The high voltage supply is given to the primary of the transformer through circuit breaker. From the bus-bar various feeders emerge out. The panel for each feeder consists of an isolator switch and circuit breaker. In addition to isolator and circuit breaker, the panel is provided with the measuring instruments. As regards protection of feeders usually reverse power relay is employed. A substation which is used for all voltage levels between 55 KV to 765 KV is called outdoor substation. Such type of substation requires less time for construction but uses more space. The outdoor substations are mainly classified into two types, namely pole-mounted substation and foundation-mounted substations.
This type of substation gets the power supply from a near producing facility. It uses a large power transformer for enhancing the voltage level for transmitting to the remote locations. In is substation, the power transmission can be done by using a transmission bus to transmission lines.
Distribution type substations are placed where the main voltage distributions are stepped-down to supply voltages to the consumers using a distribution network. The voltage of any two phases will be 400 volts, and the voltage between neutral and any phase will be 230volts.
Installation of a substation in urban centers requires large space, but generally, they don’t have a place to install the substation. To overcome this problem, installing the substation underground decreases requirement of space and the surface area can also be used for other constructions like buildings, shopping malls, etc.
The switchyard is the mediator among the transmission as well as generation, and equal voltage can be maintained in the switchyard. The main purpose of this is to supply the generated energy from the power plant at the particular level of voltage to the nearby transmission line or power grid.