Based on the parameters of the ±10 kV DC distribution system in Tongli,Suzhou,the transient characteristics of DC unipolar grounding and inter-electrode short-circuit faults are studied. Using the system structure and control strategy of the demonstration project,the electromagnetic transient model is established in the environment of PSCAD. Many fault cases are considered in our work,including the AC side,the converter side,the DC side,as well as the load side. The overvoltage and overcurrent of the system are discussed. Furthermore,the impact of grounding fault resistance on the transients on the DC side of system is quantitatively studied. The simulation results indicate that there is a continuous DC component on the AC side in the case of single pole to ground fault on DC distribution system. The converter is not blocked,and the DC-DC converter high-voltage side capacitor is discharged. The grounding resistance of fault has a significant effect on the voltage and current transients of DC side. The pole-to-pole ground fault produces a severe overcurrent,which triggers the converter overcurrent protection,which triggers the converter overcurrent protection. The fault current is an important cause of the overvoltage. The overvoltage at both ends of the inductive element is large,which has little impact on the AC side of the system.