Arema Communictaions And Signals 4c481d

AMERICAN RAILWAY ENGINEERING AND MAINTENANCE OF WAY ASSOCIATION COMMUNICATIONS & SIGNALS MANUAL

VOLUME 5 SECTION 18 – INSIDE PLANT SECTION 19 – ELECTRICAL PROTECTION SECTION 20 – INDUCTIVE INTERFERENCE SECTION 21 – DATA TRANSMISSION SECTION 22 – RADIO 2002 AREMA Committees Developing C&S Manual Parts AREMA Committee 36- Highway-Rail Grade Crossing Warning Systems Subcommittee 36-1 Warning System Controls Subcommittee 36-2 Warning System Installation & Maintenance Subcommittee 36-3 Warning System Equipment Subcommittee 36-4 Intelligent Transportation Systems AREMA Committee 37- Signal Systems Subcommittee 37-1 Signal Systems Subcommittee 37-2 Signal Equipment Subcommittee 37-3 Signal Control & Applications AREMA Committee 38- Information, Defect Detection & Energy Systems Subcommittee 38-1 Equipment Applications Subcommittee 38-2 Electromagnetic Compatibility Subcommittee 38-3 Energy Systems Subcommittee 38-4 Radio/Wireless

This page intentionally left blank

AMERICAN RAILWAY ENGINEERING AND MAINTENANCE OF WAY ASSOCIATION COMMUNICATIONS & SIGNALS MANUAL OF RECOMMENDED PRACTICE (2002) VOLUME 5 A recommended practice is a design, plan, instruction, information or any proposition of importance recommended in the interest of establishing uniformity, promoting safety or efficiency and economy. A recommended practice does not in any way imply or otherwise suggest inadequacy of practices that may not conform thereto. In addition, it is recognized that federal, state, provincial, or municipal laws and regulations may, where applicable, be at variance with the recommended practice. Each Manual Part will have any one of the following dates: New

- Date the Part was first approved for inclusion in the Manual.

Revised

- Year in which the Part was revised.

Reaffirmed

- Date on which the Part was reviewed and found to be technically correct. Therefore it is still a recommended practice.

Extended

- Date indicates that the Part is under review and tha t further action will be taken.

Your comments about the Communications & Signals Manual and the information it contains are most welcome. Comments and questions of interpretation or application should be addressed to Executive Director, American Railway Engineering and Maintenance of Way Association, 8201 Corporate Drive, Suite 1125, Landover, MD 20785-2230. Printed in U.S.A. COPYRIGHT  2002: ALL RIGHTS RESERVED. THIS MANUAL, OR PARTS THEREOF, MAY NOT BE REPRODUCED IN ANY FORM WITHOUT PERMISSION OF THE AMERICAN RAILWAY ENGINEERING AND MAINTENANCE OF WAY ASSOCIATION. SPECIAL NOTE: THE AREMA COMMUNICATIONS AND SIGNALS MANUAL OF RECOMMENDED PRACTICE WILL UPDATE THE LOOK OF ITS MANUAL PARTS OVER THE NEXT FIVE YEARS, STARTING IN 2002. NOT ALL MANUAL PA RTS WILL HAVE THE SAME STYLE DURING THIS PROCESS.


AREMA® C&S Manual 2002

Subject Index Subject Index for Manual Parts Revised 2002 (24 Pages)

AC relays 6.1.21, 6.1.35, 6.1.40 Instructions 6.4.5 Adapter clamp for signs 3.2.80 Adjacent track interconnected highway-rail grade crossing warning systems 3.1.11 Adjustable lock rod 12.2.15, 12.2.16 Adjustment bracket Vertical switch lock rod Bolt fastening 12.1.18 Parts 12.1.19, 12.1.20 Stud fastening 12.1.16 Vertical switch throw rod Bolt fastening 12.1.17 Parts 12.1.19, 12.1.20 Stud fastening 12.1.15 istration Section 1 Advance operating times Calculate for highway-rail grade crossing warning devices 3.3.10 Air depreciated primary battery 9.1.25 Aligning flashing-light signals 3.3.5 Alloys, non-ferrous 15.1.5 Aluminum conductors steel reinforced 10.3.11 Analog data transmission 21.1.2 Approach lighting, vital circuits 16.4.2 Arm, gate 3.2.15, 3.2.20 Gate, wood 3.2.25, 3.2.26, 3.2.30A through 3.2.30C Light unit 3.2.40 Armored signal cable 10.3.17 Arresters, lightning, see Electrical Surge Protection Aspects, flashing (not crossing signals) 2.1.5 Assembly of insulated track fittings 8.5.1 Audio frequency track circuits 8.2.1, 8.6.10 Automatic block End of sign 2.1.50B Automatic block signaling 2.2.1 Instructions 2.4.3 Automatic block signaling circuits 2.2.1 Automatic Equipment Identification (AEI) site configuration 5.3.2 Automatic speed control with continuous cab signaling 16.4.50 Ball socket screw jaw for switch circuit controller 12.1.7 Ball studs for switch circuit controller 12.1.2 Bases 7.2.35, 7.2.36A, 7.2.36B, 7.2.40, 7.2.41A, 7.2.41B, 7.2.45A, 7.2.45B, 7.2.46A, -1-

AREMA® C&S Manual Subject Index 2002 7.2.46B Batteries Air alkaline 9.1.26 Air depreciated primary 9.1.25 Applications 9.1.30 Chargers 9.2.1, 9.2.5 Disposal and recycling 9.5.5 Lead-acid storage 9.1.1, 9.1.2, 9.1.3, 9.5.3, 9.5.4 Nickel-cium 9.1.15, 9.5.2 Standby requirements for highway-rail grade crossing warning systems 3.1.28 Storage, instructions 9.5.1 Valve regulated 9.1.4, 9.1.16 Begin CTC sign 2.1.50C Begin TCS sign 2.1.50F Bell, highway-rail grade crossing warning devices 3.2.60, 3.2.61 Binding posts 14.1.10, 14.1.11, 14.1.12 Block, end of (sign) 2.1.50A Block, end of automatic (sign) 2.1.50B Blocks, terminal Molded 14.1.5, 14.1.8 Multiple unit 14.1.6 Screw clamp type 14.1.2 Short type 14.1.7 Boilerplate in Manual Parts 1.4.1, 6.5.1, 7.5.1 Bolts 14.1.1, 14.6.20 For highway-rail grade crossing signs 3.2.96A through 3.2.96C Bond compound, impedance 8.4.6 Bond, impedance 8.4.5 Fire-resistant dielectric 8.4.8 Instructions 8.6.30 Bonding, track circuit 8.1.20 Bond oil, impedance 8.4.7 Bonds, See Rail Head/Web Bonds Bond Strand 10.3.12 Brackets, extension for crossing signs 3.2.85 Breakaway gate arm adapter 3.2.21 Bridge circuit coupler 2.2.36 Cable Section 10 - See also listings under Wire Chlorosulfonated polyethylene and neoprene jacketing 10.3.20 Cross-linked polyethylene insulation and jacketing 10.3.22 Ethylene propane rubber insulation 10.3.19 Instructions 10.4.1 Low smoke halogen free 10.3.13 Polyvinyl chloride insulation and jacketing 10.3.23 Purpose & meaning of used in Manual Parts 10.3.40 -2-


Subject Index

Polyethylene insulation and jacketing 10.3.21 Signal Armored 10.3.17 Non-armored 10.3.16 Synthetic rubber insulation 10.3.18 Calculations Approach warning time for highway-rail grade crossings 3.3.10 Minimum allowable resistance between track battery and track 8.1.5 Time release applied to signal apparatus 2.4.20 Track circuit readings 8.1.10 Train shunt resistance 8.1.11 Canadian Electrical Code 11.1.5 Cantilevers for highway-rail grade crossing warning devices 3.2.5, 3.2.10 Cap for junction box base 7.2.50 Car detector 5.1.45, 5.1.47 Car retarders Distributive 4.2.13 Electric 4.2.10 Electro-hydraulic 4.2.12 Electro-Pneumatic 4.2.11 Carriers, pipe 13.1.57 Case platform 14.4.25 Castings Gray iron 15.1.1 Malleable iron 15.1.2 Cathodic protection 8.6.15 Centralized traffic control 2.2.11, 2.2.15 Charger, battery Constant current 9.2.5 Constant voltage 9.2.1 Chromaticity 7.1.10 Circuit protection Section 11 Circuits Automatic block signaling 2.2.1 Design guidelines Section 16 Nomenclature 16.1.1 Non-vital relays 6.3.1, 6.3.5 Vital circuit design guidelines Sections 16.3, 16.4, 16.5, 16.6, 16.9, 16.30 Circuits, track Section 8 Instructions 8.6.1 Minimize lightning, see Electrical Surge Protection Circuit, end of (sign) 2.1.50D Circuit coupler for movable bridge 2.2.30 Circuit controller, switch 12.1.1 Ball socket screw jaw 12.1.7 Ball studs 12.1.2 -3-

AREMA® C&S Manual Subject Index Insulated rod 12.1.6 Rods 12.1.5 Clamp, adapter for signs 3.2.80 Classification yard Computer to control 4.1.10 Control console 4.2.1 Distribute retarder 4.2.13 Inspection and test 4.3.1 Installation 4.1.1 Insulated t location 4.1.5 Signaling 4.1.15 Clean cab locomotive radio 22.2.1, 22.1.1 Clearances, overhead cable, 2.4.1 Climbing step 7.2.30 Coatings, metallic 15.3.1 Coded track circuit unit Non-resonant 8.3.1 Phase-Selective 8.4.1 Resonant 8.4.1, 8.4.2 Codes NESC, NEC, CEC 11.1.5 Color light signal, doublet lens 7.1.1 Color light signal searchlight type 7.1.14 Color light switch position indicator 7.3.1 Color position light signal 7.1.3 Colors, signal paint for signs, targets, etc. 15.3.10 Commercial communication facilities 20.1.4 Communication facilities 19.1.14, 20.1.8 Compensator Cranks 13.1.46 Link 13.1.47 Pipe 13.1.45 Component placement 11.2.2 Compound, impregnation of electrical windings 15.2.1 Compound Filling recesses & sealing 15.2.15 Insulating 15.2.3 Computer to control a classification yard 4.1.10 Concrete foundations, precast 14.4.lA through 14.4.11 Concrete pier for instrument housings 14.4.11 Condensation, minimize Instructions 1.5.5 Conduit Steel pipe 14.6.31 Cones, signal 7.1.10 Connectors -4-

2002


Subject Index

Ground rod 11.3.4, 11.4.1 Terminal 14.1.15 Track circuit 8.1.25 Consoles, classification yard 4.2.1 Constant current battery charger 9.2.5 Constant voltage battery charger 9.2.1 Constant warning time device for highway-rail grade crossing warning systems 3.1.26 Control of highway-rail grade crossing warning devices 3.1.15 Constant warning time devices 3.1.26 Controllers 3.1.25 Motion sensors 3.1.20 Controller, switch circuit 12.1.1 Ball socket screw jaw 12.1.7 Ball studs 12.1.2 Insulated rod 12.1.6 Rods 12.1.5 Cotters 14.6.22 Coupling, 1 in. pipe 13.1.6 Crank 13.1.38 Pins 13.1.50 Pipe compensator 13.1.46 Crank stand 13.1.35, 13.1.36 Crossarm for flashing-light signal 3.2.50, 3.2.51 Crossbuck sign 3.2.70, 3.2.71, 3.2.90 Cross-linked polyethylene insulation & jacketing for wire & cable 10.3.22 Crossovers, fouling protection 2.1.15 Current, foreign Minimize on dc track circuit 8.6.15 CTC, Begin (sign), End (sign) 2.1.50C DC relays 6.1.1, 6.1.2, 6.1.5, 6.1.10, 6.1.15, 6.1.20, 6.1.21, 6.1.25, 6.1.30, 6.1.45, 6.2.1, 6.3.1, 6.3.5 Instructions 6.4.1 DC track circuit Minimize foreign current 8.6.15 Test record 8.1.10 Decoding transformer 8.3.10 Decoding unit 8.3.5 Definitions and Definitions for technical in signaling 1.1.1 Wire and cable 10.3.40 Surge protection 11.3.10 Design guidelines - vital circuits Section 16 Designation plate, relay post 6.1.50 Detectors Car 5.1.45 -5-

AREMA® C&S Manual Subject Index Dragging equipment 5.1.1, 2.4.1 Falling rock 2.4.1, 5.1.12 Flat wheel 5.1.25 High, wide load 5.1.20 Hot bearing 5.1.30 Hot wheel 5.1.35 Inspection and testing 5.3.6 Rock slide 2.4.1, 5.1.12, Wheel 5.1.50 Wheel crack 5.1.40 Dielectric requirements for signal equipment 11.5.1 Dielectric, impedance bond fire-resistant 8.4.8 Discs Signal 7.1.10 Distribute retarder 4.2.13 Dragging equipment detector 5.1.1 Drill rail bond holes, instructions 8.6.25

2002

Electric car retarders 4.2.10 Electric lamps, incandescent 14.2.1, 14.7.1 Electric light unit Flashing-light signals 3.2.35 Gate arm 3.2.40, 3.2.45 Indicators & signs 7.3.6 Electric locks 2.1.25 Electric locking Instructions for testing 2.4.5 Electric motor switch operating mechanism 12.2.1 Electric switch locks 12.4.5 Electrical crossings 20.1.1 Electrical protection Section 11 Electrical safety 11.1.1 Electrical supply facilities 20.1.4 Electrical supply lines 20.1.1 Electrical surge protection, 11.2.1, 11.3.1, 11.3.2, 11.3.3, 11.3.4, 11.3.10, 11.4.1, 11.4.2, 19.1.10 Electrical windings Insulating compound 15.2.1 Varnish 15.2.2 Electronic track circuits 8.1.2 Electro-pneumatic car retarder 4.2.11 Electrostatic discharge control program 19.1.20 End of automatic block sign 2.1.50B End of block sign 2.1.50A End of CTC sign 2.1.50C End of circuit sign 2.1.50D -6-

AREMA® C&S Manual 2002 Subject Index End TCS sign 2.1.50F End of train device (TIS) 22.3.1 Environmental criteria, electrical and electronic signal equipment 11.5.1 Equipment, solid state Installation, maintenance and test 1.5.1 Extension bracket for crossing signs 3.2.85 Exothermic welded bonds 8.1.32, 8.1.33, 8.1.34 Facility, t signal agreement 1.3.1 Falling rock detector 5.1.12 Faraday shielding 11.3.10, 11.4.2 Fire-resistant dielectric, impedance bond 8.4.8 Flasher DC relay 6.1.45 Rate for crossing signal 3.1.1 Solid state for crossing signals 3.2.55 Flashing aspects (not crossing signals) 2.1.5 Flashing-light signal Alignment 3.3.5 Application 3.1.5 Cantilever mounting 3.2.5, 3.2.10 Crossarm 3.2.50, 3.2.51 Electric light unit 3.2.35 Flat wheel detector 5.1.25 FM transeiver (radio) 22.2.3 Foreign current, minimize on dc track circuit 8.6.15 Fouling protection on turnouts & crossovers 2.1.15 Foundations, galvanized steel 14.4.17, 14.4.19, 14.4.21, 14.4.21A. 14.4.23 Foundations, pour-in-place 14.4.30, 14.4.31, 14.4.32, 14.4.33, 14.4.34, 14.4.35, 14.4.36 Foundations, precast concrete 14.4.lA, 14.4.8A through 14.4.11 Foundations, ladders 7.2.55 Frequencies, radio, allocated 22.1.2 Frequencies, radio, channels 22.1.1 Friction tape 14.6.35 Frost conditions, instructions to minimize 1.5.5 Gasket material 15.2.10 Gate (highway-rail grade crossing) Application 3.1.5 Arm 3.2.20 Four quadrant (exit) 3.1.5, 3.2.15 Light unit for arm 3.2.40 Limited clearance combination 3.2.10 Operating mechanism 3.2.15 Wind 3.2.22 -7-

AREMA® C&S Manual Subject Index With flashing-light signal 3.2.12 Wood arm 3.2.25, 3.2.26, 3.2.30A through 3.2.30C Gate arm (breakaway) adapter 3.2.21 Gauge, switch obstruction 12.4.10 Grade crossings - see Highway-Rail Grade Crossing Warning System Grade signal marker 2.1.41 Graphical symbols 16.2.l through 16.2.l9 Gray iron castings 15.1.1 Grease, pressure gun Identical Criteria 15.5.1 Lime soap base 15.4.6 Lithium soap base 15.4.5 Ground rods (electrodes) Copper clad 11.3.4 Chemically enhanced 11.3.5 Made ground 11.4.1 Grounds Communication facilities 19.1.14 Installation, see Electrical Surge Protection Instructions 11.4.2 Hand-operated switches 2.1.25 Highway-rail grade crossing warning systems Sec. 3 Adjacent track 3.1.11 Aligning flashing-light signals 3.3.5 Application guidelines 3.1.5 Audio frequency track circuit 8.2.1, 8.6.10 Battery requirements 3.1.28 Bell 3.2.60, 3.2.61 Bolts for signs 3.2.96A through 3.2.96C Breakaway gatearm 3.2.21 Calculating advance operating times 3.3.10 Cantilever combinations 3.2.10 Location Plan 3.1.35 Mounting of flashing light signals 3.2.2, 3.2.5 Circuits: design guidelines, Manual Part Section 16 Clamp for signs 3.2.80 Complete assembly, gate, flashers, cantilever span 3.2.2 Constant warning time control 3.1.26, 3.3.20 Control 3.1.15 Controllers 3.1.25 Crossarm for flashing-light signals 3.2.50, 3.2.51 Extension bracket for signs 3.2.85 Flashing-light signal applications 3.1.5 Flashing-light signal assembly drawings 3.2.2 -8-

2002


Subject Index

Flashing light rate 3.1.1 Gate arm Break away 3.2.21 Four quadrant (exit) 3.1.5, 3.2.15 Self restoring 3.2.23 Tubular/telescopic 3.2.20, 3.2.24 Wood 3.2.25, 3.2.26 Wood anticulated 3.2.30A, 3.2.30B, 3.2.30C Gate mechanism 3.1.5, 3.2.10, 3.2.15 Inspection and test 3.3.30 Installation center turn lane 3.1.37 Insulated t locations 3.1.30 Interconnected 3.1.11 Interconnection with highway traffic signals 3.1.10 Interrupt 3.1.10 Light for gate arm 3.2.40 Light unit for flashing-light signal Incandescent 3.2.35 Light emitting diodes 3.2.35 Location plans 3.1.35, 3.1.36, 3.1.36A through 3.1.36L Locomotive, clean cab radio 22.2.1 Maintenance, testing, inspection and instructions 2.4.1, 3.3.1 Mast (See cantilever) Monitoring 3.1.29, 3.1.29A Motion sensor control 3.1.20, 3.3.15 Preemption 3.1.10 Signs 3.2.65, 3.2.70, 3.2.71, 3.2.75, 3.2.90 Solid-state flasher 3.2.55 Standby battery requirements 3.1.28 Symbols, graphical 3.1.31 Warning devices operating guidelines 3.1.1 Warning devices functional guidelines 3.1.36 Warning time, determining 3.3.10 High, wide load detector 5.1.20 Horizontal crank stand 13.1.35, 13.1.39 Hot bearing detector 5.1.30 Site selection 5.3.1 Hot wheel detector 5.1.35 Identical items ("Boilerplate") for all Manual Parts 1.4.1 Illuminated indicators and signs 7.3.5, 7.3.7, 7.3.8 Electric light unit 7.3.6 Roundels 7.3.9 Impedance bond 8.4.5 Compound 8.4.6 Fire-resistant dielectric 8.4.8 -9-

AREMA® C&S Manual Subject Index Instructions 8.6.30 Oil 8.4.7 Impulse transformer 14.2.25 Incandescent electric lamps 14.2.1, 14.7.1 Indicator Electric light unit 7.3.6 Illuminated 7.3.5, 7.3.7, 7.3.8 Switch position 7.3.1 Take or leave siding 2.1.45 Inductive Coordination 20.1.4, 20.1.6, 20.1.7 Inductive Effects 20.1.8 Inspection and test Classification yards 4.3.1 Defect detectors 5.3.6 Highway-rail grade crossing warning systems 3.3.30 Signal Systems 2.4.1 Installation AC relays 6.4.5 Communication facilities 19.1.14 Computer control of a classification yard 4.1.10 DC relays 6.4.1 Drill rail holes for plug bonds 8.6.25 Highway-rail grade crossing warning systems 3.3.30 Impedance bonds 8.6.30 Insulated rail ts 8.6.35 Incandescent electric lamps 14.7.1 Interlockings 2.4.10 Lead-Acid Storage Batteries 18.1.36 Light signals 7.4.1 Made grounds 11.4.1 Minimize foreign current in dc track circuits 8.6.15 Movable bridge signals 2.4.15 Rail head/web bonds 8.6.25, 8.6.40 Solid state equipment 1.5.1 Storage batteries 9.5.1 Time releases 2.4.20 Track circuits 8.6.1 Wire and cable 10.4.1, 10.4.40 Yard systems 4.1.1 Instructions AC relays 6.4.5 Aligning flashing-light signals 3.3.5 Audio frequency track circuits 8.6.10 Automatic block signaling 2.4.3 Batteries 9.5.1, 9.5.2, 9.5.3, 9.5.4, 9.5.5 Cable 10.4.1 -10-

2002


Subject Index Calculating advance operating times for highway-rail grade crossing warning systems 3.3.10 Classification yards 4.3.1 Constant warning time devices 3.3.20 DC relays 6.4.1 Defect detectors 5.3.6 Drill rail bond holes for plug bonds 8.6.25 Electric locking 2.4.5 Electric switch locks 12.5.5, 2.4.1 Facing point locks 12.5.15 Highway-rail grade crossing warning systems 3.3.1, 3.3.30 Hot bearing detector site selection 5.3.1 Impedance bonds 8.6.30 Incandescent electric lamps 14.7.1 Insulated rail ts 8.6.35 Insulation resistance testing 10.4.30 Interlockings 2.4.10, 2.4.1 Light signals 7.4.1, 2.4.1 LP gas winter switch protection devices 12.5.20 Made grounds 11.4.1 Minimize foreign current in dc track circuits 8.6.15 Minimize frost and condensation 1.5.5 Motion sensors 3.3.15 Movable bridge signals 2.4.15 Oil burning winter switch protection devices 12.5.21 Painting 1.5.10 Rail head/web bonds 8.6.25, 8.6.40 Signal installations 2.4.1 Solid state equipment 1.5.1 Spring switches 12.5.10, 12.5.15, 2.4.1 Storage batteries 9.5.1, 9.5.2, 9.5.3, 9.5.4, 9.5.5 Switches, derails 2.4.1 Switch circuit controller 12.5.1, 2.4.1 Time releases 2.4.20 Track circuits 3.3.25, 8.6.1, 2.4.1 Wire 10.4.1, 10.4.40 Insulated t location 2.1.20A, 2.1.20B, 2.1.20C, 2.1.20D Fouling protection 2.1.15 Grade crossing 2.1.20E Island circuit 3.1.30 Insulated rail ts At highway-rail grade crossings 3.1.30 Car retarder locations 4.1.5 Instructions 8.6.35 Locations 2.1.20A through 2.1.20E Insulated signal wire 10.3.15 -11-

AREMA® C&S Manual Subject Index Insulated terminals 14.1.15 Insulated track fittings 8.5.1, 8.5.2, 8.5.3 Insulating compound Filling recesses 15.2.3 Impregnation of electrical windings 15.2.1 Insulation Cross-linked polyethylene for wire & cable 10.3.22 Ethylene propane rubber for wire & cable 10.3.19 Polyethylene for wire and cable 10.3.21 Polyvinyl chloride for wire and cable 10.3.23 Synthetic rubber for wire and cable 10.3.18 Insulation, pipe line, 1 in. 13.1.25 Insulation resistance testing 10.4.30 Interlocking 2.2.10, 2.2.11 Microprocessor 2.2.12 Movable bridge 2.4.10 Interlockings Traffic control 2.2.2 Microprocessor based 2.2.12 Iron castings Gray iron 15.1.1 Malleable 15.1.2 Isolation of power supplies 16.3.2

2002

Jacketing Cross-linked polyethylene for wire and cable 10.3.22 Neoprene and chlorosulfonated polyethylene for wire and cable 10.3.20 Polyethylene for wire and cable 10.3.21 Polyvinyl chloride for wire and cable 10.3.23 Jaws Ends, tang and plain 13.1.21 Links 13.1.21 Pins 13.1.50 Screw ball socket for switch circuit controller 12.1.7 Screw with tang end 13.1.30, 13.1.15 Solid with tang ends 13.1.20, 13.1.15 ts, rail insulated, instructions 8.6.35 ts, rail insulated, location 2.1.20A through 2.1.20E Car retarder location 4.1.5 At highway-rail crossings, railroad crossings 3.1.30 t signal facility agreement 1.3.1 Junction box base for signals 7.2.36A, 7.2.36B, 7.2.41A, 7.2.41B, 7.2.46A, 7.2.46B, 7.2.50 Ladder foundations 7.2.55 Lamps, electric incandescent 14.2.1, 14.7.1 -12-

AREMA® C&S Manual 2002 Lamps, semaphore, lens hood 7.1.30 Lamps, switch, lens hood 7.1.30 Lead-acid storage batteries 9.1.1, 9.1.2, 9.1.3, 18.1.36 Leave siding indicator 2.1.45 Lens hoods for switch and semaphore lamps 7.1.30 Lens Doublet 7.1.1 Lenses, signals 7.1.10 Letters and numerals 14.6.2A, 14.6.3 Light, electric Gate arm 3.2.40 Highway-rail grade crossing warning signals 3.2.35 Indicators and signs 7.3.6 Light emitting diode (LED) 3.2.35 Light out detection, vital circuit design guidelines 16.4.30 Light signals, See Section 7 Application of light units to mast 7.2.1 Chromaticity 7.1.10 Color light 7.1.1 Color position light 7.1.3 Electronic Control 2.1.10 Fixed 2.1.1 Flashing Aspect 2.1.5 Identical items 7.5.1 Instruction 7.4.1 Position light 7.1.2 Search light 7.1.4 Lightning Arresters, see Electrical Surge Protection Lime soap base, pressure gun grease 15.4.6 Line circuit reactor 14.2.20 Line circuits, double feed 16.5.1 Line circuits TCS 16.50.2 Line wire 10.3.10 Lithium soap base, pressure gun grease 15.4.5 Lock, electric 2.1.25 Lock rod, adjustable 12.2.15, 12.2.16 Locking, electric, instructions for testing 2.4.5 Locking, time, vital circuits 16.4.1 Locks, switch, electric 12.4.5 Loss of shunt, circuits 16.4.8 LP gas winter switch protection devices 12.5.20 Lubricant, electro-pneumatic valves and cylinders 15.4.10 Lubrication oil 15.4.1 Lug Point 12.1.10, 12.1.11 Tang end 13.1.47 -13-

Subject Index

AREMA® C&S Manual Subject Index

2002

Maintain light signals 7.4.1 Maintenance AC relays 6.4.5 Automatic block signaling 2.4.3 Communication facilities 19.1.14 DC relays 6.4.1 Electric switch locks 12.5.5 Highway-rail grade crossing warning systems 3.3.1 Impedance bonds 8.6.30 Incandescent electric lamps 14.7.1 Insulated rail ts 8.6.35 Interlockings 2.4.10 Lead-Acid Storage Batteries 18.1.36 Light signals 7.4.1 LP gas winter switch protection devices 12.5.20 Made grounds 11.4.1 Minimizing foreign current in dc track circuits 8.6.15 Movable bridge signals 2.4.15 Oil burning winter switch protection devices 12.5.21 Rail head/web bonds 8.6.25, 8.6.40 Solid state equipment 5.3.5 Spring switches 12.5.10, 12.5.15 Storage batteries 9.5.1 Switch circuit controller 12.5.1 Time releases 2.4.20 Track circuits 8.6.1 Wire and cable 10.4.40 Malleable iron castings 15.1.2 Manual Parts "Boilerplate", identical sections 1.4.1 Marker Grade signal 2.1.41 Spring switch 12.3.15 Masts Base and Junction Boxes 7.2.35 - 7.2.50 Light signals 7.2.1 Signals 7.2.20 Materials Section 15 Insulating filling recesses 15.2.3 Gasket 15.2.10 Retroreflective sheet 15.2.20 Mechanical Section 13 Metallic coatings 15.3.1 Metals, non-ferrous 15.1.5 Microprocessor interlocking 2.2.12 -14-


Subject Index

Quality assurance software based equipment 17.1.1 Molded terminal blocks 14.1.5 Motion sensors 3.1.20 Motor, electric (switch mechanism) 12.2.1 Movable bridge Circuit coupler 2.2.30 Instructions 2.4.15 National Electrical Code 11.1.5 National Electrical Safety Code 11.1.5 Nickel-cium storage battery 9.1.15 Nomemclature 16.1.1 Non-armored signal cable 10.3.16 Non-ferrous metals & alloys 15.1.5 Non-resonant coded track circuit unit 8.3.1 Number of tracks sign 3.2.75 Numerals and letters 14.6.2B, 14.6.3 Nuts 14.1.11, 14.6.20 Nuts Insulated 14.1.15 Obstruction gage, switch 12.4.10 Oil Identical criteria 15.5.1 Impedance bond 8.4.7 Lubricating 15.4.1 Spring switch 12.3.10 Oil burning winter switch protection devices 12.5.21 Outlet for junction box base for signals 7.2.50 Overlay track circuit 3.1.23, 3.1.26 Paint: colors for signs, switch targets, etc. 15.3.10 Painting instructions 1.5.10 Phase-selective coded track circuit 8.4.1 Pier, concrete for instrument housings 14.4.11 Pinnacles for masts 7.2.60 Pins, crank, jaw 13.1.50 Pipe Adjusting screws 13.1.10 Carriers 13.1.57 Compensator 13.1.45 Steel Conduit 14.6.31 Welded steel 1 in. 13.1.5, 13.1.6 Pipe-line insulation 1 in. pipe 13.1.25 Plain washers 14.6.21 Plate, relay post designation 6.1.50 Plug boards for plug-in relays 6.2.2 -15-

AREMA® C&S Manual Subject Index Plug-in dc relay 6.2.1, 6.3.1 Point lug 12.1.10, 12.1.11 Portable radio for remote control of engine 22.2.2 Position light signal 7.1.2 Posts Binding 14.1.10, 14.1.11, 14.1.12 Power operated switch mechanism Electric 4.2.5, 12.2.1 Electro-hydraulic 4.2.5 Electro-pneumatic 4.2.5, 12.2.10 Test requirements 12.2.5 Power supplies used in vital signal systems, isolation 16.3.2 Power supply Section 9 Battery applications 9.1.30 Solar 9.4.1, 9.4.2 Standby battery for highway-rail grade crossing warning systems 3.1.28 Precast concrete foundations 14.4.lA through 14.4.11 Pre-emption of highway traffic signals 3.1.10 Preliminary section sign 2.1.50E Pressure gun grease Lime soap base 15.4.6 Lithium soap base 15.4.5 Primary battery, air depreciated 9.1.25 Protection cathodic 8.6.15 Protection, electrical Section 11

2002

Quality Assurance and Principles - software based equipment and systems Section 17 Radio equipment 22.2.1, 22.2.2, 22.2.3 Radio frequencies 22.1.1, 22.1.2 Radio frequency requirements for train information systems 22.3.1 Rail head/web bonds Application-instructions 8.6.40 Design Criteria 8.1.20, 8.1.31, 8.1.34 Drilling 3/8-inch web 8.6.25 Plug-type rail web 8.1.25 Welded type 8.1.30 Rail ts, insulated, instructions 8.6.35 Railway signal systems Section 2 Reactor for line & track circuits 14.2.20 Relays Section 6 AC induction 6.1.35 AC instructions 6.4.5 AC power transfer 6.1.40 post designation 6.1.50 DC biased neutral 6.1.5 -16-


Subject Index

DC code following 6.1.30 DC code transmitter 6.1.25 DC flasher 6.1.45 DC instructions 6.4.1 DC neutral 6.1.1, 6.1.2 DC neutral for non-vital circuits 6.3.1, 6.3.5 DC neutral, plug-in type 6.2.1 DC polarized 6.1.10 Identical items 6.5.1 Plugboard for plug-in relays 6.2.2 Retained neutral polarized 6.1.15 Time element 6.1.20, 6.1.21 Relay based systems, vital circuit design guidelines 16.3.1 Relay interlocking 16.5.1 Remote control of engine by portable radio 22.2.2 Resistance Insulation testing 10.4.30 Track and battery circuit calculations 8.1.5 Train shunt test record 8.1.10 Resistor 14.2.15 Resonant coded track circuit unit 8.4.1 Resonant two element tuned unit 8.4.2 Retarder Distributive 4.2.13 Electric 4.2.10 Electro-hydraulic 4.2.12 Electro-pneumatic 4.2.11 Retarder yard Installation 4.1.1 Insulated t location 4.1.5 Retroreflective sheet material 15.2.20 Rock slide detector 5.1.12 Rods Double tang ends 13.1.31 Ground 11.3.4, 11.4.1 Lock 12.2.15, 12.2.16 Switch circuit controller 12.1.5, 12.1.6 Roundels, signal 7.1.10, 7.1.11 Illuminated indicators and signs 7.3.9 Route checks, vital circuits 16.4.4 Route locking, vital circuit design guidelines 16.4.2 Rubber Ethylene propane insulation for wire & cable 10.3.19 Insulating tape 14.6.36 Synthetic insulation for wire & cable 10.3.18 -17-

AREMA® C&S Manual Subject Index

2002

Safety codes: NESC, NEC, CEC 11.1.5 Safety, electrical 11.1.1 Screw clamp terminal blocks 14.1.2 Screw and solid jaws 13.1.15 Screws, pipe adjusting 13.1.10 Sealing compound 15.2.15 Searchlight signal 7.1.4 Section, preliminary (sign) 2.1.50E Semaphore lamps, lens hoods 7.1.30 Shunt resistance test procedures 8.1.11 Siding, take or leave indicator 2.1.45 Signal Apparatus, time releases 2.4.20 Application of light units to masts 7.2.1 Cable- armored 10.3.17; non-armored 10.3.16 Color light 7.1.1 Color position light 7.1.3 Colors (excluding signal glass) 15.3.10 Dielectric requirements 11.5.1 Electronic control 2.1.10 Enclosure layout 11.2.2 Environmental Requirements 11.5.1 Facility, t agreement 1.3.1 Fixed 2.1.1 Flashing Aspect 2.1.5 Grade marker 2.1.41 Identical items 7.5.1 Ladders 7.2.25 Roundels 7.1.11 Roundels, lenses, discs & cones 7.1.10 Masts (See Highway-Rail Grade Crossing Warning Systems-Cantilever) Position light 7.1.2 Searchlight 7.1.4 Searchlight, stuck mechanism 16.4.10, 16.5.10 Railroad systems Section 2 Units 1.3.2 Wiring strategies for surge damage 11.2.2 Signaling Automatic block 2.2.1, 2.2.11 Automatic block circuits 2.2.3 Inspection and test 2.4.1 Instructions, movable bridge 2.4.15 Technical 1.1.1 Yards, classification 4.1.15 Signs -18-


Subject Index

Adapter clamp 3.2.80 Begin CTC, end CTC 2.1.50C Begin TCS, end TCS 2.1.50F Bolts for highway-rail grade crossing warning devices 3.2.96A through 3.2.96C Electric light unit 7.3.6 End of automatic block 2.1.50B End of block 2.1.50A End of circuit 2.1.50D Extension brackets 3.2.85 Highway-rail grade crossing warning devices 3.2.65, 3.2.70, 3.2.71 Illuminated 7.3.5, 7.3.7, 7.3.8 Mounting 3.2.90 Number of tracks 3.2.75 Preliminary section 2.1.50E Other than highway-rail grade crossings 14.6.1 Roundels 7.3.9 Site selection, hot bearing detector 5.3.1 Snow melters (see Winter Switch Protection Devices) Software base equipment and systems quality assurance 17.1.1 Solar power systems 9.4.1, 9.4.2 Solderless wire terminals 14.1.1 Solid jaws with tang ends 13.1.20 Solid state Equipment, installation, maintenance and test 5.3.5 Flasher 3.2.55 Speed control with continuous cab signaling, automatic 16.4.50 Spring lock washers 14.6.21 Spring switch 12.3.5 Facing point lock 12.5.15 Marker 12.3.15 Oil 12.3.10 Vital circuits 16.6.4 Stand, crank 13.1.35, 13.1.36 Steel 15.1.4 Steel pipe conduit 14.6.31 Steel wire strand, zinc coated 10.3.25 Step, climbing 7.2.30 Storage batteries - instructions 9.5.1 Lead-acid 9.1.1, 9.1.2, 9.1.3 Nickel cium 9.1.15 Stuck mechanism-detection vital circuit design guidelines Automatic signals 16.5.10 Controlled signals 16.4.10 Studs, ball for switch circuit controller 12.1.2 Surge damage prevention 11.2.2 Surge protection, see Electrical surge protection -19-

AREMA® C&S Manual Subject Index 2002 Switch Hand-operated 2.1.25 Heaters (see Winter switch protection devices) Lamp, lens hoods 7.1.30 Locks, electric 12.4.5 Lock rod adjustment bracket Parts 2.1.19, 12.1.20 Vertical 12.1.16, 12.1.18 Mechanism Electric motor, lockable 12.2.1 Electro-pneumatic, lockable 12.2.10 Test requirements for power operation 12.2.5 Obstruction gage 12.4.10 Position indicator 7.3.1 Self-restoring 16.6.3A, 16.6.3B, 16.6.3C Spring 12.3.5 Marker 12.3.15 Oil 12.3.10 Protection 2.2.5 Vital circuits 16.6.4 Throw rod adjustment bracket Parts 12.1.19, 12.1.20 Vertical 12.1.15, 12.1.17 Winter switch protection devices 12.5.20, 12.5.21, 12.5.23, 12.6.1, 12.6.10 Switch circuit controller 12.1.1 Ball socket screw jaw 12.1.7 Ball studs 12.1.2 Insulated rod 12.1.6 Rods 12.1.5 Switches Section 12 Yard 4.2.5, 4.1.25 Symbols, graphical Highway-rail grade crossings 3.1.31 Signal circuits 16.1.1, 16.2.1 through 16.2.19 Take siding indicator 2.1.45 Tang end Double 13.1.31 Lug 13.1.47 With screw jaws 13.1.30 Tape Friction 15.2.35 Polyvinyl chloride (PVC) 15.2.37 TCS, Begin sign 2.1.50E, End sign 2.1.50F Telephone transmission 21.1.1 Terminal blocks -20-


Subject Index

Arrester 14.1.9 Molded 14.1.5, 14.1.8 Multiple unit 14.1.6 Screw clamp 14.1.2 Short type 14.1.7 Terminal connectors 14.1.15 Insulated 14.1.15 Terminals, wire, solderless 14.1.1 Terminology used in Railway signaling 1.1.1 Surge Protection 11.3.10 Wire and cable 10.3.40 Test AC relays 6.4.5 Automatic block signaling 2.4.3, 2.4.1 Classification yard 2.4.1 DC relays 6.4.1 Detectors 2.4.1 Electric locking 2.4.5, 2.4.1 Electric switch locks 12.5.5 Facing point locks 12.5.15 Highway-rail grade crossing warning systems 3.3.1, 2.4.1 Impedance bonds 8.6.30 Incandescent electric lamps 14.7.1 Insulated rail ts 8.6.35 Insulated track fittings 8.5.1, 8.5.2, 8.5.3 Insulation resistance 10.4.30 Interlockings 2.4.10, 2.4.1 Light signals 7.4.1, 2.4.1 Load requirements for power operated switch mechanism 12.2.5 LP gas winter switch protection device 12.5.20 Made grounds 11.4.1 Minimize foreign current in dc track circuits 8.6.15 Movable bridge signals 2.4.15 Oil burning winter switch protection device 12.5.21 Record DC track circuit 8.1.10 Train shunt resistance 8.1.11 Signal installations 2.4.1 Solid state equipment 5.3.5 Spring switches 2.4.1, 12.5.10, 12.5.15 Switches, derail 2.4.1 Switch circuit controller 2.4.1, 12.5.1 Time releases 2.4.20 Track circuits 2.4.1, 8.6.1 Wheel to rail resistance 8.1.11 -21-

AREMA® C&S Manual Subject Index Wire and cable 10.4.40 Threads 14.6.20 Time, calculating approach warning time for highway grade crossing warning devices 3.3.10 Time element relays 6.1.20, 6.1.21 Time releases, instructions 2.4.20 Time locking, vital circuits design guidelines 16.4.1 Track circuits Section 6, 8.6.1 Audio frequency 8.2.1, 8.6.10 Automatic block 2.2.1 Bonding 8.1.20 Calculations voltage current resistance 8.1.5 Connectors 8.1.25, 8.1.26, 8.1.27 Decoding transformer 8.3.10 Decoding unit 8.3.5 Design guidelines Section 16 DC test record 8.1.10 Electronic 8.1.2 Instructions 8.6.1 Minimize foreign current in dc circuits 8.6.15 Minimize lightning, see Electrical Surge Protection Non-Resonant coded unit 8.3.1 Overlay 3.1.23, 3.1.26 Phase selective 8.4.1 Reactor 14.2.20 Resonant coded unit 8.4.1 Tracks, number of, sign 3.2.75, 3.2.76 Traffic control systems 2.2.11, 2.2.15 Train information system 22.3.1 Train shunt resistance test record 8.1.11 Transformer 14.2.10 Decoding 8.3.10 Impulse 14.2.25 Turnouts, fouling protection 2.1.15 Units, Table of signals, interlocking and interpretation 1.3.2 Varnish for electrical windings 15.2.2 Vital circuit design guidelines Section 16 Approach lighting controlled signal 16.4.2 Double feed line circuits 16.5.1 Light out detection color light signals 16.4.30 Line Circuits in TCS 16.50.2 Loss of shunt 16.4.8 Relay based systems 16.3.1 Relay based typical interlocking 16.50.1 -22-

2002


Subject Index

Route checks 16.4.4 Route locking 16.4.2 Self restoring switch 16.6.3A, 16.6.3B, 16.6.3C Spring switches 16.6.4 Stuck mechanism detection 16.4.10, 16.5.10 Time lockings 16.4.1 Vital signal systems, isolation of power supplies 16.3.2 Voice channels 21.1.2 Washers 14.1.11 Cast iron 14.6.27 Plain 14.6.21 Spring lock 14.6.21 Web bonds - See Rail Head/Web Bonds Welded steel pipe, 1 in. 13.1.5, 13.1.6 Wheel detector 5.1.50 Crack 5.1.40 Flat 5.1.25 Wheel to rail resistance calculations 8.1.11 Wide load detector 5.1.20 Winding, electrical Insulating compound 15.2.1 Varnish 15.2.2 Winter switch protection devices 12.6.10 Safety instructions Electric 12.5.23 LP gas 12.5.20 Natural gas 12.5.22 Oil burning 12.5.21 Selection 12.6.1 Wire and cable (See Section 10) Aluminum conductor steel reinforced 10.3.11 Cross-linked polyethylene insulation and jacketing 10.3.22 Ethylene propane rubber insulation 10.3.19 Ethylene tetraflouroethylene copolymer insulation 10.3.14, 10.3.24 High Temperature 10.3.14 Instructions 10.4.1 Insulated signal wire 10.3.15 Line 10.3.10 Low smoke halogen 10.3.13 Neoprene and chlorosulfonated polyethylene jacketing 10.3.19 Polyethylene insulation and jacketing 10.3.21 Polyvinyl chloride insulation and jacketing 10.3.23 Purpose & meaning of used in recommendations 10.3.40 Synthetic rubber insulation 10.3.18 Terminals -23-

AREMA® C&S Manual Subject Index Screw clamp type 14.1.2 Solderless 14.1.1 Zinc coated steel strand 10.3.25 Wiring instructions 10.4.1 Wiring strategies for surge damage prevention 11.2.2 Yards Section 4 Computer control 4.1.10 Control consoles 4.2.1 Inspection and test 4.3.1 Installation 4.1.1 Retarders 4.2.10, 4.2.11, 4.2.12, 4.2.13 Signaling 4.1.15 Switches 4.1.25, 4.2.5 Zinc coated steel wire strand 10.3.25

-24-

2002


Section 18 – Inside Plant 18.1 - Installation and Maintenance 2002


AREMA® C&S Manual 2002 (Includes 2002 Revisions) Volume 5

Index

SECTION 18 - INSIDE PLANT Part

C

Type & Subject

18.1.36

35-3

Recommended Instructions for Installation and Maintenance of Stationary Lead-Acid Storage Batteries

Pages

11

Status

Reaffirmed 2002

______________________________________________________________ -1Note: C =

Committee responsible for Manual Part.


AREMA® C&S Manual

2002

Part 18.1.36

Recommended Instructions for Installation and Maintenance of Stationary Lead-Acid Storage Batteries Reaffirmed 2002 (11 Pages) A.

Purpose

These recommended instructions apply to the installation, maintenance and test of stationary lead-acid storage batteries. They set forth general requirements representing recommended practice. B.

Safety 1.

Keep open flames and spark-producing sources away from storage batteries. During the charging period oxygen and hydrogen gas is produced. Hydrogen may be entrapped in the battery. A flame or spark can cause an explosion. Some batteries may be equipped with flame arresters to reduce this hazard.

2.

Shut off and disconnect both the input and the output of the charging equipment before making any repairs. The possibility of damage to the equipment and electrical shock to the individual will be reduced.

3.

Never lay metal tools or material on top of a battery. Sparking or short circuits may occur.

4.

Wear protective clothing and goggles when handling, checking filling, charging, or repairing batteries for protection against spillage of electrolyte. Sulfuric acid can cause painful burns.

5.

Have water available in case electrolyte is splashed on skin or eyes. Volumes of water applied quickly and continuously can prevent serious injury and possibly avert permanent eye damage.

6.

Apply a neutralizing solution to acid spills on floors. Alkali will neutralize acid and make it safe to clean. A mixture of one pound of baking soda to one gallon of water is recommended.

7.

When mixing electrolyte, always add acid carefully to water and stir constantly. If water is added to acid, a violent reaction can occur and splash the handler.

8.

Make sure all battery connections are tight. cause sparks.

Loose connections may

________________________________________________________________ -1–

Part 18.1.36 9.

C.

D.

E.

AREMA® C&S Manual

2002

Remove all metal jewelry such as rings, watches, and bracelets before working with batteries or power leads, to remove the possibility of injury to the individual.

Receiving 1.

Lead-acid storage cells are ordinarily shipped assembled and charged. Electrolyte may be in the cells or it may be shipped separately. As soon as the battery is received, check the packing material for damage. If there is evidence of damage or spillage of electrolyte, make a notation on the bill of lading before g.

2.

Remove packing material carefully. Always lift cells by the container, never by the cell posts. A lifting sling and spreader block may be provided by the battery manufacturer.

3.

Check the electrolyte in each cell. If the level is more than 1/2 in. below the top of the plates order a new cell and file a claim against the carrier. If the electrolyte is low but higher than 1/2 in. below the top of the plates, add electrolyte of appropriate specific gravity.

Storage 1.

Batteries should be stored in an area that is weatherproof and preferably cool and dry. Do not allow electrolyte to freeze. See Table 18136-1.

2.

Charged and wet batteries must be placed in service within three months if lead-antimony or six months if lead-calcium, from the date of shipment from the factory. If extended storage is required monitor battery at monthly intervals. The battery should be given an equalizing charge every three months or when the specific gravity drops 0.025 from nominal.

3.

Charged and dry batteries should be stored no longer than twelve months from date of shipment. If extended storage is required the supplier representative for instruction. Do not remove vent seals until cells are to be filled with electrolyte.

Installation 1.

Lead-acid storage batteries should be installed in a clean, dry, and wellventilated area so that no cells are affected by radiant heat from the sun, radiators, heaters, or pipes. Temperature variations of more than 5°F (-15°C) can cause cells to become unequal. Good ventilation is required to dispose of gas generated by the battery.

________________________________________________________________ -2–

AREMA® C&S Manual

2002

Part 18.1.36

2.

ing racks should be arranged so that each cell will be accessible for adding water, cleaning, etc. Most battery manufacturers will supply recommended racks and assembly details. The racks and all associated metal parts should be painted with two or more coats of acid resistant paint.

3.

Arrange the cells, starting at the center of the bottom row, so that the positive terminal of each cell connects to the negative terminal of the next cell. The positive lead of the charger will connect to the positive terminal of the battery and the negative lead of the charger will connect to the negative terminal of the battery. Number cells starting from the negative terminal.

Table 18136-1: Freezing Point of Aqueous Solutions of Sulfuric Acid Care must be taken to avoid freezing the electrolyte either in operation or storage. If it does freeze, irreparable damage may result. Specific Gravity at 15oC 1.000 1.050 1.100 1.150 1.200 1.250 1.300 1.350 1.400

Freezing Points Centigrade

Fahrenheit

0 - 3.3 - 7.7 -15 -27 -52 -70 -49 -36

+32 +26 +18 +5 -17 -61 -95 -56 -33

4.

Connectors and battery posts should be bright and clean, then coated with a thin film of NO-OX-ID, or equal, grease. Wire brushes, steel wool, or emery cloth should not be used to clean connectors or cell posts that have copper inserts.

5.

Cell interconnections should be made with connectors and bolts supplied by the battery manufacturer. Tighten connections using two wrenches. A torque wrench is recommended using torque values supplied by the manufacturer.

6.

All storage batteries should be given an initial charge when installed. The constant voltage per cell is determined by dividing the maximum allowable buss voltage by the number of cells. Lead-calcium battery will receive the required charge when nominal float voltages are maintained and the charge is started less than six months after shipment. All lead-antimony battery or lead-calcium battery that has been stored for more than six months will require an initial/equalizing charge.

________________________________________________________________ -3–

Part 18.1.36

AREMA® C&S Manual

2002

7.

Dry charged batteries should be installed, filled with electrolyte and receive the initial charge before a load is connected. The higher voltages required for the initial charge may damage equipment if it is connected during the charging period. Remove and discard the vent plug seals before starting the charge.

8.

The objective of the initial charge of a dry charged lead-calcium battery is to establish a charge rate that produces 2.60 to 2.70 volts per cell without exceeding 120°F (49°C) cell temperature. If the constant voltage method is used, connect the charger to a reduced number of cells and charge until the required cell voltage is reached. The charger connections must then be changed to include the uncharged cells and exclude some of the charged cells. Charging time for each step should be 12 to 16 hr. If a constant current charger is used, the complete battery may be charged at one time. Adjust the charger to the finish rate and charge 12 to 16 hr. Do not exceed 120°F (49°C) or 2.72 volts per cell during either method of charging.

F.

9.

Dry charged lead-antimony batteries may be given an initial charge with either the constant voltage or the constant current method. The charge may be applied to the entire battery at one time. If the constant voltage method is used, the charge time will be slightly longer for a given volts per cell than the initial charge of wet charged battery. If the constant current method is used, adjust the charger to the finish rate and charge for 12 to 16 hr. If cell temperatures reach 120°F (49°C), decrease the charge and increase the time proportionally.

10.

When the initial charge of a new battery is completed, record the voltage and specific gravity of each cell. This information should be kept as part of the permanent record. Specific gravity (corrected to 77°F (25°C)) of all cells should be between 1.200 and 1.220 for nominal 1.210 specific gravity battery.

Operation 1.

Lead-acid storage batteries are normally operated by float charging or a combination of float charging and equalizing charges.

2.

In float charging the battery is continuously connected in parallel with the charger and the load. The charger supplies current for the equipment load and in addition supplies enough current to keep the battery fully charged. The voltage at which this occurs is normally called the float voltage. Refer to Tables 18136-2 and 18136-3 for recommended voltages.

________________________________________________________________ -4–

AREMA® C&S Manual

2002

Part 18.1.36

3.

Equalizing charges are given, at a higher voltage than the float charge, for a definite period of time. Its purpose is to compensate for any irregularities that occur in the battery or individual cells. Refer to Tables 18136-2 and 18136-3 for recommended voltages and time.

4.

Lead-antimony batteries require an equalizing charge at least once every three months.

5.

Lead-calcium batteries floated below the nominal volts per cell should be given an equalizing charge whene ver the lowest cell in a string drops to the critical voltage in Table 18136-3. Lead-calcium batteries floated at the nominal volts per cell should not require equalizing charges.

6.

voltmeters used during float charging should be kept in accurate calibration. Check with a known standard at least every twelve months.

7.

Any lead-acid storage battery should be recharged as quickly as possible following an emergency discharge. This can be done by charging the battery at the equalizing voltage until all cells are fully charged.

Table 18136-2: Lead Antimony Cells Charge Voltage Per Cell (VPC) (1.210 Specific Gravity) Initial VPC Hours 2.39

40

2.36

60

Float VPC

Equalize VPC

2.15 to 2.17

2.33 for 8 to 24 hr.

2.33 110 2.30 168 2.24 210 Table 18136-3: Lead Calcium Cells Charge Voltage Per Cell (VPC) Specific Gravity Cells 1.210 1.225 1.250 1.275 1.300

Float VPC

Initial/Equalize (VPC)

of Minimum

Nominal

Critical Cell Voltage

Nominal VPC

2.17 2.18 2.20 2.23 2.27

2.20-2.25 2.22-2.27 2.25-2.30 2.29-2.34 2.33-2.38

2.13 2.15 2.18 2.20 2.23

2.33-2.38 2.36-2.40 2.38-2.43 2.40-2.46 2.45-2.50

________________________________________________________________ -5–

Part 18.1.36

AREMA® C&S Manual

2002

8.

Total discharge of a battery should be avoided if possible. The load should be disconnected when the buss voltage drops below the minimum equipment requirement. If a battery is to be taken out of operation for a period of time, rules for storage should be observed.

9.

Connecting loads to only a part of the battery is not recommended. If this is a requirement, an additional load should be added to the balance of the battery to equalize the cell voltages.

10.

The normal battery operating temperature is between 60°F (15°C) and 90°F (32°C) averaging about 75°F (24°C). Higher than normal temperature will: a.

Increase capacity (see Figure 18136-1);

b.

Increase internal discharge or local action losses;

c.

Raise charging current for a fixed charge voltage; and

d.

Shorten battery life.

Lower than normal temperatures will ha ve the opposite effect and decrease the maintenance required.

________________________________________________________________ -6–

AREMA® C&S Manual

2002

Part 18.1.36

Figure 18136-1: Battery Capacity vs. Operating Temperature G.

Maintenance 1.

2.

Lead-acid storage battery will remain in good condition for many years if the following rules are observed: a.

Maintain the battery fully charged.

b.

Keep the water level within the recommended limits.

c.

Keep the battery clean.

d.

Maintain a record of battery condition and maintenance activity.

The state of charge of a battery can be measured by the specific gravity of the electrolyte. Specific gravity lowers with discharge and rises with charge. The normal reading for a fully charged cell is 1.210 at 77°F (25°C). Some batteries are designed to use electrolyte with specific

________________________________________________________________ -7–

Part 18.1.36

AREMA® C&S Manual

gravity other than 1.210. marking on the cells.

2002

Refer to the manufacturer’s specification or

Figure 18136-2: Water Consumed Per Cell Per Year 3.

Specific gravity is measured by floating a hydrometer in electrolyte. A hand held bulb type hydrometer is generally used but some cells may be equipped with internal hydrometers or charge indicators. One cell in a battery is usually selected as a pilot cell for recording readings. Because a slight amount of electrolyte is lost in taking readings with a portable hydrometer, a different pilot cell should be selected after about 30 readings.

4.

Specific gravity varies with temperature and the electrolyte level. Normal readings will increase 0.001 for each 3°F 1 (.65°C) increase in temperature and conversely the readings will decrease at the same rate. Specific gravity will increase approximately 0.015 for each 1/2-in. decrease in electrolyte level below the full mark.

5.

Specific gravity readings may be in error if taken after adding water or when a cell is charging. The electrolyte must be evenly mixed for ________________________________________________________________ -8–

AREMA® C&S Manual

2002

Part 18.1.36

accurate readings. After adding water thorough mixing may take several days for lead-antimony cells and up to several weeks for lead-calcium cells. During charge strong acid is released from the plates and falls toward the bottom of the cell where it gradually diffuses through the solution.

H.

6.

Water additions are required at various intervals depending upon the type of battery and the charging rates. Electrolyte should be maintained between the high and low level markings on the cell. Never permit the level of the electrolyte to fall below the top of plate separators. Excessive use of water may indicate over charging. Refer to Figure 18136-2 for normal rates of use.

7.

Water used in electrolyte should be distilled or approved water. Battery manufacturers can provide information or assistance in determining the quality of local water.

8.

In temperatures below 0°F (-18°C) water should be added just before an equalizing charge to insure thorough mixing and prevent freezing. Refer to Table 18136-1.

9.

Clean the outside of the cells with a water-moistened cloth to remove dust and dirt. If electrolyte is spilled on the covers, neutralize it with a cloth moistened with a soda solution, then wipe with a water-moistened cloth. Never use solvents, detergents, cleaning compounds, oils, waxes or polishes on plastic containers.

10.

Keep connectors and posts corrosion-free and coated with NO-OX-ID, or equal, grease.

11.

A record of battery operation is a valuable tool in determining equipment faults, checking maintenance procedures, and indicating when corrective action is necessary. The interval for recording information will vary with location and system routines. A permanent record should start with the initial charge and continue through the life of the battery. A form should be provided to record all the necessary battery readings taken during each recording interval. Refer to Figure 18136-3.

Battery Record 1.

The following information should be recorded: a.

Date and description of last equalizing charge (if battery is leadantimony).

________________________________________________________________ -9–

AREMA® C&S Manual

Part 18.1.36

2002

b.

Battery floating voltage; pilot cell hydrometer reading and temperature, once weekly or as often as an unattended site is visited.

c.

Individual cell voltages to the nearest hundredth of a volt, once a month.

d.

Individual cell specific gravities and temperature of the highest and lowest cell, once every three months.

e.

Water additions when required.

These intervals are typical. The battery manufacturer may recommend other intervals according to the type of battery or service.

I.

2.

Call voltages should be read while the normal charging current is being maintained. Specific gravity readings should not be taken while a battery is on a high rate of charge.

3.

A continuing decline in specific gravity of the pilot cell indicates insufficient charge caused by low float voltage. When floating charge is correct the hydrometer reading will stay close to the maximum value for the cell.

4.

If a particular cell or group of cells shows lower than normal readings the cause may be uneven temperatures or internal cell troubles. Contamination of electrolyte can cause cell troubles.

Spent Batteries 1.

Spent batteries shall be handled in accordance with Manual Part 9.5.5 (Recommended Instructions for Disposal and Recycling of Batteries).

________________________________________________________________ - 10 –

2002

AREMA® C&S Manual

Part 18.1.36

20

Figure 18136-3: Stationary Battery Report

________________________________________________________________ - 11 –



Section 19 – Electrical Protection 2002



Index

SECTION 19 - ELECTRICAL PROTECTION Part

C

Type & Subject

19.1.10

35-1

Recommended Functional/ Operating Guidelines for Surge Protectors That Operate to Ground

2

Reaffirmed 1989

Recommended Practices for Installation and Maintenance of Grounds for Communication Facilities

9

Revised 1995

Recommendations for an Electrostatic Discharge (ESD) Control Program

16

New 1994

19.1.14

19.1.20

35-1

35-2

Pages

Status

______________________________________________________________ -1Note: C =



- 1 – AREMA C&S Manual 1989

Part 19.1.10 Recommended Functional/Operating Guidelines for Surge Protectors That Operate to Ground Reaffirmed 1989 (2 Pages)

A.

These recommended functional/operating guidelines are for surge protectors that operate to ground. They set forth specific detail requirements representing modern communication practice recommended for new installations and for replacement of existing installations when general renewal or replacement is to be made.

B.

The protector shall match the characteristics of the equipment being protected insofar as: (1) Breakdown voltage rating (2)

Time-current capacity limits

C.

It shall be capable of withstanding a large number of repetitive surges and be self-restoring except when subjected to direct lightning strikes and power line s.

D.

