Analysis Of Lightning Impact On Track Circuit

In recent years, with more and more electronic equipment are applied to railway signal systems, the systems have been suffering more and more lightning accidents. As important basic equipment of railway signal system track circuit plays a crucial role in ensuring the safety of train operation, improving transport efficiency and enhancing the passing capacity. As most parts of the track circuit equipment are arranged in the open air, the equipment can not run stable due to the poor working environment or even can be scrapped in serious situation. Especially in the thunderstorm season, it is very likely that lightning infringement will do damage to the track circuit equipment so that the train operation runs abnormally. What is more, serious accidents may appear to negatively affect the transportation. Therefore, it is necessary to analyze the influence of lightning invasion on the track circuit in order to provide references for the railway signal system’s lightning protection as well as to improve the lightning protection level of the entire railway signal system. In this case, the recurrence of lightning damage can be eliminated significantly in further.Firstly, according to lightning mechanism and discharge type, the lightning invasion methods on track circuit and its influence on equipment linked to the track circuit are analyzed. At the same time, combined with the catenary lightning overvoltages method, the lightning over-voltages of lightning direct track circuit, lightning track circuit near the ground and lightning catenary pillar earthing alone are also analyzed respectively.Secondly, on the basis of the two-port network mathematical models under normal mode of operation on track circuit, the coefficients of this mode of operation are solved by using distributed parameter analysis method. Therefore the transport equation of lightning overvoltage transmission on the track circuit for normal mode of operation is established. Using the Matlab software to simulate and analyze the transmission characteristics of track circuit, lightning current waveform and the transmission characteristics of track circuit after lightning. At the same time, the influence of ballast resistance on the lightning surge of transmission on rails is also simulated. In the end, it concludes that the lightning overvoltage at the receiving and will decrease with the increasing transmission distance of track circuit and the decreasing ballast resistance. In addition, that the influence of lightning strike to track circuit is the largest can be drawn as well as other conclusions.Finally, the calculation model of the surge propagation characteristics along the rails is proposed using electro-magnetic transient program(EMTP) and the correctness of the model has been proved. By simulating and analyzing the rail potential when injecting the lightning under the situations of open-circuit and short-circuit at the receiving end of the track circuit, both the surge impedance and surge propagation velocity of the rails are calculated.