Dielectric recovery strength after vacuum arc extinctions

Abstract

Anode surface temperature after interrupting a vacuum arc has a significant impact on the interruption capacity of a vacuum circuit breaker (VCB) because it dominates metal vapor evaporation. The objective of this paper is to theoretically investigate the relationship between breakdown voltages and anode surface temperatures after current zero. A heat transfer model was established to describe the temperature development on an anode surface, taking account of phase transition processes. The contact material was copper. Moreover, PIC-MCC was adopted to simulate the breakdown voltages in a range of metal vapor density. The calculated results verified the two decay modes of anode surface temperature after current zero proposed by our experiments. The metal vapor density evaporated from an anode surface was positive correlated with its temperature. The breakdown voltage was negative correlated with the anode temperature. A higher surface temperature results in a higher probability of breakdown. Thus, it is better to keep the initial surface temperature at current zero below a certain value.