Some further comments on the fast measurements of partial discharges in polyethylene voids

Voids have a deleterious effect on the performance of solid insulation because of partial discharges taking place at relatively low stresses. The waveshape of partial discharge current is studied for voids of various depths in polyethylene. Some examples of the measurements performed are shown and discussed. The voltages appearing across the voids under investigation are compared with Paschen´s curve. It is suggested that the discharge mechanism in an enclosed void is a streamer mechanism. There is also evidence that part of the void discharges, not the whole of it