Electricity Glossary

A

a - amperes; amps; The unit of measurement of electrical current produced in a circuit by 1 volt acting through a resistance of 1 ohm

ac - abbreviation for alternating current: an electric current in which electrons repeatedly change direction. see alternating current.

accuracy - the degree of uncertainty for which a measured value agrees the ideal value.

acid rain - also called acid precipitation or acid deposition, acid rain is precipitation containing harmful amounts of nitric and sulfuric acids formed primarily by nitrogen oxides and sulfur oxides released into the atmosphere when fossil fuels are burned. It can be wet precipitation (rain, snow, or fog) or dry precipitation (absorbed gaseous and particulate matter, aerosol particles or dust). Acid rain has a pH below 5.6. Normal rain has a pH of about 5.6, which is slightly acidic. The term pH is a measure of acidity or alkalinity and ranges from 0 to 14. A pH measurement of 7 is regarded as neutral. Measurements below 7 indicate increased acidity, while those above indicate increased alkalinity.

active power - see real power

actual peak load reductions - The actual reduction in annual peak load (measured in kilowatts) achieved by consumers that participate in a utility DSM program. It reflects the real changes in the demand for electricity resulting from a utility DSM program that is in effect at the same time the utility experiences its annual peak load, as opposed to the installed peak load reduction capability (i.e., Potential Peak Load Reduction). It should account for the regular cycling of energy efficient units during the period of annual peak load.

affiliated retail electric provider - a Retail Electric Provider (REP) that is owned, and now independently operated, by the original electric utility for that area.

aggregator - a company that is registered with the Public Utility Commission that joins two or more customers to purchase electricity from retail electric providers in mass.

alarm - a signal for attracting attention to some abnormal event.

alkaline battery - a long life battery. The life of a battery is partly controlled by size (the bigger the battery, the longer it lasts) and partly by the materials used to make it. An alkaline battery uses a special (alkaline) paste to ensure longer life.

all-or-nothing relay - an electrical relay which is intended to be energized by a quantity, whose value is either higher than that at which it picks up or lower than that at which it drops out.

alternating current - an electrical current which reverses direction repeatedly due to a change in voltage which occurs at the same frequency. Often abbreviated AC or ac.

alternator - an electric generator designed to produce alternating current. Usually consists of rotating parts which created the changing magnetic field to produce the alternating current.

American National Standards Institute - a private organization that coordinates and/or approves some US standards, particularly those related to the electrical industry. Abbreviated ANSI.

American Wire Gauge - a standard measure which represents the size of wire. The larger the number, the smaller the wire. Abbreviated AWG.

ammeter - a meter for measuring electric current. It is often part of a multi-meter.

ampacity - the maximum continuous current that a conductor can carry without overheating above its temperature rating.

Ampere - electric current produced by one volt applied across a resistance of one ohm.  It is also equal to the flow of one coulomb per second. It is named after French physicist Andre M. Ampère 1836.

ambient temperature - the surrounding temperature.

Ampere-hour - the flow of electricity equal to one ampere for one hour. Commonly used to rate the capacity of batteries.

Ampere-hour capacity (storage battery) - the number of ampere-hours that can be delivered under specified conditions of temperature, rate of discharge, and final voltage.

Ampere-hour meter - an electric meter that measures and registers the integral, with respect to time, of the current of a circuit in which it is connected.

analog - a measuring or display methodology which uses continuously varying physical parameters. In contrast, digital represents information in discrete binary form using only zeros and ones.

ancillary services - ancillary services are those services necessary to support the transmission of energy from resources to loads while maintaining reliable operation of the Transmission Provider’s transmission system in accordance with Good Utility Practice.

apparent power (volt-amps) - the mathematical product of voltage and current on ac systems. Since voltage and current may not be in phase on ac systems, the apparent power thus calculated may not equal the real power, but may actually exceed it. Reactive loads (inductance and/or capacitance) on ac systems will cause the apparent power to be larger than the real power.

anode - 1) The positive electrode that emits positive ions and attracts negative ions, within a voltaic cell or other such device. 2) The positive pole of a battery.

ANSI - American National Standards Institute. ANSI is located at 1430 Broadway, New York, NY 10018.

arc - a discharge of electricity through air or a gas.

array - for photovoltaic systems, a number of photovoltaic modules connected together to provide a single electrical output.

attractive force - the force that pulls together two opposite poles of a magnet (i.e. a north pole attracts a south pole) or two opposite charges in electricity ( a positive charge attracts a negative charge in static electricity).

asset - items of value owned by or owed to a business.

average revenue per Kilowatt-hour - the average revenue per kilowatt-hour of electricity sold by sector (residential, commercial, industrial, or other) and geographic area (State, Census division, and National), is calculated by dividing the total monthly revenue by the corresponding total monthly sales for each sector and geographic area.

