Effect of Dissolved Gases, Stress, and Gap Spacing on High-Field Conductivity in Liquid Insulants

The effect of dissolved gases in mineral oil on conduction currents and conduction current pulses at high fields has been investigated. For a given stress, larger gaps resulted in increased conduction currents as well as current pulses. Oxygen, nitrogen, and air dissolved at small equilibrium pressures (1 torr) resulted in a reduction in the number of current pulses of various magnitudes. However, increasing the oxygen content to 20 torr gave more pulse activity. The results are discussed by considering a model which invokes both cathode and anode space charges.