What Is The Function Of A Station Transformer And Auxiliary Transformer In Thermal Power Stations_ - Quora.pdf 4j496n

2/26/2017

What is the function of a station transformer and auxiliary transformer in thermal power stations? ­ Quora Ask Question

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What is the function of a station transformer and auxiliary transformer in thermal power stations? Request

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Answer What is the use of the station transformer in the NTPC?

4 Answers Apoorva Sohani, works at National Thermal Power Corporation Written Jun 15, 2015

I work in NTPC so I feel obliged to answer this question. I will answer this question

What is the role of station transformer in power system? How power is transformed? What are some interestingly designed transformer stations?

assuming that you have some basic knowledge about how a thermal power plant works. Power crises in India is of utmost importance for us to solve. In such situation we cannot afford a plant shut down due to failure of any device. Hence arrangements are made such that each and every device/facility has a back up. Station and auxiliary transformers are also a part of such arrangement. For your clear understanding I will provide a simple Single line diagram (SLD).

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Question Stats 5 Followers 20,947 Views Last Asked Sep 22 Edits

So as you can see from the diagram that every unit has a generator which is connected to the grid through 23.5KV/400 KV generator transformer (GT). The generator also supplies power to the unit transformers which are 23.5KV /11KV. These are used to supply power to 11 KV drives.  Meanwhile the grid is connected to the same droves through the station transformer which is 400KV /11KV transformer. The fig clearly shows the interconnection between the unit and station transformer buses. This arrangement is done so that if one of the unit transformer is under maintenance then the other should take up all the load. If in case the generation had itself stopped due to in adequate steam parameters, or some essential drive failure etc the other drives may be kept under service by taking the power from the grid and keeping the plant alive until the main problem is sorted out.  The main reason behind this is if due to some interruption in the power generation for a short while, if whole of the plant is Upvote 71 Downvote Comments 2+

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2/26/2017

What is the function of a station transformer and auxiliary transformer in thermal power stations? ­ Quora

allowed to shut down and cool down then, it takes a lot of money, time and manhours Ask Question Ask or Search Quora to start the full capacity generation again. Such huge is the system, we can't afford

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losing it. Some of the 11KV drives are Motor driven Boiler feed pump,  Induced draft fan,  Primary air fan, forced draft fan,  Cooling water pump etc. These are all vital and take most of the portion of auxiliary power consumption. To give you an example, Consider you put up a shop and keep a boy as the keeper there for full time. You due to some reasons cannot run the shop by yourself and this is your only source of income. So to sustain your income you pay a small portion as a salary to that boy.  Similarly is the working of a plant. To sustain the generation, the generator gives a small portion to its auxiliaries which help it in running.    So here enters the unit auxiliary transformer which steps down from 11KV to 3.3KV and supplies to most of the auxiliaries like condensate extraction pump, Mills, Auxiliary cooling water pump,  Instrument air compressor, demineralised cooling water pump etc. Further the unit transformers branch into unit service transformers  (not shown in the diagram) which step down 11KV to 415V abs station transformer branches into station service transformers again stepping down to 415V. The same interconnection between these 415V buses as you can see in the 11KV buses are done and this will provide a firm supply to all the LT(low tension ) switchgears. 19.4k Views · View Upvotes

Laxman Gupta, Retired ED from NTPC Written Mar 27, 2016

Station Transformer supply power to main plant ie all drive  motors to Steam Turbine and Steam Generator of a Power Plant while auxiliary Transformer supply power to other utilities like Circulating water ,Air conditioning, coal handling plant etc 3.9k Views · View Upvotes Upvote

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Shaurya Sheth, Electrical Engineer Written Jun 5, 2015

Station transformers are that transformers in which input is from the generator and output goes to the bus bar. And auxillary transformers are those which are used for the auxillary machines which are used inside the plant to run the plant. So it's input is from the bus bar to all the auxillary machines inside the plant.. 5.7k Views · View Upvotes Upvote

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John Marsh, studied at Electronics and Communication Engineering Written Jan 22, 2016

Generator Transformer: This is the main power transformer employed in the power plant. It steps the voltage from 21kV to 230 or 400kV and delivers the power. Stepping up the voltage reduces the transmission losses which occur during the power transmission to long distances. The rating of this transformer (MVA rating) will be almost equal to the alternator or generator rating. Unit Auxiliary Transformers: These transformers are connected to the Generator Transformer bus. These transformers steps down the voltage from 230kV or 400kV to 6.6kV (230/6.6kV or 400kV/6.6kV) and supply the power to the electrical auxiliaries present in the plant (motors, drives, lighting and other plant loads). 3.7k Views Upvote

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