Investigation On Breakdown Probability Of Series-Connected Vacuum Gaps

Vacuum breakers have many advantages. But traditional breaker with single vacuum gap has a disadvantage that it is uneconomical when designed to endure high voltage. So the manufacturers consider using series-connected vacuum gaps to make vacuum breakers.The breakdown characteristic of series-connected vacuum gaps is very important for making multi-gaps vacuum breaker. The statistical breakdown characteristics of the series-connected vacuum gaps are investigated in this paper. The investigation includes theory analysis and experiments. The details of investigation are listed below.The breakdown probability of single vacuum gap is analyzed. The breakdown of vacuum gaps is a process decided by the energy of electric field. The statistical characteristic is a Weibull distribution. Based on the breakdown probability of single vacuum gap and theory of conditional probability, the paper gives an expression of the series-connected gaps. The breakdown probability of series-connected gaps is a sum of probability of all possible breakdown modes. The breakdown phenomena of series-connected vacuum gaps are described. There are pre-breakdown and insulation recovery phenomena during the breakdown process. The expression is modified according to these phenomena. We use standard LIV to investigate the breakdown probability of both single and series-connected gaps. The experiments results are listed and analyzed.The theory analysis and experiments result show that the breakdown of series-connected gaps is a very complex process. There are pre-breakdown and insulation recovery phenomena in the process. The breakdown probability of series-connected gaps is a conditional probability based on breakdown probability of single gap. But we have to modified the breakdown probability of single gap because the different breakdown process.