Polarization and charge trapping in cross-linked polyethylene(XLPE) cables AC aged in humid environment

摘要

The authors report the results of TSDC (thermally stimulateddischarge current) and TTC measurements of XLPE (cross-linkedpolyethylene) cables AC aged in water for a period up to 4000 h.Absorption and resorption current measurements were also performedduring the aging to get more information about the penetration of waterand ions into the cable. The results suggest that initially the polarmoieties of cross-linked by-products together with the antioxidant playa dominant role in the internal polarization of the polymer. Thediffusion of ions with water under the AC stress also is enhanced withtime. The dipole density gradually reduces with aging time due todiffusion. With increasing AC aging there is also the enhancement of thedensity of the localized energy states and the oxidation level, which inturn increases the injection efficiency of charge carriers which aresubsequently trapped. The observed TSDC spectra of the AC aged and DCpoled samples may thus have a complex origin