Insulation Monitoring Method for Low Voltage DC Cables in Distribution Networks

In order to maintain reliable power supply for secondary equipment such as relay protection and automatic devices, electrical measuring instruments, and operating power supplies in the distribution network, real-time monitoring of low-voltage DC systems is necessary. The current DC cable insulation monitoring device has the problem of inaccurate insulation resistance calculation due to the lack of consideration of cable stray parameters. This paper proposes a low-voltage DC cable insulation monitoring method based on unbalanced bridge branch leakage current detection for distribution networks, and studies the influence of DC cable stray parameters on the transient process of unbalanced bridge branch leakage current detection. Matlab/Simulink simulation shows that using the value after the calculated resistance reaches stability as the insulation monitoring resistance can accurately reflect the insulation resistance value of low-voltage DC cables.