Research On Dynamic Simulation Model And Distribution Characteristics Of Grounding Return Current Of High Speed Emu Under Moving Condition

After decades of efforts to develop,China’s high-speed railway has been at the leading level in the world.However,as the speed of the Electric Multiple Units(EMU)is getting faster and faster,the traction current becomes larger and larger,and the grounding return current problem of the EMU becomes more and more serious.The grounding return current of the EMU will cause electric corrosion of the bearing and aggravate the abrasion of grounding carbon brush,which seriously threatens the safe operation of the EMU.Therefore,it is of great significance to study the distribution characteristics of grounding return current under the moving condition of the EMU and put forward an optimization scheme to suppress the grounding return current.In this paper,the research status and significance of the EMU grounding return current are described in detail,then the main components of high-speed EMU are introduced,and the generation of grounding return current of the EMU is analyzed theoretically.On this basis,the dynamic simulation model of grounding return current under high-speed EMU moving condition is built by using PSCAD simulation software.Using this model,the variation and distribution characteristics of grounding current during a moving process of the EMU are simulated and analyzed,which is from the end of supply arm to the traction substation.It is found that each grounding current presents periodic changes and is obviously affected by the suction line.In the whole operation process of the EMU,because there are no grounding resistors in the protective grounding of No.1,No.3,No.6 and No.8 cars,the protective grounding current of these four car bodies is relatively large,while the series grounding resistors in the protective grounding of other car bodies,the protective grounding current of other car bodies is relatively small.When the EMU is running in the section of the suction line,the traction current flows into the rail from the working grounding,the current on the rail flows into the car body through the protective grounding of the middle cars,and finally flows into the rail through the protective grounding of the head and tail cars,and the current flows into the adjacent suction line from the rail.When the EMU axle passes through the suction line,the grounding current will flow into the rail from the grounding system of the axle.The correctness of the simulation model is verified by comparing the field measured data with the simulation data.In this paper,the influences of the working grounding mode,the resistors in protective grounding and the resistance value in the vehicle body connection line to the grounding return current are studied respectively.It is found that increasing the number of working grounding points will reduce the maximum value of working grounding current and improve the balance of working grounding current distribution.All protective grounding systems are connected in series with resistors with a larger resistance value,which will reduce the magnitude of the grounding current,but also increase the car body potential.When the resistance value in the vehicle body connection line increases,the amplitude of the protective grounding current can be reduced to a certain extent,but the effect is not ideal for reducing the amplitude of the protective grounding current of the head and tail cars.Finally,an optimization scheme is proposed from two aspects of the grounding system and the vehicle body connection line.After optimization,the maximum protective grounding current is reduced from 201 A to 62 A,with a decrease of 69%.The grounding current distributed evenly in each car body,and the car body potential is controlled within a safe range.