Phase behaviour in AC generated partial discharges: electro-convection and the moderation of discharges

Summary form only given, as follows. The temporal (phase) behaviour of partial discharges generated in transformer oil is examined. The system evaluated consists of a point-plane electrode gap energized by an ac potential oscillating at a frequency of 70 Hz; the experimental methods employed provide a complete phase-history of all discharge events. Analysis of these data show that the discharge events are highly correlated at short phase-separations, in that the likelihood of discharges with phase-separation 4/π is greatly diminished and is in marked contrast with the behaviour predicted for random, independent events. We suggest that convective flow plays a predominant role in moderating the initiation of further discharges for a phase-separation of 4/π under the described experimental conditions. The conditions for electro-convection and the characteristics of the fluid flow are discussed