Analysis on thermal aging behaviors of XLPE cable insulation based on trap parameters and relaxation process

In this paper, the influence of accelerated thermal aging on the trap parameters of XLPE cable insulation was investigated by thermally stimulated depolarization current (TSDC) method. Five relaxation peaks located at -70, -30, 75, 95 and 105℃ respectively were found in the TSDC curves of different XLPE samples. The activation energies of peaks located at about -70 and -30℃ almost remain unchangeable during the whole aging process, so they can be regarded as intrinsic processes of XLPE. These processes can be explained as the movement of molecule chain in amorphous phase and the reorientation of carbonyl respectively. The polarization charge amount varies little in the recrystallization process and increases in the thermally-oxidative aging period. Peak located at about 75℃ is corresponded to the detrapping process in the crystalline/amorphous phase interface. The activation energy of it rises at first and then stays the same, and its trapped charge amount increases significantly in the thermal destruction period. Peaks located at about 95 and 105℃ are corresponded to the movement of molecule chain in crystalline phase and the melting process of crystalline phase. The total charge amount of them jumps in the recrystallization process, and drops in the thermal-oxidative aging period.