Research On Overvoltage Of EMUs Struck By Lightning On Catenary Of High-speed Railway

Because of the vast land,diverse terrain and special lightning activity in China,the laying height of high-speed railway is generally high,and the lightning protection level of traction power supply system is low,so the probability of catenary suffering from lightning is increased.Lightning strikes the catenary system,and the current enters the EMU,which may cause over-voltage of the car body,and will harm the internal high voltage equipment or on-board electronic equipment,and seriously affect the safe operation of the EMU.In order to ensure the safety of driving,the transmission law of lightning current in the EMU body and the over-voltage of the car body caused by lightning contact network are studied,and the measures to improve the overvoltage are put forward.Firstly,the characteristics of lightning activities in China are analyzed,the lightning current model is established by selecting appropriate lightning parameters,and the possible lightning location of catenary system is analyzed.Lightning may hit the catenary,feeder and pillar.Then,the catenary model is established according to the power supply mode and catenary structure of EMU,and the centralized parameter model of pillar,the flashover model of insulator and the model of suspension wire are built specifically.The main circuit of EMU is analyzed,and the internal electrical equipment of high voltage box is equivalent,and the models of high-voltage transformer,lightning arrester and traction transformer are established respectively,finally referring to the parameters of EMU body and grounding system,PSCAD software is used to build the overall model of lightning contact system and EMU.Second,the flashover of T-line and F-Line insulators and the waveform changes of transverse and longitudinal overvoltage of EMU car body were observed when lightning at different positions of catenary.It is found that different positions of lightning contact network,such as catenary,feeder and post,can cause different degrees of overvoltage of EMU body,and the longitudinal overvoltage of head and tail cars and three cars is larger.Change the distance between the lightning strike point and the pantograph of EMU,and explore the relationship between the lightning strike distance and the over-voltage of vehicle body.The farther the distance between the lightning strike point and the pantograph of EMU,the smaller the over-voltage.By changing the simulation conditions,choosing different lightning parameters and grounding methods,this thesis studies the variation law of EMU car body overvoltage.It is found that with the increase of lightning current amplitude,the car body overvoltage increases correspondingly,and the larger the lightning current front time is,the smaller the car body overvoltage is,showing exponential attenuation.The parameters of grounding system also affect the overvoltage of car body.The transverse overvoltage and longitudinal overvoltage of car body change linearly with the inductance value of grounding system,and increase with the increase of inductance value.The resistance value has a certain influence on the overvoltage attenuation.The larger the resistance value is,the slower the overvoltage attenuation is,and has little influence on the amplitude.Lastly,according to the influencing factors of vehicle body overvoltage,the parameters of grounding system are changed to find the suppression method of vehicle body overvoltage.The effectiveness of suppression method is verified by comparing the amplitude of vehicle body overvoltage before and after improving the grounding system.