E-Beam Energy and Thermal Aging Effect on the Behavior of Leackage Current in Irradiated XLPE HV Insulation

Scanning Electronic Microscopy (SEM) has been used in this investigated work to study the conduction process in XLPE insulation under thermal aging and different e-beam energies. The aged process is done under fixed high temperature equal to 140°C for 1500 h. The aged and fresh samples are subjected to the three levels of electron beam irradiation ranged from 5 keV to 30 keV. Our findings show that aging under high temperatures has a considerable effect on the conduction process of XLPE insulation. It is found that at the end of first 1000 h, the leakage current decreases and after all the aging time (1500 hours) the studied characteristic increases. The same behavior was observed when we have studied the effect of energy of applied irradiation. The falling of leakage current after 1000 hours of high temperature applying might be assigned to crystallinity increase. However, at the end of aging time (1500 hours), we have seen a rapid augmentation of leakage current caused by the augmentation of the conductivity of XLPE. In the other hand, the creation of outside imperfections caused by the aging process can contribute also in this increase.