Research On The Lightning Impulse Transient Behavior Of Grounding System Of Integrated Signal Building And Adjacent Communication Signal Tower In High-speed Railway System

Track circuit system, the key subsystem of communication signal parts in high-speed railway system, is of great significance to the security, stability, and efficiency of railway operation. During direct lightning, the existing track circuit equipment, for its ground-floating framework and lack of safeguards of ground potential rise (GPR), is prone to breakdown. However, for their lightning-triggered structures, integrated signal building, the main placement of track circuit equipment, and its adjacent communication signal tower of high-speed railway system are vulnerable to lightning. For lack of consideration on GPR withstand ability of track circuit equipment, the existing assessment methods of tower-building grounding system fails to meet the current requirements of its grounding performance assessment. The studies and main conclusions specific to the lightning impulse transient behavior on grounding system of integrated signal building and adjacent communication signal tower in high-speed railway are as follow.According to completed projects and relevant construction standards in high-speed railway, the model on lightning probability of tower-building system, based on Monte Carlo Method, has been built. The regular pattern, lightning probability of communication signal tower drops with the increasing of distance between the communication tower and the building, are figured out.Electromagnetic calculation model of tower-building grounding system, by Moment Method, has been built. Impulse grounding resistance of communication signal tower, transient potential raise of tower-building grounding system affected by lightning points, connection of grounding grids, soil resistivity, and the distance between tower and building are calculated and it is shown that equal potential connection mode can reduce the transient potential raise of lightning parts but contribute to potential raise of no lightning parts. The higher soil resistivity, the more significant effect. However, as to the parameter of distance between the communication tower and the building, that effects vary with lightning points.By tests launched on the relevant test platform, the characteristics of ground potential coupling and withstand voltage on ports of the key equipment in track circuit system have been explored. It is shown that grounding coupling coefficient of Analog Network is the highest of mentioned key equipment and that of the audio-frequency signal transmitter is the lowest. In addition, that 3 key equipment shared almost the same withstand voltage of their ports, about 4.20kV.Guided by the theory of statistics, risk assessment method of track circuit equipment, used to estimate lightning risk of such equipment, has been put forward. Under that assessment results, the conclusion, optimization of equipment grounding system alone has little effect on reducing risk of lightning damage and the further device-level protective measures are needed, has been drawn. What is more, installation of overvoltage protection device between shell and ports is the most feasible and effective method of GPR protection.