The influences of solid surface on the propagation of creepage discharge in insulating liquids

The influences of solid surface on the propagation of creepage discharge in liquids were investigated under ac divergent electric field. Synchronized phase-resolved partial discharge (PD) detection, wideband current measurement and streamer channel visualization were employed to study the differences of discharge patterns between in open gap and on solid surface and to explore the mechanisms behind from the linkages between consecutive discharges. It is found that Perspex, glass and pressboard would all promote the propagation of discharges, especially negative discharges, and enable more discharges to occur at lower instantaneous voltages. It is experimentally verified that this promotion effect of solid surface on discharges is caused by the memory effect of solid surface for space charges and residual low density channels.