A substation is a part of an electrical generation, transmission and distribution system. The assembly of apparatus used to change some characteristics (e.g. voltage, frequency, p.f., A.C. to D.C. etc.) of an electrical supply is called a substation.

Some of the main operations of substations are:

To receive energy transmitted at high voltage from the generating stations.
To decrease the voltage to a value appropriate for local distribution.
To provide switching facilities.