Download Electrical Plan Task Force Glossary of Terms

Electrical Plan Task Force Glossary of Terms
A
Alternating Current (AC) – An electrical current which reverses direction repeatedly due to a
change in voltage which occurs at the same frequency.
Ampacity – The maximum continuous current that a conductor can carry without overheating.
Ampere – A unit of measurement for current. Electric current produced by one volt applied
across a resistance of one ohm; also equal to the flow of one coulomb per second. See Current.
B
Breaker – A device that opens a circuit automatically when there is a fault on a power line. Also
a switch used to open/close the flow of electricity to a specific circuit. A breaker can provide
overcurrent protection. Also referred to as a Circuit Breaker.
Bus – An electrical conductor that connects two or more conductors.
Bushing – An insulated connection between the internal and external components of electrical
equipment.
C
Capacitor – A device to store an electrical charge. In the field of electric power transmission and
distribution, capacitors are devices used for power factor correction and voltage regulation.
Power factor correction improves the capability to deliver useful power (real power) to loads
and voltage regulation helps to maintain constant service voltage.
Capacity – The maximum amount of electrical load which a device can carry at one time. The
amount of electric power that can be delivered at one time by a generating unit, generating
station, or all the plants on an electric system.
Circuit breaker – A device that opens a circuit automatically when there is a fault on a power
line. Also a switch used to open/close the flow of electricity to a specific circuit. A breaker can
provide overcurrent protection. Also referred to as a Breaker.
Conductor – A substance or body that allows an electric current to pass continuously along it. A
wire.
Continuous Load – A sustained electrical load current for three hours or more.
Current – The flow of electricity commonly measured in amperes. See also Ampere.
Cycles-per-second – A unit of frequency. One Hertz equals one complete cycle per second of an
AC source. See also Frequency and Hertz (Hz).
D
Direct Current (DC) – Electrical current that normally flows in one direction only.
Demand – The rate at which electric energy is delivered to or by a system, expressed in
kilowatts, or other suitable units at a given instant or averaged over any designated period of
time. Demand varies from hour to hour, day to day, and season to season.
Distribution Substation – A group of transformers that reduces the line voltage from a
transmission level 161 kV – 46 kV to a distribution level 34.5 kV - 12.5 kV in order to distribute
power to a number of customers.
Distribution Line – One or more circuits of a distribution system either direct-buried, in conduit
or on the same line of poles or supporting structures, operating at relative low voltage as
compared with transmission lines.
Distribution System – The distribution system includes all lines energized at voltages less than
the nominal 34,500 volts (34.5 kV).
DSM (Demand Side Management) – The planning and implementation of strategies designed
to encourage consumers to improve energy efficiency, reduce energy costs, change the time of
usage, or promote the use of different energy source.
E
Easement – An easement is a right given to another person or entity to trespass upon land that
person or entity does not own. Easements are used for roads, for example or given to utility
companies for the right to bury cables or access utility lines.
Electrical Energy – Electric energy is a measure of the amount of usage over time and is
measured in kilowatt-hours or megawatt-hours.
Energy – See Electrical Energy.
F
Fault – A problem on the line causing a fuse to blow or a breaker to operate.
Feeder – A distribution line that carries electricity from a substation to a specific geographic
area where it will be distributed among a large number of customers.
FERC (Federal Energy Regulatory Commission) – An independent U.S. government agency that
regulates the interstate transmission of natural gas, oil, and electricity.
Franchise – A license or similar legal authority, granted to a utility by a jurisdiction, to provide
service at retail in a given geographic area. An exclusive franchise is a monopoly to provide
service in that area.
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 piece of equipment that opens and de-energizes a circuit when there is a problem on
the line. The fuse must be replaced when it has "blown".
G
Generator – A unit that converts thermal, mechanical, chemical or nuclear energy into electric
energy.
Generation Mix – A term used to describe the types of electrical generation a utility uses, or
presently has on line –coal, wind, hydro, etc.
Giga-watt (GW) – 1,000 Mega-watts, or 1,000,000 kilo-watts, or 1,000,000,000 watts.
Ground – An electrical connection to earth or some other conductor that is connected to earth.
Refers to electricity's habit of seeking the shortest route to earth. Neutral wires carry it there in
all circuits. An additional grounding wire or the sheathing of the metal-clad cable or conduit—
protects against shock if the neutral leg is interrupted.
Grounded – Connected to or in contact with earth or connected to some extended conductive
body that serves instead of the earth.
Guy Wire – A brace or cable fastened to the pole to strengthen it and keep it in position. Guys
are used whenever the wires tend to pull the pole out of its normal position and to sustain the
line during the abnormal loads caused by sleet, wind, and cold. Guys counteract the unbalanced
force imposed on the poles by dead-ending conductors; by changing conductor size, types, and
tensions; or by angles in the transmission or distribution line. Commonly mispronounced as
“guide wire”.
