The Influence of Line Impedance on Leakage Current Detection in Low Voltage DC Systems

The insulation of the power system may be damaged due to the damage of the cable or the degradation of the connection performance, which will affect the reliability of the power system. However, long cables and multiple connections increase the probability of faults, which brings difficulties detecting fault and location. When the fault point is grounded, a leakage current will be generated. The influence of line impedance on leakage current detection should be analyzed in detail. At first, a leakage current test platform is designed which can be set to two voltage levels (200V, 400V) as well as at different types of leakage current. The leakage current of cables of different lengths is simulated by connecting different equivalent impedances. The characteristics of leakage current collected from the experiment were analyzed, and the influence of line impedance on leakage current detection results was found with the combination of circuit analysis. Then, according to the analysis results, a Matlab/Simulink simulation model is established, and the validity of the proposed law is verified by modifying the simulation conditions. Then, the test platform was used to modify the conditions for relevant tests to verify the effectiveness of the method. Simulation and experimental results show that the rule is effective. Finally, the guidance of residual current device (RCD) configuration is given according to the influence rule of line impedance on leakage current detection.