Flashovers Across Porcelain-Clad Circuit Breakers Due to Atmospheric Contamination

Atmospheric contamination flashovers can occur across porcelain-clad circuit breakers either during normal opening operations or while in the open position. Such external flashovers across a breaker pole can result either in damaging the breaker or reestablishing the previous fault or establishing a new fault in which the breaker is helpless to clear. Three cited cases, each occurring on different types of circuit breakers with different voltage ratings, are presented for the first time. Some of the fundamental principles that lead to atmospheric contamination flashovers on porcelain insulator surfaces also are presented. The purpose of the paper is to alert the power industry to the possibility of such flashovers, to present an analysis of the problem, and to suggest practices and corrective measures to minimize such occurrences.