Abstract: The reliable operation of the substation DC system is extremely important for the power grid system. How to accurately grasp and understand the detection and handling methods of insulation grounding faults in DC systems is a key issue of concern for power grid operation and maintenance personnel. This article starts with the classification of insulation grounding faults in the DC system of substations. Analyzed the causes and hazards of the malfunction. Summarized the detection methods for grounding faults caused by insulation performance degradation. Corresponding handling methods have been proposed. Provide certain reference for secondary maintenance personnel on how to detect and handle grounding fault issues.