Yes, the two circuits share structures for a few spans out of the substation. Four over two construction with a shared neutral. I originally dismissed a circuit to circuit fault due to conductor movement because the presumable unfaulted circuit ground relay tripped. But if a phase to phase...
Thanks for the quick response and link to the SEL paper. Here's more details on the fault. The faulted feeder had some UG cable that went bad, so we believe it was a single line to ground fault. The cable was approximately a half mile from the substation. The feeder relays are Westinghouse...
I work for a PUD in Washington and we had two feeders out of one substation that tripped at the same time. One was faulted, the other wasn't. I'm now reviewing the causes of sympathetic tripping and my notes (from an SEL class I took a couple years ago) state that zero sequence fault current...