It shall retain its electrical characteristics after repeated operations within limits as may be specified. The minimum values of these limits must not be less than those required by Section B above.

E.

Below its breakdown point, the protector shall have a minimum initial resistance of 10,000 megohms across its terminals. This resistance shall not go below 1,000 megohms during the anticipated life of the protector.

F.

When the breakdown surge is removed, the protector shall immediately restore to normal.

G.

If the protector shall fail, it shall fail safe, permanently short-circuiting its terminals to ground.

H.

It shall not introduce capacity, resistance or inductance that would adversely affect the operation of the circuits it is protecting.

I.

It shall not cause any undue hazard to personnel either in its idle state or under operating conditions.

J.

The protector shall be capable of normal operation under such environmental conditions as may be encountered.

K.

Except for special cases when large heat dissipation must be considered, it should be capable of fitting into existing types of arrester mountings, when provided.

- 2 – AREMA C&S Manual Part 19.1.10

1989

L.

It shall be easily installed and readily replaceable.

M.

It shall be capable of simple nondestructive testing with readily available test equipment.

N.

It shall be so constructed that it will not create a fire, toxicity or radiation hazard.

O.

It shall be so constructed that it will withstand anticipated handling and shipping abuse without damage.

P.

The protector holder shall be designed to permit connection of an adequate ground conductor as defined in governing electrical codes. There shall be a firm electrical connection between this holder and the ground electrode of the protector.


Part 19.1.14 Recommended Practices for Installation and Maintenance of Grounds for Communication Facilities Revised 1995 (9 Pages)

A-1

A-2

B-1

A-General Function: The function of a grounding system is to provide a path to ground for currents resulting from lightning, induction and crosses with foreign circuits. General Requirements: A good grounding system is of great importance and should be designed and installed in a manner that ensures optimum conductivity to ground in order to safeguard employees and the general public from injury and to protect equipment from damage that may otherwise be caused by electrical potentials. B-Definitions Approved: Acceptable to the authority having jurisdiction. Equipment is normally considered acceptable if it is accepted, or certified, or listed, or labeled, or otherwise determined to be safe by a nationally recognized testing laboratory, such as, but not limited to, Underwriters Laboratories, Inc., Factory Mutual Engineering Corp. and the Canadian Standards Association.

B-2

Arrester: A device designed to limit transient voltages on equipment or conductors. The normal arrester condition is in the open circuit mode, until its breakdown voltage is exceeded. After breakdown, the arrester discharges current to ground across its GAP. The arrester again assumes the open circuit condition after the age of the surge.

B-3

Bond: A conductor providing a low impedance path between metallic parts required to be electrically connected.

B-4

Earth: The earth's potential is normally considered to be the reference electrical potential. Due to the relatively high resistivity of soil, it is not possible to make a zero impedance connection to the reference earth potential.

B-5

Electrode: A metallic object used as a terminal to connect to the reference earth potential.

B-6

Existing Electrode: Direct buried metallic piping systems, metal building frameworks, well casings, steel piling, and other underground metal structures installed for purposes other than grounding and having suitably low impedance to the reference earth potential, are classified as existing electrodes.

B-7

Exothermic Weld: A process in which a permanent electrical connection of copper to copper or copper to steel is made.


1995

An exothermic chemical reaction is utilized to produce molten copper that welds the desired metal components together. During the welding process, a ceramic or graphite mold is used to contain the molten copper around the objects being welded together. B-8

Ground Conductor: The conductor that connects the protector or the communication equipment ground point to the ground electrode.

B-9

Grounded Conductor: The conductor of the utility electrical service that is intentionally connected to a ground electrode (neutral conductor).

B-10 Grounding System: The grounding system consists of the ground conductor, electrode connection and the electrode. The purpose is to maintain the same impedance from any point connected to that system to ground. B-11 Made Electrode: Metallic objects such as rods, pipes, plates, etc., specifically installed to obtain a sufficiently low impedance connection to the reference earth potential. B-12 Multi-Grounded Neutral: The neutral conductor of the utility electrical service where the neutral conductor is connected to a made electrode at each transformer location and at a sufficient number of additional points to total not less than four electrode connections in each mile of line, not including electrode connections at the individual services. B-13 Patina: A green or greenish-blue crust or film on bronze or copper formed by oxidation. B-14 Protector: Similar to any arrestor, except it can fail in an open or closed circuit condition as defined by its construction. B-15 Sectional Rods: Sectional rods are ground rods that are threaded at both ends and can be ed together with threaded couplings to achieve whatever driven depth is required. Any sectional rod may be used as a top, intermediate, or bottom section. B-16 Sphere of Influence: An electrode in soil of uniform resistivity radiates current in all directs. The electrode can be considered to be surrounded by shells of soil, all of equal thickness. The shell nearest the electrode has the smallest surface area and so offers the greatest resistance. The next shell is somewhat larger in area and offers less resistance; and so on out. Finally, a distance from the


Part 19.1.14 electrode is reached where an additional shell of soil will not add significantly to the total resistance. This is the dimension of the sphere of influence of the electrode. For a ground rod or pipe, the radius of the sphere of influence can usually be considered to be equal to the driven depth of the rod or pipe.

C-1

C-Choice of Electrodes Existing Electrodes: An extensive direct buried metallic cold water piping system is the preferred electrode where it is readily accessible. Such systems normally have a resistance to earth within the maximum values given in Table II and have been used extensively in the past.

C-2

A direct buried cold water piping system with nonmetallic pipe, corrosion protected metallic pipe, or metallic pipe with insulated ts is not suitable for use as a grounding electrode.

C-3

Insulated or non-insulated underground cold water piping connected to a well that has a measured resistance to earth within the maximum values given in Table 2, may be used as a grounding electrode. Care must be exercised to assure that all parts of the piping system that may be disconnected at some time in the future are effectively bonded together.

C-4

Direct buried metallic piping systems other than for cold water (steam pipes, gas pipes, sprinkler systems, air lines, etc.) shall not be used as a grounding electrode.

C-5

Made Electrodes: Where a suitable existing electrode is not available or where it is desired to have a supplemental electrode, a made electrode must be installed.

C-6

Made electrodes shall be of metal or combinations of metals that do not corrode excessively under the existing conditions for the expected service life of the communication installation. All outer surfaces of a made electrode shall be conductive, that is, not having paint, enamel, or other insulating type covering.

C-7

Made electrodes shall, as far as practical, penetrate below the frost line and into permanent moisture level. Failure to reach permanent moisture may not only result in high resistance to earth, but may also result in large variations in resistance during changes of the seasons.

C-8

Made electrodes may buried wire, buried Driven rods are the recommended type of

consist of driven rods, driven pipes, plates, or buried strips of metal. most generally used and are the made electrode.

- 4 – AREMA C&S Manual Part 19.1.14 C-9

1995

Driven Rods: Driven rods shall have a minimum cross-sectional dimension of 1/2 in., a total length of not less than 5 ft., and shall have a driven depth of not less than 5 ft. Where a rock bottom is encountered, the driven depth may be less than 5 ft., or a different type of electrode employed.

C-10 Copper, copper-clad steel, galvanized steel, and stainless steel rods are the most popular. C-11 In order to achieve a resistance to earth within the maximum values given in Table 2, multiple rods connected in parallel or sectional rods coupled together (to achieve a greater driven depth), or a combination of the two may be used. C-12 Multiple rods should be spaced a distance apart at least equal to the driven depth of the rods and preferably twice the driven depth but in no case less than 6 ft. This will minimize the effect of overlapping of the spheres of influence of the rods. In general, sectional rods coupled together to achieve a driven depth down to the permanent moisture level of the soil is more efficient that the same total length of multiple single-length rods connected in parallel. C-13 Electrical Service Grounding Electrods: Where the grounded conductor of the electrical service to the building is grounded to an acceptable water pipe electrode, the communication ground connection may be made to either the metallic service conduit, the service-equipment enclosure, or to the service grounding conductor. C-14 Where an acceptable cold water pipe electrode is not available and the electrical service to the building has a multi-grounded neutral, the communication ground connection may be made to either the metallic service conduit, the service-equipment enclosure, or to the service-grounding conductor. D-1

D-2

D-Ground Conductor Material: Grounding conductors shall be copper, solid or stranded and shall be insulated in accordance with section 800 of the latest edition of the National Electrical Code. Sizes: Grounding conductors shall not be smaller than the sizes listed in Table 1.


Part 19.1.14 Table 1 Number of Arresters

Size of Copper Ground Wire

1 to 10

No. 14 AWG

11 to 20

No. 12 AWG

21 to 40

No. 10 AWG

41 to 80

No. 6 AWG

Over 80

No. 4 AWG

D-3

Splices: A grounding conductor shall be installed in one continuous length without a splice or t. Where the grounding conductor is used for connections to other apparatus in addition to the protectors, those connections shall be made by extending the ground wire rather than making taps or T-splices. See Paragraph E-3 for exception on splices.

D-4

Self Impedance: It is very important that the ground conductor is kept as short as practical and with a minimum number of bends in order to keep the self-impedance of the ground conductor as low as possible. For the same reason, a ground conductor should not contain bends exceeding 60 degrees or coils.

E-1

E-Electrode Connection The connection of a ground or bond wire to an electrode shall be as accessible as practical and shall withstand vibration and exposure to the elements while maintaining a permanently low resistance connection. Wherever possible exothermic weld, silver soldering or brazing is recommended.

E-2

To Water Pipes: For connection to a water pipe, an approved pipe grounding clamp or an exothermic type weld shall be used. Before connection is made check that path to ground is uninterrupted by plastic, rubber or other types of nonconducting materials.

E-3

To Driven Rod: For connection to a driven approved ground rod clamp or an exothermic be used. If the rod electrode is equipped the connection shall be made by means of a sleeve to the tail wire.

E-4

To Other Electrodes: For connection to a steel member, an approved lug or an exothermic type weld shall be used.

E-5

Surfaces: If any coating of non-conducting material, such as enamel, rust, or scale, is present on the

rod electrode, an type weld shall with a tail wire, compression


1995

electrode surface at the point of connection, the coating shall be thoroughly removed to obtain a good connection and conductive paste used between dissimilar materials. Special approved fittings designed to make the removal of a non-conducting coating unnecessary may also be used. F-1

F-Installation Existing Electrodes: As previously stated, an extensive direct buried cold water metallic piping system forms the most satisfactory ground electrode and shall be used whenever practical. Connection of the ground wire shall be made on the street side of all fittings such as valves, meters, etc. when possible. When this is not possible, it is necessary to install bond wires around meters, valves or other fittings.

F-2

Made Electrodes: The preferable location for a made electrode is where the surrounding earth will be moist throughout most of the year. Abundant vegetation usually indicates underlying moisture and favorable conditions; however, if the soil is such that the surface water readily seeps away, the natural salts in the earth are dissolved and carried off, leaving the earth a relatively poor conducting medium. For this reason filled-in ground, gravelly or sandy soil and, in some cases, fresh water streams, are not desirable locations for made grounds.

F-3

Bonding of Electrodes: A bond shall be of copper and shall not be smaller than No. 6 AWG or its equivalent. A bond shall be installed between the communication grounding electrode and the electrical power-grounding electrode where separate made electrodes are used in or on the same building or structure. Bonding together of all separate electrodes will limit the potential differences between them and between their associated wiring systems.

F-4

Run In Straight Line: The grounding conductor shall be run to the grounding electrode in as straight a line as practical without any sharp bends, coils or kinks. Sufficient slack shall be left in the grounding conductor at the grounding electrode to insure against possible breakage of the conductor due to vibration (i.e., water pipe) or settlement (i.e. driven rod), etc. Under no circumstances shall the slack be taken up in the form of a coil.

F-5

Physical Damage: Where necessary, the grounding conductor shall be guarded from physical damage with molding, etc. The protection from physical damage shall extend at least 8 ft. above ground.

F-6

Through Metallic Duct Or Conduit:

If the grounding


Part 19.1.14 conductor is run through a metallic duct or conduit it must be bonded to each end of the duct or conduit.

F-7 G-1

Splices:

See Paragraph D-3.

G-Resistance to Earth The grounding electrode system may consist of one or more electrodes bonded together. The resistance to earth of the grounding electrode system shall not exceed the values given in Table II under ordinary conditions. If a particular situation dictates, a lower resistance may be required. Table 2 Plant for Which Ground is Provided

H-1

Maximum Allowable Resistance

Offices with power facilities or with suitable water pipe ground.

10 ohms

Offices with made ground and with protectors for over 10 wires.

25 ohms

All other offices.

50 ohms

Booths and shelter boxes.

75 ohms

Cable terminals (except where cable sheath ground is used) and grounds for messages.

100 ohms

H-Measurement of Electrode Resistance In general, experience in any given location will enable an installer to determine whether or not an existing electrode will have a resistance within the limits given in Table II or what type and configuration of made electrode will be required. It is recommended, however, that the resistance of an existing electrode, as well as a made electrode, should be measured before it is placed in service.

H-2

The resistance to earth of a made electrode may vary considerably from time to time due to the amount of moisture contained in the earth. Therefore, measurements of electrode resistance to ground should not be made during those times when the moisture content of the earth is greater than normal.

H-3

The resistance of an electrode to earth may be easily measured by using a direct reading instrument specifically designed for this purpose. This type of instrument permits the resistance to be measured with a minimum amount of time and effort. It is strongly recommended that an instrument specifically designed for measurement of electrode resistance to earth should be used rather than using instruments designed for other purposes.


1995

H-4

The electrode under test should be isolated from the grounded equipment during the measurement procedure in order to obtain an accurate resistance measurement. Preferably, the ground conductor should be disconnected from the electrode. This temporary disconnection of the ground conductor shall be permitted only under competent supervision and for testing purposes only.

H-5

There are two methods generally used to measure the electrode resistance to earth. The two terminal method, also known as the direct method, and the three terminal method, also known as the fall-of-potential method.

H-6

Two Terminal Method: This is the simplest method but it can be used only if certain requirements are met. First, an existing electrode of known low resistance to earth (such as an extensive direct buried metallic cold water piping system) must be available. Second, the electrode under test must not be in the sphere of influence of the existing reference electrode. The instrument is connected to each electrode and measures the sum of the resistances to earth of the two electrodes. The resistance to ground of the electrode under test is obtained by subtracting the resistance to ground of the known electrode from the measured resistance.

H-7

Three Terminal Method: In the three terminal method, two small test probes, which are part of the test instrument, are used in conjunction with the electrode under test. A reference electrode is, therefore, not required. Consult the instructions with the particular test instrument being used for information on performing this measurement.

H-8

When using either the two terminal method or the three terminal method, care should be exercised to avoid influence of the test readings by any stray ground currents or buried metallic pipes, etc.

J-1

J-2

J-Reducing Resistance of Made Electrodes Chemical Soil Treatment: When deep driven rods are not possible due to hard underlying rock, etc., and the number of multiple paralleled rods required make this approach impractical, then chemical treatment may be required. Chemical treatment of the soil around a ground rod reduces the resistivity of the soil and, therefore, the resistance of the ground rod to earth. Chemical treatment is also beneficial in reducing seasonal variations in resistance due to periodic wetting and drying out of the soil. There are several methods used in chemical soil treatment including the trench method and the basin method.


Part 19.1.14

J-3

Trench Method: In the trench method, a donut shaped trench is dug around the ground rod with a depth of about 12 in. The chemical is poured into the trench and covered with a layer of soil. This method eliminates direct of the chemical with the rod.

J-4

Container Method: In the container method, a tile pipe about 16 in. long and 8 in. in diameter (or other suitable open ended container) is buried 4 to 6 in. from the ground rod. The container is filled with a chemical and covered. The chemical slowly washes into the soil near the electrode. This method does not treat the soil as fast as the trench method but is has a longer interval between treatments.

J-5

Chemicals: The most generally used chemicals are magnesium sulfate, copper sulfate and ordinary rock salt.

J-6

Treatment Intervals: Chemical treatment is not permanent because the chemical is gradually washed away by rainfall and natural drainage through the soil. Depending on local conditions, the interval between treatments varies but may be up to several years long.

K-1

K-Maintenance Inspection and Tests: Inspections and tests should be made at regular intervals, as determined by past experience with grounding systems in a particular area, to insure that the grounding system meets the requirements of this specification. Records should be kept so that a general trend of increased ground resistance will be evident.

K-2

All ts and connections should be periodically inspected. If found faulty, repairs shall be made as required.

K-3

A green film called a patina may form on copper ground conductors and electrodes due to the unavoidable corrosion process. This patina should not be cleaned off because it slows down the process of corrosion, even though it was originally caused by corrosion.

L-1

L-References Reference was made to the following codes and standards in the preparation of this recommend practice. American National Standard Institute National Electrical Safety Code, ANSI C2-1981 National Electrical Code, NFPA 70-1981 Canadian Electrical Code, C22.1-1982



Part 19.1.20 Recommendations for an Electrostatic Discharge (ESD) Control Program New 1994 (16 Pages)

A.

Purpose The purpose of an ESD control program is to provide electronic assemblies and components with continuous protection from ESD.

B.

General 1. Static damage can result in destruction or catastrophic failure when high voltage and instantaneous current flow cause the melting of metallic oxide and other components. 2.

Static damage can cause life degradation or latent defects.

3.

Intermittent failures can occur when transient induced current and polarization cause a device to fail intermittently. This type of damage is very difficult to detect.

4.

In order to prevent static damage to electronic parts and assemblies, a railroad should establish and enforce an ESD control policy that includes the following six steps:

5.

(a)

Insure that vendors provide ESD protection during manufacture and shipment.

(b)

Insure that all ESD sensitive items are marked with an ESD caution label.

(c)

Provide appropriate instructions for personnel who will be handling ESD sensitive items.

(d)

Transport ESD sensitive items only in appropriate packaging.

(e)

Open ESD protective packaging only in ESD protected conditions

(f)

Insure that the ESD protection is functioning properly.

Definition of ESD: Electrostatic Discharge, a sudden redistribution of static charge that is damaging to sensitive components.


1994

ESD-Sensitive (ESDS): A part, assembly or product that can be degraded or damaged by ESD. There are ESDS parts in nearly every family of electronic components containing thin films or insulators, including resistors, capacitors and semiconductor devices. All unmarked components or assemblies and all Class 0, Class 1, and Class 2 devices should be considered as ESDS parts. See Part Classification Table 1. ESD Controlled Area: A specifically designated area that has been properly marked and equipped for handling ESD-Sensitive assemblies and components. ESDS parts should only be removed from ESD packaging in an ESD Controlled Area. Triboelectricity: The transfer of charge by and separation of two surfaces. This charging by "rubbing or separating" is a common source of static charges. Antistatic: A material that resists triboelectric charging and produces a static voltage of less than 100 volts when rubbed against itself or another material. A material's antistatic property is not necessarily correlated with its resistivity, and can be degraded by factors such as age, wear, contamination, solvents and climate. Conductive: A material with surface resistivity less than 100,000 ohms per square and volume resistivity less than 10,000 ohm-cm (Per mil HDBK-263A), generally achieved by means of coating or impregnating with carbon or metal. Conductive materials are not necessarily antistatic. A static-shielding enclosure ("Faraday Cage") requires conductive materials. Dissipative: A material with surface resistivity from 100,000 ohms to 1,000,000,000,000 ohms per square and volume resistivity between 10,000 ohm-cm and 100,000,000,000 ohm-cm (Per mil HDBK-263A). Static Shield: A conductive surface that terminates all the static field lines that intersect it. A Faraday Cage is a static shield formed into a closed container. This is the best form of protection for ESDS items that may be transported or stored in static-unsafe areas. Reuse: To use a product more than one time without altering its physical construction. Inspecting, and relabeling are permitted within the definition of reuse.

- 3 – AREMA C&S Manual 1994 C.

Part 19.1.20 Part Classification (ESD) The part supplier shall establish, and furnish upon request, the level of susceptibility to ESD for each individual part, family or assembly per the following classes (per MIL-STD-1686) based on Human Body Model: CLASS CLASS CLASS CLASS

0 1 2 3

Table 1 0 0 2000 4000 -

200 1999 3999 15,999

V V V V

Unless otherwise stated all ESDS Parts should be treated as Class 1 for the level of susceptibility to ESD damage. D.

Responsibility 1. An individual should be designated who is responsible for the implementation and istration of the ESD control program. ESD coordinators should be designated in each work area where the guidelines are to be enforced. The ESD coordinator is responsible for yearly and monthly ESD Audits. Appendix A provides a sample ESD Audit Form. 2.

All employees should in the enforcement of these policies by bringing any deficiencies to the attention of their manager or the ESD coordinator.

3.

Employees are responsible for escorting and assuring that ALL VISITORS adhere to the ESD guidelines, and should report when visitors are coming into ESD protected areas to the ESD Coordinator.

E.

Training All personnel who come in , or may come in with static sensitive parts, shall have instruction in the safe handling of those items. These instructions should enable personnel to meet the requirements of this policy. Approved ESD protection instructions will be provided by the ESD coordinator.

F.

Labeling Recommendations 1. ESD Symbols (a)

Recommended Symbol: The recommended symbol for ESDS devices is defined by EIA-471 (Figure 1). It consists of a triangle enclosing a hand, crossed by a diagonal slash, and the words "ATTENTION, OBSERVE PRECAUTIONS FOR HANDLING ELECTROSTATIC SENSITIVE DEVICES". The colors are not specified,


1994 but a black symbol on a yellow background is recommended.

(b)

Acceptable Symbol: The MIL-STD-1285 is acceptable for use but must be accompanied by the EIA symbol when used for ESD control. All packages containing Class 1 or 2 ESDS items shall display an approved static attention label on the outside of the static container.

(c)

Yellow or fluorescent orange-red are the preferred colors for caution signs and labels. Thus, ESD control labels and signs should preferably be black on yellow, in triangular or rectangular shapes.

Figure 1 EIA-471 RECOMMENDED LABEL

Figure 2 MIL-STD-1285 ACCEPTABLE LABEL

- 5 – AREMA C&S Manual 1994 G.

Part 19.1.20 Handling Requirements 1. Packaging (a) All electrostatic sensitive parts shall be protected from electrostatic discharge by protective packaging.

2.

-

All electrostatic packages containing electrostatic sensitive parts must be labeled with an appropriate ESD Caution label.

-

Circuit assemblies and components are only protected when completely enclosed inside an antistatic protective environment such translucent static shielded bag, pink or blue poly antistatic bag, or black conductive container.

(b)

Sensitive parts shall be shipped from the manufacturer in electrostatic protective packaging and labeled with an ESD label. These parts shall remain in that packaging continuously except when actually at a static free workstation.

(c)

Circuit assemblies shall be placed in static shielded bags or conductive containers for transportation or storage.

Workstations (a) Workstations used for handling sensitive parts must be equipped with static free work surfaces and floor mats. These surfaces and mats must be static dissipative and grounded to a true earth ground. (b)

All electrical equipment used at static free workstations must be grounded. Soldering irons shall be of an approved ESD protected design.

(c)

Workstation chairs or stools must be grounded in one of two ways: carbon filled conductive casters or brass drag chains attached to the center of the chair base. These chairs or stools must be used in conjunction with static free floor mats.

(d)

No plastic materials shall be allowed within three feet of static free workstations. This includes candy wrappers, tape, cigarette packages, cellophane wrappers, foam cups, foam packaging (peanuts), bubble wrap, plastic bins, plastic folders, etc.


1994

EDS Figure 1


Part 19.1.20 (e)

3.

4.

H.

Temperature and humidity monitors should be installed in ESD safe areas and are to be monitored by personnel in each area for humidity levels. Humidity levels that reach 25% or less should be reported to the ESD coordinator, as these levels present possible ESD problems.

Personnel (a)

The wrist strap must be worn in direct with the bare skin. Personnel shall not be attached directly to an earth ground. There must be a safety 250k Ohm to 1 Meg Ohm resistance between the operator and the ground (these resistors have been molded into the ground cords of some ESD mats).

(b)

All personnel within three feet of a static free work station must be grounded with a wrist strap and ground cord attached to the grounded work surface.

(c)

The wrist strap shall be functionally checked by the daily. Testers should be placed in all ESD protected areas for this purpose. Equipment is also available to continuously monitor the wrist strap.

(d)

Improperly grounded or ungrounded personnel shall never touch static sensitive parts, assemblies, or other operators at a static free work station.

Equipment locations (a)

A railroad may elect to place properly grounded floor mats on floors where access is made to any system using plug in cards with ESDS components. This should include microwave equipment, electronic switchboards, packet switches, rack mounted data modems or multiplexers, radio base stations, and other electronic equipment.

(b)

A properly grounded wrist strap should be attached to the equipment rack.

(c)

Alternatively, a portable service kit containing ESD mat and wrist strap can be used when servicing installed equipment.

Maintenance of Static Protective Equipment 1. Workstation Mats The surface of mats must be cleaned with an antistatic


1994

cleaner, monthly, or more often as required, to prevent contamination from dirt, grime, solder, body oils, dust particles, etc.

I.

2.

Wrist Bands Wrist bands may be laundered, using a mild detergent no bleach, as required to prevent body oils from compromising the electrical functionality of the material. Care must be taken to place the band in a pocket to keep it from becoming entangled in the agitator of the washing machine.

3.

Smocks (Lab Coats) All personnel are to wear conductive smocks while working on Static Sensitive components or assemblies.

(b)

All other personnel including visitors are to wear conductive smocks while working in or touring the ESD Protected Area.

(c)

Smocks may be laundered, using a mild detergent no bleach, by the at home, or by an approved garment laundering agency.

Maintenance Shop Area, Warehouse, and Staging Areas 1.

2.

J.

(a)

The ESD Protected Area floor should have an anti-static surface applied to it. Facility maintenance will maintain the floor on the following schedule: -

weekly - anti-static wax to be applied to surfaces where required.

-

yearly - floor to be stripped and retreated.

Areas designated as a Static Safeguarded Work Area are marked by ESD signs informing personnel of the ESD Policy and by a yellow band on the floor defining the perimeter of the area.

Electrical Tests 1. Specialized test equipment can be used to routinely proper electrical performance of the wrist strap. Follow the manufacturer's instructions to wrist strap performance. 2.

Equipment is available to continuously monitor the performance of the wrist strap and grounding. Follow the manufacturer's instructions to continuously wrist strap performance.


Part 19.1.20 3.

K.

L.

The bench/table and floor mats should be tested by a qualified ESD auditor.

Frequency of Testing Wrist Straps -

Daily - (personnel not required to use wrist straps daily, must test them before each use)

Table/Floor Mats

-

Monthly by ESD Coordinator, Yearly by Quality Assurance

Mat Ground Cords

-

Daily by Operators, Monthly by ESD Coordinator, Yearly by Quality Assurance

Ground/Connection

-

Daily by Operators

Static Shielded Bags

-

As Required. At the minimum Yearly

Ionizers

-

Yearly or as determined by the Calibration Dept.

ESD Program Supplies This section provides a listing of items that may be needed for a successful ESD control program. Antistatic Cleaner Antistatic Storage Cabinet Conductive Storage Drawers Conductive Smock (Lab Coat) Conductive Tool Box ESD Floor Mat ESD Video Tapes ESD Packaging ESD Heel Strap Field Service Ground Kit Ground Cords Ionizer Outlet Tester Portable Static Meter Static Shielding Work Surfaces Static Shielding Work Surface Tester Static Shielding Floor Finish (Antistatic Wax) Static Shielding Floor Surfaces Warning Labels Wrist Strap Wrist Strap Tester

M.

Sources This section provides a partial listing of possible sources for the ESD program supplies identified in Section J.


1994

Atrix, Inc., 14301 Ewing South, Burnsville, MN. 55337. Phone (800) 222-6154. Baxter Healthcare Corp., Scientific Products Division, 1210 Waukegan Road, McGraw Park, IL. 60085. Phone (708) 689-8410 Charles Walters, 93 Border Street, West Newton, MA. 02165. Phone (617) 964-8370. East, 335 Willow Street South, North Andover, MA. 01845-5995. Phone (508) 682-2000. HYMAR Meters, 6647 Blossom Acres Drive, San Jose, CA. 95124. Phone (408) 358-6280. JULIE Associates, P.O. Box 141, Billerica, MA. 01821. (508) 667-1958.

Phone

Motorola C&E Inc., Communications Parts Division, 1313 E. Algonquin Road, Schaumburg, IL. 60196. Phone (708) 5766485. Static Control Components, Inc., P.O. Box 152, Stanford, NC. 27331. Phone (800) 356-2728. Static Control Systems Division/3M, P.O. Box 2963, Austin, TX. 78769-6154. Phone (800) 222-6154. Westcorp, 144 S. Whisman Road, Mountain View, CA. 94041. Phone (800) 537-7828. N.

References 1. MIL-STD-1686A - Electrostatic Discharge Control Program for Protection of Electrical and Electronic Parts, Assemblies and Equipment 2.

MIL-HDBK-263, Electrostatic Discharge Control Handbook.

3.

AMCI Electrostatic Discharge Control Policy, M07093, Revision C, October 14, 1993, Automated Monitoring and Control International, 11819 Miami, Omaha, NE 68164.

4.

A sample of a more detailed Packaging and Handling Specification, ESD control policy is available from 3M Company, Electrical Specialties Division, P.O. Box 33211, St. Paul, MN 55133-3211

5.

A videotape (F.A.S.T. #5) on electrostatic discharge is available from Motorola National Service Training.


Part 19.1.20 APPENDIX A ELECTROSTATIC DISCHARGE CONTROL STANDARDS AUDIT CHECKLIST

A.

PURCHASING Audit for: 1. 2. 3. 4. 5.

B.

Appropriate ESD requirements on purchase orders. Procurement only buys ESDS parts from suppliers that have been ESD-approved by the Purchasing Department or Engineering Department. Procurement maintains a list of ESD-approved suppliers. Restrictions on packaging, labeling, and proper invoices/packing slips are imposed on vendors. Procurement maintains a list of approved suppliers, the list need not be segregated into ESD and Non-ESD suppliers, but if ESD approval is needed for a new supplier, the vendor is audited for ESD.

RECEIVING Audit for: 1. 2. 3.

C.

ESDS devices are identifiable by their outside packaging and/or invoices. ESDS devices are checked for proper packaging and marking. Areas where ESDS packages are opened are equipped with proper ESD control measures, (i.e., mats, wrist straps, proper grounding).

INCOMING INSPECTION Audit for: 1. 2. 3.

D.

Packages containing ESDS devices are opened only is ESD areas by trained, grounded personnel. ESDS items are stored in protective packaging for transfer to storage and work areas. Incoming Inspection personnel write trouble tickets on any improperly marked or packaged devices and report deficiencies to the proper ESD Coordinator, Purchasing, and Engineering.

SHIPPING Audit for: 1.

ESDS items are only handled at ESD protective workstations by trained, grounded ESD Certified

- 12 – AREMA C&S Manual Part 19.1.20 2. E.

1994

personnel. Items are labeled and packaged using appropriate labels and protective packaging.

STOCKROOMS, STORAGE AREAS, KITTING AND STAGING AREAS Audit for: 1. 2. 3.

F.

ESDS items are maintained and issued in ESD-protective packaging. Bin boxes or shelves storing ESDS devices are so labeled. ESD procedures are implemented during kitting and in staging areas.

ENGINEERING Audit for: 1. 2.

G.

ESD procedures are implemented in all engineering laboratories. Engineering Assembly drawings involving ESDS components contain references to ESD Policies and Procedures.

PRODUCT INTEGRATION AND MANUFACTURING AREAS Audit for: 1. 2. 3. 4.

5. 6.

H.

ESD designated areas and workstations are established throughout these areas. Personnel in these areas are properly trained in the use of ESD workstations and implementation of precautionary handling procedures for ESDS devices. All processing equipment is properly grounded. ESD protective materials (i.e., bags, foams, totes) are available at every workstation and ESDS devices are transferred between areas in protective containers or packaging. Special ESD control measures that are necessary (e.g., conductive flooring, personnel apparel, humidity control, ionization) are implemented as appropriate. ESD areas are clearly identified by signs/placards/caution warnings and personnel entering these areas are alerted to ESDS handing and visitor requirements.

PRODUCTION TEST AND ENGINEERING TEST Audit for: 1. 2.

ESD workstation implemented in test and burn-in areas. There is an absence of prime sources of static in test


Part 19.1.20 3. 4. 5.

I.

areas. ESD control measures are implemented. ESDS items are transferred to the next work area in protective containers. Operators are not grounded while operating voltages are applied.

QUALITY ASSURANCE Audit for: 1. 2. 3. 4. 5.

Compliance to ESD control procedures. Suppliers' and Vendors' ESD compliance. Workstations ESD certification. ESD training programs. Engineering drawings containing references to ESD Policies and Procedures.


1994 10 STEP DAILY SELF-CHECK PROCEDURES

[ ]

1.

Visually check your work area to see that there are no Static-Generating materials in or around your area, (such as carpet or plastic or other insulating materials), check to see that there are no staticgenerating tools being used such as plastic solder suckers.

[ ]

2.

Visually check to see that all ground wiring to your work station has not been disconnected or damaged. Be especially suspicious if equipment or furniture has been moved. If you have a Continuous Monitor at your station, test it to see if it is working before using.

[ ]

3.

If you are using an air ionizer, turn it on and aim it properly.

[ ]

4.

Clear your work area of static charge generators, such as untreated plastic bags, boxes, foam, tape, paper, or personal items, for a distance of at least one meter (3 feet).

[ ]

5.

Visually check that all ESD-sensitive parts, assemblies or products are completely inside their staticshielding bags or conductive containers, with nothing sticking out. Both at the beginning and end of your shift.

[ ]

6.

Make sure that there are no static generators inside the static-shielding bags or conductive containers with or without ESD sensitive parts or assemblies.

[ ]

7.

Make sure that all static-shielding bags and conductive containers have the correct static attention label on the outside of the container. Visually check staticshielding bags for tears or excessive wear.

[ ]

8.

All cleaners, solvents, coatings, sprays used at your work station must be the types approved by your ESD control static coordinator.

[ ]

9.

Never allow anyone who is not grounded closer than one meter (3 feet) to your static-safe work area. Ask them to comply with grounding and garment requirements of your area before coming into the area, touching anything, or coming closer to your work. Report all violators that fail to comply.

[ ]

10.

Put on your wrist strap and any special garments required to do your job in your area, such as smocks and conductive footwear. Test your wrist strap


Part 19.1.20 according to manufacturer's instructions and sign the check-off sheet as demonstrated by your ESD coordinator. Check your smocks to see that there are no holes, rips or tears, and that they are clean. Wrist straps are required to be checked once a day at the beginning of your shift, but should be checked after each break and before beginning work after lunch or supper.


1994 ESD AUDIT FORM

Area Audited: 1.

Responsibility: _________________

Table Mats, Qty _______ Grounds: Fail/Problem ____________________________________________________________ Aesthetics (surface is clean, no static-generating materials) Fail/Problem _______________________________________________________

2.

Floor Mats, Qty _______ Grounds: Fail/Problem ____________________________________________________________ Aesthetics (surface is clean, no static-generating materials) Fail/Problem _______________________________________________________

3.

Personal (Wrist Straps, Ground Cords, Smocks, etc.) Comments:___________________________________________________ _______________________________________________________

4.

Handing/Storage of Static Sensitive Components and Assemblies Fail/Problem ___________________________ _______________________________________________________

Additional Comments: ____________________________________________________________ Auditor:

Audit Date: _____________

CORRECTIVE ACTION Corrective Action Required:______________________________________ _________________________________________________________________ Corrective Action Completed: Approved:

Date: __________________


Section 20 – Inductive Interference 2002



Index

SECTION 20 - INDUCTIVE INTERFERENCE Part

C

Type & Subject

20.1.1

38-2

Recommended Practices for Crossing of Electrical Supply Lines and Facilities of Railroads

9

Reaffirmed 1993

Recommended Principles and Practices for Inductive Coordination of Railway Electrical Supply Facilities and the Commercial Communication Facilities

30

Extended 2001

Recommended Principles and Practices for Inductive Coordination of Electrical Supply and Communication Systems Report of the t Engineering Subcommittee of the Association of American Railroads and the Edison Electric Institute; and the Association of American Railroads & Electric Power Research Institute

18

Revised 1994

Discussion of Fundamental Factors Involved in Inductive Coordination and of Remedial Measures Applicable Under Various Conditions

82

Revised 1996

Recommended Practices for Investigating Inductive Effects on Communication Facilities

50

Revised 1997

20.1.4

20.1.6

20.1.7

20.1.8

38-2

38-2

38-2

38-2

Pages

Status

______________________________________________________________ -1Note: C =




Part 20.1.1 Recommended Practices for Crossings of Electrical Supply Lines and Facilities of Railroads Reaffirmed 1993 (9 Pages) The following is a report of the t Engineering Committee of the Association of American Railroads and the Edison Electric Institute.

A-1

A-Forward After a number of years of cooperative study of the problem of mechanical coordination at crossings of electrical supply lines and facilities of railroads, the AAR-EEI t Engineering Committee issued in August 1946 a report presenting principles and practices together with a set of specifications. These specifications were based on the Fifth Edition of the National Electrical Safety Code. In the light of the subsequent cooperative handling of crossing problems by the electric utility companies and the railroads it appears that a detailed set of specifications supplementary to the National Electrical Safety Code no longer is necessary and, further, that continuance of AAR-EEI specifications periodically revised to reflect revisions in the National Electrical Safety Code would require wasteful duplication of efforts. Accordingly, the practices have been revised to refer to the latest revision of the National Electrical Safety Code as the guide for construction at crossings.

A-2

The following Principles and Practices for Crossings of Electrical Supply Lines and Facilities of Railroads are recommended for use in the handling of mutual problems at crossings, in the interest of safety, uniformity, and economy. They have been approved as recommended practice by the Association of American Railroads and the Edison Electric Institute.

A-3

A typical crossing drawing (Figure 2011-1) and instructions for its preparation are included in this report.

B-1

B-2

B-Introductory The proper solution of any engineering problem involving more than one individual or group can best be obtained through cooperation and a mutual determination of the best engineering methods for arriving at the desired result. Both railroad and electrical supply utilities render service demanded by the public. The facilities of each exist in the same territory, and crossings of these facilities are unavoidable if service conditions of both utilities are to be met. These crossings should be made with due regard to safety of the public, the protection of the employees and facilities of both utilities, and to the quality of the


1993

service of each. The burden of expense that will be necessarily imposed on the service of each, because of the common occupancy of the same territory, should be as light as is consistent with the necessary conditions of safety. The proper establishment of these crossings is, therefore, a mutual duty on the part of these utilities to the public. B-3

B-4

Cooperative consideration to the coordination of the facilities of each should be given: a.

When new facilities of either character are to be constructed.

b.

When existing facilities are to be modified, relocated, or reconstructed.

These crossing problems involve mutual duties on the part of each utility to the other and a common duty to the public. Close cooperation is required if the best results, measured in service to the public, are to be secured. These problems may be grouped as follows: a.

Inductive Coordination: These involve inductive relations between electrical circuits of all kinds when they occupy positions of proximity to each other. Inductive coordination problems are considered in the report on "The Inductive Coordination of Electrical Supply and Communication Systems" issued October 7, 1936, by the t General Committee of the Association of American Railroads and Edison Electric Institute.

b.

Mechanical Coordination: Mechanical coordination problems relate mainly to clearances and strength of construction and arise in connection with crossings, since a physical between the facilities of the utilities may constitute a hazard or impair service. These problems must be treated only in the light of such physical relations.

B-5

It is recommended that the following principles and practices be used as a guide in connection with mechanical coordination problems.

B-6

Nothing in these principles and practices should be construed as superseding state, municipal, or other legal requirements.

C-1

C-Principles It should be the duty of each utility to expedite, insofar as practicable, all work incident to necessary crossings between the facilities of the two utilities.


Part 20.1.1

C-2

Each utility should be the judge of the quality and requirements of its own service, including the general character and design of its own facilities subject to these principles and practices.

C-3

Each utility should provide and maintain facilities adequate to meet the service requirements, including such reasonable future modifications in these facilities as changing conditions indicate to be necessary and proper.

C-4

Each utility should cooperate with the other utility so that, in carrying out the foregoing duties, proper consideration will be given to the mutual problems that may arise and so that the utilities can tly determine the best engineering solution in situations where the facilities of both are involved.

C-5

t consideration by both utilities of safety, service, convenience, and economy, and the trend of development of both utilities, should determine: a.

The general character of construction of all crossings.

b.

The best engineering solution for the coordinated arrangement and design of facilities at crossings.

c.

The istrative methods for establishing, maintaining, altering, or removing crossings.

C-6

The utilities at interest in a locality should maintain close cooperation and each notify the others of any intent to build new or extend existing facilities which might tend to contribute to the creation or modification of a crossing.

C-7

When new crossings are contemplated, they should be so located and planned as to minimize interference with existing facilities.

C-8

When crossings are to be modified, the allocation of costs between the parties at interest should be reasonable and equitable, taking into all factors involved.

C-9

Construction and inductive coordination measures employed at crossings should be in accordance with mutually acceptable practices.

C-10 Contracts, whether general or specific covering the crossings, should define conditions for the establishment, construction, maintenance, operation, modification, relocation, or elimination of the crossing. Provision should be made for review and revision of all contracts from time to time.

- 4 – AREMA C&S Manual Part 20.1.1 D-1

1993

D-Practices Agreements: Agreements may be arranged to cover specific crossings, all crossings in a given territory, groups of crossings in a given territory, or in any other suitable manner satisfactory to the utilities at interest.

D-2

Notification: When a crossing is to be established, the utility initiating the crossing should notify the other utility as early in advance of the time of construction as practicable. Such notice should show the proposed location and character of the crossing. The parties should then cooperate and decide as to the fitness of the proposed location and see that construction is in accordance with the latest revision of the National Electrical Safety Code Part 2, "Safety Rules for the Installation and Maintenance of Electric Supply and Communication Lines."

D-3

Procedure When Crossing is to be Modified: When either utility finds it necessary to change the character of its facilities at a crossing, it shall so notify the other and both shall cooperate to determine the most satisfactory way to make the modification. The utility whose facilities are to be modified shall promptly carry out the necessary work and the utilities shall cooperate to determine the equitable apportionment of the expense involved in such modification.

D-4

The expense to be apportioned should be the net expense from which shall be excluded any increased cost on of the substitution for the existing facilities of other facilities of a greater life or of improved type or of increased capacity.

D-5

t Planning: An effective way of handling situations in a given territory is through the full application of the principles of cooperation, including advance notice, advance planning, and the interchange of information.

D-6

Contracts: In either general or specific contracts, any provisions treating of the character of the facilities involved should be so worded as not to restrict changes in the character of the facilities of either utility, except that it should be recognized that such changes may involve the modification, relocation, or the elimination of the crossing.

D-7

Legal questions, including the sufficiency of right-of-way grants held by the respective utilities and the protection of title or property of both utilities, in the case of mortgages, sales, mergers, or consolidations entered into by either, should be given due consideration in the preparation of contracts.

- 5 – AREMA C&S Manual 1993 D-8

Part 20.1.1 Liability: In any of a crossing contract dealing with liability for personal or property damage, care should be taken that such are reasonable and just. E-Instruction for Filling out Typical Crossing Drawing Figure 2011-1 covering power line crossings, was primarily designed to cover proposed crossings but can be used for existing crossings. It should show all the information necessary for the complete checking of the crossings from the standpoint of construction as well as clearances.

E-1

E-2

Heading: A. Fill in the correct corporate name of the company or individual owning the crossing. B.

Show the correct location of the proposed or existing crossing in of the exact distance in feet from the nearest milepost.

C.

Either plus or minus should be marked out.

D.

The nearest milepost should be shown.

E.

Whether located at a public road or street, or not; either "within" or "not within" should be marked out.

F.

Show the name of the division.

G.

Show the name of the subdivision.

H.

Show the name of the county in which located.

I.

Show the State in which the crossing is or is to be installed so that the crossing may be definitely located.

Elevation and Plan Views: a. The elevation and plan views should be considered relatively, and the correct mile post shown under j so that pole B in the plan view will be in the same relative location as in the elevation view. b.

The dimensions J, K, K', J', N, O, P, N', O', N", and P' are for the purpose of checking the construction of the crossing.

c.

J, K, K’, and J’ should be measured parallel with the supply line.


1993

Figure 2011-1: - Typical Crossing Drawing

d.

J and J' represent the length of the two spans adjacent to the crossing span, while the sum of K and K' represents the length of the crossing span. Measurements K and K' should be made from the center line of the track or tracks.

e.

N and N' represent the lead of the head guys on poles B and C, respectively, while O, P, O', and P' represent the lead of the side guys. N" represents the lead of the head guys on poles A and D where it is not possible to install head guys on poles B and C.

f.

M or M' represents the angle the crossing span makes with the track. (To aid in filling out the data sheet, the railway company's signal, communication, or catenary line has been indicated on both sides of the track.) After the direction of the elevation view has been determined, one of the lines should be crossed out unless in the section in question the railway company has a separate pole line for its signal, communication,


Part 20.1.1 or catenary wires. This line should be labeled what it is (i.e., signal, communication and/or catenary). g.

Measurements Q and R or Q' and R' represent the distance from the center line of the supply wires to the two adjacent poles in the railway company's signal, communication, or catenary lines.

h.

The remaining measurements represented by L, L', U, T, S, S', T', and U' in the plan view are for the purpose of checking clearances and should all be measured at right angles to the track.

i.

L and L' are the distances from poles B and C, respectively, to the nearest rail.

j.

S or S', as the case may be, is the distance from the center line of the track or tracks to the center line of the railway company's line.

k.

T and T' is the distance from the center line of the railway company's line to its right-of-way line. (On the side opposite to the line the distance from center line of track to the right-of-way line should be indicated under S or S' and T or T' crossed out.)

l.

U and U' represent the distance from the right-of-way line to the crossing poles B and C, respectively.

m.

Since the distances K and K' are measured parallel with the supply line and the distances U, T, S, and U', T', S' are measured at right angles to the track, the sum of U, T, and S is a function of the angle, M times the distance K, and the sum of U', T', S', the distance K'.

n.

Under V should be filled in the number of supply wires on the top crossarm: W represents the size of the wires, X the kind of material, such as hard-drawn copper, etc., Y the voltage, and Z the tension in the wires with a temperature of 0F, and with a loading of 1/2 in. of ice and a 4-lb. wind (standard heavy loading).

o.

If the supply line is not a straight line from pole A to pole D, the approximate relative position should be plotted on the plan view to indicate which poles are corner poles and the approximate pull on the pole.

p.

In the elevation view the view of the railway company's line corresponding to the one in the plan view should be crossed out. The horizontal distance from the crossing pole to the nearest wire in the line g or g'


1993

and the vertical clearance of the supply wires over or under the wires h or h' should be indicated, as well as the clearance of the supply wires above top of rail at 60F. The height above ground, a, plus the depth of setting, b, for each of the four poles, shows the total length of these poles; c represents the height of the guy attachments, where attached to the pole, above ground; d is the circumference of the pole in inches at the top and e the circumference 6 ft. from butt; f represents the normal sag at 60F of the supply wires in the three spans respectively; i represents clearance of lowest conductor above top of rail. E-3

Crossarms and Pin Spacing: n and n' show the spacing of the pole pin wires from the center of the pole and o the spacing between wires other than the pole pair; k is the length and l the width of the crossarms used; m represents the spacing between the attachment of the two braces to the crossarm.

E-4

Vertical Profile: p represents the distance between the conductors on pole. q represents the type and make of the vertical strain clamp. r represents the type and make of the strain insulator. s represents the type and make of the neutral bracket or bracket clevis.

E-5

Data: 1 represents the type pin insulators used. 2 represents the type strain insulators used. 3 represents the type pins used. 4 represents the type crossarms: their size and material. 5 represents the type strain hardware. 6 represents the type neutral bracket or bracket clevis. 7 and 8 represent the poles: depth set.

their timber, class and

9 and 10 represent the guys: their kind, size, and strength. 11 represents the anchors: set.

their kind, size, and depth


Part 20.1.1 12 and 13 represent the guy clamps: the number used.

their kind, size, and



Part 20.1.4 Recommended Principles and Practices for Inductive Coordination of Railway Electrical Supply Facilities and the Commercial Communication Facilities Extended 2001 (30 Pages)

A.

Explanation of For the purpose of these Principles and Practices, the following are used with the meanings as given below: 1.

Abnormal Operating Conditions: Electrical operating conditions resulting when operating arrangements other than normal are established on railway electrical supply circuits.

2.

Ampere-Miles: The product of the current in any section of a circuit in which the current is the same throughout the section, multiplied by the length of the section. a.

The ampere-miles of a section of circuit in which the current is not the same throughout, is the summation of the ampere-miles for successive lengths within each of which the current is the same throughout, and which together make up the section.

b.

For rail-return circuits, the ampere-miles in a specified section are based upon currents in the conductor system, except in the case of three-wire single-phase electrifications, where the vector sum of currents in the conductor system and the distribution feeders is used as a basis.

3.

Communication Circuits: Circuits used for the electrical transmission of intelligence by wire or cable.

4.

Communication Facilities: Communication circuits and their associated apparatus.

5.

Configuration: The geometrical arrangement in transverse section of any assemblage of generally parallel conductors including their sizes and their relative positions with respect to other conductors and to the earth.

6.

Conductor: A conductor, other than traffic rails, with which devices on railway cars or locomotives make to collect electric current for the operation of motors and other apparatus on trains. A conductor may be either a wire or a


2001

rail. 7.

Conductor System: The system of conductors together with any ing wires metallically connected thereto and including conductor feeders.

8.

Conductor Feeder: A conductor that connects the conductors to the substation buses. In some instances conductor feeders may be carried along the railway and connected to the conductors at one or more points.

9.

Coordinated Transpositions: Transpositions which are installed, either in railway electrical supply circuits or in communication circuits or in both, for the purpose of recuding coupling; and which are located effectively with respect to the discontinuities of the exposure and are so arranged that those in each circuit are located with due regard to those in the other circuit.

10.

Coupling: The inter-relation of neighboring circuits by electric or magnetic induction or both, or by conduction through a common earth path, or by combinations thereof.

11.

Discontinuity: A point at which there is an abrupt change in the physical relations of railway electrical supply circuits and communication circuits or in the electrical characteristics of either circuit. Transpositions, however, are not considered as discontinuities.

12.

Distribution Feeder: A conductor used in the three-wire system of railway electrification that, in combination with the conductor system, forms the primary circuit for the substation auto-transformers.

13.

Fault Conditions: Conditions resulting when a fault to ground or a short circuit occurs on a railway electrical supply circuit.

14.

General Coordinated Methods: Those methods reasonably available for general application to communication facilities or railway electrical supply facilities that contribute to inductive coordination without specific consideration of the requirements of individual inductive exposures.

15.

Inductive Coordination:

The location, design,


Part 20.1.4 construction, communication facilities in methods which Note:

operation and maintenance of facilities and railway electrical supply conformity with harmoniously adjusted will prevent inductive interference.

Inductive interference is an effect arising from the characteristics and inductive relations of communication facilities and railway electrical supply facilities of such character and magnitude as would prevent the satisfactory and economical operation of the communication facilities if methods of inductive coordination were not applied.

16.

Inductive Exposure: A situation of proximity between railway electrical supply facilities and communication facilities under such conditions that inductive coordination should be considered.

17.

Inductive Influence: Those characteristics of railway electrical supply facilities that determine the character and intensity of the inductive field that they produce.

18.

Inductive Susceptiveness: Those characteristics of communication facilities which determine, so far as such characteristics can determine, the extent to which such facilities are capable of being adversely affected in giving service, by a given inductive field.

19.

Overhead Ground Wires: Wires installed on aerial lines and grounded at intervals, which are intended primarily to provide lightning protection for the electrical supply circuits, or to limit potential rise of structures in case of fault, or both. Such wires also provide a certain amount of shielding to communication circuits involved in inductive exposures.

20.

Phase Conductor: An insulated conductor belonging to a transmission or distribution circuit and connected to an energized terminal at a point of power supply. If two or more such conductors of a circuit are connected to a single terminal at the power source and at the load, the group of such conductors so operated in parallel is considered as one phase conductor. In a two-phase, three-wire system in which two phases have a common terminal, the conductor connected to this terminal is regarded as a phase conductor.

21.

Potential-Neutralizing Conductor: A conductor upon which is impressed a voltage substantially equal and opposite to the potential of a disturbing conductor and


2001

which is suitably installed near the disturbing conductor so as to neutralize electric induction. 22.

Railway Electrical Supply Circuits: Railway circuits (including electric transmission, distribution, propulsion, and associated circuits), used to supply electric power either for the operation of a railway, or for devices or machinery used by a railway, such as signals, lights, motors, etc. (Does not include communication circuits.)

23.

Railway Electrical Supply Facilities: Railway electrical supply circuits, equipment or other railway plant associated with such circuits. (Does not include communication facilities.)

24.

Rail-Return Circuits: Railway electrical supply circuits which are so arranged that the traffic rails form part of the circuit for current carrying purposes. Such circuits may carry alternating current or direct current or both and include such feeders and auxiliary conductors as may be connected thereto, either through direct metallic connection or through auto-transformers.

25.

Residual Current: The vector sum of the currents in the phase conductors of a transmission or distribution circuit.

26.

Residual Voltage: The vector sum of the voltages to ground of the phase conductors of a transmission or distribution circuit.

27.

Return Feeder: A conductor used to supplement the current carrying capacity of the traffic rails.

28.

Shielding: An effect, due to the presence of grounded conductors or grounded conducting structures, which in general is a reduction in coupling between neighboring circuits.

29.

Shield Wires: Wires that are installed primarily to provide reduction in coupling by shielding.

30.

Specific Coordinated Methods: Those additional methods applicable to specific situations, where general coordinated methods are inadequate.

31.

Substation: Transformation, conversion, or switching equipment, together with buses, circuit breakers, control equipment, etc., from which energy is supplied directly to the conductor system.


Part 20.1.4 32.

Stub-End Feed: A substation section, or a part thereof, in which energy is supplied in only one direction to loads in that substation section.

33.

Substation Section: Where the conductor system is not sectionalized or is sectionalized only at substations, a section between successive substations is a substation section. Where energy for a given length of the conductor system is supplied entirely from a single substation, either at the substation or by means of conductor feeders that extend from the substation, the section supplied from the single substation is a substation section.

34.

Transmission and Distribution Circuits: Railway electrical supply circuits in which current normally is substantially confined to metallic conductors, insulated from ground, having substantially balanced voltages to ground and carried on the same or immediately adjacent ing structures or in the same or immediately adjacent duct runs. Such transmission and distribution circuits generally carry alternating current and may be single-phase or multi-phase. When grounded, such circuits are grounded only at neutral or substantially balanced points as regards voltage to ground. Transmission and distribution circuits are generally distinguished from each other by the manner in which they are used. Transmission circuits are generally used to transmit power in bulk to suitable locations from which it can be distributed to points of actual utilization over the distribution circuits. While rail-return circuits may fall under this classification of distribution circuits, the treatment of inductive coordination problems involving rail-return circuits differs in many respects from that usually given to other types of circuits, and therefore rail-return circuits have been considered separately in these practices.

35. B.

Transposition: An interchange of position of conductors of a circuit between successive lengths.

Principles 1. Scope: Railway electrical supply facilities and commercial communication facilities supply essential public services and these facilities frequently require inductive coordination. The Principles herein are intended to form a basis for the cooperative handling of matters in connection with the inductive coordination of these facilities.


2001

Where coordination between railway communication facilities and commercial communication facilities is necessary, such of these Principles as apply should be followed. 2.

Duty of Coordination: Railway electrical supply facilities and commercial communication facilities should be located, designed, constructed, operated and maintained in conformity with general coordinated methods. These methods should include limiting, as far as practicable, the inductive influence of the railway electrical supply facilities, the inductive susceptiveness of commercial communication facilities, and the coupling between these facilities. Where general coordinated methods will be insufficient, such specific coordinated methods suited to the situation should be applied to the facilities of either or both kinds as will most conveniently and economically prevent interference, the methods to be based on the then existing knowledge of the art.

3.

Cooperation: In order that full benefit may be derived from these Principles and in order to facilitate their proper application, railway and communication companies between whose facilities inductive coordination may now or later be necessary, should adequately cooperate along the following lines: a.

Railway and communication companies operating in the same general territory should each give to the other advance notice of any construction, reconstruction, or change in operating conditions of its facilities that are concerned or likely to be concerned in situations requiring inductive coordination.

b.

If it appears to either company that problems of inductive coordination requiring t consideration are involved, the companies should confer and cooperate to secure inductive coordination in accordance with the Principles set forth herein.

c.

To assist in promoting conformity with these Principles, an arrangement should be set up between the railway and the communication companies whose facilities occupy the same general territory, for the interchange of pertinent data and information, including that relative to proposed and existing construction and changes in operating conditions of facilities concerned or


Part 20.1.4 likely to be concerned in situations which require inductive coordination. 4.

5.

Choice of Specific Coordinated Methods: When specific coordinated methods are necessary and there is a choice of such methods, those that provide the best engineering solution should be adopted. a.

The specific methods selected should be such as to meet the service requirements of both systems in the most convenient and economical manner without regard to whether they apply to the railway electrical supply facilities or to the communication facilities, or to both.

b.

In determining which specific methods are most convenient and economical in any situation, all factors for all facilities concerned should be taken into consideration, including present factors and those which can be reasonably foreseen.

c.

Neither party should assume to be the judge of the service requirements of the other system, or of what constitutes good practice in that system.

Inductive Coordination for Existing Situations: Railway and communication companies should exercise due diligence in applying coordinated methods to existing situations in accordance with these Principles. When railway electrical supply facilities or communication facilities are generally reconstructed, rearranged, or extended, the new or changed parts should be brought into conformity with these Principles.

6.

Coordinated Locations for Lines: Railway electrical supply circuits are, as a rule, located along railway rights-of-way as it is usually impracticable to locate these circuits elsewhere. In order to provide adequate service communication lines are located along streets, highways and on private rights-of-way, and these routes are often adjacent to railway rights-of-way. Moreover, it is impracticable to change certain main communication routes when these are established either by extensive existing construction or by service requirements. However, where alternative routes for either class of circuit are available, these should be considered, together with other possible methods of coordination.


C.

2001

7.

Deferred General Coordination: While railway electrical supply facilities or communication facilities not concerned or likely to be concerned in the near future in situations requiring inductive coordination should usually conform to general coordinated methods, either of these facilities, pending the incoming or development of the other, may, if deemed economically advantageous, occupy locations or use types of construction and operating methods other than those conforming to general coordinated methods. However, non-coordinated facilities should be altered when and as necessary to conform to such methods upon the incoming or development of the other facilities conforming to general coordinated methods. Where, however, all things considered, specific coordinated methods will be sufficient and more economical than general coordinated methods in any particular case, specific coordinated methods may be applied.

8.

Special Methods of Coordination: Where the inductive coordination of railway electrical supply facilities and communication facilities cannot be technically or economically established under the methods of coordination covered by these Principles, cooperative consideration should be given to determine what special methods should be employed.

Practices - Introductory 1. These recommended Practices supplement and are in accord with the Principles. They are based on experience and cooperative investigation and are intended to indicate methods that should be considered in the inductive coordination of railway electrical supply facilities and communication facilities. Quantitative discussions are not included since the application of the Practices in specific cases will depend upon the particular circumstances in each case and the existing state of the art. 2.

It is recognized that in the growth and development of the railways and communications and as the art progresses, other mutually satisfactory methods of coordination will doubtless be devised. The fact that such other methods are not included herein does not preclude their use, nor their later incorporation in these Practices as they may be agreed upon.

3.

Electrified railways generally use the traffic rails to carry power current and, since these rails are not effectively insulated from ground, a portion of this current flows in the ground. The treatment of the


Part 20.1.4 problem of inductive coordination involving such electrified railways differs in many respects from that usually given to supply circuits in which normally the power current is substantially confined to conductors that are insulated from ground. It has been found advisable, therefore, to divide the subject matter on railway electrical supply facilities into two sections, namely, "Practices Applicable to Transmission and Distribution Circuits and Associated Equipment" (Section F) and "Practices Applicable to Rail-Return Circuits and Associated Equipment" (Section G). 4.

D.

