Application Of EMT Theory To The Analysis Of Crosstalk Between Railway Signal Cables

With the rapid development of high-speed railway and heavy-load railway, electrified railway traction power which increases significantly, as well as a large number of power electronic devices used in railway system, makes the electromagnetic environment of railway more and more complex. The railway signal equipment is also interfered frequently. Given this situation, related theoretical research and calculation are needed. But the rail system is a complex electromagnetic system which is composed of high voltage system and weak current system. It has characteristics of a large physical size, broad frequency spectrum and high electromagnetic field. Compared to other complex electromagnetic system, such as plane, automobile, electromagnetic interference analysis of high-speed rail system is more complex. The traditional FEM, FDTD numerical method is not suitable for electromagnetic analysis of such complex system.Electromagnetic topology (EMT) theory proposed by American scholar C E Baum et al. in the mid-1970s is an analysis method which meets the trends of electromagnetic compatibility theory and technology development. In the complex electromagnetic system such as railway system made up of high voltage system and weak current system, both low frequency conduction and high frequency radiation problems exist. Electromagnetic topology theory effectively combines "field" and "circuit" analysis method, and greatly reduces the difficulty of the analysis of complicated electromagnetic system. The domestic research on EMT is still in its infancy. Although in the United States and France, EMT has been applied to the EMC analysis of aircraft, missiles, satellites, automobile and other fields, there is little research on the application of EMT in the railway system.The typical electromagnetic interferences that exist in railway are analyzed firstly in this thesis. Then the basic theory of electromagnetic topology method and the derivation process of the BLT equation are introduced in detail. After that, a typical scenario of electromagnetic interference exists in railway, namely the interference coupling between railway connecting ground wire and the adjacent signal cable, is chosen as the object of study. The corresponding electromagnetic topological model and BLT equation are established. Then the crosstalk between two cables was carried out by using MATLAB program simulation. The results are compared with those obtained by using the lumped parameter model and distributed parameter model, to verify the feasibility and effectiveness of electromagnetic topology analysis method. Finally, based on the established EMT model and BLT equations, the effects of different grounding and shielding methods on the shielding effectiveness of signal cable in the railway environment is studied. A new shielding and grounding method which may significantly reduce the crosstalk is proposed.