Study of high-field AC conduction mechanism of electron beam irradiated crosslinked polyethylene film

In order to investigate the influence of crosslinking on high field dielectric properties of crosslinked polyethylene, the observations of high-field AC dissipation current waveforms of electron beam (EB) irradiated crosslinked polyethylene (IR-XLPE) films at 90°C were carried out by using the different gel fraction samples. These different gel fraction samples were obtained from a different layer of laminated films of 40 layers from the electron beam irradiation side. From the measurements of capacitance for each IR-XLPE sample, we found that the variations of capacitance with temperature depends on the gel fraction. If the gel fraction is high, then capacitance varies little with temperature and vice versa. From the results of high-field AC dissipation current waveforms under AC ramp voltage application, we have estimated the electric field dependence of tan δ for each gel fraction sample. The results show that the dielectric properties at 90°C depend on the position of film from the electron beam irradiation side. It seems to indicate the mobile carrier in high temperature region are strongly affected not only by the electric field and/or temperature but also by the gel fraction of polyethylene films