What is a Traction Substation? Powering the Railway Network

A Traction Substation (TPSS), or Traction Power Substation, is an electrical substation that converts electric power from the commercial utility grid to a form suitable for supplying electric trains, trams, or metros.
It is the bridge between the national power grid and the Overhead Catenary System or Third Rail. Without these substations, electric trains would have no power to move.

Functions of a Traction Substation

The main job of a TPSS is to transform voltage and, in many cases, convert the current type.
Voltage Transformation: Steps down the high voltage from the national grid (e.g., 132kV or 33kV) to the railway voltage (e.g., 25kV AC or 750V DC).
Rectification (AC to DC): For metros and trams that run on Direct Current (DC), the substation uses “Rectifiers” to convert Alternating Current (AC) from the grid into DC.
Protection: It houses circuit breakers to protect the railway network from overloads and short circuits.

AC vs. DC Substations

Different railway types require different substation configurations.

Feeder Stations

From the substation, the power is sent through “Feeder Cables” to the trackside. In complex networks, Auto-Transformer Stations are placed along the line to boost the voltage and prevent power loss over long distances.