This system for powering an overhead contact line, which includes a contact wire consisting of a plurality of conductive sections separated by insulating sections, includes power supply sub-stations, each conductive section being connected, on the side of an upstream end, to an upstream sub-station via an upstream controlled switch and, on the side of a downstream end, to a downstream sub-station via a downstream controlled switch. This system includes a detection device, associated with a conductive section, to be monitored, which includes a means for transmitting a characteristic signal to an upstream or downstream end of said conductive section and a receiving means able to receive the characteristic signal at the other end, the receiving means modifying the value of a state signal applied to a control circuit for actuating the opening of the downstream switch and/or of the upstream switch.