A New Method of Ground Fault Location in 2 x 25 kV Railway Power Supply Systems

Owing to the installation of autotransformers at regular intervals along the line, distance protection relays cannot be used with the aim of locating ground faults in 2 x 25 kV railway power supply systems. The reason is that the ratio between impedance and distance to the fault point is not linear in these electrification systems, unlike in 1 x 25 kV power systems. Therefore, the location of ground faults represents a complicated task in 2 x 25 kV railway power supply systems. Various methods have been used to localize the ground fault position in 2 x 25 kV systems. The method described here allows the location of a ground fault to be economically found in an accurate way in real time, using the modules of the circulating currents in different autotransformers when the ground fault occurs. This method first needs to know the subsection and the conductor (catenary or feeder) with the defect, then localizes the ground fault's position.