Research On Electromagnetic Compatibility Of Urban Railway Signal System Under 25kV AC Traction System

In recent years,China’s cities have developed rapidly,the urban area is expanding,and the urban population is increasing year by year.The traditional urban railway,which adopts DC 1500 V traction power supply system,has begun to fall behind people’s growing travel demand in terms of transport capacity.In order to further enhance the transport capacity of urban rail transit system,part of the urban railways changed to use AC 25 k V power supply system to improve the power supply efficiency and driving force.The signal system of AC 25 k V urban railway still adopts the subway system.With the change of power supply system and the promotion of power supply voltage level,the electromagnetic compatibility of the low current rail side equipment such as axle-counting and communication equipment under the AC 25 k V traction system still needs to be further studied and analyzed,to ensure the safe and reliable operation of the urban rail transit system.In view of the arrangement of long distance parallel laying of railside weak current cable and strong current cable,as well as the existence of a wide frequency range of electromagnetic disturbance around the line and the open air interface of the wireless communication system,this thesis analyzes two prominent problems which affect the electromagnetic compatibility of AC 25 k V urban railway signal system:(1)Crosstalk coupling of strong current cable to signal cable of axle counter equipment beside tracks;(2)The influence of high frequency electromagnetic noise on vehicle-ground wireless communication system.The method of electromagnetic simulation and numerical calculation is applied in this paper,and the crosstalk coupling between strong electric power cable and weak electric signal cable of axle counter equipment is studied.Firstly,the simulation models of strong and weak cables without grooves and with grooves are built by using simulation software,and build test models in the laboratory according to the simulation Settings.By comparing the analytical solution,simulation results and test results,the error is within 5d B,indicating that the simulation model is effective.Then,based on the actual wiring mode and cable type of the railside cables,the simulation results show that the crosstalk coupling voltage corresponding to each frequency point under different shielding mode,different grounding mode and different cable length are allμV stages.The sensitivity level obtained by the immunity test of the axle counter equipment is m V level.It is concluded that the coupling disturbance of the strong and weak cables will not affect the normal operation of the axle counter equipment under the actual arrangement.Then,the theoretical anti-interference models of WLAN and LTE wireless communication systems are established.In order to ensure the normal transmission of information by WLAN and LTE system,the minimum field strength of the communication signal is respectively 41.9d B μV/m and 29.42 d B μV/m.By comparing the measured data with the theoretical anti-jamming model,the anti-interference performance of the wireless communication system is analyzed.Through theoretical analysis,simulation,laboratory test and field measurement,the influence of low frequency disturbance on axle counter equipment by the way of crosstalk coupling is obtained.The electromagnetic compatibility of WLAN and LTE wireless communication systems in AC 25 k V urban railway system is studied by theoretical analysis and field measurement.The electromagnetic compatibility of urban railway signal system under AC 25 k V traction system is studied.