Breakdown Conditioning Characteristics of Long Gap Electrodes in Vacuum

In order to develop high voltage vacuum circuit breakers, it is important to clarify breakdown (BD) mechanism in vacuum, especially for long gap (longer than 10mm gap distance). This paper discusses the conditioning characteristics of a long gap electrode (up to 50mm), under non-uniform electric field in vacuum. Experimental results revealed that the influence of vacuum gap distance between electrodes on the BD voltage, the BD field strength and the BD occurring region. Maximum field strength at BD is nearly constant at 10-50 mm gap distance