Northeast Power - Glossary of Terms

Glossary of Electrical Terms

A.B.C.D.E.F.G.H.I.J.K.L.M.N.O.P.Q.R.S.T.U.V.W.X.Y.Z

Alternating Current (ac)
	Current that flows in a circuit in a positive direction and then reverses itself to flow in a negative direction.
Alternative Energy Sources
	Also known as supplemental energy sources; methods of producing energy other than those commonly in use. Solar, wind, tidal, geothermal, fusion and synfuels are some alternative energy sources.
Amp (A)
	The unit of measurement of electric current.

Base Load
	The minimum amount of electric power delivered or required over a given period, at a constant rate.
Blackout
	Complete loss of power being supplied by the electric cooperative.
Brownout
	A temporary reduction in voltage below the normal minimum level specified by the system.

Capacity
	The quantity of electricity that can be delivered under certain conditions.
Charge
	The quantity of unbalanced electricity in a body (either positive or negative) and construed as an excess or deficiency of electrons.
Circuit
	The complete or partial path of an electric current, including the generating apparatus, intervening resistors, or capacitors.
Conductors
	Materials that have many free electrons and are good transporters for the flow of electric current.
Conservation
	Reducing the amount of energy consumed by a customer for a specific end-use. Behavior changes, such as thermostat setback, are included in this definition. This definition does not include changing the timing of energy use, switching to other fuel sources or increasing off-peak usage, even though these actions may make more efficient use of generation or distribution facilities.
Cooperative (Co-op)
	A nonprofit utility owned by it's members. Rural electric cooperatives generate and purchase wholesale power, own or arrange for the transmission of that power and then distribute the power to serve the demand of rural customers. Co-ops typically become involved in ancillary services such as energy conservation, load management and other demand-side management programs to serve their customers at least cost.
Current (I)
	The flow of free electrons in one general direction, measured in units of amps.

Direct Current (dc)
	Current that flows continually in one direction.
Distribution substation
	You see them around towns and cities. They are those small fenced-in areas that have electric lines coming in and going out. Inside these fenced-in areas are transformers that reduce voltage to a lower level so the power can be sent out on distribution lines to the surrounding community.
Distribution System
	Includes main or primary lines and lower voltage, or secondary lines that deliver electricity through overhead or underground wires to homes and businesses. You see these lines every day on poles alongside roads and streets.

Electricity
	The motion of electrons through a conductor.
Energy
	The amount of electric work (real power) consumed or utilized in an hour. The unit of measure is the watt-hour.
Energy conversion factors
	Chart available here.

Forced Outage
	The unplanned shutdown of a generating unit, transmission line or other facility.
Frequency (f)
	The number of complete cycles made per second, measured in units of hertz.
Fuse
	A protective device, used in an electric circuit, containing a conductor that melts under heat produced by an excess current, thereby opening the circuit.

Generating capacity
	The maximum amounts of electricity a given power plant is able to produce, usually expressed in megawatts.
Generator
	A machine that converts mechanical energy into electricity to serve as a power source for other machines. Electric generators found in power plants use water turbines, combustion engines, windmills, or other sources of mechanical energy to spin wire coils in strong magnetic fields, inducing an electric potential in the coils.
Green power
	Electricity produced using wind, sun, or steam escaping from the earth. By definition, federal regulation also includes power generated by sources such as gas produced by decaying garbage in landfills. Also includes energy produced by biomass, hydro and geothermal.
Grid
	A system of electrical distribution serving a large area, especially by means of high-tension lines.
Ground
	A conducting connection between an electric circuit or equipment and the earth or some other conducting body.

Hertz (Hz)
	Units of frequency (equal to 1 cycle per second.)

Insulators
	Materials that have hardly any free electrons and inhibit or restrict the flow of electric current.

Kilowatt (kW)
	Unit of power equal to 1,000 watts
Kilowatt hour (kWh)
	A unit of energy, equivalent to the energy transferred or expended in one hour by one kilowatt of power; approximately 1.34 horsepower-hours.

Load
	The amount of electric power delivered or required at any specified point on a system.

Megawatt (MW)
	A unit of power equal to one million watts.
Minimum generation
	The lowest level to run a generator so you can meet peak power needs.
Must-run units
	A generating unit that must be online or on the grid to ensure the stability of the system, even if it costs more to run than other units that may be available on the system or in the power pool.

Net capacity
	The maximum capacity a power plant can sustain over a period of time, less the capacity used to supply its own needs such as motors and other equipment essential to its operation. This capacity may be modified to account for seasonal or ambient limitations.

Off-peak
	Is a utility period of lower energy demand.
Off-peak power
	Electricity generated during periods of typically low demand, such as early morning hours, Sundays and holidays.
Ohm (Ω)
	The unit of measurement of resistance in an electric circuit.

Peak demand
	The maximum amount of electricity used by a utility customer at any time during the year.
Power (P)
	The rate of flow of energy past a given point.
Power capacity
	The amount of power which can be generated. for example, if an electric generator has a power capacity of 25,000 kilowatts; it can deliver energy at the maximum rate of 25,000 kilowatt-hours per hour.
Power Factor (p.f.)
	The ratio of real power to reactive power.
Power plant
	Electricity starts here, produced by spinning generators that are driven by water, a diesel engine, or a natural gas or steam turbine. Steam is made by burning coal, oil or natural gas or by a nuclear reactor. When needed, plants bring extra power.

Reactive Power
	The portion of power flow due to stored energy, which returns to the source in each cycle.
Real Power
	The portion of power flow that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction.
Reserve
	The generating capability that an electric utility needs, in addition to the highest level of user demand, to meet its needs.
Resistance (R)
	The electrical "friction" that must be overcome through a device in order for current to flow when voltage is applied.

Single-phase power
	The ordinary electric service usually provided to households (120v, two-wire or 120v / 240v three-wire). Lights and small appliances operate at 120v. Major units such as electric ranges, clothes driers, heating and central air conditioning, operate at 240 volts.
Static Electricity
	Electric charge that has accumulated on an object. Static electricity is often created when two objects that are not good electrical conductors are rubbed together, and electrons from one of the objects rub off onto the other.
Substation
	A facility that switches, steps down or regulates electricity. Substations also serve as control or transfer points in an electric system. Their purpose is to route and control electricity, alter voltage levels and serve as delivery points.
Switch
	A device for turning on or off or directing an electric current of for making or breaking a circuit.

Three-phase power
	Electric power supplied using alternating current with three branches, differing by one-third of a cycle (120°) in phase, such that when one branch is at full value the others are at half value, but glowing in the opposite direction. this type of power is generally required for operating heavy equipment.
Transformer
	A device that raises or lowers the voltage or force of alternating current electricity.
Transmission substation
	These facilities look like giant erector sets connected to wires from the power plant. here large transformers increase voltage from thousands to hundreds of thousands of volts so the power can be sent over long distances.

Var (Q)
	The unit of reactive power in an electric circuit.
Volt (V) *
	The unit of measurement of voltage in an electric circuit.
Voltage (E)
	The electric force of work required to move current through an electric circuit, measured in units of volt.
Voltampere (VA)
	The unit of both real and reactive power in an electric circuit.

Watt (W) *
	The unit of real power in an electric circuit.

* The difference between a watt and a volt can be visualized by imagining water flowing through a hose into a bucket. Voltage is similar to the water pressure in the hose and wattage is the amount of water going into the bucket.