Traction substation


A traction substation, traction current converter plant or traction power substation is an electrical substation that converts electric power from the form provided by the electrical power industry for public utility service to an appropriate voltage, current type and frequency to supply railways, trams or trolleybuses with traction current.

Conversions

These systems can be used to convert three-phase 50 Hz or 60 Hz alternating current for the supply of AC railway electrification systems at a lower frequency and single phase, as used by many older systems, or to rectify AC into direct current for those systems using DC for traction power.

Equipment

Rotating

Originally, the conversion equipment usually consisted of one or more motor-generator sets containing three-phase synchronous AC motors and single-phase AC generators, mechanically coupled to a common shaft. Rotary converters were also used, especially where the desired output was DC current from an AC source.

Static

In the 1920s, DC was derived using electronic valves. In modern systems, high-voltage DC "back-to-back" stations are used instead of mechanical equipment to convert between different frequencies and phases of AC power and solid-state thyristor rectifier systems are used for conversion from AC power to DC traction power.

Location

Traction current converter plants are either decentralized or centralized.
Central traction current converter plants are generally found in Germany, Austria and Switzerland, while decentralized traction current converter plants are generally found in Norway, Sweden and the German states of Mecklenburg-Vorpommern and Brandenburg as well as parts of Great Britain. A List of railway electrification systems provides further detail.