Calculating fault current on secondaries of Grounding Bank
Calculating fault current on secondaries of Grounding Bank
(OP)
Was wondering if anyone has experience calculating available fault current on the secondaries of a grounding bank utilizing distribution transformers (3-50kVA, 13.86kV/240V, Z=2%) which are wired in a wye/broken delta?
Also any tips on sizing the 13.8kV fuse to protect these transformers or is a fuse even necessary. The secondaries will be wired into a digital relay.
Thanks in advance for any assistance.
Also any tips on sizing the 13.8kV fuse to protect these transformers or is a fuse even necessary. The secondaries will be wired into a digital relay.
Thanks in advance for any assistance.






RE: Calculating fault current on secondaries of Grounding Bank
I believe that if you close the delta the current will be limited by three times the 2% transformer impedance (6%Z). Will someone confirm this? Thanks.
Bill
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"Why not the best?"
Jimmy Carter
RE: Calculating fault current on secondaries of Grounding Bank
RE: Calculating fault current on secondaries of Grounding Bank
RE: Calculating fault current on secondaries of Grounding Bank
I suggest relaying protection to trip substation operation.
RE: Calculating fault current on secondaries of Grounding Bank
RE: Calculating fault current on secondaries of Grounding Bank
Fusing. The last thing you want is for a fuse to open on your grounding device during a fault.
It is quite possible that the circuit may be energized with one or more ground faults. For example a crew fails to remove one or more grounding jumpers after a maintenance outage.
This will energize one or more of the grounding ttransformers with full rated voltage. The inrush may be up to 25 times rated full load current.
I would not fuse at less than 50 times full load rated current.
I would use a disconnect switch or fused cutouts fused as described or with wire jumpers in place of fuse links.
You may monitor the secondary voltages to detect transformer failures.
Bill
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"Why not the best?"
Jimmy Carter
RE: Calculating fault current on secondaries of Grounding Bank
RE: Calculating fault current on secondaries of Grounding Bank
Bill
--------------------
"Why not the best?"
Jimmy Carter