Severity assessment of local ageing defects in cross-linked polyethylene cables based on the high-voltage frequency domain spectroscopy non-linearity and its sensitivity analysis

Abstract

Local ageing defects are the main causes of cross-linked polyethylene (XLPE) power cable faults. This research aims at assessing the severity level of typical cable local ageing defects based on the high-voltage frequency domain spectroscopy (FDS) non-linearity. Experimentally, typical XLPE cables ageing defect conditions are simulated, with different ageing types, degrees, and local proportions. Then, the high-voltage FDS detection is conducted and the results have been analysed. It has been found that the high-voltage FDS non-linearity is only related to the detection voltage and ageing degree. Especially, it is more sensitive to changes in the ageing severity. Thus, the local ageing defect severity assessment method based on non-linearity has been established. Additionally, the sensitivity has been compared between two diagnostic evaluation methods: the high-voltage FDS and the widely used very-low frequency method (VLF, 0.1 Hz). It can be concluded from the comparison result that the proposed assessment method has higher sensitivity than that of the traditional methods. Finally, the effectiveness of the proposed method for evaluating the on-site long cables has been validated. The result demonstrates that the proposed method can assess on-site long cables and has the potential to be formed as quantitative standards.