H
Hertz (Hz)– A unit of frequency. One Hertz equals one complete cycle per second of an ac
source. Named after the German physicist Heinrich R. Hertz 1894. This unit replaces the former
"cycles-per-second."
Horsepower – One horsepower for rating electric motors is equal to 746 watts.
Hot – Energized (i.e., the line hot or live).
I
IEEE (Institute of Electrical and Electronics Engineers) – A non-profit organization that is the
world's leading professional association for the advancement of technology. The IEEE promotes
the engineering process of creating, developing, integrating, sharing and applying knowledge
about electro and information technologies and sciences for the benefit of humanity and the
profession.
Insulator – A device used to isolate conductors from the distribution poles or transmission
structures that support them. They are generally made of porcelain or glass. Sometimes they
are favorite targets for vandals to "shoot out" causing an interruption of power.
IOU (Investor Owned Utility) – A utility that is structured as a tax-paying business financed
through sales of common stock. Rocky Mountain Power is an Investor Owned Utility.
IPP (Independent Power Producer) – A company that generates power but is not affiliated
with an electric utility.
IRP (Integrated Resource Plan) – The product of the process many utility commissions use to
select the generation resources needed to meet future demand for electricity.
J
Junction Box – A box through which the main conductors of a system of electric distribution
pass, and where connection is made with branch circuits.
K
KiloVolt (kV) – A common unit of measurement for voltage of power lines and equal to 1000
volts.
Kilowatt (kW) – A unit of measure of the rate of electric energy use. A one hundred-watt light
bulb uses 100 watts of electricity. Ten such bulbs would use one kilowatt or 1000 watts. See
also Kilowatt-Hour.
Kilowatt-Hour (kWh) – A kilowatt-hour is a measure of electric energy equal to one kilowatt of
power supplied to or taken from an electric circuit for one hour. A kilowatt-hour could be used
to light a 100-watt bulb for 10 hours.
L
Line Loss Load – The amount of electric power delivered or required at any specified point or
points on a system. Load originated primarily at the power-consuming equipment of the
customer.
Load – The amount of power that is drawn from a utility system at a given point in time. The
peak load is the highest amount of power drawn down at anyone time, or the utilities
maximum capacity or demand. Load can be divided into 3 major classes – industrial load,
commercial load, and residential load. That is, collectively, the devices in an electrical circuit
that consume electricity.
Load Curve – A chart showing power (kilowatts) supplied, plotted against time of occurrence,
and illustrating the varying magnitude of the load during the period covered.
Load Factor – Load factor represents the ratio of average load that occurs over a billing period
to maximum demand. Load factor is a measure of the efficiency of use of electricity. A high load
factor is better than a low load factor because this means that electricity is used at a more
constant rate without having the peaks and valleys. A business with a high factor typically
results in a lower average cost per kWh and has a lower cost of service by the utility.
Load Forecasting – The procedures used to estimate future consumption of electricity. These
estimates are used in planning for generation, transmission, and distribution facilities; in
calculating future revenue from the sales of electricity; in determining cost allocations for the
various rate classes; and in assessing the impact on load of changes in policies or underlying
conditions such as the level of employment in the region. Load forecasts are developed either
to provide the most likely estimate of future load or to determine what load would be under a
set of specific conditions; e.g., extremely cold weather, high rates of inflation, or changes in
electricity prices. Forecasting procedures include trending (extrapolating past trends into the
future) and econometrics (where statistical relationships are established between electricity
use and causal variables such as price, population, income, and employment and then used to
forecast load based on projections of these causal variables).
M
Megawatt (MW) – 1,000 kilowatts, or 1,000,000 watts. See Kilowatt (kW).
Megawatt-hour (MWh) – 1,000 kilowatt-hours or 1,000,000 watt-hours.
MEHC (Mid-American Energy Holding Company) – Parent company of Rocky Mountain Power.
Municipal Utility – An electric utility system owned and/or operated by a municipality that
generates and/or purchases electricity at wholesale for distribution to retail customers
generally within the boundaries of the municipality.
N
NEC (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. 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.
NERC (North American Electric Reliability Council) – An independent organization that works
to ensure that the bulk electric system in North America is reliable, adequate, and secure.
NESC (National Electric Safety Code) – The rules published by the Institute of Electrical and
Electronics Engineers (IEEE) applying to grounding, installation, maintenance and operation of
electric supply, communication, utilization equipment, lines and facilities which have been
adopted as standard by the American National Standards Institute.
Net Metering – A method of measuring the difference between the electricity the customer
uses from the power company and the excess electricity they give back by generating their own
power. Their meter keeps track of power usage taken from the company and customer power
provided back to the company.
Neutral – The return wire of the system sometime called a ground.
O
Off-Peak – Those periods of time at which energy is being delivered far below the utility's
maximum demand.
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 ( ).
Named for the German physicist George Simon Ohm 1854.
Ohm’s Law – An equation that 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.
On-Peak – Those periods of time at which energy is being delivered near and including the
utility's maximum demand.
