高温領域におけるポリエチレンフィルムの高電界誘電特性

抄録

Nonpolar polymers such as polyethylene or polypropylene are widely used as insulation materials. Their operating conditions often involve high electric field and high temperature. Under these conditions the conduction loss due to DC like carrier transport may contribute high field AC dissipation factor (tanδ).
This paper describes high field dielectric properties of polyethylene films measured from 50Hz to 400Hz above room temperature to 100°Cwith the new-type electrodes developed by authors. In the high temperature region, AC dissipation current waveform at 50Hz was also measured. Around room temperature, electric field dependence of tanδ is independent of the frequency of the applied field. However, at high temperatures, the high field tanδ tends to have large field dependence and to be almost inversely proportional to the frequency. Namely, the AC conductivity becomes independent of the frequency of the applied field in high field and high temperature regions. The theoretical analysis shows that the high field dielectric loss is governed by two processes. One is the dielectric relaxation loss inherent to AC field. Another is the DC like carrier transport loss which comes to prominent in the high temperature region, where AC dissipation current waveform deforms from the sinusoidal one.