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Tennessee Valley Authority (TVA)

TVA is owned by the United States government. TVA provides wholesale electricity in seven southern states as well as services such as flood cont …

Three-part communication

Three-part communication is a process used in the gas and electric industries to limit errors due to lack of effective communication.

Three-phase power

Three-phase power refers to an electrical system that has three voltage or current curves.

Three-phase service

Three-phase service is typically provided to larger commercial and industrial customers. Any customer with a motor larger than 10 horsepower is …

Tidal hydropower plants

Tidal hydropower plants, also called tidal barrage plants, depend on dams across an estuary or tidal channel that trap incoming tidal flows and …

Time-of-use rate

Time-of-use rates change the price of electricity according to the time of day in which it is consumed.

Trading arrangements

Trading arrangements define how business transactions are performed to allow energy, reserves, and other ancillary services to be acquired by ma …


A transformer is a device that changes the voltage of electricity.

Transmission company

Transmission companies, or transcos, are independent owners of transmission facilities. They are commonly investor-owned, and like IOUs operate …

Transmission management system (TMS)

A transmission management system, commonly called a TMS, is a suite of software tools used by system operators to monitor and manage the transmi …

Transmission outage

Transmission outages can be caused by a variety of reasons: weather events, lightning, fires, vandalism, terrorism, failure of substation or cir …

Transmission owner (TO)

In markets where the system operations function has been moved to an Independent System Operator (ISO), the term transmission owner, or TO, is u …

Transmission rights

Transmission rights are used by generators and/or marketers to ensure delivery of power to a point of sale.

Transmission substation

Transmission substations connect two or more transmission lines.

Transmission System Operator

A transmission system operator (TSO) is a stand-alone natural gas or electric transmission company that owns transmission facilities and provide …


A turbine is a machine in which the kinetic energy of a moving fluid causes a series of blades to spin, thus converting kinetic energy to mechan …

U.S. energy flow

There are various sources of energy consumed in the United States and different uses for each.

Unbundled service

Unbundled service happens when the distribution company provides the delivery service but another entity such as a marketer or aggregator provid …

Utility distribution company (UDC)

A utility distribution company (UDC) is an electric utility that provides distribution services.

Vertically integrated monopoly utility electric market model

Under the vertically integrated monopoly utility model, generation, transmission, distribution, retail sales, and system operations functions an …