Modelling Methodology for Autotransformer Rail Traction Power System Based on Symmetrical Components: Models of System Components and Fault Study Examples

This paper presents a modelling methodology intended to enable easier and quicker circuital calculations for autotransformer rail traction power systems. The 2 x 25 kV configuration is considered. The classic formulation of the symmetrical components for 3-phase systems is referred to, and transposed in a 2-phase case. The items of plant that compose the power system are modelled as positive- and zero-sequence devices, and the system voltages and currents are transformed as well. Calculation examples are provided for fault currents and fault impedance for system protection purposes. Due to the considerable simplification of the circuital models, the methodology presented enables the designer to perform approximate hand calculations as well as computer-based ones.