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SPDC Terms I-L
IMPEDANCE GROUNDED
Grounded through impedance.
NOTE: The components of the impedance need not be at the same location.
[STD 32–1990]
IMPEDANCE VOLTAGE
Comprises an effective resistance component corresponding to the impedance losses, and a reactance component corresponding to the flux linkages of the winding.
[STD 32–1990]
IMPULSE
A surge of unidirectional polarity.
[C62.1–1989 & C62.2–1987 & C62.11–1987 & C62.22–1987 & 62.37–1996 & STD. 100-2000]
IMPULSE FLASHOVER VOLTAGE
The crest voltage of an impulse causing a complete disruptive discharge through the air between electrodes of a test specimen.
[STD 32–1990]
IMPULSE PROTECTIVE LEVEL
For a defined wave shape, the higher of the maximum sparkover value or the corresponding discharge-voltage value.
[C62.11–1987]
IMPULSE PROTECTIVE VOLT-TIME CHARACTERISTIC
The discharge-voltage time response of the device to impulses of a designated wave shape and polarity, but of varying magnitudes.
[C62.11–1987]
IMPULSE RESET TIME
t(Reset)
The time taken for a device to switch back into the off-state, in the presence of a specified value of dc short-circuit current, after being switched into the on state by a specified impulse.
[C62.37–1996]
IMPULSE SPARKOVER VOLTAGE
The highest value of voltage attained by an impulse of a designated wave shape and polarity applied across the terminals of an arrester (that will cause sparkover) prior to the flow of discharge current. Sometimes referred to as surge or impulse breakdown voltage.
[C62.31–1987 & C62.32–1987 & C62.1–1989 & (C62.11–1987)]
IMPULSE SPARKOVER VOLTAGE-TIME CURVE (ARRESTER)
A curve that relates the impulse sparkover voltage to the time to sparkover.
[C62.31–1987]
IMPULSE SPARKOVER VOLT-TIME CHARACTERISTIC
The (gap) sparkover response of the device to impulses of a designated wave shape and polarity, but of varying magnitudes.
NOTE: For an arrester, this characteristic is shown by a graph of values of crest voltage plotted against time to
sparkover.
[C62.1–1989 & (C62.11–1987)]
IMPULSE TESTS
Dielectric tests in which the voltage applied is an impulse voltage of specified wave shape. The wave shape of an impulse test wave is the graph of the wave as a function of time or distance.
NOTE: It is customary in practice to express the wave shape by a combination of two numbers, the first part of which represents the wave front and the second the time between the beginning of the impulse and the instant at which one-half crest value is reached on the wave tail, both values being expressed in microseconds, such as a 1.2 x 50 microsecond wave.
[STD 32–1990]
IMPULSE WAVE
A unidirectional wave of current or voltage of very short duration containing no appreciable oscillatory components.
NOTE - In the case of the 8/20 wave an opposite polarity wave tail underswing of up to 30% is allowed.
[C62.37–1996 & STD. 100-2000]
IMPULSE WITHSTAND VOLTAGE
The crest value of an applied impulse voltage which does not cause a flashover, puncture, or disruptive discharge on the test specimen.
[STD 32–1990]
The crest value of an impulse that, under specified conditions, can be applied without causing a disruptive discharge.
[C62.1–1989 & C62.11–1987]
INCREMENTAL SURGE RESISTANCE
RS = (VC2 - VC1)/(Ipp1 - Ipp2)
Resistance composed of thermal and nonlinear avalanche characteristics calculated between two instantaneous sets of values for peak pulse current (Ipp) and clamping voltage (VC) with a specified waveform.
[C62.35–1987]
INDIRECT ESD EVENT
An ESD event taking place between an intruder and a receptor, in proximity to equipment which is the victim.
[C62.47–1992]
INDOOR ARRESTER
An arrester that, because of its construction, shall (must) be protected from the weather.
[C62.1–1989 & (C62.11–1987)]
INDUCED-POTENTIAL TEST
A dielectric test in which the test voltage is an alternating voltage of suitable frequency, applied or induced between the terminals.
[STD 32–1990]
INERT GAS-PRESSURE SYSTEM
A method of oil preservation in which the interior of the tank is sealed from the atmosphere, over the temperature range specified, by means of a positive pressure of inert gas maintained from a separate inert-gas source and reducing-valve system.