AWG - abbreviation for American Wire Gauge.

B

balanced load - refers to an equal loading of the phases in a polyhphase system (current and phase angle).

bank - a group of electrical devices, usually transformers or capacitors, connected in a way to increase capacity.

baseload - the minimum amount of electric power delivered or required over a given period of time at a steady rate.

battery - a group of two or more cells connected together to provide electrical current. Sometimes also used to describe a single cell which converts chemical energy to electrical current. A battery works by changing chemical energy into electrical energy. To do this two materials, such as carbon and zinc in the case of a dry cell, are connected by a chemical paste. The carbon is in the shape of a rod and is placed in the centre of the cell. The zinc makes up the metal case. The paste fills up the rest of the cell.

battery cycle life - the number of discharge and recharge cycles that a battery can undergo before degrading below its capacity rating.

battery self-discharge - the gradual loss of chemical energy in a battery that is not connected to any electrical load.

battery tray - a contained with a base and walls for holding several cells or batteries.

bias Current - the current used as a bias quantity in a biased relay.

biased relay - a relay in which the characteristics are modified by the introduction of some quantity, and which is usually in opposition to the actuating quantity.

black start - refers to certain electric utility generating units that can start upon demand without any outside source of electric power.  These are often combustion turbines that have stationary battery banks to provide backup power to energize all the controls and auxiliaries necessary to get the unit up and running.  In the event of an large area-wide blackout, these units are critical to restoring the utility grid.   Most utility generating units do not have black start capability.

boiler - a device for generating steam for power, processing, or heating purposes or for producing hot water for heating purposes or hot water supply. Heat from an external combustion source is transmitted to a fluid contained within the tubes in the boiler shell. This fluid is delivered to an end-use at a desired pressure, temperature, and quality.

bonding - an electrical conducting path formed by the permanent joining of metallic parts. Intended to assure electrical continuity and the capability to safely conduct any likely current. Similar to bonding jumper or bonding conductor.

branch circuit - the conductors between the last overcurrent protective device and the outlets or loads.

bulb - the outer enclosure of a light source; usually glass or quartz. Also a device for converting electricity into light

bundle - multiple cables used to form one phase of an overhead circuit.

burden - load imposed by an electronic or electrical device on the measured input circuit, expressed in volt-amps.

bus - a conductor, which may be a solid bar or pipe, normally made of aluminum or copper, used to connect one or more circuits to a common interface. An example would be the bus used to connect a substation transformer to the outgoing circuits.

capacitor voltage transformer - a voltage transformer that uses capacitors to obtain a voltage divider effect. It is utilized at EHV voltages instead of an electromagnetic VT for cost and size purposes.

cell - a single device which converts chemical energy into electrical current. Sometimes also referred to as a battery.

charge - the build up of electricity on the surface of an insulator.
People use the word charge when talking about static electricity. A surface of an insulator can have a positive charge or a negative charge.
When two substances rub together the positive charges can be rubbed off onto one surface and the negative ones onto the other. Each surface now has an opposite charge and so they will attract each other. Sometimes the charges will jump the gap and then a spark will occur.

charge rate (battery) - the rate at which a battery or cell is recharged. Can be expressed as a ratio of battery capacity to current flow.

charge-retention (battery) - the tendency of a charges cell or battery to resist self-discharge.

Circuit - a conductor or a system of conductors through which electric current flows.

circuit breaker - a device designed to open a circuit either by manual action or by automatic action when current exceeds a value longer than permitted. A circuit breaker can provide overcurrent protection.

circuit voltage - the greatest root-mean-square (effective) difference of potential between any two conductors of the circuit.

clearing time - The total time needed for a protective device such as a fuse or circuit breaker to clear a fault.

conduit - a duct designed to contain underground cables, conductors, wires.

conductor - usually a metallic substance capable of transmitting electricity with little resistance. The best conductor at normal temperature ranges is silver. The most common is copper. Some other recently discovered substances called super conductors actually have zero resistance at extremely low temperatures.

continuous load - a sustained electrical load current for three hours or more.

control area - an electric power system or combination of electric power systems to which a common automatic control scheme is applied in order to: (1) match, at all times, the power output of the generators within the electric power system(s) and capacity and energy purchased from entities outside the electric power system(s), with the load in the electric power system(s); (2) maintain, within the limits of Good Utility Practice, scheduled interchange with other Control Areas; (3) maintain the frequency of the electric power system(s) within reasonable limits in accordance with Good Utility Practice; and (4) provide sufficient generating capacity to maintain operating reserves in accordance with Good Utility Practice.

