Calculation of the Impedance of a Rail Track With Earth Return for the High-Speed Railway Signal Circuit Using Finite-Element Method

The impedance of the rail track is one of basic parameters to analyze the high-speed railway signal circuit. In this paper, an accurate and fast approach to calculate the impedance of the rail track with the earth return is presented. Two imagined current-carrying sheaths going in opposite directions are placed to encase the rail track. With these imaginary currents, the impedance can actually be divided into imagined internal and external impedance, respectively. The imagined internal impedance can be calculated using the finite-element method without numerical difficulties, and the imagined external one can be evaluated using the analytical formula with the help of the asymptotic extraction technique. The numerical examples validate that the proposed approach and show the proposed approach has a satisfactory accuracy and reasonable computation time.