Located outside of the generating unit is a switchyard where the station transformer increases the voltage of the unit output to the voltage of the transmission system. The switchyard also contains switches, breakers, busbars, and other protective equipment that configure the flow of power away from the generating unit and provide protection for both the unit and transmission grid. The power flows then from the switchyard through one or more transmission lines.
Transmission substations connect different transmission lines. The transmission substation contains switches, breakers and other protective equipment, monitoring and metering equipment, and, if necessary, transformers to adjust voltage between different incoming power lines. Power leaves the transmission substation through the transmission lines, which connect to the distribution system at the distribution substation.