Impulse Breakdown Characteristics of Double Vacuum Gaps in Series with Asymmetric Distribution

The objective of this paper is to determine the effect of asymmetric distribution on the impulse breakdown characteristics of double vacuum gaps in series. Vacuum interrupters with sphere-plane electrodes were selected in our experiments. The material of the electrodes was Cu. The diameter of sphere electrode was 18 mm and the diameter of plane electrode was 50 mm. The gap distance of the sphere-plane electrodes could be adjusted. A negative standard lightning impulse voltage was applied with the up-down method, by which 50% breakdown voltage U
₅₀
was obtained.The experiment results showed that the 50% breakdown voltage U
₅₀
of double vacuum gaps is slightly lower than that of single vacuum gap when the total gap distance is less than 2 mm. The asymmetric distribution of two gaps has influence on the 50% breakdown voltage U
₅₀
of double vacuum gaps, the U
₅₀
of double vacuum gaps increases with the upper gap distance under a certain total gap distance. Compared with the lower gap distance, the upper gap distance has a greater effect on the 50% breakdown voltage U
₅₀
of double vacuum gaps.