Study on the Charge Transfer Criterion for the Pole-to-Ground Fault in DC Distribution Networks

After a pole-to-ground fault occurs in the DC distribution network using low current grounding, the fault pole voltage drops while that of the non-fault pole rises, which is harmful to equipment insulation and operational safety. Therefore, it is necessary to accurately identify and locate faults with protection equipment. In order to solve the pole-to-ground fault in DC distribution networks using low current grounding, the characteristics of different fault current loops are studied. The distributed capacitance discharging loop at the fault pole, the distributed capacitance charging loop at the non-fault pole, and the feeding of system grounding loop current into the fault grounding point current are analyzed. On this basis, a protection criterion for distinguishing the internal fault from the external fault by the amount of transferred charges, which can be calculated based on the transient differential current, is proposed in this paper. The simulation results show that the proposed pole-to-ground fault criterion can reliably identify the fault line while being immune to the influence of transitional resistance.