Outage – Interruption in the delivery of electric service.
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.
Overhead Service – Electric service supplied to the customer from the power company utilizing
overhead conductors.
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
Partial Power – The loss of one phase of three-phase service.
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.
Peak Demand – The maximum demand imposed on a power system or component thereof
during a specified time period.
Peak Load – The maximum electrical load consumed or produced in a stated period of time. It
may be the maximum instantaneous load or the average load within a designated interval of
time.
Phase – One wire of a two, three or four wire system.
Point of Delivery – The point where the Power Company's circuit connects to the Customer's
system.
Power – Power is the rate of energy production or transfer. Electrically, power is expressed in
watts, which is the product of applied voltage and resulting in-phase current. See also Energy.
Power Grid – A network of major electrical connections between electric companies; used to
transfer power from one region to another.
Power Plant – Place where electricity is generated; the primary source of power for a typical
transmission and distribution system.
PPE (Personal Protective Equipment) – Refers to protective clothing, helmets, goggles, or other
garment designed to protect the wearer's body from injury by blunt impacts, electrical hazards,
heat, chemicals, and infection, for job-related occupational safety and health purposes.
Primary – The high voltage part of the distribution system. Usually over 600 volts.
PSC (Public Service Commission) – A utility regulating authority.
PURPA (Public Utility Regulatory Policies Act) – A law passed in 1978 by the United States
Congress as part of the National Energy Act, meant to promote greater use of renewable
energy. This law created a market for non-utility electric power producers forcing electric
utilities to buy power from these producers at the "avoided cost" rate, which was the cost the
electric utility would incur were it to generate or purchase from another source. Generally, this
is considered to be the fuel costs incurred in the operation of a traditional power plant.
Q
R
Recloser – A switch that will automatically open to break a circuit if it detects electrical
problems, and then attempts to close the circuit at timed intervals. If the electrical problem
falls to correct itself, the switch will remain open after a certain number of attempts to close
the circuit.
RMP (Rocky Mountain Power) – The investor owned electric utility which serves customers in
Utah, Idaho and Wyoming. A subsidiary of Mid-American Energy Holding Company (MEHC).
ROW (Right of Way) – Right-of-way is an interest in property either owned in fee or as an
easement transferred through grant, prescription, dedication, or the right of Eminent Domain.
Public utilities (regulated by the Public Utility Commission) have the right by State Statue to use
a portion of the road right-of-way for installation and maintenance of their facilities.
S
SCADA (Supervisory Control & Data Acquisition) – It generally refers to a computer system
monitoring and controlling a process.
Secondary – Low voltage connecting wires; part of the distribution system usually under 600
volts (often between 120 - 480 volts).
Sectionalize – To isolate a problem and restore as many people to service as possible.
Single-phase – An alternating current 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 threephase but has substantial disadvantages when large amounts of power have to be delivered.
Single Phase Service – A service consisting of two “hot" wires and a neutral, this is a typical
house service (120/240 volts).
Smart Grid – A term used for an ever widening palette of utility applications that enhance and
automate the monitoring and control of electrical distribution.
Structures – The poles or towers used to support transmission and distribution line conductors.
Substation – A group of transformers is called a substation. Substations generally decrease the
transmission voltage to levels that can be carried to distribution lines.
Sub-transmission – Lines that are energized between the voltages of 161,000 volts and 46,000
volts.
Switch – A device that open or closes a circuit.
Switchyard – An arrangement of switches, in an enclosed area, that receive electricity and
direct it to transmission lines.
T
Three- phase – An alternating current 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.
Transformer – A device that converts one ac voltage and current to a different voltage and
current. A transformer is constructed using two or more coils of wire around a common
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 alternating
current systems over direct current systems.
Transmission Loss – the electrical energy lost in the process of transporting it at high voltage
over transmission lines. Generally, the greater the distance, the greater the loss; the higher the
voltage, the less the loss.
Transmission System – An interconnected group of electric lines and associated equipment for
the movement or transfer of electric energy in bulk between points of supply and points at
which it is transferred for delivery to ultimate consumers, or is delivered to electric systems of
other utilities. Transmission lines at energized at 230,000 volts (230 kV) or higher.
Trip – A sudden shutdown of a piece of equipment. Generally caused when a breaker operates
to isolate a portion of the system in order to protect or maintain service to the remainder
U
Undergrounding – The act or program for placing the overhead transmission or distribution
system underground.
V
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.
Voltage – The driving force, or "electrical pressure," that causes current to flow through a
complete circuit.
Voltage Drop – Wires carrying current always have inherent resistance (or impedance) to
current flow. Voltage drop is defined as the amount of voltage loss that occurs through all or
part of a circuit due to the impedance.
W
Watt – A unit of measurement of the rate of electric energy use. One watt is the rate of energy
transfer equivalent to one ampere flowing under a pressure of one volt at unity power factor.
See also Kilowatt and Megawatt.
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