An Investigation of Ac Electrical Aging Phenomena in Polyethylene by Thermally Stimulated Discharge Current Measurement

In previous work, the authors have shown that electrical aging of polyethylene under ac voltage was due to the build-up of a space charge which was accompanied by light emission. Study of the electroluminescence allowed us to estimate the quantity of charges trapped in the material when ac voltage was applied to the polymer. The present paper reports an investigation on space charge in polyethylene stressed by an ac electric field by the thermally stimulated discharge current (TSDC) technique. Measurements were made on the same samples, i.e., the same polyethylene and the same point-plane electrode set-up as for the light emission study. This gives us a direct comparison of the results obtained using both techniques. It is shown that both the quantity of oxygen dissolved in the material and the amplitude, type and duration of electrical polarization have an influence on the observed peaks. We suggest that the applied electric field modifies the structure of the polymer.