Insulation Monitoring and Fault Diagnosis Technology of Cross-Bonded Metal-Sheathed Cable

For addressing the challenge that cross-interconnection of metal sheaths in long-distance high-voltage cables complicates the monitoring of cable insulation faults, it is proposed a fault diagnosis scheme based on resistive current, dielectric loss factor, and sheath current. The voltage and current signals at both ends of the cable are collected, as well as the current signals at the outlet of the grounding box and the transposition box. By establishing an equivalent model of the cross-connected cable, the calculation method for fault diagnosis is derived, and an implementation scheme for fault diagnosis is provided. The insulation monitoring method proposed in this paper is simulated and verified using MATLAB/Simulink software, with simulations conducted to investigate four typical faults: cable insulation fault, sheath open-circuit fault, transposition box immersion short-circuit fault, and cable intermediate-joint breakdown fault. The circuit model of the cross-connected unit is established in the laboratory to verify the method proposed in this paper. The results show that the simulation results are consistent with the test results, and the fault types can be correctly reflected, which verifies the correctness and effectiveness of the insulation monitoring method.