[STD 32–1990]
INHIBITED OIL
Mineral transformer oil to which a synthetic oxidation inhibitor has been added.
[STD 32–1990]
INITIAL CURRENT PULSE
The sub-nanosecond rise time, and <1 to perhaps 3 nanosecond duration pulse that can occur at the start of the current wave from an ESD. Also called initial pulse, initial spike and fast discharge mode. Its leading edge is the initial slope.
[C62.47–1992]
INITIAL SLOPE
The slope, in Amps per nanosecond (A/ns), which occurs at the start of the ESD current wave. Also termed rising slope.
[C62.47–1992]
INSULATION CLASS (OF A GROUNDING DEVICE)
A number that defines the insulation levels of the device.
[STD 32–1990]
INSULATION LEVEL
A combination of voltage values (both power-frequency and impulse) that characterize the insulation of an equipment with regard to its capability of withstanding dielectric stresses.
[C62.22–1991]
INSULATION RESISTANCE
The equivalent insulation resistance of the device, computed by: VD / ID
[C62.37–1996]
INTRUDER ELECTRODE GEOMETRY
The size and shape of that surface of the intruder, termed the intruder electrode, at which the ESD takes place.
[C62.47–1992]
INTRUDER
The body which is in motion in an ESD event. The intruder is usually but not necessarily charged relative to its surroundings. It is always at a potential different from that of the receptor.
[C62.47–1992]
IONIZATION CURRENT
The electric current resulting from the movement of electric charges in an ionized medium, under the influence of an applied electric field.
[C62.1–1989 & C62.11–1987]
IONIZATION VOLTAGE
A high-frequency voltage appearing at the terminals of an arrester, generated by all sources, but particularly by ionization current within the arrester, when a power-frequency voltage is applied across the terminals.
[C62.1–1989 & C62.11–1987]
LET-THROUGH SPARKOVER
A measure of the highest lightning surge an arrester is likely to withstand without sparkover in 3 µs or less. The value determined by a 1.2/50 µs impulse sparkover test: see ANSI/IEEE C62.1–1984
[C62.2–1987]
LIFETIME RATED PULSE CURRENTS (VARISTOR)
Derated values of Itm for impulse durations exceeding that of an 8/20 µs wave shape, and for multiple pulses which may be applied over device's rated lifetime.
[C62.33–1989]
LIFETIME RATED PULSE CURRENTS
Rated values of the peak impulse current, Ipp, as a function of the number of pulses and wave shape, which may be applied over the device rated lifetime.
[C62.37–1996]
LIGHTNING OVERVOLTAGE
The crest voltage appearing across an arrester or insulation caused by a lightning surge.
[C62.2–1987 & C62.22–1991]
LIGHTNING SURGE
A transient electric disturbance in an electric circuit caused by lightning.
[C62.1–1989 & C62.2–1987 & C62.11–1987 & C62.22–1991]
LIGHTNING
An electric discharge that occurs in the atmosphere between clouds or between clouds and ground.
[C62.1–1989 & C62.11–1987]
LINE END (OF A NEUTRAL GROUNDING DEVICE)
The end or terminal of the device that is connected to the line circuit directly or through another device.
[STD 32–1990]
LINE TERMINAL
The conducting part provided for connecting the arrester to the circuit conductor.
[C62.11–1987]
The conducting part provided for connecting the arrester to the circuit conductor.
NOTE: When a line terminal is not supplied as an integral part of the arrester, and the series gap is obtained by providing a specified air clearance between the line end of the arrester and a conductor, or arcing electrode, etc., the words line terminal used in the definition refer to the conducting part that is at line potential and that is used as the line electrode of the series gap.
[C62.1–1989]
LONGITUDINAL (COMMON) MODE VOLTAGE
The voltage common to all conductors of a group as measured between that group at a given location and an arbitrary reference (usually earth).
[C62.31–1987]
LOSSES (OF A GROUNDING DEVICE)
The I²R loss in the windings, core loss, dielectric loss, loss due to stray magnetic fluxes in windings and other metallic parts of the device, and, in cases involving parallel windings, losses due to circulating currents.
NOTES: (1) The losses as here defined do not include any losses produced by the device in adjacent apparatus or materials not a part of the device.
(2) Losses will normally be considered at the rated thermal current but in some cases may be required at other current ratings, if more than one rating is specified, or at no load, as for grounding transformers. The losses may be given at 25 ºC or 75 ºC.
[STD 32–1990]
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