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SPDC Terms V-Z
VALVE ARRESTER
An arrester that includes a valve elements.
[C62.1–1989 & C62.2–1987 & C62.11–1987 & C62.22–1991]
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.
[C62.1–1989 & C62.2–1987 & C62.11–1987 & C62.22–1991]
VARIATION OF HOLDING CURRENT WITH TEMPERATURE
The change in holding current, IH, with changes in temperature. It is shown as a graph.
[C62.37–1996]
VARISTOR VOLTAGE
Voltage across the varistor measured at a given current, IX.
[C62.33–1989]
VENT
An intentional opening for the escape of gases to the outside.
[C62.1–1989 & C62.11–1987]
VIRTUAL DURATION OF WAVE FRONT (OF AN IMPULSE)
The virtual value for the duration of the wave front is as follows:
(1)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.
(2)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.
(3)For current waves, 1.25 times the time for the current to increase from 10% to 90% of crest value.
[C62.1–1989 & C62.2–1987 & C62.11–1987 & C62.22–1991 & C62.37–1996 & STD. 100-2000]
(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.
[C62.37–1996]
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.
[C62.1–1989 & C62.2–1987 & C62.11–1987 & C62.22–1991 & C62.37–1996]
VOLTAGE CLAMPING RATIO (VARISTOR)
A figure of merit measure of the varistor clamping effectiveness as defined by the symbols VC/Vm(ac), VC/Vm(dc).
[C62.33–1989]
VOLTAGE CLAMPING RATIO
A figure of merit, which determines the clamping effectiveness of an avalanche surge suppressor as defined by the symbols.
[C62.35–1987]
VOLTAGE OVERSHOOT (VARISTOR)
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.
[C62.33–1989]
VOLTAGE OVERSHOOT
The excess voltage above the clamping voltage (VC) of the device for a given current that occurs when current waves of less than 10 µs virtual front duration are applied. This value may be expressed as a percentage of the clamping voltage (VC) for a 10 X 1000 µs current wave.
[C62.35–1987]
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.
[C62.1–1989]
VOLTAGE TO GROUND
The voltage between any live conductor of a circuit and the earth.
NOTE: Where safety considerations are involved, the voltage to ground that may occur in an ungrounded circuit is usually the highest voltage normally existing between the conductors of the circuit, but in special circumstances higher voltages may occur.
[STD 32–1990]
VULNERABILITY
The characteristic of a device for being damaged by an external influence, such as a surge.
[C62.45–1992]
WAVEFORM
A manifestation or representation (that is, graph, plot, oscilloscope presentation, equation(s), table of co-ordinate or statistical data, etcetera) or a visualization of a wave, pulse or transition.
[C62.37–1996 & STD. 100-2000]
WAVEFRONT (OF A SURGE OR IMPULSE)
That part (of an impulse) which occurs prior to the crest value.
[C62.1–1989 & C62.11–1987 & C62.22–1991 & C62.37–1996 & STD. 100-2000]
WAVE SHAPE (OF AN IMPULSE TEST WAVE)
The graph of the wave as a function of time.
[C62.1–1989 & C62.2–1987 & C62.11–1987 & C62.22–1991 & C62.37–1996 & STD. 100-2000]
WAVE SHAPE DESIGNATION (OF AN IMPULSE)
The wave shape of an impulse (other than rectangular) of a current or voltage as designated by a combination of two numbers. The first, an index of the wave front, is the virtual duration of the wave front in microseconds. The second, an index of the wave tail, is the time in microseconds from virtual zero to the instant at which one-half of the crest value is reached on the wave tail. Examples are 1.2/50 and 8/20 waves.
[C62.1–1989 & C62.2–1987 & C62.11–1987 & C62.37–1996]
The wave shape of a rectangular impulse of current or voltage is designated by two numbers. The first designates the minimum value of current or voltage that is sustained for the time in microseconds designated by the second number. An example is the 75 A X 1000 µs wave.
[C62.2–1987 & C62.22–1991 & C62.37–1996]
WAVE SHAPE OF A RECTANGULAR IMPULSE OF CURRENT OR VOLTAGE
This wave is designated by two numbers. The first designates the minimum value of current or voltage which is sustained for the time in microseconds designated by the second number. An example is the 75 A X l000 µs wave.
[C62.1–1989]
WAVE TAIL (OF AN IMPULSE)
That part between the crest value and the end of the impulse.
[C62.1–1989 & C62.2–1987 & C62.11–1987 & C62.22–1991 & C62.37–1996 & STD. 100-2000]
WAVE
The variation with time of current, potential, or power at any point in an electric circuit.
[C62.1–1989 & C62.11–1987 & C62.37–1996 & STD. 100-2000]
WITHSTAND VOLTAGES
The voltage that electric equipment is capable of withstanding without failure or disruptive discharge when tested under specified conditions; see ANSI C92.1–1982
[C62.2–1987 & C62.22–1991]
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