A railway electrification system supplies electrical energy to railway locomotives and multiple units so that they can operate without having an on-board prime mover. There are several different electrification systems in use throughout the world. Railway electrification has many advantages but requires heavy capital expenditure for installation.

The main advantage of electric traction is a higher power-to-weight ratio than forms of traction such as diesel or steam that generate power on board. Electricity enables faster acceleration and higher tractive effort on steep grades. On locomotives equipped with regenerative braking, descending grades requires very little use of air brakes as the locomotive's traction motors become generators sending current back into the supply system and/or on-board resistors, which convert the excess energy to heat.

Other advantages include the lack of exhaust fumes at point of use, less noise and lower maintenance requirements of the traction units. ...more

1500 v dc.