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Investigation of dielectric breakdown characteristics of double‐break vacuum interrupter and dielectric breakdown probability distribution in vacuum interrupter

To investigate the reliability of equipment of vacuum insulation, a study was carried out to clarify breakdown probability distributions in a vacuum gap. Further, a double‐break vacuum circuit breaker was investigated for breakdown probability distribution. The test results show that the breakdown probability distribution of the vacuum gap can be represented by a Weibull distribution using a location parameter, which shows the voltage that permits a zero breakdown probability. The location parameter obtained from Weibull plot depends on electrode area. The shape parameter obtained from Weibull plot of vacuum gap was 10 to 14, and was constant irrespective of the nonuniform field factor. The breakdown probability distribution after no‐load switching can be represented by Weibull distribution using a location parameter. The shape parameter after no‐load switching was 6 to 8.5, and was constant irrespective of the gap length. This indicates that the scatter of the breakdown voltage was increased by no‐load switching. If the vacuum circuit breaker uses a double break, the breakdown probability at low voltage becomes lower than the single‐break probability. Although the potential distribution is a concern in the double‐break vacuum circuit breaker, its insulation reliability is better than that of the single‐break vacuum interrupter even if the bias of the vacuum interrupter's sharing voltage is taken into account. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(2): 13–20, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21060