Contact System

equipment used for the transmission of electric power from power plants through traction substations to electric locomotives, motorized railroad cars, streetcars, and trolleybuses. The power is transmitted by means of a sliding contact between an overhead wire of a contact rail and the current collector (or pantograph) of the rolling stock. As a rule, the overhead wire is located above the rails or along the route of a railless transportation line; contact rails are located at the same height as the undercarriage of rolling stock. The overhead wire is mounted on a supporting structure—usually the supports of the contact system or, less frequently, the walls of buildings and other structures (for streetcar and trolleybus systems)—by means of flexible components (cables and wires) located parallel to the overhead wires (catenary suspension) or across it (direct suspension). The supports of a contact system are made of reinforced concrete, steel, or wood. The suspensions are attached to the supports by fittings and insulators.

A contact system is divided into sections to achieve reliability of operation and ease of maintenance. A single section may include open lines and intermediate stations or, in large stations, a group of electrified tracks. Maintenance work requiring a power shutdown is conducted with only one section disconnected, without interruptions of power supply to other sections. The supports of the contact system located along railroad tracks are also used for suspending conductors supplying power to railroad consumers along the right-of-way and as supports for other conductors, such as those used for remote control of sub-stations and for operating various types of switching gear used in the sectioning of circuits.