Common Terms Used in the Utility Industry

Circuit: An overhead line on poles or underground cable that carries power from substation to customers. Circuit and distribution lines are terms used interchangeably.
Circuit Breaker: An electrical device which interrupts the current flow to a circuit when it exceeds a predetermined value. A circuit breaker is used to de-energize a circuit and can be set or programmed with various protection schemes to minimize damage to lines and equipment. Circuit breakers are designed to be re-closed after a current interruption.
Distribution Line: A distribution line is a medium- voltage (2,001 volts to 46,000 volts) overhead line that carries power from the substation to customer service areas. Some distribution lines are underground cables.
Fuse: An electrical device that interrupts the current flow to a circuit when it exceeds a predetermined value. A fuse is used to de-energize a circuit to minimize damage to lines and equipment. Fuses can interrupt current only one time and must be replaced in order to energize the circuit it protects.
Insulator: An insulator is a device made of special material that supports and separates energized lines and equipment from non-energized parts to prevent unwanted current flow. Insulators support overhead lines or cables on utility poles. An insulator may also support energized conductors and equipment in cabinets and inside substations.
Kilowatt (KW): An electrical quantity of energy that represents one thousand watts of power.
Megawatt (MW): An electrical quantity of energy that represents one million watts of power.
Meter: A device that plugs into a meter socket to measure the consumption of energy by the customer in kilowatt-hours.
Phase: Most power generation is three-phase and therefore needs three individual wires for each phase to convey it over distance to the end user.
Power Plant: A facility, which converts fuel such as gas, coal, oil, nuclear or wind into an electrical energy (power).
Service Line: A service line is a lower-voltage (up to 2000 volts) overhead conductor that carries power from the step-down transformer on the distribution line to a small-industrial, commercial or residential customer. This overhead conductor is the last connection from the utility to the meter on the customer’s premises. Service lines could be an underground cable.
Substation: A power distribution center that steps down transmission voltages (46,001 volts to 750,000 volts) to a primary distribution voltage (2,001 volts to 46,000 volts) with power transformers. Most circuits (distribution lines) radiate from this center toward customers.
Transformer: A device that steps voltage down from a higher voltage or up to a higher voltage depending on use (i.e. steps the voltage down from a primary distribution voltage of 7200 volts to 120/240 volts for residential use).
Transmission Line: A transmission line is a bare, uninsulated high-voltage (46,001 volts to 750,000 volts) overhead line that carries power from power plants to substations or power distribution centers. Some transmission lines are underground cables
Watt: The basic unit for measuring energy or power in the utility industry.