How Does Electricity Work?

Producing and delivering reliable electricity to customers is complex. We must generate, transmit, and distribute electricity. Traveling at almost the speed of light – 186,000 miles a second – electricity arrives where it’s demanded the moment you click on the TV, flip a light switch, or press the buttons on your microwave — at almost the same moment that it’s produced.

Glossary of Electricity Terms

Access – The contracted right to use an electrical system to transfer electrical energy.

Alternating current (AC) – Commonly used electrical current that reverses its direction of flow 60 times per second.

Ampere (amp or A) – A unit of electric current or the amount of electric charge per second.

Baseload – The minimum amount of power that a utility must make available to its customers or the amount of power required to meet minimum demands based on reasonable expectations of customer requirements.

Blackout – A total power failure over a large area usually caused by the failure of the generation, transmission or distribution system.

Brownout – The partial reduction of electrical voltages caused by customer demand being higher than anticipated or by the failure of the generation, transmission or distribution system. A brownout results in lights dimming and motor-driven devices slowing down.

Capacitor banks – System elements (equipment) that support the voltages necessary to provide reliable service to customers.

Capacity – The load-carrying ability, expressed in megawatts (MW), of generation, transmission or other electrical equipment.

Circuit – A continuous electrical path along which electricity can flow from a source, like a power plant, to where it is used, like a home. A typical transmission circuit consists of three phases with each phase on a separate set of conductors.

Conductivity – A measure of a material’s ability to conduct/transmit an electric charge.

Conductor – A wire made up of multiple aluminum strands supported by a steel core that together carry electricity. A bundled conductor is two or more conductors connected together to increase the capacity of a transmission line.

Conservation – Practice of decreasing the quantity of energy used while achieving a similar outcome. Generally, conservation reduces the energy consumption and energy demand per capita, and thus offsets the growth in energy supply needed to keep up with population growth.

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.

Current – The movement or flow of electricity. Current is measured in amperes.

Demand – The rate at which electric energy is delivered to or by a system or part of a system at a given instant or averaged over any designated interval of time. Demand is generally expressed in kilowatts (kW) or megawatts (MW).

Demand-side management (DSM) – Actions that influence the quantity or patterns of use of energy consumed by end users, such as actions targeting reduction of peak demand during periods when energy supply systems are constrained.

Direct current (DC) – The constant flow of electric charge.

Distributed generation – Small-scale generation located close to homes, farms and businesses where the power is needed, using traditional as well as renewable sources, like wind and biomass.

Distribution – An interconnected group of lines and associated equipment for the local delivery of low voltage electricity between the transmission network and end users.

Double circuit – Two sets of independent circuits with each circuit made up of three sets of conductors.

Dual fuel capacity – The capacity of an energy burning facility to use more than one kind of fuel alternatively.

Easement – An easement is a permanent right authorizing a person or party to use the land or property of another for a particular purpose. In the case of CapX2020, this means acquiring certain rights to build and maintain a transmission line. Landowners are paid a fair price for the easement and can continue to use the land for most purposes, although some restrictions are included in the agreement.

Efficiency – Using less energy/electricity to perform the same function.

Electric and magnetic fields (EMF) – Invisible lines of force that surround any electrical appliance or wire that is conducting electricity. The balance of scientific evidence indicates that exposure to EMF does not negatively impact health.

Energy source – Raw materials that are converted to electricity through chemical, mechanical or other means. Energy sources include coal, gas, water, wind, biomass and solar.

FERC – Federal Energy Regulatory Commission; an independent agency that regulates the interstate transmission of natural gas, oil and electricity.

Generation – The act of converting various forms of energy input (thermal, mechanical, chemical and/or nuclear energy) into electric power. The amount of electric energy produced is usually expressed in kilowatt hours (kWh) or megawatt hours (MWh).

Grid – The interconnected transmission and distribution networks operated by electrical utilities that deliver electricity to end users.

Heavy loads – High volume of electricity flowing on a line, transformer or other equipment to meet a high demand for electricity, usually during hot weather.

Import/export – Ability of the transmission system to bring power into or out of an area in order to serve load.

Insulator – An object made of a material like glass, porcelain or composite polymer that is a poor conductor of electricity. Insulators are used to attach conductors to the transmission structure and to prevent electricity from short circuiting from the wire to the structure.

Kilovolt (kV) – A kilovolt is equal to one thousand volts (V).

Kilowatt (kW) – A unit of electrical power equal to one thousand watts.

Kilowatt hour (kWh) – One kWh represents the use of one thousands watts of electricity for one hour. Put another way, one kWh equals 10 100-watt light bulbs burning simultaneously for one hour.

