Substation

An aerial substation

A substation is the part of an electricity transmission and distribution system that reduces voltage from transmission voltages of up to 330kV. This may take place in several stages and at several substations in sequence, progressively reducing the voltage.

The word substation comes from the days before the distribution system became a grid. The first substations were connected to only one power station, and were entirely dependent on it, hence the name.

Substations may be on the surface in fenced enclosures, underground, located in special-purpose buildings, located on power poles (aerial substations) or located in the service areas of the buildings they service. Substations located within the buildings they serve are particularly a feature of high-rise buildings.

It is more efficient to transmit electricity over long distances at very high voltages; the function of the substation is to reduce the voltage to a more manageable, and for domestic use, safer level.