Transformer Grounded Wye - Grounded Wye with Delta Tertiary
Transformer Grounded Wye - Grounded Wye with Delta Tertiary
(OP)
I have a Grounded Wye - Grounded Wye txfmr with delta tertiary (tertiary used for station service). My question is - Do I need a ground relay on the High side? For a Low side ground fault, will my High side see Zero seq current? If it will, would it be the same as what the low side sees?
What is the source for the gnd current? the tertiary? Please explain, and give any other related points that you have think are useful.
Thanks
What is the source for the gnd current? the tertiary? Please explain, and give any other related points that you have think are useful.
Thanks






RE: Transformer Grounded Wye - Grounded Wye with Delta Tertiary
For a ground fault on the high side primary,the WYE-WYE trafo is equivalent to a DELTA-WYE trafo with no zero seq current contribution to the ground fault.That means only the overcurrent relays will respond.But for a ground fault on the low side secondary the zero seq currents will (a)pass to the primary (b)circulate in buried tertiary DELTA.Therefore,a calculation is necessary to estimate line currents in all three windings knowing Zps,Zpt & Zst values of the trafo.
RE: Transformer Grounded Wye - Grounded Wye with Delta Tertiary
RE: Transformer Grounded Wye - Grounded Wye with Delta Tertiary
Bill
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"Why not the best?"
Jimmy Carter
RE: Transformer Grounded Wye - Grounded Wye with Delta Tertiary
For a fault on the high-voltage system, you will also see some neutral/zero sequence current on the high side.
Find a text on sequence networks for three-winding transformers and start sketching it out.
Cheers.
RE: Transformer Grounded Wye - Grounded Wye with Delta Tertiary
Bill
--------------------
"Why not the best?"
Jimmy Carter