GSU transformer connection 1

Viceng · Jul 16, 2007

Hello,
I was wondering if someone could suggest pro's and con's to the following configuration I have seen at a hydroelectric generating facility:

Generator: High resistance grounded

GSU trasformer: ungrounded wye (4.2kV)/ delta (69kV).

There is one station service transformer on the 4.2kV system (delta-grounded wye 4.2kv-600V). Apart from this the rest of the 4.2kV system is only instrument transformers and some surge arrestor and capacitors.

Thanks!

dpc · Jul 16, 2007

Something in particular you are concerned about?

Viceng · Jul 16, 2007

Well to be quite honest: My inexperience in the matter and the fact that I rarely see this connection.

I am guessing that that one would go for this connection over a delta-delta MPT as the delta-wye is more readily available?

Cheers.

dpc · Jul 16, 2007

Probably started with a requirement that the 69 kV connection be delta, for whatever reason. The generator should be grounded via high resistance grounding, normally at the generator. This rules out a grounded wye connection on the low side of the GSU. So the generator grounding is OK for protecting the generator, the aux transformer delta-wye works out OK. The ungrounded wye is a bit non-typical - perhaps it had already been ordered before it was determined that it shouldn't be grounded.

Viceng · Jul 16, 2007

Thanks dpc.

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GSU transformer connection 1

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