Impedance Decomposition Method and Its Application in Calculating the Impedance of Ballastless Track
Zhang Hanhua1, Zou Jun1, Wang Zhixin2, Yang Jin2, Qiao Zhichao2
1. Electrical Engineering Department Tsinghua University Beijing 100084 China; 2. Beijing National Railway Research & Design Institute of Signal & Communication Beijing 100073 China
Abstract Track signal circuit has been widely used in the railway control system to detect the presence of a train. The track impedance is one of the most important parameters in designing the track signal circuit. To this end, finite element method (FEM) could be a good choice due to its capacity of handling complex geometries and media. If FEM is adopted, the open boundary problems in 3D must be tackled in the first place, because the ballastless track locates in an air-ground half space. Second, if the skin effect of conductor is included, the size of each element has to be less than the skin depth, which results in a huge number of unknowns. Accordingly, the computational time and the convergence problem would be big obstacles in reality. Thus, an impedance decomposition approach is proposed in virtue of the physical nature of impedance computation. The track impedance is decomposed into two parts, i.e., the inner and external track impedance. Each kind of impedance is calculated using an appropriate method, which can essentially reduce the computational burden. To validate the proposed decomposition approach, the impedance of a single conductor above the ground is taken as an example, and is calculated by the decomposition method and analytical formulation respectively. The calculated results agree with each other very well. The proposed decomposition approach is applied to calculate the impedance of the double-block ballastless track in Southern Shanxi railway. The frequency- dependent characteristic of the impedance is presented. The absolute value and the trend of the numerical results can reach agreement with the measurements if the certain error is considered from viewpoint of the practical engineering.
Zhang Hanhua,Zou Jun,Wang Zhixin等. Impedance Decomposition Method and Its Application in Calculating the Impedance of Ballastless Track[J]. Transactions of China Electrotechnical Society, 2017, 32(12): 164-170.
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2017, Vol. 32 
