Abstract: This article analyzes the hazards of insulation faults in the DC system of substations and proposes preventive measures. Firstly, a statistical analysis was conducted on the insulation faults of the DC system that occurred in a certain municipal power supply company in the past three years. The main causes of insulation faults in the DC system of the substation are aging, damage, and moisture in the insulation of the secondary cables and auxiliary contacts of the DC branch. Secondly, analyze the DC insulation faults that occurred in the substation. Finally, corresponding preventive and governance measures are proposed for various types of fault causes. Improve the reliability of substation operation.