Evaluation of Repeatability for the Measurement of DC Conductivity of HVDC XLPE Model Cables

Cross-linking polyethylene (XLPE) power cables are widely used as an excellent insulation material for high-voltage direct current (HVDC) transmission. For the design and operation of HVDC-based power cables, the conduction properties of XLPE insulation must be obtained. This study aimed to establish a highly reliable conductivity-measurement system that can diagnose the XLPE insulation of cables before and after aging by evaluating the repeatability of their conductivity. In this study, a conductivity-measurement circuit was constructed using the polarization-and-depolarization-current technique. Conductivity was measured according to the conductor temperature by using an applied electric field, and then the repeatability of the measured conductivity was evaluated using a statistical method. The experimental results show that the minimum repeatability was 6%, thereby demonstrating the establishment of a reliable conductivity-measurement system.