Conduction current pulses in transformer oil

A systematic study of the pre-breakdown conduction current pulses in transformer oil using static electric stresses showed that these pulses are very sensitive to test conditions. The pulses were found to depend on gap length, applied stress, temperature, electrode material and hydrostatic pressure. The distribution of the pulse heights was exponential, indicating the presence of a multiplication process in the liquid. It is suggested that the pulses are due to the ionization of microscopic gas bubbles by electrons emitted at the cathode.