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Glossary of Electric Terms



Aerial cable – insulated cable installed on poles via a steel messenger cable for the purpose of delivering power at distribution voltage levels.

Ampere (amp) – a unit of measure for the flow of electricity. Often referred to as load.

Area substation – a substation that reduces voltage from transmission levels to distribution levels. e.g. from 138,000 volts to 13,000 volts.

Auto-loop – an overhead distribution system comprised of wire, transformers, switches, and vacuum reclosers installed on poles. An auto-loop will automatically isolate a fault on open wire, reducing the amount of customers interrupted.



Breaker – a switch that automatically disconnects power to a circuit in the event of an electrical fault condition. May also be operated manually to disconnect power.

Burnout – an electrical fault caused by the breakdown of the insulation on cable.

Bus – a large rigid conductor, usually constructed of copper, used for delivering power.

Bushing – an insulated fitting for carrying a conductor through a metal enclosure of electrical equipment such as transformers or capacitors.



Cable – an insulated conductor that can be installed either overhead or underground.

Cable Limiter – a current limiting device that limits the extent of secondary cable damage due to a cable fault or burnout. Limiters are used in underground secondary network systems.

Capacitor – a device which helps to improve the efficiency of transmission and distribution circuits by reducing power losses.

Commodity Cost – The cost of the natural gas or electricity commodity and related charges to deliver it to the marketplace.

Conductor – wire, cable, or bus that serves as a path for current to flow.

Cutout – the opening of a switching device to de-energize cable or equipment.



Demand – the total amount of power required at any given time.

Direct Current (DC) – a fixed polarity power supply with a positive and negative terminal that remains constant.

Distribution – the system used to deliver power from a substation to the customer’s premises.

Distribution Feeder – an individual circuit used to deliver power from a breaker position at a substation to the transformers or switching devices at the load area.



Energize – the act of connecting a piece of equipment to a source of electrical potential.



Fault – the initiating condition that results in a feeder breaker tripout caused by an insulation breakdown. A permanent or transient condition which causes equipment not to perform in its required manner.

Fault locating – the process of determining the failure point on a feeder.

Feeder – see distribution feeder and transmission feeder.

Fused cutout – a pole mounted switch & fuse assembly used to protect the branch of an overhead feeder.



Ground – the conductive body, usually earth, to which an electric potential is referenced.
– (as a verb) the establishment of a connection, whether by intent or accident, of an electric circuit or equipment to referenced ground. The application of grounds on de-energized equipment is used for worker protection to prevent the accidental energization of electrical conductors or equipment.



High-pot – a high voltage DC test of the integrity of the insulation of cable or equipment.

High Tension Vault – an installation that is supplied by high voltage at the 33, 27, 13 or 4kV level whereby the equipment beyond the high voltage terminations is customer owned & maintained.

High Voltage Tracing Current – a high voltage DC output applied to a feeder for the purpose of locating a fault.



Insulation – the protective material covering electrical cable or equipment.

Isolated – disconnected from the system by opening of switches, disconnecting devices, or removal of equipment.

Isolated Network – a secondary distribution network isolated from the normal secondary network grid and comprises at least 2 primary feeders supplying underground transformers that have interconnected secondary systems.

In Service – a term used to indicate equipment is connected to the system and fulfilling its designated function.



Joint – a joining or splicing of conductors for the purpose of continuity of cable sections.



Kilovolt – abv. kV 1000 volts.

Kilowatt – abv. kW 1000 watts.



Live End Cap (LEC) – a sealed housing installed on a primary cable end for the purpose of allowing the cable to be energized after removing defective cable or equipment beyond the live end cap point.

Life Sustaining Equipment (LSE) – any electrically operated equipment that is essential to sustaining the life of the individual user of that equipment. (e.g. iron lung)

Load – the power consumed by customers and equipment.

Load Shedding – the process of disconnecting load from the system for the purpose of protecting the integrity of the system.

Local Grounds – the protective grounds applied to equipment to be worked upon.

Low Voltage Condition – any voltage that is below the specified parameters for the existing system condition.

Low Voltage Tracing Current – a low voltage DC current applied to a feeder for the purpose of making a positive identification of cable or equipment at the working point.



Open-Auto (O/A) – a trip out of a feeder breaker in a substation due to a fault condition or overload on the feeder cable or equipment.

Overload – a condition wherein electrical equipment is carrying current in excess of its applicable rating.



Partial Outage – an interruption of service to a portion of a facility or area where the customer(s) is not completely without power.



Radial – a distribution system with one source of supply only. Also referred to as non-network.



Secondary Network – a system of distribution feeders connected on their secondary side (120/208V). This system allows for a multiple power supply to any given point connected to the secondary grid.

Splice – the process of joining conductors for the purpose of continuity of cable sections.



Transformer – an electrical device used for converting voltage or current levels by either stepping up or down the level.

Transmission Feeder – the circuit used to deliver power from a generating station or switching station to the distribution area substation.



Unit Substation – comprises a large step-down transformer that transforms voltage levels from 33kV, 27kV, or 13kV to the 4kV level for the purpose of distribution on primarily overhead wires to supply mostly residential load at the 120/28V or 120/240V level.



Vacuum Recloser – a pole mounted automatic switch used in auto-loops for the purpose of isolating and restoring power due to a feeder outage or overhead wire fault.

Vault – an enclosure occupied by electrical distribution equipment.

Voltage Reduction – reducing voltage supplied to an area to reduce the demand on the system.