Report on continuing work on parallel and nonparallel electric field chemical aging of polymer cavities

Fast pulse measurements were made in a system consisting of parallel electrodes with a cylindrical cavity embedded in polyethylene between them. Extremely fast discharge events can be detected in such cavities. The partial discharges recorded were of the streamer type. Variations in inception stress, albeit small ones, were found. The results also show that the smaller the cavity, the smaller the risetime and the smaller the discharge magnitude. These results suggest that notions such as `discharge free insulation´, and `inception stress´ should be used with caution, as they are very much dependent on the sensitivity of the detection apparatus used