Research On Electromagnetic Transient Process Of Electric Locomotive Passing Through Articulated Phase Insulator

The power grid is three-phase symmetric during normal operation while the traction power supply system of electrified railway is a single-phase AC network,which will disrupt the three-phase balance of the power grid and generate negative sequence currents.Therefore,sectioned and phase changed power supply method is used in the traction power system,and articulated phase is widely set in electric railway to prevent out-of-phase short circuits.The articulated phase insulator is a weak link in the electrified railway traction power supply system.Over-voltages occurs frequently as the electric locomotive passes the articulated phase insulator,which may cause the gap’s electric breakdown,short circuit fault and serious influence on the safe operation of the railway.The current situation of present research for the over-voltage at articulated phase insulator when the electric locomotive passing was introduced in this paper,and a comparative analysis of the advantages and disadvantages of various technology was put forward.Besides,the transient process of the electric locomotive passing through the articulated phase insulator was theoretically analyzed and calculated,and the mathematical expressions of the neutral line voltage corresponding to these transient processes were obtained.Substituting the relevant equivalent parameters,the voltage on the neutral line corresponding to the transient process was calculated,and the results were analyzed.There has been a lot of researches on the over-voltage generated by the articulated phase insulator,but almost all the process described of the locomotive passing through the articulated phase insulator were static,and the transient component will basically attenuate to zero within one cycle,while in reality,the locomotive is moving.From the actual measurement results of the locomotive passing the articulated phase insulator,the overvoltage can still maintain a certain period of time when the locomotive is running in the transition zone and the no-power zone.Therefore,the continuation of the electromagnetic transient process and the reason for the longer overvoltage time may be the movement of the locomotive.However,the practice of dividing the transition zone and the non-electricity into countless units will greatly increase the calculation difficulty of the entire electromagnetic transient process,which is difficult to implement with existing computing equipment.Therefore,it is necessary to explore a method that can effectively describe the continuous process of the locomotive passing through the articulated phase insulator with a limited number of discrete processes.The electrical quantities of some electrical components in the equivalent circuit will transition from the old steady state to the new steady state when the locomotive passes through a unit,which will produce electromagnetic transient processes continuously.Therefore,this paper constructs a model to simulate the movement of locomotive in the transition zone and the no-power zone with a finite number of switches.The models of the four transition processes and the locomotive passing through the transition zone and the no-power zone were simulated in Matlab/Simulink.The correctness of the theoretical calculations was verified through the analysis for the simulation results of the four transient processes.Besides,compared the simulation results of the locomotive in the no-power zone and the transition zone with the measured results,which verified that the equivalent model is effective.