The Direct Breakdown Voltage of Silicone Oil Under Uniform Fields

The breakdown voltage versus gap length characteristics were obtained for degassed silicone oil, oil saturated with oxygen, and oil containing varying concentrations of l-methylnaphthalene as additive. Both aluminum and stainless steel electrodes were used. The breakdown voltage versus gap length characteristics for various additive concentrations in degassed oil all pass through a critical gap length at which the breakdown voltage is independent of the additive concentration. For gaps longer than the critical gap the breakdown voltage decreases with increasing additive concentration, whereas for shorter gaps the effect is reversed. For oil saturated with oxygen no such critical gap is present.