Considerations of conduction mechanism of LDPE under AC high field

Polyethylene is widely used as an insulating material, for power cables under AC high field. Dissipation current waveform observation method, which has been developed by authors, is very powerful technique to detect high field nonlinear dielectric property and by using this method, not only the various kinds of numerical processing but also the observation under the various kinds of applied voltage waveform by using arbitrary function generator are possible. In order to clarify the conduction mechanism of polyethylene under AC high field and to know which factor influences on the AC conduction, various kinds of experiments, such as the effect of acetophenone or alpha-methylstyrene soaking, the frequency dependence of dissipation current waveforms, the effect of an instantaneous changing rate of applied electric field (dE/dt) by using a high field trapezoid-like arbitrary waveform and so on, were carried out by using several thickness of LDPE film and sheet samples. Some results were analyzed by using FFT analyzing program and it was estimated the fundamental component of the dissipation current waveform. As the results of these experiments, it will be discussed the high field AC conduction mechanism with the effect of dE/dt and the applied frequency