Coulomb - the practical unit of electric charge transmitted by a current of one ampere for one second. It is the charge carried by 6.2418 x 10¹⁸ electrons. Named for the French physicist Charles A. de Coulomb 1806.

current, electric - an electric current is the flow of electricity through a conductor such as a wire. An electric current can be understood by comparing it with the way water flows in a river. Imagine the channel of the river as being like a wire and the flow of water through it like the current flowing through the wire. The bigger the wire (or the river channel) the more current (or water) can flow. The amount of current that flows in a wire also depends on the pressure on the electric current. The pressure is known as the voltage, or volts (V). More current flows if the voltage is increased. This is like the way water flows in a river faster when the bed slopes steeply. So, for example, if you double up the number of cells in a battery, a bulb connected in the circuit will have more current flowing through it and it will shine more brightly. The way current and voltage are related is given by a law called Ohm's Law (named after the scientist who discovered it). Ohm's Law simply says that the more voltage (pressure) you put on to a circuit, the more current will flow. There are tow kinds of current used. The current produced by a battery is a direct current. It is often shown by DC. Direct current is used in all cars and in all electronic circuits. Direct current is most useful at low voltages. The other kind of current is used in mains supplies. It is called alternating current (shortened to AC). AC is only used for carrying electricity economically across the country. In electronic circuits there is a special device (called a transformer), that steps down mains voltage into the low voltage needed for use by electronics and another device (called a rectifier) that turns AC into DC. Some simple circuits, such as light bulbs, motors and heaters, can use AC directly. Motors that run on AC are also much more reliable than those that run on DC because they have a simpler design.

cycles-per-second - a measure of the frequency in an ac electric system. Abbreviated cps or cycles. Now replaced with the unit Hertz.

D

dc - abbreviation for direct current.

decibel - a logarithmic measure of the ratio of two quantities. Abbreviated dB. For electrical power, 1 dB = 10 x log₁₀ P₁/P₂. For electric voltage or current, 1 dB = 20 x log₁₀ E₁/E₂.

depth of discharge - the percent of rated capacity of a battery that has been discharged from the battery.

diode - an electronic semiconductor device that predominantly allows current to flow in only one direction.

direct current - electrical current that normally flows in one direction only. Abbreviated dc.

distribution - the act or process of delivering electric energy from convenient points on the transmission system (usually a substation) to consumers. The network of wires and equipment that distributes, transports or delivers electricity to customers. The delivery of electric energy to customers on the distribution service. Electric energy is carried at high voltages along the transmission lines. For consumers needing lower voltages, it is reduced in voltage at a substation and delivered over primary distribution lines extending throughout the area where the electricity is distributed. For users needing even lower voltages, the voltage is reduced once more by a distribution transformer or line transformer. At this point, it changes from primary to secondary distribution.

E

eco-friendly - the term “eco-friendly” is used to describe activities which are good for the environment. It is a shortening of “ecologically friendly,” and you may also hear terms like “environmentally friendly” or “green” used to describe similar activities. There are a range of ways in which activities can be eco-friendly, ranging from eco products which are constructed in an environmentally friendly way to making lifestyle changes which are designed to benefit the environment.

electricity, electric energy - electricity is a form of energy. Electricity and magnetism are inseparable because electricity produces magnetism. The discovery of electricity has effected our modern world perhaps more than any other discovery. Inventions that use electricity include electric light, electric heat, computers, motors, generators, telephones, radio and television, and the circuits that run motor cars. The first people to become aware of electricity were the Greeks who found that a natural material called amber attracted small piece of fur after it has been rubbed by a cloth. They had discovered static electricity. The word electricity comes from the Greek word for amber, elektron. In 1747, both William Watson in Britain and Benjamin Franklin in America realised that electricity could flow through materials, and that rubbing materials together simply transferred the electricity from one body to another. In fact we now know that small particles called electrons are transferred. It is the movement of electrons in a material that make electricity flow. It was Franklin who called called an excess of electrical charge positive and a lack of charge negative. He therefore believed that electricity flowed from positive to negative. In the 18th century, an assistant of the Italian scientist Luigi Galvani noticed that a dissected frog's leg twitched when he touched its nerve with a metal scalpel. Experimenting further, Galvani found that a frog's muscle would twitch when hung by a brass hook on an iron railing. Another Italian scientist, Alessandro Volta (for whom the word voltage is named) showed that when two metals are connected by some kinds of liquid, a flow of electricity results. By 1800, Volta had invented the electric cell (and battery). An electric cell separates electrons by chemical means (rather than by rubbing, as is the case with static electricity). If the electrons are removed in some way, the battery separates more electrons, thus changing chemical energy into electrical energy. This is current electricity.

