A new method for observation of breakdown phenomena in XLPE cable insulation

Prebreakdown partial discharges (PPDs) were measured in XLPE (cross-linked polyethylene) cable insulation, and the duration of the time before breakdown and the stress dependence were examined. A special prebreakdown partial discharge detecting method, which detects prebreakdown partial discharges and removes the applied voltage before the breakdown occurs, was developed and permitted the detection of the breakdown origin. The data show that PPDs necessarily appear before the breakdown and that the breakdown origin can be detected by removing that applied voltage within the PPD duration time. It is concluded that this method is very useful for the study of breakdown mechanisms in XLPE cable insulation