In order that the intent of the Principles may be carried out, the Practices herein designated as "General Coordinated Methods" should be applied to all railway electrical supply facilities and commercial communication facilities except as deviations may be made under the principle of "Deferred General Coordination" (Paragraph B-7 of Principles). In cases of inductive exposure where these general coordinated methods are insufficient, such of the Practices herein designated, as "Specific Coordinated Methods" (Paragraphs E-2, F-2 and G-2) should also be applied, as they will provide the best engineering solution. In determining what specific coordinated methods should be applied in such cases, consideration of the railway communication facilities should be included.

Mutually Applicable Practices 1. Notice and Cooperation: Arrangements should be set up between railway and communication companies operating in the same general territory providing for notice, as far in advance as practicable, of any construction, changes in construction or changes in operating conditions of their facilities, which are concerned or are likely to be concerned in situations requiring inductive coordination. These arrangements should include a list of items regarding which each company will give advance notice to the other company and should specify the territory included in each such arrangement. For each such territory each company should designate an official to receive and send advance notices and should adopt such routines within their respective organizations as will provide for the proper forwarding of advance notices and the prompt handling of notices that are received. An illustrative arrangement between a railway company and a commercial communication company is shown in Appendix A. Where situations arise which in the opinion of either company require inductive coordination, the railway and communication companies should cooperate in determining


2001

and carrying out those methods which provide the best engineering solution in each case and to this end there should be complete interchange of pertinent information. 2.

Operating Instructions: Railway companies should adopt operating instructions that outline the procedure to be followed when abnormal operating or fault conditions exist. Communication companies should adopt operating instructions specifically outlining the procedure for notification of Railways when inductive disturbances arise on their communication circuits that appear to be due to the influence of Railway electrical supply facilities. If abnormal operating conditions on railway electrical supply facilities should temporarily prevent the use of certain communication facilities, and these effects can be avoided only by rerouting the traffic or rearranging the facilities of one or both companies, t consideration should be given to such arrangements as will give the best overall results.

3.

Records: Railway companies should keep operating records of their electrical supply facilities and communication companies should keep a record of disturbances on their communication facilities so that a study of such disturbances as appear to be due to conditions on the railway will be facilitated.

4.

Limitation of Influence and Susceptiveness: In deg, specifying or otherwise determining the character, location, construction, and arrangement of railway electrical supply facilities or commercial communication facilities, or the character, quality, arrangement, and suitability of materials or apparatus making up these facilities, and in operating and maintaining these facilities, all factors which would contribute to inductive influence or inductive susceptiveness should be limited as far as necessary and practicable. The mechanical and electrical design and construction of railway electrical supply facilities and commercial communication facilities should conform to good modern practice.

5.

Coupling: Efforts should be made to arrange railway electrical supply facilities and commercial communication facilities so as to minimize the coupling between them.


E.

Part 20.1.4 a.

While coupling may be reduced by increasing the separation in sections of the exposure, other methods of coordination should be considered along with this method and those arrangements adopted which, in combination, will give the best engineering solution. In the consideration of separation as a means of reducing coupling, future service requirements and premanency of location should be included.

b.

Where communication facilities and railway electrical supply facilities are located in proximity to each other, cooperative consideration should be given to the relative locations of grounds with a view to limiting coupling.

6.

Changes in Systems or Methods of Operation: In changing systems or methods of operation, precaution should be taken to avoid increasing, and an effort made to decrease the inductive influence or inductive susceptiveness. If any condition develops which increases these factors, an effort should be made promptly to remedy such condition.

7.

Maintenance: Railway electrical supply facilities and communication facilities should be maintained in good condition. Repairs and renewals should be made promptly.

Practices Applicable to Communication Facilities 1. General Coordinated Methods: The following practices should be applied to all commercial communication facilities except as deviations may be made under the principle of "Deferred General Coordination" (Paragraph B-7 of Principles). a.

Protection: Protective devices should be so designed, constructed, installed and maintained as not to cause unavoidable unbalances or interruptions of communication circuits.

b.

Inspection: Routine inspections and tests should be made with a view to maintaining electrical balance and efficiency of communication facilities.

c.

Discontinuities: Discontinuities should be limited to the number required by the conditions to be met.

d.

Lines: In order to minimize line unbalances, the resistance, inductance, capacitance and leakage


2001 conductance of one side of a circuit in each section thereof, should be as nearly equal respectively to the corresponding quantities in the other side of the same section of the circuit as is necessary and practicable. Some of the methods that should be followed for the purpose of limiting the unbalance in lines are as follows: 1)

Transpositions: The capacitances to earth of the two sides of a metallic circuit on an open-wire line should be suitably balanced by transpositions. Before a metallic circuit is placed in service, a check should be made to insure that the transpositions are correctly located and properly installed.

2)

Derived Circuits: In the creation of circuits from one or more circuits without adding line conductors, due regard should be given to avoiding unnecessary increases in inductive susceptivness.

3)

a)

Phantom circuits should be created only from similar adjacent pairs. Branches connected to one side only of a phantom circuit should be avoided unless connected through repeating coils.

b)

If one side circuit of a phantom group is loaded for voice frequencies, the other side circuit should be similarly loaded at the same loading points, such loading to have closely the same electrical characteristics.

c)

In general, phantom circuits should be used only for toll or trunk circuits, except in cases of long rural circuits.

Connections: Efforts should be made to prevent the introduction of unbalance by resistance. a)

In toll cable conductors, all ts should be made in accordance with good practice for the conditions concerned. In open-wire toll conductors, all ts should be made with sleeves or should be well soldered or welded.

b)

All wires should be properly cleaned before the ts are made to insure


Part 20.1.4 good . c)

4)

e.

2.

All test connections, terminal boxes and associated wiring should be designed, constructed, installed and maintained so as to avoid circuit unbalances as far as practicable.

Use of Cable: Consideration should be given to fiber optics or placing circuits in cable at the time of rebuilding open wire lines.

Apparatus: All apparatus connected to a communication circuit should be so designed, constructed, installed and maintained as to minimize, within practical limits, the unbalances of the series impedance and ittance to ground of the two sides of the circuit.

Specific Coordinated Methods: The specific practices which follow are to be used in addition to the general practices to supplement the latter, in so far as may be necessary and practicable, in cases where railway electrical supply facilities and commercial communication facilities are involved or are about to be involved in situations requiring inductive coordination. a.

It is not intended that all of these practices should be applied in any specific case, but in each instance that practice or those practices should be selected which, in combination with the methods that are to be applied to the railway electrical supply facilities, will afford the best engineering solution.

b.

Special Devices: Consideration should be given to the use of special devices, such as neutralizing transformers, sectionalizing transformers, filters, resonant shunts, drainage, special protective devices, acoustic shock reducers, etc., in any case where they may offer benefit, and where service requirements permit.

c.

Lines 1) Configuration: Where service requirements permit a choice of configuration of a communication circuit or a group of communication circuits, consideration should be given to the selection of a configuration such as to limit inductive susceptiveness.


2001 2)

Shielding: Where an open-wire line is involved in an inductive exposure, consideration should be given to the use of methods of shielding in order to reduce inductive effects. This should include consideration of replacement of the open-wire line by aerial or underground cable or fiber within the exposure. Where communication circuits are carried in cable, consideration should be given to the use of properly arranged and installed grounds on cable sheaths, or other methods of shielding.

3)

d.

Coordinated Transpositions: Consideration should be given to the use of arrangements of transpositions in open-wire lines involved in inductive exposures, to reduce coupling. Such transpositions should be located at suitable intervals consistent with the discontinuities of the exposure and the locations of transpositions in the paralleling Railway electrical supply lines.

Apparatus 1) Party Line Stations: Consideration should be given to improving the electrical balance of party line stations where noise frequency effects are involved. Where low frequency effects are involved, consideration should be given to biasing ringers, the use of relay sets, or other available methods. 2)

Central Office Equipment: Where a toll circuit may be switched to another toll circuit or to a subscriber's circuit, consideration should be given to the use of repeating coils or other apparatus which will adequately limit the inductive susceptiveness. Where series apparatus is applied to local communication circuits, consideration should be given to arranging it so that equal impedances are inserted in each side of the circuit where necessary and practicable.

3)

Ground Connections: Ground connections, if employed on equipment connected to


Part 20.1.4 communication circuits, should, when practicable, be at neutral or balanced points. e.

Records: A detailed record should be kept of disturbances in communication circuits involved in inductive exposures where a study is advisable. Such records should as fully as practicable include date, time, duration, circuit designation, location, nature, effects and probable cause of the disturbances, and the method and time of clearing the circuits. All of the above records, or a convenient summary thereof, should be available for the purpose of analyzing causes and effects of disturbances.

F.

Practices Applicable to Transmission and Distribution Circuits and Associated Equipment 1. General Coordinated Methods: The following practices should be applied to all transmission and distribution circuits and associated equipment except as deviation may be made under the principle of "Deferred General Coordination" (Paragraph B-7 of Principles). a.

Residual Voltages and Currents: Residual currents returning by remote paths, and residual voltages, should be limited as far as practicable.

b.

Unsymmetrical loads between phases, which would give rise to residual currents returning by remote paths, or to residual voltages, should be avoided as far as practicable.

c.

Discontinuities: Discontinuities should be limited to the number required by the conditions.

d.

Switching: In all switching operations care should be taken to limit the production of transient disturbances. Care should be taken to avoid repeatedly energizing, at normal voltage, a transmission or distribution circuit in order to locate or clear a fault.

e.

Connections: Care should be taken to avoid resistance that might increase inductive influence.

f.

Lines: In order to limit the residual currents and voltages arising from line unbalances, the


2001 resistance, inductance, capacitance and leakage conductance of each side in any section of a circuit should be as nearly equal as practicable to the respective corresponding quantities in any other side of the same section of the circuit. Some of the methods and means for limiting unbalance in lines are described below: 1)

Configuration: Where there is a choice between two or more configurations of open-wire lines, consideration should be given to the use of such configuration of a circuit or a group of circuits as will provide the superior balance.

2)

Transpositions: The capacitances to earth of the phase conductors of a circuit should be suitably balanced by transpositions, as far as necessary and practicable.

3)

Branch Circuits: Where branches employing less than the total number of phases are to be used, they should be so planned as not to give rise to excessive residual current returning by remote paths or to excessive residual voltages. This can be accomplished by limiting the length of such branch circuits and distributing them among the phases of the main circuit.

4)

Three-Phase Four-Wire Circuits with Multi-Grounded Neutral: On three-phase four-wire circuits with multi-grounded neutral, single-phase and open-wye loads should be limited in size and so distributed among the phases as to limit the unbalanced load current. Where energy is supplied to three-phase four-wire circuits with multi-grounded neutral from a delta-wye-connected transformer bank, consideration should be given to connecting the neutral of three-phase wye-delta-connected load transformer banks to the neutral wire.

5)

Overhead Ground Wires: Where overhead ground wires are to be installed on transmission or distribution lines, consideration should be given to such kind and size of wire as will, through shielding, reduce coupling as far as practicable.


Part 20.1.4 g.

Apparatus: 1) Rotating Machinery: Synchronous machines should be specified and selected so as to have a waveform in which the harmonic components are limited as far as practicable.

2)

a)

Where three-phase generators having grounded neutrals are to be connected either directly or through wye-wye-connected transformer banks to three-phase transmission or distribution circuits, means should be used to suppress triple harmonics as far as necessary and practicable. This may be accomplished in the design of the generators, or by the use of auxiliary equipment, or, where wye-wye transformer banks are used, by delta-connected tertiary windings on the transformers.

b)

Induction motors and generators should be specified and selected, the harmonic voltages and currents of which, as far as practicable, will not increase the inductive influence of the system to which they are connected.

Transformers: In order that the waveform of voltage and current may be affected as little as practicable by transformers, such apparatus should be so designed as not to require operation at excessive magnetic densities. In the installation, connection, and operation of transformers, care should be taken to avoid normal voltages in excess of rating, and excessive magnetizing currents. a)

Where a three-phase transmission or distribution circuit is connected directly to the wye-connected windings of transformers with grounded neutral, or to wye-connected auto-transformers with grounded neutral, low impedance closely coupled delta-connected windings, or other suitable means for adequately limiting the triple harmonic components of residual currents and voltages, should be employed.

b)

Care should be taken that the individual units in each bank of transformers, operated with a grounded neutral and


2001 connected to a three-phase transmission or distribution circuit, are substantially alike as to electrical characteristics and that they are similarly connected. 3)

Circuit Breakers: Each circuit breaker controlling the supply of energy to transmission or distribution circuits should have all of its poles arranged for gang operation. These circuit breakers should be automatic for short circuits between phases and from phase to ground, and should be of a type that will disconnect the faulty circuit in as short a time as practicable.

4)

Protective Apparatus: Protective apparatus should be such that it will not unnecessarily add to transient disturbances and should, as far as practicable, avoid or limit such transient disturbances.

5)

a)

Lightning arresters should be so adjusted as not to operate at small over-voltages.

b)

Lightning arresters that have been temporarily withdrawn from service should not be replaced in service until they are in proper operating condition.

c)

Where lightning arresters requiring periodic charging are used on a transmission or distribution circuit involved in an inductive exposure, they should be equipped with auxiliary resistances and s.

d)

Routine inspections and tests should be made to insure that adjustments in all protective apparatus are properly maintained.

Ground Connections: Ground connections, if employed on apparatus connected to transmission or distribution circuits, should be made at balanced or neutral points. This precludes the use of grounded single-phase loads and grounded open-wye transformer connections on three-phase systems. Consideration should be given to the use of


Part 20.1.4 current limiting impedance in neutral-to-ground connections of apparatus electrically connected to transmission or distribution circuits. 2.

Specific Coordinated Methods: The specific practices which follow are to be used in addition to the general practices to supplement the latter, in so far as may be necessary and practicable, in cases where transmission and distribution circuits and communication facilities are involved or are about to be involved in situations requiring inductive coordination. a.

It is not intended that all of these practices should be applied in any specific case, but in each instance that practice or those practices should be selected which, in combination with the methods that are to be applied to the communication facilities, will afford the best engineering solution.

b.

Lines: 1) Configuration: Where physical and economic conditions permit a choice of configuration of transmission or distribution circuits within inductive exposures, the configuration selected should be such as to limit the inductive influence most effectively. 2)

Branch Circuits: Consideration should be given to the isolation of branch circuits consisting of less than the total number of phases of the main circuit, by means of transformers, when such main or branch circuits are involved in inductive exposures.

3)

Coordinated Transpositions: Consideration should be given to the use of transpositions in transmission and distribution circuits, within inductive exposures, for the purpose of reducing coupling. Such transpositions should be located at suitable intervals, consistent with the discontinuities of the exposure and the locations of transpositions in the communication lines.

4)

Shielding: Consideration should be given to the installation of shield wires in inductive exposures. In order to obtain the full benefit of such shield wires they should be effectively grounded at the ends of the exposures and at intervals within the


2001 exposures. Where overhead ground wires are to be employed on transmission or distribution lines, consideration should be given to the use of such kind and size of wire as will, through shielding, reduce coupling as far as practicable; also to the effective grounding of these wires within and adjacent to the exposure and to the connection of these wires to the station grounds at power supply points where the neutrals of the transmission or distribution circuits concerned are grounded.

c.

Apparatus 1) Wave Shape: Where service conditions permit, consideration should be given to special means and devices for reducing the amplitude of harmonics on systems involved in inductive exposures. a)

Where a ground connection on the armature winding of an alternating current generator or motor, directly connected to a transmission or distribution circuit, results in triple harmonics on circuits involved in inductive exposure, means should be employed to reduce the triple harmonics as far as necessary and practicable.

b)

Where rectifiers, arc furnaces or other apparatus, distort the voltage or current waveform of a transmission or distribution circuit involved in an inductive exposure, consideration should be given to the use of suitable auxiliary apparatus or other means to limit such distortion.

2)

Lightning Arresters: Where disturbances arise at times of charging lightning arresters, notwithstanding compliance with Section F-1-7-d, every effort should be made to do the charging at times of minimum traffic load on the communication facilities concerned.

3)

Circuit Breakers: Consideration should be given to the installation of automatic circuit breakers or their equivalent to control the supply of energy to transmission


Part 20.1.4 or distribution circuits involved in inductive exposures. 4)

d.

Current Limiting Devices: Consideration should be given to the use of current limiting devices in either the line wires or the neutral-to-ground connection of transmission and distribution circuits, as far as necessary and practicable.

Records: Railway companies should keep detailed operating records of their transmission and distribution circuits which are involved in inductive exposures where a study of disturbances in the communication facilities concerned is advisable. Such records should, as fully as practicable, include date, time, duration, circuit designation, location, nature and cause of trouble, method and time of clearing the trouble and any special or abnormal operating conditions. All of the above records, or a convenient summary thereof, should be available for the purpose of analyzing cause and effect of disturbances on communication circuits.

G.

Practices Applicable to Rail-Return Circuits and Associated Equipment 1. General Coordinated Methods: The following practices should be applied to all rail-return circuits and associated equipment except as deviation may be made under the principle of "Deferred General Coordination" (Paragraph B-7 of Principles). a.

General Considerations: In the design, construction and maintenance of rail-return circuits and associated equipment, consideration should be given to facilities and methods of operation which will limit, as far as practicable, the inductive effects on neighboring communication facilities.

b.

Electrified Railways: Current. 1)

Single-Phase and Direct

Design of Network including Distribution of Current: In the design and arrangement of electrified railway circuits, consideration should be given to means of limiting the total ampere-miles in rail-return circuits on either side of any load or short circuit, and to equalizing the total ampere-miles on the


2001 two sides. Means for obtaining benefit in these respects exist, in the case of alternating current electrifications, in the proper proportioning of impedances among the transmission circuits (including the distribution feeder - conductor circuits of three-wire systems), the system of rail-return circuits and the substation transformers, and in the spacing of substations. Similar methods exist in the case of direct current electrifications. 2)

Limitation of Short Circuit Current: In the design and arrangement of alternating current electrified railway circuits, including the associated transmission and distribution system and the facilities which supply energy thereto, consideration should be given to means of limiting short circuit currents in rail-return circuits. On branch lines having a power demand that is light compared to that of the main system, it is often practicable to design the network so as to limit short circuit currents to a greater extent that can be done on the main system. On direct current electrifications, consideration should be given to the use of means of controlling the rate of change of short circuit currents on conductor systems.

3)

Conductor Systems: conductors should be so arranged that they can be sectionalized either normally or at times of abnormal conditions. a)

conductor systems not normally sectionalized, should be so arranged that they will be sectionalized automatically at times of fault or short circuit.

b)

Consideration should be given to the use of separate conductor feeders for connecting the conductor system associated with yard tracks to substation buses.

c)

Stub-end feed as a condition of normal operation should be avoided as far as


Part 20.1.4 practicable. Where this cannot be avoided its length should be limited. 4)

5)

Return Current: Consideration should be given to arrangements that will limit the amount of current that returns through the ground or remote metallic paths. a)

Rails should be bonded and cross-bonded in accordance with good modern practice.

b)

Where return feeders are to be employed, consideration should be given to locating them, with respect to paralleling electrical supply conductors, so as to minimize inductive influence as far as practicable.

c)

The method of connecting return feeders to rails and the spacing of such connections should be in conformity with good modern practice.

d)

Where conditions are such that return current may follow remote metallic paths, consideration should be given to methods of limiting the flow of the return current through such paths.

Rotating Machinery: Generators, frequency converters and motors used in alternating current railway electrifications should be designed so as to have a waveform in which harmonic components are limited. a)

Generators, motor-generator sets, synchronous converters and motors used in direct current railway electrifications should be designed so as to have a waveform in which alternating current ripples are limited.

b)

Where direct current generators, or the direct current sides of motor-generator sets or synchronous converters, are operated in series, those operated in each such series arrangement should be alike in capacity and design, and consideration should be given to arranging them so that in their operation the alternating current ripples will oppose each other.


2001 c)

6)

Where synchronous machines are used on the locomotives or cars operating on alternating current railway electrifications, consideration should be given to placing such machines in operation in a manner which will not cause excessive current surges over the conductor system.

Mercury Arc Rectifiers: Where mercury arc rectifiers are to be employed on direct current railway electrifications, consideration should be given to the use of rectifiers having as large a number of phases as practicable. Consideration should be given to the use of filters on the direct current side of mercury arc rectifiers to suppress harmonics.

7)

Transformers: In order that the waveform of voltage and current may be affected as little as possible by transformers, such apparatus should not be designed for operation at excessive magnetic densities. In the installation, connection and operation of transformers, care should be taken to avoid normal voltages in excess of rating, and excessive magnetizing currents.

8)

Circuit Breakers: Circuit breakers controlling the supply of energy to conductor systems should be automatic.

9)

a)

Consideration should be given to arranging circuit breakers controlling the energy supplied to any section of the conductor system so that, under fault conditions, they will operate as nearly simultaneously as practicable.

b)

High-speed circuit breakers should be considered for use in positions controlling the energy supplied to conductor systems.

Protective Apparatus: Protective apparatus should be such that it will not unnecessarily add to transient disturbances and will, as far as practicable, avoid or limit such transient disturbances.


Part 20.1.4

10)

c.

2.

a)

Lightning arresters should be so adjusted as not to operate at small over-voltages.

b)

Lightning arresters that have been temporarily withdrawn from service should not be replaced in service until they are in proper operating condition.

c)

Where lightning arresters requiring periodic charging are used on rail-return circuits involved in an inductive exposure, they should be equipped with auxiliary resistances and s.

d)

Routine inspections and tests should be made to ensure that adjustments on all protective apparatus are properly maintained.

Overhead Ground Wires: Where overhead ground wires are associated with railway electrical supply circuits carried on or near an electrified railway, consideration should be given to connecting such ground wires to the traffic rails so that they may serve as part of the return feeder system. In connecting such ground wires to the traffic rails, due consideration should be given to the requirements of the signal system within the territory involved.

Other Rail-Return Circuits: Where rail-return circuits or associated equipment, other than for single-phase and direct current electrified railways, require inductive coordination with commercial communication facilities, those of the above methods that apply, should be followed in the design, construction and maintenance of the facilities concerned.

Specific Coordinated Methods: The specific practices which follow are to be used in addition to the general practices to supplement the latter, in so far as may be necessary and practicable, in cases where rail-return circuits and commercial communication facilities are involved, or are about to be involved, in situations requiring inductive coordination. a. It is not intended that all of these practices should be applied in any specific case, but in each instance that practice or those practices


2001 should be selected which, in combination with the methods that are to be applied to the commercial communication facilities, will afford the best engineering solution.

b.

Electrified Railways including Single-Phase and Direct Current 1) Conductor Systems: Consideration should be given to specific arrangements of conductor systems so as to reduce inductive influence.

2)

a)

Where, because of local conditions, certain locations and spacings of substations will materially reduce inductive influence, consideration should be given to such locations and spacings.

b)

Where operation with conductors sectionalized at substations, or at other points, will materially reduce inductive influence, consideration should be given to such method of operation.

c)

Where, because of local conditions, stub-end feeds are used, consideration should be given to means of limiting currents to short circuits on such stub-end feeds.

Return Current: Consideration should be given to the use of return feeders or additional return feeders where a reduction in the amount of current returning through ground or remote metallic paths is desirable. a)

Where leakage to earth from the conductors that connect traffic rails to return feeders and negative buses contributes to inductive influence, consideration should be given to insulating these conductors from ground.

b)

Where material reduction of inductive influence can be obtained by the use of conductor feeders combined with closely coupled return feeders, the use of such arrangements should be considered.


Part 20.1.4 c)

Consideration should be given to the use of booster transformers in alternating current railway electrifications.

c.

Circuit Breakers: Consideration should be given to the use of high-speed circuit breakers for controlling the energy supplied to each substation section of the conductor system. In cases of multi-track installations, this should include consideration of individual breakers in each conductor feeder, as well as the alternative in which a single circuit breaker may control the energy supplied to a group of conductors.

d.

Lightning Arresters: Where disturbances arise at times of charging lightning arresters, notwithstanding compliance with Section G-1-2-i, every effort should be made to do the charging at times of minimum traffic load on the communication facilities affected.

e.

Potential-Neutralizing Conductors: Where potential-neutralizing conductors would contribute to the reduction of inductive influence, their use should be considered.

f.

Special Devices: Filters, resonant shunts or other devices to suppress alternating current ripples from rectifiers, generators, motor-generator sets, synchronous converters or motors used in direct current railway electrifications, should be employed as far as necessary and practicable. Where mercury arc rectifiers are to be used in direct current railway electrifications, consideration should be given to the use of special means or devices to prevent or limit wave shape distortion on the alternating current supply system, as far as necessary and practicable.

g.

Overhead Ground Wires: Where overhead ground wires are to be used in connection with railway electrical supply circuits carried alongside or near the railway, consideration should be given to making them of low resistance and connecting them to the traffic rails so that they will serve as part of the return feeder system. In connecting such ground wires to the traffic rails, due consideration should be given to the requirements of the signal system within the territory


2001 involved.

h.

Records: Railway companies should keep detailed records of their electrical supply facilities involved in inductive exposures, where a study of disturbances in the communication facilities concerned is advisable. Such records should, as fully as practicable, include date, time, duration, circuit designation, location, nature and cause of trouble, method and time of clearing the trouble, and any abnormal operating conditions. All of the above records, or a convenient summary thereof, should be available for the purpose of analyzing cause and effect of disturbances on the communication circuits.

i.

Other Rail-Return Circuits: Where rail-return circuits or associated equipment, other than for single-phase or direct current electrified railways, require inductive coordination with commercial communication facilities, such of the above specific methods as apply should be followed in the design, construction and maintenance of the facilities concerned.

Appendix A Cooperation and Notice Illustrative Arrangement Between a Railway Company and a Communication Company The purpose of this Appendix is to illustrate an arrangement for cooperation and advance notice, in accordance with the Principles and Practices, between a Railway Company and Communication Companies operating in the same territory. In any specific case the details may differ from the illustration, although the items covered should ordinarily be included. Cooperative Arrangements - Inductive Coordination The Railway Company The Communication Company 1.

General: This memorandum covers arrangements for cooperation and advance notice between the________________ Communication Company Railway and the where inductive coordination is involved.

2.

Cooperation: All situations requiring inductive coordination will be handled in accordance with the


Part 20.1.4 Principles and Practices for the inductive coordination of railway electrical supply facilities and commercial communication facilities.

3.

Exchange of Advance Notice: A. Territory and Representation 1. For the area traversed by the __________________ Railway in the States of , advance notice of any construction and other information connected with the coordination of the Railway electrical supply facilities and the communication facilities of will be forwarded by the Railway Company to Mr. , General Plant Manager* of the Communication Company and by the Communication Company to Mr. , Superintendent of Communication* of the Railway Company. (*This will vary with the organization of the company concerned.) B.

Advance Notice: 1. Items to be Reported: Whenever any of the following items of work are planned, a notice will be sent to the designated representative of the other company as far in advance as practicable of actual construction or the making of commitments:

2.

a.

Construction of new facilities that will be or are likely to be concerned in situations requiring inductive coordination.

b.

Relocation or rearrangement of facilities that will change the separation or length of existing inductive exposures.

c.

Reconstruction or rearrangement of facilities, located on or near railway rights-of-way, which will require or may require inductive coordination.

d.

Changes in facilities or methods of operation that will appreciably affect inductive susceptiveness or inductive influence, where such facilities are involved in situations in which consideration must be given to inductive coordination.

Form of Advance Notice: Advance notices will be sent by letter and will


2001 include the following:

4.

a.

Location and brief description of proposed work.

b.

Estimated starting and completion dates.

c.

With whom the inductive coordination matters involved should be taken up in the company in whose plant the work is proposed.

Action to be Taken Upon Receipt of Advance Notice: The representative of the company receiving advance notice will proceed as follows: a. See that the notice is promptly brought to the attention of the people who are concerned in his company and associated companies. b.

Ascertain if his company, or associated companies, plan any work which may be affected by the proposed work.

c.

Write to the representative of the company sending the notice, advising as to his views with regard to the desirability of further t study, and as to who will represent his company and associated companies in connection with these matters.

d.

Arrange for representatives of his company or associated companies to get in touch with the proper representatives of the other company.

5.

Coordination for Existing Situations: Where the circumstances are such as to make it advisable to give t consideration to coordination for existing situations, the designated representatives of the railway and telephone companies will make such arrangements for action or further study as may be required by the facts in each specific case.

6.

Special Arrangements: This section should include any further and detailed arrangements that the railway and communication companies desire to make.


Part 20.1.6

Recommended Principles and Practices for Inductive Coordination of Electrical Supply and Communication Systems Report of the t Engineering Subcommittee of the Association of American Railroads and the Edison Electric Institute; and the Association of American Railroads & Electrical Power Research Institute Revised 1994 (18 Pages) A-1

A-2

A-Introduction Member companies of the Association of American Railroads and member companies of the Edison Electric Institute have found that their respective wire systems frequently require inductive coordination. Railroad companies operate communication circuits in connection with the movement of trains and the general conduct of their business. In some instances they also operate supply circuits for electrical propulsion of trains and for supplying energy to signals, shops and stations along the rights-of-way. Electric light and power companies operate supply circuits for the transmission and distribution of electrical energy to consumers both large and small throughout the territory they serve. In some instances they also operate communication circuits in connection with their supply systems and in the general conduct of their business. The characteristics of the systems, as well as their physical relations introduce problems of a character that make apparent that cooperative study and the adoption of specific arrangements would make possible the most satisfactory solution of these problems as they may arise. The Engineering Subcommittee has, therefore, prepared the following: 1. Principles for the inductive coordination of railroad and electric light and power supply and communication facilities to provide for the best engineering solution in each situation. 2.

A-3

Practices for the inductive coordination of railroad and electric light and power supply and communication facilities covering the general and specific methods of coordination that may be employed, based on the present state of the art.

In accordance with its understanding of the desires of the t General Committee, the Engineering Subcommittee has approached this problem in the broadest possible spirit of cooperation, recognizing that the orderly working out of mutual problems in accordance with the best engineering solution, by the organizations concerned, is to their best interest and in the best public interest.


1994

A-4

It should be pointed out that the Principles and Practices do not deal with the allocation of costs or with the physical coordination of the respective systems except in so far as the physical relations effect inductive coordination.

A-5

These Principles and Practices are intended to apply to all new installations, extensions and reconstructions and to the maintenance, operation and changes of all railroad or electric light and power wire systems where inductive coordination may be required now or later to prevent interference with the rendering or providing the railroad or electric light and power services.

A-6

The major problem is the coordination of electric supply facilities, and telephone and telegraph facilities. It is recognized, however, that some coordination of supply facilities and signal facilities may be required. All the Principles and many of the Practices apply to all types of communication facilities. It is to be understood, therefore, that wherever the term "communication facilities" is used, it includes signal facilities in so far as the Principles are concerned, and in such of the Practices as may be applicable.

B-1

B-2

B-Principles Duty of Coordination: In order to meet the reasonable service needs of the public, all railroad and electric light and power wire systems with their associated apparatus should be designed, located, constructed, operated and maintained in conformity with general coordinative methods. Where the general coordinative methods are insufficient, such specific coordinative methods as are suited to the situation should be applied to one or more of the facilities so as to provide the best engineering solution. The methods of inductive coordination should include the limiting of the inductive influence of the supply system, of the inductive susceptiveness of the communication system, or such combination of these as will most conveniently and economically provide satisfactory coordination, the methods to be based on the knowledge of the art. Cooperation: In order that full benefit may be derived from these Principles and in order to facilitate their proper application, railroad and electric light and power companies between whose facilities inductive coordination may now or later be necessary, should cooperate along the following lines: 1.

Railroad and electric light and power companies operating in the same general territory should give each to the other advance notice of any construction, reconstruction or change in operating conditions of its


Part 20.1.6 facilities which are concerned or likely to be concerned in situations requiring inductive coordination. 2.

If it appears to either company that problems of inductive coordination requiring t consideration are involved, the companies should confer and cooperate to secure inductive coordination in accordance with the Principles set forth herein.

3.

To assist in promoting conformity with these Principles, an arrangement should be set up between the railroad and the electric light and power companies whose facilities occupy the same general territory, for the interchange of pertinent data and information, including that relative to existing and proposed construction and changes in operating conditions of facilities concerned or likely to be concerned in situations which require inductive coordination.

4.

A computer software program (CORRIDOR) is available through AAR or Electrical Power Research Institute (EPRI) and will enable railroad communications and signal engineers to calculate overhead transmission line coupling to ive conductors. The CORRIDOR module enable railroad communications and signal engineers to readily determine the induced voltage and current in conductors that parallel one or more power lines. Input data can include common occurrences such as multiple power lines, segmented or multigrounded static wires, counterpoises, rail or pipeline insulators, relay impedances, ballast unbalance, bonds between pipelines or other conductors, cathodic protection anodes, and pipeline-coating and soil-resistivity changes along the length of the corridor. Most importantly the CORRIDOR module s for the shielding or interactive effects (mutual coupling) of the various paralleling conductors of the sharing utilities, and it predicts the voltage and current coupled to the ive conductors at defined locations along the corridor.

B-3

Choice of Specific Coordinative Methods: When specific coordinative methods are necessary and there is a choice of such methods, those that provide the best engineering solution should be adopted. 1.

The specific methods selected should be such as to meet the service requirements of both systems in the most convenient and economical manner without regard to whether they apply to the railroad or electric light


1994

and power facilities or to both.

B-4

2.

In determining which specific methods are most convenient and economical in any situation, all factors for all facilities concerned should be taken into consideration, including present factors and those which can reasonably be foreseen.

3.

Neither party should assume to be the judge of the service requirements of the other system, or of what constitutes good practice in that system.

Inductive Coordination for Existing Situations: Railroad and electric light and power companies should exercise due diligence in applying coordinative methods to existing situations in accordance with these Principles. When railroad or electric light and power facilities are generally reconstructed, rearranged, or extended, the new or changed parts should be brought into conformity with these Principles.

B-5

Systematic Fundamental Planning: The principles of advance notice and cooperation are not limited in application to instances of new construction or reconstruction presently to be undertaken, but should be applied also in connection with preparation of fundamental or systematic plans for future extension and improvement of their systems. The application of these principles, in cases of the latter class, should be made sufficiently early to ensure that fundamental plans for future developments will encounter no serious difficulties of coordination that can reasonably be foreseen.

B-6

Coordinated Location for Lines: The utilization of generally paralleling rights-of-way is often essential to the economical and efficient extension, operation and maintenance of railroad and electric light and power facilities. 1.

Each utility recognizes the right of the other to place, as necessity requires, circuits of any modern and efficient type on any highway, provided the location and type of construction are such as to coordinate reasonably with modern and efficient circuits of the other utility.

2.

Each utility recognizes the right of the other to operate lines of modern and efficient type along private rights-of-way free from substantial interference to service resulting from the construction, maintenance or operation of paralleling lines of the other utility. Each utility its,


Part 20.1.6 however, the right of the other utility to construct lines paralleling its private rights-of-way, provided it is practicable to coordinate the respective systems in such a manner that they can be maintained and operated without causing substantial interference to the service of either utility. 3.

Railroad circuits are, as a rule, located along railroad rights-of-way as it is usually impracticable to locate these circuits elsewhere. In order to provide adequate service, electric light and power circuits are located along streets, highways, and on private rights-of-way, and these routes are often adjacent to railroad rights-of-way. Moreover, it is impracticable to change the routes of certain electric light and power circuits when these are established either by extensive existing construction or by service requirements. However, where alternative routes for either class of circuit are available, these should be considered, together with other possible methods of coordination.

B-7

Deferred General Coordination: While railroad facilities or electric light and power facilities not concerned or likely to be concerned in the near future in situations requiring inductive coordination should usually conform to general coordinative methods, either of these facilities, pending the incoming or development of the other, may, if deemed economically advantageous, occupy locations or use types of construction and operating methods other than those conforming to general coordinative methods. However, non-coordinated facilities should be altered when and as necessary to conform to such methods upon the incoming or development of the other facilities conforming to general coordinative methods. Where, however, all things considered, specific coordinative methods will be sufficient and more economical than general coordinative methods in any particular case, specific coordinative methods may be applied.

B-8

Special Methods of Coordination: Where the inductive coordination of railroad facilities and electric light and power facilities cannot be technically or economically established under the methods of coordination covered by these Principles, cooperative consideration should be given to determine what special methods should be employed.

C-1

C-Practices - Introductory These recommended Practices supplement and are in accord with the Principles. They are based on experience and cooperative investigation and are intended to indicate methods that should be considered in the inductive


1994

coordination of supply facilities and communication facilities. Quantitative discussions are not included since the application of the Practices in specific cases will depend upon the particular circumstances in each case and the existing state of the art. C-2

Electrified railroads generally use the traffic rails to carry power current and since these rails are not effectively insulated from ground, a portion of this current flows in the ground. The treatment of the problem of inductive coordination involving such electrified railroads differs in many respects from that usually given to other types of supply circuits. In the design, construction and maintenance of rail-return circuits and associated equipment, consideration should be given to facilities and methods of operation which will limit, as far as practicable, the inductive effects on neighboring communication facilities. The coordination of these circuits with the communication circuits of the railroad and of commercial communication companies presents the major problem. Since in practically every case the measures adopted to provide this coordination will be adequate to take care of any communication facilities of electric light and power companies, no detailed practices have been prepared for these circuits.

C-3

It is recognized that in the growth and development of the railroad and electric light and power industries and as the art progresses, other mutually satisfactory methods of coordination will doubtless be devised. The fact that such other methods are not included herein does not preclude their use, nor their later incorporation in these Practices as they may be agreed upon.

C-4

In order that the intend of the Principles may be carried out, the Practices herein designated as "General Coordinative Methods" should be applied to all supply facilities and communication facilities except as deviations may be made under the principle of "Deferred General Coordination." In cases of inductive exposure, where these general coordinative methods are insufficient, such of the Practices herein designated as "Specific Coordinative Methods," should also be applied as will provide the best engineering solution.

D-1

D-Mutally Applicable Practices Notice and Cooperation: Arrangements should be set up between railroad and electric light and power companies operating in the same general territory providing for notice, as far in advance as practicable, of any construction, changes in construction or changes in operating conditions of their facilities, which are


Part 20.1.6 concerned or are likely to be concerned in situations requiring inductive coordination. These arrangements should include a list of items regarding which each company will give advance notice to the other company and should specify the territory included in each such arrangement. For each such territory each company should designate an office to receive and send advance notices and should adopt such routines within its organization as will provide for the proper forwarding of advance notices and the prompt handling of notices that are received. (An illustrative arrangement between a railroad company and an electric light and power company is shown in Appendix A.)

D-2

Where situations arise which in the opinion of either company require inductive coordination, the railroad and electric light and power companies should cooperate in determining and carrying out those methods which provide the best engineering solution in each case and to this end there should be complete interchange of pertinent information.

D-3

Operating Instructions: Companies operating supply circuits should adopt instructions that outline the procedure to be followed when abnormal operating or fault conditions exist. Companies operating communication circuits should adopt instructions that outline the procedure for notification of a company operating a neighboring supply system when inductive disturbances arise on communication circuits that appear to be due to the influence of that supply system.

D-4

If abnormal operating conditions on supply facilities of one company should temporarily prevent the use of certain communication facilities of the other, and these effects can be avoided only by rerouting the services or rearranging the facilities of one or both companies, t consideration should be given to such arrangements as will give the best overall results from the standpoint of the public.

D-5

Records: In order to facilitate a study of disturbances on the communication facilities of one company which appear to be due to conditions on the supply facilities of another company, each company should keep operating records of its own supply facilities as well as records of disturbances on its communication facilities.

D-6

Limitation of Influence and Susceptiveness: In deg, specifying or otherwise determining the character, location, construction, and arrangement of supply facilities or communication facilities, or the character, quality, arrangement, and suitability of materials or apparatus making up these facilities, and in operating and maintaining these facilities, all factors which would contribute to inductive influence or inductive susceptiveness should be


1994

limited as far as necessary and practicable. D-7

The mechanical and electrical design and construction of supply facilities and communication facilities should conform to good modern practice.

D-8

Coupling: Efforts should be made to arrange supply facilities and communication facilities so as to minimize the coupling between them.

D-9

While coupling may be reduced by increasing the separation in sections of the exposure, other methods of coordination should be considered along with this method and those arrangements adopted which, in combination, will give the best engineering solution. In the consideration of separation as a means of reducing coupling, future service requirements and permanency of location should be included.

D-10 Where communication facilities of one company and supply facilities of the other company are located in proximity to each other, cooperative consideration should be given to the relative locations of ground connections with a view to limiting coupling. D-11 Changes in Systems or Methods of Operation: In changing systems or methods of operation, precaution should be taken to avoid increasing, and an effort made toward decreasing, the inductive influence or inductive susceptiveness. If any condition develops which increases these factors, an effort should be made promptly to remedy the situation as far as necessary and practicable. D-12 Maintenance: Supply facilities and communication facilities should be maintained in good condition. Repairs and renewals should be made promptly. E-1

E-Practices Applicable to Communication Facilities General Coordinative Methods: The following practices should be applied to communication facilities except as deviations may be made under the principle of "Deferred General Coordination."

E-2

Protection: Protective devices should be so designed, constructed, installed and maintained as not to cause unnecessary unbalances or interruptions of communication circuits.

E-3

Inspection: Routine inspections and tests should be made with a view to maintaining electrical balance and efficiency of communication facilities.

E-4

Discontinuities:

Discontinuities should be limited to the


Part 20.1.6 number required by the conditions to be met.

E-5

Insulation Resistance: The insulation resistance of communication circuits should be as high as is necessary and practicable.

E-6

Cable plant should be so designed, constructed and maintained as to ensure a high insulation of working conductors.

E-7

Conductor Spacing: In order to avoid increasing the interaction between grounded telegraph circuits, pin spacings less than those normally employed in communication practice should be avoided.

E-8

Excessive spacing of the conductors of metallic circuits should be avoided. This, however, does not mean that the spacing should be less than that required by considerations of safety and service.

F-1

F-2

F-Practices Applicable to Supply Circuits and Associated Equipment General Coordinative Methods: The following practices should be applied to all supply circuits and associated equipment (not including rail return circuits) except as deviation may be made under the principle of "Deferred General Coordination." Residual Voltages and Currents: Residual currents returning in the earth or by remote metallic paths, and residual voltages, should be limited as far as practicable. Unsymmetrical loads between phases, which would give rise to such residual currents or voltages should be avoided as far as practicable.

F-3

Discontinuities: Discontinuities should be limited to the number required by the conditions to be met.

F-4

Switching: In all switching operations care should be taken to limit the production of transient disturbances. Care should be taken to avoid reenergizing a faulted circuit at normal voltage an excessive number of times even if done in order to locate or clear the fault.

F-5

Connections: Care should be taken to avoid resistance that might increase inductive influence.

F-6

Balance of Lines: In order to limit the residual currents and voltages arising from line unbalances, the resistance,


1994

inductance, capacitance and leakage conductance of each side of a circuit in any section thereof should be as nearly equal as practicable to the corresponding quantities in any other side in the same section. Some of the methods and means for limiting unbalance in lines are described as follows:

F-7

1.

Configuration: Where there is a choice between two or more configurations of open-wire lines, consideration should be given to the use of such configuration of a circuit or a group of circuits as will provide the superior balance.

2.

Phase Arrangement (Interconnection): Certain phase arrangements of multiple circuit lines that are especially effective in reducing the inductive influence should where practicable, be employed.

3.

Transpositions: The capacitances and inductances of the phase conductors of a circuit should be suitably balanced by transpositions, as far as necessary and practicable.

4.

Branch Circuits: Where branches employing less than the total number of phases are to be used, they should be so planned as not to give rise to excessive residual current returning in the earth or by remote metallic paths, or to excessive residual voltages. Limiting the length of such branch circuits and distributing them among the phases of the main circuit will aid in accomplishing this result.

Three-Phase Four-Wire Circuits with Multi-Grounded Neutral: On three-phase four-wire circuits with multi-grounded neutral, single phase and open-wye loads should be limited in size and distributed among the phases to limit as far as necessary and practical the unbalanced load current. Where energy is supplied to three-phase four-wire circuits with multi-grounded neutral from a delta-wye connected transformer bank, consideration should be given to connecting the neutral of three-phase wye-delta connected load transformer banks to the neutral wire in order to limit the flow of triple harmonic currents.

F-8

Overhead Ground Wires: Where overhead ground wires are to be installed on supply lines, consideration should be given to the utilization of such kind and size of wire as will aid in providing the most satisfactory coordination. Frequently those characteristics that are beneficial from a coordination standpoint during abnormal conditions on the


Part 20.1.6 supply line have adverse effects during normal operating periods. Therefore the relative importance of both normal and abnormal effects should be considered in each installation.

F-9

Rotating Machinery: Synchronous machines should be specified and selected so as to have a waveform in which the harmonic components are limited as far as necessary and practicable. Where three-phase generators having grounded neutrals are to be connected either directly or through wye-wye connected transformer banks to three-phase supply circuits, means should be used to suppress triple harmonics as far as necessary and practicable. Induction motors and generators should be selected so that, as far as practicable, their harmonic voltages and currents will not increase the inductive influence of the system to which they are connected.

F-10 Transformers: In order that the waveform of voltage and current may be affected as little as practicable by transformers, such apparatus should be designed as not to require operation at excessive magnetic densities. In the installation, connection and operation of transformers, care should be taken to avoid normal voltages in excess of rating, and excessive magnetizing currents. 1.

Where a three-phase supply circuit is connected to wye-wye connected transformers with grounded neutral, or to wye-connected auto-transformers with grounded neutral, low impedance closely coupled delta-connected windings, or other suitable means for adequately limiting the triple harmonic components of residual currents and voltages should be employed.

2.

Care should be taken that the individual units in each bank of transformers, operated with a grounded neutral and connected to a three-phase supply circuit, are substantially alike as to electrical characteristics and that they are similarly connected.

F-11 Circuit Breakers: Each circuit breaker controlling the supply of energy to transmission circuits should have all of its poles arranged for gang operation, except when arranged for rapid opening and reclosing of a single phase to clear a phase-to-ground flashover. These circuit breakers should be automatic for short circuits between phases and in the case of grounded-neutral systems from phase to ground. They should be of a type that will disconnect the faulty circuit in as short a time as practicable. F-12 Protective Apparatus:

Protective apparatus should be such


1994

that it will not unnecessarily add to transient disturbances and should, as far as practicable, avoid or limit such transient disturbances. 1.

Lightning arresters should be so designed and adjusted as not to operate at small over-voltages.

2.

Where lightning arresters requiring periodic charging are used on a supply circuit involved in an inductive exposure, they should be equipped with auxiliary resistances and s.

3.

Routine inspections and tests should be made to ensure that adjustments in all protective apparatus are properly maintained.

F-13 Ground Connections: Ground connections, if employed on apparatus connected to supply circuits, should so far as practical be made at balanced or neutral points. In singlephase extensions of multi-grounded neutral circuits one side of the circuit is still considered a neutral although it is not a balance point of the particular branch. 1.

Ground-return circuits or ground-return branches of multi-wire supply circuits should not be employed.

2.

Consideration should be given to the use of current limiting impedance in neutral-to-ground connections of apparatus electrically connected to supply circuits.

F-14 Specific Coordinative Methods: The specific practices which follow are to be used in addition to the general practices to supplement the latter, in so far as may be necessary and practicable, in cases where supply circuits and communication facilities are involved or are about to be involved in situations requiring inductive coordination. It is not intended that all of these practices should be applied in any specific case, but in each instance that practice or those practices should be selected which, in combination with the methods that are to be applied to the communication facilities, will afford the best engineering solution. F-15 Configuration: Where physical and economic conditions permit a choice of configuration of supply circuits within inductive exposures, the configuration selected should be such as to limit the inductive influence most effectively. F-16 Coordinated Transpositions: Consideration should be given to the use of transpositions in supply circuits, within inductive exposures, for the purpose of reducing coupling at


Part 20.1.6 noise frequencies. Such transpositions should be located at suitable intervals, consistent with the discontinuities of the exposure and the locations of transpositions in the communication circuits. Where normal induction at fundamental frequency is involved, consideration also should be given to the location of the transpositions so as to reduce coupling with overhead ground wires or shield wires within inductive exposures. In addition, consideration should be given to the location of existing transpositions so as to obtain the best overall results.

F-17 Wave Shape: Where necessary and where service conditions permit, consideration should be given to special means and devices for reducing the amplitude of harmonics on systems involved in inductive exposures. 1.

Where a ground connection on the armature winding of an alternating-current generator or motor, directly connected to a supply circuit, results in triple harmonics on circuits involved in inductive exposures, means should be employed as far as necessary and practicable to reduce the triple harmonics.

2.

Where rectifiers, arc furnaces or other apparatus, distort the voltage or current waveform of a supply circuit involved in an inductive exposure, consideration should be given to the use of suitable auxiliary apparatus or other means to limit such distortion as far as necessary and practicable.

F-18 This Section intentionally left blank F-19 Circuit Breakers: Consideration should be given to the installation of automatic circuit breakers or their equivalent to control the supply of energy to supply circuits involved in inductive exposures. Practice similar to that for transmission circuit is desirable for distribution circuits as far as coordination is concerned and should be applied to distribution circuits as far as necessary and practicable. F-20 Current Limiting Devices: Consideration should be given to the use of current limiting devices in either the line wires or the neutral-to-ground connection of supply circuits as far as necessary and practicable. F-21 Branch Circuits: Consideration should be given to the isolation of branch circuits consisting of less than the total number of phases of the main circuit, by means of transformers, when such main or branch circuits are involved in inductive exposures.


1994

F-22 Shielding: Consideration should be given to the installation of shield wires in inductive exposures. In order to obtain the full benefit of such shield wires they should be effectively grounded at the ends of the exposures and at intervals within the exposures. G-Explanation of For the purpose of these Principles and Practices, the following are used with meanings as given below: G-1

Abnormal Operating Conditions: Electrical operating conditions resulting when operating arrangements other than normal are established.

G-2

Communication Circuits: Circuits used for the electrical transmission of intelligence by wire, such as telephone, telegraph, signal relaying or control circuits.

G-3

Communication Facilities: associated apparatus.

G-4

Configuration: The geometrical arrangement in transverse section of any assemblage of generally parallel conductors including their sizes and their relative positions with respect to other conductors and to the earth.

G-5

Coordinated Transpositions: Transpositions which are installed, either in supply circuits or in communication circuits or in both, for the purpose of reducing coupling; and which are located effectively with respect to the discontinuities of the exposure and are so arranged that those in each circuit are located with due regard to those in the other circuit.

G-6

Coupling: The interrelation of neighboring circuits by electric or magnetic induction or both, or by conduction through a common earth path, or by combinations thereof.

G-7

Discontinuity: A point at which there is an abrupt change in the physical relations of supply circuits and communication circuits or in the electrical characteristics of either circuit. Transpositions, however, are not considered as discontinuities.

G-8

Fault Conditions: Conditions resulting when a fault to ground or a short-circuit occurs on a supply circuit.

G-9

General Coordinative Methods: Those methods reasonably available for general application to communication facilities or supply facilities that contribute to inductive coordination without specific consideration of the requirements of individual inductive exposures.

Communication circuits and their


Part 20.1.6

G-10 Inductive Coordination: The location, design, construction, operation and maintenance of communication facilities and supply facilities in conformity with harmoniously adjusted methods which will prevent inductive interference. Note: Inductive interference is an effect arising from the characteristics and inductive relations of communication facilities and supply facilities of such character and magnitude as would prevent the satisfactory and economical operation of the communication facilities if methods of inductive coordination were not applied. 1.

Inductive Exposure: A situation of proximity between supply facilities and communication facilities under such conditions that inductive coordination should be considered.

2.

Inductive Influence: Those characteristics of supply facilities that determine the character and intensity of the inductive field which they produce.

3.

Inductive Susceptibility: Those characteristics of communication facilities which determine, so far as such characteristics can determine, the extend to which such facilities are capable of being adversely affected in giving service, by a given inductive field.

G-11 Overhead Ground Wires: Wires installed on aerial lines and grounded at intervals, which are intended primarily to provide lightning protection for the supply circuits or to limit potential rise of structures in case of fault, or both. G-12 Supply Circuits: Circuits used for the electrical transmission of energy. G-13 Supply Facilities: apparatus.

Supply circuits and their associated

G-14 Residual Current: The vector sum of the currents in the phase conductors of a transmission or distribution circuit. G-15 Residual Voltage: The vector sum of the voltages to ground of the phase conductors of a transmission or distribution circuit. G-16 Shielding: An effect, due to the presence of grounded conductors or grounded conducting structures, which in general is a reduction in coupling between neighboring circuits. G-17 Shield Wires:

Wires that are installed primarily to provide


1994

reduction in coupling by shielding. G-18 Specific Coordinative Methods: Those additional methods applicable to specific situations, where general coordinative methods are inadequate. G-19 Transpositions: An interchange of position of conductors of a circuit between successive length.

APPENDIX A COOPERATION AND NOTICE Illustrative Arrangement Between a Railroad Company and an Electric Light and Power Company The purpose of this Appendix is to illustrate an arrangement for cooperation and advance notice, in accordance with the Principles and Practices, between a Railroad Company and an Electric Light and Power Company operating in the same territory. In any specific case the details may differ from the illustration, although the items covered should ordinarily be included. COOPERATIVE ARRANGEMENTS INDUCTIVE COORDINATION The The

Railroad Company Electric Light and Power Company

General This memorandum covers arrangements for cooperation and Railroad and the advance notice between the Electric Light and Power Company where inductive coordination is involved. Cooperation All situations requiring inductive coordination will be handled expeditiously in accordance with the Principles and Practices of the t General Committee of Association of American Railroads and the Edison Electric Institute. Territory and Representation For the area traversed by the Railroad in the States of advance notice of any construction and other information connected with the coordination of Railroad and Electric Light and Power supply and communication facilities will be forwarded by the Railroad Company to Mr. , Superintendent of Distribution* of the Electric Light and Power Company and by the Electric Light and Power Company to Mr.


Part 20.1.6 , Superintendent of Communication* of Railroad Company.

the

* This will vary with the organization of the company concerned. Items to be Reported: Whenever any of the following items of work are planned, a notice will be sent to the designated representative of the other company as far in advance as practicable of actual construction or the making of commitments: 1. Construction of new facilities that will be or are likely to be concerned in situations requiring inductive coordination. 2.

Relocation or rearrangement of facilities that will change the separation of length of existing inductive exposures.

3.

Reconstruction or rearrangement of facilities, located on or near railroad rights-of-way, which will require or may require inductive coordination.

4.

Changes in facilities or methods of operation that will appreciably affect inductive susceptiveness or inductive influence, where such facilities are involved in situations in which consideration must be given to inductive coordination.

Form of Advance Notice: Advance notices will be sent by letter and will include the following: 1. Location and brief description of proposed work. 2.

Estimated starting and completion dates.

3.

With whom the inductive coordination matters involved should be taken up in the company in whose plant the work is proposed.

Action to be Taken Upon Receipt of Advance Notice: The representative of the company receiving advance notice will proceed as follows: 1. See that the notice is promptly brought to the attention of the people who are concerned in his company and associated companies. 2.

Ascertain if his company, or associated companies, plan any work which may be affected by the proposed work.

3.

Write to the representative of the company sending the notice, advising as to his views with regard to the desirability of further t study, and as to who will


1994

represent his company and associated companies in connection with these matters. 4.

Arrange for representatives of his company or associated companies to get in touch with the proper representatives of the other company.

Coordination for Existing Situations: Where the circumstances are such as to make it advisable to give t consideration to coordination for existing situations, the designated representatives of the Railroad and Electric Light and Power companies will make such arrangements for action or further study as may be required by the facts in each specific case. Special Arrangements: (This section should include any further and detailed arrangements which the Railroad and Electric Light and Power companies desire to make.)


Part 20.1.7

Discussion of Fundamental Factors Involved in Inductive Coordination and of Remedial Measures Applicable Under Various Conditions Revised 1996 (82 pages) Index A-Introductory Introductory......................................

Paragraphs A-1 to A-5

B-General Electromagnetic Induction, Electric and Magnetic Induction.................................... Induction from Electrical Supply Circuits into Communication Circuits, Effect of the Earth........................................

B-1 to B-5 B-6 to B-7

C-Fundamental Principles of Shielding General........................................... Fundamental Principles of Shielding............... Calculation of Shield Factor......................

C-1 C-2 to C-16 C-17 to C-26

D-Balance of Power and Communication Circuits General........................................... Balance of Supply Circuits........................ D-2 to Configuration................................ D-9 to Transpositions............................... D-23 to Branches Consisting of Less Than the Total Number of Phase Wires........................ D-26 to Balance of Communication Circuits................. D-44 to Line Unbalances.............................. Mutual Unbalances............................ D-47 and Self Unbalances.............................. D-49 to Equipment Unbalances.............................. D-54 to Office Unbalances............................ Station Unbalances...........................

D-1 D-43 D-22 D-25 D-43 D-53 D-46 D-48 D-53 D-56 D-55 D-56

E-Transpositions General........................................... Application of Transpositions..................... Supply Circuit Transpositions................ Supply Circuit Transpositions for Low Frequency Induction.................................... Balanced Current Induction...................

E-1 to E-13 E-14 E-14 E-15 to E-48 E-24 to E-27


1996

Design of Barrels in Pairs................... Transpositions at Ends of Barrels............ Crossovers................................... Use of One Three-Phase Transposition......... Balance to More Than One Communication Line.. Transpositions to Reduce Residuals in Ground Wires, Phase Conductors, etc............ Ground Wire Induction........................ Balance to Ground............................ Load and Single Phase Extension Unbalance.... Composite Systems............................ Interconnection of Phases of Twin Circuit Lines................................... Methods of Transposition..................... Combined Systems............................. Interconnection for Least Capacitance Unbalance............................... Supply Circuit Transpositions to Reduce Noise Frequency Induction.......................... Communication Circuit Transpositions......... Transposition Systems for Communication Lines Exposed Line System.......................... Whole Line Transpositions.................... C-1 Transposition System..................... R-1 Transposition System..................... R-2 Transposition System..................... Coordinated Transpositions................... Design Procedure............................. Communication and Signal Supply Circuits on t Poles..........................

Paragraphs E-28 E-29 E-30 E-31 E-32 and E-33 E-34 E-35 to E-39 E-40 E-41 E-42 and E-43 E-44 E-45 and E-46 E-47 E-48 E-49 to E-71 E-50 to E-52 E-53 E-54 E-55 and E-56 E-57 E-58 E-59 and E-60 E-61 to E-66 E-67 E-68 to E-76

A-Introduction A-1

The remedial measures applicable in any given situation requiring inductive coordination depend upon many factors, such as the nature and magnitude of the induction and the types of power and communication circuits. It is the purpose of this section to outline the more important of these factors and the remedial measures that are applicable under various conditions. It is not the intent to give complete technical information, such as is required for design purposes, but rather to present an overall picture, non-mathematical and generally descriptive. The outline of remedial measures contains information on the types of


Part 20.1.7 situations to which each is applicable and its relative effectiveness.

A-2

It has been found desirable to divide the material and group the various items in several ways. One important division is that of noise frequency induction and low frequency induction. Noise induction has to do primarily with induction at such frequencies and of such magnitude as might cause noise in data voice and carrier circuits and is generally caused by harmonics in the power systems. Low frequency induction, on the other hand, refers generally to induction at the fundamental and lower harmonic frequencies of the power systems. The interference effects produced by low-frequency induction may be of two types; namely, interference with signal devices which operate in the lower frequency range, or induced voltages of such magnitude as to operate protectors or introduce hazard. Another important division is that between power systems and communication systems.

A-3

For a detailed treatment of the fundamental factors involved in inductive coordination, refer to "IEEE Recommended Practice for Inductive Coordination of Electric Supply and Communication Lines" IEEE Standard 776-1992. This publication is available from IEEE Service Center, P. O. Box 1331, Piscataway, New Jersey 08855. This recommended practice addresses the inductive environment that exists in the vicinity of electric power and wire-line telecommunications systems and the interfering effect that may be produced. Guidance is offered for the control or modification of the environment and the susceptibility of the affected systems in order to maintain an acceptable level of interference.

A-4

For a complete discussion of the practical factors involved in inductive coordination, refer to "IEEE Guide for the Implementation of Inductive Coordination Mitigation Techniques and Application" IEEE Standard 1137-1991. This publication is available from IEEE Service Center, P. O. Box 1331, Piscataway, New Jersey 08855. This guide provides for controlling or modifying the inductive environment and the susceptibility of affected wire line telecommunications facilities in order to operate within the acceptable levels of steady-state or surge induced voltages of the environmental interface. Procedures for determining the source of the problem are given.


