Research On Lightning Characteristics And Lightning Withstand Level Of Subway Contact Rail Power Supply Mode

The subway power supply mode mainly includes contact rail and catenary.Compared with catenary power supply mode,the contact rail power supply mode has these characteristics of low construction cost,low failure rate and small impact on urban appearance.Therefore,the contact rail power supply mode has been widely applied in recent years.However,due to the influence of the height of the viaduct itself,it leads to the increase of the lightning range,which is easily attacked by lightning.The overvoltage generated by lightning stroke easily leads to the flashover of the insulation bracket,the damage of the communication and the signal equipment along the metro line.And the subway belong to the no standby power supply system.Once the line is tripping,which will directly lead subway to stop running,and traffic accidents and casualties can be caused in serious circumstances.Therefore,in order to reduce the harm caused by lightning strikes subway lines along elevated section,it is necessary to study the characteristics of lightning and lightning withstand level of metro contact rail power supply.According to the physical process of occurrence of lightning overvoltage,and uniting the real parameters of metro rail along viaduct section,thereby get the lightning strike type when lightning strikes the subway line.And based on the roiling ball method,the lightning stroke type about metro contact rail are divided.On this basis,building the contact rail model of elevated section under different lightning stroke types,the lightning flash-over characteristics under different lightning stroke types are studied.The research founds that two types between lightning striking lightning strip and lightning striking train are prone to occur.When lightning strikes the lightning strip,the lightning current level required for insulation bracket flash-over,which caused by induced over-voltage of the contact rail is lower than that of ground potential counterattack,so the main reason for the insulation bracket flash-over is the induced overvoltage.When lightning strikes the train,the lightning current amplitude reaches 118 kA,which will cause the insulation bracket flash-over through the form of inducted over-voltage,but the cumulative probability is small,so the probability of lightning stroke triggered insulated guardrail flash-over is not high.At the same time,the viaduct section of metro rail model is built based on CDEGS electromagnetic transient simulation program.Under the condition of lightning strikes lightning strip,the influence of different influence factors on lightning withstand level is analyzed,the obvious influence factors are obtained on lightning withstand level.And an elevated section model of subway contact rail built by ATP-EMTP program.The influence of arrester erection method on contact rail lightning withstand level is analyzed,and change rule of lightning discharge current and specific energy of arrester under different grounding resistance of bridge pier are studied.The results show that the lightning strip height,the soil resistivity,the lightning current waveform,the grounding point distance and the lightning stroke position will have very greater influence on the lightning withstand level of contact rail,at the same time,the viaduct height and the grounding material have a relatively small impact.When the installation distance of grounding point is 50-300 m,the minimum lightning withstand level of contact rail is mainly affected by lightning strip height,and the highest growth rate of the lightning withstand level reached 24.73%;With the increase of the grounding point distance,both the lightning strip height and the distance of grounding point have effects on the lightning withstand level,and the influence of the grounding distance on the lowest lightning withstand level is more obvious.Meanwhile,through the study of ATPEMTP electromagnetic transient program,lightning strikes locations of the assembly line of lightning belt,grounding resistance of bridge pier will have a greater influence on the lightning withstand level of contact rail.The erection of the arrester can improve the lightning withstand level of contact rail obviously,the erection density increase of arrester will leads increase of lightning withstand level,and the discharge current and the specific energy of the arrester are proportional to the ground resistance.At the same time,comparing the discharge current and specific energy of different type arresters,it is suggested to use YH5WS-17/45 arrester with smaller residual voltage.Finally,the paper based on building transient simulation model of weak electric equipment,the transmission and distribution law of lightning overvoltage is analyzed,and the influence of lightning stroke on weak current equipment is studied.The influence of soil resistivity,grounding resistance of weak electric equipment and other factors on weak electric equipment.The result shows that the change of rail leakage resistance has obvious influence on rail overvoltage,and with the increase of distance from the lightning point,the rail overvoltage decreases gradually and tends to become steady gradually.When lightning current amplitude is 20 kA,the influence range of lightning strikes on weak current equipment is 36.32 m and 13.73 m in horizontal and vertical direction respectively.At the same time,with the increase of soil resistivity,the change of influence range in horizontal and vertical directions is obvious.However,the influence extent of the change of grounding resistance on weak current equipment under the horizontal direction is higher than that under the vertical direction.