High-field dielectric properties of polymeric films just after AC field application

The authors have developed a new detection method of AC dissipation current and its waveform of dielectric materials around power frequency. Applying this method, they establish a new instantaneous measurement technique of high-field dielectric properties of insulating materials. The fast rising AC ramp voltage and the AC constant voltage with abrupt frequency changes are applied to the nonpolar polymeric film samples. The DC pre-stress is also applied to evaluate its effect for the AC electric field dependence and time variation of tanδ. Using the FFT data analysis of AC loss current, the variation of tanδ of PP film is measured within each one cycle of continuously applied field. AC loss mechanism is then discussed from this result