Electrical evaluation of 30 years operation 6.6 kV XLPE cables depending on installation location

Abstract

As the number of AC XLPE cables operated for more than 30 years increases, interest in aging evaluation of insulation materials is increasing. Therefore, it is necessary to study the insulation characteristics of old cables in order to determine the replacement time of aging AC XLPE cables. However, the prediction of residual life in power distribution cables is arduous due to the difficulty in managing their operating history. In this paper, the electrical characteristics of 30 years operation 6.6 kV XLPE cables were evaluated according to the installation location in the power station. Tan delta test was performed on a 6.6 kV XLPE cable operated for 30 years depending on the installation location. After analyzing the measurement data and classifying them into safety and warning levels, the XLPE cable was peeled to conduct dielectric breakdown tests on the specimens. The XLPE cable installed in the boiler feed pump exhibits higher Tan d and lower breakdown voltage compared to other locations, indicating a more progressed state of degradation. The cable of the de-heater booster pump showed excellent performance with a low Tan delta value and high dielectric strength. The cables installed in the cooling tower showed both non-degraded and deteriorated cables.