Ground Fault Location in 2 × 25 kV High-Speed Train Power Systems by (Auto)Transformers Currents Ratio

High speed trains supply is, nowadays, performed by 2 × 25 kV power systems. If a ground fault occurs, its location and correction are crucial to minimize downtime. One of the methods for locating ground faults in power systems is the impedance method. This was a good solution for 1 × 25 kV railways power systems, as the ratio between reactance and fault distance is linear. However, the use of autotransformers between the catenary, feeder and rails makes this ratio non-linear in 2 × 25 kV configuration. This work presents a novel ground fault location method for 2 × 25 kV power systems. The new method is based on the ratio of the currents of the autotransformers and the substation transformer. The main contribution, compared to previous methods developed, is that this new method is insensitive to the fault current variations produced by the network voltage fluctuations or by the main transformer tap changer position, among others for 2 × 25 kV power systems. The novel approach has been corroborated by numerous experimental tests in the laboratory and computer simulations, with satisfactory results.