Traction Current Line - Characteristics

Characteristics

Traction current lines are used to power the railway systems of countries which use alternating current of a lower frequency than the public supply. This is typically the case in the German-speaking countries of Europe. For example 16.7Hz AC is used in Germany, Austria and Switzerland.

A specific example is the Mariazeller narrow gauge railway in Austria, operating with single phase AC with a frequency of 25 Hz, which has its own traction current lines with an operating voltage of 27 kV. These lines are mounted on the pylons of the overhead wire over the lines.

The voltages used for traction current lines are 110kV in Germany and Austria and 66kV or 132kV in Switzerland.

Traction current lines are operated symmetrically against earth. In the case of 110 kV lines, for example, each conductor has a voltage of 55 kV against earth. The grounding is made in larger substations and in power stations for traction current, using transformers for the cancellation of the earth leakage current. As is the case for all symmetrical powerlines there are also at traction power lines twisting points. A traction powerline for one circuit has usually two conductors. Since most traction current lines possess two electric circuits, four conductors are on the pylons as a rule (in contrast with three-phase alternating current lines, whose number of conductors are an integral multiple of three).