Enhancement of breakdown strength by microdischarge under impulse voltage applications in vacuum

An investigation of charge behavior such as microdischarge under high electric field in vacuum is very important in order to enhance the electrical insulation performance of vacuum circuit breakers and vacuum interrupters (VCB/VI). This paper discusses the enhancement characteristics of breakdown strength by microdischarge under applying impulse voltage repeatedly and changing vacuum pressure. As a result, microdischarge which had pulsed current waveform became smaller with repeated constant peak voltage applications under 10^-6 Pa vacuum. In addition, microdischarge generation had the electrode conditioning effect to raise the breakdown voltage by reducing adsorption gas of the electrodes. Microdischarge having very small charge compared with that of breakdown has a possibility of drastic enhancement of breakdown strength in vacuum, as the non-breakdown conditioning technique.