Electromagnetic Crosstalk Analysis Of Signal Cable By Traction Power Supply System In Bridge Section

Railway signal cable shoulders the important task of transmitting the information of railway operation control.However,due to the limited laying space in the railway field,the coupling between cables is easy to occur,and the electromagnetic interference problem of signal cables caused by the traction power supply system is increasingly prominent,especially in the bridge section where the through grounding wire and the signal cable are laid in the same cable slot along the railway line which has a negative impact on the safety of railway transportation.Therefore,in the thesis,the signal cable of the railway field is selected as the research object,and the electromagnetic crosstalk of the signal cables in the traction power supply system is studied.As the signal cable is laid along the railway track,the long loop structure formed between the signal cable and the earth is easily disturbed by the coupling of external interference sources through the magnetic field,and its long line structure is also easily affected by the longitudinal electromotive force such as ground potential difference.In the traction power supply system,there are many traction backflow paths and complex coupling modes which can cause crosstalk on signal cable.Therefore,in the crosstalk analysis of signal cable,the factor of signal cable should be incorporated into the model of traction power supply system to establish a complete and accurate model.Firstly,the traction network skeleton containing shielding layer of signal cable was equivalent to the parallel multi-conductor transmission lines,and the impedance matrices and admittance matrices of these conductors were calculated respectively,and the through grounding wire is modeled separately considering the different laying modes of the through grounding wire in subgrade section and bridge section.Secondlly,the traction power supply system was divided into series elements and parallel elements,which were combined according to the structure of the traction power supply system to establish the chain network model of the traction power supply system.Finally,the power flow algorithm was used to simulate the model,and the reliability of the model was verified by comparing with the rail potential distribution theory and traction reflux measured data.Based on the analysis of the principle of magnetic field coupling and electric field coupling suffered by the signal cable respectively,the electromagnetic crosstalk model of the signal cable caused by the traction power supply system is established.By analyzing the sources of crosstalk,it is concluded that the signal cable is mainly affected by the current in the through grounding wire and the shielding layer of the signal cable,and the expression of the longitudinal induced electromotive force of the signal cable caused by crosstalk is presented.The longitudinal induction electromotive force distribution of the signal cable of per unit length under normal operation conditions is simulated by using Matlab software.The simulated results are integrated to judged whether it exceeds the limit value of the specification,and the electromagnetic crosstalk of the signal cable under fault condition is analyzed.In order to further study the influence of the distance between the through grounding wire and the signal cable,single-ended grounding and double-ended grounding of signal cable,bridge section and non-bridge section on the electromagnetic crosstalk of signal cable,the results of signal cable crosstalk under the above conditions are simulated separately,and the measures to reduce the electromagnetic crosstalk of signal cable are proposed according to the results of simulation analysis.