Pulse-shape characteristics of partial discharge within electrical trees in polymeric materials

Polymeric insulating materials, subjected to high electrical stresses, are susceptible to degradation due to electrical trees, which grow from stress enhancements at contaminants or protrusions. Partial discharges (PD) cause the trees to grow and ultimately lead to failure of the insulation system. This paper describes the latest results of continuing investigation into how the PD pulse characteristics vary with tree growth. For a bush-type tree, the pulse rise- and fall-times, width and amplitude increase with tree growth. The pulse-repetition rate, after the first three hours of aging, remains constant up to failure