The Research On Dynamic Distribution Model And The Change Law Of Moving Grounding Return Current Of Emu

In recent years,with the improvement of the operation speed of EMU,the traction current gradually increases,and the problem of grounding reflux of EMU becomes more and more prominent.The EMU forms a grounding return channel through the body wheel set rail.Excessive grounding return will cause problems such as electric corrosion of bearings and abnormal wear of carbon brushes,which seriously threaten the safe operation of the EMU.Therefore,it is necessary to deeply study the variation law of grounding return when the EMU works in the power supply section,and provide the optimization scheme of EMU grounding system.This paper discusses the research status of grounding return of EMU,and analyzes the traction power supply mode of high-speed railway in China,the main circuit of EMU and the grounding system.On this basis,combined with the field measured data,the dynamic process simulation model of grounding return current of EMU driving in the power supply section is established.The change trend of grounding return current of each vehicle during the operation of EMU in the power supply section is studied,and the transfer law of grounding current between each axle of EMU is analyzed.On the whole,the grounding current of vehicle 1 shows a gradually increasing trend;The grounding current of 2,3 and 4 vehicles decreases first and then increases.When the EMU runs in each suction line section,the working grounding will guide the traction current of the EMU to the steel rail.The protective grounding of vehicle 3,axle 1,vehicle 6,1 axle,vehicle 2,vehicle 4,vehicle 5 and vehicle 7 will guide the current on the steel rail to the vehicle body,and then the grounding current will flow from the protective grounding of vehicle 1 and vehicle 8 to the steel rail;When the EMU passes through the suction line,the grounding current will enter the rail from the axle closest to the suction line.It is found that during the driving of EMU within the power supply range,the working grounding current of vehicles3,axles 3 and 4 will gradually transfer to axles 2;The protective grounding current of vehicle 1 is transferred from axes 4 of vehicle 1 to axes 3 of vehicle 1;The grounding current of axle 1 and axle 3 of vehicle 2 is gradually transferred to axle 4 of vehicle 2;The grounding current of axle 1 and axle 2 of vehicle 4 is gradually transferred to axle 3 and axle 4.The concept of equivalent value of grounding current of EMU is proposed.The changing grounding current of EMU is equivalent to a fixed current equivalent value to represent the thermal effect of grounding current in the power supply section.Using the dynamic model of grounding return current of EMU,the effects of working grounding mode,resistance value of protective grounding resistor and position on the effective value of grounding return current are studied respectively.The simulation results show that increasing the number of working grounding circuits of EMU can reduce the effective value of working grounding current and improve the uniformity of working grounding current distribution.When grounding resistors are installed for all protective grounding,the protective grounding current of each shaft decreases with the increase of resistor resistance.Finally,the optimization scheme of EMU grounding system is put forward,four working grounding modes are set,and all protective grounding are installed with grounding resistors.After optimization,the effective value of protective grounding current is reduced from 53 A to 17 A,with a decrease range of 67%.The distribution of grounding return current is relatively uniform,and the vehicle body potential is also controlled within a safe range.