Abstract: A contact line system is provided for traction supply of an electrical tractive vehicle. It contains a contact line being contacted by a current consumer of the tractive vehicle for energy transmission. It further contains a central substation for converting a supply voltage into a contact line voltage which is electrically connected to the contact line via a section exit for supplying of energy. It additionally contains a protection device for interrupting the energy supply upon recognizing a failure which has a central measurement device for measuring a parameter in the section exit and an evaluation device for recognizing a failure. The protection device has decentrally arranged measurement units for detecting parameters outside of the substation and a data transmission system for transmitting parameter measurement values to the evaluation device. The evaluation device evaluates the decentrally detected parameter measurement values for failure recognition.