A Case Study of Breaker Failure During Simultaneous Single-Line-to-Ground Faults on a Parallel Circuit

This paper analyzes two breaker failure events of which simultaneous single-phase-to-ground faults on a double circuit line caused re-striking of one line's faulted phase interrupter. The short-line faults occurred twice at nearly identical locations approximately one year apart causing failure each time of a 161kV, 40kA circuit breaker. The fault current of both events was less than ten percent of the maximum interrupting current capability of both circuit breakers. This paper discusses both incidents, the analysis to determine the root cause of failure, and the solution to mitigate reoccurrence.