electricity grid - a network of cables designed to connect power stations with their customers in offices, homes, schools and factories. The cables are often carried on tall overhead pylons across country, but they are buried underground in cities.

electricity power monitor - a device that measures in real-time the amount of electricity a household is consuming and provides the user with a constant display of actual usage and cost. The display acts as a prompt to be less wasteful and more energy efficient. Sailwider-SmartPower is a developer and manufacturer of electricity power monitor and controlling system.

electric Utility - a corporation, person, agency, authority, or other legal entity or instrumentality that owns and/or operates facilities within the United States, its territories, or Puerto Rico for the generation, transmission, distribution, or sale of electric energy primarily for use by the public and files forms listed in the Code of Federal Regulations, Title 18, Part 141. Facilities that qualify as cogenerators or small power producers under the Public Utility Regulatory Policies Act (PURPA) are not considered electric utilities.

electrolyte - a nonmetallic conductor of electricity usually consisting of a liquid or paste in which the flow of electricity is by ions.

energy - the capacity for, or the ability to do, mechanical work. Electrical energy is measured in kilowatt-hours for billing purposes.

energy monitor - a device that measures in real-time the amount of electricity a household is consuming and provides the user with a constant display of actual usage and cost. The display acts as a prompt to be less wasteful and more energy efficient. Sailwider-SmartPower is a developer and manufacturer of energy monitor and control system.

F

Farad - a unit of capacitance. One coulomb of charge will produce a potential difference of one volt across a capacitance of one Farad. Named for the English physicist Michael Faraday 1867.

fault - a short circuit.

feeder - circuit conductors between the service equipment and the last downstream branch circuit overcurrent protective device.

filter - a device made up of circuit elements designed to pass desirable frequencies and block all others. It typically consists of capacitors and inductors.

FLA  - Full load amperes, also sometimes abbreviated RLA for full load amperes. This is the current in amperes that a motor requires to produce rated nameplate horsepower output when rated nameplate voltage and frequency is provided to it's terminals.

float charge - charging current supplied to a battery which overcomes the battery self-discharge rate. This current, under otherwise normal conditions, will maintain the battery in a fully charged state.

force - a pulling or pushing action that occurs between poles of a magnet or electrical charges on the surface of insulators.

fluorescent light - a fluorescent light is a tubular form of lighting. It does not have a filament that glows, but is contains (mercury) vapour that gives off an invisible kind of light called ultra violet light. The ultra violent light strikes particles of a coating on the tube, which then give out visible light (they fluoresce). A fluorescent tube needs a high voltage to work. Very little heat is given out, which is why a fluorescent tube is more efficient and cheaper to operate than a filament light bulb. Fluorescent tubes can now be made very compact. They are called 'energy saving' lights when sold for use i homes. Tubes with gases under high pressure are used for street lighting. Sodium vapour makes the orange coloured street lighting; mercury vapour lamps produce a greenish blue light. These are also very economical to run. Gas-filled tubes are also used to produce flashes of high intensity light. These are used in lighthouses.

frequency - the number of complete alternations or cycles per second of an alternating current. It is measured in Hertz. The standard frequency in the US is 60 Hz. However, in some other countries the standard is 50 Hz.

fuse - a safety device which prevents appliances from being ruined (or causing a fire) when circuits are overloaded; a thin strip of metal located within the fuse will burn up if a large electric current goes through it causing a break in the circuit and the subsequent "shutting down" of the device.

G

gassing - gas by-products produced by the chemical reactions that occur when charging a battery. Since one of these gasses is often hydrogen, safety precautions must be taken to ensure proper ventilation to avoid the danger of explosion.

generator (electric generator, electric power generator ) - a machine for producing electricity. It is like a motor in reverse. The spindle is turned and electricity flows from the surrounding coiled wire. Many forms of energy can be used to turn the shaft. For example, the shaft may be connected to the wheel of a bicycle, then, as the bicycle wheel turns, the shaft of the generator (in this case called a dynamo) also turns, and power is fed to the cycle bulbs. The shaft can also be connected to a water wheel, or the blades of a wind generator. The biggest power stations, however, use steam to turn the shaft.

grid - in the electrical arena, a term used to refer to the electrical utility distribution network.

ground - a conducting connection between an electrical circuit or device and the earth. A ground may be intentional, such as in the case of a safety ground, or accidental which may result in high overcurrents.