1996

Mitigation theory and philosophy are discussed, and mitigation devices are described. The application of typical mitigation apparatus and techniques and installation, maintenance and inspection of mitigation apparatus are addressed. Advice for determining the best engineering solution is offered, and general safety considerations are discussed. A-5

A computer program CORRIDOR has been developed by the Electric Power Research Institute (EPRI) and AAR that enables engineers to readily determine estimates the induced voltage and current in conductors that parallel power lines and railroad tracks. Input data can include common occurrences such as multiple power lines, segmented or multi-grounded static wires, counterpoises, rail or pipeline insulators, relay impedances, ballast unbalance, bonds between pipelines or other conductors, cathodic protection anodes, and pipeline-coating and soil-resistivity changes along the length of the corridor. Most importantly, the CORRIDOR module s for the shielding or interactive effects (mutual coupling) of the various paralleling conductors of the sharing utilities, and it estimates the voltage and current coupled to the ive conductors at -defined locations along the corridor. This software is available from the Association of American Railroads, C&S Section for member railroads. B-General

B-1

Electromagnetic Induction, Electric and Magnetic Induction: Electromagnetic induction is a process that occurs whenever an electromagnetic field varies with respect to time. It is a dual process, each part of which consists fundamentally in the production of electric forces - that is, forces which in general cause voltage or electromotive forces, and which, when conductors or conducting materials are present, cause charges (that is, quantities of electricity) to appear upon the surfaces of conductors and currents to flow in them.

B-2

One part of this dual process is called electric induction, and is an effect due solely to electric charges. The electric forces concerned are those of attraction and repulsion that, charges exert upon each other. The effect can and does exist even when there are no field variations with respect to time. The word electrostatic is used to describe such a stationary state and the term electrostatic


Part 20.1.7 induction is used for the process by which a charge is made to exist upon a part of a conductor by the proximity of another charge, fixed in amount and stationary in position. The term is sometimes used as the name of the more general phenomenon that is called electric induction; but this usage is inappropriate because of the "static" part of the word "electrostatic." "Static" means fixed or unchanging with time. The term "electric" rather than "electrostatic" induction is used to convey the idea that the phenomena are, or may be, variable with respect to time, even though only effects due to charges are being considered. In this usage, "electric" is the broader term and includes "electrostatic" as a special case. Electric induction, then in the general case, is an effect due to electric charges - not to currents - that vary with time, and it consists essentially in the appearance of voltages between conductors in the vicinity of these charges and of charges upon and currents in such conductors.

B-3

The other part of the process of electromagnetic induction is called magnetic induction. It is due solely to electric currents, and the word magnetic is used because the magnetic fields associated with the currents are responsible for the inductive action. In this case, the phenomenon can only occur if there is time variation of the currents*, since an unchanging magnetic field produces no electrical effects. Thus, if the "induced" charges and currents are very small compared with the "inducing" ones, the reactions of the former upon the latter may be neglected and the analysis of the phenomena of induction is greatly simplified. This, in general, is the situation in induction from electrical supply circuits into communication circuits, except for electric induction in situations of very close exposure, such as under t use conditions.

*

For magnetic inductive action to occur at a given place, it is only necessary for the magnetic field to change at that place. This can happen if the device by which the field is produced is moved about, without changing the strength of the electric current that produces the field. This exception to the statement in the text is of little importance in the considerations that are to follow.


1996

B-4

The same set of effects comes from magnetic induction as from electric induction - that is, voltages between conductors, charges on conductors and currents in conductors. These effects, whether they arise from electric or magnetic induction, are usually considered induced voltages, charges and currents. This implies a certain point of view that distinguishes inducing from induced, which separates a part of the total electromagnetic field under contemplation as being cause, and regards the rest of it as effect. Although, strictly speaking, every charge or current reacts upon every other, and is both "inducing" and "induced," the distinction mentioned may often be advantageous for practical purposes.

B-5

This scheme, which is purely a matter of practical convenience, has led to a representation about electric induction that is somewhat misleading. That is, in most of the working data one will find electric induction as "induction from" or "due to" the voltages of such-and-such a power line configuration. It is frequently of value to , nevertheless, that the induction is really due to the charges on the line in question.

B-6

Induction from Electrical Supply Circuits into Communication Circuits, Effect of the Earth: Aside from cases of actual , the transfer of energy from an electrical supply system to a communication system takes place either (1) in parallel or quasi-parallel exposures of line conductors, or (2) through proximity of ground connections in the two systems. In the latter, "proximity" must be understood as covering the range from common or closely adjacent ground connections to separations of a mile or more, and "ground connection," for the supply system, includes accidental connection (faults to ground) as well as intentional ones. The first class is that of "inductive coupling" and the second that of "ground potential" or "end effects"; but in many practical situations, especially of low frequency induction, both types of effect are present in important degrees. However, except for cases of common or closely associated intentional ground connections, line conductors of both systems are involved.

B-7

If the line part of an electrical supply or a communication circuit consists of two or more conductors insulated from


Part 20.1.7 the earth and forming what is called a "metallic circuit," (line to line, differential, normal mode, transverse) the fact that both conductors are, and necessarily must be, closely adjacent to the ground, makes very little difference as long as both remain well insulated and are operated in a balanced manner. Under such circumstances the earth may be forgotten, and only the metallic circuits considered, so far as their mutual relations are concerned. If the insulation of either circuit becomes seriously defective or fails, or if otherwise the electrical symmetry (i.e., balance) of either circuit with respect to the earth is sufficiently impaired, the earth enters as an important factor. C-Fundamental Principles of Shielding

C-1

Voltages produced in communication lines by magnetic induction may be reduced by large amounts under favorable conditions by induced currents flowing in neighboring conductors. Also, voltages electrically induced in communication circuits may be reduced, usually by even greater amounts, by charges induced in neighboring conductors. These reactions are called shielding. Magnetic shielding may be produced by supply line ground wires, railway tracks bonded for current return, metallic sheaths of supply or communication cables, by water, gas or other types of buried pipe lines or by conductors installed specifically for the purpose. The most effective practical shields against electric induction are grounded cable sheaths and direct grounding of the communication circuits through drains or through apparatus. This section describes the general nature of shielding and illustrates its dependence upon the electrical constants of shielding conductors and upon their coupling with supply or communication lines.

C-2

Fundamental Principles of Shielding: This discussion deals explicitly with shielding against voltages along a conductor or between conductor and ground, (as contrasted to voltages between conductors), produced by residual currents and voltages. All circuits, therefore, are earth-return circuits, for which mutual and self-impedances are determined by methods described in Section D. The principles of shielding, however, are the same whether the source of the induction is in residual or balanced components, or whether the induced voltage is along the


1996

conductor, between conductor and ground, or between conductors. A system of three earth-return conductors is assumed, designated as (1) the "disturbing" conductor, i.e., the power conductor producing the induction, (2) the shielding conductor and (3) the "disturbed" conductor, i.e., the communication conductor receiving the induction. C-3

Shielding, as used herein, means the reduction* in induced voltage produced by the reaction of the shielding circuit. The shield factor is the ratio of the shielded voltage to the unshielded voltage; a low shield factor means high shielding.

C-4

Electric shielding is accomplished by placing near the disturbed conductor, or near the disturbing conductor, a third conductor bearing a charge of sign opposite to that of the disturbing conductor. The voltage induced by this charge opposes that produced by the charge on the disturbing wire, and the resulting voltage on the disturbed wire is reduced. The simplest way to charge the shield wire is by grounding it, thus permitting it to retain a net charge induced by the charge on the disturbing wire. This process is illustrated in Figure 1.

C-5

As mentioned in Paragraph C-1, the most effective practical shield against electric induction is a grounded power or telephone cable sheath. Virtually no electric field associated with the disturbing conductor exists outside of the grounded sheath of a supply cable, and none exists inside of the grounded sheath of a communication cable. It may be noted that where electric induction is concerned, it is necessary to provide low resistance grounds to sheaths or other shields. Moreover, except for long exposures, one ground connection is sufficient.

*

In certain cases the disturbed wire may be exposed to the shield wire but not to the disturbing wire. The reaction of the shield in such a case would be to increase the voltage in the disturbed wire. This effect is spoken of as "secondary induction."


Part 20.1.7

Figure 1:

Shielding Against Electric Induction.

Conductor 1:

Disturbing conductor energized to ground at voltage V, and carrying charge +q.

Conductor 2:

Shielding conductor connected to ground and carrying charge -q’ induced by charge +q on conductor 1.

Conductor 3:

Disturbed conductor. Voltage V1 induced by charge +q on conductor 1 is opposed by voltage V2 induced by charge -q’ on conductor 2.

C-6

With open-wire communication lines exposed to open-wire supply lines, shielding in many cases may be effected by the use of drainage coils or resistances, or by grounds on apparatus connected to the lines. The use of special shield wires for the reduction of electric induction, as compared to the arrangements mentioned above, apparently does not offer enough advantage to require description of methods of calculation.

C-7

Magnetic shielding is accomplished by placing near the disturbed conductor, or near the disturbing conductor, a third conductor connected in a closed circuit. Since this conductor is acted on by the primary magnetic field surrounding the disturbing conductor, a voltage will be induced therein in consequence of which a current will flow in the shielding circuit, the magnitude of which will


1996

depend upon the voltage induced and upon the self-impedance of this circuit. This current in the shielding conductor will in turn induce in the disturbed conductor a voltage, the magnitude of which depends upon the magnitude of the shielding current and the coupling of shielding and disturbed circuits. The phase relationship between this shielding voltage and the voltage induced in the disturbed conductor by the primary field will depend upon the phase angle of the shield self-impedance and upon that of the mutual impedance of shielding and disturbed conductors. For effective shielding, the shielding voltage should be as nearly as possible equal and opposite to the voltage produced by the disturbing conductor. Factors that favor this condition are low impedance of the shielding circuit, large coupling between shielding and disturbed, or between shielding and disturbing conductors, and a high ratio of inductive reactance to resistance in the shield self-impedance and the mutual impedance of shield and disturbed conductors. C-8

The physical processes involved in magnetic shielding are illustrated by the simple system shown in Figure 2. With a given current I1 in the disturbing circuit the voltages induced in the shielding circuit and in the disturbed circuit, with the shielding circuit open are: V2 = Z12I1 in shielding circuit (1) V3 = Z13I1 in disturbed circuit (2)


Part 20.1.7

Figure 2:

Shielding Against Magnetic Induction.

Conductor 1:

Disturbing Conductor

Conductor 2:

Shielding Conductor

Conductor 3:

Disturbed Conductor

With the shielding circuit closed, a current I2 will circulate in it: I2 =

V2 Z12 ___ = ___ I1 Z22 Z22

(3)

The voltage induced in the disturbed circuit by the current I2 in the shielding circuit is: V3' = Z23I2

(4)


1996

The total voltage in the disturbed circuit with the shielding circuit closed is: Z12 Z23 V3" = V3 - V3' = Z13 (I _) I1 (5) Z13 Z22 The shield factor • is then: V3"

•

Z12 Z23

=

= 1 V3

(6) Z13 Z22

The impedances Z12, Z23, Z13 and Z22 are total mutual and self-impedances of the circuits designated by the subscripts. When the circuits are uniform, parallel, coextensive* and of length s, and the shielding circuit is grounded at the ends through resistances having a total resistance R: Z12 Z13 Z23 Z22

= = = =

sz12 sz13 sz23 sz22 + R

where the lower case impedances are values per unit length, the shield factor then becomes: Z12 Z23

•

= 1 -

(7) Z13(Z22 + R/s)

C-9

From equation (6) it is apparent that for a given arrangement of disturbing, shielding, and disturbed conductors, the shield factor is unchanged when the positions of the disturbing and disturbed conductors with relation to the shielding conductor are interchanged. In other words, the shield factor is the same whether Z23 is made large and Z12 small by placing the shield close to the disturbed conductor, or whether Z12 is made large and Z23 small by placing the shield close to the disturbing wire. This is shown graphically in Figure 3 by the symmetry of the curves of shield factor versus position of shield conductor.

*

The disturbing circuit or the disturbed circuit may extend beyond the other two circuits.


Part 20.1.7

Figure 3: Variation of Shield Factor with Location of Shielding Conductor.

Separation of Shielding and Disturbing Conductor, d12, feet 1 = Disturbing Conductor 2 = Shielding Conductor 3 = Disturbed Conductor Frequency: 60 Hz Earth Resistivity: 100 Meter-Ohms Shielding Conductor: No. 0 Copper Wire; Perfect Ground Connections; Disturbing, Shielding and Disturbed Conductors Parallel and Coextensive. Shield Wire Moved Horizontally. C-10 When the shielding conductor is a cable sheath, or a wire, or grounded communication conductors, equation be simplified as follows: For a communication cable or other shield close to the disturbed conductor, Z12 assumed equal to Z13, hence Z23

•

= 1 -

_ Z22

(8)

ground (6) may sheath, may be


1996

For a power cable sheath, or other shield close to the disturbing conductor, Z13 may be assumed equal to Z23, hence. Z12

•

= 1 -

(9) Z22

C-11 The variation of shield factor with the resistance and reactance of the shielding conductor will, for simplicity, be illustrated by considering the shield to consist of an aerial shield, such as a cable sheath, placed close to the disturbed conductor and grounded at the ends. The principles involved and the general conclusions apply to any form of shield. Using total circuit impedances, the shield factor may be written as: Z22 - Z23

•

=

(10) Z22

where Z22 = R' + (R22 + jX22) is the total earth return self-impedance of the shield. R' is the dc resistance of the sheath plus grounds, and R22 - jX22 are, respectively, the real (excluding the dc resistance) and imaginary components of the earth-return self-impedance of the sheath. Z23 = (R23 - jX23) is the earth-return mutual impedance of shield and disturbed conductors. If the shield and the disturbed conductors are of the same length, R22 = R23 approximately and X22 = X23 approximately: hence R'

•

=

approximately Z22

(11)


Part 20.1.7 Equation (11) shows that the shield factor increases (shielding diminishes) as the dc resistance of the shield increases, and that it decreases with increasing shield reactance.* Thus with aerial cables, for a given grounding resistance, the shield factor decreases as the size of the cable or the number of cables in parallel increases, or for a given cable, the shield factor decreases as the grounding resistance is reduced. For a given cable and grounding resistance, the shield factor may be reduced by placing tape armor around the sheath, thus increasing its self-reactance. Increasing the frequency increases sheath reactance: also an increased reactance is associated with larger earth resistivity. Equation (11) therefore shows that the shield factor decreases with increasing frequency or increasing earth resistivity. To summarize: the shield factor decreases (shielding increases) when shield resistance decreases, and the shield reactance, the frequency, and the earth resistivity increase. If the disturbing, shielding and disturbed circuits are parallel and coextensive (the disturbing or disturbed circuits may extend beyond the other two circuits), equation (11) may be written in of unit length impedances as: r' + R/s

•

=

(12) Z22 + R/s

in which r' is the dc resistance per unit length of sheath, R is the total resistance of ground connections to the sheath and s is the length of the shielding circuit. Equation (12) indicates that the effect of a given total grounding resistance, R, is less the greater the length of the shielding circuit, and also that, under the given conditions, little is to be gained by using a shielding conductor of low resistance if it is not possible to secure a low ratio of R's. Figures 4 to 7 illustrate these *

This statement is true only if whatever is done to increase the shield reactance at the same time and by a proportionate amount increases the mutual reactance of shield and disturbed conductor; this excludes (except in a special case) increasing the shield reactance by reactance coils.


1996

variations of shield factor with constants of the shielding circuit. Figure 4: Earth Resistivity, 100 Meter-Ohms, 60 hertz.

Cable Length in Miles Indicated by Numerals in Curves. Dashed curves apply to two or more closely spaced cables having a parallel resistance smaller than that of a full size cable. Variation in Shield Factor with sheath Resistance for Aerial Cables of Various Lengths Grounded at Endpoints Through a Total Resistance of R = 2 Ohms.


Part 20.1.7

Figure 5: Earth Resistivity:

100 Meter-Ohms

Ratio of Total Resistance of Endpoint Grounds in Ohms to Length of Cable in Miles indicated by Numbers on Curves Variation in Shield with Frequency For Full-Size Aerial Cable Grounded at Endpoints


1996

Figure 6: Frequency 60 Hz

Ratio of Total Resistance of Endpoint Grounds in Ohms to Length of Cable in Miles Indicated by Numerals on Curves Variation in Shield Factor with Earth Resistivity For Full-Size Aerial Cable Grounded at Endpoints. C-12 While the discussion in the preceding paragraphs illustrates the physical nature of magnetic shielding, and the calculation of shielding in practical cases proceeds from the concepts set forth, it may be well to point out a number of factors which may not be readily apparent. In the first place, the discussion has been limited to the effect of shielding upon longitudinally induced voltages in circuits, such that no current flows along the conductor. This condition is approximately satisfied in open-wire circuits of moderate length and in cable circuits of short length, the length depending on the frequency in question: in these cases, if the circuits are terminated in grounded


Part 20.1.7 apparatus the impedance of this apparatus ordinarily is high enough compared to the conductor impedance to approximate the open-circuit condition satisfactorily. In long circuits, particularly in long cable circuits, on the other hand, even though the conductors may be open-circuited at the ends, the open-circuit condition as regards induced voltage may not be realizable because charging currents flowing through the distributed capacity of the conductors to ground may be of sufficient magnitude to cause a voltage drop along the conductors. This effect may also be heightened if the conductors are connected to grounded apparatus at the terminals, since for long circuits the impedance of this apparatus may be small compared to the conductor impedance. Figure 7: Earth Resistivity:

100 Meter-Ohms, 60 Hz

Total Resistance in Ohms of Endpoint Grounds Indicated by Numerals on Curves Variation in Shield Factor with Cable Length For Full-Size Aerial Cable Grounded at Endpoints.


1996

Under these circumstances, shielding cannot be defined as simply as when circuits are short. For the long circuit case, the calculation of shielding must take into the propagation of voltage and current along the disturbed conductors and becomes a complicated process except in the more simple cases. For practical purposes, however, cable conductors can be regarded as being short if they do not exceed 25 miles for 60 hertz and 35 miles for 25 hertz. C-13 In the discussion in Paragraph C-12, an aerial shield is used grounded only at the ends, and current in the disturbing conductor is fed in one direction only. It is apparent that the equations given above will not apply if the shield contains intermediate grounds as well as terminal grounds: because, in this case, the shield current is not constant. If current in the disturbing wires is fed from two directions, say from each end to a point inside the exposure, the equations above will apply to the net longitudinal voltage if there are no intermediate shield grounds but not to voltage to ground. It is not practicable to attempt to give general equations for the many variable conditions of this kind that may be encountered. The shielding in particular cases can usually be determined by straightforward application of circuit theory. C-14 In the case of a cable sheath that is continuously grounded, such as an underground cable, the calculation of shielding involves propagation of voltage and current along the sheath and the shield factor is consequently a more complicated function of the circuit configuration and constants. The minimum shield factor obtainable for underground cables is: r'

•

=

(13) Z22

in which the are as defined in equation (12). It will be seen that equation (13) is obtained from equation (12) when R/s vanishes. This minimum shield factor is approached in situations in which the underground cable, both the shield and the exposed conductors, extends for considerable distances beyond each end of the exposure.


Part 20.1.7

C-15 In the foregoing discussion, it has been taken for granted that there is no resistive coupling between the grounds to which the induced voltage is referred and the grounds to which the shield is connected: i.e., these grounds are assumed sufficiently far apart so that their mutual resistance is negligible. If such mutual resistance exists, it counteracts the effect of the shield grounding resistance: that is to say, the shield factor is reduced by it. In practical situations, no great amount of control can ordinarily be exercised over the resistive coupling between ground connections: its presence or absence is determined by local conditions. For example, in the case of a telephone cable sheath connected to a central office ground, the only ground practically accessible for voltage reference at the central office may be the sheath or the same ground to which the sheath is connected. In this case, the resistance of the shield ground is mutual to the shielding and the disturbed circuits, and the induced voltage is reduced by an amount equal to the drop across the shield ground resistance. The shield factor is thus smaller than it would be if the voltage were referred to some other ground, in which case the voltage would exclude part or all of this drop, depending upon the mutual resistance between the grounds. At a point on an aerial cable outside of the central office, on the other hand, the voltage between conductor and a ground other than the sheath ground, for example a guy, may be of interest, in which case mutual resistance between the grounds would in general be much smaller than in the foregoing example. C-16 The statement has been made that it is immaterial, as regards shield factor, whether the shielding conductor is placed close to the disturbed conductor or close to the disturbing conductor. While this statement is true as regards shield factor, it may not be true as regards the resulting induced voltage. Unless the separation between the disturbing and disturbed conductors is usually small, placing the shield close to the disturbing conductor will tend to decrease the self-impedance of the latter to a much greater extent than if the shield is placed close to the disturbed conductor. If the induced voltage results from a given current in the disturbing conductor, as may be the case under normal load conditions, this reaction of the shield upon the disturbing conductor will have no effect upon the net induced voltage in the disturbed circuit. On the other hand, if the induced voltage is produced by


1996

current flowing to a fault on a power conductor, this current may be increased by the reaction of the shield upon the disturbing wire, hence the net voltage induced in the disturbed wire may be longer than if the shield were placed close to the latter even though the shield factor may be the same for the two cases. C-17 Calculation of Shield Factor: Values of self and mutual impedance for use in calculating shield factor may be determined from the charts of Figures 8-10, Tables C-1 to C-4, inclusive. These are taken from Engineering Report No. 37 of the EEI-Bell System t Reports, Vol. IV. Thorough study of the report is recommended. C-18 Figure 8 and Tables C-1 to C-4, inclusive, provide the data necessary for the determination of the 60 and 25 hertz self-impedance of an overhead wire with ground return. (Z22 of equation 8, Paragraph C-10, for example.) The formula for self-impedance appears on Figure 8, together with curves giving the reactive component (X11) as a function of conductor diameter, for several values of earth resistivity. The effective resistance (R) and the internal reactance (K), which must be added, are shown in Tables C-1 to C-4 inclusive. C-19 Calculation of shield factor also requires the use of the mutual impedance between, for example, the disturbed conductor and the shield (Z23 of equation 8, Paragraph C-10). This may be derived conveniently from the curves of Figures 9 and 10, for 60 Hz and 25 Hz, respectively. The mutual impedance is plotted as a function of the separation between the two conductors, for a range of earth resistivities. C-20 The self and mutual impedances derived as outlined above, and employed in equations 8 and 9 of Paragraph C-10 will suffice in such problems as determining the shielding effect of a lead cable sheath on the internal conductors, the effect of a shield wire on the communication line or the calculation of the percent earth current as affected by the multi-grounded neutral conductor on a single-phase distribution line.


Part 20.1.7

Figure 8: Self-Impedance of One Overhead Wire with Ground Return.

- 24 – AREMA C&S Manual Part 20.1.7 Figure 9: 60-Hz Mutual Impedance of Two Overhead Wires with Ground Return.

1996


Part 20.1.7

Figure 10:25-Hz Mutual Impedance of Two Overhead Wires with Ground Return.


1996

Table C-1 EFFECTIVE RESISTANCE OF HARD-DRAWN STRANDED COPPER CONDUCTORS Taken in part from Table 26, page 421, of "Symmetrical Components: by C. F. Wagner and R. D. Evans. For a temperature of +50°C, 25°C rise above +25°C ambient. AWG

Outside Diameter (Inches)

1,000,000

---

950,000

---

900,000

Size of Conductor Circular mils

Effective Resistance (ohms per mile) 60 Hz

25 Hz

1.152

0.0685

0.0648

1.123

.0718

.0683

---

1.093

.0752

.0718

850,000

---

1.062

.0794

.0761

800,000

---

1.031

.0837

.0806

750,000

---

0.998

.0888

.0860

700,000

---

.964

.0947

.0920

650,000

---

.929

.0997

.0991

600,000

---

.891

.1090

.1070

550,000

---

.853

.1194

.1173

500,000

---

.814

.1300

.1280

450,000

---

.772

.1446

.1429

400,000

---

.725

.1620

.1600

350,000

---

.679

.1849

.1835

300,000

---

.628

.215

.214

250,000

---

.574

.257

.256

211,600

0000

.528

.303

.303

211,600

0000

.522

.303

.303

167,806

000

.464

.382

.381

133,077

00

.414

.481

.481

105,535

0

.368

.607

.606

83,693

1

.328

.765

.765

66,371

2

.292

.964

.964

52,635

3

.260

1.22

1.22

41,741

4

.232

1.53

1.53

33,102

5

.206

1.93

1.93

26,251

6

.184

2.44

2.44

The internal reactance (K) of copper conductors depends on the stranding. Values applicable to the usual strandings for wire sizes in the above table are: Size of Conductor Circular mils

Number of Strands

Internal Reactance (K) (ohms per mile) 60 Hz

25 Hz

25,251 to 211,600

7

0.039

0.016

211,600 to 400,000

19

.033

.014

450,000 to 600,000

37

.032

.013

650,000 to 1,000,000

61

.031

.013

All sizes

solid

.031

.013


Part 20.1.7 Table C-2 EFFECTIVE RESISTANCE AND INTERNAL REACTANCE OF ACSR CONDUCTORS Taken in part from Table 26, page 420, of "Symmetrical Components" by C. F. Wagner and R. D. Evans. For a temperature of +50°C, 25°C rise above +25°C ambient.

Size of Conductor Circular Mils or AWG 1,590,000 1,510,500 1,431,000 1,351,500 1,272,000 1,192,500 1.113,000 1,033,500 954,000 900,000 874,500 795,000 795,000 795,000 715,500 715,500 715,500 666,600 636,000 636,000 636,000 605,000 556,500 556.500 500,000 477,000 477,000 397,500 397,500 336,400 336,400 300,000 300,000 266,800 0000 000 00 0 1 2 3 4 5 6

Number of Wires Alum Steel 54 19 54 19 54 19 54 19 54 19 54 19 54 19 54 7 54 7 54 7 54 7 54 7 30 19 26 7 54 7 30 19 26 7 54 7 54 7 30 19 26 7 54 7 30 7 26 7 30 7 30 7 26 7 30 7 26 7 30 7 26 7 30 7 26 7 26 7 6 1 6 1 6 1 6 1 6 1 6 1 6 1 6 1 6 1 6 1

Outside Diameter of Cable (Inches) 1.545 1.506 1.465 1.424 1.382 1.338 1.293 1.246 1.196 1.162 1.146 1.093 1.140 1.108 1.036 1.081 1.051 1.000 0.977 1.019 0.990 .953 .952 .927 .904 .883 .858 .806 .783 .741 .721 .700 .680 .642 .563 .502 .447 .398 .355 .316 .281 .250 .223 .198

Effective Resistance ohms per mile 60 Hz 25 Hz 0.068 0.066 .072 .069 .076 .073 .080 .077 .085 .082 .091 .087 .097 .094 .104 .101 .113 .109 .119 .116 .123 .119 .138 .131 .129 .129 .129 .129 .148 .145 .144 .144 .144 .144 .160 .157 .169 .164 .162 .162 .162 .162 .178 .172 .186 .186 .186 .186 .206 .206 .216 .216 .216 .216 .259 .259 .259 .259 .306 .306 .306 .306 .342 .342 .342 .342 .385 .385 .592 .514 .723 .642 .895 .806 1.12 1.01 1.38 1.27 1.69 1.59 2.07 1.98 2.57 2.50 3.18 3.12 3.98 3.94

Internal Reactance (K) ohms per mile 60 Hz 25 Hz 0.026 0.011 .026 .011 .026 .011 .026 .011 .026 .011 .026 .011 .026 .011 .026 .011 .026 .011 .026 .011 .026 .011 .026 .011 .025 .011 .023 .010 .026 .011 .025 .011 .023 .010 .026 .011 .026 .011 .025 .011 .023 .010 .026 .011 .026 .011 .023 .010 .023 .010 .025 .011 .023 .010 .025 .011 .023 .010 .025 .011 .023 .010 .025 .011 .023 .010 .025 .011 .128 .053 .152 .063 .157 .065 .159 .066 .153 .064 .139 .058 .121 .050 .105 .044 .097 .040 .090 .037


1996

Table C-3 EFFECTIVE RESISTANCE AND INTERNAL REACTANCE OF STEEL STRAND AND COPPERWELD CONDUCTORS

Current (amperes)

Diameter (Inches)

Resistance ohms per mile 60 Hz

Internal Recatance (K) ohms per mile

25 Hz

60 Hz

25 Hz

Number of Strands in Conductor

Siemens Martin Steel Strand 5

1/4

12.25

12.20

0.42

0.18

--

15

1/4

12.54

12.51

.48

.20

--

25

1/4

13.04

13.02

.54

.23

--

5

3/8

5.44

5.42

.40

.17

--

15

3/8

5.49

5.47

.46

.19

--

25

3/8

5.62

5.57

.50

.21

--

5

1/2

3.40

3.27

.41

.18

--

15

1/2

3.43

3.39

.44

.19

--

25

1/2

3.47

3.41

.47

.20

--

5

3/8

5.87

5.83

.39

.17

--

15

3/8

5.94

5.86

.43

.18

--

25

3/8

6.03

5.99

.47

.20

--

High Strength Steel Strand

Copperweld Conductor - 40% Conductivity 10

3/8

1.19

1.16

.17

.08

7

50

3/8

1.20

1.16

.18

.09

7

100

3/8

1.24

1.19

.21

.10

7

200

3/8

1.32

1.27

.17

.09

7

10

1/2

.765

.730

.15

.07

7

50

1/2

.792

.740

.15

.07

7

100

1/2

.792

.750

.16

.08

7

200

1/2

.820

.776

.16

.07

7

----

3

Copperweld Conductor - 30% Conductivity 5-120

5/16

2.92

----

.18

5-120

5/16

2.45

----

.20

----

7

0.1-160

3/8

1.53

1.50

.19

0.09

7

5-200

1/2

1.03

.99

.18

.09

7

5-215

21/32

.62

----

.19

----

19

The values for the steel strand conductors were obtained from Overhead Systems Reference Book. Tables compiled by the Indiana Steel and Wire Company. The values for the Copperweld conductors were obtained from measurements made by Project Committee 2K.


Part 20.1.7 Table C-4 DC RESISTANCE OF LEAD CABLE SHEATH Resistances are computed for a resistivity of 20 x 10-6 ohms per centimeter cube at + 25°C or + 77°F.

Note:

1. The internal reactance (K) may be taken as zero for lead cable sheaths. 2. Lead cable is not recommended due to environmental hazards and regulations, but is given here for reference.

C-21 When the disturbing (or disturbed) circuit consists of several conductors, as in the case of a three-phase line, where the shield factor is most commonly used to evaluate the shielding afforded by the overhead ground wire during phase-to-ground faults, it is convenient to use the method of geometric mean separations. This is particularly so since the fault may occur on any of the three conductors, and separate evaluations of shield factor are not justified. In this approach, the geometric mean separation is used in determining the value of the mutual impedance.


1996

C-22 As an example, let S17, S27, S37 be the distances between the individual phase conductors (1,2,3) and the overhead ground wire (7), then the geometric mean spacing Sm is:

Sm =

______________ √ S17 X S27 X S37

3

(14)

The mutual impedance between phase and ground wire is then determined from Figure 9 or 10 for a separation corresponding to Sm. C-23 This method of geometric mean spacing may also be used in computing the shielding effect of the neutral conductor on a three-phase, four-wire multi-grounded neutral line. C-24 When two shield conductors, of like conductivity, are present, as in the case of two overhead ground wires, it is practical to compute the geometric mean spacing from the phase wires (1,2,3) to each ground wire (7,8) and then to combine these mean spacings in a similar manner.

(14b)

3

_______________ √ S18 X S28 X S38

Sm8 =

(14a)

3

_______________ √ S17 X S27 X S37

Sm7 =

Sm =

________ √ Sm7 X Sm8

(15)

Similar procedures may be followed for double circuit three-phase lines, though not always necessary with symmetrical configurations. C-25 With two-shield conductors (7, 8) of like conductivity, the self-impedance with earth return of the two conductors in parallel is: zs

=

Z77 – z78 ______ 2

(16)

Where Z77 is the self-impedance of one shield conductor, determined as described in Paragraph C-18, and Z78 is the


Part 20.1.7 mutual impedance between shield conductors as described in Paragraph C-19, and obtained from Figures 9 or 10.

C-26 The shield factor for two ground wires, then is, derived from equation 9 of Paragraph C-10 by substitution of the proper values: 2 Z17 • = 1 ______ (16) z77 + z78 Where Z17 is the mutual impedance between phase-wire groups and ground-wire groups, at a spacing corresponding to Sm (equation 15). D-Balance of Power and Communication Circuits D-1

D-2

In discussing balance of power and communication circuits, it is convenient to distinguish between (1) line unbalances and (2) apparatus, equipment or load unbalances. In general, in the following, the word "circuit" is used to mean the line-part of the complete circuit, without inclusion of loads or apparatus. It is believed that no confusion will arise from the occasional use of the word in a broader sense, the context being sufficient to make the meaning clear in such cases. Balance of Supply Circuits A supply circuit is balanced if the normally energized conductors belonging to it have equal self-impedances and ittances to ground and equal impedances and ittances to each other and to all neighboring conductors, in each elementary section of the length of the circuit. This is equivalent to saying that, in a balanced circuit, the conductors that are regularly energized, when the circuit is in use as designed, possess the property of electrical symmetry in any short section of the circuit. It is not necessary that any two of the sections should be alike: that is, for example, the various electrical characteristics (impedances and ittances) of the normally energized conductors may be different, in one mile of line, from what they are in another; but in each of these miles, considered by itself, the property of electrical symmetry must obtain among all of the normally energized conductors in that mile, if the circuit is balanced.


1996

D-3

The use of the adjective "elementary" (or "short") in the above definition means, strictly, that in applying the criterion of electrical symmetry the length of section to be taken is to be allowed to approach zero as a limit. While, theoretically, this might make the criterion easier to meet, this is of no importance practically, since all actual lines are more or less unbalanced, and the unbalances are approximately compensated, where necessary and practicable, by transpositions. Thus for practical purposes, the "elementary" section may often be a transposition section. Technically speaking, the length of such a section should be a comparatively small fraction of the wavelength of the highest frequency deemed to be of interest. Also, in order to include the case (discussed below) of branches having fewer than the total number of phase-conductors, an "elementary" section of the main circuit in the vicinity of such a branch must be considered to include the branch connections. It should be noticed that in the above definition of a balanced supply circuit, the characteristics of the circuit as regards balance do not depend upon the way in which the circuit is energized: nor does the presence of residual currents or voltages in a supply circuit necessarily mean that the circuit is unbalanced, since such residuals may be the result of the mode of energization, or of loading. It is also important to notice that the balanced and unbalanced, when used in describing the condition of a supply circuit with respect to electrical symmetry among its conductors, are used in a different sense from that in which they are used in describing the currents and voltages of the conductors of the circuit. It is evident that such a property, or the lack of it, is not among the characteristics of the wires to which the currents (or voltages) belong. The opposite of "balanced," when one is talking about currents or voltages, is "residual," not "unbalanced", although it is true that residual current, for example, is sometimes (inappropriately) called "unbalanced" current. Also, a ground-return circuit is sometimes said to be "wholly unbalanced." It is preferable to speak of it simply as a ground-return circuit.

D-4

It is a characteristic of a balanced circuit that if it is energized in a balanced manner and if the loads are also balanced or have no connection to neutral or to ground, no residuals will result. On the other hand, residuals are in general produced if an unbalanced circuit is energized,


Part 20.1.7 even with balanced voltages, or if a balanced circuit is energized with voltages containing residual components. In fact, since it is impossible to build electrical machinery having identical characteristics for all phases, and since it is equally impossible to construct perfectly balanced lines, residuals are necessarily present in actual lines for both reasons. Practically, it is simply a question of their magnitudes. As has been previously pointed out, the coupling between a supply and a neighboring communication circuit is usually much larger for ground-return residuals than for balanced components. While the former, for this reason, are frequently the more important in coordination problems, situations are by no means uncommon in which balanced components are of controlling importance.

D-5

In an ungrounded system, the voltages to ground are largely determined by the capacitances to earth of each phase of the whole system. If these are unequal, a residual voltage is produced. Transposition of the phase wires tends to equalize these capacitances to ground and to reduce residual voltages. In general, residual voltage due to circuit unbalances will be lower with a grounded neutral system than with an isolated system, since with the former, line capacitances to ground are shunted by transformer impedances. However, the presence of these lower impedance paths to ground tends to increase the residual currents.

D-6

In considering the matter of supply circuit balance as herein defined, it must be recognized that other factors, such as wave shape or methods of operation, may he of greater importance in contributing to inductive influence. This does not mean that circuit balance is not an important factor, but that in certain cases more can be accomplished in the control of inductive effects through the control of other factors.

D-7

For the purpose of this discussion it will be convenient to divide supply circuits into two classes: namely, transmission circuits and distribution circuits. The distinction assumed between these two classes of circuits is that transmission circuits may be thought of as transmitting power in bulk between specified points, as from a generating station to a substation which may be located at some distant point, whereas distribution circuits may be thought of as circuits which carry the power from the substation to the customers or points of


1996

utilization located in a generally limited adjacent area. Under this classification transmission circuits may be thought of as generally operating at a voltage higher than distribution circuits. However, transmission circuits may be operated at voltages as low as 6600 volts, while under certain conditions circuits operating at voltages as high as 22,000 volts may be classed as distribution circuits. Transmission circuits are more or less permanent when once established, whereas distribution circuits are subject to day-by-day changes and extensions. Another distinction is that a transmission circuit generally includes the full number of phase wires throughout its length, whereas a distribution circuit is commonly made up of a main feeder and numerous branches some of which may consist of less than the full number of phase wires. D-8

The principal factors affecting the impedance or ittance unbalance of a supply circuit are: (a) Configuration including phase arrangement on twin circuit lines. (b)

Transpositions.

(c) D-9

The distribution among the various phases of branches consisting of less than the total number of phase wires. Configuration is defined as "The geometrical arrangement in transverse section of any assemblage of generally parallel conductors including their size and their relative positions with respect to other conductors and to the earth." (See C&S Manual Part 20-1-4 (Recommended Principles and Practices for the Inductive Coordination of Railway Electrical Supply Facilities and the Commercial Communication Facilities)). Aside from its effect upon induction from balanced components, the configuration of a supply line is of interest because of its relation to ittance unbalance and impedance unbalance. As to ittance unbalance, configuration affects this only through its effects upon capacitance unbalance since, of course, it has no direct effect upon leakage.

D-10 The capacitances to ground and the mutual impedances of the normally energized conductors of a supply circuit are affected by their relative heights above ground, their spacing and by other conductors located on the same or closely adjacent lines. In discussing the effect of


Part 20.1.7 configuration on balance, therefore, it is necessary to consider it from two points of view: namely the configuration of the normally energized conductors of the supply circuit itself, and the configuration of the line as a whole, as defined in Paragraph D-9. Where the line carries only the normally energized conductors, as in the case of a three-wire three-phase line, the two points of view become the same. In general, however, other wires are present on the line in various combinations and the following shows typical examples of the various conditions that may be met: 1. Single circuit lines that carry only the wires to be energized: the circuits may be two-wire single-phase or three-wire three-phase. 2.

Single circuit lines, as described in (1) but with the addition of overhead ground wire or wires.

3.

Multi-circuit lines in which the several circuits are of the same voltage and are energized from the same source. Such lines are often spoken of as twin circuit lines, triple circuit lines, etc., depending on the number of circuits carried. Such multi-circuit lines may or may not also carry overhead ground wires.

4.

Single or multi-circuit lines in which the circuits are made up of more than the normally energized conductors, as for instance, three-phase four-wire circuits.

5.

Lines carrying combinations of one or more circuits, as described in (1) to (4) with other circuits of different voltage or frequency. One specific example would be a line carrying a 22,000-volt circuit, a 4,000-volt distribution circuit and a 220-volt secondary circuit.

6.

Lines carrying both supply and communication circuits.

D-11 Transmission circuits are generally carried on lines of the types described in (1), (2) and (3) in Paragraph D-10. Distribution circuits, on the other hand, are generally carried on lines of the type described in (4), (5) and (6) in Paragraph D-10.


1996

D-12 While the configuration of a circuit has a considerable effect on its balance if it is un-transposed, it is frequently the case that the residual voltage and ground return currents are more dependent on the method of energization, the method of connecting and the amount and type of load carried and (for distribution circuits) on single-phase branches, than on configuration. Furthermore, in cases where the capacitance unbalance due to configuration is important, it can under certain conditions be reduced by power circuit transpositions as discussed in Paragraphs D-23 to D-25. Since the configuration employed is often largely determined by structural and insulation considerations, there are many cases where it is not subject to adjustment for inductive coordination reasons alone. Where there is a choice of configuration, it is helpful to employ the one that will provide the superior balance. D-13 For a single three-phase transmission circuit carried on a line of the type described in (1) of Paragraph D-10, symmetrical configurations have in general less ittance unbalance than unsymmetrical configurations. Of the various symmetrical configurations, the triangular has the lowest capacitance unbalance to ground, the equally spaced vertical and equally spaced horizontal configurations having much higher and about equal capacitance unbalances to ground. For one single-phase circuit carried on such a line, a horizontal configuration has less unbalance than all other arrangements. D-14 The unbalance incident to configuration results in a residual voltage when the circuit is energized with balanced voltages from an ungrounded source. If the line section is short and un-transposed, and balanced voltages, equal in magnitude to the nominal voltage of the circuit, are applied between the phase-conductors, the resulting residual voltage is called the characteristic residual voltage of the circuit. The characteristic residual voltage is frequently expressed as a percentage of the nominal phase-to-phase voltage of the circuit. Thus expressed, it depends only on the configuration, Figures 11 and 12 show calculated characteristic residual voltages (in kilovolts) for single circuit lines, for a number of configurations, with various heights and voltages of energization with conductor spacings as shown in Table D-1. To use the curves, find the first column of Table D-1, the


Part 20.1.7 line voltage corresponding to the configuration and spacing of the actual line for which the characteristic residual voltage is desired. Locate this voltage on the horizontal scale of Figures 11 (or 12). The intersection of the ordinate, ing through this point so located, with the curve corresponding to the configuration and height above ground of the actual line, gives directly, on the vertical scale, the desired characteristic residual voltage, provided the actual line voltage is the same as the line voltage taken from Table D-1. If these two line voltages are not the same, the result read on the vertical scale, as described, must be multiplied by the ratio actual line voltage__ voltage from table D-1 to get the characteristic residual voltage of the line in question.

D-15 Where overhead ground wires are added to single circuit lines as described in (2) of Paragraph D-10, the situation may be considerably changed. For a three-phase circuit the preferable configuration from the standpoint of balance will depend upon the number and relative location of the ground wires with respect to the phase wires. Under certain conditions where a single ground wire is used, the inverted triangle, or where two ground wires are used, the symmetrical horizontal may be preferable. For the single phase circuit the horizontal configuration will generally be preferable. D-16 In the case of multi-circuit lines, as described in (3) of Paragraph D-10, such a variety of conditions arise that each case must be considered individually. In such cases, however, more can often be accomplished in limiting the inductive influence of the lines by suitable phase interconnection of the circuits than by attempting to select the optimum configuration. Figures 13 and 14 give some calculated data regarding the characteristic residual voltage (Erc), in percentage of the phase-to-phase voltage, for twin-circuit three-phase lines. It will be noted that the dimensions given contain no reference to a unit of length, ERC depending only on the relative magnitudes of the various dimensions. Figure 13 covers certain twin circuit configurations without ground wires, for different methods of interconnecting the conductors of the two circuits.


1996

These data are taken from the book "Inductive Interference," Railroad Commission of the State of California, San Francisco, 1919. Further data on lines without ground wires are given in that book. Calculated data for a twin-circuit line without ground wires, and with one and two ground wires, are given in Figure 14 for four schemes of phase interconnection. The pronounced effect of the ground wires should be noticed. Table D-1 Conductor Spacings for Three-Phase Circuits

Line Voltage Kv.

High or Equilateral Triangular (Feet)

6.6 11

Low Triangular (Feet)

•1•1• Horizontal 1--1 (Feet)



1.67

2

2.5

3.75

5.0

5

2

3

5

7.5

9

5

22

2.5

4

5

7.5

---

5

33

3

6

6

9

---

6

44

4

8

8

---

---

8

66

6

12

12

---

---

12

Vertical (Feet)

88

8

16

16

---

---

16

100

10

20

20

---

---

20

125

13

26

26

---

---

26

150

16

--

32

---

---

32

Note: The above spacings are for the following:

Triangular - Base of Triangle. Horizontal - Distance between outside conductors. Vertical - Distance between upper and lower conductors.

D-17 In addition to its relation to capacitance unbalance, the configuration of a power line with a ground wire affects the balance of the mutual impedances between the phase-conductors and the ground wire. Any lack of equality among these mutual impedances causes ground-return current to appear in the ground wire. D-18 These ground-return currents, although considerably less than the load currents, have a much larger coefficient of coupling and therefore may produce relatively large longitudinal voltages in exposed communication circuits. The magnitude of the ground wire currents depends upon the load currents, the degree of impedance unbalance, the selfimpedance of the ground wires and the resistance of the earth connections.


Part 20.1.7

D-19 On single-circuit lines the configuration is the principal factor determining the impedance unbalance. On lines carrying more than one circuit, certain interconnections of the various phase wires may result in considerable decrease in the unbalance. Figure 15 shows the impedance unbalance on three representative types of twin-circuit lines with one and two ground wires, showing the effects of various interconnections of the Phase wires. The configurations in the top and bottom rows are the same as in Figure 14. The lines are assumed to be carrying equal and symmetrical loads. D-20 Circuits carried on lines of the types described in (4) and (6) of Paragraph D-10, generally fall under the classification of distribution circuits. In the case of three-phase four-wire circuits having single or multi-grounded neutral, the neutral conductor is frequently grouped with the phase conductors, and the optimum configuration will depend upon the arrangements employed, the presence of other conductors and whether or not such conductors are grounded. For this class of circuit the effects of load balance, distribution of branches, etc., may be far more important from the inductive standpoint than the balance of the circuit, or circuits, as defined in this discussion. D-21 For lines of the type described in (5) of Paragraph D-10, it is necessary to consider the configuration of the line as a whole. Here again, the inductive effects resulting from the methods of operation, particularly of the intermediate voltage circuits and the distribution of branches, etc., are frequently of much greater importance than the configuration of either the line or the transmission circuit. D-22 From the above, it is evident that the effect of configuration on supply circuit balance is of importance mainly in connection with transmission circuits. Quite, commonly, in the case of distribution circuits and in some cases of transmission circuits, the effects of other factors on inductive influence are so much greater that configuration becomes a secondary matter. In certain cases, configuration may, of course, have an important bearing on induction from balanced components. In some cases, the configuration that is preferable from the standpoint of induction from balanced components, is not


1996

preferable from the standpoint of circuit balance. In such cases, it is necessary either to select the configuration according to whether it is more desirable to control induction from residuals or from balanced components, or to make a compromise between the two. D-23 Transpositions: The capacitance unbalance to ground incident to the configuration of a supply circuit can theoretically be brought to a condition of approximate balance by systematically interchanging the conductors between the conductor positions so that each normally energized conductor occupies each conductor position for an equal distance, that is, by the proper use of transpositions.


Part 20.1.7

Figure 11:Characteristic Residual Voltage of a Three-Phase Line (Single Circuit) Horizontal and Triangular Configurations.


1996

Figure 12:Characteristic Residual Voltages of a Three-Phase Line (Single Circuit) Vertical Configurations.


Part 20.1.7

Figure 13:Characteristic Residual Voltages Twin Circuit Power Lines without Ground Wires.

- 44 – AREMA C&S Manual Part 20.1.7 Figure 14:

1996 Characteristic Residual Voltages Twin Circuit Power Lines with One and Two Ground Wires and Without Ground Wires.

- 45 – AREMA C&S Manual 1996 Figure 15:

Part 20.1.7 Examples of Impedance Unbalance Between Phase Conductors and Ground Wires for Different Configurations and Interconnections.


1996

D-24 Transpositions are installed in sections of line to form what are known as "barrels." For a single-phase line, a barrel would be a given length with a single transposition installed at the mid-point of that length. For a three-phase line, a barrel would be a given length divided into three equal parts by two transpositions located at the one-third and two-thirds points, respectively. Theoretically, the length of the barrel should be a small fraction of the wavelength of the highest frequency of interest. It follows, therefore, that for low frequencies, such as 25 or 60 Hz, a barrel can be of much greater length than where harmonic frequencies are of interest, for a given degree of effectiveness. D-25 In the case of three-phase circuits having single-phase branches, or where there is a combination of circuits on the line as described in (5) of Paragraph D-10, other conditions, such as the distribution of the branches among the three phases, may be of more importance than the unbalance incident to configuration. It follows, therefore, that from the standpoint of circuit balance, transpositions find their main application to transmission circuits. Transpositions within inductive exposures are useful in controlling induction from balanced components, as will be discussed in Section G on Coordinated Transpositions. D-26 Branches Consisting of Less Than the Total Number of Phase Wires: Branches consisting of less than the total number of phase wires are rarely employed on higher voltage transmission circuits. On the other hand, they make up an important part of distribution networks, and they are sometimes used on that class of transmission circuit that also supplies distribution along its route. D-27 Since branches consisting of one wire with ground return are not recognized standard construction, they will not be considered in this discussion. Branches from two-wire single-phase circuits will therefore consist of the total number of phase wires. Since the three-wire single-phase type of circuit in common use is generally of the low voltage secondary class, this discussion will be confined to two-wire branches from three-wire three-phase circuits and from four-wire three-phase grounded neutral circuits.


Part 20.1.7

D-28 In discussing branches from three-phase circuits, it will be convenient to consider the matter from three viewpoints: namely: 1. The balance of the branch. 2. The balance of the three-phase circuit. 3. The net result when the three-phase circuit is energized in a balanced manner. On extensive systems or long branches, the matter of propagation resulting in resonance effects at harmonic frequencies becomes involved. In the following discussion Paragraphs D-29 to D-34, inclusive, consider first the situation where such effects do not arise. A discussion of these effects is given in Paragraph D-37. D-29 A two-wire branch from a three-wire three-phase circuit, even if approximately balanced of itself, will experience a residual voltage when energized due to the fact that the vector sum of the voltages to ground on the two wires is not zero. If the loads on the branch are connected between the two wires only, the load current in the branch will be balanced. Where the branch is short, charging current may not be of importance. Where, however, the branch is of considerable length, residual charging current, due to the action of the residual voltage on the capacitance to ground, may have an important effect on exposures to the branch particularly if they are located near the supply end of the branch. D-30 On the three-phase circuit the effect of the branch is to unbalance the circuit since, in effect, it adds ittance to ground to two of the phase wires without a corresponding addition to the third. When the circuit is energized in a balanced manner, two conditions have to be considered: first, if the neutral is not grounded the branch will cause the residual voltage normally on the three-phase line to be increased, but the total residual voltage on the three-phase line will not be as great as the residual voltage on the branch. Second, if the neutral is grounded the branch will affect the residual voltage of the three-phase circuit but to a smaller extent than with the isolated neutral, and will increase the ground return charging current. D-31 Two-wire branches from four-wire three-phase circuits may consist of branches from two-phase wires or from phase and


1996

neutral, the latter being referred to hereafter as phase-neutral branches. Branches form two phase-wires will have the same effect in this case as in the case of the three-wire three-phase circuits discussed in Paragraphs D-28, D-29 and D-30. In considering phase-neutral branches two conditions arise; first where the neutral is grounded at the supply end only; and second, where the neutral is grounded at the supply end and at a number of points along the line. These two conditions will be referred to as uni-grounded and multi-grounded neutral, respectively. D-32 A phase-neutral branch from a uni-grounded neutral four-wire three-phase circuit may, of course, he approximately balanced if considered apart from the three-phase circuit. However, when connected, one wire of the branch will be grounded and the branch will therefore be unbalanced. When energized, the full voltage on the branch will appear as residual voltage. The load current on the branch will be balanced, but there will exist a residual charging current having earth return which may have an important effect on exposures to the branch particularly near the supply end. D-33 A phase-neutral branch from a multi-grounded neutral four-wire three-phase circuit is unbalanced since one wire is grounded at various points along its length. When energized, the full voltage will appear as residual voltage. A substantial part of the load current, and of the transformer exciting current, gets into the earth through the ground connections. On the other hand, charging current that flows through the capacitance between the phase wire and ground is partly pulled back (through magnetic inductive action) from the earth into the neutral wire. These two opposing effects have a net result that may be in either direction at noise frequencies; that is, having multiple grounds, instead of no grounds, along the branch, may result in either a smaller or a larger inductive influence, depending on whether the more important factor is charging current (as in long, lightly-loaded lines at the higher voltages), or load current plus transformer exciting current (shorter, more heavily-loaded, lower voltage lines). The wave-shape of the impressed voltage is also an important factor in these considerations. At the fundamental and lower harmonic frequencies the inductive influence of a multi-grounded


Part 20.1.7 neutral branch is considerably greater than that of one having no grounds.

D-34 Regarding the effect of a phase-neutral branch on the three-phase circuit, the latter circuit will be unbalanced whether the neutral is uni-grounded or multi-grounded, since the effect is that of adding ittance to ground to one phase-wire without similar additions to the other two phase-wires. When the circuit is energized, the residual voltage of the three-phase circuit will not be substantially changed by connecting the branch to it whether the neutral is uni-grounded or multigrounded, and the ground return residual current will be increased in either case. D-35 If a three-phase four-wire circuit has a number of similar phase-neutral branches, the Z will be approximately balanced (aside from propagation effects) if the mileage of branch lines is approximately the same for all phases. This does not necessarily mean, however, that the charging current will be even approximately balanced at all points of the three-phase circuit. Thus, for example, if the branches from one phase are all taken off in a single stretch of line, and no other branches are connected within this part of the line nor between it and the point of supply, it is obvious that the charging current may be very substantially off balance at the end of this part of the circuit that is farthest from the point of supply. To avoid this kind of situation, the mileage of branch lines should evidently be disturbed equally among the phases, not merely on an over-all basis, but also within suitably short sections of the main circuit. To do this may be difficult if there are a few scattered long branches and many short ones. In such cases, the long branches, or some of them, may be connected to the main circuit through two-winding transformers. If such transformers are connected to two phase-wires of the main circuit, the branch will not cause capacitance unbalance to ground in the main circuit, regardless of the type of grounding (uni- or multi-) of the neutral wire, and regardless also of whether the branch itself is grounded on one side. But if the transformer is connected between a phase-wire and the neutral wire, the use of it will not prevent the branch from unbalancing the main-circuit capacitance to ground, nor (if the main-circuit has a multigrounded neutral) the appearance


1996

of ground-return residual current in the main circuit, due to branch capacitance and loads. D-36 It should be noted that the method of obtaining balance as discussed in Paragraph D-35 may have no relation to load balance among the phases and that the best distribution of branches from the standpoint of load balance may be far from the best from the standpoint of circuit balance. In considering balance, therefore, it is necessary to determine which type of balance is important and be guided accordingly. At fundamental frequencies, load balance is of prime importance. D-37 Where branches of considerable length are involved, or where the branches are associated with an extensive three-phase line, the capacitances and inductances which go to make up the self and mutual impedance and ittances to ground may be in such a combination as to approach a condition of resonance for certain harmonic frequencies which may be present in the impressed voltage or which may be produced by loads. When this condition obtains, induction due to the frequency or frequencies concerned will be accentuated throughout the length of the branch. Furthermore, the condition of resonance on the branch may materially affect the inductive influence of the three-phase portions of the supply line as well as that of other single-phase branches fed from the latter. D-38 In considering the application to practical problems of the foregoing discussion, three types of situations involving distribution circuits may arise; namely, (1) urban distribution, (2) suburban distribution, and (3) rural distribution. D-39 In urban distribution, the supply and communication circuits quite commonly occupy t poles. The communication circuits are generally in cable, the sheath of which, when grounded, provides an effective shield against electric induction. In such cases, therefore, magnetic induction from the power system currents is practically always controlling. Since the feeders are usually short and operate at 6600 volts or below, charging currents may be expected to be less important than harmonic components of the load and transformer exciting currents. On urban distribution systems, therefore, equal distribution of load and connected kva of transformers


Part 20.1.7 between the various phases is of greater significance than equal capacitances of the various phase wires to ground.

D-40 In suburban areas, the communication circuits may be a combination of cable and open wire and may be subject to either electric or magnetic induction or both. In such cases, therefore, particularly where the power circuits are long, capacitance balance as well as load balance on the distribution circuits must receive consideration. D-41 In rural areas the supply circuits may be long and may be largely made up of single-phase branches or circuits, and the loads are generally relatively light. In such cases the more important factors from the noise induction standpoint are ground return charging current, the distribution of the branches among the three phases of the feeder circuit, wave shape and in some cases residual voltage. D-42 At fundamental frequency, load balance rather than capacitance balance is controlling, in nearly all cases. Due to the normal variation of loads with time, as well as the fluid nature of distribution lines, the control of influence by load balance of three-phase, four-wire lines has not been especially successful in practice. D-43 In exposures to single-phase multi-grounded neutral lines, no possibility of load balance exists. For the sizes of neutral wires commonly used, about 75% of the load current at fundamental frequency returns through the ground. Balance of Communication Circuits D-44 A metallic communication circuit is balanced if its two sides have equal self-impedances and ittances to ground, and equal mutual impedances and ittances to neighboring conductors, in each elementary section of its length. This definition applies both to metallic circuits of two conductors and to phantom circuits. In the latter case, the wires composing the side circuits from which the phantom is derived are considered as being in parallel, and are treated as if they were single conductors. D-45 This definition is in substantially the same as the definition given in Paragraph D-2 of balance in the case of a supply circuit, and most of the discussion given in connection with that definition applies directly (in most


1996

cases with suitable and obvious changes in wording) to this. Thus longitudinal uniformity is not necessary to a condition of balance in a communication circuit, it is only necessary that corresponding electrical constants of the two sides of the circuit should be equal in each elementary section. An elementary section, from a practical standpoint, can be taken as a transposition section, and if taken in the vicinity of a branch on one side of a phantom, it must include the branch connections. The condition of balance of a communication circuit does not depend upon its mode of energization, but depends only on the self and mutual characteristics of the conductors of the circuit and neighboring conductors. In an exposure, a metallic communication circuit may be energized longitudinally by magnetic induction from a supply circuit, and from wires to ground by electric induction; but no metallic circuit voltages or currents will result from these components of induction unless the circuit, or equipment connected to it, is unbalanced. As it is impossible entirely to prevent unbalances in communication circuits or equipment, metallic circuit effects always follow from longitudinal induction or induction to ground. Practically, it is simply a question of the magnitudes of these effects. D-46 Line Unbalances: Unbalances of communication circuits are of two general types. The first may be called selfunbalances, involving only the conductors of the circuit and ground, and the second, mutual unbalances involving other conductors. Thus, a self-unbalance would exist even though all other conductors except those of the circuit in question were moved beyond the field of influence. In practice both self unbalances and mutual unbalances may have an unfavorable influence from an inductive standpoint. The resulting current or voltage in a circuit depends on both the self and mutual unbalances, and upon the modes of energization and terminal impedances of the circuit in question and neighboring conductors. D-47 Mutual Unbalances: In practice, none of the circuits on multi-wire lines are inherently balanced in respect to their mutual relations to other conductors. A close approximation to such balance is obtained, however, by means of transpositions whereby the unbalances existing in one section are neutralized by those in a nearby section of line. Thus transposition errors are the main source of


Part 20.1.7 mutual unbalances. be a factor.

