SPDC Terms beginning with V

Terms and definitions extracted from current SPDC published documents
Click one of the capital letters above to advance the page to terms beginning with that letter.
valve arrester

An arrester that includes one or more valve elements.
[C62.22-2009]

valve arrester

An arrester that includes one or more valve elements.
[C62.11-2005]

valve element

A resistor that because of its nonlinear current-voltage characteristic, limits the voltage across the arrester terminals during the flow of discharge current and contributes to the limitation of follow current at normal power-frequency voltage.
[C62.22-2009]

valve element

A resistor that because of its nonlinear current-voltage characteristic, limits the voltage across the arrester terminals during the flow of discharge current and contributes to the limitation of follow current at normal power-frequency voltage.
[C62.11-2005]

variation of holding current with temperature

The change in holding current, IH, with changes in temperature. It is shown as a graph.
[62.37-1996]

Varistor voltage

VX
Voltage across the varistor measured at a given current, IX.
[C62.33-1982]

vent

An intentional opening for the escape of gases to the outside.
[C62.11-2005]

very fast front voltage shape

This category has not been standardized at this time.
[C62.82.1-2010]

very fast front, short-duration overvoltage

A transient overvoltage in which a short duration, usually unidirectional, voltage is generated (often by GIS disconnect switch operation or when switching motors). High-frequency oscillations are often superimposed on the unidirectional wave.
[C62.82.1-2010]

virtual current chopping (rotating electric machinery)

The chopped interruption of current in the machine circuit by a superimposed high-frequency current induced from another phase and with a magnitude greater than the fundamental frequency current in the interrupted phase.
[C62.21-2003]

virtual duration of wave front (of an impulse)

The virtual value for the duration of the wave front is as follows:
a) For voltage waves with wave front durations less than 30 μs, either full or chopped on the front, crest, or tail, 1.67 times the time for the voltage to increase from 30% to 90% of its crest value.
b) For voltage waves with wave front durations of 30 μs or more, the time taken by the voltage to increase from actual zero to maximum crest value.
c) For current waves, 1.25 times the time for the current to increase from 10% to 90% of crest value.
[C62.22-2009]

virtual duration of wave front (of an impulse)

(A) For voltage waves with wave front duration less than 30 μs, either full or chopped on the front, crest, or tail, 1.67 times the time for the voltage to increase from 30% to 90% of its crest value.
(B) For voltage waves with wave front duration of 30 μs or more, the time taken by the voltage to increase from actual zero to maximum crest value.
(C) For current waves, 1.25 times the time for the current to increase from 10% to 90% of crest value.
[C62.11-2005]

virtual duration of wavefront (of an impulse)

The virtual value for the duration of the wavefront is as follows:
1) For voltage waves with wavefront duration less than 30 µs, either full or chopped on the front, crest, or tail, 1.67 times the time for the voltage to increase from 30% to 90% of its crest value.
2) For voltage waves with wavefront duration of 30 µs or more, the time taken by the voltage to increase from actual zero to maximum crest value.
3) For current waves, 1.25 times the time for the current to increase from 10% to 90% of crest value.
[62.37-1996]

virtual junction temperature

TJ
A theoretical temperature representing the temperature of the junction(s) calculated on the basis of a simplified model of the thermal and electrical behavior of the device.
[62.37-1996]

virtual zero point (of an impulse)

The intersection with the zero axis of a straight line drawn through points on the front of the current wave at 10% and 90% crest value, or through points on the front of the voltage wave at 30% and 90% crest value.
[62.37-1996]

virtual zero point (of an impulse)

The intersection with the time axis of a straight line drawn through points on the front of the current wave at 10% and 90% crest value or through points on the front of the voltage wave at 30% and 90% crest value.
[C62.22-2009]

virtual zero point (of an impulse)

The intersection with the time axis of a straight line drawn through points on the front of the current wave at 10% and 90% crest value, or through points on the front of the voltage wave at 30% and 90% crest value.
[C62.11-2005]

voltage clamping ratio (Varistor)

VC/Vpm
A figure of merit measure of the varistor clamping effectiveness as defined by the symbols VC/Vm(ac), VC/Vm(dc).
[C62.33-1982]

voltage overshoot (Varistor)

VOS
The excess voltage above the clamping voltage of the device for a given current that occurs when current waves of less than 8 µs virtual front duration are applied. This value may be expressed as a % of the clamping voltage (VC) for an 8/20 µs current wave.
[C62.33-1982]

voltage protection level

A parameter that characterizes the performance of the SPD in limiting the voltage across its terminals. This value shall be equal to or greater than the highest value measured in measured limiting voltage tests.
[C62.34-1996]

voltage rating

The designated maximum permissible operating voltage between its terminals at which an arrester is designed to perform its duty cycle. It is the voltage rating specified on the nameplate.
[C62.41.1-2002]

voltage shape

A waveform of a voltage impulse that has been standardized to define insulation strength. The standardized voltage shapes are as follows: power-frequency short-duration, standard switching impulse, standard lightning impulse, very fast front, standard chopped wave impulse, and front-of-wave lightning impulse.
[C62.82.1-2010]