Improvement of on-line monitoring method for insulation of substation DC system

When patrolling process of substation DC grounding offer a plurality of suspected branch faults, the existences of influence factors such as zero drift, transformer remanence, and transformer stability, impact on the efficiency of grounding troubleshooting, leading to wrong selection or missed selection. According to the logical relationship of state variables such as voltage, current and calculated value such as grounding resistance before and after the fault, the causes of wrong selection or missed selection are analyzed, the characteristics of the faults are identified based on circuit schematic, the calculation process of grounding resistance is checked, automatic inspection mode based on logic event driven is proposed, not only to improve the accuracy of DC lookup, but also to identify the branch with zero drift.