Circulating Currents / Gen / DeltaWye

[jimgineer]

The setup that is currently existing involves a pair of 480V generators that feed transformers that step the voltage up to 13.8kV , and in turn feed a piece of switchgear at this voltage. Utility feeds into switchgear, and switchgear feeds a couple buildings, presumably being dropped down to 480 or other distribution level voltage closer to the loads.

The question I have been asked and didn’t have a good answer to involves explaining the tradeoffs in selecting a delta or wye winding on the generator sides of those transformers. It seems like on the switchgear side, delta will be fine, and as I understand it slightly cheaper for both the transformer and the fewer conductors that are pulled (a N/G instead of a separate N and then G). But on the generator side, what goes into the selection of whether the generator needs to supply a neutral to this transformer?

I realize this is a subject that is very deep but I need to develop a much better pros/cons kind of engineering tradeoff understanding of this decision.

Thanks in advance to you smart ones-

 

[slavag]

Hi jimgineer .
Please don't mix 87G generator differential protection against phase to phase faults and 87N restricted earth/ground fault protection or 87U block transformer-generator differntial protection.
For the your OP David wrote full and correct answer.
Delta on the generator side.
star (wye) on the 13.8kV side.
Best Regards.
Slava

 

[jimgineer]

OK so 87 relay operation is unrelated to my original question.

Thanks,

 

[slavag]

Hey Jimgineer.
You don't understood me right, sorry for my not clear post.
Of course, we can continue with protection issue.

87 relay operation isn't related to your OP, but 87N, yes relayted. If you will use NER ( high impedance or low-impedance), it's very recommended use 87N ( REF) protection.
Best Regards.
Slava