353 articles
Vacuum interrupter
A vacuum interrupter is a switching component for power circuits in which separable contacts operate in a vacuum, extinguishing the arc without air, oil, or SF₆.
Variable autotransformer
A variable autotransformer, commonly called a Variac, is a transformer with a sliding brush that adjusts AC output voltage continuously from zero to above the input.
Vault transformer
A vault transformer is a liquid-immersed, three-phase distribution transformer installed in underground vaults, where it steps a medium-voltage feed down to 600 V or less to supply secondary networks through network protectors.
Viking Link
Viking Link is a 1.4 GW HVDC electricity interconnector between Bicker Fen in Lincolnshire and Revsing in Denmark, the world's longest land and subsea interconnector, operational since 2023.
Virtual Power Plant
A virtual power plant (VPP) is a group of dispersed energy resources like rooftop solar, batteries, and electric vehicles coordinated by software to act as a single power plant.
Volt/var optimization
Volt/var optimization (VVO) is a distribution-engineering method that coordinates voltage regulators, load tap changers, and capacitor banks to minimize power losses and keep feeder voltages within limits.
Voltage flicker meter
A voltage flicker meter, or flickermeter, is an instrument that converts rapid mains voltage fluctuations into indices of perceived light flicker, as specified by the international standard IEC 61000-4-15.
Voltage fluctuation
Voltage fluctuation is a power quality disturbance, a continuous variation of RMS voltage caused by arc furnaces, welders, and rapidly changing loads, and linked to flicker.
Voltage sag
Voltage sag, also called a voltage dip, is a short reduction in AC voltage to between 10 and 90 percent of nominal, lasting from half a cycle to 1 minute.
Voltage spike
A voltage spike is a short, high-magnitude transient rise in voltage on an electrical circuit, lasting microseconds to milliseconds and often reaching tens of kilovolts, caused by lightning, switching, or faults.
Voltage stability
Voltage stability is the ability of a power system to maintain steady, acceptable voltages at all buses after a disturbance; its loss can cause cascading blackouts.
Voltage stability analysis
Voltage stability analysis is a power systems engineering method for assessing whether a grid can maintain acceptable voltages, identifying conditions under which voltage collapse would begin.
Voltage swell
A voltage swell is a short-duration rise in RMS voltage to 110% to 180% of nominal lasting up to one minute, classified by IEEE 1159 as a power quality problem.
Voltage transformer
A voltage transformer, also called a potential transformer, is an instrument transformer that supplies meters and protective relays with an accurate scaled replica of system voltage.
Voltage unbalance
Voltage unbalance, also called voltage imbalance, is a power quality condition in three-phase electrical systems where voltages differ in magnitude or deviate from their ideal 120-degree phase angles.
Walsin Lihwa
Walsin Lihwa Corporation (华新丽华) is a Taiwanese manufacturer of wires, cables, and stainless steel, founded in 1966 as a power wire maker and now a leading cable company in Greater China.
War of the currents
The War of the currents was the late-1880s American rivalry between Thomas Edison's direct current and George Westinghouse's alternating current, which prevailed after the 1893 Chicago World's Fair.
Water treeing
Water treeing is a degradation process in polymeric power cable insulation, chiefly XLPE, where tree-shaped regions of water-filled microcavities grow slowly under an alternating electric field.
Wide area measurement system
A wide area measurement system (WAMS) is a power-grid infrastructure that collects GPS time-synchronized measurements from across a large transmission network, complementing SCADA with a real-time system-wide view.
Zero-sequence current
Zero-sequence current (ground or residual current) is a component of three-phase AC systems where three currents are equal in magnitude and phase, passing through neutral or earth paths.
Zhangbei converter station
The Zhangbei converter station is the sending end of China's Zhangbei flexible DC grid, delivering wind and solar power from Hebei to Beijing since 2020.
Zhundong converter station
The Zhundong converter station, also called the Changji converter station, sends ±1100 kV direct current from Xinjiang to Anhui over 3324 km, the world's highest-voltage HVDC link.
Zigzag transformer
A zigzag transformer, also called an interconnected-star or Z-type transformer, is a three-phase grounding transformer used to create a neutral point on delta-connected, three-wire systems with no natural neutral.