On the relation between current pulses and discharges

Results of a study of the current fluctuations which occur when a point-plane electrode system is highly stressed by a DC voltage are presented. The current pulses can be used as a trigger to initiate the capture of shadowgraph pictures. Polarity effects and the magnitude of the charge associated with the current pulses are both considered. It is found that shadowgraph pictures can invariably be produced when the pulse is sufficiently large to trigger the system, suggesting that the current pulses are associated with the propagation of partial discharges in the liquid. The form of the shadow pictures recorded for DC voltage when compared with those produced by short-pulsed voltage suggests that the former are influenced by local space charge. The effect of the point radius on the discharge initiation and propagation and on the shape of the recorded current pulse is discussed.