Study On The Effect Of Grounding Methods Of High-speed EMU On Distribution Of Grounding Return Current

High-speed railway has a rapid development all over the world due to high speed,safety and comfort,large carrying capacity,eco-friendly and many other advantages.As the key part of high-speed railway system,high speed EMU is closely related to the safe operation of high speed railway.In recent years,with the continuous increasing of train speed and traction current,the phenomenon caused by unreasonable settings of grounding system occurs frequently such as uplifting of the car-body potential and sensor burned.The grounding system has become one of the most key technologies to ensure the safe operation of high-speed EMU.Therefore,according to characteristics of grounding methods for different types of EMUs,It is urgent to have systematic study on grounding methods of high-speed EMUs.In this paper,grounding methods of existing china's high-speed EMUs were introduced.Based on grounding method of CRH380B EMU,Theoretical analysis model was established.According to this model,the distribution mechanism of grounding current was analyzed,and the grounding current was calculated.Simulation model of grounding system of high-speed EMU was established,and the correlative parameters in this model were determined.Based on established simulation model of grounding system,simulation analysis of grounding current was carried,and this model was proved to be reasonable according to the comparison between test results and the simulation results.According to the working grounding methods of the existing high-speed EMUs in China,simulation analysis on distribution of grounding return current was discussed under the different working earthing methods of high-speed EMUs.The results show that the amplitude of maximum working grounding current is decreased in different degrees with the number of working grounding points increased.Setting up four working grounding points can not only reduce the working current to the maximum extent,but also balance the distribution of the grounding current in different working grounding points;Current circulation in working grounding system occurs under the condition of setting eight working grounding points,and current in rail would flow back to working grounding devices;By changing locations of working grounding points when two-way or three-way working grounding was set at ground terminal of traction transformer,the best working grounding methods were obtained.The effect of protective grounding methods on distribution of grounding renturn current was studied from two aspects.Firstly,the effect of changes of two protective grounding positions of the same carriage on improving distribution evenness was studied.Secondly,the suppresion effect of three schemes of protective grounding with equiping grounding resistance on return current flowing on EMU's car-body was studied based on protective grounding methods of CRH380B EMU.According to the three protective grounding methods,the influence of grounding resistance values on protective grounding current and potential of car-body to axle end was discussed.Finally,the scheme of protective grounding with adding grounding resistance was tested,and correctness of the simulation results was verified.The above research provides a theoretical basis for the improvement of the grounding system and standard formulation for high-speed EMUs.