H

harmonic - a sine wave which is an integral multiple of a base frequency. For example, the third harmonic on a 60 Hz system is a frequency of 180 Hz. Certain types of electrical equipment generate harmonics which interfere with the proper functioning of other devices connected to the same system.

Henry - the practical unit of inductance. One Henry is equal to the inductance in which the change of one ampere per second results in an induced voltage of one volt. Abbreviated H. Named for the American physicist Joseph Henry 1878.

Hertz - unit of frequency. One Hertz equals one complete cycle per second of an ac source. Abbreviated Hz. Named after the German physicist Heinrich R. Hertz 1894. This unit replaces the former "cycles-per-second."

horsepower - a unit of power equal to 746 watts.

Hz - abbreviation for Hertz.

I

IEEE - abbreviation for Institute of Electrical and Electronics Engineers.

impedance - the total effects of a circuit that oppose the flow of an ac current consisting of inductance, capacitance, and resistance. It can be quantified in the units of ohms.

inductance - the characteristic of an electric circuit by which a voltage is induced in it by a variation of current. This can be a variation of the current in the circuit itself (self-inductance) or in a nearby circuit (mutual inductance). The magnitude of the characteristic is measured in the units of Henries.

interruptible load - refers to program activities that, in accordance with contractual arrangements, can interrupt consumer load at times of seasonal peak load by direct control of the utility system operator or by action of the consumer at the direct request of the system operator. It usually involves commercial and industrial consumers. In some instances the load reduction may be affected by direct action of the system operator (remote tripping) after notice to the consumer in accordance with contractual provisions. For example, loads that can be interrupted to fulfill planning or operation reserve requirements should be reported as Interruptible Load. Interruptible Load as defined here excludes Direct Load Control and Other Load Management. (Interruptible Load, as reported here, is synonymous with Interruptible Demand reported to the North American Electric Reliability Council on the voluntary Office of Energy Emergency Operations Form OE-411, "Coordinated Regional Bulk Power Supply Program Report," with the exception that annual peak load effects are reported on the Form EIA-861 and seasonal (i.e., summer and winter) peak load effects are reported on the OE-411).

Institute of Electrical and Electronics Engineers - an independent organization which develops electrical standards and furthers the profession of electrical and electronics engineers.

inverter - an electrical device which is designed to convert direct current into alternating current. This was originally done with rotating machines which produced true sine wave ac output. More recently this conversion has been performed more economically and efficiently using solid state electronics. However, except for the most expensive models, these devices usually do not produce perfect sine wave output.  This sometimes can result in electromagnetic interference with other sensitive electronic devices.

ion - a positively or negatively charged atom or molecule.

J

Joule - a unit of work or energy equal to one watt for one second. One kilowatt hour equals 3,600,000 Joules. Named after James P. Joule, an English physicist 1889.

Joule’s law - defines the relationship between current in a wire and the thermal energy produced. In 1841an English physicist James P. Joule experimentally showed that W = I² x R x t where I is the current in the wire in amperes, R is the resistance of the wire in Ohms, t is the length of time that the current flows in seconds, and W is the energy produced in Joules.

K

kilovar - unit of ac reactive power equal to 1000 vars. Abbreviated kVAr or KVAR.

kilovolt - unit of electrical potential equal to 1000 volts. Abbreviated kV or KV.

kilovolt amperes - a unit of apparent power equal to 1000 volt amperes. Here, apparent power is in contrast to real power. On ac systems the voltage and current will not be in phase if reactive power is being transmitted. Usually abbreviated kVA or KVA.

kilowatt - unit of power equal to 1000 watts. Abbreviated kW or KW.

kilowatt-hour - unit of energy or work equal to one kilowatt for one hour.   Abbreviated as kwh or KWH. This is the normal quantity used for metering and billing electricity customers. The price for a kwh varies from approximately 4 cents to 15 cents. At a 100% conversion efficiency, one kwh is equivalent to about 4 fluid ounces of gasoline, 3/16 pound LP, 3 cubic feet natural gas, or 1/4 pound coal.

kV - abbreviation for kilovolt and equal to 1000 volts.

kVA - abbreviation for kilovolt amperes.

kVAr - abbreviation for kilovar. A unit of ac reactive power equal to 1000 vars.

kW - abbreviation for kilowatt. A unit of power equal to 1000 watts.

