This is a list of the power supply systems that are, or have been, used for railway electrification. Note that the voltages are nominal and vary depending on load and distance from the substation. many trams and trains use on-board solid-state electronics to convert these supplies to run three-phase AC traction motors. Tram electrification systems are listed here.

Key to the tables below

Systems using standard voltages

Voltages are defined by two standards: BS EN 50163 and IEC 60850.

Overhead systems

600 V DC

750 V DC

1,200 V DC

1,500 V DC

3 kV DC

15 kV AC, 16 2/3 Hz / 16.7 Hz

25 kV AC, 50 Hz

25 kV AC, 60 Hz

Conductor rail systems

600 V DC conductor

All systems are third rail unless stated otherwise. Used by some older metros.

750 V DC conductor

Conductor rail systems have been separated into tables based on whether they are top, side or bottom contact. Used by most metros outside Asia and the former Eastern bloc.

Bottom contact

Side contact

Top contact

Mixed

1,200 V DC conductor

All systems are third rail and side contact unless stated otherwise.

1,500 V DC conductor

All systems are third rail unless stated otherwise.

Systems using non-standard voltages

Overhead systems

DC voltage

AC voltage

Three-phase AC voltage

Two wires

Three wires

Conductor rail systems (DC voltage)

Conductor rail systems have been separated into tables based on whether they are top, side or bottom contact.

Top contact systems

Side contact systems

All third rail unless otherwise stated.

Bottom contact systems

All third rail unless otherwise stated.

Conductor rail systems (AC voltage)

All systems are 3-phase unless otherwise noted.

Special or unusual types

DC, plough collection from conductors in conduit below track

DC, one ground-level conductor

DC, two-wire

DC, power from running rails

DC, four-rail

Footnotes