Download common electricity terms

P. O. Box 270
Hartford, CT 06141-0270
107 Selden Street
Berlin, CT 06037
(860)-665-5000
www.nu.com
COMMON ELECTRICITY TERMS
DIRECT CURRENT (DC): Electricity that flows
continuously in one direction. A battery produces DC power.
ALTERNATING CURRENT (AC): An electric current
which reverses its direction of flow periodically. Utilities
supply this type of current to homes and businesses.
DISTRIBUTION LINE: Any line operating at less than
69,000 volts.
AMPERE (AMP): A unit measure for the flow (current) of
electricity. A typical home service capability (i.e. size) is 100
amps; 200 amps is required for homes with electric heat.
ENTRANCE CABLE OR SERVICE ENTRANCE
CONDUCTORS: The cable running down the side of the
customer’s house into the meter. This cable is owned by the
customer and its maintenance is the customer’s responsibility.
Work on this cable should only be performed by a licensed
electrician.
ARCING/GAPPING: The flow of electricity through the air
from a conductor to another object that conducts electricity.
Produces visible flashes, flames and a crackling sound.
BUSBAR (BUS): A rigid, large conductor (a metal bar or
tube) usually used in substations. Provides a quick, convenient
means of rearranging circuit connections to keep power
flowing or to restore power in case of equipment damage.
FAULT: A failure or interruption in an electrical circuit.
FEEDER: A distribution circuit (less than 69,000 volts)
carrying power from a substation.
BUSHING: An insulated fitting for carrying the conductor
through the metal enclosure of electrical equipment such as
transformers or capacitors.
FEEDER LOCKOUT: Main circuit is interrupted at the
substation by automatic protective devices and cannot be
restored until crews investigate. Usually indicates a serious
problem on the circuit, either a broken conductor or other
equipment failure.
CABLE: A fully insulated conductor that can be installed
underground or overhead.
FUSE/FUSED CUTOUT: Protects the distribution line from
overloading. Acts by melting during overloading or faults,
breaking the circuit. Is similar to fuses found in fuse boxes in
homes.
CABLE TERMINATOR: A device used at the junction of
an underground cable and an overhead line to prevent moisture
from entering the cable insulation.
CAPACITOR: Installed in substations and on poles. A
device which helps to improve the efficiency of transmission
and distribution lines to carry electrical power by reducing
energy losses.
GROUND: When one or more conductors contact the earth,
causing the electricity to flow out of the circuit into the earth.
INSULATION: The protective material covering the electric
wire. Rubber or polyethylene are commonly used.
CIRCUIT: A continuous system of conductors providing a
path for electricity.
INSULATOR: The porcelain support used to insulate the
conductors from the pole or tower.
CIRCUIT BREAKER: Located in substations, this switch
automatically disconnects power to the circuit in the event of a
fault condition. Performs the same function as a circuit
breaker in a home.
KILOVOLT (kV): 1,000 volts.
KILOWATT (kW): 1,000 watts.
CONDUCTOR: A wire, cable, busbar, rod or tube which
serves as a path for electricity flow. The most common
conductor is the overhead wire.
KILOWATT-HOUR (kWh): A basic unit of electricity
equal to one kilowatt or 1,000 watts of power used for one
hour.
CONVEX: The Connecticut Valley Electric Exchange,
located in Newington, Connecticut, which plans and
coordinates the dispatch of bulk electric power in Connecticut
and western Massachusetts. It is one of five satellite stations
of the New England Power Exchange (NEPEX) which
dispatches virtually all power across New England.
LIGHTNING ARRESTER: Protects lines, transformers and
equipment from lightning surges by carrying the charge to
ground. Lightning arresters serve the same purpose on a line
as a safety valve on a steam boiler.
LINE CREW: Teams of highly trained workers who service
and repair lines and equipment.
CUTOUT: See FUSE.
LOAD: Amount of power delivered as required at any point
or points in the system. Load is created by the power demands
of customers’ equipment.
DEMAND: The total amount of electricity required at any
given time by a utility’s customers (also see peak demand).
