Dielectric Strength and Statistical Property of Single and Triple-Break Vacuum Interrupters in Series

The maximum possible improvement factor of VCB with double or multiple breaks compared with one-break, which have the same equivalent gap length, is deduced. Simultaneously, from the research on the breakdown weak points in high voltage vacuum gaps, their turn out and distribution, a theoretic model was set up for describing the statistical property of multi-breaks VCB´s. This paper describes dielectric experiments on the commercial vacuum interrupter arrangements with single break or triple breaks in series. The experiments were carried out under lightning impulse voltage (LIV). It shows that the more numbers in series are, the higher the breakdown voltage improvement factor is. The statistical results show that the triple-break vacuum interrupters in series have the lower breakdown probability compared with the single-break one. It can be demonstrated in a preliminary study that the experimental results do confirm with the previous theoretical studies