On the Statistics of Multi-Break Circuit Breakers-Thermal and Dielectric Regimes

This paper studies the statistical performances of multi-break circuit-breakers. For the thermal reignition regime, a formal proof is given of the fact that under certain conditions (explicitly derived) the overall performance of a multi-break breaker is better than that expected from a proportional extrapolation of the results from a single break. For the dielectric regime, it is shown that the hitherto published formulas are conservative in the sense that they overestimate failure probabilities. Using these formulas, graphs are given which compare the failure probabilities of a four-break breaker in the dielectric regime with that of a single break under certain given fractions of the stress on the complete pole. Some general results of a statistical nature relating complete circuit breaker failure probabilities in the dielectric regime to a single break failure probability are also given.