Abstract:The transient variation of line electrical parameters in catenary short circuit fault is the basis of researches for technology of line protection and short circuit fault location. Based on Matlab/Simulink, a 24-pulse rectifier circuit model is established, the transient resistance and inductance value of the equivalent catenary and rail network under the skin effect are calculated, the short Circuit fault simulation model of DC traction power supply system is established, the short-circuit fault of the traction network at close and distant points are simulated, the transient variation values of fault current with the different fault distance are analyzed. The simulation results show that the transient current peak of the near-end short circuit is oscillatory and convergent due to the nonlinear devices such as rectifier unit,which proves the accuracy of the model and provides a reference for the precise configuration of the line protection equipments of traction substation system.