Accurate track modelling for fault current studies on third-rail metro railways

The use of a constant inductance and resistance model for rail track impedance in traction power system fault transient studies gives rise to inaccuracies due to the actual frequency dependency of the line. In this paper, an accurate frequency-dependent track model for a third-rail metro railway is described in which the track feeding impedance is synthesized from the self and mutual impedances and represented by a discrete-component linear circuit network. The model is used to simulate current rise in a third-rail traction system short-circuit fault. Results are given for short and long track section feeding lengths and show significant differences compared with a constant-parameter track model