Zero Sequence Current Source
Zero Sequence Current Source
(OP)
I am currently designing an inverter based distributed energy resource facility in which, upon review, the utility is requiring an additional zero sequence current for effective grounding on the high-voltage side of my transformer. I have a 1500kVA oil-filled padmount step-up transformer (G-WYE:Delta) to interconnect with the customer-owned medium voltage system. The examples the utility has provided all use G-WYE:G-WYE transformers. Does the G-WYE:Delta transformer need the additional zero sequence source on the MV side? I thought this configuration of transformer provided that source on the high voltage side of the transformer.






RE: Zero Sequence Current Source
RE: Zero Sequence Current Source
RE: Zero Sequence Current Source
So it sounds like they are asking you to either purchase the transformer with a delta winding, or purchase a zig-zag transformer. An alternite would be to purchase a transformer with a phantom delta.
You can do one of these, or if you just want to poke them in the eye, propose a grounded wye capacitor bank, which also provides zero sequence, but not the way they want it.
RE: Zero Sequence Current Source
Why doesn't a grounded-wye - grounded-wye not usually supply zero sequence? Are they usually grounded through some impedance?
RE: Zero Sequence Current Source
RE: Zero Sequence Current Source
RE: Zero Sequence Current Source
RE: Zero Sequence Current Source
prc, your question seems a little confusing. What voltage is what? A delta winding is also not a zero sequence source, but on a delta/grounded-wye transformer, it does provide a zero sequence source to the wye side.
A system with no ground reference can be a good and bad thing. In a hospital, a ground fault will not require the system be removed from service. In a distribution system, you can't tell where the fault is, until there is either a fire in the dead pine needles, or a second phase goes to ground resulting in a phase to phase fault.