Partial discharge patterns of electrical treeing in polyethylene

The partial discharge pattern of electrical treeing in polyethylene was investigated by using a computer aided partial discharge measurement system. It was found that partial discharge from an electrical tree is characterized by the so-called wing-like pattern. By using the wing-like patterns, treeing degradation was successfully diagnosed. It is likely that each PD from a tree occurs in a different channel and the number of discharges in each half cycle in one channel is one or less. Negative discharges occur more easily than positive ones