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pvkrishnaji
Member

Join Date: Jan 2011
Location: bangalore,india
Posts: 5

Transformer OLTC

04/29/2011 5:46 AM

Dear All

In our plant one transformer(UAT) is having 2 OLTCs(for U phase -1OLTC & V,W -1 OLTC). TRF capacity is 25MVA,20KV/6.9KV

My question is , Is not cause any problem while maintenance?

( If suppose fault occred one OLTC what is the situation? --then It may leads to over loading of other trfs ,trip of breakers & trip of turbine etc., )

what should be the protections(any special relays),steps to take care of that abnormal situations?

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pravinba
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Join Date: Apr 2011
Location: Abu Dhabi, UAE
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Good Answers: 2
#1

Re: Transformer OLTC

04/29/2011 12:16 PM

I have worked with transformers having tap changers on primary as well as secondary side ( submersible HT motor application ). But I never heard transformers having tap changer for "U" phase separately & 'V,W" separately. What is the connected load in this transformer? Can you give more info..

Differential protection is one of the solution to protect the transformer against internal fault..
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rhkramer
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Join Date: Oct 2010
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#2

Re: Transformer OLTC

04/29/2011 2:02 PM

What do you mean by OLTC? Is it some kind of Tap Changer (Maybe OnLine Tap Changer)? Is it some kind of Thermocouple (OverLoad ThermoCouple)--is it something else?
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RAMConsult
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#3

Re: Transformer OLTC

04/29/2011 3:02 PM

Assuming you are referring to some sort of LTC (Load Tap Changer) then the answer to your question is RTFM (Read the Fine Manual) that comes with your equipment. Failure to heed the maintenance safety requirements will result in death, especially if a fault occurs somewhere near the terminals. A fault anywhere inside the transformer and/or LTC will render your equipment non-operationa as well. There are plenty of books on how to properly protect a transformer with relays. And a piece of friendly advice, if you were seriously considering the idea of live maintenance on that equipment, let someone else design the protective relaying.

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pvkrishnaji
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Join Date: Jan 2011
Location: bangalore,india
Posts: 5
#4

Re: Transformer OLTC

04/30/2011 12:11 AM

Dear rhkramer,

OLTC is a On Load Tap Changer. ( It is for getting variable voltage by taking tapping on HV winding)

The manufacturer said that its not possible to make a OLTC of rating 700A. ( Of course its possible).

My question is , Is it Recommendable? if not what precautions we have to take?

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dreamchaser
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Join Date: Aug 2010
Posts: 16
#6
In reply to #4

Re: Transformer OLTC

05/02/2011 2:16 AM

Interesting to hear a transformer with 2 OLTC.How the OLTC are Synchronized for each tap up and tap down operation

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Tornado
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#5

Re: Transformer OLTC

04/30/2011 12:35 AM

That's the problem with unexplained acronyms; I would have guessed "OverLoad Trip Current."

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xformdesign
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Join Date: Feb 2011
Location: Chennai
Posts: 19
#7

Re: Transformer OLTC

06/05/2011 1:17 PM

I think the side where the OLTC connected is DELTA side??????

Yes for 700 A the oltc is possible, but in case of DELTA it is nt available, thats y the oltc is installed in two phases, one at one phase, and another one at the point common to two phases.....

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dreamchaser
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Join Date: Aug 2010
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#8
In reply to #7

Re: Transformer OLTC

08/25/2012 9:18 AM

why it has to be only for delta transformers?

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Tornado
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#9
In reply to #8

Re: Transformer OLTC

08/25/2012 2:12 PM

In star (Y) transformers, there is a single point common to all three phases.

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dreamchaser (2); pravinba (1); pvkrishnaji (1); RAMConsult (1); rhkramer (1); Tornado (2); xformdesign (1)

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