Alberta Electric System Operator (AESO)

The Alberta Electric System Operator (AESO) is the independent, not-for-profit organization responsible for the safe, reliable and economic planning and operation of the Alberta electric system.

Alberta Utilities Commission (AUC)

The Alberta Utilities Commission (AUC) ensures the fair and responsible delivery of Alberta’s utility services. AltaLink submits applications for new transmission projects to the AUC and the AUC reviews them in a public process.

Alternating Current (AC)

A current that flows alternately in one direction and then in the reverse direction. In North America, the standard for alternating current is 60 complete cycles each second. Such electricity is said to have a frequency of 60 hertz. Alternating current is used in power systems because it can be transmitted and distributed more economically than direct current.

Ancillary Services

Services necessary to support transmission of capacity and energy from resources to load while maintaining reliable operation of the transmission system.

Available Energy Capacity (AEC)

The amount of available energy on a transmission system.

Base Load

The minimum continuous load over a given period of time. Base load generating stations operate essentially at full output whenever possible.

Bulk Electricity

Large amounts of electric power at transmission voltages, generally to run industrial plants and operations.

Capacitor bank

Capacitor banks regulate the voltage within a substation and help ensure the safety and reliability of the electric system.


In the electric power industry, capacity has two meanings:

  1. System Capacity: The maximum power capability of a system. For example, a utility system might have a rated capacity of 5000 megawatts, or might sell 50 megawatts of capacity.
  2. Equipment Capacity: The maximum power capability of piece of equipment. For example, a generating unit might have a rated capacity of 50 megawatts.


A circuit is a group of wires that electricity flows through. The wires are strung along power line structures. Transmission line structures can be described as single or double circuit. In a single circuit transmission line, three sets of wires are strung along the transmission structures. In a double circuit transmission line, six sets of wires are strung along the transmission structures.

Circuit breaker

Circuit breakers are electrical switches inside a substation that protect substation equipment. Circuit breakers help ensure the safety and reliability of the electric system.

Conventional Generation

Electricity that is produced at a generating station where the prime movers are driven by gases or steam produced by burning fossil fuels.


The flow of electricity in a conductor. Current is measured in amperes.


Deregulation is the process by which governments removes selected regulations on business in order to (in theory) encourage the efficient operation of markets. The theory is that less regulation will lead to a raised level of competitiveness, therefore higher productivity, more efficiency and lower prices overall.

Direct Current (DC)

Current that flows continuously in the same direction (as opposed to alternating current). The current supplied from a battery is direct current.


The process of transporting electric energy from the high voltage transmission grid directly to retail customers, generally on lines of 25 kV or less.

Distribution line

After transmission lines bring the electricity from power plants to substations and the voltage is reduced, distribution lines carry the lower voltage electricity to your homes, farms and businesses.

EHSMS (Environment, Health and Safety Management System)

The EHSMS aligns with the International Standards Organization (ISO) 14001:2015 Standard for Environmental Management Systems and the ISO 45001 Standard for Occupational Health and Safety Management Systems to help employees safely perform their job and protect the environment.

Electric grid

Alberta's electric grid is comprised of power plants, thousands of kilometres of power lines (high-voltage transmission lines and lower voltage distribution lines) and hundreds of substations. The electric grid works behind the scenes 24 hours a day to keep your lights on.

Electrical Energy

The quantity of electricity delivered over a period of time. The commonly used unit of electrical energy is the kilowatt-hour (kWh).

Electrical Power

The rate of delivery of electrical energy and the most frequently used measure of capacity. The basic unit is the kilowatt (kW).


The transfer and return of electricity from one utility to another at different time periods or seasons to achieve a more economic or efficient overall system operation. Such transfers are possible because of differences in electricity demand, generation resource capability or system operating characteristics.

Facilities Application

AltaLink submits Facilities Applications to the AUC for review. A Facilities Application describes how AltaLink proposes to meet the requirement for a transmission project. It includes routing details, results of the participant involvement program and technical details. Facilities Applications must be approved by the AUC before construction can begin.

Facilities Study

An engineering study conducted by the Transmission Facility Owner to determine the required modifications to the grid, including the cost and scheduled completion date for such modifications, that will be required to provide the requested transmission service.

Fire Weather Index

The Fire Weather Index (FWI) is a numeric rating of fire intensity. It is used as a general index of fire danger throughout the forested areas of Canada.


The process of converting thermal, mechanical, chemical or nuclear energy into electric energy.


A network of electric power lines and connections.

Hertz (Hz)

The unit of frequency for alternating current. Formerly called cycles per second. The standard frequency for power supply in North America is 60 Hz.

Interconnected System

A system consisting of two or more individual power systems connected together by tie lines.

