D!NNy
Senior Member
- Location
- San Luis Obispo
Hello, I am copying this data from SKM website: someone please help me to understand why there is curve shift for only a single phase to ground fault of Delta Wye Grounded configuration which is 0.58% where as line line fault current is 0.5pu on the primary side. I understand the explanation provided below that primary relay is seeing fault current of 1.0pu on at least one of the phases which a relay can trip the circuit breaker (assuming that there is no single phase tripping) except in the case of single phase to ground fault shown My question if there is a line line (Phase A and C as shown in the table) fault on secondary side of a 12kV to 480V 3X100kVA pole mounted transformer Delta Y grounded configuration, protected by the fuses on the primary side (individually operated). in this case fuses on the phase A and C has to be sized for 0.5pu transformer curve shift and phase C as 0.58pu. OR curve shift to applied 0.5pu for all phases and coordinate the fuses properly. Am i doing correct?? Thanks for the suggestions Have a great day. |