Overcurrent Protection Setings for Zig Zag Grounding Transformers
Overcurrent Protection Setings for Zig Zag Grounding Transformers
(OP)
I have 50/51 overcurrent relay protecting a Zig Zag grounding transformer. What are the recommended settings for the realy?






RE: Overcurrent Protection Setings for Zig Zag Grounding Transformers
RE: Overcurrent Protection Setings for Zig Zag Grounding Transformers
Regards
Marmite
RE: Overcurrent Protection Setings for Zig Zag Grounding Transformers
All that said, my original answer still stands. There is not enough information in the original question to actually recommend settings.
RE: Overcurrent Protection Setings for Zig Zag Grounding Transformers
The supply transformer should be tripped out before the I2T crosses the the zig-zag transformer's damage curve.
An alternative is to insert a series resistor in the ground path to limit the fault current and alarm the fault. This depends a lot on the application, and the protection philosophy of the protection group.
Bill
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"Why not the best?"
Jimmy Carter
RE: Overcurrent Protection Setings for Zig Zag Grounding Transformers
How are the CTs connected?
A good method of protecting a zig-zag transformer is to
connect the overcurrent CTs in delta. The overcurrent
relay will then ignore the zero sequence current which
must flow for an external fault, and can be set low and
fast.
Thanks,
Alan