| The traction current and traction power of the high-speed EMU are further increased due to the increasing of the running speed of high-speed EMU.As a result,the dynamic coupling of train moving grounding is much more complicated.The moving grounding system provides a release channel for the grounding reflux during the normal operation of the train and the overvoltage during the transient condition of the train.Therefore,it is of greatly importance to carry out the research on the grounding reflux and overvoltage characteristics for further proposing a moving grounding system optimization method suitable for higher operating speed.Up to date,most domestic and foreign scholars only take the grounding reflux into consideration to optimize the moving grounding system.Therefore,the amplitude and distribution characteristics of the grounding reflux and overvoltage are considered in this paper to carry out comprehensive optimization research on the train moving grounding system.A standard EMU moving grounding system model for normal/transient operating conditions is established in this paper.Through the performance test of the moving grounding system during actual operation,the existing moving grounding system is found to be insufficient.Based on the standard EMU moving grounding system model,normal/temporary,the grounding reflux and overvoltage under state conditions are progressively optimized.Based on Kirchhoff’s law,the theoretical analysis of the "vehicle-catenary-station-rail" traction recirculation system was carried out.The parameters of the standard EMU were accurately measured on site,and the equivalent parameters of the two-dimensional model were calculated.Standard EMU moving grounding system model for transient conditions.Through on-site testing of the performance of the existing EMU’s existing moving grounding system,it is found that the uniformity of the working grounding reflux distribution is poor,and the protection grounding current of each vehicle is quite different,the maximum value can reach 280 A,the minimum value is only 6A,and the over-phase over-voltage is the largest.The value is 6.5kV,and the overvoltage distribution shows a tendency to be attenuated toward both sides of the pantograph.Based on the standard EMU moving grounding system model under normal/transient conditions,the effects of grounding system electrical parameters,working grounding system and protective grounding system on the performance of the moving grounding system are studied.It is found that the overvoltage amplitude of the vehicle body has a nonlinear correlation with the resistance value of the grounding resistor and the parasitic inductance.In the high frequency state,the influence of the parasitic inductance on the amplitude of the overvoltage is dominant.And the amplitude of the overvoltage increases as the length of the grounding cable increases.As the number of working grounds increases,the working ground of low discharge efficiency increases.When set to two-point working ground,each working ground has the highest discharge efficiency,and the maximum value of the protective grounding current decreases by 9.2%;In the head and tail car,the grounding current of the head and tail car protection increased by 15.5%.Considering the grounding reflux and overvoltage,the multi-round progressive optimization of the protective grounding system is carried out.The optimized scheme of the protective grounding system is: the 1st and 2nd shafts of the head and tail vehicles are set to the grounding mode of the grounding resistor of 100mΩ,and the remaining protections are provided.The grounding is set to the direct grounding mode.Compared with the original grounding system,the protection grounding current of each vehicle drops below 100 A,and the over-phase voltage amplitude of the pantograph decreases to 3.08 kV.It drops below 1.5kV,and the overall distribution trend of the protective grounding current and over-phase over-voltage of each vehicle is good. |
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