Load – All the devices that consume electricity and make up the total demand for power at any given moment or the total power drawn from the system.

Load management – The management of load patterns in order to better utilize the facilities of the system. Load management generally attempts to shift load from peak use periods to other periods of the day or year when demand is lighter.

Loading relief – A system change or reinforcement that results in lower power flows on equipment that is heavily loaded or overloaded.

Low voltages – A situation that can occur in parts of the system that are heavily loaded or that have high motor loads. Think of a clothesline that is pulled taut when nothing is hanging on it but that tends to sag when more and more clothes (i.e. loads or motors) are attached.

Margin – The difference between (1) generation resources and electric demand or (2) the capacity of a transmission line and the power flowing on that line. Margin is usually expressed in megawatts (MW).

Megawatt (MW) – A megawatt is equal to one million watts.

Megawatt-hour (MWh) – One MWh equals 1 million watt hours.

MISO – Midcontinent Independent System Operator; a not-for-profit corporation of electric transmission owners, covering a 15 state region from the Dakotas to Kentucky. MISO administers and manages the transmission of electricity within its region.

National Environmental Policy Act (NEPA) – Law requiring the consideration of the environmental impacts of major federal actions and the preparation of environmental impact statements (EISs) that discuss these impacts and possible alternatives. Public participation also is required in the EIS process.

North American Reliability Council (NERC) - a not-for-profit corporation formed by the electric utility industry in 1968 to ensure 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. NERC’s planning standards apply primarily to the bulk electric system, meaning the electric generation resources, transmission lines and interconnections generally operated above 100-kV.

Network – A system of interconnected lines and electrical equipment.

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, possibly as a result of planned for maintenance or unplanned (forced) problems caused by weather or equipment failures.

Overloads – Occur when power flowing through wires or equipment is more than they can carry without incurring damage.

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 a 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 direct connection.

Phase – One element of a transmission circuit that has a distinct voltage and current. Each phase has maximum and minimum voltage peaks at different times than the other phases.

Power flows – Electricity moving through lines or other equipment.

Rebuild – Removing an existing line and replacing it with a new, higher capacity line.

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. It is the ability to deliver uninterrupted electricity to customers on demand and to withstand sudden disturbances such as short circuits or loss of system components.

Renewable resource – A power source that is renewed by nature, such as solar, wind, hydroelectric, geothermal, biomass or similar sources of energy.

Reserve – The difference between an electric system's capability and the expected peak demand for electricity.

Right-of-Way (ROW) – A right-of-way is the land area legally acquired for a specific purpose, such as the placement of transmission facilities and for maintenance.

Regional Transmission Organization (RTO) - organization that oversees and coordinates regional transmission planning and services to facilitate fair and competitive wholesale markets. MISO is a Regional Transmission Organization.

Serve load – The ability to reliably deliver the amounts of electricity necessary to match customer needs at any given time.

Service area – Territory in which a utility is required to, or has the right to, supply service to customers.

Shield wire – A wire connected directly to the top of a transmission structure to protect conductors carrying electricity from a direct lightning strike, minimizing the possibility of power outages.

Single circuit – A circuit with three sets of conductors.

Stability – The ability of an electric system to maintain a state of equilibrium during normal and abnormal system conditions or disturbances.

Structures – Towers or poles that support transmission lines.

Substation – A facility that monitors and controls electrical power flows, uses high voltage circuit breakers to protect power lines and transforms voltage levels to meet the needs of end users.

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.

Transmission to distribution interconnection (T-D interconnection) - the place where distribution substations connect to the 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 from overheating or before it violates public safety requirements.

Thermal overloads – Power flows on lines or equipment that exceeds 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 change voltage levels.

Transmission – An interconnected group of lines and equipment for transporting electric energy in bulk on a high voltage power lines between power sources (e.g. power plants) and major substations where the voltage is ‘stepped down’ for distribution to customers. Transmission is considered to end where the line connects to a distribution station.

Uprates – Make the transmission system element able to carry more electricity than it is capable of currently. This can be done by increasing line clearances or replacing limiting pieces of equipment to enable the safe transport and delivery of more power.

Voltage – A type of ’pressure’ that drives electrical charges through a circuit. Higher voltage lines generally carry power longer distances.

Voltage collapse – Can occur when the voltage dips low and cannot recover quickly enough. In this situation, protective equipment will automatically disconnect lines and/or transformers, causing load to be shed.

Voltage stability – The system is able to maintain the proper voltages needed to serve load.

Watt (W) – Unit of power equal to volts x amps.

Watt-hour (Wh) – The total amount of energy used in one hour by a device that requires one watt of power for continuous operation.