Glossary terms beginning with V

Terms used within Transpower
Click one of the letters above to go to the page of all terms beginning with that letter.
vacuum circuit-breaker

A circuit-breaker in which the contacts open and close within a vacuum.

valve control unit

The valve control unit provides Power Supply Supervision for its thyristor. In case of loss of auxiliary voltage in the VCU the affected quadruple valve can not be controlled, and the converter is tripped. [ABB TR-LK-88-032 rev 3].

valve service platform

A power-operated elevating work platform used for servicing HVDC valves and valve-hall equipment.

valve-regulated cell (VRLA) (battery)

A cell which is closed under normal conditions but has an arrangement which allows the escape of gas if the internal pressure exceeds a predetermined value. Electrolyte is not added to this type of cell. [AS 2676, Part 1].

vented cells (battery)

Vented cells refer to those battery cells from which gas escapes during charging, such as Faure, Plante and Kathanode lead acid cells.

venting duct (surge arrester)

The vent for the over pressure relief device.

very high frequency

The frequency spectrum between 30 MHz and 300 MHz. The land mobile radio service uses a portion of this spectrum.

VF

Voice frequency

VHF

The frequency spectrum between 30 MHz and 300 MHz. The land mobile radio service uses a portion of this spectrum.

vibration damper

A device designed to reduce the amplitude of aeolian vibrations in transmission line conductors.

vll

This is the normal line to line voltage of the system.

voltage

Means the nominal potential difference between conductors or the nominal potential difference between a conductor and earth, whichever is applicable.

voltage collapse

A sudden and large decrease in the voltage of the electrical system. [GOSP glossary - IEC 50 (604-01-22)].

voltage detector

An approved device used to prove that equipment is de-energised prior to earthing.

voltage detector stick

An approved telescopic insulated stick for use with voltage detectors in all weathers.

voltage gradient

The difference in voltage between points spaced at unit distance.

voltage monitor

A device for monitoring the secondary voltages of capacitor voltage transformers.

voltage rating

The rated voltage of the equipment.

voltage reduction (power system)

A means of reducing power system load by lowering the supply voltage.

voltage support

Voltage is the electromotive force (pressure) that transfers power along transmission lines. In long transmission lines, this force may reduce too much by the time it reaches its destination, increasing the risk of voltage collapse. Equipment like capacitors, static var compensators and synchronous condensers are installed to provide reactive support by "propping up" the voltage to within an acceptable range.

voltage to CT influence

The effect of energised primary conductors that induces an error current in the secondary of a CT.

voltage transformer

An instrument transformer for obtaining measurements of a high voltage, by reducing it proportionately to a low voltage suitable for metering and protection purposes .

voltage transformer supervision

A device in a distance relay which will detect defects in VT secondary wiring.

VRLA

A cell which is closed under normal conditions but has an arrangement which allows the escape of gas if the internal pressure exceeds a predetermined value. Electrolyte is not added to this type of cell. [AS 2676, Part 1].

VSC

Voltage Source Converter - Transistor based high voltage power electronic converter.  Converts DC to AC and vice versa.

VT

An instrument transformer for obtaining measurements of a high voltage, by reducing it proportionately to a low voltage suitable for metering and protection purposes .

VTS

A device in a distance relay which will detect defects in VT secondary wiring.