In a poorly maintained line, leakage may

D-48 The mutual unbalances that remain in a well-transposed line are largely of the nature of shunt unbalances, i.e., they are equivalent to ittances connected from a wire of one circuit to a wire of another circuit. In other words, if a well-transposed pair is energized to ground, both currents and charges are produced in other wires. The currents in the well-transposed pair itself are unequal, due to the other wires, but largely because of their charges rather than because of their currents. D-49 Self-Unbalances: Self-unbalances may be divided into the general classifications; namely, series impedance unbalances and shunt ittance unbalances. D-50 A series impedance unbalance is a difference, usually local, between the series impedances of the two conductor composing the circuit. Such an unbalance may be caused, for example, by a high resistance t in one of the conductors. If such a t exists, the longitudinal currents in the conductors due to induced voltages encounter unequal impedance with a resulting difference in voltage drop on the two conductors. This difference in voltage drop causes a voltage acting around the circuit, which tends to cause noise-metallic. The effect of a given series unbalance depends, of course, on the longitudinal current through it, which in turn depends on the voltage or noise to ground and the ittance to ground of the circuit on either side of the unbalance. D-51 Shunt ittance unbalances are generally due either to unbalanced capacitances to ground or to unbalanced leakances to ground of the two wires. The effect of an ittance unbalance is to cause more current to flow to ground from one side of the circuit than from the other. Part of this excess current is drawn from the other side of the circuit, thus flowing through the terminal equipment and thereby causing noise-metallic. D-52 Some of the most common sources of self-unbalances are: 1. Series impedance unbalances (line): a. Defective splices in line conductors. b. resistance in test connectors, binding posts and fuses.

- 54 – AREMA C&S Manual Part 20.1.7 c. 2.

1996 Broken line conductors in tie wires.

Shunt ittance unbalances (line): a. Defective insulators. b. of line wires with trees, vines, crossarms, guy wires, foreign wires or with wires falling across the line. c. Leakage at protectors. d. Capacitance or insulation unbalance in cables. e. Defective insulation on bridle wires. f. Capacitance unbalance due to transposition errors or irregularities.

D-53 Other precautions that should be observed in connection with phantom circuits to avoid unbalancing them are: 1. When terminating one side circuit at an intermediate point, balancing resistance or other compensating apparatus should be inserted in the through side of a phantom group at a point where the other side circuit is terminated. 2.

When one side circuit of a phantom is looped into an office, the other side circuit also should be looped in to avoid capacity and series unbalances in the phantom.

3.

When a branch is connected to one side circuit only of a phantom group, the connection should be made to the side circuit through a repeating coil, or a branch having the same characteristics should be connected to the other side circuit. If the branch is terminated in a switchboard or at other point where it may be connected to other circuits, a repeating coil is always advisable.

Equipment Unbalances D-54 Circuit unbalances may be caused by office or station equipment and associated wiring if the equipment is not properly designed and constructed for the service in question or is not properly maintained. Equipment unbalances have the same general effect as line unbalances. They are especially important on phantom and composite circuits. D-55 Office Unbalances: Some of the more common sources of office equipment and wiring unbalances are:


Part 20.1.7 1.

Composite set unbalances: a. Unbalance between the elements of composite sets in two sides of a phantom group. b.

2. 3. 4. 5. 6.

Unbalance between various parts of a composite set: --- Series condensers. --- coils in telegraph branches. --- Condensers in telegraph branches. --- Coils in grounded branches. Loose connections due to rosin ts or poorly soldered ts. Drops of solder, wire clippings, etc., falling on terminals causing crosses, grounds or short-circuited apparatus. Poor connections at relay s in talking circuits. Relay s normally open when talking, failing to open. Variable resistance s at heat coils.

D-56 Station Unbalances: Telephone station lines are subject to self and ittance unbalances as described in Paragraph D-52. Telephone station equipment is always subject to unbalances, the more common sources of which are: 1. Leakage at protectors. 2. Unequal resistance at fuses, station terminals and switches. 3. Defective cords. 4. Ground return ringing. In situations where ground return ringing is employed, the unbalance can often be reduced by the use of either a ringer having high impedance at harmonic frequencies or by the use of a relay at the station which will connect the ringer to ground only during the ringing period. E-Transpositions E-1

General If the two sides of a metallic communication circuit were infinitely close together and thus equally exposed to a paralleling supply circuit, there would be no voltage induced directly in the metallic communication circuit. Similarly, if the supply conductors were infinitely close together and thus equidistant from the communication


1996

circuit, there would be no longitudinal circuit induction in the communication circuit from balanced components of current and voltage in the supply circuit. These ideal conditions cannot, of course, be realized in practice. However, by means of transpositions in the supply and communication circuits, the direct-metallic induction and the longitudinal-circuit induction from balanced components occurring within ading sections of the communication circuit may be neutralized to a degree and an approximation to the ideal arrangement may thus be effected. E-2

An open wire communication circuit is said to be transposed when the two sides of the circuit reverse their respective pin positions on the line according to a definite plan. A metallic circuit voltage (voltage between the two sides of the circuit) induced from an external source in a section of the circuit on one side of a transposition tends to be neutralized by the corresponding voltage on the other side of the transposition, since the voltage in the second section is reversed with respect to that in the first by the transposition. The interchange of pin positions by the conductors of a communication circuit at the transposition (the exposure conditions at the point of transposition being otherwise uniform) may be said to cause a phase change of 180 deg. in the metallic circuit induction in that particular communication circuit. Communication circuit transpositions have no effect on longitudinal-circuit induction because this type of induction takes place in the circuit composed of the communication wires in parallel as one side and the earth as the other.

E-3

Supply circuit transpositions, on the other hand, may be used effectively to reduce longitudinal-circuit induction from balanced components of current and voltage on the supply circuit.

E-4

Transpositions in a supply circuit do not reduce the induction from residual components, which act in a circuit of which the earth forms one side, except as they may do so indirectly by reducing the residuals themselves.

E-5

In the case of ground-return communication circuits where only longitudinal-circuit induction is encountered, transpositions are practicable only in the supply circuit.


Part 20.1.7

E-6

The effect of transpositions in interchanging phase conductor positions is to establish for the over-all circuit a condition of equal induction between each of the several supply conductors and the disturbed circuit.

E-7

A section of supply circuit of uniform configuration within which the transpositions are so arranged that each conductor occupies each of the conductor positions for an equivalent length is commonly known as a "barrel."

E-8

The neutralizing effect of supply circuit transpositions on longitudinal-circuit induction results from the change in phase of the electric and magnetic fields of the balanced components of voltages and currents, respectively, accompanying a change in the relative positions of the supply wires.

E-9

In a single-phase system where the currents in the two supply wires are equal in magnitude and opposite in direction, that is, 180 deg. out of phase, a transposition in the supply circuit changes the phase of the induction by 180 deg. Therefore, within a uniform parallel, one such transposition will neutralize the longitudinal-circuit induction from balanced components into the communication circuit, if located at the mid-point of the exposure.

E-10 Similarly, in a three-phase system, where the currents in the phase wires are 120 deg. apart, a transposition in the supply circuit changes the phase of the induction by 120 deg. Two three-wire transpositions of identical type, dividing a uniform parallel of a three-phase line into three equal parts, will neutralize the longitudinal-circuit induction on the communication circuit resulting from balanced components. The application of this method, however, is attended with difficulties in practical cases because of the irregular exposures usually encountered. In such cases, the transpositions are located, not at the geographical third points, but at the points corresponding to thirds of the induced potential. This is the normal method of forming a transposition barrel. E-11 In specific exposures, these theoretical transposition locations will, often times, not fall opposite neutral points in the communication transposition system. In these cases, the question as to whether it is preferable to move the supply line transposition, and thus avoid introducing


1996

metallic circuit induction, at the expense of the longitudinal circuit induction, must be answered. In other words, the relative importance of the direct and indirect metallic circuit induction, as modified by supply circuit transpositions, as well as the effect of the un-neutralized longitudinal induction on grounded circuits, must be evaluated. Where the longitudinal induction predominates, it may sometimes be preferable to re-transpose the metallic-communication circuits to coordinate with the theoretical locations of the supply line transpositions. E-12 The application of transpositions to multi-grounded-neutral supply circuits is usually not warranted. On such circuits the ground return components usually predominate; therefore, reduction of the balanced components by transpositions is of little benefit. E-13 The common functions of supply and communication circuit transpositions may be summarized as follows: 1. Supply circuit transpositions within exposures tend to reduce longitudinal-circuit induction due to balanced components. They may tend to reduce induction due to residual components if they reduce the magnitude of the residuals themselves; they do not affect the induction from given amounts of residuals. Furthermore, they may either increase or decrease the direct metallic circuit induction. 2.

Supply circuit transpositions outside of exposures have no effect on either metallic circuit or longitudinal-circuit induction due to balanced components. They may tend to reduce induction due to residual components if they reduce the magnitude of the residuals themselves.

3.

Supply circuit transpositions within exposures, where the supply line carries one or more overhead ground wires, tend to reduce the effect of induced current flowing in these wires. This is helpful in situations where normal induction from fundamental frequency currents is concerned.

4.

Where the supply line carries a drained telephone circuit, the fundamental frequency induction from induced current flowing in this circuit may be reduced


Part 20.1.7 by supply line transpositions designed to provide balance between drainage points. 5.

Supply circuit transpositions are of little benefit for multi-grounded-neutral systems.

6.

Communication circuit transpositions tend to reduce cross-induction between the various circuits on the communication line.

7.

Communication circuit transpositions within inductive exposures tend to neutralize metallic circuit induction from both the balanced and residual components of the supply system. They have no effect on longitudinal-circuit induction.

8.

Communication circuit transpositions outside of exposures have no effect on direct metallic circuit induction. They do, however, tend to reduce the indirect metallic circuit induction (from either the balanced or residual components of the supply system), if they reduce unbalances that might be acted upon by the longitudinal-circuit induction.

Application of Transpositions E-14 Supply Circuit Transpositions: The considerations which determine the need and application of transpositions in supply circuits in the case of normal low frequency induction may differ widely from those governing when noise frequency induction predominates. Low frequency induction involves the fundamental frequency and the lower range of harmonic frequencies while noise frequency induction involves the harmonic frequencies in the noise frequency range. Where the TIF of the supply system is low transpositions in the supply circuit may not be necessary from the standpoint of noise frequency induction whereas they may be necessary to reduce induction at the fundamental frequency. On the other hand, in situations where noise frequency induction is the only problem, the control of the supply system wave shape may provide a more economical means of reducing the supply system influence than the use of transpositions. Supply Circuit Transpositions for-Low Frequency Induction (This discussion on supply circuit transpositions for low frequency induction refers principally to three-phase


1996

systems. However, the underlying theory applies equally well to single-phase circuits.) E-15 When a preliminary study of a given situation has indicated the possible need of supply circuit transpositions, the order of procedure might be as follows: 1.

The obtaining of complete information about the physical characteristics of the exposure and the preparation of an exposure chart showing the relation of the communication line to the supply circuits involved in the exposure.

2.

The obtaining of complete information regarding the operating characteristics of the supply system, including maximum probable load, transformer connections, location of neutral ground connections, type of relaying, etc.

3.

The determination of the induced voltage and its effect on service.

4.

If transpositions in the supply line seem necessary, an estimate should be made of the minimum number of transpositions required.

5.

The determination of the most desirable locations for the transpositions, taking into the minimizing of the effects on both grounded and metallic communication circuits.

E-16 Careful consideration must be given to the number, location and relative importance of discontinuities within the exposure. A discontinuity as herein used is any point at which an abrupt change occurs in the magnitude or phase of the supply line voltages or currents, or in the resulting induced voltage. Particular examples are: 1. Generating stations. 2. Switching or transformer stations. 3. Substations or load points. 4. Abrupt changes in separation. 5. Changes in configuration of the supply line. 6. Crossovers.


Part 20.1.7

E-17 Transpositions, because of their application to coordination, are not considered as discontinuities, although technically included in the term. E-18 The lengths of supply line transposition barrels are largely determined by the exposure discontinuities. Attenuation and phase change effects, which are of importance at noise frequencies, are less important in the usual type of low frequency problem. E-19 Working, then, with sections between discontinuities, the longitudinal-circuit-induced voltage is determined, as explained below, for the entire exposure. The amount of this voltage and its effect on the operation of the various communication circuits involved are the basis for an estimate of the desired number of supply line transpositions. E-20 It is then necessary to select the balance or neutral points for the transposition system to be used to obtain the best neutralization of induction consistent with the minimum number of barrels. It is desirable that these points occur at discontinuities. However, to locate such points at all discontinuities is often impracticable so that careful consideration should be given to the relative importance of discontinuities to determine if the minor ones cannot be disregarded. For example, where the load taken off at an intermediate substation is a small proportion of the total transmitted load, this discontinuity may be ignored. E-21 One or more barrels of transpositions are located between successive balance points when the longitudinal-circuit induction is sufficient to warrant their use. E-22 The usual procedure in deg a barrel of transpositions is to endeavor to locate the two transpositions at points corresponding to 1/3 and 2/3 of the total induction between balance points. As explained previously, the longitudinal-circuit induction in the three sections should then be 120 deg. apart and thus should neutralize. However, in locating the supply circuit transpositions, consideration must be given to the effect on direct metallic circuit induction.


1996

E-23 In deg transposition systems for supply lines which carry overhead ground wires, consideration must be given not only to the balanced current effects directly but also to the effect of the residual current flowing in the ground wires as a result of induction from the currents in the phase conductors. The relative magnitudes of these two components of induction will determine what source should be given greater weight in the transposition design. Paragraphs E-36 to E-40, inclusive, discuss the method of estimating the effect of ground wires. E-24 Balanced Current Induction: In computing the induction for sections of uniform exposure, the coefficient of induction at the separation concerned is multiplied by the length of the paralleling section. The coefficient of induction may be determined from the curves given in Section D in of volts induced per ampere or per 100 amp. in the supply circuit per unit of length of the exposure. Sloping exposures may be divided into short elements, in which the separation at the two ends does not differ by more than 10%, and induction in each short element determined by multiplying the average coefficient by the length of the element. The average coefficient for each short element is obtained by taking the average of the coefficients for the separations at the two ends of the element. Since this average point is located on the chord of the coefficient curve rather than on the curve itself, it is necessary to use short elements, that is, elements in which the change in separation is not great in order to avoid introducing too large an error. At close separations where the coefficient of induction is large, and at separations where the slope of the coefficient curve is changing rapidly*, frequent subdivision of the sloping exposure is especially important. However, when the length of sloping exposure is so short that the induction from it is small compared to the total, fewer subdivisions may be used. A somewhat similar method of treating sloping exposures that, however, uses the average separation for the small elements rather than the average of the coefficients, is described in Section D. *

The slope of the coefficient curves for a vertically configured supply line changes more rapidly at certain separations than the coefficient curves for any other configuration.


Part 20.1.7

E-25 For either method, the induction (average coefficient times length) for each of the small sections is added cumulatively and the transpositions (for each barrel) are located at points equal to 1/3 and 2/3 of the total induction; i.e., the actual transposition points are found by interpolation at the 1/3 and 2/3 points of the cumulative column. E-26 The layout should be inspected to ascertain the relation of the transpositions to the neutral points of the communication circuit transposition system. In general, if the supply circuit transposition locations were to be altered to fit these neutral points, there would usually be some un-neutralized longitudinal induction. Consideration must be given to the effect of this on both direct and indirect metallic circuit induction, and on grounded telegraph circuits. A decision is then in order as to the desirability of the more exact longitudinal balance obtained by using the theoretical transposition locations, and the possible necessity of re-transposing or installing whole line transpositions in metallic circuits within the exposure. E-27 Where more than one barrel of transpositions is to be used, a similar procedure is followed between the next pair of balance points. E-28 Design of Barrels in Pairs: Where the length of barrel is not limited by discontinuities, and where theoretical consideration shows the desirability of installing two consecutive barrels in a particular exposure, it is desirable to design the two barrels to be exactly alike, by locating the transposition points at the 1/6, 1/3, 2/3 and 5/6 points of the total inductive length. It is frequently more economical to install initial transpositions at the 1/3 and 2/3 points. If later it develops that further reduction is necessary, a second barrel can be obtained by adding transpositions at the 1/6 and 5/6 points. E-29 Transpositions at Ends of Barrels: In general, transpositions should not be used at the ends of complete transposition barrels, since this would increase the unbalance due to phase change, and also the cost of transposing. Where it is necessary to have particular phase relations at given points, this condition can often


1996

be met by rolling certain barrels in opposite directions instead of transposing at the junction points. E-30 Crossovers: The direct balanced current induction from a supply line of horizontal configuration is changed in phase by 180 deg. at points of crossing over a communication line. Sometimes such a crossover, therefore, may be usefully employed in lieu of transpositions, when the exposure dimensions are similar in the two directions from the crossover. This method is of no benefit for a supply line having vertical or unsymmetrical configuration, nor will there be any reduction by use of this method in the induction from residual current flowing in the overhead ground wire. E-31 Use of One Three-Phase Transposition: Where a barrel of transpositions cannot be economically justified but where some relief from inductive effects is required, a three-phase transposition, located at the inductive center of the exposure, will reduce the longitudinal-circuit induction by approximately 50 percent. E-32 Balance to More Than One Communication Line: Where there are two communication lines involved in the same exposure, it is not usually possible to provide equal coordination to both. In such cases, the more important communication line, or the one more closely exposed, should be given greater consideration in deg the transposition scheme. If, as is the usual case, the balance to the other line is imperfect, it may often be improved by rolling certain barrels in the opposite direction, and by inserting additional transpositions at the balance points. E-33 In general, a diagram, similar to Figure 16, should be prepared, showing the theoretical transposition points, and the method of rolling the individual transpositions. This is especially important when reversed barrels are to be used. E-34 Transpositions to Reduce Residuals in Ground Wires* Phase Conductors* etc.: Supply line transpositions do not mitigate inductive effects due to residual currents directly, but such transpositions may reduce the induction indirectly as described below.


Part 20.1.7

E-35 Ground Wire Induction: Overhead ground wires on a supply line may be an important source of low frequency induction. It is evident that if the phase wires are not transposed with respect to these wires, a voltage to ground will be induced along them by the balanced phase currents, and a ground return current will flow which may be of considerable magnitude particularly where high conductivity ground wires are used. E-36 The resulting ground wire residual current induction on paralleling communication circuits may be largely reduced by suitable transpositions in the phase conductors. These transpositions must be located with due regard to the varying separation between the supply and communication lines in the usual manner. Since the ground wire is normally grounded at frequent intervals, the transposition barrels, while they will change the phase of the induction into the ground wire in each third of the barrel by 120 deg., will not reduce the ground wire current, since the currents in each section will still flow to ground through the ground connections. However (if the earth resistivity is constant throughout the barrel and) if the transpositions are so located that the coupling to residual currents is equal in each third of the barrel, there will be no residual current induction on the communication circuits, since the inductive effects of the current flowing in the ground wire in the individual barrel thirds will be equal and 120 deg. apart, and hence will tend to cancel. In some situations, this ideal condition may not be fully realized because of end effects, and for this reason it is sometimes advisable in severe cases to establish low impedance grounds (5 ohms or less) on the ground wire at the ends of the exposure and at transposition locations. E-37 The calculation of ground wire induction is performed by first computing the current in the ground wires per unit of balanced current. The coupling to the communication line is determined in the same manner as described in Paragraph E-24 for balanced current, except that the residual current coupling curve is used. Interpolation for transposition points is likewise done in the same way. Because of the different shape of the coupling curves for balanced and residual current induction, the transposition points (except for uniform exposures) may not be at the same locations for the two types of induction.


1996

E-38 Transpositions to balance to the ground wire are needed only within the limits of the exposure, but it is important to that since a residual current is being considered, as far as fundamental frequency induction is concerned, its effects may be appreciable at separations of a mile or more, especially in regions of high earth resistivity. E-39 It may be assumed that the ground wire current flows to earth at every point where this wire is grounded (such as at towers), but since an equal current flows up the tower due to the induced potential in the next span, the net result is that of a uniform current flowing throughout the length of the ground wire, with current flowing to ground only at towers near where the ground wire is interrupted, where transpositions are installed, and at the ends of the line. E-40 Balance to Ground: Residual currents are usually present in the phase wires of an un-transposed supply line due to the unbalanced series impedance and ittance to ground of the several phase conductors. The magnitude of the residual current is determined by the impressed voltage, load current, conductor configuration, length of supply line, location of grounded transformer banks, and other factors. This type of residual may be reduced by transposing the supply line throughout its length, thus equalizing the series impedances, and capacitances to ground of the phase conductors. E-41 Load and Single Phase-Extension Unbalance: Where the residual current is due to unbalanced load currents, as in three-phase four-wire multi-grounded neutral distribution circuits or to the unequal lengths of single phase extensions connected to the various phases, transpositions are of little benefit.


Part 20.1.7

Figure 16:Interconnection for Twin Circuit Vertical Lines Without Ground Wires.


1996

E-42 Composite systems: Since, except in uniform exposures, it is impossible to design a system of supply line transpositions which will be fully effective in reducing both the induction from the balanced load currents and from the current flowing in other parallel wires, such as ground and telephone wires, the relative interfering effect of each of these must be determined for each specific exposure, and the transposition scheme laid out giving due consideration to their relative weights. In an existing exposure, it is sometimes possible to determine the relative importance of the various sources of induction by actual tests; but in proposed cases, this must be done by calculations. The transposition scheme should be designed to provide the greatest relief from the induction as a whole, consistent with cost and practicability. E-43 Combined systems of supply circuit transpositions may be used. A common scheme is to lay out transpositions within the exposure against balanced current or ground wire induction, and to install additional transpositions outside the exposure to reduce residuals. Transpositions may sometimes be necessary in one or both of two paralleling power supply circuits in order to reduce their combined effect, including secondary induction, on a paralleling communication circuit. While the general principles given in this section will apply, such cases usually require special consideration. E-44 Interconnection of Phases of Twin Circuit Lines: The phase conductors of twin circuit supply lines may generally be interconnected to produce a partial neutralization of particular inductive effects from the two circuits. A general recommendation as to the most advantageous method in each case is not possible, as numerous factors govern the type to use in any particular case. Considering only the inductive effect of the twin circuit due to balanced currents, Figure 17 shows the relative merits of different methods of interconnection for a few configuration types at specific separations. The ratios given as IE in the drawing are approximate and will vary with conductor spacing and line separations, but the merits of the various methods of interconnection are, in general, as indicated. If ground wires or a telephone circuit are present on the supply line, a special study is necessary.


Part 20.1.7

E-45 Methods of Transposition: When transposing twin circuit lines, both circuits should be transposed at the same point, except as explained in Paragraph E-47. E-46 Transpositions in the two circuits should be rotated in such a manner that the chosen interconnection is maintained in each part of the transposition barrels. Figure 18 indicates the direction of rotation to be employed with various methods of interconnection for vertical configuration. E-47 Combined Systems: The interconnection which gives the least induction from balanced currents, Figure 17, in general, is not the one which gives the best balance to ground. For this reason, it may be desirable to transpose one of the circuits on a twin circuit line at the balance points at the end of the exposure as shown on Figure 16 in order to change from the best configuration for balanced current induction within the exposure to the best for balance to ground outside the exposure. E-48 Interconnection for Least Capacitance Unbalance: For twin circuit lines in vertical configuration* without ground wires, the interconnection giving least capacitance unbalance is with the top conductors of each circuit at the same phase, and the two bottom conductors diagonally interconnected, as shown on Figure 19. When ground wires are used, the bottom conductors should be at the same phase, and the two top conductors diagonally interconnected. For twin circuits in triangular configuration without ground wires, the least capacitance unbalance results when similarly located conductors of each circuit are at the same phase. For other arrangements a special study is necessary. Supply Circuit Transpositions to Reduce Noise Frequency Induction E-49 Transpositions in supply circuits to reduce noise frequency induction must of necessity be located with due regard to the communication circuit transpositions. The locations and arrangement of the transpositions in the two classes of circuit should be such as to form a coordinated layout. Such application is discussed in Paragraphs E-61 to E-76. * Including those with center conductors displaced.


1996 Twin Circuit Interconnection for Several Power Line Configurations and Relative Inductive Effect due to Balanced Phase Currents.


Part 20.1.7

Figure 18:Direction of Rotation of Power Circuits with Various Types of Interconnection.


1996

E-50 Communication Circuit Transpositions: Practically all metallic open wire communication circuits are transposed throughout their length. Even if no supply circuits are near the communication line, transpositions are necessary to minimize the cross-induction between the various circuits on the line. Transpositions installed solely for this purpose in open wire communication circuits, however, do not necessarily fit the discontinuities in exposures involving neighboring supply circuits in such a way as to neutralize effectively induction from these supply circuits. A decrease in the induction in a metallic communication circuit can usually be obtained in a given situation by arranging the transpositions with particular reference to the discontinuities of the exposure. Thus communication circuit transpositions have two functions: to reduce induction from other communication circuits on the same line and to reduce the metallic circuit induction from the wires of supply circuits located on the same line (t use) or on a neighboring line. E-51 The components of indirect metallic circuit induction caused by the action of longitudinal-circuit induction on communication circuit unbalances may arise either inside or outside of exposed sections. Experience has indicated, however, that in many cases an exposed section is short compared to the total length of the communication line. It has therefore been convenient to refer to this effect as occurring outside the exposed section and to contrast it with the so-called direct induction into the metallic circuit inside the exposed section. E-52 The components arising outside the exposed section may be reduced by any means that reduce the longitudinal circuit induction or the unbalances. The balance of the communication circuit depends to some extent on the transpositions employed and in a particular case the components of indirect metallic circuit induction might be reduced by changes in the arrangement of the communication circuit transpositions. However, the type of transposition section is not usually a controlling factor since there is little practical difference in the effect of different transposition systems. For this reason and because of the lengths of the lines and the consequent number of transpositions involved, it appears that the retransposition of unexposed sections of communication line


Part 20.1.7 is seldom a practical and economical measure for inductive coordination.

E-53 Transposition Systems for Communication Lines: The design of a transposition scheme to take care of both cross-induction and induction from supply circuits for any considerable number of communication circuits on a line is a complicated process. However, a definite system of transpositions, known as the Exposed Line System, has been developed for general application. Instructions covering the installation of the exposed line system are given in Manual Part 1-D-9. E-54 Exposed Line System: The Exposed Line System is designed not only to reduce cross talk but also to be suitable, when properly coordinated, for reducing the noise induction which might otherwise result from exposures with supply circuits. It consists of three types of sections, namely, standard, auxiliary, and unit designated by the letters E, L, and U, respectively. E-55 Whole Line Transpositions: Whole line transposition units were developed in order to provide for more frequent transposing in either a part or all of a transposition section designed for inductive coordination purposes, through the super-session of additional transpositions. Such transpositions can be employed effectively with the E section (and sometimes the L section) but cannot be used with the U section where phantom groups are present. These units and their application are described in Communication Manual Part 1-D-9, (Recommended Practices for the Installation of Transposition in Open Wire Communication Circuits) Section C. The whole line transposition units therein described are particularly applicable to E sections and, when properly applied, will not appreciably disturb the voice frequency cross talk in such sections. E-56 One important consideration in the use of whole line units is the fact that if a short part of an existing E section becomes exposed, it may be practicable to reduce the noise induction without re-transposing the remaining part of the transposition section. Furthermore, whole line transpositions may be employed to furnish additional transpositions in the irregularly exposed part or parts of an E section (or where the interval between two adjacent mile points of an E section is exposed for only part of its


1996

length), the coordination in the remaining (relatively uniform) parts of the exposure being satisfactorily provided by the ordinary transposition arrangements of the E section, thus avoiding the use of the shorter types of transposition section. Whole line transpositions are also useful in connection with slanting exposures and, in addition, their use, where necessary, will make it possible for discontinuities in an exposure (such as crossovers, changes in separation, etc.) to occur at other than mile points of the E section, an application which is often found to be of advantage in exposures which are otherwise uniform. E-57 C-1 Transposition System: The C-1 system is suitable for carrier frequency applications up to about 35 KHz. It may be applied to individual groups on lines transposed on the Exposed Line basis. When this is done, modifications will generally be required on some of the voice frequency facilities. Voice frequency circuits may be operated on the sides and phantoms of C-1 groups and will have about the same cross talk performance as Exposed Line facilities. The noise performance of the side circuits is generally better than with the Exposed Line design due to the more frequent transpositions; the noise on phantom circuits is about the same since they are about equally transposed under the two designs. The layout of the C-1 System is described in Manual Part 1-D-9, Section F. E-58 R-1 Transposition System: The R-1 system is intended for use on non-phantomed voice frequency facilities subject to severe metallic noise induction. Essentially it provides for transpositions on each pair at every other pole with transpositions on longitudinally or vertically adjacent pairs staggered so as to fall on different sets of poles. Transpositions should be made on double groove insulators, mounted individually or on a two-pin bracket depending on the span length. The use of drop brackets may substantially impair cross talk performance. The R-1 design may be applied to any pair on an existing voice frequency transposed line. It may generally be used on carrier frequency pole lines provided there are no carrier systems operating above about 35 KHz on the same or adjacent crossarms. The layout of the R-1 System is described in Manual Part 1-D-9, Section G.


Part 20.1.7

E-59 R-2 Transposition System: The R-2 system is similar to the R-1 except that it provides for transpositions on every fourth pole and finds its principal application when the average span length is less than about 300 ft. Because of the less frequent transpositions, the noise performance is about 6 db lower than the R-1 system for the same span length. The R-2 design is not satisfactory for use on carrier transposed lines because of possibility of voice frequency cross talk. E-60 The R-1 and R-2 systems were primarily designed for use on short distance circuits such as PBX extension loops, pony lines, block circuits, etc. E-61 Coordinated Transpositions: For coordinated transpositions to be fully effective, conditions among the various sections of line within which the induction is to be neutralized must be substantially alike as regards the relations of the supply and communication circuits to each other, to ground, and to other circuits on each line. E-62 Even though a layout of transpositions were perfectly coordinated on paper, it would not be correspondingly effective when installed because of unavoidable irregularities in the spacing of poles, in the separation between the supply and communication circuits, in the presence of shielding objects, in the heights of poles, etc. It is usually impracticable to treat these as discontinuities and to take of them in the transposition design. The extent of impairment caused by non-uniform conditions in a particular case is, for practical purposes, impossible to calculate with any degree of accuracy. General estimates, however, of the order of magnitude of the effectiveness of transpositions may be made on the basis of measurements, if any are available, for cases similar to the particular one under consideration. E-63 The design of coordinated transposition layouts cannot, in general, be carried out by the application of fixed formulas or rules but must to a certain extent be conducted as a cut and try process. A study of several different possibilities is usually involved for a particular exposure. The selection of the final design is dependent upon obtaining adequate effectiveness with due regard also to relative economies and to the reaction on circuit


1996

operation at the frequencies that are employed on the communication line. E-64 The design of a practical layout of transpositions for a particular case requires great care. In the majority of cases, the attention of an experienced designer is required to obtain satisfactory results without undue expense. Figure 19 shows an illustrative example which, together with the information given in Paragraphs E-67 to E-75, inclusive, may be used as a general guide in this work. E-65 When a preliminary study of a given situation has indicated the probable need of coordinated transpositions, the design of the coordinated layout frequently proceeds by a definite series of steps, such as are outlined in Paragraph E-67. Certain definite limitations are established by the usual conditions where the length of the communication line in the particular exposure is only a relatively small part of the total length of the line, so that the transposition system installed in the line as a whole is a primary factor in determining the choice of a suitable transposition scheme for the exposed section. For instance, where circuits transposed for carrier frequency operation are present, the transpositions in the exposed section must be such as to provide for this type of operation.


Part 20.1.7


1996

E-66 The adaptation of transpositions to fit the discontinuities of the exposure will usually be limited to adjusting the lengths of the several types of available transposition sections within the limits allowed, or combining sections having different nominal lengths. Preference is usually given to the transposition sections having the greater nominal lengths, such as the E section of the exposed line system. To avoid undesirable increases in cross induction and to otherwise avoid impairing the effectiveness of the transpositions, the adjustment of a transposition section length is usually made in such a way as to result in a decreased rather than an increased length of section as compared to the nominal length. Considerations of coordination are usually limited to fitting as far as practicable the available neutral points of the communication transposition system in the most effective manner to the exposure discontinuities by one or the other of these devices. E-67 Design Procedure: With these considerations, the usual steps of the design are as follows: 1. Obtain as complete information, as practicable, about the physical characteristics of the exposure and prepare an exposure chart showing the relation of the communication line to the various supply circuits involved in the exposure. 2.

Divide the exposure into zones between discontinuities, such that, throughout each zone, substantially the same conditions exist in the relation of the supply and communication circuits to each other and to ground.

3.

Make detailed estimates of the metallic circuit induction and longitudinal circuit induction for the various important components of supply circuit voltage and current for each zone of the exposure. These estimates are usually carried out initially as if the supply and communication circuits were totally untransposed.

4.

Make a preliminary selection of the transposition systems that appear to have a reasonable degree of application of the case in hand and make a trial adjustment of these systems to the discontinuities of the exposure.


Part 20.1.7 5.

Make an inspection of the general order of effectiveness and characteristics of the layout of this preliminary selection, with a view to eliminating from further consideration as many as practicable of those sectional arrangements, which have the more outstanding values of un-neutralized metallic circuit or longitudinal-circuit induction, the larger values of cross induction, an imperfect longitudinal circuit balance, etc. While at this stage use will ordinarily be made of the results of the estimates outlined in step (3), it will frequently be possible to use graphical methods and by them to simplify the operations and reduce the amount of calculation required. For instance, in simple cases, a brief general inspection of a layout, together with consideration of the estimated values of induction, will often show at once that certain less severely exposed parts of an exposure may be neglected, at least temporarily, while attention is concentrated on reducing the induction in the more severely exposed parts.

6.

Carefully examine certain of the layouts (those which have not now been eliminated in the steps which have been taken) with respect to their effectiveness in reducing the induction and with respect to the practicability of applying them. Where the need for supply circuit transpositions has been indicated, this step includes the design of their arrangement to coordinate with the communication transposition layout. In general, supply circuit transpositions, when used, would be located opposite neutral points of the communication circuit transposition layout, consistent with obtaining a sufficient neutralization of the longitudinal circuit induction. In uniform sections of exposure at highway separations, barrels approximately 3 or 6 miles long will coordinate with the full length E or L sections. Where the exposure involves successive full-length transposition sections, barrels of longer lengths will coordinate with the transposition layouts in the communication circuits. In the design and application of supply circuit transpositions, which are primarily used to minimize the indirect metallic circuit induction and the longitudinal induction in grounded circuits, care needs to be exercised lest the direct metallic circuit


1996

noise be increased. Where no grounded circuits are involved, too great a refinement in the neutralization of the longitudinal circuit induction may not be justified by the reduction of over-all noise in the metallic circuit. 7.

After the adoption of layout based on the preceding steps, it is necessary to consider the matter of obtaining suitable locations for the necessary transposition poles, particularly for circuits transposed for carrier operation. This factor may have a considerable influence upon the relative practicability of specific layouts.

8.

Estimate the un-neutralized induction (of various types) or noise expected to result from the particular arrangement of transpositions adopted.

E-68 Communication and Signal Supply Circuits on t Poles: A class of construction prevalent on railroads is that of a t single-phase signal supply circuit operating at voltages up to 550 volts and placed on pins at one end of a crossarm carrying low voltage signal wires, usually only one gain separated from communication circuits. This has been known to cause induction in adjacent or nearby communication circuits, even in short sections. However, the need for coordination between signal supply and communication circuits on t lines is to a considerable extent dependent upon the nature of the exposure and the wave shape of the signal supply line. E-69 Where the exposed line transposition system is present, the transpositions in the communication circuits are designed to provide adequate protection from direct metallic circuit induction if the supply circuit discontinuities are at "S" or mid-section points (E-32 or L-16). Most signal supply circuits require the connection of loads much more frequently than would be permitted by limitation to those points. It is also not good practice to adjust the telephone transposition scheme to conform to minor discontinuities of the signal supply system. In consequence, discontinuities in signal supply circuits are permitted to occur at nominal mile points of the communication transposition scheme. The signal supply circuit should be transposed at the odd mile points of the communication transposition scheme, i.e.


Part 20.1.7 1. 2. 3.

For E-sections, at the odd 1/8ths of the communication transposition scheme. For L-sections, at the odd 1/4ths. For U-sections, none for a single U-section. Where there is a series of consecutive U-sections one supply circuit transposition located at a US pole, approximately at the center of this series of consecutive U-sections.

E-70 Major discontinuities in the signal supply circuit should, in general occur at balance points in the communication transposition scheme. When this is impractical, special transpositions in the supply circuit should be installed so as to secure adequate balance between the supply and communication circuits. E-71 Major discontinuities in the signal supply circuit are: power feed point, change in pin position of the supply circuit, change in crossarm spacing between signal and communication arms of one gain or more.

The

E-72 Minor discontinuities that do not have to be taken into are: Load transformers, disconnecting switches, and end of supply circuit. E-73 Circuits transposed to 30 KHz patterns have a greater number of transpositions than those transposed to the exposed line system. They are therefore somewhat less susceptible, and discontinuities may be permitted at more frequent intervals than with 3 KHz patterns. However, it is believed that 3 KHz circuits will be present in most situations, and coordination with signal lines that is suitable for these circuits will be adequate for the 30 KHz facilities. E-74 This arrangement provides reasonable coordination to both phantom circuits and non-phantomed pairs, but may tend to increase the direct metallic circuit induction to the side-circuits of some phantom groups. Where the desired degree of neutralization is not obtained, a special study of the needs of the communication circuit will be necessary. E-75 Another method, which has been used in some instances for single-phase signal supply circuits and which has proved


1996

effective in reducing the induction in the communication circuits where the supply circuit was free of residuals, is to treat the supply circuit, so far as its transpositions are concerned, as if it were a communication circuit. For transposition purposes, it is assigned the pin position numbers that a communication pair on the same pins would take. The numbering of the pin positions for the communication circuits and their transpositions are also arranged as if the supply circuit were one of the communication circuits. For the best results, this method would, in general be confined to cases where the supply circuit was continuous throughout a complete communication transposition section and where there were no loads on the supply circuit at points within the section. E-76 Grounds on signal supply circuits, if to be used, should be made only at balance points of the supply transformers. Grounds at unbalance points are likely to increase the influence of the signal supply circuit materially, with attendant increased coordination problems. Multi-grounded neutral signal circuits will greatly increase the cost of coordinating the communication plant. Such construction is not recommended. Transposition of a multi-grounded neutral signal supply circuit offers little or no benefit to exposed communication circuits.


Part 20.1.8 Recommended Practices for Investigating Inductive Effects on Communication Facilities Revised 1997 (50 Pages)

A-1

A - General These recommended practices are for evaluating the seriousness of, and determining a solution for, problems associated with proposed or existing parallel power lines and communication lines.

A-2

The principles outlined in Manual Part 7-7 (Discussion of Fundamental Factors Involved in Inductive Coordination and of Remedial Measures Applicable Under Various Conditions), will be applied in as systematic and non-technical a manner as possible.

A-3

Inductive interference may be defined as the disturbance or complete interruption of communications, either telephonic or telegraphic, or physical hazard to personnel or equipment by extraneous voltages introduced into the communication circuits as a result of fields associated with nearby electric supply lines.

A-4

Induction problems for the purpose of this discussion have been divided into the following three classifications:

A-5

1.

Normal low frequency induction. distribution lines.

Predominantly from

2.

Abnormal low frequency induction. transmission lines above 25 kv.

3.

Noise frequency induction. Predominantly from distribution lines of 100 ft. separation or less.

Predominantly from

Normal low frequency induction results from load and transformer exciting currents that introduce into neighboring communications circuits fundamental frequency voltages (usually 60 Hz, although 25 Hz for some railroad electrifications). The third harmonic voltages (180 or 75 Hz) also are often considered as normal low frequency effects because of their large magnitudes in many cases. Induced voltages from normal low frequency induction have been measured up to 100 volts or more in severe exposures where the power system residual current was unusually high, although such voltages are generally considerably lower.


1997

The principal adverse effects that may be experienced on communications systems involve false signaling on telephone voice frequency circuits using ground return signaling and interference with the operation of ground return telegraph circuits. Occasionally normal induction on isolated sections of open wire lines may result in hazardous voltages between conductors or from conductors to ground, requiring remedial measures. A-6

Abnormal low frequency induction relates to the fundamental 60 (or 25) Hz voltage induced in communications circuits only momentarily at times of faults to ground on neighboring power circuits. Such induced voltages which may be in the order of 1,000 volts or more for severe exposures, can result in communication service interruptions due to temporary or permanent grounding of protector blocks and possible hazardous voltages to workmen along the conductors, unless suitable remedial measures are adopted.

A-7

Noise frequency induction results from the harmonics caused by power system wave shape distortion inducing voltages over the voice frequency range into neighboring communications circuits. These voltages, which may be in the order of millivolts, act on even slight unbalances in the communications circuits and may cause noise in the telephone receiver or other terminal equipment.

A-8

It is essential to keep in mind that inductive coordination involving any of the above forms of induction is a mutual problem that must be handled cooperatively with all the organizations involved. Technically sound solutions to problems cannot be expected unless the relations of the interested parties are on a sound basis. In view of the complexity of many coordination problems and the fact that they frequently involve consideration of operating requirements which differ markedly between the classes of service involved, the importance of establishing and maintaining friendly relations and arranging for frank discussions of mutual problems can hardly be overemphasized.

A-9

The following sections discuss more in detail most of the points mentioned above, as well as the consideration of remedial measures for the various types of induction.

- 3 – AREMA C&S Manual 1997 B-1

Part 20.1.8 B - Normal Low Frequency Induction This section discusses methods of estimating fundamental frequency (usually 60 Hz) normal induction from supply lines. Such lines fall conveniently into two classes, requiring different methods of treatment, namely multigrounded neutral distribution lines and transmission lines. The former is often the more serious from a normal induction standpoint, while the latter sometimes presents a difficult problem with respect to abnormal low frequency induction.

B-2

Computations are often necessary in considering a projected exposure, and this section treats in some detail the methods to be employed in making such computations. Actual measurements, however, are always preferable to computations whenever possible. It has well been said that "One test is worth a thousand expert opinions."

B-3

Before any estimate is made, it is necessary to assemble information concerning the general features of the power and communication facilities involved. This preliminary information will consist of a description of the general location and route (actual or proposed) of the lines and the type of power and communication facilities.

B-4

Using these data preliminary estimates of the coordination aspects of a given situation may be made using the charts shown on Figure 2018-1. The zones are based on certain assumptions of load current, conductor size, configuration, earth resistivity and limiting values of induction as are frequently encountered in the field. This preliminary analysis will generally indicate whether the situation will require further detailed study.


1997

Figure 2018-1:

Evaluation of Proposed Exposures to Supply Lines.

B-5

Due to the large 60-Hz residual currents inherent in multigrounded neutral distribution lines, especially the single-phase ones, their influence in the normal low frequency induction problem is often greater than that of transmission lines for similar exposure conditions.

B-6

A method will be outlined for estimating the induction from normal load currents in power distribution circuits with multi-grounded neutral. Since it is not always possible to determine accurately all of the basic information necessary for the estimate, the results will not necessarily indicate precisely the amount of induction. The method is intended to give an estimate that will usually be accurate enough for practical purposes.

B-7

The induced voltage is given by the formula: Vi = ZmlIg where Zm is the coupling per unit length, l is the length of the exposure, and Ig is the equivalent earth current.

B-8

Values of Zm applicable within the indicated separation ranges with a maximum error of less than ± 15 percent are given in the following table:

Range of Separation (feet)

p=10

50-100 100-175 175-250 250-500 500-1,000

0.31 0.23 0.18 0.15 0.08

100 0.45 0.37 0.31 0.26 0.18

Coupling-volts/ampere/mile 1,000 10,000 0.59 0.73 0.51 0.65 0.46 0.60 0.40 0.53 0.32 0.38

- 5 – AREMA C&S Manual 1997 B-9

Part 20.1.8 The symbol p indicates earth resistivity in meter-ohms. Where the value of earth resistivity is not known, a value of 100 meter-ohms may be assumed. However, it should be noted that, for wide separations, this assumption may introduce considerably more error than for shorter separations. Values for 10,000 and 1,000 meter ohms are also expressed graphically in Figure 2018-2.

Figure 2018-2: Induced Voltage Along Conductor from Residual Current - 60 Cycles

B-10 The length of the exposure, l, should be expressed in miles. B-11 Ig, the ground return current, is determined by the load current in the line through the exposure. As an approximation on single-phase multi-grounded lines, the earth current can be estimated as 80% of the circuit load current. For three-phase lines, a figure of 30% of the circuit load current is taken as the value of the current flowing in the earth. The situation should be considered on the basis of maximum load current. B-12 A more exact approximation of the earth current can be made by the following method: 1. First obtain a diagram of the feeder involved, showing mileages of the main feeder and branch lines, the average connected transformer kva per mile of small


1997

transformers, plus size and location of large ones, exclusive of three-phase banks. 2.

Determine the demand factor, that is, the ratio of the maximum kva demand on the feeder to the total connected transformer kva. In the absence of more accurate information a demand factor of 0.5 may be used.

3.

Determine the size of the neutral conductor making up the major portion of the feeder.

4.

Determine the length and location of the exposure.

5.

If data are readily available, determine the earth resistivity.

6.

Plot a diagram of the exposure showing points where important branch lines leave the main feeder.

B-13 From the information as to connected transformers kva assign as an equivalent load at the end of the exposure furthest removed from the source of power, the total kva of transformers connected to the feeder and its branches beyond that point, plus one-half of the total kva of transformers distributed through the exposure. At points within the exposure where there are large concentrated loads or where branch lines leave the feeder, assign an equivalent load equal to the total connected transformer kva of the load or branch. B-14 Find the currents due to the various equivalent loads by multiplying the kva of each by the demand factor and dividing by the nominal line to neutral voltage. B-15 Where the currents so determined apply to sections of the exposure, as in the case of branch lines or concentrated loads within the exposure, determine an equivalent current applicable to the entire exposure by multiplying the section current by the ratio ls/lt, where ls is the distance from the end of the exposure nearest the supply substation to load or branch line, and lt the total length of exposure.


Part 20.1.8

B-16 Add directly the individual equivalent currents so determined to obtain a total equivalent current (I). Find the corresponding earth current Ig, where Ig = KI amperes. B-17 For neutral conductor approximate K values are: Conductor Size

K Value

No. 2 copper or equivalent.................. 0.65 No. 4 copper or equivalent.................. 0.75 No. 6 copper or equivalent.................. 0.85 No. 8 copper or equivalent.................. 0.9 B-18 This value of Ig can be used in the formula Vi = ZmlIg as explained previously. B-19 If there are major variations in separation or shield factor (K) within the exposure, divide it into sections of fairly uniform separation and shield factor and apply the above procedure, treating each section as a separate exposure. Add directly the induced voltages found for each section to determine the total voltage. B-20 In computing normal 60-Hz magnetic induction from transmission lines, there are a number of factors that must be evaluated. These include: 1. Induction from the balanced currents. 2.

Induction from the ground return currents that flow in the overhead ground wires of the transmission line as a result of induction into these ground wires from the phase currents.

3.

Induction from the residual currents flowing in the transmission line phase conductors.

B-21 In a specific case the magnitude of induced magnetic potential from balanced three-phase circuits depends somewhat on the configuration and spacing of the power conductors. Figures 2018-3 and 2018-4 are typical curves for coupling coefficients. These coefficients are expressed in volts per mile per 100 amp. of balanced


1997

current. These curves apply to average soil conditions and are valid only for 60-Hz currents. B-22 The induction from the overhead ground wires is most likely to be important where high conductivity ground wires are used. Steel ground wires in the smaller sizes, around 3/8-in. diameter, offer sufficiently high impedance to the flow of current that their inductive effect will usually be less than that from the balanced currents. B-23 The residual current in the phase conductors is an unknown quantity when a proposed exposure is under consideration. Sixty Hertz residual currents of 5 to 10 amp. are not unusual and may be used for estimating purposes. The induced voltage from such residual currents is computed by the formula in Paragraph B-7, and adds to the induced voltage from the three-phase balanced currents. B-24 This section left blank. B-25 Induction into dc grounded telegraph circuits below 10 volts will usually not be troublesome; voltages between 10 and 25 volts are likely to require remedial measures and voltages in excess of 25 volts will definitely require correction. Due consideration must be given to existing induction on the circuits in question. Higher speed telegraph circuits approaching 60-Hz operation will suffer comparable impairment at lower induced voltages than those named above. For metallic operations considerably higher voltages than those referred to may be tolerated. B-26 Normal low frequency induction has been known to interfere with 60-cycle signal systems operated by track circuits. C-1

C - Abnormal Low Frequency Induction The purpose of this section is to describe methods of determining whether the low frequency induction from supply system short circuit currents to ground warrants remedial measures, and if so, to what extent such measures should be undertaken. Abnormal low frequency induction affects both ground return and metallic communication circuits. It results from high ground return currents that occur at times of ground faults on neighboring supply systems and its characteristic is, therefore, one of relatively high induced voltages of short duration. The effects on the communication system vary over a wide range from


Part 20.1.8 the distortion of signaling, false signals, loss of synchronism, operation of protectors and communication plant damage, to acoustic and electric shock hazards in extreme cases. Important factors in connection with this type of induction are the magnitude of the induced voltage, the frequency of its occurrence and the length of time that each occurrence persists.

Figure 2018-3: Induced Voltage Along Conductor From Balanced Three-Phase Currents Horizontal and Triangular Configuration - 60 Hz, 20 Meter Ohms

- 10 – AREMA C&S Manual Part 20.1.8 Figure 2018-4: Induced Voltage Along Conductor From Balanced Three-Phase Currents Vertical Configuration 60 Hz, 20 Meter Ohms

1997


Part 20.1.8

C-2

This section covers analyses of both proposed and existing situations. The same data are required for both, the principal difference being in the manner of obtaining the information and its reliability. For example, coupling can often be obtained by direct measurements on the circuits involved in an existing exposure whereas for a proposed exposure, other means must be used. Also in existing exposures the frequency of faults on the power system and the troubles experienced in the communication system are known whereas an estimate of these must be made for a proposed exposure.

C-3

Because of the many factors involved in low frequency induction, it is not practical to set definite limits for the magnitude of the voltage which can be tolerated in the communication plant from the standpoint of safety and service reactions. Therefore, to provide a basis for appraising the possible effects of a particular exposure, it is suggested that information be prepared on certain factors that will enable estimates of the following type to be prepared. 1. Service Reactions: Estimated frequency of occurrence and number of momentary protector block operations. Estimated frequency of occurrence and number of protector operations resulting in permanently grounded blocks. 2.

C-4

Safety: Estimated miles of communication line subjected to significant voltages; the frequency of occurrence of these voltages and their duration. These estimates should include voltage differences between conductors and between conductors and ground or grounded metallic objects, and voltages across an "open" conductor.

The service reactions and hazards of low frequency induction are subject to wide variations and estimates of these factors will not have a high degree of precision. Furthermore, in some phases of the study, rough approximations must be used. On the other hand, reasonable accuracy is practical and should be obtained in connection with the fault currents, coupling, fixed shielding, etc.

- 12 – AREMA C&S Manual Part 20.1.8 C-5

C-6

1997

General Procedure in Analyzing Problems: An analysis of an inductive exposure situation should, in general, cover the steps given below. 1. Estimates or measurements of coupling, including all shielding except that due to grounded communication conductors and cable sheaths. 2.

Magnitude and duration of fault currents through the exposure.

3.

Estimates of primary field calculated as the product of the coupling determined in (1) and the magnitude of fault current determined in (2).

4.

Estimates of shield factor for grounded communication cable sheaths, and normally grounded communication conductors.

5.

Estimate of shielded longitudinal voltage as product of (3) and (4). This is called herein longitudinal induced voltage.

6.

* Estimates of voltages across protectors and the likelihood of protector operation for selected fault locations.

7.

Determination of approximate number of protectors likely to be operated for selected fault locations.

8.

Determination of current through protectors and the likelihood of permanent protector grounding for selected fault locations.

For a complete analysis of an inductive problem other factors should also be considered such as: 1. Voltage distribution for selected fault locations: a. Conductor voltage to ground or to sheath. b. Voltage between conductors. c. Voltage across an open in a conductor.

* Actually the voltage across protector blocks cannot exceed the operating voltage of the block. Here, and in the following, the expression "voltage across protectors" means the voltage that would exist at a given point if the protector blocks were removed.


Part 20.1.8 2.

Average frequency of occurrence of faults over the power line. (Faults per 100 miles of power line per year.)

3.

Determination of miles of power line over which faults at different locations will produce significant voltages and currents.

4.

Miles of communication line subjected to different values of voltage for various power line fault locations and frequency of occurrence of such faults. (Fault-mile products.) It is usually difficult to obtain accurate data regarding many of these factors, consequently a detailed discussion is not included.

C-7

In certain cases, a preliminary analysis, consisting only of the first few steps necessary for a complete study, may develop that a particular problem can be dismissed with no further work. For example, preliminary scrutiny indicating that voltages induced will be below protector breakdown may show no further study necessary if the durations of fault currents are not over two or three seconds. If the number of faults that might result in voltages above protector breakdown is large, or if a border line case is indicated, a fairly complete study should be made, and in more severe cases complete studies are necessary.

C-8

The importance of an inductive exposure is determined by considerations of both service reactions and safety-not by any single factor such as the magnitude of the longitudinal induced voltage. As explained below, the appraisal of service reactions is based on a consideration of how many and how often protectors are likely to be operated or permanently grounded. The appraisal of safety is based on a consideration of the frequency of occurrence of significant voltages, their duration, the number of miles of communication line subjected to these voltages, etc.

C-9

Detailed Procedure in Analyzing Problems Coupling: As indicated in Paragraph C-5, it is usually desirable to determine first the coupling between the power and communication circuits including shielding effects of ground wires on the power line and of other conducting paths not associated with the communication line. The


1997

product of this coupling factor and the fault current through the exposure is the primary field, which excludes the effect of shielding from conductors on the communication line. The longitudinal induced voltage is found by multiplying the value of primary field by the shield factor for the communication cable sheath (if any) and normally grounded conductors. In some cases the coupling and shield factors can be estimated with sufficient accuracy (ER*-14,26,48), while in other cases the coupling and shielding must either be measured directly or computed with the assistance of measurements of earth resistivity (see Section D). The importance of earth resistivity depends upon the separation between the power and communication circuits. For example, a 100 to 1 change in earth resistivity results in less than a 2 to 1 change in 60-Hz coupling at about a 60-ft. separation, but approximately a 30 to 1 change in coupling at a separation of 5,000 ft. C-10 Paragraph B-8 and Figure 2018-2 give information by which coupling factors can be readily estimated and the primary field calculated for particular conditions, provided a high degree of accuracy is not required. TO obtain a higher degree of accuracy actual coupling between power and communication circuits should be obtained by measurements. C-11 Magnitude and Duration of Fault Currents: The magnitudes and durations of fault currents for use in analyzing an inductive problem should be arrived at only after consulting the power company involved as suggested in Paragraph A-8. In some situations, particularly for exposures to relatively short power lines, fault resistance is an important factor in determining fault current and a choice for its value for use in calculations should be made only after careful consideration. The results of extensive t tests indicate that where fault resistance is to be allowed for in fault current computations, 20 ohms for line and 5 ohms for substation ground faults are reasonable values to use (ER-39).

*

ER-Engineering Reports of the t Subcommittee on Development and Research of the Edison Electric Institute and Bell Telephone System.


Part 20.1.8

C-12 Maximum Longitudinal Induced Voltage: The longitudinal induced voltage in itself is not sufficient for judging an exposure situation. It does, however, provide a starting point in an investigation, since the resulting currents and voltages on the communication line depend on it. The maximum longitudinal induced voltage is that obtained for the "worst" fault location; that is, the location for which the fault current and coupling are so related that their product is a maximum. In most cases the "worst" fault location can be selected by inspection. In others it may be necessary to make estimates for faults at a number of locations from which the "worst" may be selected. C-13 Voltages Across Protectors and Likelihood of Protector Operation: If the voltage at a protector point exceeds the operating voltage of the protector, the protectors at both ends of the circuit will operate (assuming that there is no drainage at either end.) As mentioned previously, standard protectors operate so fast that the voltage across them cannot rise above the operating value. The following tabulation shows the average and approximate range of 60-Hz breakdown voltages for the various spacings of protector blocks commonly used:

Average operating voltage Minimum operating voltage Maximum operating voltage

3-mil Spacing 300 250 400

5-mil Spacing 500 300 800

60 Cycle rms Volts 6-mil 8-mil Spacing Spacing 600 800 500 400 800 1000

14-mil Spacing 1200 1000 1500

It will be noted that the average breakdown voltage is at the rate of about 100 volts rms per mil spacing of the blocks.

C-14 At best, it is a rather complicated procedure to estimate precisely the voltage across the protectors at the two ends of a conductor when there are other conductors on the line which are grounded at their ends since these other grounded conductors exert a considerable shielding effect and the total induced voltage usually does not divide equally across the protector blocks at the two ends of the communication circuit. Experience indicated that a practical assumption is that if the longitudinal voltage in a conductor is above 500, 3-mil spaced protectors will operate; if it is below 500, the protectors will not operate. This value of longitudinal voltage is about midway between that for which two sets of protectors in


1997

series will operate under the most unfavorable conditions (about 400 volts) and that for which they will operate under the most favorable conditions (about 600 volts). Where protectors of other spacing are used at terminals, these values will be approximately directly proportional to the air gap spacing. Likelihood of Permanent Protector Grounding for Selected Faults C-15 The permanent grounding of carbon block protectors depends upon the current through the blocks, and its duration. Tests made on new 3-mil blocks have yielded average values of these factors that are summarized in the table below: Average Number of Occurrences Required to Cause Permanent Grounding of 3-mil Spaced Blocks Duration Several Seconds 1 Second 0.5 second 0.2 second 3-5 cycle

1.5 Amp. Many Many Many Many Many

2 Amp. 1 5 or 6 10 or more Many Many

5 Amp. 1 2 4 8 Over 10

C-16 The figures cannot be used to predict block or group of blocks will or will grounded in a particular occurrence. used to give an idea as to the number grounded over a period of time.

10 Amp. 1 1 or 2 2 or 3 3 or 4 Over 5

whether any particular not become permanently However, they can be of blocks that will be

Discussion of Remedial Measures C-17 Coupling and Shielding: The most foolproof method of reducing coupling is to secure increased separation. Such a solution, however, is not always practical. C-18 Other methods of reducing coupling are substituting metallic sheath cable for open wire circuits, the use of steel tape armoring on communication cable, and installation of shield wires on the power or communication line. The following observations may be made with respect to these measures: 1. Under the most favorable conditions, the shielding for a lead sheath is about 50 percent for a full size cable.


Part 20.1.8 2.

Shield wires of practicable sizes on either power or communication lines do not usually provide shielding of over 50%. In communication cables, additional low frequency shielding can be obtained if copper is added as circuits rather than as separate shield wires.

3.

Generally, tape armoring provides a higher degree of shielding than shield wires.

4.

Low resistance grounds on the sheath or other shield conductors are essential to obtain maximum shielding.

C-19 Power System Influence: Various developments in the power industry during recent years have had a definitely favorable reaction on low frequency inductive coordination. The most significant of these are measures taken to reduce the frequency of occurrence of ground faults which cause power line outages, and measures to insure more prompt clearance of such faults. C-20 On several occasions, residual current limitation has been used as a means of reducing power system influence. The usual form of such limitation involves resistance or reactance in the neutral-to-ground connections of important transformer supply banks (ER-27). The type and amount of neutral impedance that can be used in any power system depends upon system layout, insulation levels, relaying systems, etc. The effect on low frequency induction of such current limitation can be summarized as follows: 1.

For exposures near the power supply point, the hazard to workmen due to induced voltages frequently can be reduced by the use of relatively small values of neutral impedance.

2.

For exposures remote from the source of supply, comparatively large values of neutral impedance would be required and these frequently are impracticable.

3.

There is a tendency for power system relaying to become slower and less positive where large values of neutral impedance are used. This may actually increase the influence of the system.

C-21 From the standpoint of limiting ground fault currents, a special form of neutral impedance known as the Petersen


1997

coil, or "ground-fault neutralizer" or "resonant" grounding is probably the most satisfactory. In the United States the use of the Petersen coil is limited to a large extent to situations where special kinds of power operating problems exist. The Petersen coil however acts to increase the 60-cycle residual current during normal operation of the power system. C-22 Communication System Susceptiveness: The two measures which are most widely used now to reduce the susceptiveness of communication systems to low frequency induction are short-circuiting relay protectors (ER-41) and drainage. The more important differences between relay protectors and ordinary protectors can be summarized as follows: 1.

