Temporal Variation of Conduction Currents in Liquid Insulants under High Direct Voltages

The temporal variations of conduction currents were closely observed for point-to-sphere and sphere-to-sphere gaps, in transformer oil and in n-hexane, subjected to high direct voltages. Current bursts of both long and short durations could be distinguished from the random fluctuation of the quasi-steady current component. Long-duration bursts were similar to some previous observations and could be related to impurity particle activity in the liquid. Many short-duration bursts, however, had the polarity opposite to that of the quasi-steady current component. Explanations are proposed.