Method for detecting faults on a railway vehicle feeder cable

The method involves setting up a voltage difference between output terminals of reversible sub-stations (20A, 20B) such that current (I) circulates on a power supply line (10) of a railway vehicle between the reversible sub-stations. An impedance value of the power supply line at nominal temperature is determined. The determined impedance value of the power supply line is compared with expected nominal linear impedance (Z-L) of the power supply line at the nominal temperature.