Effect of thermal ageing on space charge characteristics of cross-linked polyethylene

In order to understand the thermal ageing effect on space charge characteristics of XLPE in the strong DC field, accelerated thermal ageing tests were conducted on XLPE samples. In this study, dicumyl peroxide (DCP) and low density polyethylene (LDPE) was selected to prepare samples. The PEA method was utilized to measure the space charge distribution characteristics of aged samples under DC voltage (50kV/mm). The impact of ageing on the internal space charge evolution as well as the average space charge density was discussed. Experiments and analysis results show that thermal ageing induces negative charge traps to samples and increases both the deep and shallow charge traps. Furthermore, it indicates that space charges distribution and the average charge density reflect the insulation properties of samples. The internal structure of XLPE specimens is changed and the insulation properties of specimens degraded as the aging time prolonged. These results provide theoretical support for further research on the effect of the space charge characteristics on properties of the power cables.