Partial Discharge Activity on Polymeric Insulating Surfaces under Positive Trapezoidal High Voltages

Partial discharge activity in a short sphere-plane gap bridged by PVC and POM insulating surfaces has been investigated under positive trapezoidal high voltages; the case of air alone was considered as reference. Distinguished modes of discharge activity., namely streamer and stable glow discharges., are determined., and their associated salient characteristics are measured as affected by the insulating surface. Inception of partial discharges occurs at a lower voltage in the presence of an insulating surface than in air alone., but the opposite applies for discharge extinction. Along an insulating surface the establishment of the stable glow discharge is hindered due to preceding intense streamer discharge activity. The discharge current., therefore also conductance., is higher for air alone and lowest for the PVC insulating surface. Results are discussed in terms of insulating surface material electrical properties and its affinity to surface charging.