A zero crossing protection method for DC distribution network

In the field of relay protection in DC distribution networks, quickly and reliably identifying DC line faults has always been one of the challenges. When a fault occurs in a DC line, the current in the line will suddenly increase and flow into the fault point from both sides of the line. Based on this, this article proposes a protection method for DC zero crossing, specifically by detecting the zero crossing characteristics of the current on both sides of the line, determining whether the line has a fault, and then cutting off the line to avoid further expansion of the fault. Simultaneously analyze the impact of transition resistance and lightning on protection criteria, and propose corresponding measures. Finally, in order to further verify the feasibility and effectiveness of the proposed method, a typical DC distribution network model was established based on PSCAD software, and the accuracy of the typical fault analysis and protection method criteria was set in the model. The simulation results show that the zero crossing protection method proposed in this paper for DC distribution networks can accurately identify faulty lines based on the zero crossing characteristics on both sides of the line. This method has the characteristics of simple principle and easy implementation, and can adapt well to DC distribution networks.