Kontaktdraad

Kontaktdraad, or contact wire, is the energized conductor in overhead traction systems that supplies electric power to rail vehicles via a current collector such as a pantograph or trolley pole. The wire runs along the length of a route on supporting structures and is kept at a consistent height to ensure reliable contact at varying speeds. It is part of the overhead line or catenary system, which also includes a messenger or catenary wire that provides mechanical support and maintains the proper sag and profile of the installation.

Construction and layout: The contact wire is typically made of copper or an aluminum alloy with reinforcing strands and is tensioned to minimize sag. It is supported by insulators on masts, portals, or gantries and may be attached to a messenger wire that bears the mechanical load. The exact geometry—height above the rail, sag, and spacing—depends on vehicle type, current, and operating speed. In many systems, the contact wire is one component of the overhead line, with the messenger wire handling mechanical support to keep the contact wire smooth and properly aligned for optimal current collection.

Operation and maintenance: The pantograph or trolley pole maintains continuous electrical contact with the moving contact wire, drawing current for propulsion. Wear, corrosion, or contamination can cause arcing and reduced performance, so the system is routinely inspected and the wire tension adjusted with automatic or manual tensioning devices. Operating voltages vary by network, from urban tramways and light rail using lower-voltage DC (roughly 600–750 V) to mainline railways employing higher voltages (commonly 15–25 kV AC) or DC. Maintenance also covers segmentation into feeder sections and ensuring adequate electrical insulation where the line interacts with other structures. Safety considerations address high voltage, energized equipment, and clearance from people and property.