Response of a 25 kV AC railway traction system to lightning current transients and mitigation measures

This paper presents the design, simulation and analysis of the distribution of lightning current and transient voltage in a 25 kV AC railway traction system. Consequently, the lightning protection system that may mitigate the adverse effects due to possible lightning strikes has been designed. The Mpumalanga- Richards Bay Coal line in South Africa has been considered for the analysis. The railway system is modelled, consisting of a mast, an insulator applying a back flashover control mechanism, overhead catenary wires, a pantograph, an AC locomotive and the rails. The main component of protection is the surge arrester that is designed using the PincetiGiannetoni model. The surge arrester is rated at 30 kV, with a nominal discharge current of 10 kA. The complete system is modelled and simulated in PSCAD software. The simulations are performed to detect the transient response of critical components of the system when lightning current is injected at locations of exposure, namely; the mast, catenary wires and the pantograph, in the absence and presence of surge arresters. The results show a significant decrease in the peak current and voltage of the selected components when surge arresters are connected.