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The Glossary provides definitions for industry-related terminology and acronyms.
A
Access: The contracted right to use an electrical system to transfer electrical energy.
B
Blackout: A total power failure over a large area; usually caused by the failure of major generating equipment or transmission facilities.
C
Capability: he maximum load that a generating unit, generating station, transmission line or other electrical apparatus can carry under specified conditions for a given period of time without exceeding approved limits of temperature and stress.
Capacitor banks: System elements (equipment) that support the voltages necessary to provide reliable service to customers.
Capacity: The amount of electric power delivered or required for which a generator, turbine, transformer, transmission circuit, apparatus, station, or system is rated by the manufacturer. Capacity is also used synonymously with capability.
Certificate of Need (CON): This is the first step of the permitting process in Minnesota.
Circuit: A path of conductors (wires) through which an electric current flows.
Conductor: A material through which electric current flows easily. Wires are often referred to as conductors.
Contingency: An outage of a transmission line, generator or other piece of equipment, which affects the flow of power on the transmission network and impacts other network elements.
D
Demand: The rate at which electric energy is delivered to or by a system or part of a system, generally expressed in kilowatts (kw) or megawatts (mw), at a given instant or averaged over any designated interval of time.
Distribution: An interconnected group of lines and associated equipment for the local delivery of lower voltage electricity from the transmission network to the end users.
E
Easement: A right purchased from property owner(s) that allows utility companies to construct, operate, maintain and control facilities, such as transmission lines, on the property.
Electromagnetic fields (EMFs): Electric and
magnetic fields often occur together, hence the term
electromagnetic fields. They are found throughout nature and can
be grouped by wavelength or frequency.
The counterparts have the following definitions:
- Electric fields - Created by voltage. Anytime something
electric is plugged in it has an electric field, even if it is
not in use. An electric field, in some instances, can be felt
when the hair on your neck stands up during a lightning storm,
for example. An electric field can be blocked by trees, walls,
or buildings.
- Magnetic fields - Created by current. Anything that carries
electricity (such as power lines) and anything that uses
electricity (such as home appliances in use) has a magnetic
field. A magnetic field cannot be felt, and it passes through
most objects.
Eminent domain: The power of a government body to condemn and use private property for public use with just compensation to the property owner.
Energy: The capacity for doing work; may be natural or manufactured. Electrical energy is usually measured in kilowatt-hours.
F
Federal Energy Regulatory Commission (FERC): An independent agency that regulates the interstate transmission of natural gas, oil and electricity.
G
Generation: The act of converting various forms of energy input (thermal, mechanical, chemical and/or nuclear energy) into electric power. Also, the amount of electric energy produced, usually expressed in kilowatt hours (kwh) or megawatt hours (mwh).
Grid: The transmission and distribution networks operated by electrical utilities.
H
H-frame: A wood structure used in transmission lines composed of two poles connected by a cross arm near the top.
Heavy loads: High volume of electricity flowing on a line, transformer or other equipment to meet a high demand for electricity, using during hot weather.
I
IBEW: International Brotherhood of Electric Workers.
IEEE: Institute of Electrical and Electronic Engineers, Inc.
Import/export: Ability of the transmission system to bring power into or out of an area in order to serve load.
Insulator: A component that opposes the flow of electric current; commonly made of glass or porcelain and used to support the conductor (wire).
J
K
Kilovolt (kV): A measure of voltage. Common transmission voltages on CAPX member systems are 34.5 kV, 41.6 kV, 69 kV, 115 kV, 161 kV, 230 kV and 345 kV.
L
Load: The amount of power drawn from an electric system at a specific time, or the total power drawn from the system. Peak load is the amount of power drawn at the time of highest demand. Also, anything that uses electrical energy.
Loading relief: A system change or reinforcement that results in lower power flows on equipment that is heavily loaded or overloaded.
Low voltages: Situation that can occur in parts of the system that are heavily loaded. Think of a clothesline pulled taut with nothing hanging on it, but which then tends to sag when more and more clothes (i.e. load such as motors) are attached.
M
Margin: The difference between (1) generation resources and electric demand or (2) the difference between the capacity of a transmission line and the power flowing on that line. Margin is usually expressed in megawatts (MW).
Megawatt (MW): One million watts or 1,000 kW.
