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biswanath.das
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Join Date: Oct 2006
Location: Kolkata, India
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Transformer Differential and REF Protection

04/17/2013 8:06 AM

In one protection One line for 50/63 MVA 230/69 kV YNynD transformer it has been observed that they have used redundant differential protection relay with all separate diff CT's and didn't consider REF for primary and secondary winding. Whether REF is superflorous for such dual redundanrt diff protection scheme.

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Anonymous Poster #1
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Re: Transformer Differential and REF protection

04/17/2013 8:24 AM

Ask "them".
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electricalexpert65
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#2

Re: Transformer Differential and REF protection

04/17/2013 10:32 AM

From the trafo specifications, I understand that it is a inter-connecting auto transformer with a tertiary delta. Am I right?

Generally, almost all of today's numerical relays do have REF protection element inherent in them. Pl. check for the same.

If it is not there, you must provide separate REF Protection.

Even though differential relays could offer REF protection to an extent, if the earth fault is very close to the neutral, then differential may not react. A separate REF would be helpful then.
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biswanath.das
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Location: Kolkata, India
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#3
In reply to #2

Re: Transformer Differential and REF protection

04/18/2013 1:12 AM

You are right its tertiary delta. In case of REF what % winding protection is advised? At that % winding protection will Diff protection will not respond? as an additional protection they have used dual diff protection. 100% winding protection is not recommended since it will trip the upstream breaker with minor fault isn't it?

Thanks

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Anonymous Poster #1
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Re: Transformer Differential and REF protection

04/18/2013 3:19 AM

Did you ask "them"?
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Anonymous Poster #2
#5

Re: Transformer Differential and REF Protection

04/22/2013 5:53 AM

I think you must climb on your tricicle, go to the alians and ask them about your problem..................
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