Variations of high-field dissipation current waveform under AC ramp voltage application

To study the high-field AC conduction mechanisms of nonpolar polymers, the AC dissipation current waveforms are observed. The shapes of the AC dissipation current waveforms in the high-held and high-temperature region become the triangle shape in spite of the sinusoidal voltage application, suggesting the nonlinear electric field dependence of instantaneous AC conductivity. The fast rising AC ramp voltage application method is developed as the new technique to examine the dielectric properties in the very short time range. This method enables the measurement of the variations of the high-field dielectric properties and the dissipation current waveform immediately after the voltage application. The new measurements were carried out on electron beam (EB) irradiated crosslinked polyethylene (IR-XLPE) film. The dissipation current waveforms in the high temperature region show the peak in the former part of each half cycle and quickly decrease in the latter part of each half cycle of a full waveform, which seems to show that the carrier injection from the electrode is assisted by the heterospace charge in the region near the electrode