Calculation and measurement of rail impedances applicable to remote short-circuit fault currents

Accurate knowledge of the values of the self and mutual impedances in electric railway traction power supply networks is important in a number of respects. Third rail and overhead catenary systems use the running rails to return electrical current from moving rail vehicles to power substations, and track signalling systems use the running rails to detect the presence of trains and transmit data for automatic train control. The authors describe how using simulation as part of a design procedure enables exact data to be used, which is an improvement over the approximate models necessary for analytical calculations. In particular, circuit effects, internal and external self impedance, self and mutual impedance values, nonlinearity of the internal impedance and measurement techniques are considered