L

listed - an electrical device or material that has been tested by a recognized organization and shown to meet appropriate standards. Many local governmental authorities require that installed electrical products be listed. A well-known listing organization is Underwriters Laboratories (UL).

load - a device which consumes electrical power and is connected to a source of electricity.

load shifting - involves moving load from on-peak to off-peak periods. Popular applications include use of storage water heating, storage space heating, cool storage and customer load shifts to take advantage of time-of-use or other special rates.

loop/looped - An electrical circuit that provides two sources of power to a load or to a substation so that if one source is de-energized the remaining source continues to provide power.

LRA - Locked rotor amperes. This is the current that a motor would require if the rotor were locked in place and prevented from rotating and rated nameplate voltage and frequency were applied to its terminals. This is also the current that could appear briefly during motor starting. While the motor comes up to speed this current gradually drops off and when the speed approaches running rpm this current rapidly falls to the RLA value. Often the starting current is less than the LRA value because the voltage at the motor terminals dips during starting. This LRA value is important when sizing a generator because the generator's surge rating must be large enough to handle it.
 

M

magnetic pole - the place where the magnetic field enters or leaves a magnet. Because the lines of force concentrate at the poles, these are the most powerful parts of the magnet. Magnetic poles can be either North Poles or South Poles. The field leaves the North Pole and enters the South Pole. The Earth has magnetic poles, which are not in quite the same positions as the geographic poles.

MCA - Minimum circuit amperes. This is the minimum current rating allowed for the wiring and circuit breaker or fuse protection for the equipment.  It is used by the installer and electrician to size the branch circuit to feed the equipment.

monitoring & evaluation Cost - expenditures associated with the planning, collection, and analysis of data used to assess program operation and effects. It includes activities such as load metering, customer surveys, new technology testing, and program evaluations that are intended to establish or improve the ability to monitor and evaluate the impacts of DSM programs, collectively or individually.

multi-meter - a meter designed to measure several properties of electricity all in one box. Normally multi-meters measure current, voltage and resistance.

N

National Electrical Code - a code for the safeguarding of people and property from hazards related to the use of electricity. Compliance with this code along with proper maintenance will result in an installation essentially free from hazard. Abbreviated NEC. The NEC was first developed in 1897 as a result of the efforts of various insurance, electrical, architectural, and allied interests. It is sponsored and regularly updated by the National Fire Protection Association.

NEC - abbreviation for the National Electrical Code.

neutral - a conductor of an electrical system which usually operates with minimal voltage to ground. Depending on the type of system, it may carry little current or only unbalance current. Systems that have one conductor grounded use the neutral for this purpose.

O

Ohm - a unit of electrical resistance. A circuit resistance of one ohm will pass a current of one ampere with a potential difference of one volt. Abbreviated using the Greek letter omega (W ). Named for the German physicist George Simon Ohm 1854.

Ohm’s Law - defines the relationship between voltage, resistance, and current. In 1828 the German physicist George Simon Ohm showed by experiment that the current in a conductor is equal to the difference of potential between any two points divided by the resistance between them. This may be written as I = E / R where E is the potential difference in volts, R is the resistance in Ohms, and I is the current in amperes.

open circuit voltage - the maximum voltage produced by a power source with no load connected.

overcurrent - any current beyond the continuous rated current of the conductor or equipment. This may be value slightly above the rating as in the case of an overload, or may be far above the rating as in the case of a short circuit.

overload - operation of electrical equipment above its normal full-load rating or of a conductor above its rated ampacity. An overload condition will eventually cause dangerous overheating and damage.

P

power - the rate at which work is performed or that energy is transferred. Electric power is commonly measured in watts or kilowatts. A power of 746 watts is equivalent to 1 horsepower. Power is a way of talking about the amount of electrical energy used. All electrical equipment uses power. The amount of power used is measured in Watts (W). Devices that use a large amount of power are always run off the mains A small mains electric light uses about 25W; a large electric light uses 100W. A small flashlight bulb used in a torch may use 1.5W. Appliances such as cookers and heaters use much more power. For example, the heating ring of an electric cooker may be about 1000W (1kW ­ kilowatts). An electric heater may consume 2000W (2kW ) or more. A shower has to heat water very fast and may consume 7kW. The more power taken by an electric circuit, the thicker the supply wires have to be. That is why the cable use to connect an electric heater to the mains supply is thicker than the cable used to connect a table lamp to the mains. In a battery-run circuit, the more power that is used, the faster a battery is run down.
Power is amps multiplied by volts. So, for example, if a motor is connected to a 9V battery mains and uses 3 watts of power, we can easily work out how much current is flowing in the wires.
Power W = Voltage (V) x current (A)
3 = 9 x A
A = 1/3
The motor uses 1/3A of current.
Calculations like these allow electricians to work out the cable to be used to connect mains appliances and also the size the fuse that should be used.

