Space charge distribution, TSC and TSL spectra in polyethylene aged by electrical stress

PE samples were aged under an ac stress of 50 kV/mm for 100, 300, 700, 1000 and 1200 hrs respectively. The space charge distribution in the samples was measured by pulsed electro-acoustic (PEA) method. Thermally stimulated current and luminescence spectra were simultaneously detected by a United Spectrum Instrument. The test results show that the space charges in samples were mainly negative charges from dissociated impurities. The space charges in the samples increased with aging time. An increase of hetero-charges promotes the electrodes to emit home-charges and separate charge peaks in the aged samples. Aging increases the densities of traps and luminescence centers (LC), but does not change their energy level in γ relaxation region of PE sample. However, aging not only increases the density of traps in β and α relaxation range or structure defects, but also increases their energy level. Space charges in short circuited aged sample may be an indication of change in densities of trap and luminescence center