Statistical Property of the Breakdown of Vacuum Circuit Breakers and its Influence on the Surge Generation in Capacitive and Reactive Current Interruption

The statistical property of the breakdown of a contact in vacuum has been studied experimentally. The results are summarized so as to express the cumulative probability of breakdown as a function of the applied voltage and the spacing of the contact. The expression of the probability distribution is applied to analyze the switching surge generation by a vacuum circuit breaker in the load current interruption of capacitive and inductive circuits. It was shown that a completely restriking -free condition is quite difficult to realize particularly at high system voltages. The statistics of the switching surges due to the restrikings and the problems of circuit protection for them are given based on the analysis.