Step-up transformer connection wye-star versus star-star
Step-up transformer connection wye-star versus star-star
(OP)
I have a fleet of diesel generators, generating at 400V. I use these in different applications through step-up transformers. So I need flexibility to parallel with other systems at 11kV, 22kV etc. My current fleet of step-up transformers are star-star connected. The original transformer supplier mentioned something about 'no problems with 'phase displacement' if you go star-star. Now I have a client that wants the LV (400V) winding to be connected in delta and the MV connection in star (11kV), due to 'potential 3rd harmonics' if the LV is in star. IS star-star or delta-star the best for paralleled step-up transformers?





RE: Step-up transformer connection wye-star versus star-star
Do you have to serve any loads requiring an LV neutral? You can provide much better protection on an LV delta system with a high resistance earth connection, but only if you don't need the neutral. You can also avoid any circulating current problems, especially if the machines are not closely matched, if you can live without the machine neutrals being connected to each other although you will still need to provide a single neutral-earth connection somewhere on the LV bus.
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RE: Step-up transformer connection wye-star versus star-star
Our little utility ran for years with delta connected generators in parallel with wye connected generators, feeding a delta:wye transformer bank.
Bill
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"Why not the best?"
Jimmy Carter