This paper proposes a distributed-parameter mathematical model of a 25 kV AC traction power network developed using the state variable method for the analysis of HEMI affecting railway TC equipment. The model is formulated on the basis of an equivalent circuit representation and a loop-branch topological matrix, resulting in a system of algebraic and differential equations in state variable method. Transient voltages and currents during contact wire-to-rail short-circuit events are investigated for different fault locations and rail-to-ground resistance values corresponding to summer and winter operating conditions. Simulation results show a significant dependence of current distribution and rail-to-ground overvoltages on environmental parameters. Under winter conditions, the rail-to-ground voltage exceeds permissible insulation levels for TC, indicating the necessity of dedicated protective measures. To simplify the assessment of electromagnetic impact, an equivalent representation using generalized resistance and inductance parameters for each half-wave of the short-circuit current is introduced. The proposed model is validated by comparison with field experimental data from a 25 kV AC traction network, demonstrating an error below 8%.
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