Research On DC Insulation Detection Algorithm For Power System

The DC power supply system is power supply for protection,signal,communication and other circuits in power plants and substations.It has long bypass circuits and many distribution branches.Due to environmental,man-made,and natural factors,the insulation of the line is often reduced,which in turn the protection device malfunctions,even the fuse is blown or the main circuit trips and other serious consequences.In order to ensure the reliable operation of these branch networks and prevent accidents caused by insulation problems,DC insulation monitoring devices are installed in power plants and substations.Generally speaking,since the positive and negative bus of DC system are not grounded,the system can continue to operate normally when grounding occurs at one point,and the protection relay will not operate.However,according to the actual operating experience on site,one-point grounding will also cause the export protection relay to malfunction.In addition,due to the existence of zero drift of DC leakage current sensor,the insulation resistance calculation is inaccurate,and the insulation monitoring device often misses or misreports,causing safety hazards to the operation of the DC system.Based on the existing problems of DC insulation detection,this paper proposes the design method of single-arm unbalanced bridge DC insulation detection system,and derives the single-arm-based bus insulation algorithm and branch insulation algorithm in detail.Based on this algorithm,a portable DC insulation testing and verification integrated machine is designed,and the effectiveness of the algorithm has proved through the experiment of the integrated machine.