SC Current on Primary
SC Current on Primary
(OP)
If I am given a maximum fault current at a transformers secondary from the utility and the transformers impedance, how do I get the fault current that is seen at the primary side of the transformer (in order to get clearing times with the transformers protective device).
Xmfr: 3 phase, 150Kva, 12.47->120/208, Fault Current: 32,784 Amps, Impedance = 1.9%
Thanks.
Xmfr: 3 phase, 150Kva, 12.47->120/208, Fault Current: 32,784 Amps, Impedance = 1.9%
Thanks.






RE: SC Current on Primary
But for what ever fault current, the primary 3-phase fault current would be 208/12470 times the secondary fault current.
RE: SC Current on Primary
For example, a delta-wye-gnd transformer will have two primary phases contributing to a secondary fault, each at 1/sqrt(3) magnitude w.r.t the line-to-line turns ratio * sec current.