What is an Overhead Contact System (OCS) and its relation to power delivery?

• A. A general term for overhead wire systems (catenary) delivering traction power to trains.
• B. A device used to switch tracks.
• C. A system that converts AC to DC power.
• D. A track-side signaling device.

Answer: (A)

The main idea is that the Overhead Contact System is the network of overhead wires that delivers traction power to trains. It provides the electrical energy the train needs by allowing a pantograph on the train to slide along and draw current from the overhead contact wire as the train moves. This power comes from electrical substations that convert grid or generator power into the appropriate traction voltage, which can be alternating or direct current depending on the system. The OCS includes the contact wire itself, support structures, and tensioning elements that keep the wire at the right height and tension. It’s distinct from trackside switching devices or signaling equipment and from onboard power conversion hardware, all of which are separate parts of railway operations.