The multi-grounding type of relay protector is used extensively for the reduction of hazard. With this type all wires are grounded whenever any protector in the group operates, thus insuring shielding from all of the wires in the group. By the same token, potential differences between wires at the protector point are brought essentially to zero.

2.

With multi-grounding type relay protectors certain circuits on the line may be short-circuited and grounded at times when the protectors on them would not otherwise be operated. Hence in cases where, in the absence of relay protectors, only a small proportion of the regular protectors would operate, the service may be impaired. On the other hand, in cases where the regular protectors on most of the circuits would operate, the service may be improved by relay protectors, and in particular, where permanent grounding of regular protectors may occur, the improvement in service may be relatively large.

3.

If multi-grounding relay protector installations are appropriately placed, substantial reductions in voltage-to-ground hazards can be secured, and voltage differences at cable poles can be virtually eliminated.

4.

Unit type relay protectors, also known as arrester relays, are frequently used to improve service by preventing permanent grounding of regular protectors.


Part 20.1.8

C-23 The location of relay protectors should be such as to provide the largest possible reduction in hazard from a minimum number of installations. Locations at or near communication entrance cable poles are frequently desirable since relay protectors at such locations often give maximum effectiveness, cable sheaths can often be used for ground, and maintenance is facilitated. Installations at other points frequently involve "making" low resistance grounds, which in some cases may be expensive and difficult. In some cases, of course, relay protector installations can be located in towns or other places where water pipes or other extensive grounding structures are available. C-24 Drainage can sometimes be used to eliminate even momentary protector operation on metallic circuits used only for voice or carrier transmission. A physical circuit is drained simply by connecting the drainage coil across the line with windings in series-aiding and with the neutral point grounded. A phantom group requires three coils at each drainage point, a single coil being connected across each side circuit, the neutral points of which connect to the line terminals of the third coil, and the neutral of this third coil is grounded. C-25 Acoustic shock may be caused by a high induced voltage operating a protector or otherwise breaking down the insulation on one side of a telephone circuit or by operating the arresters on the two sides of a pair unsymmetrically. Under such conditions, the difference between the voltages simultaneously appearing in the two sides of the circuit causes a discharge of current through the terminal apparatus. C-26 The device known as the varistor, which consists of an assembly of copper oxide discs, has been used widely as a means for reducing acoustic shock. This device has the property of decreasing its resistance with increase in voltage across its terminals, that is, when such a device is placed across the circuit, the shunting effect increases with increasing voltage. D-1

D - Noise Frequency Induction Introduction: This section discusses the general principles and procedures involved in determining the technical solution to a noise frequency inductive coordination problem. It is based largely on experience in


1997

many such situations and an attempt has been made to summarize this experience as concisely as practicable. D-2

It is obviously impractical to set down any procedure that will be universally applicable to all noise problems. There is too much variety among problems. However, experience has shown that there are several methods of approach and this section is designed to be of help in finding the method most likely to secure the best overall results.

D-3

This section has been prepared to meet the needs of the following: 1. The engineer who has had little or no experience with noise coordination problems, but who wishes to become generally familiar with the fundamentals and methods of attack and to know where to find detailed information on particular phases of the work. 2.

The experienced coordination engineer who wishes a ready reference to the available material for use in his day-to-day problems.

3.

The supervisor who wishes to have a broad picture of the essential factors involved in noise coordination problems.

To meet these needs the discussion of the body of the section assumes knowledge of the meanings of the special used in noise coordination studies and of the physical processes of induction. However, explanations of these fundamental ideas are given in Section A of the Manual Part 7-7. D-4

It is essential to keep in mind that inductive coordination is a mutual problem that must be handled cooperatively with the power organizations. Technically sound solutions to problems cannot be expected unless the relations with the power organizations are on a sound basis and sound relations cannot be long maintained unless technically sound solutions to specific problems are secured. This is not a new thought, nor is it difficult to understand its importance, but situations sometimes arise in which it seems evident that its full significance is not appreciated.

- 21 – AREMA C&S Manual 1997 D-5

Part 20.1.8 Experience has indicated very definitely that in order to arrive at technically sound solutions there are a number of principles that must be observed. Furthermore such experience has clearly shown that failure to observe any one of these principles may and frequently does lead to unsatisfactory results in specific cases or to unsatisfactory relations or to both. These principles are outlined below. 1.

Do not try to arrive at a conclusion without sufficient facts. Both the facts and the conclusions should be arrived at cooperatively with the power organization.

2.

Weigh the various factors involved in a problem properly. For example, do not concentrate on some factor which may be the cause of high influence and neglect a possible cause of high susceptiveness, and do not spend too much time correcting the source of 15 db of noise while leaving a source of 40 db uncorrected.

3.

Wherever practicable use measured rather than computed values. No matter how precisely computations are made, the results are no more accurate than the data or assumptions on which they are based. There are few things as detrimental to sound conclusions (or to relations) as the use of values purporting to be correct to three or four significant figures when the assumptions on which they are based may be off two or more to one.

4.

that a power man knows more about the power business than a communication man and is the one who should determine what can and what cannot be done on his system.

5.

that a power man ordinarily has no particular reason or incentive to take the lead in solving an inductive coordination problem. It is up to the communication man to follow up each situation and to carry out any arrangements made with the power man at the earliest practicable moment.

- 22 – AREMA C&S Manual Part 20.1.8 D-6

1997

There are three factors that combine to determine the overall effect of noise on exposed communication circuits in an area. 1. The inductive influence of the power system. 2.

The inductive coupling between the power and communication systems.

3.

The inductive susceptiveness of the communication system.

In analyzing an existing or potential problem, each of these factors should be given proper weight. The most successful investigating techniques involve securing the data necessary to weigh properly these three factors as a basis for arriving at a conclusion as to which alone or in combination should be controlled. D-7

There is no ready rule for determining how much control can and should be exercised over each of these factors or even over the final result of all three of them (i.e. the noise). Furthermore, a proper balance of these factors in one case will be out of line in another or might have been out of line in the same case had it occurred a year before or a year later. The balance is constantly shifting with developments in the art, with material and manufacturing conditions and with many other factors.

D-8

It is desirable to avoid the use of arbitrary "limits" for power system influence and noise. Experience over a long period has shown that difficulties nearly always arise in the t solution of noise problems when the concept of "limits" is introduced. On the other hand, most problems have been satisfactorily worked out on the basis of reasonable control of the influence, coupling and susceptiveness, as described above. The noise objectives that are used by the maintenance people in day-by-day operation of the communication plant are for their guidance in determining whether the plant is in trouble and must not be thought of as engineering limits.

D-9

In noise coordination work it is important to be sure one thinks only in of harmonics rather than the fundamental frequency. When looking at a power system it must be seen not as a system transmitting kilowatts from a group of generators to a group of loads but purely as a


Part 20.1.8 system composed of inductances, capacitances and resistances with one or more sources of harmonics on it. Where these harmonics originate, where they go, how they are attenuated or amplified (as by resonance) usually bear little or no relation to the 60 Hz characteristics.

D-10 The results of noise tests on poorly balanced communication circuits (where the unbalance is due to poor maintenance) should never form the basis for negotiations with a power company concerning a noise problem. Where extensions of or changes in a power system have caused noise increases, or exposed circuits, it may be desirable to investigate influence, coupling and susceptiveness conditions cooperatively, before reaching conclusions that improved balance is desirable. General Considerations D-11 Certain general considerations common to all types of noise frequency induction studies are discussed below with references to related material that gives detailed discussions of the various factors. D-12 Layout of Power and Communication Facilities: The first step in any general survey of noise conditions or in an investigation of a specific noise case is to obtain up-to-date information on the layout of the power and communication systems involved in the problem. There is probably no greater single cause of delay in solving such problems than an attempt to proceed without adequate information of this type. These data will normally include information on the relative locations of the power and telephone circuits involved, the type of power system, source of supply for the particular feeders under consideration, transformer connections, etc., as well as the types of communication circuits and equipment used. Ground connections and continuity of any telephone cable sheaths involved in a specific noise problem should be carefully checked. Such data should normally be available in the records of the power and communication companies, but, if there is a possibility of the records not being kept up to date, these will need to be carefully checked at the start of the study. A brief description of the physical situation and of the power and telephone equipment involved should always form part of the report covering the test results. (See Paragraphs D-50 to D-53, inclusive.)


1997

D-13 The information on the power and communication system layout and type should be "adequate" in all cases; the type and amount of information to be assembled should be carefully considered in the light of the nature and extent of the problem. It is undesirable to attempt to secure more detailed information than is necessary, particularly when it involves asking a power company to prepare and furnish information on every detail of an extensive system. While considerable experience is necessary before completely sound judgment can be exercised in this important matter, the principles involved are briefly outlined below and will be made clearer from study of the remaining parts of this section. 1. The first principle is to decide what the general scope of the problem is or is likely to be, viz.: a. Is it a specific problem involving only one or more exposures? b.

Is it a general problem that extends or may extend over a substantial area and involve a considerable (and possibly unknown) number of exposures?

2.

If on class (1-a), it usually is desirable to secure information pertaining to the exposures and circuits in considerable detail.

3.

If the class (1-b), more general information is usually sufficient - e.g. single line diagrams and geographic layouts of the power transmission system, and general descriptions of the communications system giving the locations and rough dimensions of exposures but not going into much detail on either system.

4.

Regardless of the general class of the problem, complete information on the power and communication systems in the vicinity of important sources of harmonics or at points of high influence on the power system should be secured.

D-14 Influence, Coupling and Susceptiveness: In all investigations it is of primary importance to keep in mind that every noise induction problem involves consideration of three major factors, (a) the inductive influence of the power system, (b) the coupling between the power and communication lines, and (c) the susceptiveness of the


Part 20.1.8 communication system. Each of these major factors depends in turn on several other factors, which are briefly noted below. Figures 2018-5, 2018-6 and 2018-7 show schematically the factors involved in three cases.

D-15 The inductive influence of a power circuit in an exposure is determined by the magnitudes of the harmonic currents and voltages present on the circuit. Since the inductive coupling between the power and communications circuits is different for currents or voltages associated wholly with the power line phase conductors (balanced components) than for those components of current or voltage involving the ground (residual or ground return components) it is convenient to consider the two sets of components separately. This separate consideration should not be allowed to obscure the interdependence of balanced and residual (or ground return) components. For example, a ground return component of current often results from the effect of a balanced voltage impressed on a power circuit having an unbalanced impedance-to-ground. D-16 Figure 2018-5 shows in simple the various portions of a power transmission system as it is generally considered from the noise coordination standpoint. A transposed, (or even the usual un-transposed) three-phase transmission line is ordinarily well enough balanced to ground so that harmonics originating as balanced components in generators, three-phase transformer banks or loads are largely confined to the phase conductors. However, triple harmonic components originating in grounded neutral generators directly connected to the transmission circuit (ER-12), or in grounded neutral transformer banks not equipped with large capacity delta* windings, are directly impressed on the circuit as residuals. The majority of important noise problems involving exposures to transmission lines are caused by triple harmonic residuals.

*

For two-winding or three-winding transformers, at least one-winding connected delta.


1997

D-17 Figure 2018-6 shows a schematic diagram of a power distribution circuit and exposed communication plant that consists of aerial cable. Ordinarily a distribution system feeds a substantial portion of single-phase load and is inherently unbalanced to ground, because of the unequal lengths of line associated with each phase. Consequently non-triple harmonic residual components arising in single-phase load transformers, or as a result of balanced impressed voltages acting on unbalanced system impedances to ground, may be as important as, or more important than, triple harmonic components. (Under these conditions the usual distinction between triple and non-triple components loses much of its significance.) There are usually many load transformers and loads connected to a distribution system and each of these is a potential source of harmonics. Consequently, the influence of a distribution system is affected by many more factors than that of a transmission circuit connecting a point of generation with a load. D-18 In Figure 2018-5, two separate components of coupling are shown between the power line and an exposed open wire communication line. Induction into an exposed communication line is primarily longitudinal (Section B of Manual Part 7-7) and direct metallic induction may be considered as the difference between the unequal magnitudes of longitudinal induction that act on two communication wires at different spacings from the power line. It follows that if induction into the two wires is equalized either by properly coordinated transpositions or by keeping the two wires of the pair close together (as in cable or drop wire, etc.), the effects of direct metallic induction can be made very small even though the longitudinal voltages (between wires and ground) and longitudinal currents (flowing in the wires with ground return) will still be present and will act on any series or shunt unbalances in the communication circuit or terminal equipment to produce metallic circuit noise. D-19 The magnitude of the coupling for either direct metallic or longitudinal induction depends upon the exposure length and the separation between the power and communication lines. Coupling for ground return currents also depends upon the distance of the ground return path below the power phase wires, but this is generally assumed as 400 ft. (200-ft. ground plane) in noise induction problems. Occasionally


Part 20.1.8 cases may arise in which the coupling in fairly wide separation exposures (say 100 ft. or more) is considerably greater than would be indicated by a 200-ft. ground plane, but there appears to be very little advantage in trying to precisely evaluate the depth of ground plane in such cases since coupling computations are usually made only in connection with preliminary noise estimates and there are other factors which have a greater effect on the precision.

Figure 2018-5: Schematic Diagram Illustrating Factors in Noise Induction Problems, Power Transmission Line and Exposed Open-Wire Communication Line


1997

Figure 2018-6: Schematic Diagram Illustrating Factors in Noise Induction Problems, Power Distribution Circuit and Exposed Exchange Telephone Line in Aerial Cable

D-20 As shown in Figures 2018-5, 2018-6 and 2018-7, the susceptiveness of a communication circuit depends upon the overall effect of the transpositions (ER-16 and ER-17) (in the case of open wire) and upon the series and shunt balance of the line and on the balance of the terminal equipment. Ordinarily the design of long distance circuits in open wire and cable and of their associated terminal equipment is such that good balance should be secured. However, unless care is taken to insure that terminal apparatus is in good condition and is properly connected to the circuit, and to insure good line conditions, circuit balance may be a controlling factor in the noise on these circuits.


Part 20.1.8

Figure 2018-7: Schematic Diagram Illustrating Factors in Noise Induction Problems, Power Distribution Circuit and Exposed Communication Lines in Open Wire and Cable

D-21 Referring to Figure 2018-6 the susceptiveness or balance of equipment is generally of primary importance for local circuits in cable since the series and shunt unbalances of cable pairs are usually small. There is a wide range in the susceptiveness of different types of equipment (ER-46). There are two ways to reduce the effect of unbalances in equipment, viz.: 1. To replace it with equipment of less susceptive types, and 2.

To reduce the voltage to ground impressed upon the equipment or the longitudinal current in it, as by drainage or longitudinal chokes.

The use of longitudinal chokes or drainage in individual circuits has the disadvantage (as compared to general changes in the type of office equipment) that close supervision and care must be exercised in connection with growth and changes in order to maintain good noise conditions. However, in some cases these arrangements form part of the best engineering solution. In many cases the longitudinal induction on cable pairs may be reduced by means of cable sheath shielding (ER-43).


1997

D-22 Figure 2018-7 illustrates the factors to be considered under conditions often encountered in the field involving circuits in open wire and cable. In addition to metallic and longitudinal induction, the diagram emphasizes the possibility of secondary induction from certain cable pairs - which are connected to exposed open wire extensions - into other pairs which do not have such extensions. A similar situation may exist when open wire telephone circuits are connected into a cable. D-23 Overall Influence and Noise Measurements and Harmonic Analyzes, Test Program: All test programs are usually directed toward securing data on existing or potential noise situations and on the coupling, influence and susceptiveness factors which contribute to that noise. Such a test program will generally include noise measurements (metallic and to-ground or longitudinal), measurements of power system influence and of the effects of changes (if any) in the coupling. D-24 Planning an adequate but not too elaborate test program presents one of the most important, and most difficult problems to the coordination engineer. No substitute has been found for good judgment based on experience in laying out such a program. A few general principles based on experience which may be helpful are listed below. 1.

Determine what questions require answers concerning noise, influence, coupling, and susceptiveness. Pertinent questions are likely to remain unanswered regardless of how much data are accumulated unless the purpose of the tests is clear-cut.

2.

A test or series of tests should be made which will answer each of the questions in the most direct and simplest manner practicable. Wherever a direct measurement can be made, do not rely on an indirect one - and rely on computations only when a direct or an indirect measurement is not practicable.

3.

The test program should be flexible enough to take of new facts that may be discovered as the tests proceed. Care must be taken, however, to prevent being sidetracked from the main issues.


Part 20.1.8

D-25 Coordination of Power and Communication System Tests: Whenever practicable, it is desirable to carry on simultaneous measurements of power system influence and telephone circuit noise. The advantages of being able to tie together the effects of changes in the power and telephone system on the influence and noise will usually justify the extra personnel and apparatus required for such simultaneous measurements. Where it is impracticable to provide for simultaneous tests, it is often necessary to give considerable study to the factors which control the variations in the influence and noise over a period of time, as otherwise the test results are apt to lead to wrong conclusions. D-26 Variation of Influence and Noise with Time: A number of problems have been investigated in which it was found that a knowledge of the variations in the power system influence and resulting noise with time provided important clues to the solution of the problem. For example, in locating a source of harmonic distortion on a power circuit, such as a motor, it has been found advantageous to make records of the resulting influence or noise in order to determine the operating cycle of the particular motor as a clue to its location. Likewise, there are many cases where the influence of the power circuit varies considerably with the amount of load on the circuit (ER-40). In other cases it has been found advantageous to set up a recording arrangement at a particular point on a power system and then to survey influence or noise condition at other points using the record at the key point as an indication of any changes in conditions during the tests. Where recording equipment is not available for this purpose, it may be desirable to have an observer testing at the key point at all times when measurements are being made at other points. With such an arrangement it has been possible to solve several problems that had previously been investigated over long periods by a single test crew without success. D-27 Noise Estimates vs. Measurements: In connection with noise estimates (ER-16 and ER-17) following the principles outlined in the introduction to this section, computations of noise should never be used in place of measurements, where tests are practicable. Estimates of noise metallic are likely to be unreliable unless a great deal of information is available on power system influence, coupling and susceptiveness, most of which must be obtained


1997

by measurement. On the other hand, computations may be very helpful in estimating the contributions of various types of induction or of particular communication plant unbalances to a known (measured) overall noise. Power Systems D-28 Types of Situations Likely to be Encountered: Several different types of inductive coordination problems may confront the engineer and the procedure in determining the power system influence will vary accordingly. For example, it may be desirable to investigate the effect of some known change in power system operation, such as the conversion of a power circuit from one type of operation to another or the addition of a new generator or piece of load equipment. In this case it is ordinarily desirable to start the investigation at the point where the change has been made, or where the equipment is being added, although it should not be concluded if conditions are satisfactory there that the same is necessarily true at all other locations. On the other hand, the noise problem may arise from some unknown cause and it is often impossible to determine by discussions with the power company exactly what change or changes might be responsible. This particularly is difficult when a number of changes in operating conditions occur over a short period in both the power and communications systems. A change in power system operations that is responsible for a change in influence and noise may well be one that seems to have little significance to the power people, who naturally view their system primarily from the point of view of supplying power. For example, in one case it was found that a short length of distribution feeder had been disconnected from one source of supply and connected to another. The addition of this length of line to the second system changed its impedance characteristics and introduced a condition of resonance, which was responsible for a substantial increase in influence and noise. In cases like this the investigation of power system influence should commence in the exposure section and work toward the source of harmonic distortion or the cause of the condition of resonance. D-29 Direct Measurements of Power System Influence: Where suitable current and potential transformers are available for measuring the influence of the harmonic currents and voltages on the power system they should be used in preference to any less direct method of test. Such


Part 20.1.8 transformers are ordinarily available at generating plants, substations and at the points where fairly large loads are located. However, the instrument transformer connections that are ordinarily used for metering and relaying a power circuit, may not be the most advantageous arrangement for use in investigating the inductive influence of the power system.

D-30 Exploring Wire Methods: The development of exploring wire methods (ER-20) for measuring the influence of a power system within the exposure section of interest, has provided a valuable tool for noise induction studies. These methods are comparatively simple and yield results that indicate the influence at the desired point as well as the relative importance of the various harmonic components. Nearly all the recent investigations of complicated problems have depended to a considerable extent upon the use of these exploring wire methods. The probe wire method used for measuring the ground return IT product of a power line is the most useful of these arrangements. Effective use has also been made of a loop of about 300 turns of wire wound on a form 2 ft. or more in diameter for rapid qualitative exploration of the harmonic currents present at different points along a power line. (ER-20.) D-31 Interpretation of Results: When the results of the overall power system influence and the supplementary harmonic analyses are available, they should furnish the answers to the following questions: 1.

Are the overall influence factors (balanced KvT, residual KvT, balanced or phase IT, ground return IT) in line with those to be expected in the light of experience with similar types of circuits or apparatus elsewhere? (ER-12, 15, 22, 40, 49.)

2.

If any of the influence factors are substantially higher than those observed in other cases, what are the controlling frequencies?

3.

What apparatus or circuit conditions are responsible for these harmonic components? Have any additions or changes been made recently?

4.

What further data or tests are necessary to determine whether it is practicable to improve the influence?


1997

This does not mean that the best overall solution to the problem will necessarily include a reduction in power system influence. However, if the influence is high, the available methods of reducing it should be known before attempting to reach a t decision as to the best solution. D-32 In connection with obtaining the answer to the third of these questions from the available data, the following tabulations of the harmonic components that may arise from different causes may be helpful. Components Controlling Influence

Possible Cause

One (or two adjacent) odd non-triple harmonics.

Balanced harmonics from generator or synchronous motor or condenser. (ER-15)

Same but components not exact odd harmonics of fundamental.

(a) Balanced components arising as slot harmonics of induction motors (ER-34) (These components are usually quite variable in cases where the motor is connected to a pump, grinding mill machinery, saw mill, etc.)

Same but components not exact odd harmonics of fundamental.

(b) If exposures are to dc trolley systems, components* Having such frequencies may be arising as slot harmonics of the dc generators and also as "even" tap harmonics of rotary converters. (ER-21) (*Manifested as residuals in the case of "rail-return" dc trolley systems.)

All odd harmonics up to about 3,000 Hz.

"Out Lamp" on series street lighting circuit employing individual lamp transformers.


Part 20.1.8 Components Controlling Influence Relatively long "string" on prominent components, that may include "even" as well as "odd" harmonics.

Possible Cause Components arising in electrical devices containing saturable reactors, in sodium vapor lamps, in "single-phase" rectifiers, in "electronic" welders, induction heaters, frequency changers and portable saws.

One or more odd triple Direct connected grounded neutral harmonics. generator (ER-12) or motor or large transformer without adequate delta windings. All odd non-triple harmonics starting with 5th harmonic.

6-phase rectifier (ER-22).

Even harmonics 6, 12, 18, etc.

DC side of 6-phase rectifiers.

11th, 13th, 23rd, 25th harmonics.

12-phase rectifier (ER-22).

Pair of adjacent non-triple harmonics above the 23rd.

Multi-phase rectifier (ER-49)

3rd, 5th, 7th, and 9th Exciting currents of distribution harmonics. transformers (ER-40) possible aggravated by circuit resonance resulting from the presence of shunt capacitors (ER-50). Single outstanding component.

Possible resonance in balanced or residual circuit of power system (ER-23, 24 and 40). (May be due to shunt capacitors.)

D-33 Application of Remedial Measures: Measures that may be applied to reduce the influence of a power system may be divided into two general classes. The first class consists of measures, such as selective devices (ER-21 and 34) that are applied to particular generators or loads (such as


1997

motors or rectifiers) to prevent the flow of harmonics originating in these machines out on the power network to which the communication circuits may be exposed. Assuming that it is not practicable to replace or change the connections of the equipment so as to restrict the harmonics originating therein, the use of selective devices is ordinarily the most satisfactory and permanent method of reducing the effect of such sources on the power system influence. A second type of power system remedial measure involves the use of arrangements to change the impedance characteristics of a particular power circuit or system (ER-23 and 24) at harmonic frequencies in order to minimize the effects of harmonics arising from one or more sources. Examples of these arrangements include the use of wave traps in the neutral connection of a generator (ER-12) or of shunt capacitors (ER-40) at the point where a distribution system is supplied. Also use has been made of networks to terminate a resonant power circuit in an impedance approximating its characteristic impedance. The terminating arrangements have been tested experimentally in a number of cases and, in general, the results have not been as satisfactory as the use of comparable amounts of material to reduce the harmonic at the source, except in the occasional situation where an acute resonance condition exists on a particular power circuit and where the impressed harmonic components are relatively low. A remedial measure applied at or near the source of a harmonic is generally more desirable than one placed on a branch to relieve that particular branch. As long as the source is uncontrolled, it is apt to cause trouble at other points with existing conditions or in future exposures created by expansion of either or both systems. D-34 Where the overall results of the study indicate that arrangements to reduce the power system influence are a part of the solution, it is essential to keep in mind the reactions of such arrangements on the fundamental frequency supply problem and on components of frequencies other than those that they are designed to reduce. The reaction of such devices on power system operation can only be determined by the power people involved. Wherever practicable, therefore, the design of such arrangements should be left entirely to them.


Part 20.1.8

D-35 Coordinated Power and Communication Transpositions: The determination of the necessity of coordinated communication and/or power transpositions requires a full knowledge of the situation and the factors other than transpositions that are involved. There is no answer to the general questions "should a power line be transposed?" or "should communication transpositions coordinate with exposure irregularities?" except "it all depends on circumstances." D-36 The fundamental point which must be kept in mind in making a wise decision with respect to transpositions (or for that matter, almost any other specific measure) is, the fact that coordinated transpositions help to reduce noise does not mean that they are necessarily the right thing to use in a particular case. Before present investigation techniques, and present methods of controlling influence and susceptiveness were developed, there were many cases where about the only known procedure was to coordinate the transpositions and hope for the best. Nowadays, coordinated transpositions are like any other measures; they are good things to use only when the facts show that they form part of the best engineering solution - and like other measures they are not always good things to use unless the facts so show. Communication Systems D-37 The large majority of noise induction problems on telephone circuits involve open wire exposures. However, the general methods of attack for cable circuits are essentially the same as those for open wire circuits. The purpose of noise measurements and harmonic analyses on exposed telephone circuits is to obtain the answers to one or more of the following questions: 1.

What are the magnitudes of noise metallic and noise-to-ground on the overall telephone circuits under a particular power system operating condition, and what is the variation in these magnitudes over a period of time, or with specific changes in power system conditions?

2.

What harmonic components control the magnitudes of noise metallic and noise-to-ground on the exposed circuits?


1997

3.

What is the relative importance of unbalances in the outside plant and in the office equipment?

4.

If the noise arises primarily in the outside plant, do the unbalances in the entrance cables contribute to the problem?

5.

If the open wire is exposed to several different power lines, which exposure is controlling in the noise?

6.

Assuming that the controlling exposure has been located, is the noise due primarily to direct metallic induction inside the exposure (which may indicate inadequate coordination of the communication transpositions) or is it due primarily to the effects of longitudinal induction on unbalances outside the exposure?

D-38 A number of different kinds of measurements may be required to answer these questions. These are considered briefly below, approximately in the order in which they might be made in the usual type of investigation. Where two-type noise measuring sets which have been modified to include "FIA" line weighting are available, noise measurements with that line weighting will be included along with readings of noise with "144" line weighting. Experience indicates that only in the most complex cases will it be necessary to carry out the complete series of tests mentioned below. D-39 Overall Noise Measurements: One of the most important steps generally necessary in the early stages of the investigation of a specific noise frequency inductive coordination problem, is the carrying out of suitable overall measurements of noise metallic over the particular area concerned. One of the chief purposes of such overall measurements - as made at switchboards, or as expressed in of noise at switchboard level - is that their results serve as very helpful reference points and, as such, perform an important function in determining the overall effects of any changes (in the line of remedial measures, etc.) that may subsequently be made. Also, such measurements are in many instances needed to indicate the "geographical" extent of the particular noise problem concerned, as well as to show definitely the magnitudes of the noise. (Subsequent to the carrying out of these overall tests it will often, of course, be necessary to


Part 20.1.8 proceed with certain of the other type of tests which are outlined in Paragraphs D-41 to D-43.)

D-40 Where the overall measurements mentioned in Paragraph D-39 form (as they often will) a part of a cooperative study with a power company, it is desirable to include measurements of noise-to-ground in the repeater section where the exposure exists. The latter measurements must be made on the line side of the repeating coil group associated with the circuits. Ordinarily this involves interrupting at least the voice frequency circuit on the phantom. Where a number of noise-to-ground measurements and harmonic analyses are to be made, it has been found convenient to bring out temporarily the midpoint of the line side of the phantom coils (or side circuit coil in the case of non-phantomed circuits) to a special jack (such as a spare testboard jack) and to measure and analyze from this point to ground. With this arrangement, the testing is simplified since it is not necessary to take any circuits out of service for noise-to-ground measurements. D-41 "Condition" Tests: Before proceeding with noise measurements to determine which portion of the outside plant or which power line exposure is the controlling factor in the noise, it is essential that the condition of the telephone circuits be investigated. These condition tests include measurements of insulation and resistance unbalance. If these tests indicate abnormally high leakage or high resistance ts, the next step obviously is to locate and remove these conditions. In making such tests it should be recognized that certain jack s or intermediate connections which are in the circuit during its normal operation may be removed from the circuit as a result of the measuring arrangements which are used during tests (such as at the line jacks). Where unbalances in the outside plant are found to be small, the possibility of unbalances in the jacks and wiring between the main frame and equipment should be investigated before proceeding with detailed tests on the outside plant. In the case of individual phantom groups, measurements of the side-to-own-phantom voice frequency cross talk will often give a useful indication of the general condition of balance of the respective groups. D-42 "Location" Tests: In some cases, the test data obtained up to this point in the investigation will not give a clear


1997

indication as to just which of several exposures may be controlling. There are three general ways to find out. 1.

Make "sectionalized" tests on the communication line. In some cases, this may require merely "general" sectionalization (that is, cutting all wires in the lead at perhaps only two or three points), while in occasional instances the conditions may be such as to warrant cutting the lead into several fairly short lengths (each of which embraces only one exposure). This measure should be used only "as a last resort." It is essential for these tests that all grounded or simplexed telegraph circuits be cut at the locations where the telephone circuits are cut. This is to eliminate the possibility of secondary induction into the telephone circuit from any telegraph circuit that may extend through the exposure.

2.

De-energize the power lines, one at a time, and observe the results; recommended only for special cases.

3.

Measure the influence (particularly the harmonic voltages and currents) on each of the power circuits concerned (ER-33) (ER-20) and correlate the results with the measured noise and harmonics in the communication circuits (ER-16, 17, 20).

Of these, the method (or combination of methods) that is best for any particular case will depend upon the circumstances. It frequently will be found, however, that the comparison of influence and noise (method "3" just above) will involve less difficulty and net effort than either of the other two methods, particularly where "exploring wire" tests (ER-20) are used. D-43 Influence Tests: The "influence" tests mentioned in Item "3" of Paragraph D-42 will include, for at least one point in each exposure: 1. Measurements of the voltage TIF and of the corresponding contributions of the various harmonic components of voltage - usually on the secondary of a convenient service transformer. 2.

A determination of the balanced and ground return IT and the controlling harmonics.


Part 20.1.8 For these latter measurements, the exploring wires described in ER-20 are often helpful (particularly in cases where direct measurement of some or all of these quantities, at a point in or reasonably near the exposure, is impracticable). In the case of high voltage systems, for example, such exploring wires may be the only practicable means of securing the desired data on influences. A comparison of these "influence" results (Items 1 and 2) with the results of measurements of noise-to-ground (and frequency analyses thereof) at the adjacent testboard will usually indicate the exposure (or exposures) for which further consideration is warranted.

D-44 As mentioned in Paragraph D-24, it is often desirable to have simultaneous measurements of influence in the exposure and of noise-to-ground at the testboard, particularly if the noise is found to be variable with time. D-45 If the influence in the controlling exposures is relatively high, as compared with other similar exposures, the next step is to determine the controlling sources of harmonics or the particular power system impedance conditions responsible, as outlined under Power Systems. It may also be desirable to make tests to indicate whether the noise is controlled by direct metallic induction within the exposure (which might be reduced by improving exposure transposition arrangements) or results from longitudinal induction acting on unbalances outside the exposure section (which might be improved by suitable maintenance work or perhaps by retransposing certain of the communication line sections outside the exposure). (ER-16, 17) D-46 Sectionalized Tests: If it so happens that the noise on only one or two phantom groups on an open wire line stands out above the average, the relative importance of direct-metallic induction and longitudinal induction may usually be determined by noise measurements with this particular group (or groups) sectionalized at each end of the exposure section. It is usually necessary to open all grounded telegraph circuits including simplex circuits. This method of test has the advantage that it does not require complete interruption of service on the line, such as is required for completely sectionalized noise tests or measurements of current balance ratios. On the other hand, if several of the phantom groups have high noise values, or if it is found impracticable to determine the relative


1997

importance of electric and magnetic induction in contributing to the noise by means of exploring wire tests, it may be necessary to make completely sectionalized noise tests, possibly supplemented by measurements of current balance ratios. Experience has shown that it is necessary to resort to these detailed tests (which involve complete interruption of service over the line, including carrier and telegraph circuits) in only a very small percentage of the noise problems encountered. It is almost always desirable to exhaust all of the testing methods outlined above before resorting to sectionalized tests, at least on important lines. D-47 Remedial Measures: A number of measures, which include the following, have been used to improve the susceptiveness of exposed telephone circuits. 1. Removal of series unbalances caused by high resistance ts in open wire or cable. 2.

Removal of shunt unbalances caused by defective insulators, s with tree or guys, dusty carbons in protectors or unbalanced cable pairs.

3.

Improvement in balance of office equipment, such as office cabling, repeating coils, telegraph composite sets, carrier filters, etc.

4.

Improvement in communication transposition layouts inside exposure section to reduce direct metallic induction.

5.

Improvement in communication transposition arrangements in unexposed sections (particularly the older type transposition sections or incomplete sections) adjacent to exposures to improve overall balance of communication line to longitudinal induction.

6.

Increase in transmission levels (on repeated circuits) to improve signal-to-noise ratio inside exposure (See Paragraph C-10.)

7.

Drainage of longitudinal circuit (usually by grounding midpoint of line side of phantom repeating coils) to reduce voltage-to-ground across terminal equipment that may have unbalances to ground. Such drainage may


Part 20.1.8 also result in some longitudinal shielding from magnetic induction. Overall improvement in noise will result only where series unbalances are small. 8.

Isolation of longitudinal circuit in exposed and unexposed sections by use of repeating coils. Such arrangements are undesirable from standpoint of dc telegraph and carrier operation and dc testing.

9.

Drainage at ends of exposed section to prevent longitudinal induction from acting on adjacent unexposed sections. In the one case where this device was employed, the drainage arrangement was made more effective by tuning the capacitive reactance of condensers (in series with the drainage coils) to resonate at a particular frequency, using an auxiliary reactor in the ground connection. The specific case just mentioned involved a relatively light telephone line and required special design work and an appreciable amount of experimentation. In any specific situation it would be necessary, in deg such a device, to guard against any adverse resonance effects which might otherwise occur between the device itself and the line impedances. The use of such a low impedance termination might, of course, tend to result in increased noise (particularly at, or in the vicinity of, its tuned frequency) in cases where important series unbalances are present in the communication circuit. On the other hand, the effects of the noise voltage-to-ground acting upon ittance unbalances-to-ground might be expected to be decreased. It is expected that this device would have but little general application in practice, as compared with other available methods.

10.

Reduction in noise metallic by use of a sharply tuned resonant shunt across the metallic circuit at offices adjacent to the exposure to reduce the effects of a single outstanding component of induction. Experimental work indicates that such noise reductions are technically possible. However, it may be noted that this measure also reduces the speech signal somewhat and may affect the intelligibility. In addition, on repeated circuits or circuits which may be used as links in a built-up connection involving repeaters, consideration would have to be given to the


1997

matter of impedance irregularities, a factor which would tend to produce adverse effects such as singing echoes or false operation of voice-operated devices. For these and other practical reasons it has generally been found preferable to reduce the induction-or its effects-by some other method. It is therefore expected that this device will have little practical application to voice frequency telephone circuits. D-48 Cable Sheath Shielding: The lead sheath of a communication cable provides practically perfect shielding against electric induction (from power system voltages) when it is grounded at one or more points (provided, of course, that the sheath is electrically continuous between the points at which it is grounded). The sheath also provides substantial magnetic shielding when it is grounded more or less continuously, as in underground construction, or is grounded at both ends of an aerial section or near both ends of an exposure. The degree of magnetic shielding increases with the frequency of the induction and is also dependent on the size of the cable, type of sheath and on the resistance of the ground connections. These relationships are illustrated in Table 1. (See also ER-48.) From this tabulation, it is evident that low resistance sheath grounds are required if the maximum benefits from shielding are to be obtained. This is particularly true for the shorter exposures involving large size cables. A low resistance ground may generally be obtained at the end of the cable nearest the office by bonding the aerial and underground cable sheaths. At points on the cable remote from the office, it has long been the practice to obtain a low resistance ground by bonding the cable sheath to the water system, where feasible. More recently it has been found that fully as effective shielding can usually be obtained by bonding the cable sheath to the multi-grounded neutral of the power distribution system (ER-43). This method of bonding is generally more convenient than a connection to a water pipe, and can ordinarily be arranged with the power company. Intermediate grounds generally do not provide appreciable additional shielding for communication circuits extending throughout the exposure, except for power faults within the exposure or where the end grounds are high in resistance and intermediate grounds of much lower values can be obtained. As may be noted in Table 1, the shielding provided by aluminum plastic sheath is not quite so good as


Part 20.1.8 lead sheath, especially for the larger size cables where long exposures and low resistance grounds are involved. The column for zero ohm grounding resistance represents the maximum shielding condition and is the percent of remaining voltage which is approached by a long exposure where the grounding resistance is negligible compared with the total sheath impedance.

D-49 Cable sheath shielding is effective only when the cable sheath is electrically continuous between the points where grounds are applied. When tests are being made to determine the effectiveness of shielding, it is necessary to strap out any insulating ts and to make low resistance connections between the sheath and ground. In some situations, grounding the cable sheath at two or more points may react adversely on electrolysis conditions, and it may be necessary to insert an electrolytic condenser in series with the ground connections or in the sheath-to-power system-neutral bond. This is discussed in detail elsewhere (ER-43). Presentation of Test Results D-50 A carefully planned and clearly worked out report of the test results and the conclusions which are indicated by these results is an important part of a noise investigation, particularly where the studies have been made tly with the power company. Wherever practicable, the report should be prepared tly by the representatives of the power and railroad companies who actually participated in the tests and should be submitted for comments to others interested before being put in final form. Where circumstances make it necessary for the railroad company representatives to prepare the initial draft of the report, the power company engineer should be given an opportunity to review the plan of the report in the early stages and to comment freely before a final draft is prepared.


1997

TABLE 1 Magnetic Shielding for Various Frequencies Sizes and Lengths of Communication Cables and Various Grounding Resistances Expressed as Percentage of Remaining Voltage to Original Voltage with no Shielding (Calculated Values of er/ei x 100) (ei =Voltage present with sheath grounded at one point only) (er =Voltage remaining after grounding sheath at both ends)

Frequency Hz 60 180 300 420 540 660 1,000 2,000

60 180 300 420 540 660 1,000 2,000

60 180 300 420 540 660 1,000 2,000 * **

Outside Diameter 2.6 Inches Outside Diameter 1.7 Inches 1 Mile** 3 Miles** 1 Mile** 3 Miles** 0 ohms* 5 ohms* 10 ohms* 5 ohms* 10 ohms* 0 ohms* 5 ohms* 10 ohms* 5 ohms* 10 ohms* LEAD 44% 96% 98% 85% 93% 66% 97% 99% 89% 94% 17 81 93 52 71 30 83 93 59 74 10 67 85 36 54 19 69 85 41 57 7.6 55 77 27 43 14 57 77 31 46 6.0 47 69 23 35 11 48 70 25 38 5.0 40 63 19 30 9.0 42 63 21 33 3.4 29 48 12 21 6.2 30 49 15 22 1.8 15 28 6.4 11 3.3 16 28 7.6 12 LEAD Outside Diameter 0.9 Inch ALUMINUM PLASTIC Outside Diameter Approximately 1.2 Inches 88% 99% 99% 97% 99% 56 94 97 87 94 39 87 94 74 87 29 79 91 63 79 24 72 87 54 72 20 66 82 48 66 13 51 72 35 51 7.1 30 48 19 30 Outside Diameter Approximately 2.8 Inches Outside Diameter Approximately 1.9 Inches ALUMINUM PLASTIC 67% 97% 99% 89% 95% 78% 97% 99% 91% 95% 31 84 93 60 75 41 85 93 65 78 20 70 86 43 59 27 71 86 47 61 15 59 78 33 47 20 60 78 36 50 12 50 71 26 40 16 51 72 30 42 9.7 43 65 22 34 13 44 65 25 36 6.5 31 50 15 23 8.9 32 50 17 25 3.4 17 29 8.0 12 4.7 17 29 9.0 13 Refers to total grounding impedance (Approximate dc resistance) of the two ground connections - expressed in ohms. Refers to distances along cable sheath between the two grounding points.

D-51 The form and length of a test report will of course depend to a great extent on the complexity and importance of the situation under consideration. In every case, however, the history of the problem and a brief description of the plant involved, as well as the outstanding results and conclusions, should be included in the first few pages,


Part 20.1.8 with confirming data and details following, where necessary. A brief report that is well organized and easy to follow is better than a longer report which must be read through completely before the problem becomes clear.

D-52 When the investigation includes many harmonic analyses of wave shape and noise, it will be desirable to tabulate the detailed results as attachments to the report and to include brief summary tables in the body of the report along with the discussion. These summaries might include only the overall measured power system influence and noise, together with the contributions of the important harmonic components. Comparative data taken under different test conditions should be included in the same tabulation wherever feasible. It is well to that a little time spent in organizing and summarizing the material in the report may easily save considerable time for those reviewing the report. D-53 Maps and circuit schematics are usually helpful in indicating the general layout of the power and communication facilities under consideration. Wherever practicable, the power and communication system layouts should be shown on the same drawing. Also, use can often be made of graphical methods of presenting the test results. In particular, the results of noise measurements on a number of exposed communication circuits under different power system operating conditions can be shown in a series of cumulative percentage curves on the same background. A number of different methods of drawing such curves have been developed. In the interest of uniformity it is suggested that the scheme shown in Figure 2018-8 be adopted where practicable.


1997

Figure 2018-8:

D-54 The following paragraphs briefly describe the purpose of some of the more important types of testing apparatus used in noise coordination studies. D-55 Noise-Measuring Sets: The 2A and 2 B Noise Measuring Sets are self-contained portable visual-indicating devices for measuring noise. These noise-measuring sets include: 1. Weighting networks to enable the measurement of noises of different frequencies in of their noise effects. 2.

Amplifiers to raise the level of the noise currents to measured sufficiently to operate an indicating instrument.

3.

A copper oxide rectifier and a rugged output meter on which the visual indication is obtained.


Part 20.1.8 4.

A graduated gain control permitting measurement of a wide range of noise magnitudes.

5.

Input coils and switching arrangements to facilitate the various measurements.

6.

Self-contained calibrating means.

7.

Self-contained dry-cell battery supply.

8.

A means for monitoring under all test conditions.

D-56 Harmonic Analyzers: The 10-A Noise Analyzer Attachment is an adjunct to the 2Type Noise Measuring sets to provide a visual indicating arrangement for measurements of individual harmonic components of noise or power system influence in the range from 180 to about 4,000 Hz (or higher under special conditions.) The frequency selectivity, sensitivity, freedom from the effects of external fields, and other operating characteristics of the analyzer attachment –noise measuring set combination have been found satisfactory for most of the noise coordination problems which are apt to be encountered. It is impossible to overemphasize the importance of harmonic analyses of power system influence and noise in arriving at the solution to a noise coordination problem. D-57 Couplers for Power System Influence Measurements: The same noise measuring set and analyzer which is used for noise tests may also be used for measurements and analyses of power system influence is auxiliary apparatus (mentioned in paragraphs D-58 and D-59) is used for connections to the power system. D-58 The current TIF coupler (per D-99127) consists chiefly of a low impedance (0.4 mh) retardation coil, together with a 605-ohm resistance. These and the binding posts of the coupler are so arranged as to facilitate connecting the retard coil in series with the secondary of a current transformer inserted in the power circuit under test, while the analyzer and/or noise measuring set in series with the 605-ohm resistance is connected across the retard coil (via the “To Set” binding posts) of the coupler. Because of its low impedance (j0.15 ohm at 60 cycles) on the “To C.T.Sec.” side, this coupler has no effect on any metering or


1997

relaying equipment that is normally connected to the secondary of the same current transformer. The inductive reactance of the retard coil, in conjunction with the “line” weighing curve of the noise measuring set, provides the proper frequency weighting curve for measurements of IT product. D-59 Similarly, the voltage TIF coupler (per D-00128) consists essentially of a small condenser (0.01 mfd) in series with a 605-ohm resistance. This coupler is so arranged that the analyzer and/or noise measuring set can be connected across the 605-ohm resistance. By this means, the device serves to couple the input of the analyzer or noise measuring set to the power voltage (secondary of service or potential transformer). On the “power voltage” side, the impedance of the coupler is controlled by the high impedance of the 0.01 mfd condenser (265,000 ohms at 60 Hz) and therefore has no effect on any metering or relaying equipment that might be connected to the same transformer secondary. In this case the capacitive reactance of the condenser and the “line” weighting curve of the noise measuring set provide the proper frequency weighting for measurement of the KvT product. D-60 Current and Potential Transformers: Measurements of power system influence and supplementary harmonic analyses may be made on the secondaries of current and potential transformers normally employed for metering and relaying or, in special cases, on specially installed transformers. In the latter case, the current transformers may be connected directly in series with the circuit under test or may be of the clamp or “split core” type. D-61 Miscellaneous Equipment: In addition to the apparatus already mentioned, a variety of other testing equipment and special terminating arrangements may be required in noise coordination work.


Section 21 – Data Transmission 2002



Index

SECTION 21 - DATA TRANSMISSION Part

C

Type & Subject

21.1.1

35-3

Recommended Functional/ Operating Guidelines for Telephone Transmission

19

Extended 2001

Recommended Functional/ Operating Guidelines for Analog Data Transmission Over Voice Channels

12

Extended 2001

21.1.2

35-3

Pages

Status

______________________________________________________________ -1Note: C =




Part 21.1.1 Recommended Functional/Operating Guidelines for Telephone Transmission Extended 2001 (19 Pages)

A.

General Requirements 1. Telephone System: The primary function of a telephone system is to provide for the transmission of information (including speech, data, graphics, video, etc.) with sufficient faithfulness, received level and freedom from extraneous noises to be readily usable, and to provide a satisfactory means of signaling. To attain this objective, the equipment and line facilities must be suitably designed, installed and maintained. The actual results depend to a considerable extent on how the system is used, but as the use is largely beyond the control of the communications engineer the following sections deal only with design and maintenance. 2.

Telephone Transmitter: The telephone transmitter is a means for translating acoustic vibrations into electrical current variations. A transmitter widely used accomplishes this by varying its resistance in accordance with variations of the sound pressure. That part of the transmitter whose resistance is subject to variation is the carbon button and consists of a small sealed chamber partly filled with granular carbon through which direct current es when the telephone set is used. When the transmitter diaphragm vibrates in response to speech, the resistance of the carbon button is varied which in turn varies the direct current. These latter variations are in effect alternating current and constitute the speech currents transmitted over telephone circuits. The telephone transmitter introduces some frequency distortion because its electrical output is not uniform over the entire speech range for a given input energy. The transmitter also introduces some frequencies other than those impinging upon the transmitter. This latter type of distortion is noticeable only when the transmitter is overloaded due to too high talking volumes. Offsetting these disadvantages is the fact that the carbon transmitter is a very effective amplifier, that is, the electrical energy in the output is many times that of the acustic energy impinging upon the transmitter diaphragm.

- 2 – AREMA C&S Manual Part 21.1.1 3.

2001

The efficiency of a transmitter decreases rapidly as the distance between the speaker’s lips and the transmitter increases. If this fact were more widely appreciated and more care taken to use the instrument correctly the average grade of transmission would undoubtedly be considerably improved, and many cases of extremely poor transmission eliminated. Figure 2111-1 shows the decrease in transmitter efficiency as the distance between the mouthpiece of the transmitter and the lips of the speaker is increased. The curve is based on average results from tests on local battery instruments of some half dozen manufacturers.

Figure 2111-1

Transmission Loss Due to Talking at Various Distances from Transmitter Mouthpiece (Average of Several Types of Local Battery Transmitters)


Part 21.1.1 4.

Telephone Receiver: The function of the receiver is the opposite of the transmitter since it is actuated by the alternating electric currents and delivers acoustic waves. This is accomplished by the variation in pull on the diaphragm by the electromagnet that is energized by the line current. As in the case of the transmitter, the quality characteristics of the receiver are dependent upon both its electrical and its mechanical performance.

5.

Telephone Sets: A telephone set is a combination of receiver and transmitter and is associated with a subset which contains an induction coil, usually a ringer, and in some cases, other equipment. The battery supply for the transmitter may be from local batteries or from a common battery source. In the latter case, the transmitter current flows over the same conductors as used for speech transmission.

6.

Common-Battery Sets: "Anti-sidetone" circuits are now standard for common-battery telephone sets. In the older circuits high side-tone in the speaker's ear often caused the to unconsciously lower his voice. Furthermore, room noises were amplified in his ear when he was listening. Both of these conditions, in effect, degrade transmission. Anti-sidetone sets employ a balancing arrangement that eliminates the speaker's voice from his own receiver. The degree of balance obtainable varies with frequency and with impedance of the connected line. The balance cannot, therefore, be perfect but it is generally good enough to provide performance quite superior to the older side-tone sets.

7.

Local-Battery Sets: These are two general types of local-battery sets. One type uses a push button (or foot switch) to cut the transmitter into the circuit only when the is actually speaking. Sets of this type have inherently good transmission efficiency. They are especially useful where more than two phones are bridged on a line simultaneously because they have a low bridging loss and because transmitter background noise is eliminated from all but the one set being used by the speaker at any given instance. Sets of this type are almost universally used on dispatching circuits.


B.

2001

8.

The other type of local-battery set employs a transmitter circuit that is continuously closed when the set is in the "off-hook" condition. Such sets are quite satisfactory on lines normally used by only two people at any given time. The use of this set is simpler for those not accustomed to "push-to-talk" sets.

9.

Telephone Circuits: The circuits between two telephone sets may be direct or may be switched at one or more points. The circuits may be physical or they may be derived. In any case it is necessary that speech be transmitted with adequate volume, sufficient faithfulness, and relative freedom from noise and crosstalk. In many instances these requirements can be met only by giving very careful consideration to the characteristics of the circuit facilities. Attenuation and noise levels are of paramount importance. Flat attenuation frequency characteristics and wide bandwidth (250-3,000 cycles) are desirable but must frequently be sacrificed where increased circuit capacity of a line is a requirement.

Types of Railroad Circuits 1. The following classes of circuits (based primarily on usage rather than design) are commonly found in railroad service: a. Trunk circuits.

2.

b.

Train dispatching circuits.

c.

Message circuits.

d.

PAX circuits.

e.

Yard circuits.

f.

PBX extensions.

g.

Block circuits.

h.

Party line circuits.

Trunk Circuits: A trunk circuit interconnects two switchboards. The switchboards may be miles apart and not infrequently are separated by hundreds of miles.


Part 21.1.1 Short trunks of a dozen miles or less are usually physical circuits. Longer trunks are generally derived circuits. A large, and constantly increasing, proportion of long trunk circuits are carrier derived. Signaling is either ring-down or dial depending on terminal use. 3.

Train Dispatching Circuits: Dispatching circuits are normally physical, although sections of carrier are not uncommon when the dispatcher is remote from the controlled territory. The dispatcher's circuit is a push-to-talk, local-battery party line. Selective signaling, employing individual impulse following selectors, is used outward from the dispatcher's office. The dispatcher is generally provided with an amplifier-loudspeaker set which eliminates any need for inward signaling.

4.

Message Circuits: These circuits are provided to interconnect all way stations on a district or division, and generally terminate in a railroad owned or leased private branch exchange switchboard. Signaling toward the switchboard is 20-Hz ring-down. Signaling outward from the switchboard is, by selectors, similar to those used on dispatcher circuits, by 20-Hz code ringing, or by a combination of both. Message circuits are almost universally of the local-battery type and usually use a common telephone set switchable between the dispatcher and message lines.

5.

Private Automatic Exchange (PAX) Circuits: Dial telephones are extensively used by railroads. Such systems do not differ essentially from those commonly used by other industries.

6.

Yard Circuits: Where PAX service is not available, yard communication is usually provided by a circuit connecting all principal points in the yard. It usually is of the local-battery, code-ringing type and generally does not terminate in a switchboard.

7.

Private Branch (PBX) Extensions: Wherever PBX service is provided, local phones are served by extension lines from the switchboard. These lines are common battery.


2001

They may be manually switched or may be a combination of manual and dial.

C.

8.

Block Circuits: Block circuits were provided to connect adjacent block stations, but sometimes were extended to connect several stations. Generally, they were local-battery, code-ringing, and do not connect to a switchboard. Block station eliminations have all but obsoleted this type circuit.

9.

Party Line Circuits: Some use is made of party line service on lightly loaded circuits extending from a single PBX switchboard to outlying points, or in some instances on semi-trunk circuits between two distant PBX switchboard locations. When such service is used the intermediate telephones (or PBX switchboard) are connected to the circuits on a bridging basis. Coded magneto ringing is generally used for signaling purposes.

10.

Miscellaneous Circuits: The list of circuits given under Paragraph B-1 is not exhaustive. Many other types of circuits are used in railroad service. Paging loudspeaker, talk-back loudspeaker, and office inter-communicating sets are examples of the many arrangements available.

Transmission Losses 1. Some of the electrical power input into a circuit is dissipated in the circuit due to line attenuation, reflection and equipment losses. These losses in the power transmitted over a circuit are termed transmission losses. Transmission losses are commonly expressed in of the attenuation or power ratio between the input and output of a circuit. The unit is the decibel (abbreviated "db") that is a logarithmic expression of the power ratio. The loss expressed in decibels in a particular case is P1 10 log ____ where P1 is the input power and P2 the P2 output or received power. Where the impedances are equal, I1 db equals 20 log___ I2

E1 or 20 log

where I1 E2


Part 21.1.1 and E1 are the input and I2 and E2 are the output current and voltage. 2.

The use of a logarithmic unit such as the db permits the direct addition of the losses in different parts of a circuit, or of the gains due to repeaters.

3.

Line Loss: Line loss, or attenuation, reduces the magnitude of the received power. The following factors affect line loss. a. Resistance: This is influenced largely by the size, material, and temperature of the line conductors. The unit of resistance is the ohm. b.

Leakage or Leakage Conductance: This is the shunt loss between the two conductors of the circuit. It is measured in mhos, and at low frequencies is practically the reciprocal of the line insulation resistance. Leakage, in open wire, depends on the number, type and condition of the insulators, foreign s such as trees, and upon weather conditions. At high frequencies, other factors are involved.

c.

Inductance: The series inductance of a circuit is the self-inductance of each conductor plus the mutual inductance between the individual conductors of the pair. The magnitude of the series inductance is dependent upon the material, size and spacing of the wires and the surrounding conductors. At a given frequency, the greater the separation of the conductors, the larger the inductance. The effect of inductance is dependent upon the imposed frequency. The unit of inductance is the henry.

d.

Capacitance: The shunt electrostatic capacitance of a circuit is the electrical capacitance between the two conductors of the pair including the effect of capacitance to earth. The magnitude of the shunt capacitance is dependent on the size, separation and dielectric material between the conductors, as well as the presence of surrounding conductors. With a given frequency and dielectric constant, the closer the conductors, the greater the capacitance. The


2001 effect of capacitance is dependent upon the imposed frequency. The unit of capacitance is the farad.

4.

Characteristic Impedance: This is the impedance looking into one end of a infinitely long uniform line. By definition, it is also the impedance of a uniform line of any length terminated in its characteristic impedance. It is dependent on the frequency and the four factors above noted in connection with line loss. It is measured in ohms.

5.

Reflection and Return Losses: When alternating currents traveling along a circuit encounter an impedance irregularity; i.e., from a circuit of one impedance to one of another impedance, a portion of the current or voltage is reflected and travels back toward the sending end. This loss in transmission through the irregularity is known as the reflection loss and in computing the overall loss in a circuit or connection these reflection losses are added to the attenuation losses. Expressed in of the line impedances looking in the two directions at the irregularity Z1 and Z2, the power reflection loss in db

equals 20 log

6.

Z1 + Z2 _______ 2Z1 Z2

The ratio of the reflected current to the current striking the irregularity is known as the return loss. The return loss is of principal interest in its effect on repeater balances and may be referred to the repeater by adding twice the attenuation loss between the irregularity and the repeater. This is then known as the "singing" point irregularity. The return loss in db equals Zn + ZL 20 log

where Zn is impedance of the network

Zn - ZL and ZL is impedance of the line. 7.

Insertion Loss: The complete effect of the introduction of a piece of equipment or line in a


Part 21.1.1 circuit is frequently considered in of its insertion loss. The insertion loss obviously includes both the reflection effects and the losses or gains in the device or line itself. The insertion loss is defined as a loss expressed in decibels of the ratio between the power received with the device or line not in the circuit and that received with the device or line inserted in the circuit. It should be noted that the result is frequently an insertion gain, particularly where a repeating coil of the proper ratio is inserted at a point of the junction of two lines of unequal impedance and existing reflection effects are reduced.

D.

Distortion 1. Attenuation-Frequency Distortion: Attenuation-frequency distortion may be defined as the distortion or modification of voice signals ing through a unit of apparatus or circuit of such a character that the attenuation of a signal is not the same at all frequencies. Such distortion results in unequal losses to the various frequency components desired for speech transmission and may seriously affect the intelligibility of the received signal. 2.

Frequency Distortion may be introduced into a circuit by station equipment, repeating coils and other apparatus, such as repeaters, if they do not have a satisfactory attenuation-frequency characteristic. Another source of frequency distortion is the line itself. Non-loaded open wire circuits are comparatively free from this form of distortion, but this is not true of cable facilities. Loaded cable facilities have a comparatively flat transmission frequency characteristic within the band for which the loading system is designed.

3.

Non-Linear Distortion: Non-linear distortion is the modification of signals ing through a unit of apparatus or a circuit in a manner such that the output of the unit or circuit is not proportional to the input. In other words, for a given change in input energy, where this type of distortion occurs, there will not be a corresponding and proportional change in the output energy. This effect may result in apparent changes in the transmission loss or gain


2001

of the circuit and results in the generation of harmonics and other undesired frequencies.

E.

4.

Non-linear distortion may take place in telephone transmitters or receivers where the conversion from mechanical to electrical signals, or vice versa, is not equally efficient for all energy values.

5.

Non-linear distortion may take place in repeating coils where these coils are operated at higher current levels than they are designed for or where, through abnormal use, these coils have become magnetized. The result is the generation of harmonics and the modulation of normal line signals, one upon the other, to produce undesired products of modulation.

6.

Non-linear distortion may occur in repeater equipment using analog amplifying circuits, producing distortion of the signal or extraneous noise when operated beyond rated input values.

7.

Delay Distortion: Delay distortion is the modification of signals ing through a circuit under conditions such that certain frequencies or groups of frequencies are delayed and arrive at the receiving end of the circuit after the remainder of the frequencies have arrived. This results in a phase relation between the frequency components of the received signal different from the relation in the original or transmitted signal. Delay distortion will seldom be apparent in railway voice telephone circuits. It is present in each unit of equipment and in each section of line, but is so small as to be negligible. When many of these units are connected in tandem to provide a circuit, the distortion may be sufficiently great to require attention if the circuit is used for purposes other than voice.

