Locating system for the position of ground faults in biphasic railway power lines with autotransformers. The invention comprises: - a sensor device for measuring the incoming current in the winding of the autotransformer connected to the power supply conductor or the railway line. - an analyzer device that compares and analyzes the intensity measured by each sensor assembly, and that is connected to an electrical power substation. - a calculating device in the substation that receives the signals from each analyzer device and, comparing them with those stored in its memory referring to its electrical section, determines the position in which the ground fault has occurred, in addition to whether the affected driver is the positive or negative. - a presentation team that collects the computer's output signal and shows the results to an operator. (Machine-translation by Google Translate, not legally binding)