Pathway of Power: Transmission System

Before electricity can be delivered to consumers, it must travel through a distribution substation. Distribution substations, located near where electricity will be used, monitor and adjust circuits within the system.

Substations are fenced-in yards containing switches, transformers and other electrical equipment. The main purpose of distribution substations is to lower transmission voltage to 24,900 volts or less to feed the distribution system.

Relays are mechanical switches that will cause a substation breaker to shut off power if it senses a higher than normal current. Within the substation, rigid tubular or rectangular bars, called busbars, or buses, are used as conductors to feed power to two or more circuits. Circuit breakers automatically disconnect power to a circuit in the event of a failure or interruption in an electric line (see diagram #4).