Characteristic Analysis And Suppression Method Of Switching Overvoltage Of Circuit Breaker On High Speed Train

With the rapid development of my country’s high-speed rail,the operating speed and traction power of EMUs continue to increase.At the same time,in the actual operation process,safety issues related to the on-board high-voltage electrical system are gradually exposed.High-speed trains need to frequently operate on-board circuit breakers in working conditions such as neutral-section passing and short-circuit fault handling.At the moment of opening and closing of the circuit breaker,the magnetic energy and electric field energy between a large number of inductance and capacitance in the traction power supply circuit will be converted mutually,resulting in electromagnetic oscillation and high-amplitude switching overvoltage.The high-voltage equipment that has direct electrical connection with the on-board main circuit breaker will immediately suffer overvoltage shock,which will cause the insulation aging or breakdown of the equipment in the high-voltage box,and the main insulation and longitudinal insulation of the on-board traction transformer will also be subject to high-frequency overvoltage;In addition,overvoltage will also be induced to the car body,causing the ground potential of the electronic communication equipment on the car to be unstable,threatening the safety of train operation.This article first conducts an in-depth investigation of factors related to switching overvoltage such as the external power supply mode of high-speed trains,the high-voltage main circuit of the train,and the high-voltage electrical equipment onboard.A high-speed train switching overvoltage simulation model of the vehicle-catenary system was established based on the actual measured parameters.Through simulation,the switching overvoltage characteristics of the circuit breaker under the three conditions of disconnecting the no-load transformer,connecting the no-load transformer and disconnecting the short-circuit load were studied.Simulation results show that the switching overvoltage generated by disconnecting the short-circuit load is the largest.Subsequently,the influence of the three key factors of catenary voltage phase,transformer distributed capacitance,and traction network impedance on the overvoltage of the circuit breaker opening and closing operation is further analyzed.Then,through the analysis of the measured waveform characteristics of the static test of the train disconnecting no-load transformer,the reignition overvoltage phenomenon of the circuit breaker was found,and the phenomenon was verified through spectrum analysis.The measured reignition overvoltage spike frequency was concentrated around 300 k HZ.Subsequently,the mechanism of the reignition overvoltage was analyzed,and the vacuum circuit breaker opening model considering the reignition characteristics was built.The influence of the recovery rate of the dielectric strength between the contacts of the circuit breaker and the high frequency arc extinguishing ability of the circuit breaker on the reignition process is analyzed.The influence is that the recovery rate of the dielectric strength affects the number of overvoltage reignitions and the high-frequency arc extinguishing ability affects the reignition high-frequency current amplitude of the circuit breaker.Finally,based on the vehicle-catenary system model and the vacuum circuit breaker opening model considering the reignition characteristics,three types of combined suppression using zinc oxide arrester,RC suppressor,and opening resistor-RC suppressor are proposed.The protection scheme,and the parameter selection and working wiring of the three suppression schemes are analyzed in detail.Considering the two situations of cutting off the short-circuit load and the occurrence of reignition,the overvoltage suppression effect of the three schemes has been evaluated.The results show that the suppression effect of the opening resistor-RC suppressor is the best.The amplitude of overvoltage is reduced by56.7%,the oscillation frequency is also significantly reduced,and the high-frequency oscillation caused by reignition is eliminated.This paper analyzes the characteristics of the overvoltage of the circuit breaker in high-speed trains and analyzes the main factors that affect the overvoltage.It provides a solution for the suppression of the overvoltage of the circuit breaker in the actual project.