Power systems and overhead lines – Infrastructure and track :: Trackopedia

The catenary supplies vehicles with the energy required to power them. It is the last link in the chain of the traction power supply, which begins at the power station. The catenary is required, since electrically propelled rail vehicles – unlike in industry – are mobile, and some are travelling internationally. Therefore, there are certain standards for the interaction of overhead line and pantograph systems with which all vehicles to be used on these lines must comply. Where appropriate, different pantographs are fitted (one for Germany and Austria, a second for Switzerland).

In general, and on all continental European railways, the external power comes from the catenary which supplies the electrical load with power from above. The overhead catenary either uses special wire profiles made of copper alloys or small rail profiles. The latter are widely used in tunnels.
Instead of an overhead line, some underground railway lines and commuter railway lines have a power rail at the side, a third rail, which makes smaller tunnel cross-sections possible and thus lower construction costs. Here the voltage is, however, limited to 1,000 V AC or 1,500 V DC. Both systems are installed on the two system-S-Bahn (commuter railway) in Hamburg. There is a catenary and a live rail at the side. The use of an underground power supply, such as on some inner-city track sections of trams, in particular, in France has made little progress. It can be recognised by a covered slot centred between the rails of the track which carries the power cable underground.

The overhead wires of high-speed lines are not only designed differently to those of conventional railway systems, due to the mechanical stresses, they are also made of a special alloy. This provides better contact, thus reducing voltage breaks between the contact wire and pantograph. The TGV in France shows that speeds up to 350 km/h can be achieved in normal operation without any problems. However, the overhead line system was strengthened for the well-known record runs.