Partial breakdown (PB) has been reported in breakdown of vacuum gaps in series but has not been fully understood. The objective of this article is to investigate the influence of PB on breakdown of vacuum gaps in series under lightening impulse voltages. Two commercial vacuum interrupters (VIs) of the same model were connected in series with various gap distance arrangements. Experimental results show that four breakdown types could be classified, i.e., repeatedly PB without final full breakdown of the series gaps (type I), two PBs before final full breakdown (type II), one PB before final full breakdown (type III), and no PB before final full breakdown (type IV). Breakdown voltage of the vacuum gaps in series decreases with the increasing difference between the two gaps and could be even lower than breakdown voltage of the larger gap alone. This is explained by analyzing the three stages of transients induced by a PB. A model was established to simulate transients induced by PB of the vacuum gaps in series. The simulated results could match the experimental results well. An evolution process from a PB to the four breakdown types was deduced. The influence of PB on insulation coordination and breakdown voltage of the vacuum gaps in series was analyzed according to the abovementioned analysis.

中文翻译：

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串联真空间隙的闪电脉冲击穿——第一部分：部分击穿

部分击穿 (PB) 已报道在串联真空间隙的击穿中，但尚未完全了解。本文的目的是研究 PB 在雷电冲击电压下对串联真空间隙击穿的影响。两个相同型号的商用真空灭弧室 (VI) 以不同的间隙距离排列串联。实验结果表明，可以划分四种击穿类型，即重复 PB 未最终完全击穿串联间隙（类型 I）、最终完全击穿前的 2 个 PB（类型 II）、最终完全击穿前的 1 个 PB（类型 III）、并且在最终完全击穿之前没有 PB（IV 型）。串联真空间隙的击穿电压随着两个间隙之间的差异的增加而降低，甚至可能低于单独较大间隙的击穿电压。这可以通过分析由 PB 引起的三个阶段的瞬态来解释。建立了一个模型来模拟由串联真空间隙的 PB 引起的瞬态。模拟结果可以很好地匹配实验结果。推导了从PB到四种击穿类型的演变过程。根据上述分析，分析了PB对串联真空间隙绝缘配合和击穿电压的影响。