Insulation Monitoring and Diagnosis of Faults in Cross-Bonded Cables Based on the Resistive Current and Sheath Current

Abstract

To reduce the induction voltage in the metal sheath, cross-bonded grounding is a widely adopted method in long-distance high voltage power cables, but this introduces challenges to the online monitoring and diagnosis of cable insulation. An online monitoring and diagnosis method for cable insulation based on the analysis of resistive current is proposed in this paper. A theoretical formula for the separation between leakage current and sheath current was derived, and a theoretical formula for the separation between resistive current and leakage current was obtained. An equivalent circuit of a three-phase long distance cable was established using the MATLAB/Simulink platform. The simulation was used to model three typical faults: cable insulation deterioration, open sheath circuit faults, and the sheath breakdown of intermediate joint faults. The results show that the method can be used to monitor each cable’s insulation state under metal sheath cross-bonded, and it also can determine the open sheath circuit faults and fault joint location using the measured current values by the corresponding current sensors increases significantly. Based on the analyses, diagnostic criteria are established for different types of cable faults and fault locations.