The effect of surface oxide films on the apparent zero-gap breakdown voltage in mineral oil

Abstract

The dependence of the apparent zero-gap intercept, obtained by extrapolation of the direct breakdown voltage versus gap length characteristics, on the presence of strongly insulating oxide films on the electrode surfaces has been studied. The intercepts were obtained from tests carried out using etched aluminium, anodized aluminium and stainless steel electrodes in both degassed and oxygen-saturated mineral oil. The results indicate that although a large intercept is associated with the presence of a highly insulating barrier on one of the electrodes, the presence of such a barrier does not necessarily lead to such an intercept. The results are interpreted by taking into account the space charges present at the electrode surfaces prior to extrapolation to zero gap.