Some Factors Affecting the Direct Breakdown Voltage of Silicone Oil under Nonuniform Fields

The effect of electrode polarity, material, and gap length on the direct breakdown voltage of degassed and oxygen-saturated silicone oil was determined using a point-sphere electrode configuration. The results are compared with those obtained for liquid paraffin under similar test conditions. The shape of the breakdown voltage versus gap length characteristics for both polarities of the point shows a marked dependence on the material of the sphere electrode, as well as on the presence or absence of oxygen. The results indicate a striking difference in the polarity dependence between oxygen-saturated silicone oil and oxygen-saturated liquid paraffin.