Intertie (Interutility Tieline)

Transmission circuit used to tie or inter-connect two load areas of two utility systems.


Independent System Operator.


The work required to produce one watt of power for one second, or one 'watt second' (W-s).

Kilovolt (kV)

A kilovolt is equal to one thousand volts and is commonly used when describing transmission and distribution lines. AltaLink's transmission lines range from 69 kV (69,000 volts) to 500 kV (500,000 volts). Light bulbs typically range from 120 to 300 volts.

Kilowatt (kW)

The commercial unit of electric power; 1000 watts. A kilowatt can best be visualized as the total amount of power needed to light ten 100 watt light bulbs.

Kilowatt hour (kWh)

The commercial unit of electric energy; 1000 watt hours. A kilowatt hour can best be visualized as the amount of electricity consumed by ten 100-watt light bulbs burning for an hour. One kilowatt hour is equal to 3.6 million joules.


The total amount of electricity required to meet customer demand at any moment. The load equation fluctuates depending on electricity use throughout any given day.

Load Factor

The ratio of the average load during a designated period to the peak or maximum load in that same period. Usually expressed in per cent.

Load Forecast

The anticipated amount of electricity required by customers in the future.

Megawatt (MW)

A unit of bulk power; 1000 kilowatts.

Megawatt hour (MW.h)

A unit of bulk energy; 1000 kilowatt hours

Need Study

An engineering study conducted by the Electric System Operator to determine the required modifications to the grid, including the cost, that will be required to meet the need of customers on the transmission system.

Needs Application

The AESO submits Needs Applications to the AUC for review. A Needs Application describes why a transmission project is required. The AUC may review a Needs Application at the same time it reviews a Facilities Application, or may review each application separately. The AUC must approve a Needs Application before construction can begin.

Point of Delivery (POD)

Point on the transmission provider's transmission system where the transmission grid connects to a receiving party for the delivery of electricity.

Point of Receipt (POR)

Point on the transmission provider's transmission system where the grid connects to a generator for the loading of electricity on to the transmission system.

Power plant

Power plants convert various forms of energy into electric power. The transmission system connects diverse sources of power generation including wind, high-efficiency coal, natural gas and more. The transmission system always meets the demand for power with the lowest-priced generation in the province, meaning you're powering your home with the most cost-effective power at any given time.

Power System

The interconnected facilities of an electrical utility. A power system includes the generation, transmission, distribution, transformation, and protective components necessary to provide service.

Radio Site

Typical radio sites house a telecommunications tower and a control building within a fenced enclosure. The telecommunications equipment transmits data to our system control centre, allowing us to monitor the operation of the electric system and ensure the safety and reliability of the system for our customers.


Regulators ensure voltages remain stable and do not fluctuate within a substation. Regulators help ensure the safety and reliability of the electric system.

Reserve Generating Capacity

The extra generating capacity required on any power system over and above the expected peak load. Such a reserve is required mainly for two reasons: (i) in case of an unexpected breakdown of generating equipment; (ii) in case the actual peak load is higher than forecast.


The right-of-way is a strip of land required for the construction and operation of a transmission line. A right-of-way refers to the physical space a transmission line encompasses including areas on either side of the line. 


Substations are the connection point between high-voltage transmission lines and the lower voltage power lines (called distribution lines) that connect directly to homes and businesses.

After a transmission line brings power to a substation, its voltage is reduced so it can be transported safely and efficiently to you.

Switchgear building

Switchgear buildings house electrical equipment like cables, switches and breakers. Switchgear buildings ensure the equipment is protected from potential weather damage helping to ensure a reliable source of electricity is available for years to come.

Switching station

Switching stations connect two or more transmission lines so power can be re-routed and transported across the province to where it's needed.

System Impact Study

An assessment by the transmission provider of: (i) the adequacy of the transmission system to accommodate a transmission request for either Firm Point-to-Point Transmission Service or Network Integration Transmission Service; and (ii) whether any additional costs may be incurred in order to provide transmission service

Telecommunications tower

Telecommunications towers support equipment that transmits data to our system control centre. This allows us to monitor the operation of the electric system and ensure the safety and reliability of the system for our customers.


Transformers step down the voltage in a substation so power can be distributed safely to your community through distribution lines. Transformers also step up the voltage so power can be transmitted through transmission lines.


Transmission lines make up Alberta's electric highway, linking the places where power is generated to where power is used. Transmission lines transport large amounts of power over long distances across the province. The transmission system connects diverse sources of power generation including wind, high-efficiency coal, natural gas and more.

Transmission Must Run (TMR)

Generation that was introduced to the Alberta market to support the over-burdened transmission system caused by the expanding demand of the southern region of the province.

Transmission System

The facilities owned, controlled or operated by the transmission provider that are used to provide transmission service.

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