Interference 1. General: Although a system may be capable of transmitting speech with sufficient volume and with good quality, the presence of disturbing noises may detract from the intelligibility of the speech received and in some cases may make the circuit unsatisfactory. A small amount of noise may in effect be equivalent to an appreciable increase in


Part 21.1.1 transmission loss. Disturbing noises may be due to inductive disturbances, cross talk and other causes. 2.

Inductive Interference: Telephone noises can be caused by paralleling power circuits. Such noises may result from inadequate or uncorrelated transposition systems or from transposition errors. The effects of inductive disturbances are increased by line unbalance. Corresponding electrical quantities for the two sides of the circuit should be substantially equal at all points along the circuit; that is, there should be electrical symmetry of the two sides of the circuit. Unbalances may be due to fuses or heat coils of unequal resistance in the two sides of the line, high resistance in the line due to sleeve or other line ts, loose connections in equipment or wiring, unequal leakage in the two sides of the circuit, partial grounds in line or protectors, different gages of wire in the two sides of the line, or other causes.

3.

Crosstalk: Under this heading is classed the transference of voice frequencies from one circuit to another, which may be due to several causes, among which are induction between physical circuits or parts thereof, unbalance between the two sides of a phantom group, resistance and capacitance unbalances incapable circuits and a variety of defects in office equipment and wiring. Crosstalk may be caused by inadequate transpositions or by transposition errors in open wire circuits or by induction between improperly shielded repeating coils and relays. Excessive capacitance unbalances may be due to improper splicing of cable. High impedance battery leads may be responsible for a considerable amount of crosstalk.

4.

Other Noises: Besides disturbing noises traceable directly to inductive disturbances and crosstalk, room noises are often a source of disturbance. Room noise may be detrimental to intelligible transmission in several ways; it may interfere directly, it may be picked up by the transmitter and appear as sidetone noise in the receiver and thus affect transmission, or it may be transmitted to the other end of the line and interfere with received speech. Of the methods by which room noises may cause impairment of transmission, that of sidetone noise is the most


2001

detrimental and may be minimized by the use of transmitter cutouts and anti-sidetone sets. F.

Reference Standards 1. Volume Reference Standard: It is the practice in communication work to measure the speech volume level on a circuit by means of a device called a volume indicator. This instrument has clearly defined ballistic characteristic and pointer action that follows the variation in the speech wave in a determined suitable manner. 2.

The Standard Volume Indicator is calibrated to give a steady state reading of zero when a 1,000 Hz signal of one milliwatt is being dissipated in a 600-ohm resistance across which the instrument is bridged. Readings made with a volume indicator of this type and calibrated in this way are recorded as "+ X vu," where X is the number of db by which the speech volume level differs from the reference level of this meter.

3.

Transmission Testing Standards: In making transmission tests on telephone circuits it is the usual procedure to transmit a power of one milliwatt (0 dbm) into the line at the sending end. The power received at the other end is measured and its relationship to one milliwatt, expresses the transmission gain or loss of the circuit. Both ends of the circuit must be terminated in 600 ohms impedance or such other impedance as specified.

4.

Noise Reference Standard: A circuit noise meter measures noise in of the number of db by which the noise reading exceeds a certain reference standard. The communications industry has in the past used as the reference power level for noise measurements 10-12 watt, or 90 db below 1 milliwatt at 1,000 Hz per second. Measurements made in decibels above this reference level using a 144-weighting network were called dbRN or decibels above reference level. A practice has been to use F1A weighting based on the more sensitive F1A handset, and to use -85 dbm as the reference level. Measurements made with the F1A weighting network are designated as "dba" or decibels adjusted to differentiate between the old and new standard. With the 500-type set, a new weighting


Part 21.1.1 characteristic was found desirable. A new noise meter has reverted to the use of the original reference level of 10-12 watt, or 90 db below 1 milliwatt at 1,000 cycles. However, due to the difference in F1A weighting and the new 500 set, or C-message weighting the measurement made with the set should be designated as "dbRn C-Message" for purposes of differentiation.

G.

5.

Standard Crosstalk Unit: The crosstalk meter in common use is calibrated in of db and expresses the db loss between the transmitted power on the disturbing circuit and the received power on the disturbed circuit. These meters are also calibrated in of crosstalk units. These units express in one-millionths the ratio of the received current on the disturbed circuit to the transmitted current on the disturbing circuit. The crosstalk unit is abbreviated "dbx.". Reference coupling is that which produce 0 dba in the disturbed circuit when a test tone of 90 dba is impressed on the disturbing circuit. Both values of dba are for the same weighting.

6.

Reference Power Unit: The most common reference power used in communications work is the milliwatt. A convenient method of indicating an amount of power is to express it as being so many db above a reference power of one milliwatt. Because of its common usage, decibels above or below one milliwatt are usually abbreviated plus or minus dbm.

Line Facilities and Equipment 1. General: There are several aspects with regard to line facilities and equipment which involve transmission considerations of a type which it would be desirable to review in this section. This applies particularly to the use of loading and repeaters for improving the transmission performance of existing circuits and in deg new ones, and to the application of carrier systems for deriving new circuits. 2.

Loading: Loading coils are inductances that are inserted in telephone circuits at regular intervals to offset or counteract the effect of capacitance between wires. While loading was formerly applied to open wire circuits, other methods of reducing attenuation


2001

such as the use of repeaters have proven more economical and more reliable and at present the application of loading is restricted to cable facilities and long twisted pair runs. The purpose of loading is to reduce attenuation and to provide an improved transmission frequency characteristic. In addition, it is often desirable to load entrance and intermediate cables on open wire routes in order to make the impedances of the cable facilities substantially equal to the open wire, as well as reduce the attenuation and the variation of attenuation with frequency. This, of course, reduces line irregularities and permits the operation of repeaters at higher gains than might otherwise be possible. 3.

There are several loading systems commonly in use. Those systems that make use of the lower inductance coils and shorter spacings provide the higher cut-off frequencies. It is generally desirable to select systems that provide nominal cut-off frequencies of at least 2,900 Hz. For the longer cable circuits or cable circuits which may be used as links in long built-up connections it is particularly important to make use of the higher cut-off types of loading, such as H-44-25, H-88-50, B-88-50, etc., in order to avoid objectionable echo and singing reactions.

4.

In the case of toll entrance and intermediate cables in open-wire lines, the selection of loading usually involves a review of the several possible loading layouts that might be used. A number of systems have been worked out making use of full weight and fractional weight coils in combination for different lengths of cables.

5.

Cable facilities loaded for voice frequency systems will not satisfactorily transmit carrier frequencies. Where carrier systems are involved and loading is necessary, carrier-loading systems should, therefore, be used. These carrier-loading systems not only reduce attenuation but will also largely eliminate reflection losses at junctions with open wire. When cable pairs connect with open wire carrying both voice frequency and carrier it is sometimes necessary to separate the frequencies by means of filters and


Part 21.1.1 transmit the voice frequency over one pair and the carrier frequency over another. For best results each pair should be loaded for the frequencies that it is to .

H.

6.

Voice-Frequency Repeaters: Telephone repeaters are basically amplifiers and are employed to overcome excessive attenuation losses. Four-wire repeaters are relatively simple and are capable of high gain. Two-wire repeaters require hybrid-balancing arrangements that inherently make them much less stable than four-wire repeaters. Two-wire repeaters are easily unbalanced by changes in line impedance. If adjusted to produce high gains they are easily thrown into a feed-back, or "sing," condition.

7.

Depending upon their application, voice-frequency repeaters fall into two classifications: (1) Terminal and (2) Through-line.

8.

Terminal repeaters are often favored because of easier testing and maintenance of facilities at terminal points, but through-line repeaters generally yield better transmission gains.

9.

"Negative Impedance" Repeaters are finding some use on railroad cable circuits. They are designed to produce a phase shift which feeds more energy into the line than is drawn from it.

Carrier Telephone 1. Carrier: Carrier systems provide a means of communication through the use of frequencies above those of the normal voice circuit range. This is accomplished by apparatus at the circuit terminals which translate the voice frequencies received into carrier frequencies whereas at the opposite end the carrier frequencies are translated back into voice frequencies. The first of these operations is called modulation and the second demodulation. In the opposite direction of transmission the same thing is done but the carrier frequency band used on the line is different. For example, the band from 4,000 to 6,800 Hz may be used for transmission from the west to east direction and the band from 7,200 to 10,000 Hz used for the opposite direction of transmission.


2001

Filters in the carrier equipments prevent the carrier channels and voice circuit from interfering with one another. 2.

Basic Types: There are several methods of securing derived circuits by the use of carrier frequencies but only two are in common use: a. Single sideband, amplitude modulation. b.

Frequency modulation.

Single sideband amplitude modulated carriers are almost universally employed in trunk circuits. This is largely because they are efficient s of bandwidth and therefore permit a maximum number of channels in a given spectrum space. 3.

Low-Frequency and High-Frequency Carriers: Single-channel carriers usually occupy a frequency-range of from 4,000 to 10,000 Hz. Three-channel carriers generally extend upward to about 35,000 Hz. High-frequency carriers extend from 40,000 to about 150,000 Hz and normally provide 12 channels. There are other carrier systems having as many as 600 channels but they are designed for co-axial cables or microwave radio.

4.

Attenuation of Carrier Frequencies: When planning carrier installations consideration must be given to the greater attenuation of carrier compared to voice frequencies. Although this increase is not nearly proportional to frequency, it is an appreciable factor. On 0.104 dry, open copper wire, for example, the attenuation at 100,000 Hz is approximately four times the db loss at 1,000 Hz. This disadvantage is at least partly offset by the fact that carrier repeaters are generally much more effective than voice-frequency repeaters and provide much higher gains. The explanation of this is that carrier repeaters are, in effect, four-wire repeaters. Actually, transmission in both directions may take place over the same pair of wires, but the use of separate frequencies for the two directions, insolated form each other by appropriate filters, provides very nearly the equivalent of a four-wire circuit.


Part 21.1.1 5.

I.

Carrier Regulation: Carrier attenuation on cable pairs is subject to variation with temperature. Attenuation on open-wire pairs is subject not only to temperature effects but also to the greater effects of wet weather, snow, and ice. A 100-mile carrier circuit, for example, having a dry-weather attenuation of 20 db may have losses of as much as 100 db under severe icing conditions. Such a circuit would obviously become completely unworkable unless increased gain is provided to compensate for the losses. All long-haul carriers are provided with automatic gain control. This feature makes possible the operation of high-quality circuits with many repeater sections. Circuits 2,000 and more miles in length are not uncommon.

T-Carrier Systems 1. CARRIER: Describes a digital communications facility with a 1.544 Mbps bandwidth that can be used for digitized voice, data or image transmission. The 1.544 Mbps standard is used in both North America and Japan; the rest of the world implements E-1 at 2.048 Mbps. T-1 service is available from virtually every long distance carrier, as well as satellite carriers. Although it started strictly in the province of telephone companies, it is now available to end-s. Numerous multiplexer vendors offer equipment so that railroads can utilize it on their own transmission lines, including copper, coax and fiber-optic 2.

CHANNELS: T-1 "pipes" carry the equivalent of twenty-four 64 Kbps voice circuits, or other combination of voice, data or video within their 1.544 Mbps bandwidth. For pure data transmission, a T-1 line can handle more than 24 circuits, since data may be at other speeds, as 1.2, 2.4, 4.8, 9.6, 19.2, 56 Kbps, 64 Kbps, N x 64 Kbps.

3.

MODULATION TECHNIQUE: In its basic implementation for voice communications, a T-1 channel bank samples analog signals from each of up to 24 channels connected to it. Using Pulse Code Modulation (PCM) techniques an analog signal is sampled 8000 times per second, each sample being represented by an 8-bit code. This results in a digitized voice signal requiring 64 Kbps of bandwidth for each individual


2001

voice channel. The digital bit stream for each voice channel, also known as a DSO channel, is time-division multiplexed with other similar channels and transmitted over a four-wire circuit (the T-1 line) to another channel bank at the receiving end which decodes it back to its original 24 analog signals. In a fully digital environment with digital PBX's or other devices, conversion from analog to digital takes place at the telephone instrument only, with separation of channels taking place internally on the digital bus of the PBX, for example, for individual switching without a change from the digital encoding. 4.

TRANSMISSION: Data, in the form of digitized voice, is assembled into frames for transmission over a T-1 line. Each frame consists of 24 DSO channels containing 8 data bits representing a digitized voice sample for each of the 24 channels. This, plus one framing bit, used by carrier equipment to signal the beginning of each frame, makes a total of 193 bits per frame. The entire frame generation process occurs 8000 times per second. This results in an aggregate data rate of 1.544 Mbps, also known as a DS-1. Higher transmission speeds are possible and have a T-series digital circuit hierarchy as follows:

Digital Signal (DS)

Transmission Speed (bps)

0 1 1C 2 3 4

64K 1.544M 3.152M 6.312M 44.736M 274.176M

5.

& Voice Channels 1 24 48 96 672 4096

FORMATS: The frame configuration of 24 channels with 8 bits per framing bit is called the D4 Format. It allows the transmitter and receiver to achieve proper synchronization so that the beginning and end frame can be readily identified for information retrieval. A more complex framing technique, called D3 Format is used in many voice and data applications also. It utilizes a concept called a super-frame, which consists of 12 separate DSO frames, two of which include signaling bits. A even newer technique,


Part 21.1.1 called Extended Super-frame Format (ESF), adds a Facility Data Link (4 Kbps) and Cyclic Redundancy Check (2 Kbps) to a smaller framing sequence of 2 Kbps. The result is continued use of the one bit for every 8000 samples (8 Kbps) concept, but provides a data channel between ends without interrupting a session in progress and the CRC indication of transmission quality over the circuit. This information can be polled by Network Management to proactively monitor line performance. 6.

TIMING: Since T-1 is a synchronous type of transmission, it must have timing information encoded between sending and receiving devices, plus all signal repeaters in between. In T-1, timing information is sent as part of the digital pulse stream. The beginning pulse of each frame is called the S, or framing, pulse and is used to synchronize terminal devices. The least significant pulse, or 8th bit, is often used for timing and signaling. Thus small errors are created. Voice traffic is generally unaffected by these errors but data speeds are limited to 56 Kbps in this system, since data does require error-free transmission. However, ISDN standards, which is based on T-1 specifications, eliminates even this limitation by providing for separate signaling channels on each connection.

7.

High bit rate Digital Subscriber Link (HDSL) provides DS-1 transmission thru existing metallic plant with extended range unaffected by bridge taps.


- 1 – AREMA C&S Manual

2001

Part 21.1.2

Recommended Functional/Operating Guidelines for Analog Data Transmission Over Voice Channels Extended 2001 (12 Pages) A.

Scope The transmission of data over channels that have been designed primarily for voice operation presents some new problems. Certain transmission parameters that are of small concern in voice transmission must be carefully considered in order to assure satisfactory data transmission performance. The following paragraphs describe these parameters and the mitigation of some of the possible transmission impairments.

B.

General Considerations 1. In voice communication the talker and listener usually have a high degree of tolerance to transmission impairments. For one thing, redundancy in speech often allows the listener to supply syllables or even words missed or garbled because of noise, excess loss or other transmission difficulties. Also, people will adjust themselves (within limits) to problems in transmission by talking louder, listening more closely or asking for repeats. 2.

C.

Data transmission is more exacting than voice transmission for a number of reasons. First and foremost the data sets are really electronic devices that do not exhibit human characteristics. The sets cannot adjust themselves to transmission variations except within very narrow limits. Further, not only are they very sensitive to the same transmission impairments as voice but they are also sensitive to other transmission parameters which have little effect on voice.

Transmission Considerations 1. Primary transmission characteristics of voice channels that can affect data transmission are: Over-all Attenuation Attenuation-Frequency Characteristics Return Loss and Echo Steady Background (White) Noise Impulse Noise Delay-Frequency Characteristics Carrier Frequency Error

Part 21.1.2


2001

Of these, only the first four usually cause serious difficulties in voice transmission. The same four items are even more important in data transmission, because degradations not serious enough to prevent voice communications may make data transmission virtually impossible. The last three items are of minor importance in voice transmission but are very important to the transmission of data signals. 2.

3.

4.

Transmission Levels: The maximum transmit level of data sets is limited by both crosstalk considerations and the maximum level at which the data signals may be applied to a carrier channel. The data carrier level should be set at a level -13 dbm0 (below ref./test tone level) for measurement point. When more than one tone is involved in the data signal the above transmit levels represent the total rms power of all tones transmitted simultaneously. Over-all Loss: The maximum over-all loss allowable between data sets depends upon the sensitivity of the set and varies with the type of set and operating frequencies. Generally, the maximum permissible loss ranges from 30 to 45 db. Exact figures can be obtained by subtracting the maximum transmit level from the minimum receive level. In determining this value the highest frequency used by the data signal should be considered. Data transmission systems are susceptible to over-all loss changes due to level variations that may be encountered on a channel. The effect of level variations on data transmission is dependent upon a number of factors, including type of modulation and type of automatic gain control used in the data sets, magnitude of level changes, and the frequency with which level changes occur. Effects of level changes on data sets are usually most serious when the changes result in higher loss and the data sets are operating near their minimum receive levels. Typical of level variations that may be encountered are: a.

Changes due to temperature, daily as well as seasonal, component aging, etc.


2001

Part 21.1.2

b.

Abrupt changes due to microwave switching, microwave fading where protection channels are not available, regulation action, equipment irregularities, etc.

c.

Slow level changes up and down at a cyclic rate of several seconds or more.

Level variations can be kept to a minimum by the application of proper engineering and maintenance practices. 5.

Loss-Frequency Characteristics: The loss-frequency characteristic (sometimes referred to as the transmission-frequency characteristic) is very important to good data transmission. A loss-frequency curve can be used to determine both attenuation distortion (sometimes called frequency distortion) and bandwidth. Attenuation distortion is usually expressed as so many db slope across the transmitted band. For optimum data transmission this slope should be essentially 0 db, in other words, the loss-frequency curve should be essentially flat in the transmitted band. In the practical case data sets are designed to tolerate some attenuation distortion. With those data sets using speeds under 200 bits per second slope is not a serious problem because of the limited bandwidth. Some of the higher speed data sets (1200-2400 bits per second range) have compromise loss-frequency equalizers that increase their tolerance to slope. Slope tolerances for the various types of data sets range from about 3 to 10 db in a band of 1,000 to 2,300 Hz. Most cases of excessive slope on channels can be taken care of by the application of attenuation-frequency equalizers.

6.

The loss-frequency characteristic of a channel can be used to define its bandwidth. Some data sets involve frequencies as low as 600 Hz and as high as 2,700 Hz. Modern transmission facilities provide sufficient bandwidth for such as some of the older type carrier systems and heavy loaded cable systems such as the H172-63 system may prohibit the use of such data sets.

Part 21.1.2


2001

7.

Return Loss and Echo: In voice transmission, talker echo is controlling. With properly designed data sets talker echo is not particularly important because the set cannot send and receive on the same frequency at the same time. It is necessary to delay the start of data reception until talker echoes have diminished but this is accomplished in the design of the data set. Listener echo, on the other had, is very important in data transmission because the receiving data set will interpret data received through the echo path as interference. This happens because listener echoes usually affect subsequent transmitted pulses at bit speeds used on voice channels. Most data sets are designed to tolerate listener echo as little as 12 db below received signal levels.

8.

Steady Background (White) Noise: Steady background noise, including white noise is not a serious problem with data transmission over a voice channel if satisfactory noise objectives from a voice standpoint are met on the channel. Under such conditions adequate signal-to-noise ratio should be obtained for satisfactory data transmission over the channel. In general the signal-to-steady noise ratio should be at least 15 db.

9.

Impulse Noise: Impulse noise hits are a primary source of errors in data transmission. Such hits are short in duration, often lasting only a milli-second or less. Since the human ear is insensitive to such short noise peaks, impulse noise of this type is not important in voice transmission. With data transmission, however, impulse noise is a serious problem because the bit durations are short, for example 0.8 millisecond in a 1200-bit frequency shift serial system. If impulse noise hits are of sufficient magnitude and occur very often, they can seriously degrade the error rate of a data transmission system.

10.

One of the simplest criteria for the identification of impulse noise is there is more than 15 counts of impulse noise maximum in any 15-minute interval above a threshold that is 6 db below the received signal level. White noise in itself will have excursions


2001

Part 21.1.2

that seldom exceed this level. A more detailed description of impulse noise would involve the following parameters: a. The distribution of peak amplitudes;

11.

b.

The frequency spectra of individual bursts;

c.

The distribution of burst lengths;

d.

The distribution of impulses in time or possibly the distribution of the intervals between bursts.

Each one of the above parameters is of importance in determining the detrimental effects of impulse noise on a data signal. Consider that: a. The interfering effect of an impulse is a function of its amplitude; b.

Data systems are often of small bandwidth. Hence, the position of the major portion of the energy of an impulse in the frequency domain must be considered;

c.

The length of an interfering noise impulse will determine how many data bits may be disturbed;

d.

The length of quiet intervals is an important factor in determining one distribution of errors in the received signal. This information is necessary in the construction of error detection and error correction codes.

12.

Occurrence rate of impulses is related to the system activity. However, during equal system activity times impulse noise is a function of traffic load. For system evaluation purposes, measurements should be made during periods of peak system activity.

13.

Impulse noise measurements require relatively long periods of time. The reason for this hinges on two factors: a. Impulse noise has a low incidence rate. b. Determination of a distribution requires a large number of samples.

Part 21.1.2


2001

14.

The long measuring period and repetitive nature of the measurements lends itself to automated equipment. Measuring sets are available with built-in timers, filters and adjustable threshold settings for measurement of impulse noise.

15.

With such an instrument, impulse noise objectives could be stated in of a threshold level and a maximum permissible number of registrations on the counting in a given period of time.

16.

Channels provided by carrier systems inherently are subject to impulse noise. For these types of channels the noise comes primarily from carrier-frequency transients generated as by-products of normal telephone operation. Among the known sources of impulse noise generated in communication plant are: a. Relays and switches in switching offices. Dial switching offices are usually more prolific of noise than manual switching offices because of the large number of switching operations.

17.

b.

DC telegraph, particularly when operated on grounded simplex facilities.

c.

Breakdown test sets, buzzer-type sets and reflection type fault finders.

d.

Rectifier-type power supply and defective power lines.

e.

20-Hz ringing.

Impulse noise may also arise from sources external to the communication plant such as atmospheric static, radio transmitters or another carrier system.


2001

Figure 2112-1:

Part 21.1.2

Secondary Induction Paths

18.

Figure 2112-1 illustrates how noise generated by relays and switches in the office may travel into the plant over the longitudinal (ground return) circuit, energizing the longitudinal circuit of the carrier pairs by near-end coupling. Due to the less-thanperfect longitudinal-to-metallic balance of the carrier pair and the associated equipment some of the noise power appears in the metallic circuit of the carrier system.

19.

Figure 2112-2 shows how noise generated by central office equipment that is not located in the same building as the carrier equipment can nevertheless appear on the carrier system. It will be noted that noise can reach the carrier pairs by way of both nearend and far-end coupling.

Part 21.1.2 Figure 2112-2:


2001

Noise Induction From Non-Carrier Office

20.

The most important path for induction from sources external to the communication path is by secondary induction from non-carrier pairs. These include voicefrequency channels in the carrier cable having extensions directly into open wire lines or to branch cables of short length connected to open wire or drop wire plant. A longitudinal voltage is picked up on the open wire or drop wire from an external source such as atmospheric static. This voltage is propagated longitudinally into the cable pairs connected to the open wire and then into the carrier system by the same process of longitudinal coupling and unbalance as discussed above.

21.

When a carrier system is operated in part or entirely over cable pairs with non-soldered twisted ts, erratic noise of various kinds may be apparent as a


2001

Part 21.1.2

result of the variation in resistance of such ts with movement of the conductors due to changes in temperature or wind action. The use of punched sleeves or soldering on carrier pairs should maintain uniformly low resistance over a long period of time. 22.

Secondary induction of office noise may be controlled as follows: a. Plan the carrier system layout so the repeaters or terminals are physically separated from the source of the noise. In this way, the noise is attenuated before reaching the carrier system. To a large extent this attenuation is due to the loss in the longitudinal circuit of the disturbing conductors. Although it is not possible to estimate longitudinal loss precisely, it may be approximated by using metallic circuit attenuation data. b.

Use a separate carrier-only entrance cable. Here the noise is attenuated both as it travels over the non-carrier pairs from the office to the junction with the carrier cable and from this point back to the office over the carrier pairs. The noise reduction is, therefore, roughly twice the one-way loss in the cable pairs.

c.

Install longitudinal suppression inductors on the non-carrier pairs. These coils are of two general types, one for use on pairs not employing phantom circuits and the other on pairs that make up phantom circuits. These types of inductors are only used to suppress noise generated in switching offices.

d.

Install radio suppression filters in the noncarrier cable pairs at the main distributing frame of the distributing switching office. These filters should be placed on all non-carrier pairs that enter the carrier cable, with the output wiring segregated from the input wiring.

e.

Restrict the length of the carrier repeater section adjacent to the carrier equipment.

Part 21.1.2


2001

23.

Type 1530A (2-windings) and 1530B (4-windings) or equivalent inductors are used to suppress longitudinal noise that enters a carrier cable at open wire or drop wire taps. The 1530A inductor is used on non-phantomed pairs and the 1530B is used on pairs that make up phantom circuits. This type of longitudinal noise arises from external sources such as atmospheric static or a radio transmitter.

24.

Grounded dc telegraph operated in the same cable with carrier systems may be an important source of impulse noise. High values of noise may be expected from repeaters whose transmitting relay s operate directly into the line. Any high impedance between the relay s and the line such as a relay winding, retard coil of a voice-frequency noise killer, or resistance pads, and any low impedance shunts to ground, such as the capacitor in some of the noise killer circuits provides important reductions in the amount of carrier-frequency noise put out on the line.

25.

The magnitude and frequency of occurrence of impulse noise voltages are used to specify objectives for impulse noise on a channel to be employed for data transmission. The objective is expressed as the noise peak level that will be equaled or exceeded a given number of times during a specified period of time on a long-term average basis. This period of time usually is 30 minutes during the busy hour period and the given number of times is 90.

26.

Data sets that operate at speeds in the 1000-9600 bits per second range require a large part of the voice band. In general, these data sets have an effective bandwidth approaching that of C message weighting. The basic impulse noise objectives are expressed in dbrn using a weighting similar to the C message weighting. They vary somewhat depending upon the type of modulation, gain control and bandwidth employed. However, for data sets operating in the range of 10009600 bits, the objectives are set to provide in the order of a 4 to 8 db ratio between the rms power of the data signal as measured by a transmission


2001

Part 21.1.2

measuring set and the setting of the Impulse Noise Counter. Thus for a data signal level of -16 dbm not more than 15 counts should be obtained with an Impulse Noise Counter setting of 68 dbrn to provide a 6 db ratio, i.e., -16 dbm corresponds to 74 dbrn; 74-68 = 6. 27.

Delay-Frequency Characteristics: Data transmission can be seriously degraded by delay distortion better known as envelope delay distortion. Such distortion results from the variation of the phase characteristic of a channel from perfect linearity. For voice transmission envelope delay distortion is not a problem because the ear is relatively insensitive to minor phase variations.

28.

Envelope delay distortion is usually expressed as the maximum excursion of the envelope delay characteristic within a particular frequency band. It is generally expressed as microseconds over the band. Data sets vary in their tolerance to envelope delay distortion, depending upon the type of modulation and bit speed. The slow speed sets can operate satisfactorily with more envelope delay distortion than is possible with the higher speed sets. The effects of excessive envelope delay distortion show up as high distortion of the data signals and high error rate.

29.

Figure 2112-3 shows typical envelope delay or delay distortion characteristics of various types of carrier channels and a loaded cable circuit. It will be noted that the distortion is very much greater at the extreme ends of the band. The delay distortion can be minimized by the application of special networks that effectively flatten out the characteristics shown in the drawing. Such networks are sometimes included as a part of the data sets.

30.

Carrier Frequency Error: Carrier frequency error experienced over a channel has little effect on voice transmission. In the case of data transmission it presents more serious problems. Modulation in data set transmitters results in tones of various frequencies on the channel. These tones are demodulated at the data set receivers to recover the data. If the frequencies of the transmitted tones are

Part 21.1.2


2001

changed as they traverse the channel, the frequency sensitive circuits in the receivers will not be receiving the tones at the optimum points resulting in distortion in the received data. In general, the maximum line frequency error on a channel between data transmitter and data receiver should not exceed ± 10 Hertz. Figure 2112-3:

31.

Envelope Delay of Various Facilities

There is no frequency error problem with wire facilities or carrier systems in which the carrier used for modulation is transmitted to the receiving end and used for demodulation. Likewise, there is no problem in systems that suppress the carrier at the transmitting end and re-supply it at the receiving end from a generator held in synchronism with the generator at the transmitting end. Frequency error problems may exist in suppressed carrier systems where there is no provision for synchronizing carrier supplies.


Section 22 – Radio 2002



Index

SECTION 22 - RADIO Part

C

Type & Subject

22.1.1

35-2

Recommended Clean Cab Radio Channel Designators and Railroad Radio Services VHF Frequency Table

1

Reaffirmed 2002

Listing of Allocated Frequencies in the Railroad Radio Service

1

Extended 2001

Recommended Design Criteria/ Functional Guidelines for Interface of Radio Communications Module in “Clean Cab” Locomotive

16

Extended 2001

Recommended Functional/ Operating Guidelines for Remote Control of Engine by Portable Radio

3

Extended 2001

Recommended Design Criteria for Rack Mounted Frequency Modulated Transceiver and Accessories

14

Extended 2001

Recommended Guidelines, Considerations and Radio Frequency Requirements for Train Information Systems

39

Extended 2002

22.1.2

22.2.1

22.2.2

22.2.3

22.3.1

35-2

35-2

35-2

35-2

35-2

Pages

Status

______________________________________________________________ -1Note: C =



2002

AREMA® C&S Manual

Part 22.1.1 Recommended Clean Cab Radio Channel Designators and Railroad Radio Service VHF Frequency Table Reaffirmed 2002 (1 Page)

"All Channel Radios" display the selected channel by two sets of digits i.e., 54 54 indicates the radio is transmitting and receiving on the same frequency 160.920 MHz (Simplex); 08 64 indicates the radio is transmitting on 160.230 MHz and receiving on 161.070 MHz (Duplex). Table 2211-1: Frequency Table Channels No. MHz 2* 159.810 3* 159.930 4* 160.050 5* 160.185 6* 160.200 7 160.215 8 160.230 9 160.245 10 160.260 11 160.275 12 160.290 13 160.305 14 160.320 15 160.335 16 160.350 17 160.365 18 160.380 19 160.395 20 160.410 21 160.425 22 160.440 23 160.455 24 160.470 25 160.485 26 160.500 27 160.515 28 160.530 29 160.545 30 160.560 31 160.575

No.

#Footnote 613 Channels MHz No. MHz 32# 160.590 33# 160.605 34# 160.620 35# 160.635 36# 160.650 37# 160.665 38# 160.680 39# 160.695 40# 160.710 41# 160.725 42# 160.740 43# 160.755 44# 160.770 45# 160.785 46# 160.800 47# 160.815 48# 160.830 49# 160.845 50# 160.860 51# 160.875 52# 160.890 53# 160.905 54# 160.920 55# 160.935 56# 160.950 57# 160.965 58# 160.980

Channels No. MHz 59 160.995 60 161.010 61 161.025 62 161.040 63 161.055 64 161.070 65 161.085 66 161.100 67 161.115 68 161.130 69 161.145 70 161.160 71 161.175 72 161.190 73 161.205 74 161.220 75 161.235 76 161.250 77 161.265 78 161.280 79 161.295 80 161.310 81 161.325 82 161.340 83 161.355 84 161.370 85 161.385 86 161.400 87 161.415 88 161.430 89 161.445 90 161.460

#Footnote 613 Channels 91# 92# 93# 94# 95# 96# 97#

*

Canada Only

#

International Maritime Frequencies in the bands 160.600 - 160.975 MHz and 161.475 - 162.050 MHz for railroad use in the United States and Canada only.

161.475 161.490 161.505 161.520 161.535 161.550 161.565

_____________________________________________________________________________ -1–



Part 22.1.2

Listing of Allocated Frequencies in the Railroad Radio Service Extended 2001 (1 Page) The below listed frequencies are allocated to the Railroad Radio Service and are coordinated by the Association of American Railroads by the authority of the Federal Communications Commission Rules and Regulations Part 90 Private Land Mobile Radio Service. Very High Frequency - VHF Voice analog channels used in all train operations and other railroad related functions 91 Channels* 160.215 MHz - 161.565 MHz Channel Spacing - 15 kHz Occupied/Equipment Bandwidth - 25 kHz Ultra High Frequency - UHF Voice Analog - Paired Channels 452.900 MHz (Fixed) - 457.900 MHz (Mobile) Channel Spacing - 12.5 kHz Occupied/Equipment Bandwidth - 25 kHz Slave Control of Locomotives - Paired Channels 452.925 MHz - 452.950 MHz 457.925 MHz - 457.950 MHz Channel Spacing - 12.5 kHz Occupied/Equipment Bandwidth - 20 kHz End of Train Device - EOTD Half Duplex 452.9375 MHz - 457.9375 MHz Channel Spacing - 12.5 kHz Occupied/Equipment Bandwidth - 16 kHz Advanced Train Control Systems (ATCS) - Paired Channels Base Mobile 896.8875 MHz - 935.8875 MHz 896.9375 MHz - 935.9375 MHz 896.9875 MHz - 935.9875 MHz 897.8875 MHz - 936.8875 MHz 897.9375 MHz - 936.9375 MHz 897.9875 MHz - 936.9875 MHz Channel Spacing - 12.5 kHz Occupied/Equipment Bandwidth - 12.5 kHz *

See Manual Part 22.1.1 (Recommended Clean Cab Radio Channel Designators and Railroad Radio Service VHF Frequency Table) for channel and frequency arrangements.



Part 22.2.1 Recommended Design Criteria/Functional Guidelines for Interface of Radio Communications Module in "Clean Cab" Locomotive Extended 2001 (16 Pages)

A.

Purpose Recommended design criteria/functional guidelines are for the purpose of setting forth the recommended general requirements for the space, mounting and connections for a communications module in a locomotive utilizing AAR clean cab concepts. They set forth specific detailed requirements representing modern communication practice recommended for new installations and for replacement of existing installations when general renewal or replacement is to be made.

B.

Mounting and General Arrangement of Radio or Control Head Module The mounting and general arrangement of a radio module are shown in Figure 1. It should be ed that the radio module is always installed and serviced from the rear of the control stand. Therefore, sufficient clear space at the rear shall be allowed for removal and servicing of the communications equipment. The mounting tray always remains mounted within the control stand when the radio is removed for service. A control head only module may be mounted over the front opening with 10-32 nuts and bolts, utilizing the mounting holes shown in Figure 2.

C.

Fabrication 1. The space and mounting arrangement shall be in accordance with Figures 1, 2, 3 and 4. It should be noted that the area adjacent to the connectors 1, 2, and 3 above the padlock shown in Figure 1 shall be kept free and clear of any non-radio cables or piping to insure clearance for radio connector plugs, etc. 2.

Cables shall be installed in a manner to allow sufficient length for connection to mating receptacles regardless of location on the communications module.

3.

When a control head module is used, a flat plate may be required in lieu of the radio mounting plate to provide protection to the control head module.


2001

D.

Thermal Environment The ambient temperature inside the module partition of the control stand shall be within -30°C(-22°F) to 65°C(140°F).

E.

Mounting Plate 1. The communications module shall be mounted by a plate as shown in Figures 4 and 5. 2.

This radio mounting plate shall be secured to the control stand mounting brackets. Refer to Figures 2, 3 and 5.

3.

The control stand mounting brackets should be at right angle to the vertical surface of the control stand.

4.

A suitable model of the AAR Clean Cab Radio module has been supplied to all domestic locomotive manufacturers for the purpose of verification of correct fit.

5.

F.

Handset Hanger and Cable Opening Location 1. When a handset is required, the handset hanger may be located as shown in Figure 6. 2.

G.

The radio module shall be secured in place within the control stand by a suitable locking device (not a responsibility of the locomotive manufacturer).

A handset cable opening shall be provided as shown in Figure 3.

Electrical Connectors 1. External Remote Connector: Plug - Amphenol 67-06C1412P or approved equivalent. (Mates with 67-02E14-12S.) 2.

Antenna Connector (VHF): Plug - Amphenol 83-1SP or approved equivalent. (Mates with 83-1R)

3.

Power Connector: Plug - Amphenol-Straight MS 3106A-184S or Right Angle MS-3108A-18-4S, Strain Relief MS 3057-10-6 or approved equivalents. (Mates with MS3102A-18-4P)

4.

Handset Connector: Plug - Amphenol MS-3106A-14S-6P, Strain Relief MS 3057-6A or approved equivalents, (Mates with MS-3102A-14S-6S-639)

- 3 – AREMA C&S Manual 2001 H.

Part 22.2.1 Electrical Connections: 1. Power Connector Pin Assignment on the Communications Module. Amphenol MS 3102A-18-4P or approved equivalent. A- +72 volts B- -13.6 volts C- -72 volts D- +13.6 volts 2.

External Remote Connector Pin Assignment: A- Microphone B- Microphone/Earphone Ground/Shield C- Push-to-talk D- Push-to-talk return E- Handset audio F- A plus (power) H- Handset audio return or spare J- A minus (power) K- Channel Revert L- Spare M- Speaker)Pair N- Speaker)

I.

Blanking Plate When a communications module is not used, the front opening shall be covered by a surface-mounted blanking plate, secured to the control stand opening by 10-32 nuts and bolts, utilizing the mounting holes shown in Figure 2.

J.

Tolerances 1. Dimensions are supplied in fractions or decimals appropriate to fabrication operations. 2.

K.

The tolerances for all dimensions are to be plus or minus 1/16 in. unless otherwise specified.

Data Option 1. The structure of the radio should be modular and have the ability to transmit and receive data. Data modulation/De-modulation, message encoding, decoding, Forward Error Correction (FEC) and RF protocols should conform to the latest edition of AAR ATCS Specifications 200 and 210.

- 4 – AREMA C&S Manual Part 22.2.1 2.

2001

Maximum of three RS422 serial data connectors type MS 3112 F 14-15 P (mates with a MS 3116 F 14-15 S Plug) should be mounted at the back of radio.

Figure 1: Pictorial View of Typical Communications Module Installation


Part 22.2.1 Figure 2: Rear View of Clean Cab Communications Module Mounting Details

- 6 – AREMA C&S Manual Part 22.2.1 Figure 3: Additional Mounting Details, Section A-A

2001


Part 22.2.1 Figure 4: Details of Mounting Plate

- 8 – AREMA C&S Manual Part 22.2.1 Figure 5: Additional Details of Mounting Plate

2001


Part 22.2.1 Figure 6:

Additional Details of Mounting Plate


2001 Additional Details of Mounting Plate



Isometric View of Mounting Plate Control Stand


2001 Figure 9:

Plan View of Control Stand


Part 22.2.1 Angle Iron and Tray Mounting in Control Stand


2001 Angle Iron and Tray Mounting in Control Stand


Part 22.2.1 Angle Iron and Tray Mounting in Control Stand


2001 Angle Iron and Tray Mounting in Control Stand


Part 22.2.2 Recommended Functional/Operating Guidelines for Remote Control of Engine by Portable Radio Extended 2001 (3 Pages)

A.

B.

Purpose This Manual Part recommends functional/operating guidelines for remote control by personnel of an engine in yard switching service, in hump service, in road switching service or in road and terminal service. General 1. System shall provide for the remote control of the following, where required: (a) Direction (b) Throttle (c) Engine Brakes (independent) (d) Train Brakes (automatic) (e) Horn (f) Bell (g) Coupler pins of engine (h) Rail sander (i) Headlight bright or dim (j) Speed selection (k) Dynamic brake (l) Others (to be specified) 2. The system shall be designed so that the engine can be operated in either the remote control or manual mode such that only one mode of operation is functional at a time. Manual movement of the controls when the system is in the remote mode or remote operation of the system with the control in the manual mode will not create an undesired release of brakes or an undesired call for power. 3. System shall provide the following automatic features, where required: (a) Speed regulation (operating, coupling or other) (b) Headlight selection for direction (c) Fire protection (d) Emergency stopping program in case of: (l) Low air pressure (2) Low oil pressure (3) High engine temperature (4) Fire


2001

4. The combined controller and transmitter shall be of such size, weight and design as to permit it being carried or worn without interference to vision, hearing, mobility or such activities as throwing track switches by hand, using a telephone, coupling or uncoupling cars, climbing upon engine or cars, or entering an engine cab. 5. The combined controller and transmitter shall be powered by a lightweight battery that is to be normally charged from the engine power supply when the unit is in its storage rack located on the engine. The battery shall be capable of operating the equipment continuously for 3-1/2 hr. 6. The controller shall include a dean feature to stop the engine and attached cars should the operator fall or become disabled. 7. Transmission power shall be adequate to provide reliable control from all points in line-of-sight within 2,000 ft. of the engine. 8. Each radio channel shall be on a frequency in the VHF or UHF band which is allocated by governmental agency for use by railroads and which is approved by that agency for use in the remote control of engines. The equipment shall be designed to use minimum spectrum space consistent with performance required by these performance specifications. 9. Remote control equipment for location on the engine shall be so designed that it can be installed so as not to interfere with conventional control equipment if provided. 10.System shall be designed so that failure will not cause an unsafe condition. When the normal control signal is not present at the engine receiver, the controls shall operate to apply the brakes and cut off the power. 11.System shall be designed to minimize interference from other remote control and communication systems, if any, in the same general area, and shall be designed so that such interference will not cause an unsafe condition. 12.Throttle control shall be designed to advance or retard throttle in discrete steps or "notches" on engines using this type of control.


Part 22.2.2

13.The radio equipment shall be capable of compliance with all applicable governmental rules, regulations and standards in effect at time of delivery. 14.Where required, an alarm device or devices, visible or audible from a distance of 2,000 ft. under normal conditions, shall be located on the engine to provide warning of low air pressure, wheel slippage, penalty brake application, operation of ground indication relay, or other abnormal conditions. 15.Systems designed with speed control shall be capable of limiting the speed of the engine to a maximum of 20 mph when it is in the remote control mode. 16.System shall be designed to insure that engine has stopped before power can be applied for movement in the opposite direction. 17.System shall be designed to insure there is adequate brake pipe or main reservoir pressure to stop the train or engine before power can be applied for movement.



Part 22.2.3 Recommended Design Criteria for Rack Mounted Frequency Modulated Transceiver and Accessories Extended 2001 (14 Pages)

A.

Purpose The purpose of this Manual Part is to guide the manufacturer in the supplying of frequency-modulated Rack Mounted Transceiver equipment for use on railroad mobile equipment.

B.

Specifications Except where otherwise noted in this part, the transceiver shall conform to TIA Standards 603, “Land Mobile FM or PM Communication Equipment Measurement and Performance Standards”, and Canadian Government Standards, Industry Canada RSS-119, 2500 Wilson Blvd., Arlington, VA 22201 Note: used.

Latest version of above specifications shall be

C.

Dimensions Metric equivalents of all dimensions in millimeters are shown in parenthesis. All dimensions shall be within the tolerances specified. Where allowable variations are not shown, reasonable correspondence to specified dimensions is required, consistent with good commercial practice.

D.

General Requirements 1. Service Conditions: Unless otherwise specified, equipment shall be operable without damage under any combination of service conditions listed below: a. Ambient Temperature*...-30oC(-22oF) to +65oC(+149oF) b. Ambient Relative Humidity...0 to 95% c. Duty...................Transmitter intermittent, **Receiver continuous. d. Power Supply.............Any one of the power supplies specified in Paragraph G-1. 2.

Normal Test Conditions: Unless otherwise specified, the term "normal test conditions" as used in this ______________________ *Inside weatherproof housing. **Cycle of 5 min. on and 15 min. off for a period of 7 hr., and 10 sec. on and 20 sec. off for 1 hr.


2001

specification shall be understood to have the definition given below: a. Ambient Room Temperature. +25oC(+77oF) b. Line Voltage.............Any one of the normal voltages as shown in Paragraph G-1. c. Power Output.............Full rated. d. Mode of Operation........Transmitter intermittent, **Receiver continuous. 3.

Frequency Range: This equipment should be capable of operation on any specified frequencies between 159 and 162 Mhz.

4.

Primary Power: The primary power input required by this equipment shall be a minimum consistent with other requirements of this specification. Reference G1

5.

Single-Package Unit: Unless otherwise ordered, the transmitter, receiver, and power supply should be furnished in a single-case assembly, including shock and vibration mounts, when required, which shall conform to the following: a.

Mounting Rack and Base Plate: The mounting rack and base plate shall be as shown in Figures 1 and 2, and should be neat in appearance with all corners and edges well formed and slightly rounded. The dimensions of the mounting rack shall be: Inside width--10 in.(254), +1/16 in.(1.6), -0 in. Length --15 in.(381), +0 in., -1/8 in.(3.1) measured from the back of the front hook to the inside curve of the rear hook. The dimensions of the base plate, Figure 3, shall be: Width--10 in. (254) to inside of turn-up. Length--17 1/2 in. (444.5) To provide rigidity, the base plate should have a minimum of 1/4 in. (6.3) turn-up along its full length on each side. Four 1/2-in. (12.7) holes shall be provided at the locations shown in


Part 22.2.3 Figure 3. Conduit brackets for 1-in. (25.4) conduit should be provided on each side of the base plate near the rear end of the terminal strips. The mounting rack should be ed 21/4 in. (57.1) above the base plate in such a manner as to provide accessibility to the terminal strips and adequate space for forming heavy wires. b.

Mounting Rack and Base Plate (Optional): The mounting rack and base plate shall be as shown in Figure 2. For this option, a completely enclosed mounting base should be provided to protect the wiring and the terminal strips when no radio unit is installed. A removable cover should be provided to gain access to the terminal strips. The dimensions of the optional mounting rack and base plate shall conform with those shown above in this section.

c.

Terminal Strips: One two-point terminal strip, Jones 2-150, or approved equivalent, and two 12point terminal strips, Jones 12-142, or approved equivalent, should be mounted and numbered as shown in Figure 1. The numbering strip should insulate the terminals from the base. Terminals shall be utilized as shown in Figure 4.

d.

Sockets and Plugs: The communications unit shall have a Type NK-L23-32S socket, or approved mechanical and electrical equivalent, located as shown in Figure 6. The insert in the socket shall be oriented within the socket as shown. The plug shall be a Type NK-L23-23C, or approved mechanical and electrical equivalent. The insert within the plug shall be oriented as shown in Figure 6. The cable attached to the plug should be long enough to reach the socket as located anywhere in the area specified in Paragraph (e), but not less than 15 in. (381) from clamp on base to clamp on plug. The antenna coaxial receptacles shall be Type 83-1R, or approved mechanical and electrical equivalent, and located as to be separated from the plug and cable by at least 2 in. (50.8).

- 4 – AREMA C&S Manual Part 22.2.3 e.

2001 Dimension of Case Assembly: The outer dimensions of the case assembly shall not exceed: Width -- 15 in.(381) Length-- 18 in.(457.2)(not including handle) Height-- 9-1/2 in.(241.3) Figure 1:

Mounting Rack and Base Plate



Mounting Rack and Base Plate (Optional)


2001 The handle should be 3/8-in. (9.6) or larger diameter stock and shall be located in the approximate center of gravity on the front of the equipment case, Figure 7, and should not extend beyond the outside edge of the case and approximately 2-3/4 in. (69.9) outward from the front of the case. The cable and antenna receptacles should be located within the area 5 in. (127) each side of the vertical center line and not closer than 11/2 in. (38.1) to the handle. The antenna receptacle should not be mounted below the cable receptacle. The case assembly should include facilities to permit securely attaching case to mounting rack, Figure 2.

f.

Weight: The weight of case assembly including transmitter, receiver, power supply and shock mounting, if required, should not exceed 48 lb. (21.8 Kg).

Figure 3:

Base Plate Mounting Holes


Part 22.2.3 g.

Locking Means: 1. Case: Provision should be made on the case for locks to prevent unauthorized entry into the case. 2.

E.

Case to Rack: The case should have provision to lock the case to the rack, mating with bracket on front of rack, Figure 1.

h.

Mounting Space: The equipment should be mounted in a location which is well ventilated and a minimum clear space of 20 in. (508) wide, 24 in. (610) deep, and 14 in. (356) high should be provided with the base plate mounted in the center of the 20 in. (508) dimension and the front of the base plate should be 2 in. (51) from the front of the opening.

i.

Mounting: When so ordered, this equipment should be provided with mountings capable of reducing the effects of vibration and shock encountered sufficient to prevent damage to the equipment. When both shock mounting and housing are provided, the mountings should be located inside the housing.

Transmitter Unit 1. General Requirements for Transmitter a. Input Circuit: The audio input impedance of the transmitter should be a nominal 500 ohms. Voltage of a positive polarity should be supplied to the ungrounded microphone terminal, such as to supply 10-milliamp. current through a 68-ohm, 5% resistive load. b.

Output Impedance: The output coupling system should be suitable for feeding a 50-ohm unbalanced coaxial line.

c.

Power Output: The transmitter should be designed to supply full radio frequency output of 25 watts or more as ordered into a 50-ohm unbalanced load.


2001 Terminal Strip and Plug Connection



Multi-channel Control Unit


2001 Figure 6:

Orientation of Plug and Socket

Figure 7:

Equipment Case

- 11 – AREMA C&S Manual 2001 F.

G.

Part 22.2.3 Receiver Unit 1. General Requirements for Receiver: a. Input Impedance: The receiver input circuit should be designed for operation from a 50-ohm coaxial unbalanced transmission line. b.

Output Impedance: The receiver should be designed to feed an 8-ohm load with one side of load grounded.

c.

Audio Output: Audio output should be at least 8 watts with a maximum overall distortion of less than 5% measured with 10 microvolt input modulated to a peak deviation of  3.5 KHz. At least this power should be obtained with a 1 microvolt input modulated 90% at 1,000 Hz. Distortion should not exceed that for 10 microvolts input at any frequency from 300 to 3 KHz.

d.

Auxiliary Squelch Control: An auxiliary squelch control circuit may be provided by the radio receiver unit. This circuit should terminate at Terminal 17 of the standard rack as shown in Figure 4. The control voltage with reference to the negative battery terminal (gnd.) should change by at least 3 volts, when operating into a load of 50,000 ohms or more, under conditions of squelch closed (without signal) changing to squelch open (with signal). The polarity of the voltage change should be more positive with "Squelch Open" than with "Squelch Closed". The control voltage available with squelch closed may be either zero or + 6 volts. The external squelch unit should be so designed that it will operate satisfactorily from either of these reference voltages.

Power Supply 1. Primary Power: Railroad equipment should be capable of operating from any one of the following power supplies, as specified by the purchaser.


2001 Normal Voltage 117 volts 60  10 Hz 36 volts dc 72 volts dc 13.6 volts dc

H.

Minimum 105 29 58 10.9

Maximum 129 42 85 15.5

a.

There shall be no continuity between any of the voltage input terminals and the chassis of the radio unit.

b.

Over a voltage range equal to the normal test voltage  10%, the power output should not drop more than 2.5 dB below the power output at the normal test voltage. All other transmitter requirements should be met, except for transmitter frequency stability that should be maintained over a range of  20% of normal test voltage. Over a voltage range equal to the normal test voltage -20%, the equipment should start and the transmitter power output should not drop more than 4 dB, and the usable receiver sensitivity should not degrade more than 3 dB. Receiver squelch when set according to manufacturer's specifications at normal test voltage should not open without signal, and squelch sensitivity should not degrade by more than 3 dB at normal test voltage +14%, -20%.

c.

The above tests should be performed in an ambient temperature of +25oC(+77oF).

d.

Adequate protection should be provided to prevent damage to the equipment caused by overload conditions and transient voltages.

Accessories 1. Antennas: Antennas furnished for use with this equipment should be of such design as to reduce high angle radiation to a minimum. Antennas should be designed for a nominal input impedance of 50 ohms unbalanced. When fed by a corresponding coaxial transmission line, the voltage standing wave ratio should be not greater than 1.5 to 1.


Part 22.2.3 2.

Handsets: Unless otherwise specified, microphones furnished for use with this equipment should be of the handset type incorporating a spring-return, push-totalk switch. Frequency response should be substantially flat between 300 and 3,000 Hz. The microphone should be capable of satisfactory operation between ambient temperatures of -30oC(-22oF) to +65oC(+149oF). Earphone impedance shall be between 75 and 150 ohms at 1,000 Hz.

3.

Mobile Control Unit: The following features should be provided: a. Transmitter-on indicator as required by governmental regulations. b.

Channel selector with minimum indication of four channels.

c.

Moisture-proof speaker

d.

Speaker pad with attenuation continuously variable over a range of approximately 20 dB. A residual audio level should remain to prevent the operator from turning the speaker "off".

e.

Handset connector with connections as follows: A--Microphone B--Microphone/earphone ground, shield C--Push-to-talk relay D--Push-to-talk return E--Receiver F--Microphone (balanced only)

f.

Attenuator network for feeding suitable level to handset earphones.

g.

Terminal board with terminal connections as follows: 1) OSC return 2) 8-ohm speaker 3) Chassis ground 4) Microphone ground 5) Microphone 6) Blank 7) Audio input (8 ohms) 8) Headset earpiece


2001 9) 10) 11) 12) 13) 14) 15) 16) 17) 18) 19)

h.

H.

Push-to-talk relay 13.6 volt dc relay (power) Channels 1, 5, 9 Channels 2, 6, 10 Channels 3, 7, 11 Channels 4, 8, 12 13.6 volt pilot light 6.3 volt pilot light Power in (if used) Power out (if used) Tone squelch disable

The control unit should provide low side keying and appropriate channel selection wiring per Figure 5.

Time Out Device: When so specified, a time out device should be provided which will limit continuous transmission and give an indication of such operation. Time limit is to be specified by purchaser.

AREMA® C&S Manual

2002

Part 22.3.1

Recommended Guidelines, Considerations and Radio Frequency Requirements for Train Information Systems Extended 2002 (39 Pages) A.

Purpose 1.

This document presents performance guidelines for Train Information Systems, intended to provide additional train handling and safety information in locomotive cabs. The Train Information Systems is composed of a Basic System and related optional features that shall utilize communications frequencies available under Federal Communications Commission (FCC) and Department of Communications (DOC) rules. All equipment shall comply with all applicable regulatory requirements.

2.

The purpose of these guidelines is to outline various characteristics of devices to transmit information between the rear-car and the controlling locomotive cab of freight trains. The need for performance guidelines arises because of the substantial advantage of avoiding development of locomotive cab and rear-car units that are incompatible in their ability to transmit messages to any other designated unit or receive messages from any other designated unit. It is also important to ensure that these systems do not cause undesirable communications interference with systems on other trains. Compatibility shall ensure that run-through motive power or train consists which exist, or may develop with further rationalization of the railroad system, shall not be impeded.

3.

For the foregoing reasons, the features of these performance guidelines that shall be considered mandatory for any system designed to operate at the prescribed frequencies are the message coding, format and protocol used in transmissions and the rear brake pipe pressure threshold status information. Other features of these guidelines are recommended in the belief that they shall prove to be useful aids to operations. These suggested features should not be considered mandatory in the abovementioned sense.

4.

These performance guidelines are intended to maximize the alternatives available to manufacturers in using whatever compatible equipment they judge to offer the most attractive combination of features, performance, maintainability, reliability, weight, etc. to purchasers.

5.

The existence of these performance guidelines does not imply that Train Information System devices are necessary for any type of freight service nor do they imply that other devices should or could not be used at other frequencies with this or any other transmission format acceptable to the FCC or DOC.

6.

Opinions will vary among railroads regarding the information desired in locomotive cabs, the detail and accuracy of displays, and even the desire for optional features as discussed in Section D. of this document. For this reason, the features that the majority of railroads consider necessary to provide a minimum compatible system for run-through trains are defined as the BASIC SYSTEM. Additional features not absolutely necessary for

_____________________________________________________________________________ -1–

AREMA® C&S Manual

Part 22.3.1 2002 compatible run-through trains are considered OPTIONS. The main purposes for describing the technical features of these Options are:

7.

B.

a.

To suggest the direction of further development of compatible systems by railroads who wish to obtain features beyond the Basic System.

b.

To ensure that the installation of such options on locomotives or as features of the rear-car devices does not prevent equipment so modified from operating with Basic System equipment such that reduces the capability of the basic unit in any way. This requirement is termed "upward compatibility."

A further consideration arises from the current U.S. Department of Transportation requirement for a lighted rear-car marker and through the possible advantages of a common power source for the information and marker systems. It is not the intention of this guideline to attempt to resolve the issue of rear-car marker regulations that differ between federal jurisdictions in the United States, Canada and Mexico. Discussion of a rear-car marker device is explanatory and is not intended as a mandatory requirement, nor is it specifically recommended as a part of the Train Information System.

Basic System This section covers the technical and performance characteristics of the Basic Train Information System. The Basic System will be composed of two units. The Train Information System rear-of-train unit shall be located on the last car of the train and hereafter referred to as the "rear unit" in this document. The second unit that shall receive and display rear car information to the engineer in the locomotive cab shall commonly be referred to as the "cab unit." The message formats and protocol provisions that shall govern data transmissions between the rear and cab units shall be commonly referred to as "communications." Rear unit features are discussed in the next section. 1.

Basic System Rear Unit: The rear unit shall determine the status of brake pipe pressure above or below a preset brake pipe pressure threshold value and transmit this information to the cab unit for display to the locomotive engineer. The rear unit shall be designed for continuous duty service on the rear of trains. The design of the rear unit shall consider the nature and consequences of possible system failure modes in such a way that a fault tolerant design results. a.

Measurement Device: (1)

A Brake Pipe Pressure (BPP) threshold sensing device is required. The pressure threshold shall be set at nominal 45 psig on decreasing pressure; accuracy " 3 psig.

(2)

A means of locally inspecting the brake pipe pressure outside of the enclosure is highly desirable. Either an integral air pressure indicating device (0-125 psig) or a

______________________________________________________________________________ -2–

AREMA® C&S Manual

2002

Part 22.3.1 quick-disconnect coupling for an external indicating device could be used. (3)

A test fitting, to an appropriate tap size, is desirable. This fitting could be used with a gauge testing device or a second air gauge to accuracy of the integral air gauge, if used.

(4)

A glad hand coupling in accordance with AAR Standard S4911 is required, arranged as necessary to connect rear unit to the train line. Provisions must be included to maintain the coupling of glad hand fittings in a vibration environment.

(5)

A "bleeder valve" is required in the rear unit. This valve shall permit the release of any air under pressure from the rear car unit and/or associated air hoses prior to detaching the device from the train line.

(6)

An internal failure of the measurement device shall not cause an undesired emergency brake application.

(7)

No equipment damage shall occur with pressures up to 200 psig.

b.

Reporting Rate: Multiple data transmissions shall occur immediately following detection of a change of status of the pressure threshold sensing device. During periods of no pressure threshold status change, transmission will be controlled by a randomized interval timer that will be set to generate a message at intervals of 55-65 sec. (nominal 60 sec. time between messages). The randomized interval timer will be reset following each transmission.

c.

Electrical Guidelines: (1)

Input Power for Rear Unit: Power for the rear unit will be provided by removable, internal battery(ies) using universal terminal connectors. It is highly desirable to have a battery minimum operating life of 72 hr. with the optional marker light included in the Basic System. Changing batteries shall not require the use of tools.

(2)

Power for Communications Equipment: Input Voltage: 13.6 volts dc ± 20%, negative ground.

(3)

Transient Over-voltage Protection: Transient energy must be suppressed to not more than 130 percent of the nominal input voltage.

1

Association of American Railroads Mechanical Division, Manual of Standards and Recommended Practices, Section E, Standard S-491, "Air Brake Hose Coupling ‘Dual Fitting.’"

_____________________________________________________________________________ -3–

AREMA® C&S Manual

Part 22.3.1 (4)

d.