power factor - the ratio of real power to apparent power delivered in an ac electrical system or load. Its value is always in the range of 0.0 to 1.0 or 0% to 100%. A unity power factor (1.0) indicates that the current is in phase with the voltage and that reactive power is zero.

power supply - the power that enters homes, schools, factories and so on.

Public Street and Highway Lighting - Public street and highway lighting includes electricity supplied and services rendered for the purposes of lighting streets, highways, parks, and other public places; or for traffic or other signal system service, for municipalities, or other divisions or agencies of State or Federal governments.

Q

R

rates, time-of-use - prices for electricity that vary depending upon what time of day or night a customer uses it. Time-of-use rates are designed to reflect the different costs an electric company incurs in providing electricity during peak periods when electricity demand is high and off-peak periods when electricity demand is low. MGE has two time periods defined for its time-of-use services: on-peak and off-peak. On-peak periods are defined as 10 a.m. through 9 p.m., Monday through Friday, excluding holidays. All other periods are off-peak. Whether customers benefit from time-of-use rates depends on the percentage of total consumption used during on-peak periods. Generally, customers who use less than 30% to 36% of their total consumption during on-peak periods may benefit from these rates. However, individual analysis of electricity usage habits is required to see if a time-of-use service would be of potential value.

rates, unbundled - the process of itemizing the rates for specific services that used to be covered under one rate.

reactive power - the mathematical product of voltage and current consumed by reactive loads. Examples of reactive loads include capacitors and inductors. These types of loads when connected to an ac voltage source will draw current, but since the current is 90^o out of phase with the applied voltage they actually consume no real power in the ideal sense.

real power - the rate at which work is performed or that energy is transferred. Electric power is commonly measured in watts or kilowatts. The term real power is often used in place of the term power alone to differentiate from reactive power.  Also called active power.

rechargeable battery - a battery that can be used more than once. Rechargeable batteries have to be charged in the first place, they do not contain chemicals that can make electricity. Instead they contain materials that store it.

Renewable (Green) Energy - Electricity that is made from natural fuel sources via the environment, such as wind, water or solar. See Bounce Energy green energy plans and rates.

resistance - the characteristic of materials to oppose the flow of electricity in an electric circuit.

RLA  - Running load amperes, also sometimes abbreviated FLA for full load amperes. This is the current in amperes that a motor requires to produce rated nameplate horsepower output when rated nameplate voltage and frequency is provided to it's terminals.

rms - "root-mean-square", a method of computing the effective value of a time-varying electrical wave.  For example, an ac current is said to have an effective or rms value of one ampere when it produces heat in a certain resistance at the same average rate as a continuous (or dc) current of one ampere would in the same resistance. rms - "root-mean-square", a method of computing the effective value of a time-varying electrical wave.  For example, an ac current is said to have an effective or rms value of one ampere when it produces heat in a certain resistance at the same average rate as a continuous (or dc) current of one ampere would in the same resistance. rms - "root-mean-square", a method of computing the effective value of a time-varying electrical wave.  For example, an ac current is said to have an effective or rms value of one ampere when it produces heat in a certain resistance at the same average rate as a continuous (or dc) current of one ampere would in the same resistance. rms - "root-mean-square", a method of computing the effective value of a time-varying electrical wave.  For example, an ac current is said to have an effective or rms value of one ampere when it produces heat in a certain resistance at the same average rate as a continuous (or dc) current of one ampere would in the same resistance.

separately derived system - an electrical system whose power is provided by a stand-alone generator, transformer, or converter and which has no direct electrical connection or ground connection to another source (such as the utility). The NEC contains special grounding and bonding requirements for such systems.

service - the equipment and conductors that transmit electricity from the utility supply system to the building being served.

service equipment - the circuit breaker or fused switch located near where the service conductors enter the building which is intended as the primary means of disconnecting the supply.

short circuit - a low resistance connection unintentionally made between points of an electrical circuit which may result in current flow far above normal levels. Fuses are designed to melt when short circuits occur.

