Condition Assessment of XLPE Cables Based on Isothermal Relaxation Current and Breakdown Voltage

As a non-destructive method of state assessment, the isothermal relaxation current (IRC) method has been widely practiced in Europe, while it has been in a fledging period in most areas. This paper focuses on the applicability of the IRC assessment method and its criterion to the cables under the conditions of production, operation, and testing in China. Samples from 14 different domestic manufacturers were used as the object to reduce the individual difference effect on the experimental results. The result shows that the aging factor obtained by the IRC method increases with aging, but the calculated aging factor is generally larger than that tested in German. According to the test data, the correlation analysis of the aging state and residual breakdown voltage was further explored to verify the aging state criterion. Compared with the German standard, the range of breakdown voltage is relatively narrow, while the range of aging factor is wide under the same aging state in the paper. Differences in the aging evaluation criteria may be related to the production level of the cable, the operating environment, and the IRC test conditions.