Dielectric breakdown probabilities for uniform field gap in vacuum

To investigate the reliability of the insulation of equipment having vacuum incorporated as an insulation medium, a study was carried out to clarify breakdown probability distributions in the vacuum gap. Experiments were carried out to investigate the effects of test methods, electrode area, and electrode materials on the breakdown probability distributions of uniform-field gaps. 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. When aiming for highly reliable vacuum insulation equipment, an important factor is insulation design with the location parameter just mentioned taken into account. The location parameter depends on electrode area. This is probably because the existence probability of factors as weakpoints for breakdowns such as micro-protrusions and micro-particles depends on the electrode area