Electrical substations perform different roles depending on their position in the power system.
Transmission substations operate at high voltage levels. Distribution substations operate at medium or low voltage levels.
Transmission Substation
A transmission substation connects high voltage transmission lines. Typical voltage levels include 132 kV, 220 kV, and 400 kV.
Its main functions include:
Voltage transformation between transmission levels
Switching transmission lines
Maintaining system stability
Equipment in transmission substations usually includes large power transformers, gas insulated switchgear, and advanced protection systems.
Distribution Substation
A distribution substation reduces voltage from transmission levels to distribution levels. Typical output voltages include 33 kV, 13.8 kV, or 11 kV.
Distribution substations supply electricity to cities, industrial areas, and residential neighborhoods.
Equipment in distribution substations includes distribution transformers, feeder breakers, and protection relays.
The main difference between both types lies in voltage level and system function.