Research On Performance Analysis And Optimization Method Of Protective Grounding Of High Speed EMU

With the continuous acceleration of EMU speed,a lot of problems related to protective grounding are gradually exposed.Experience has shown that under normal running conditions,unreasonable setting of protective grounding will result in excessive return current,electric corrosion of bearing,abnormally wear of carbon brush and so on.Under the special transient condition,the unreasonable setting of the protective grounding will cause the EMU body potential to be too high and the speed sensor to burn down and so on.The systematic research on the EMU protective grounding is required according to the characteristic and existing problem of the existing EMU protective grounding.Considering the grounding return current and body overvoltage,the optimal design of protection grounding is carried out.The traction power supply mode,the circuit of the EMU and the grounding system are introduced respectively in this paper.The characteristic and existing problem of the existing protective grounding are analyzed.The traction power supply system and EMU are modeled respectively.The grounding return current simulation model during the EMU passing the boosting cable is established with the whole process of the EMU passing the boosting cable taken into consideration.The variations of the protective grounding current during the EMU passing the boosting cable and at the time of the EMU passing the boosting cable are analyzed based on the grounding return current simulation model.The influence of the boosting cable on the grounding current is studied.The distribution characteristic of the protective grounding current is revealed.The problems which remain in the existing protective grounding are pointed out.The overvoltage simulation model during the EMU rising pantograph is built with the circuit state of the EMU during the actual rising pantograph taken into account.The protective grounding performance of the existing grounding mode is analyzed from the aspect of overvoltage.The protective grounding performance includes the amplitude and distribution characteristic of the body overvoltage.The propagation law of overvoltage on the EMU body is obtained.The problems which remain in the existing protective grounding are pointed out from the aspect of overvoltage.The correctness of the simulation model is verified by experiments.The effects of the parameter,number and position of the protective grounding on the grounding current and the body overvoltage are studied based on the grounding return current model and the rising pantograph overvoltage model.The allowable range of the grounding resistor value is given.And the number of the protective grounding is suggested.Taking the grounding return current and the EMU body overvoltage into account,the optimum design of protective grounding is carried out.A hybrid grounding method of non-equivalent resistor grounding and direct grounding is proposed.After optimization,the current peak of protective grounding current decreased by 73%,and the grounding current distribution became relatively uniform.As for overvoltage,the overvoltage at the top-bottom and bottom-rail fell 28.9%and 50%,respectively.