1
SHORT CIRCUIT: An accidentally established connection
between two points in an electric circuit, such as when a tree
limb, or an animal bridges the gap between two conductors.
This will cause heavy currents to flow in the line (overload)
and result in melting of line fuses and operation of protective
devices such as reclosers and circuit breakers.
MESSENGER CABLE: A strong, non-energized, bare metal
wire used to support energized cable.
NETWORK: A system of interconnected transmission and
distribution lines. Usually installed in urban areas. Makes it
possible to restore power quickly to customers by switching
them to another circuit.
SINGLE PHASE LINE: A conductor installation carrying
electrical loads capable of serving the needs of residential
customers, small commercial customers and streetlights.
Carries a relatively light load as compared to heavy duty three
phase.
OPEN CIRCUIT: A condition produced when a circuit
opens either intentionally with a switch or as a result of a fault.
OVERLOAD: A flow of electricity into conductors or
devices exceeding their capacity.
SUBSTATION (S/S): A small building or fenced-in yard
containing switches, transformers and other equipment and
structures. Adjustments of voltage, monitoring of circuits and
other service functions take place in this installation.
PEAK DEMAND: The maximum amount of electricity
required to supply customers.
POLE-MOUNTED TRANSFORMER: The transformer
mounted on a pole which steps down primary distribution
voltage (normal range: 4,160 to 23,000 volts) for use by
individual customers. A home typically uses a secondary
voltage of 120/240 volts.
SWITCHING STATION: A type of substation where
connections are made between several distribution or
transmission lines. Voltage is not changed.
TAP: A connection between conductors or between a
conductor and certain equipment such as transformers.
POTHEAD (TERMINATION): A flared pot-shaped
insulated fitting used to connect underground cables to
overhead lines.
TAP CHANGER: A device to adjust the voltage-changing
capability of a transformer or a voltage regulator.
PRIMARY TAP: A short wire connecting primary
conductors and a transformer.
THREE PHASE LINE: A conductor installation capable of
carrying heavy loads of electricity.
PRIMARY CIRCUIT: The distribution circuit (less than
69,000 volts) on the high voltage side of a transformer.
TRANSMISSION LINE: Any line operating at 69,000 or
more volts.
RECLOSER: A switch which functions like a circuit breaker,
protecting primary circuits from fault conditions. A recloser
will automatically restore the circuit in the event of a
temporary fault. Temporary faults can be caused by such
things as a tree branch falling onto the lines and then to the
ground.
TRANSFORMER: A device used to transform voltage levels
to facilitate the transfer of power from the generating plant to
the customer. A step-up transformer increases the voltage; a
step-down transformer decreases it.
TREE CREWS: Teams of workers skilled in trimming and
removing trees in close proximity to energized power lines.
REGULATOR: A type of transformer which maintains
constant voltage on main distribution lines (feeders) as
customer demand for electricity changes. Installed in
substations and on poles.
TREE WIRE: A covered conductor used in heavily treed
areas to provide some protection from momentary tree limb
contact.
RELAYS: Sensitive instruments which trigger switches to
interrupt circuits when a fault is detected.
UNDERGROUND: Electrical facilities installed below the
surface of the earth.
RISER: The underground-to-overhead cable connection
enclosed in a pipe and attached to the side of the pole.
VOLTAGE: A measure of the push or force which transmits
electricity.
SECONDARY CIRCUIT: The distribution circuit on the
low voltage side of a transformer (usually 120/240 volts).
WATT: A measure of the work electricity can do.
SECTIONALIZER: Similar to a recloser, but only opens
when line is "dead" due to the operation of a recloser or
breaker upstream. Serves to isolate the section of the circuit in
fault and allow the remainder of the circuit to be re-energized.
SERVICE DROP: The lines running from the pole to the
customer’s house. Usually made up of two 120-volt lines and
a neutral line, from which the customer can obtain either 120
or 240 volts of power. When these lines are insulated and
twisted together the installation is called triplex cable.
2