901 articles
Transformer types
Transformer types are the classes of electrical transformers, distinguished by function, winding and core construction, and insulation and cooling, including distribution, power, instrument, and autotransformers.
Transgrid
Transgrid is the privately held company that operates the high voltage electricity transmission network in New South Wales and the Australian Capital Territory, covering about 11,500 kilometers of lines.
Transient recovery voltage
Transient recovery voltage (TRV) is the voltage that appears across a circuit breaker's terminals immediately after it interrupts a current, largely determining whether the breaker can clear a fault.
Transient stability
Transient stability, a branch of rotor angle stability also called large-disturbance angular stability, is a power system's ability to maintain synchronism through a severe disturbance, such as a transmission-line short circuit, and regain equilibrium afterward.
Transient stability analysis
Transient stability analysis is a power systems engineering method that determines whether a grid's synchronous generators remain in synchronism after a large disturbance, such as a short circuit.
Transmission Company of Nigeria
The Transmission Company of Nigeria (TCN) is the state-owned company that owns and operates Nigeria's national electricity transmission grid, created in 2005 from the unbundled PHCN.
Transmission tower
A transmission tower, also known as an electric pylon or by the German name Hochspannungsmast, is a tall structure, usually a steel lattice, that carries high-voltage conductors of an overhead transmission line.
TransnetBW
TransnetBW GmbH is the transmission system operator for the German state of Baden-Württemberg, operating its extra-high-voltage grid as one of four German TSOs and majority owned by EnBW.
Traveling wave fault location
Traveling wave fault location (TWFL) locates faults on power transmission lines by timing the wavefronts a fault launches, reaching accuracy of a few hundred meters on long lines.
Tri-State Generation and Transmission Association
Tri-State Generation and Transmission Association, Inc. is a not-for-profit wholesale electric cooperative, incorporated in Colorado in 1952, that supplies power to member utilities in Colorado, Nebraska, New Mexico, and Wyoming.
TSGENCO
TSGENCO, since renamed Telangana Power Generation Corporation Limited (TGGENCO), is the government-owned thermal and hydel generation company of Telangana, incorporated in May 2014 as a successor of undivided Andhra Pradesh's utilities.
Tunisian Company of Electricity and Gas
The Tunisian Company of Electricity and Gas (French: Société Tunisienne de l'Electricité et du Gaz, or STEG) is the state-owned utility producing and distributing electricity and natural gas across Tunisia, created in 1962.
Turkmenenergo
Turkmenenergo, officially the State Power Corporation, is the state-owned electric utility of Turkmenistan under the Ministry of Energy, operating the unified ring power grid and counterparty for electricity exports.
TV pickup
TV pickup is a sudden surge in electricity demand synchronized with breaks in popular TV programs, mainly in the United Kingdom, as millions of viewers boil kettles at once.
Two-phase electric power
Two-phase electric power, or two-phase power, is an AC polyphase system carrying two equal voltages 90 degrees apart, historically over four wires, displaced by three-phase for transmission.
U.P. Rajya Vidyut Utpadan Nigam
U.P. Rajya Vidyut Utpadan Nigam (UPRVUNL) is the wholly owned thermal power generation company of the Government of Uttar Pradesh, India, incorporated in 1980 and operating coal-fired stations at Anpara, Obra, Parichha, and Harduaganj.
UK Power Networks
UK Power Networks (UKPN) is a British electricity distribution network operator serving London, the South East, and East of England, created in 2010 and sold to ENGIE in 2026.
Ukrenergo
Ukrenergo (НЕК «Укренерго») is Ukraine's sole state-owned electricity transmission system operator, established in 1998 to control and run the main power grid, which it synchronized with Continental Europe in 2023.
Ultranet (HVDC transmission project)
Ultranet is a 2,000-megawatt high-voltage direct current transmission line under construction in Germany, running about 340 kilometers from Osterath to Philippsburg, due operational at the end of 2026.
Under-frequency load shedding
Under-frequency load shedding (UFLS) is a last-resort emergency protection scheme that automatically disconnects predetermined blocks of load when power system frequency falls below thresholds, arresting decline and preventing cascading blackouts.
Undergrounding
Undergrounding is the practice of placing electric power lines below ground instead of on poles, improving reliability and reducing wildfire risk at much higher cost.
Undervoltage load shedding
Undervoltage load shedding (UVLS) is an emergency control measure in electric power systems that automatically disconnects selected loads when bus voltages fall below preset thresholds, arresting voltage instability and preventing collapse.
Unified power flow controller
The unified power flow controller (UPFC) is a FACTS device that independently controls active and reactive power on a transmission line by injecting a series voltage.
Union Electric
Union Electric Company is an investor-owned electric utility founded in 1902 in St. Louis, Missouri, now doing business as Ameren Missouri and serving about 1.2 million customers.
Unión Eléctrica de Cuba
Unión Eléctrica de Cuba (UNE) is Cuba's state-owned electric utility, operating the national power system under the Ministry of Energy and Mines and facing repeated total grid collapses since 2024.
Unipro
Unipro (ПАО «Юнипро», Unipro PJSC) is a Russian thermal power generation company that operates five power plants with about 11.3 GW of capacity, and is majority-owned by Germany's Uniper SE.
Unit commitment
Unit commitment is an optimization method in power systems scheduling that decides which generators to switch on and at what output to meet demand at minimum cost.
Unit protection
Unit protection is power system protection that operates only for faults inside a clearly defined zone, such as a transformer or busbar, never for faults outside it.
Utility frequency
Utility frequency, also called mains frequency, is the rate at which alternating current in a power grid oscillates: 50 Hz in most of the world, 60 Hz in North America.
Utility pole
A utility pole, also known as a telephone pole or power pole, is a column, most often treated wood, supporting overhead power lines, communication cables, and streetlights.