Mid-Continent Area Power Pool (MAPP): The Mid-Continent Area Power Pool is an association of electric utilities and other electric industry participants. MAPP was organized in 1972 for the purpose of pooling generation and transmission.
Midwest Reliability Organization (MRO): A council charged with implementing NERC reliability standards for the eight states in the upper Midwest. This council covers the CAPX footprint.
Midwest Independent System Operator (MISO):
N
Network: A system of interconnected lines and electrical equipment
North American Reliability Council (NERC): A not-for-profit company formed by the electric utility industry in 1968 to promote the reliability of the electricity supply in North America. NERC consists of nine Regional Reliability Councils and one Affiliate whose members account for virtually all the electricity supplied in the United States, Canada, and a portion of Mexico.
O
Operating guides: Procedures carried out by transmission operators when certain events occur on the system that may compromise system reliability if no action is taken.
Outage: The unavailability of electrical equipment; could be planned for maintenance or unplanned (forced) by weather or equipment failures.
Overloads: Occur when power flowing through wires or equipment is more than they can carry without incurring damage.
P
Parallel path flows: When electricity flows from a power plant over the transmission system, it obeys the laws of physics and flows over the paths of least resistance. Though there may be direct connection between a power plant and a particular load area, some of the power will instead flow over other network lines "parallel" to the direction connection.
Power flows: Electricity moving through lines or other equipment.
Q
R
Rebuild: Removing an existing line and replacing it with a new, higher capacity line.
Reliable: When the system operates within standard industry and specific utility performance criteria.
Reliability: The degree of performance of the elements of the bulk electric system that results in electricity being delivered to customers within accepted standards and in the amount desired. The ability to deliver uninterrupted electricity to customers on demand, and to withstand sudden disturbances such as short circuits or loss of system components.
Reserve: The difference between an electric system's capability and the expected peak demand for electricity.
Right of Way (ROW): Use of property covered by an agreement (easement) that allows utilities to construct and operate their facilities there. Sometimes acquired through the right of eminent domain. Plural is rights of way.
RTO: Regional Transmission Organization.
S
Sag: The distance between the actual location of a conductor (at its lowest point in a given span) and an imaginary line drawn between the conductor’s two adjacent supports.
Serve load: Reliably deliver the amounts of electricity needed to match consumer needs at any given time.
SMMPA: Southern Minnesota Municipal Power Agency.
Stability: The ability of an electric system to maintain a state of equilibrium during normal and abnormal system conditions or disturbances.
Structures: Typically refers to poles within a given power line.
Substation: Place where transmission lines connect to each other and where protective equipment is located. Also where transformers are located to step the voltage up or down in order to put power into or take power out of the transmission network.
System Planning: The process by which the performance of the electric system is evaluated and future changes and additions to the bulk electric systems are determined.
T
T-D interconnection: Transmission to distribution interconnection; place where local distribution substations connect to transmission system.
Thermal rating: The maximum amount of electrical current that a transmission line or electrical facility can conduct over a specified time period before it sustains permanent damage by overheating or before it violates public safety requirements.
Thermal overloads: Power flows on lines or equipment that exceed their capacity limits.
Transfer capability: The measure of the ability of interconnected electric systems to move or transfer power in a reliable manner from one area to another over all transmission lines between those areas under specified system conditions.
Transformers: Devices that changes voltage levels.
Transmission: The process of transporting electric energy over long distances to other principal parts of an electric system or to other utility systems for subsequent voltage reduction and distribution.
Transmission Grid: An interconnected group of lines and equipment for transporting electric energy in bulk on a high voltage power line from a source or sources of power supply (e.g. power plant) to a point of use within a utility system or to a point of interconnection with another utility system or power grid.
U
Uprates: Make the transmission system element able to carry more electricity than it currently can. This can include increasing line clearances or replacing limiting pieces of equipment to enable the safe transport and delivery of more power.
V
Voltage: A type of "pressure" that drives electrical charges through a circuit. Higher voltage lines generally carry power longer distances.
Voltage collapse: Can occur after a contingency where the voltage dips low enough and cannot recover quickly enough. In this situation protective equipment will automatically disconnect lines and/or transformers, causing load to be shed.
Voltage stability: System is able to maintain the proper voltages needed to serve load.
W
Watt: The unit of electric power. The rate of work represented by a current of one ampere under a pressure of one volt in circuit having a unity power factor.
X
Y
Z
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