抄録
Non-polar polymers are widely used as electrical insulation materials. Their operating conditions sometimes become high electric field and high temperature. Under these conditions the conduction loss is supposed to affect the dielectric properties and to make the ac dissipation factor (tan δ) increase. Therefore the high field dielectric properties of polymeric materials in high temperature region becomes very important.
This paper describes high field dielectric properties of polypropylene films measured at 50Hz and 400Hz above room temperature with the new electrodes developed by authors. At low temperature, the high field tan δ is independent of the frequency of the applied field. However, at high temperature, the high field tan δ becomes almost inversely proportional to the frequency, namely, the conductivity is independent of the frequency. The theoretical analysis shows that the high field dielectric loss is governed by two processes: one is the loss which appear only under AC field and the other is conduction loss which appear also under DC field. The latter loss becomes prominent under high electric field at high temperature.
