Comparative study of PD characteristics and degradation of PET insulation with a self-contained void, void with closed channel and void with vented channel

Polymeric insulating materials with excellent electrical properties are widely used in electrical power equipment. These materials are degraded however when they are subjected to Partial Discharge (PD). Factors which control the PD activity include pressure and type of gas present. When PD occurs in insulation pressure is created and gaseous products changed due to the energy input. A series of experiments is carried out on artificial voids, created from layered sections of polymer. One set of samples has a self contained air void inside the polymer; a second set of samples has a void connected to a channel with closed end; the final set of samples is created with a channel connecting the void to the outer atmosphere. The samples were electrically stressed at 10% above their PD inception voltages (PDIV) under near identical experimental conditions for the same length of time. This paper summarizes a comparative study of the measurements made on PD activity and the chemical and morphological changes occurring on the void surfaces for each arrangement.