An Overhead Contact System (OCS) is the arrangement of overhead electrical conductors, supporting equipment and associated components used to transmit traction power to electrically powered trains.

The train normally collects electrical current from the contact wire using a roof-mounted pantograph. The OCS is designed to maintain suitable contact between the pantograph and contact wire throughout the permitted operating speed range while accommodating variations in track geometry, temperature, conductor movement and dynamic interaction.

A typical OCS may include contact wires, messenger or catenary wires, droppers, registration equipment, cantilevers, insulators, tensioning equipment, sectioning devices, feeders, supports and associated fittings. The exact configuration depends on the electrification system and railway application.

OCS may be installed along open route, at-grade sections, viaducts, bridges, stations, depots and tunnels. Different support arrangements may be required depending on available clearances and structural constraints. In tunnels and other restricted-clearance locations, rigid overhead conductor systems may also be used.

The OCS interfaces closely with traction power supply, rolling stock, track, civil structures, signalling, earthing and bonding, electromagnetic compatibility and maintenance access. Its design must also consider electrical clearances, pantograph performance, sectioning, neutral sections and safe isolation for maintenance.

mainline, high_speed, metro, light_rail, freight, depot

EN 50119; EN 50122 series; EN 50367; IEC 60913; applicable railway electrification standards and project specifications