Multi‐type defect detection and location based on non‐destructive impedance spectrum measurement for underground power cables

Abstract

Power cable defect detection and location is a crucial aspect in power asset maintenance. Impedance spectrum measurement can be used as a non‐destructive tool for cable monitoring. Defects from overheating and moisture ingress are investigated by the authors, and it is shown that multi‐type cable defects can be detected and located by this methodology. With both electromagnetic analysis and experimental investigation, the relation between impedance variation and the dielectric permittivity is studied to reveal the method's mechanism. An approach to implement such impedance measurement online is proposed and its perspectives in terms of sensitivity is investigated by field scale tests. It is shown that 2% impedance variation due to defect should be detectable. Field scale tests show perspectives for online application with signal coupling through a high‐frequency current transformer with focus on the differences in waveforms obtained from the impedance measurements.