Abstract: The fast grounding switch has both voltage and current double arc suppression effect,but traditional analysis does not take the effect of voltage drop on the current at fault point into account,which needs further analysis of arc suppression performance.Considering the dynamic parameters of the fault line,a single-phase grounding fault model of distribution network with fast grounding switch is established,and the expression of the fault point current is derived by the symmetrical component method.The calculation results show that the fault current is affected by multiple factors such as load current of fault line,sequence impedance,interphase capacitance,fault distance and transition resistance.The model of fast grounding switch arc circuit is analyzed to show that the fast grounding switch can effectively suppress intermittent arc grounding overvoltage.But in the process of stable low flame retardancy caused by the dynamic parameters of the fault line,the fast grounding switch may increase the fault point current,which is not conducive to the extinguishing of the arc.Combined with the advantages and disadvantages of the fast grounding switch,suggestions are put forward for its arc suppression application of fast grounding switch or cooperating with Petersen coil.Finally,the results of the analysis are verified by MATLAB simulation.