Calculation Of Impedance Of Rail Track For Ballastless Track Line

During the 11^th five-year plan term, 9800 kilometers high speed railway for passenger transportation shall be built in China. This project is a huge construction task. Because of their futures, ballast-less track and joint-less track circuit shall be used in Chinese high speed railway. Owing to the impact of steel networks in ballast-less track, the equivalent impedance of rail track may be changed and the length of track circuit may be shorted. So it is valuable to analyze and calculate the impact of ballast-less track on joint-less track circuit.Based on brief introduction of the structure of ballast-less track and the principle of joint-less track circuit, a coupling model between rail track and double layer steel networks in ballast-less is derived and a formula of the equivalent impedance of rail track is given in the paper. On the basis of the model and the formula, the impact of ballast-less track on impedance of rail track can be explained. This kind of impact is that the resistance in impedance should be increased and the inductance in impedance should be decreased.Secondly, in order to calculate the impact of the coupling between the rail track and the steel networks in ballast-less, some formulas including the mutual inductance between the rail track and the steel networks in ballast-less, the self-inductance of the steel networks in ballast-less, and the mutual inductance between two layer steel networks, are derived.Finally, based on the parameters of a kind of ballast-less track, the resistances, inductances and equivalent impedance are calculated. Compared with the filed test results in Qinhuangdao-Shenyang high speed railway for passenger transportation, the errors between the theoretical calculation and filed test are small. This conclusion indicates that the coupling model and calculating formulas proposed in the paper are correct.The research results may provide some references for the design of ballast-less track and the research of adoptability of ballast-less track on joint-less track circuit.