sine wave - in ideal electric systems, the characteristic shape of the alternating voltage or current wave. This shape matches the trigonometric sine function of the acute angle in a right triangle and equals the ratio of the side opposite the angle to the hypotenuse.

single-phase - an ac electric system or load consisting of at least one pair of conductors energized by a single alternating voltage. This type of system is simpler than three-phase but has substantial disadvantages when large amounts of power have to be delivered.

socket - a place in a wall or an appliance where the electricity supply plug is inserted.

solar cell, solar power - the electrical power produced from the radiation of the sun. A solar power station contains many highly polished mirrors that reflect the sun's rays onto to tubes carrying water. The water gets hot enough to produce steam which can then turn the shaft of a generator.

spark - the sudden flow of electricity between two charged surfaces. A flash of lightning is the world's biggest spark.

static (static electricity) - electricity that builds up on the surfaces of insulating materials. It consists of positive and negatively charged surfaces.

surge capacity - the ability of an electrical supply to tolerate a momentary current surge or inrush imposed by the starting of motors or the energizing of transformers.

switch - a device for breaking the flow of electricity in a circuit

tariff - a schedule of prices or fees.

tariff schedule - a document filed with the regulatory authority(ies) specifying lawful rates, charges, rules and conditions under which the utility provides service to the public.

three-phase - an ac electric system or load consisting of three conductors energized by alternating voltages that are out of phase by one third of a cycle. This type of system has advantages over single-phase including the ability to deliver greater power using the same ampacity conductors and the fact that it provides a constant power throughout each cycle rather than a pulsating power, as in single-phase. Large power installations are three-phase.

three-phase service - service where the facility (e.g., manufacturing plant, office building, warehouse, barn) has three energized wires coming into it. Typically serves larger power needs of greater than 120V/240V. Usually required for motors exceeding 10 horsepower or other inductive loads. Requires more sophisticated equipment and infrastructure to support and tends to be more expensive to install and maintain.

transformer - a device that converts one ac voltage and current to a different voltage and current. Constructed using two or more coils of wire around a common magnetic core. The energy is transferred from one coil, usually considered the primary winding, to the other coil, the secondary winding by means of mutual induction in the magnetic core. Transformers are an efficient and economical means of transferring large amounts of ac electric power at high voltages. This is the primary advantage of ac systems over dc systems.

transmission lines -  large cables designed to carry very high voltage electricity from the power station to where it is needed. Transmission lines are cables. They are supported on metal frames called pylons.

two-way switch - a switch which controls the flow of electricity from either of two points.

Underwriters Laboratories - a non-profit organization that was established by the insurance industry to test electrical devices for safety.

uninterruptible power supply - a device that provides a constant regulated voltage output in spite of interruptions of the normal power supply. It includes filtering circuits and is usually used to feed computers or related equipment which would otherwise shutdown on brief power interruptions. Abbreviated UPS.

VA - abbreviation for volt ampere. Unit of apparent power.

VAR - abbreviation for volt ampere reactive. Unit of ac reactive power.

Variable Costs - Costs that change or vary with usage, output or production. Example: Fuel costs.

volt - The electrical potential difference or pressure across a one ohm resistance carrying a current of one ampere.  Named after Italian physicist Count Alessandro Volta 1745-1827.

volt ampere - a unit of apparent power equal to the mathematical product of a circuit voltage and amperes. Here, apparent power is in contrast to real power. On ac systems the voltage and current will not be in phase if reactive power is being transmitted. Usually abbreviated VA.

voltage drop - a voltage reduction due to impedances between the power source and the load. These impedances are due to wiring and transformers and are normally minimized to the extent possible.

watt - A unit of power equal to the rate of work represented by a current of one ampere under a pressure of one volt.  Named after the Scottish engineer James Watt, 1819.

wind generator, wind power - a method of concerting the power of the wind into electrical power. The blades of a wind turbine are connected to the shaft of a generator, so that when the blades turn electricity is produced. A site with frequently windy conditions is needed to operate a wind generator.

wire - strands of metal, or sometimes a single piece of metal, designed to be thin enough to be flexible. It is used to connect components in a circuit.

wye - a three phase, four-wire electrical configuration where each of the individual phases is connected to a common point, the "center" of the Y. This common point normally is connected to an electrical ground.

x - reactance expressed in Ohms.

y - see "wye".

zero crossing - the point at which a sinusoidal voltage or current waveform crosses the zero reference axis

Electricity Energy Monitors

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