Characteristics of the Operating Environment: The rear unit must meet all performance requirements specified herein under all the following environmental conditions and also remain undamaged under the specified non-operating (storage or transport) environmental conditions. (1)

Temperature (ambient at device): (a)

Full performance: -40°F (-40°C) to +140°F (60°C)

(b)

Operation: -40°F (-40°C) to +140°F (60°C)

(c)

Storage/Transport: -40°F (-40°C) to +140°F (60°C)

(2)

Relative Humidity: 95 percent non-condensing at +122°F (+50°C)

(3)

Altitude: 12,000 ft MSL

(4)

Vibration:

(5) e.

2002 Spurious Energy: Conducted spurious energy shall not cause carrier to be deviated by more than 40 dB below test tone level. Shall comply with regulatory requirements.

(a)

Vertical & Lateral:

1 to 15 Hz, 0.5 g peak to peak 15 to 500 Hz, 5 g peak to peak

(b)

Longitudinal:

1 to 15 Hz., 3 g peak to peak 15 to 500 Hz., 5 g peak to peak

Shock: 10 g peak for 10 millisec. in any axis.

Physical Guidelines: (1)

Size: As required.

(2)

Weight:

A maximum 35 lb is recommended.

(3)

Exterior:

A durable finish is required.

(4)

Mounting:

In trailing end of rear car coupler knuckle area.

(5)

Security:

Device locked to car with switch lock.

(6)

Enclosure: Sealed for service environment, lockable cover, high security cabinet with a pressure relief safety valve to avoid explosion from high pressure leak inside enclosure.

______________________________________________________________________________ -4–

AREMA® C&S Manual

2002 f.

Communications Equipment for Rear Unit: (1)

Modulator: See Section B.3., Communications

(2)

Radio Transmitter

(3) g.

Part 22.3.1

(a)

Frequency: 457.9375 MHz.

(b)

RF Power Output (pursuant to current regulatory requirements): 2 Watts.

(c)

Modulation Designation: 16K0F2D/9Y Peak Deviation of Mark and Space Frequencies: ±3.0 KHz

(d)

Spurious: 60dB Minimum below carrier.

(e)

Deviation: Flat within ±0.5 dB from 300 to 3,000 Hz. relative to 1,000 Hz.

(f)

Transmitter Rise Time: Shall not exceed 5ms for 90% Power and frequency within 1 kHz.

Antenna: Shall be attached to the rear unit.

Rear Unit Identification Provisions: Each rear unit shall be assigned a unique identification code that shall be transmitted along with the pressure threshold message to the cab unit. This code ensures that only data transmitted from the assigned rear unit shall be accepted by the cab unit. In this way, rear unit messages from adjacent trains shall be rejected by the cab unit. In order to maintain the interchangeability between rear units and cab units, the identification code shall be reported and selected at the cab unit prior to the start of any train trip. The unique identification code or "address" shall be in the range 00000 to 99999 and be established in the rear unit electronics by solder strapping or other permanent and secure means. The identification code shall also be clearly indicated on the exterior of the rear unit enclosure. The assignment of identification codes shall be made by the Central Train Information Systems clearinghouse upon written application by a railroad or manufacturer. Once assigned, an identification code number shall remain in effect on the specified rear unit until written notification is given to the clearinghouse by the owning railroad stating that the device is not, and no longer will be, in service. Under no circumstances shall any railroad or manufacturer utilize an identification code not properly assigned by the clearinghouse. Sufficiently large blocks of identification codes shall be assigned to the manufacturers to allow them to utilize proprietary bits and to recognize their equipment.

_____________________________________________________________________________ -5–

AREMA® C&S Manual

Part 22.3.1 2002 2. Basic System Cab Unit: The cab unit shall receive data messages from the rear unit and display information to the locomotive engineer. The receiver and cab display unit located in the locomotive cab shall be designed for continuous duty service. The design of the cab unit shall consider the nature and consequences of possible system failure modes so that a fault tolerant design results. a.

b.

Cab Display: (1)

Cab displays for the Basic System shall be two indicators that will display the status of rear brake pipe pressure above or below the selected threshold. The display indicators and markings shall be clearly visible and legible from the locomotive engineer's seat position under cab lighting conditions ranging from full sunlight to night illumination. A brightness control shall be provided.

(2)

Display functions are as follows: One display indicates BPP at or above preset threshold brake pipe pressure (i.e., the "Go" condition). The second display indicates BPP below preset threshold brake pipe pressure (i.e., the "No Go" condition). If no communications are received for more than 5 min., the indication of the most recent valid information shall flash until manually reset or communication is restored. If the system is not operating properly (i.e., cab unit or rear unit inoperative or power off), all displays shall be off. If colors are used with display indicators, amber shall indicate below threshold pressure and green shall indicate at or above threshold pressure.

(3)

An audible alarm shall be provided which can be clearly detected in the noise environment of the locomotive cab. The alarm shall sound for 5 sec. duration, or until reset, whenever BPP drops below threshold pressure or communications are lost for more than 5 min.

(4)

Any system cab display shall be capable of displaying the minimum system "Go" and "No Go" status indications regardless of which additional options have been installed on either the rear unit or the cab unit.

(5)

A cab unit equipped to display optional information, shall not present false information upon receipt of a Basic System message from the rear unit.

Connections: (1)

Power Connectors: See AAR Standard S-5002 for connector and pin assignments.

2

Association of American Railroads Mechanical Division, Manual of Standards and Recommended Practices, Section F, Standard S-500,"Communication Module Application - Locomotive Control Stand."

______________________________________________________________________________ -6–

AREMA® C&S Manual

2002

Part 22.3.1 See AAR Standard S-5002 for

(2)

Antenna Connectors: connector assignment.

(3)

Data Connectors: See AAR Standard S-5002 Section 8.2 regarding External Remote Connector. Data connector use and pin assignments shall be defined by the Central Train Information System clearinghouse on the basis of future system requirements. Twelve pins are reserved.

c.

Reporting Rate: Data messages from the rear unit, or repeater stations where applicable, can be expected to arrive at the cab unit at any point in time.

d.

Electrical Guidelines: (1)

(2)

(3) e.

Input Power for Cab Unit equipment shall operate from either of the following voltages: (a)

13.6 volts dc ± 20 percent, negative ground

(b)

72 volts dc nominal, 60 to 80 volts dc operating range, floating ground, from the locomotive auxiliary electrical system

Transient Overvoltage Protection: (a)

13.6 volt system: 130% of the nominal input voltage for 5 sec.

(b)

72 volt system: 5 KV for 10 ms, 90 volts for 5 sec.

Dielectric Strength: 750 volts for 1 min., any circuit to enclosure.

Characteristics of the Operating Environment: The cab unit shall meet all the performance requirements specified herein under all the following environmental conditions and also remain undamaged under the specified non-operating (storage or transport) environmental conditions. (1)

Temperature (ambient at device) (a)

Full Performance: +32°F (0°C) to +140°F (60°C)

(b)

Operation: +32°F (0°C) to 140°F (60°C)

Also see, AREMA C&S Manual, Part 22.2.1 (Recommended Design Criteria/Functional Guidelines for Interface of Radio Communications Module in "Clean Cab" Locomotive) that is an equivalent standard for this purpose.

_____________________________________________________________________________ -7–

AREMA® C&S Manual

Part 22.3.1 (c)

2002 Storage/Transport: -40°F (-40°C) to 140°F (60°C)

Note: The above temperature ranges assume that a cab unit will be located in the locomotive cab area. If not, the -40°F (-40°C) temperature requirement applies as the lower limit in above cases. Conditioning of the internal environment of the enclosure will be permitted on a case-by-case basis. In such cases, a maximum time of 10 min. shall be allowed to condition the equipment to a temperature range consistent with human operator temperature tolerance before operation must commence. (2)

Relative Humidity: 95 percent non-condensing at +122°F (50°C)

(3)

Altitude: 12,000 ft above MSL

(4)

Vibration:

(5)

f.

(a)

Vertical & Lateral:

1 to 15 Hz, 0.5 g peak to peak 15 to 500 Hz, 5 g peak to peak

(b)

Longitudinal:

1 to 15 Hz, 3 g, peak to peak 15 to 500 Hz, 5 g peak to peak

Shock: (a)

Vertical and Lateral: 2g peak for 10 millisec.

(b)

Longitudinal: 5g peak for 10 millisec.

Physical Guidelines: (1)

Dimensions: Dimension and mounting in accordance with AAR Standard S-500

(2)

Displays may be integral with the cab unit enclosure, installed in the locomotive control stand, or separately packaged and mounted per specifications (e.g., mounted on top of the control stand). If the display is separated from the enclosure, it shall be connected using manufacturer-supplied cables.

______________________________________________________________________________ -8–

AREMA® C&S Manual

2002 (3)

g.

Communications Equipment For Cab Unit: (1)

Demodulator: See Section B.3.

(2)

Radio Receiver: (Must comply with applicable regulatory requirements)

(3) h.

3.

Part 22.3.1 AAR Clean Cab Criteria: Any exposed enclosure corners shall conform to the radius standards described in AAR Standards S-528 3.

(a)

Frequency: 457.9375 MHz.

(b)

Sensitivity: 0.5 microvolt at 20 dBQ

(c)

Selectivity: 80 dB protection

(d)

Intermodulation Distortion: 80 dB protection

(e)

Spurious Response: 85 dB protection

(f)

Receiver Discrimination: Flat within 0.5 dB from 300 to 3,000 Hz, relative to 1,000 Hz.

Antenna: The antenna shall be suited for the environment and the mounting location chosen by the .

Unit Identification Provisions: Provisions shall be made for entry of the rear unit identification code by operating personnel each time a new rear unit is installed on the rear car of the train. The unit addresses shall be on-site selectable from 00000 to 99999 (e.g., using thumbwheel switches or other suitable means).

Communications: The following communications protocol and data message formats shall be mandatory for the Basic System. a.

General: Synchronous Transmission.

b.

Modulator/Demodulator: (1)

Modulation Technique: Continuous Phase Fast Frequency Shift Keying (FFSK)

(2)

Modulating Frequencies: Space (0) 1800 Hz ±0.5% Mark (1) 1200 Hz ±0.5%

(3)

Transmit/Receive Rate: 1200 baud ±0.5%

3

Association of American Railroads Mechanical Division, Manual of Standards and Recommended Practices, Section F, Standard S-528, "Rounding All Possible Exposed Convex Edges and Corners."

_____________________________________________________________________________ -9–

AREMA® C&S Manual

Part 22.3.1 c.

2002 Data Reporting Rate: The minimum acceptable reporting rate for a Basic System rear unit is described in Section B.1. Communications strategies that employ more frequent transmissions than that described in this section are permitted. However, these strategies shall be consistent with the guidelines set forth herein (especially battery operating life) and strive for efficient use of the radio communications link.

d.

Data Message - General: A message transmitted on the frequency(ies) specified herein shall utilize the format described in the following sections. The general format of any message to be sent is a series of blocks, of fixed length, which contain the data that is to be sent to the front of the train. This format is illustrated as:

BASIC BLOCK

OPTIONAL BLOCK 1

Length: 144 bits

Length: 144 bits

OPTIONAL BLOCK 2 Length: 144 bits

TRAIN INFORMATION SYSTEM MESSAGE FORMAT Every message sent shall always have at least one block, namely the Basic Block. Additional blocks may or may not be sent depending upon the number of optional features built into the system. At the beginning of every block in the message, a series of synchronization bits shall be sent to allow the transmitter and receiver circuitry to settle and to establish both bit and frame sync. Immediately following the synchronization bits shall be a 45 bit data sequence for the block and an 18 bit BCH error detection/correction code. The block is ended by a trailing bit that is designed to enable the receiver to reliably extract the last bit(s) in the BCH code. The total length of every message block is 144 bits. The initial block contains all the information that is sent by any Basic System. Included within this initial block is the message type identifier, the rear brake pipe pressure threshold status, rear brake pipe pressure information, motion indications, marker light status, battery(ies) condition, and other discretionary information. Following the Basic Block are Optional Blocks that contain the data from other optional system features that are not provided for in the Basic System message. The number of Optional Blocks, and hence the total length of the message, shall vary depending upon the number of options included in the rear unit, if any, and the strategy the manufacturer uses for transmitting data to the cab unit. Some messages sent by the rear unit, such as the Basic System message will have no Optional Blocks, since all the information to be conveyed is contained in the Basic Block. The maximum ______________________________________________________________________________ - 10 –

AREMA® C&S Manual

2002

Part 22.3.1 number of Optional Blocks allowed by the message format is four. Specific details about the message format are contained as follows. e.

Basic System Message Format: A message transmitted by the Basic System shall have the following format.

Basic Bit sync 4 Block Frame sync 4 Chaining bits Device battery condition Message type identifier Unit address code Rear brake pipe status and pressure Discretionary information Motion detection Marker light battery condition Marker light status Basic block BCH code Trailing bit Total Length

69 bits 11 bits 2 bits 2 bits 3 bits 17 bits 7 bits 11 bits5 1 bit 1 bit 1 bit 18 bits 1 bit 144 bits

Each of these items is defined in the next section, and the bitpositioning diagram corresponding to this format is given in Appendix B. f.

4 5

Basic Block Data Message Elements: (1)

Bit and Frame Sync: Immediately preceding the start of every basic block transmission, a series of sync bits shall be sent to allow the transmitter and receiver circuitry to settle, and to establish both bit timing and frame synchronization. The bit sync shall be a 69 bit pattern of alternating zeroes and ones (i.e., 0101010101...). The frame sync shall be the eleven bit marker code 01001000111, where the right most bit is the least significant bit (LSB). The frame sync code shall be transmitted LSB first. Note that the bit and frame sync patterns are not considered to be a part of the message information bits for the purpose of generating the BCH error detection/correction code.

(2)

Chaining Bits: Chaining bits are a two bit code which provide information about the position of the current data block within the overall message being received. Chaining bits indicate whether the block is the first block, the last block, or an intermediate block in the message. They may be used in conjunction with the Number of Optional Data Blocks field, described below, to locate the beginning of a

See Item B.3.f.(1) For Two-Way Systems see Section C.

_____________________________________________________________________________ - 11 –

AREMA® C&S Manual

Part 22.3.1

2002 message in case of an RF dropout. The chaining bits are encoded as follows: First Chaining Bit (MSB) 0= The block IS NOT the first block in the message 1= The block IS the first block in the message Second Chaining Bit (LSB) 0= The block IS NOT the last block in the message 1= The block IS the last block in the message Thus, a system that transmits only the Basic System message shall encode the chaining bits as binary 11. A more advanced system sending a Basic Block plus two Optional Data Blocks, for example, shall have chaining bits in each message block encoded as binary 10, 00, and 01. The chaining bits shall be sent LSB first. (3)

Device battery condition: Two bits shall be assigned to monitor the device battery status as follows: MSB LSB 1 1 = Device battery OK 1 0 = Device battery weak 0 1 = Device battery very weak 0 0 = Device battery condition not monitored The LSB will be sent first.

(4)

Message Type Identifier: The second element to be transmitted is a three bit code which defines the type of message being transmitted. This information shall be used by the cab unit to identify the format of the message received and enable correct decoding of the contents. Messages from the rear unit of one-way systems shall contain a message type identifier code of zero (0), or 000 in binary. The message type identifier shall be sent LSB first. Other message type identifiers shall be defined in the future by the Train Information System clearinghouse when requested. These additional message type identifiers could be used for messages from wayside devices to train, or from front to rear of train.

(5)

Rear Unit Address Code: The rear unit’s unique address code shall be the fourth item transmitted in the data message. This code number will be within the range 00000 to 99999 and, therefore, shall require seventeen bits. The address code shall be expressed in binary and sent LSB first.

(6)

Rear Brake Pipe Status and Pressure: This seven bit message element contains the information about the brake

______________________________________________________________________________ - 12 –

2002

AREMA® C&S Manual

Part 22.3.1 pipe pressure status and brake pipe pressure data, if the rear unit is configured to measure continuous quantitative pressure. The rear brake pipe status and pressure information shall be expressed in binary and transmitted LSB first. For a Basic System, which only monitors brake pipe pressure above or below the threshold, the status information is sent using the codes 126 and 127 expressed in binary. If the actual brake pipe pressure at the rear unit is below the established threshold (i.e., 45 psig.) the status value shall be 126. If the actual brake pipe pressure is greater than or equal to the selected threshold level, then the status code shall be 127. Advanced units equipped to measure quantitative rear brake pipe pressure shall use this field in a slightly different manner than discussed in the previous paragraph. The brake pipe pressure shall be encoded as a seven bit unsigned binary integer, where one bit represents 1 psig. The allowable range of brake pipe pressures for advanced systems shall be from zero (0) to 125 psig. In this case, the "GO" or "NO GO" brake pipe pressure status shall be deduced in the cab unit by examining the pressure value. Pressures in the range 45 to 125 psig reflect the "GO" status, while pressures 44 psig. and below indicate a "NO GO" brake pipe pressure status. The table below summarizes the coding and interpretation of the combined brake pipe status and pressure field: Coded Value (Decimal Representation) Interpretation__ 127 "GO" condition from a Basic System rear unit. Brake pipe pressure is at or above threshold pressure. 126

“NO GO" condition from a Basic System rear unit. Brake pipe pressure is below threshold pressure.

45 through 125

Actual rear brake pipe pressure value from an advanced system. Pressure at rear unit is at or above threshold pressure (i.e ., a "GO" condition).

0 through 44

Actual rear brake pipe pressure value from an advanced system. Pressure at rear unit is below

_____________________________________________________________________________ - 13 –

AREMA® C&S Manual

Part 22.3.1

2002 threshold pressure (i.e., a "NO GO" condition).

(7)

Discretionary Information: Eleven bits shall be used for discretionary information in one -way systems, at the option of the manufacturer. The use of these bits will be submitted to the Central Train Information System clearinghouse, who shall maintain a record of such on file. All bits not assigned shall be coded as zeroes (0).

(8)

Motion detection: One bit shall be assigned to indicate whether or not the rear car of the train is in motion as follows: 1 = Rear car in motion 0 = Rear car stopped or not monitored

(9)

Marker light battery condition: One bit shall be assigned to monitor the marker light battery status as follows: 1 = Marker light battery weak 0 = Marker light battery OK or not monitored

(10)

Marker light status: One bit shall be assigned to indicate whether or not the marker light is lit as follows: 1 = Marker light on 0 = Marker light off or not monitored

(11)

Basic Block BCH Code: The basic block BCH code is an 18 bit error detection/correction code for the basic block portion of a message. The BCH code is of the 63,45 type. It shall be computed at the time a message is transmitted by dividing the message block information bits by the generator polynomial g(x) = (18, 17, 16, 15, 9, 7, 6, 3, 2, 1, 0) The remainder is Exclusively OR'ed with the eighteen bit code and the result becomes the quantity that is sent. MSB LSB 000011101110110101 The bit and frame sync patterns are not considered part of the block information bits and, therefore, are not included in the BCH code generation process. The BCH Code shall be sent LSB first.

(12)

g.

Trailing Bit: One "trailer" bit shall be added to the end of the Basic Block to enable the last data bits to be reliably received at the cab unit. This bit shall be a one (1).

Basic Block Plus Optional Data Block(s): Train Information System units equipped with options over and above those provided for in the Basic Block shall use additional message blocks to transmit data. The Basic Block is always the first block in the message,

______________________________________________________________________________ - 14 –

AREMA® C&S Manual

2002

6

Part 22.3.1 however. The general format for all Train Information System units will be: Basic Bit sync Block Frame sync Chaining bits Device battery condition Message type identifier Unit address code Rear brake pipe status and pressure Discretionary information Motion detection Marker light battery condition Marker light status Basic block BCH code Trailing bit Total length

69 bits 11 bits 2 bits 2 bits 3 bits 17 bits 7 bits 11 bits6 1 bit 1 bit 1 bit 18 bits 1 bit 144 bits

Optional Block(s)

69 bits 11 bits 2 bits 1 bit 42 bits 18 bits 1 bit 144 bits

Bit sync Frame sync Chaining bits Block format indicator bit Optional block data bits Optional block BCH code Trailing bit Total length (1)

Basic Block Elements: All elements of the Basic Block are described in the previous Section B.3.f.

(2)

Optional Block(s) Bit and Frame Sync: Immediately preceding the start of every optional block transmission, a series of sync bits shall be sent to allow the transmitter and receiver circuitry to settle, and to establish both bit timing and frame synchronization. The bit sync shall be a 69 bit pattern of alternating zeroes and ones (i.e., 0101010101...). The frame sync shall be the eleven bit marker code 01001000111, where the right most bit is the least significant bit (LSB). The frame sync code shall be transmitted LSB first. Note that the bit and frame sync patterns are not considered to be a part of the message information bits for the purpose of generating the BCH error detection/correction code.

(3)

Chaining Bits: The two chaining bits are coded as described in the previous Section B.3.f.(2). The chaining bits shall be sent LSB first.

(4)

Block Format Indicator Bit: This bit is used to indicate whether the data contained in the current Optional Data

For Two-way Systems see Section C.

_____________________________________________________________________________ - 15 –

Part 22.3.1

AREMA® C&S Manual

2002 Block is in binary or ASCII format. Coding for this format indicator bit shall be: 0 = Binary format for data in the block 1 = ASCII format for data in the block (a)

Data in Binary Format: If the indicator bit is zero (0), the remaining 42 bits in the data block are coded in binary using the following format: Data Type "A" Identifier 7 bits Data "A" 7 bits Data Type "B" Identifier 7 bits Data "B" 7 bits Data Type "C" Identifier 7 bits Data "C" 7 bits Total Data Length 42 bits The Data Type Identifier is a seven-bit code used to describe or designate the datum which shall immediately follow. Data type identifiers shall be established by the Central Train Information System clearinghouse and shall not be indiscriminately used by a railroad or supplier in an unauthorized manner. Valid data type identifiers shall be in the range of one (1) to 127, expressed in binary representation. Data type identifier zero (0) is a special code and is discussed below. The data type identifier shall be sent LSB first. The data item appears in conjunction with the data type identifier and contains the information about a particular rear unit parameter associated with one of the optional features of the Train Information System. Generally speaking, each parameter the rear unit reports shall be contained in a separate Data Type Identifier with Data Item pairing, however, some data shall be "packed together" to form related pieces of information to "fill-up" a message element. The coding of each data type shall be defined in the future by the clearinghouse, as requirements arise. Individual data quantities shall be transmitted LSB first. It should be noted that there is no requirement that all the information that a rear unit could potentially transmit must actually be transmitted when a data message is sent to the cab unit. Any sequence or combination of data parameters may be transmitted, and in any order, so long as the basic rules of message organization are fulfilled. That is, the data type identifier shall precede the datum it describes. In this manner, it is possible for the rear unit equipped with optional features to determine which parameters

______________________________________________________________________________ - 16 –

AREMA® C&S Manual

2002

Part 22.3.1 shall be transmitted to the cab unit at the time of a transmission and thereby minimize use of the radio transmitter. If a rear unit does not require all 42 bits in the Optional Block data field to transmit its information, additional bits shall be sent to fill the block to the 42 bit length. This shall be accomplished by using Data Type Identifier zero (0) as a special indication for the "no data" situation. The associated data item shall also be sent as zero (0), or 0000000 in binary.

(b)

(5)

Data in ASCII Format: If the Optional Block format indicator bit is a one (1), the following 42 data bits are coded as six seven-bit ASCII characters. Appendix A provides additional information regarding the transmission of ASCII characters in a message.

Optional Block BCH Code: The Optional Block BCH code is the error detection/correction code for the data portion of a message. It shall be computed at the time a message is transmitted by dividing the data block information bits by the generator polynomial. g(x)=(18, 17, 16, 15, 9, 7, 6, 3, 2, 1, 0) The remainder is Exclusively OR'ed with the eighteen-bit code and the result becomes the quantity that is sent. MSB LSB 000011101110110101

(6)

h.

Optional Block Trailing Bit: One "trailer" bit shall be added to the end of any optional data block to enable the last data bits to be reliably received at the cab unit. This bit shall be a one (1).

Message Error Detection and Correction Techniques: A combination of message repetition and error code checking shall be used to provide the reliability necessary for Train Information System communications. These concepts are discussed in the following paragraphs. (1)

Rear Unit Transmission Requirements: A data message sent by the rear unit shall be sent at least twice. The rear unit must transmit the first message in its entirety before the second repetition of the message is sent. That is, all blocks of the first message shall be transmitted before any repetition of blocks are sent. A manufacturer may elect to transmit the message more times than these guidelines require.

_____________________________________________________________________________ - 17 –

AREMA® C&S Manual

Part 22.3.1 (2)

2002 Cab Unit Receiving Requirements: The capability to detect invalid data is provided by the BCH codes in the message. A BCH code shall be generated by the cab unit for each information block, respectively, using the techniques described in previous sections. If the new BCH codes agree with the BCH codes received in the message block(s), the message may be considered valid and decoded. If, however, the BCH codes do not agree, the message shall be considered in error and may be disregarded by the cab unit or, at the discretion of the manufacturer, corrected to become va lid. The communications guidelines described in this document do not prohibit a manufacturer from using additional error correction techniques, such as "bit averaging" techniques, that may be afforded by multiple repetitions of the message.

C.

Application of Train Brakes from Rear Car The following general assumptions have been made to formulate the guidelines for end-of-train braking systems: The rear emergency valve is regarded as a backup device, not a braking performance improvement device. The probability of two trains trying to apply emergency brakes at the same time is very low. A failure of the system shall not cause application of the emergency brakes. A 1 sec. delay between the command to apply rear emergency brakes and the rear valve's activation is acceptable. A requirement for rear of train braking necessitates the provision of two-way communication. Guidelines for two-way transmission given below supplement guidelines in Sections A. and B. Additional Features - Rear Unit: The addition of two way transmission to the rear unit described in Section B. will provide the additional capability of applying the brakes, restoring normal brake operation, transmission of status information and testing the communications channel on receipt of a command. 1.

Brake Application: The front-to-rear transmission and rear-of-train equipment shall provide for application of train emergency air brakes upon manual selection by the locomotive engineer. a.

An emergency brake application command from the front unit shall activate the emergency air valve typically within one sec.

______________________________________________________________________________ - 18 –

AREMA® C&S Manual

2002 b.

Part 22.3.1 The rear unit shall send an acknowledgment message to the front unit immediately upon receipt of a brake application command. The front unit shall listen for this acknowledgment and repeat the brake application command if the acknowledgment is not correctly received.

c.

The rear unit, on receipt of a properly coded command, will open a valve in the brake line and hold it open for a minimum of 15 sec. This opening of the valve shall cause the brake line to vent to the exterior.

d.

The valve opening and hose diameter shall have a minimum diameter of 3/4 in. to effect an emergency brake application.

e.

Restoring of the braking function (recharging the air brake system) shall be enabled automatically by the rear equipment, no more than 60 sec. after it has initiated an emergency release.

2.

Transmission of Status Information: The rear unit shall transmit the latest status information on receipt of properly coded request. The transmission of the status information will reset the randomized interval timer.

3.

Power Requirements: The radio receiver and data equipment shall be powered from the same battery pack as the rear unit described in Section B.1.c. and shall still meet all the requirements of Section B.1.

4.

Environmental Requirements: The rear unit equipped with two-way transmission shall meet all the environmental guidelines specified in Section B.1.d.

5.

Additional Radio Receiver for Rear Unit: a.

Demodulato r: See Section B.3., Communications

b.

Radio Receiver: (1)

Frequency: 452.9375 MHz

(2)

Sensitivity: 0.5 microvolt at 20 dBQ

(3)

Selectivity: 80 dB protection

(4)

Intermodulation Distortion: 80 dB protection

(5)

Spurious Response: 85 dB protection

(6)

Receiver Discrimination: Flat within +/-0.5 dB from 300 to 3,000 Hz, relative to 1,000 Hz.

_____________________________________________________________________________ - 19 –

AREMA® C&S Manual

Part 22.3.1 (7) (8)

6.

2002 The receiver shall use the same antenna as the rear unit transmitter, with suitable T/R switching provisions. The address code of the receiver shall be the same as set for the rear unit identification code described in Section B.1.g.

Communications Rear to Front: The communications protocol and data message formats for rear to front message exchanges shall be identical to that specified under Section B. with the exception that two bits of information are now removed from the discretionary field to become defined. The changed information, together with a new bit-positioning diagram are detailed below. a.

b.

Message Format Rear to Front Communications: A message transmitted by the rear unit shall have the following format: Bit sync 7 Frame sync 5 Chaining bits Device battery condition Message type identifier Unit address code Rear brake pipe status and pressure Discretionary information Valve circuit status Confirmation indicator Discretionary information Motion detection Marker light battery condition Marker light status Basic block BCH code Trailing bit

69 bits 11 bits 2 bits 2 bits 3 bits 17 bits 7 bits 8 bits 1 bit 1 bit 1 bit 1 bit 1 bit 1 bit 18 bits 1 bit

Total Length

144 bits

Additional Defined Bits: The two new bits are defined below and the new bit positioning diagram corresponding to this format is given in Appendix C-1. (1)

Valve Circuit Status - One bit is assigned to indicate the status of the Emergency Valve Circuit: 0 = Emergency Valve Circuit failed 1 = Emergency Valve Circuit operational

(2)

7

Confirmation Indicator - One bit is assigned to differentiate between normal updates and responses to requests from the Cab Unit:

See Item B.3.f.(1) of basic system

______________________________________________________________________________ - 20 –

AREMA® C&S Manual

2002

0= 1=

7.

Part 22.3.1 Rear Unit transmission is a normal update Rear Unit transmission is in response to a request from the Cab Unit

c.

Additional Timing Requirement for Two-Way Operation: When the confirmation bit is set to 1, i.e. when the Rear-to-Front message occurs in response to a Front-to-Rear trans mission, the bit sync of the Rear-to-Front message must begin between 12 to 18 millisec. after the end of the Front-to-Rear message.

d.

Discretionary Information: Nine bits will be used for discretionary information at the option of the manufacturer. The use of these bits will be submitted to the clearinghouse, who shall maintain a record of such on file. All bits not assigned shall be coded as zeroes (0).

e.

Optional Data Blocks: Timing constraints between messages does not permit the use of additional optional data blocks, in the two-way system, for transmission of additional information.

Additional Features - Cab Unit: The addition of two-way transmission to the front equipment described in Section B.2., shall provide the additional capability of applying the emergency brakes at the rear end of the train, via an emergency air dump valve, activate by remote control. The capability of requesting transmission of status information from the rear unit and of testing the communications channel shall also be provided. a.

Manual Emergency Brake Activation: The Cab Unit will have a switch which, when activated, shall initiate a front-to-rear transmission containing an emergency brake application command. On receipt of this command, the brakes shall be applied at the Rear Unit. The switch, distinctively labeled "EMERGENCY", shall be protected, so that there shall exist no possibility of accidental activation.

b.

Manual Communications Test: Means shall be provided for manual initiation of an end-to-end test of the front-to-rear communications link with a visual/audible indication of success or failure of the test. Activation of a manual, communications link test shall simultaneously set a distinctive symbol on the display and transmit a request for an update of the status information from the rear unit. The distinctive symbol will be cleared when the new status information (containing the confirmation indicator Bit = 1) is received in the following rear-tofront transmission. This indicator is also cleared by any subsequent successful front-to-rear/rear-to-front confirmation cycle.

c.

Automatic Communications Test: The availability of the front-to-rear communications link shall be checked automatically at least every 10 min.

_____________________________________________________________________________ - 21 –

Part 22.3.1 d.

e.

f.

AREMA® C&S Manual

2002

Emergency Valve Test: Means shall be provided to confirm availability and proper functioning of the emergency valve as part of both the manual (item b) and automatic (item c) communications tests. Rear to Front Communications Failure: (1)

The cab unit shall be so designed that if no rear-to-front transmission is received for a period of 196 sec. a request shall automatically be transmitted to the rear unit for an update of status information. If a message has not been received after this request, another request shall be sent 15 sec. after the first. If no communication is received for a period of 326 sec., another status update request shall be transmitted to the rear unit. If, after 15 sec., no status update has been received, another status update request shall be transmitted. If after this fourth status update request no status update has been received, Rear-to-Front communication failure shall be declared.

(2)

Display or indication of Rear-to-Front communication failure shall take precedence over Front-to-Rear communication failure.

Front-to-Rear Communications Failure: Every 10 min. a status update request shall automatically be sent to the rear unit. If no status update is received as a result of this transmission, (i.e. with confirmation bit = 1) a second request shall be sent 15 sec. later. If still no status update has been received, a third request shall be repeated 6 min. later. If still no status update has been received, a fourth request shall be sent 15 sec. later. If after the fourth update request no update has been received (with confirmation bit = 1), then Front-to-Rear communication failure shall be declared. This warning shall be reset by the next successful front-to-rear/rear-to-front confirmation cycle (automatically or manually initiated). Front-to-rear communication failure shall also be tested and declared during an attempted emergency activation (Item C.7.a.).

g.

Front-to-Rear Message Retries: The cab unit will handle data message retries as follows: (1)

For emergency brake application commands, the retries shall continue until a status update indicates that the rear unit has received the command by setting the confirmation bit in the update. Thereafter if the rear brake pipe pressure has not been reduced to a level below 5 psi within 4 sec., another retry shall be made and again the confirmation bit looked for. This process shall repeat up to a maximum time of 2 min. after the last emergency switch activation. If a

______________________________________________________________________________ - 22 –

AREMA® C&S Manual

2002

Part 22.3.1 confirmation bit has not been received within 15 sec. of the initial or a 4 sec. retry emergency command, front-to-rear communication failure shall be declared. (2)

For manually initiated status information update requests, the cab unit shall not transmit any retries automatically, nor cause a communication failure indication.

h.

Power Requirements: The additional radio transmitter and data equipment shall be powered from the same power source as the cab unit receiver described in Section B.2.d.

i.

Environmental Requirements: The additional equipment included in the cab unit for two way transmission shall meet the environmental guidelines described in Section B.2.e.

j.

ID Code: The ID code transmitted by the cab unit transmitter shall be identical to that selected for message reception from the rear detailed in Section B.2.h.

k.

Additional Radio Transmitter for Cab Unit: (1)

Modulator: See Section B.1. Communications

(2)

Radio Transmitter (a)

Frequency: 452.9375 MHz

(b)

RF Power Output: RF power of the Front-to-Rear radio link shall be 2 watts nominal unless a greater power output is permitted by regulatory authorities, throughout the operating territory of the equipment. Nominal radio power under any circumstances shall not exceed 8 watts.

(c)

Modulation Designation:

16K0F2D/9Y

Peak Deviation of Mark and Space Frequencies: +/-3.0 KHz. (d)

Spurious:

60 dB Minimum below carrier

(e)

Deviation: Flat within +/-0.5 dB from 300 to 3,000 Hz, relative to 1,000 Hz.

(f)

Transmitter Shall not exceed 5 ms for 90% Rise Time: power and frequency within 1 KHz

_____________________________________________________________________________ - 23 –

AREMA® C&S Manual

Part 22.3.1

8.

(g)

2002 The transmitter shall use the same antenna as the cab unit receiver with suitable T/R switching provisions.

(h)

The transmitter identification code shall be the same as that selected in Section B.2.h.

Communications Front to Rear: The following communications protocol and data message formats shall be mandatory for the front to rear communications link. a.

Governing Factors: The following items were considered when formulating the guidelines for the front to rear protocol. (1)

Since the front to rear communications protocol now concerns a control function as well as telemetry, additional code security is desirable.

(2)

An emergency brake application command from the front unit shall activate the emergency air valve typically within 1 sec.

(3)

The front-to-rear radio link shall achieve a single transmission success rate of 98% or better, averaged over typical railroad operating terrain, for a train length of 5,000 ft. The intent of this requirement is for this link to have the same performance in of throughput, as the Rear-toFront link.

(4)

To enable functioning of two-way telemetry on more than one train in close proximity (radio range), no unit can be allowed to flood either radio channel, with a long continuous burst of message transmission.

(5)

Performance of Rear-to-Front communication shall not be degraded by the Front-to-Rear link.

b.

General: Synchronous transmission

c.

Modulator/Demodulator: The modulation scheme shall be identical to that described in Section B.1.3., for the one way system.

d.

Transmission: The Front-to-Rear radio channel shall operate at 452.9375 MHz. All other parameters describing this radio channel including band width and stability shall be as stated in the guidelines for the oneway system.

______________________________________________________________________________ - 24 –

AREMA® C&S Manual

2002 e.

f.

Transmission Format Front to Rear Communications: Any message sent from the front unit to the rear unit, shall utilize the format described in the following sections: (1)

Each message shall consist of three identical data blocks.

(2)

At the beginning of the message (before first data block only) a series of synchronization bits shall be sent to allow the transmitter and receiver circuitry to stabilize and to establish both bit and frame sync.

(3)

Immediately following the synchronization bits, shall be a 30 bit data sequence for the block followed by a 33 bit BCH error detection code.

(4)

Each data block is followed by a single odd parity bit.

(5)

The total length of each message is 672 bits.

Message Format Front to Rear Communications: A message transmitted by the front unit shall have the following format: Bit Sync Frame Sync Data Block Odd Parity Bit Data Block (Repeat #1) Odd Parity Bit Data Block (Repeat #2) Odd Parity Bit Total length

g.

456 bits 24 bits 63 bits 1 bit 63 bits 1 bit 63 bits 1 bit 672 bits

Data Block Format: (1)

Each of the three data blocks shall have an identical format.

(2)

The format within each block shall consist of 30 information bits followed by 33 BCH error check bits conforming to the (63.30) format.

(3)

The general format of each data block is as follows: Chaining Bits Message Type Identifier ID Command word Status Request or Emergency BCH Code

h.

Part 22.3.1

2 bits (always 11) 3 bits (always 000) 17 bits 8 bits 33 bits

Message Data Block Elements: (In Order Transmitted)

_____________________________________________________________________________ - 25 –

AREMA® C&S Manual

Part 22.3.1

2002

(1)

Bit Sync: Immediately preceding the start of every basic block transmission, a series of sync bits shall be sent to allow the transmitter and receiver circuitry to settle, and to establish both bit timing. The bit sync shall be a 456-bit pattern of alternating zeroes and ones (i.e., 010101010101...)

(2)

Frame Sync: Immediately following the bit sync pattern. A frame sync code shall be transmitted to establish frame synchronization. The frame sync used shall be the 24-bit code: 1000 1111 0001 0001 0010 1001 The left bit in the above code is the LSB, transmitted first. Note that the bit and frame sync patterns are not considered to be a part of the message information bits for the purpose of generating the BCH error detection/correction code.

(3)

Chaining Bits: Chaining bits are a two-bit code which provide information about the position of the current data block within the overall message being received. Chaining bits indicate whether the block is the first block, the last block, or an intermediate block in the message. For the Front to Rear protocol, the first (and only) block is uniquely identified by the chaining bits 11, signifying only one block in the message. The left hand bit is MSB. Note that for the Front to Rear protocol, the 2nd and 3rd blocks are repeats of the first block.

(4)

Message Type Identifier: The message type identifier is a 3-bit code used to define the type of message being transmitted by the cab unit. For two-way end of train systems this code shall be all zeroes (000).

(5)

ID Code: Unique ID code of the rear unit being addressed shall be the next item in the data message. This code number will be within the range 00000 to 99999 and, therefore, shall require seventeen bits. The address code shall be expressed in binary and sent LSB first.

(6)

Command Word: The left bit in the below code is the MSB and sent LSB first. An 8-bit command word shall be used for the following two functions: (a)

Status Update request from front unit:

______________________________________________________________________________ - 26 –

AREMA® C&S Manual

2002

Part 22.3.1

01 01 01 01 (b) (7)

Emergency Brake Application 10 10 10 10

BCH Code: The BCH code used for Front-to-Rear transmissions is a 33bit detection/correction code applied only to the data portion of the block. The BCH code is of the (63.30) type and is computed at the time a message is transmitted by dividing the message block information bits by the generator polynomial: g(x)=(33,32,30,29,28,27,26,23,22,20,15,14, 13,11,9,8,6,5,2,1,0) This remainder is the result that is sent. The BCH code shall be sent LSB first. Note that the bit sync and frame sync patterns are not considered part of the block information bits and therefore, are not included in the BCH generation process.

(8)

D.

Parity Bit: An odd parity bit shall be added at the end of each data block. The bit-positioning diagram corresponding to this format is given in Appendix C-2.

Optional Features This section discusses several optional features that could be added to the Basic System. As previously indicated, the Basic System is defined as the minimum system necessary to ensure compatible operation for run-through trains. Most of the options to be discussed become feasible as a result of installing onboard the train those minimum data processing and communications capabilities provided by the Basic System. With relatively modest increases in data processing, communications, and display capabilities over and above capabilities provided by the Basic System, a number of optional features become viable. The selection of which option(s) is/are to be selected resides entirely with the acquiring railroad. Many of the options are highly desirable to some railroads. However, the various optional features described below can be added to the Basic System, if and only if, the minimum compatible operations are not in any manner compromised by the incorporation of any optional feature. The options to be discussed are as follows: Option 1 - Rear End Marker Device Option 2 - Multiple Brake Pipe Pressure Threshold Switches Option 3 - Brake Pipe Pressure Transducer Option 4 - Rear Car Movement Indicator Option 5 - Built-in Battery Charger for Rear Unit Option 6 - Rear Unit Status Monitoring

_____________________________________________________________________________ - 27 –

AREMA® C&S Manual

Part 22.3.1 2002 Option 7 - Rear Car Slack Status Detection Option 8 - Rear Car Brake Cylinder Release Detection Option 9 - Undesired Emergency Location Option 10- Emulation of Rear Car Brake Control Valve Activity Option 11- Deleted, See Section C Option 12- Automatic Initial Terminal Air Brake Test Option 13- Voice Warning and Advice Option 14- Hot Box, Dragging Equipment and Other Defects Cab Display Option 15- Train Orders Cab Display Option 16- Automatic Train Location Option 17- Mid-Train Slack and Brake Pipe Pressure Detectors Option 18- Disabled Train Warning Light Option 19- Rear Car Acceleration Indicator Option 20- Front Unit Authorization for Additional Security in Two-Way Systems It should be noted that discussions of options, is not intended to suggest that any single option or combination of options is a requirement. Each railroad should make these choices based upon its own needs and objectives. It is the intent of this section to enable the maximum opportunity to tailor the most effective Train Information System that should meet the individual needs of each using railroad. It should also be restated that any option or combination of options ins talled in any system shall not in any manner interfere with or constrain operation with a companion unit configured for Basic System capabilities. Furthermore, options shall meet applicable environmental specifications established for related Basic System units and components. The following paragraphs discuss the various options. 1.

Rear End Marker Device: A lighted rear marker device is currently required by Title 49 CFR Part 221 on trains operating in the United States. Other jurisdictions (e.g. Canada, Mexico) also have requirements that are different from those described in 49 CFR Part 221. Because of these requirements, there may be advantages for some railroads to incorporate a rear marker device as an optional feature to their basic Train Information System. This section briefly addresses the issue of a rear-of-train marker device insofar as it concerns Train Information System design. These provisions are offered only as an explanation of ideas for meeting statutory requirements with this type of system in a reasonable manner. In no way do these provisions constitute an endorsement, specification or mandatory requirement for a marker light feature in a Train Information System. If a marker device (light) is installed as an optional feature in a Train Information System, the following points should be considered: a.

The marker device be an integral part of the rear unit.

b.

All statutory requirements be met by the marker device, including Title 49 CFR Part 221 for a U. S. installation or other applicable regulation for a foreign application.

______________________________________________________________________________ - 28 –

AREMA® C&S Manual

2002 c.

Part 22.3.1 The marker device power requirements have a minimal impact on the rear unit battery life. See Section B.1.c.

d.

The operation of the marker device be unaffected by the operation of any other rear unit optional feature, within the limits of the battery life.

e.

A marker device status indication be developed at the rear unit, transmitted to the cab unit as one of the data parameters and displayed to the engineer.

f.

Ease of field servicing and reliability be emphasized in the design of the marker device.

2.

Multiple Brake Pipe Pressure Threshold Switches: An optional feature that could be incorporated into the Basic System is one or more additional pressure threshold switches. The additional pressure threshold intervals would permit additional brake pipe pressure functions. For example, a 10 psig pressure switch could be used to power down the rear unit during extended periods when Brake Pipe Pressure (BPP) was zero. Other intervals could be selected by using railroads. Additional display devices would be needed. However, these additional devices shall not interfere with the planned uses and meanings of Basic System functions and displays.

3.

Brake Pipe Pressure Transducer: Another option is addition of a continuous, quantitative BPP display in the cab. The BPP transducer shall provide 0-125 psig measurements with " 3 psig accuracy. An alphanumeric cab display could be used to present this information to the locomotive engineer. This cab display shall provide sufficient characters to present rear car brake pipe pressure to the nearest 1 psig. The display shall be legible in both bright daylight and night vision conditions in the cab. It is suggested that character height be at least 0.5 deg. of arc as viewed from the locomotive engineer's seated position. Location of the alphanumeric display unit shall avoid obstruction of the locomotive engineer's field of view. Optional display devices should also meet other applicable guidelines presented in Section B.2. Basic System Cab Displays.

4.

Rear Car Movement Indicator: Another option would provide the locomotive engineer with information about movement of the rear car. A motion-detecting device in the rear unit would encode a single bit of information in data messages. The cab unit would receive this information and use a suitable display to indicate that the rear car is moving or not moving.

5.

Built-in Battery Charger for Rear Unit: Some railroads may wish to incorporate a battery charger circuit into the rear unit to facilitate recharging of battery packs. Reliability and serviceability would be improved if personnel could simply plug in a line cord to 115 volts ac,

_____________________________________________________________________________ - 29 –

AREMA® C&S Manual

Part 22.3.1 2002 which would recharge battery packs at the correct voltage and charging rate. 6.

Rear Unit Status Monitoring: The reliability and maintainability of the rear unit would be enhanced by built-in performance monitoring. This performance monitoring feature could monitor the status of the sensing device, battery voltage, and other optional features which may be added to the rear unit. Status information could be displayed in the cab and/or recorded for self-diagnosis, sensor calibration, and maintenance.

7.

Rear Car Slack Status: Another optional feature for Train Information Systems is the reporting of slack conditions between the last two cars in a train. An elementary rear car slack status indicator would simply determine the slack state as either being in a draft or buff condition and display this status in the cab. A slightly more sophisticated rear car slack status indicator would not only determine the buff/draft slack state but also estimate the magnitude of the coupler forces.

8.

Rear Car Brake Cylinder Release Detection: Train handling and completion of terminal air test could be improved if a positive and reliable method were devised to detect brake application and release at the rear car. This could be accomplished by using a movement/motion sensor on the brake cylinder piston or brake beam.

9.

Undesired Emergency Location: The cause of undesired emergency applications of train brakes (UDE) may occasionally be difficult to identify because of the inability to isolate the source of the problem at the time of occurrence. "Kickers" are one type of UDE that falls into this category. A Train Information System equipped with a UDE Locator option should be able to detect the source of an emergency application of the train brakes to within one or two car lengths. Upon detecting the emergency application at the rear car, a data message is immediately transmitted to the cab unit reporting that the rear-end is in emergency. The cab unit logs the time of arrival of this message and logs the time of arrival of the emergency brake application at the front of the train using a BPP transducer in the locomotive. The cab unit then calculates the location of the UDE using train length data (previously input by the engineer) and then displays the estimated location of the UDE on a suitable display.

10.

Emulation of Rear Car Control Valve Activity: Another optional feature could provide the locomotive engineer with expanded information about the rear car brake system. By continuous monitoring of changes in brake pipe pressure over time, it is possible to predict the brake cylinder, emergency reservoir and auxiliary reservoir pressures without direct measurement. Once this information has been calculated, it can be presented to the engineer as a quantitative or qualitative indication of: a.

The state of the air charge at the rear of the train.

b.

An emergency or service brake application.

c.

A brake release in progress, or

______________________________________________________________________________ - 30 –

AREMA® C&S Manual

2002 d.

Part 22.3.1

Low rear end train line pressure.

11.

Deleted, See Section C.

12.

Automatic Initial Terminal Air Brake Test: Availability of an onboard microprocessor in the locomotive cab offers the possibility of improving the consistency and accuracy of both the Initial Terminal Air Brake Test and the 1,000 Mile Air Brake Test.

13.

Voice Warnings and Advice: Recent advances in the presentation of information have included methods for verbal announcement of computer generated display and status information. With this method, instead of a visual display, a voice would announce the information on a speaker. With such voice presentations, the locomotive engineer is not required to visually scan a display to read the information. This method would be most beneficial during periods of peak demands for visual scanning outside the cab.

14.

Hot Box, Dragging Equipment and Other Defects Cab Display: Availability of both a data communications link and a microprocessor onboard locomotives offers the potential for integrating existing wayside detector systems into a cab display for the locomotive engineer.

15.

Train Orders Cab Display: Availability of a microprocessor, computer memory, and alphanumeric cab displays in locomotives offers the potential for cab displays of a variety of train operations information and aids useful to the locomotive engineer. For example, train orders, train makeup information and special restrictions information could be prepared on a main frame computer, recorded on a digital mass storage device (e.g., cassette tape, non-volatile memory, CD ROM or diskettes), loaded into the cab unit at the start of a trip, and displayed upon request of the locomotive engineer in the cab at any time during a trip. Such a tape or memory device could even be used to enter the identification number of the Train Information System rear unit and train length for each trip. This would require addition of a memory readout device and a larger alphanumeric display device in the locomotive cab and computer facilities for preparation of the digital storage memories.

16.

Automatic Train Location: This option would use interrogation and response interactions between wayside stations and the train to provide accurate train location data independent of existing block signal systems.

17.

Mid-Train Slack Status and Brake Pipe Pressure Detectors: Another option could provide mid-train slack and brake pipe pressure status in the cab. This would require one or more sensor units, similar to the rear unit operating at any designated mid-train location, in parallel with the rear unit. Each unit would be assigned a unique identification number to enable the cab unit to distinguish data reported from each location. Increased communications processing capability would be required, along with increased alphanumeric display capability and a display selector device.

_____________________________________________________________________________ - 31 –

AREMA® C&S Manual

Part 22.3.1 2002 18. Disable Train Warning Light: In the event a train suddenly becomes disabled, such as from an undesired emergency brake application, operating rules require the crew to protect approaching trains from the possibility of a derailment. This option would add a light to warn approaching trains of this situation. This warning light would be illuminated either automatically when train brakes are applied in emergency or manually by the locomotive engineer using a cab control switch. The light would be reset by a control stand switch. This warning light would not replace the rear end marker device, nor shall the marker device serve this function. 19.

Rear Car Acceleration Indicator: Another train handling related option would provide a cab display of rear car acceleration. This could be accomplished using a longitudinal accelerometer in the rear car, and displayed in the cab in miles per hour per minute.

20.

Front Unit Authorization for Additional Security: This is a recommended option that provides additional security to prevent unauthorized application of the Emergency Braking Feature, by a party or parties external to the control cab of the train. This option is to maximize the safety of the system while not compromising the two -way, front-to-rear code security, described in Section C. By using the following procedure when the rear unit is tested by a employee at the end of the train, the front equipment is authorized to transmit the Emergency command to its associated rear unit only. Description of Arming Sequence: Detailed below is a technical description of the Front Unit Authorization option as used to provide protection against external initiation of the Emergency Braking feature described in Section C. a.

When a front unit is said to be authorized to transmit Emergency on a certain ID code, it means that it is capable of doing so only when the thumb wheel switches match the authorized ID code.

b.

The authorized ID code shall be stored in non-volatile memory in the front unit, ie. it shall be retained indefinitely when unit is unpowered. This is required should power to the device be lost.

c.

The authorized ID code shall not be directly readable by the in operational mode, but shall be capable of being displayed in a test mode for maintenance purposes.

d.

The front unit shall retain the last used authorized ID code until reauthorized on a different code.

e.

Whenever the front unit sends a Status Update Request having an ID code (selected by the thumb wheels) that does not match the

______________________________________________________________________________ - 32 –

AREMA® C&S Manual

2002

Part 22.3.1 authorized code, it shall sound an audible alarm and display the warning NOT ARMD for 1 sec. This alerts the that the Emergency function is not available, while still allowing a two-way Communications Link test, to any rear unit without having to go through the authorizing sequence. f.

To authorize the front unit, the TEST button on the rear unit is pushed. The transmission initiated by this action, shall have the code 111 as Message Type Identifier and the Confirmation bit reset to "0".

g.

When the front unit receives a rear-to-front message matching its dialed ID code, which has Message Type Identifier 111, and which has the Confirmation bit reset to 0, it shall sound an audible alarm and display the message ARM NOW for 5 sec. The above transpires, if and only if, the stored authorized code differs from the ID code of the received rear unit's ID code.

h.

To complete the authorizing sequence, a Communications Link Test shall be initiated while the display shows ARM NOW. This shall initiate a Status Update Request and causes the display to revert to normal.

i.

After the transmission with Message Type Identifier 111 has been sent (per step f.), the rear unit shall respond to the first valid Status Update Request received within 6 sec. from the front unit (per step h.) with a message in which the Confirmation bit is set to 1 and with a Message Type Identifier of 111. On subsequent replies to Status Update Requests, or on any reply occurring 6 sec. after the ARM transmission, the Message Type Identifier shall be set to 000.

j.

When the front unit receives a confirmation of a Status Update Request that has Message Type Identifier 111 and the Confirmation bit set to 1, it shall sound an audible alarm and display ARMED for several seconds. The display shall then revert to normal. At this time, the new authorized code is written into nonvolatile memory in the front unit.

_____________________________________________________________________________ - 33 –

Part 22.3.1

AREMA® C&S Manual

2002

Appendix A Coding of ASCII Characters in Messages A desirable feature of a Train Information System is the ability to send ASCII character strings to a cab unit, which could subsequently display this information directly on a suitable display device. To facilitate the development of this optional feature, the following information, which pertains to Type 0 messages, is provided. When an Optional Data Block format indicator bit is a one (1), the 42 data bits that follow the indicator bit are coded as six seven-bit ASCII characters. The designated coding format for a character is shown in Table A-1 that contains the 128 character conventional ASCII character set. Each ASCII character sent in the block shall be transmitted LSB first. A rear unit device shall transmit a total of six ASCII characters when the ASCII data format is used. If the transmitting system requires only a portion of the six characters available in the Optional Data Block, additional ASCII characters shall be appended as place markers so that all 42 bit positions are filled with data. (That is, all ASCII character strings shall be padded to six characters if less than six are required.) The ASCII null (NUL) or space (SP) characters could be used in many situations to fulfill this requirement.

______________________________________________________________________________ - 34 –

AREMA® C&S Manual

2002

Part 22.3.1

Type 0 message example: An example of a Type 0 message containing an ASCII character string is shown below. The character string in the message is the ten-character string, "SAMPLE ONE". This character string requires two Optional Data Blocks in the message. Two ASCII null characters have been added to the string in order to fill the entire data field in the second Optional Data Block. The data values listed are in binary, with the right most bit being the LSB. Basic Bit sync Block Frame sync Chaining bits Device battery condition Message type identifier Unit address code Rear brake pipe status and pressure Discretionary information Motion detection Marker light battery condition Marker light status Basic block BCH code Trailing bit Optional Data Block 1

Optional Data Block II

Bit sync Frame sync Chaining bits Block format indicator bit ASCII character S ASCII character A ASCII character M ASCII character P ASCII character L ASCII character E Optional block I BCH code Trailing bit

1 1010011 1000001 1001101 1010000 1001100 1000101

Bit sync Frame sync Chaining bits Block format indicator bit ASCII character SP ASCII character O ASCII character N ASCII character E ASCII character NUL ASCII character NUL Optional block II BCH code Trailing bit

1 0100000 1001111 1001110 1000101 0000000 0000000

_____________________________________________________________________________ - 35 –

AREMA® C&S Manual

Part 22.3.1

2002

Table 2231-A1: ASCII Code Chart 87

0 86 85

0

0 0

BITS

0 1

CONTROL

0

0

1 1 0 1 HIGH X & Y

1

1

0 0

1

0 1

LOW X

1

1 0

1 1

LOW Y

GRAPHIC INPUT

84

83

82

81

0

0

0

0

NUL 0

DLE 16

SP 32

O 48

@ 68

P 80

`

96

p 112

0

0

0

1

SOH 1

DC1 17

! 33

1 49

A

65

Q 81

a

97

q 113

0

0

1

0

STX 2

DC2 18

" 34

2 50

B 66

R 82

b

98

r

114

0

0

1

1

EXT 3

DC3 19

# 35

3 51

C 67

S 83

c

99

s

115

0

1

0

0

EOT 4

DC4 20

$ 36

4 52

D 68

T 84

d 100

t 116

0

1

0

1

ENQ 5

NAK 21

% 37

5 53

E 69

U 85

e 101

u 117

0

1

1

0

ACK 6

SYN 22

& 38

6 54

F 70

V

f

v

0

1

1

1

BEL 7

ETB 23

' 39

7 55

G 71

W 87

g 103

w 119

CAN 24

(

40

8 56

H 72

X 88

h 104

x

120

41

9 57

I 73

Y

89

i 105

y

121

86

102

118

BELL

1

0

0

0

BS 8 BACKSPACE

1

0

0

1

HT 9

EM 25

)

1

0

1

0

LF 10

SUB 26

* 42

: 58

J 74

Z 90

j 106

z

122

1

0

1

1

VT 11

ESC 27

+ 43

; 59

K 75

[ 91

k 107

{

123

1

1

0

0

FF 12

FS 28

, 44

< 60

L 76

\ 92

l 108

| 124

CR 13

GS 29

-

45

= 61

M 77

] 93

m 109

}

1

1

0

1

125

RETURN

1

1

1

0

SO 14

RS 30

. 46

> 62

N 78

^ 94

n 110

~ 126

1

1

1

1

SI 15

US 31

/ 47

? 63

O 79

-

o 111

RUBOUT

95

(DEL) 127

______________________________________________________________________________ - 36 –

AREMA® C&S Manual

2002

Part 22.3.1

Appendix B BIT POSITIONING DIAGRAM BASIC MESSAGE BLOCK - ONE WAY SYSTEM MSB UAC

LSB MESSAGE TYPE IDENTIFIER

DEVICE BATTERY CONDITION

CHAINING BITS

UNIT ADDRESS CODE (UAC) UNIT ADDRESS CODE (UAC) DISCRETIONARY

REAR BRAKE PIPE STATUS & PRESSURE DISCRETIONARY INFORMATION

BCH CODE

MARKER STATUS

MARKER COND.

MOTION DETECT.

DISCRETIONARY INFORMATION

BCH CODE TRAIL. BIT

BCH CODE

Note: Bit and Frame Sync Bits are not shown.

_____________________________________________________________________________ - 37 –

AREMA® C&S Manual

Part 22.3.1

2002

Appendix C-1 BIT POSITIONING DIAGRAM MESSAGE BLOCK - TWO WAY SYSTEM REAR - TO - FRONT COMMUNICATIONS MSB

LSB

UAC

MESSAGE TYPE INDENTIFIER

DEVICE BATTERY CONDITION

CHAINING BITS

UNIT ADDRESS CODE (UAC) UNIT ADDRESS CODE (UAC) DISCRETIONARY

REAR BRAKE PIPE STATUS & PRESSURE

VALVE CIRCUIT

DISCRETIONARY INFORMATION

BCH CODE

MARKER STATUS

MARKER COND.

MOTION DETECT.

DISCRETIONARY

CONFIR MATION

BCH CODE TRAIL. BIT

BCH CODE


______________________________________________________________________________ - 38 –

2002

AREMA® C&S Manual

Part 22.3.1

Appendix C-2 BIT POSITIONING DIAGRAM MESSAGE BLOCK - TWO WAY SYSTEM FRONT - TO - REAR COMMUNICATIONS MSB REAR UNIT ADDRESS CODE

LSB MESSAGE TYPE CONDITION

CHAINING BITS

REAR UNIT ADDRESS CODE COMMAND

REAR UNIT ADDRESS CODE

BCH

COMMAND BCH CODE BCH CODE BCH CODE

PARITY BIT

BCH CODE


_____________________________________________________________________________ - 39 –


Arema Communictaions And Signals 4c481d

Overview 5o1f4z

More details 6z3438

Related Documents c2h70

Arema Communictaions And Signals 4c481d

Signals And Systems 1w8q

Signals And Systems [haykin] 2h1060

Signals And Systems Syllabus 2o3921

Bendera Arema.. 615ol

Manual Arema 3r4v40