AC standby power (Varistor)pes-spdc.org/system/files/filedepot/145/SPDC_glossary... · Web viewA AC standby power (Varistor) Pd Varistor ac power dissipation measured at rated rms

2012-05-18 SPDC Glossary

Glossary of Published IEEE PES SPDC Terms and Definitions

AAC standby power (Varistor)

Pd

Varistor ac power dissipation measured at rated rms voltage Vm(ac). [C62.33-1982]

anodeThe electrode by which current enters the thyristor, when the thyristor is in the on-state with the gate open-circuited.NOTE: This term does not apply to bi-directional thyristors.[62.37-1996]

anti-parallel (connection)A parallel combination of two semiconductor elements, where the main current entry electrode of one element connects to the main current exit electrode of the other element, allowing one element to pass current in one voltage polarity and the other element to pass current in the opposite voltage polarity. (syn: inverse-parallel connection in IEEE 100 )[C62.37.1-2000]

arc currentThe current that flows after breakdown when the circuit impedance allows a current that exceeds the glow-to-arc transition current. Syn:arc mode current.[C62.31-2006]

arc voltageThe voltage drop across the gas tube during arc current flow. Syn:arc mode voltage.[C62.31-2006]

arresterSee: surge arrester.[C62.22-2009]

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arresterSee: surge arrester.[C62.11-2005]

arrester discharge currentThe current that flows through an arrester resulting from an impinging surge.[C62.22-2009]

arrester discharge voltageThe voltage that appears across the terminals of an arrester during the passage of discharge current.[C62.22-2009]

arrester disconnectorA means for disconnecting an arrester in anticipation of, or after, a failure in order to prevent a permanent fault on the circuit and to give indication of a failed arrester.NOTE: Clearing of the fault current through the arrester during disconnection is generally done by the nearest source-side overcurrent-protective device. [C62.41.1-2002]

arrester disconnectorA means for disconnecting an arrester in anticipation of, or after, a failure in order to prevent a permanent fault on the circuit and to give indication of a failed arrester.NOTE: Clearing of the fault current through the arrester during disconnection is generally done by the nearest source side overcurrent-protective device.[C62.11-2005]

arrester duty cycle ratingThe designated maximum permissible root-mean-square (rms) value of power-frequency voltage between its line and ground terminals at which it is designed to perform its duty cycle.[C62.22-2009]

arrester unitAny section of a multi-unit arrester.[C62.11-2005]

arrester, deadfront typeAn arrester assembled in a shielded housing providing system insulation and conductive ground shield, intended to be installed in an enclosure for the protection of underground and pad-

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mounted distribution equipment and circuits.[C62.11-2005]

arrester, distribution, heavy duty classAn arrester normally used to protect overhead distribution systems exposed to severe lightning currents.[C62.11-2005]

arrester, distribution, light duty classAn arrester normally installed on and used to protect underground distribution systems where the major portion of the lightning stroke current is discharged by an arrester located at the overhead line/cable junction.[C62.11-2005]

arrester, distribution, normal duty classAn arrester normally used to protect overhead distribution systems exposed to normal lightning currents.[C62.11-2005]

arrester, liquid-immersed typeAn arrester designed for use immersed in an insulating liquid.[C62.11-2005]

arrester, riser pole typeAn arrester for pole mounting normally used to protect underground distribution cable and equipment.[C62.11-2005]

atmospheric correction factorA factor applied to account for the difference between the atmospheric conditions in service and the standard atmospheric conditions. (In terms of this standard, it applies to external insulation only.)[C62.82.1-2010]

avalanche breakdown diode (ABD)A transient voltage suppressor that is a semiconductor diode with a single P-N junction or multiple, non-interactive P-N junctions, which may operate in either direction and employs its breakdown characteristics as part of its function.NOTE—The ABD is also known as an avalanche-junction transient voltage suppressor, silicon

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avalanche diode (SAD) or transient voltage suppressor (TVS).[C62.35-2010]

Bback filter

A filter inserted in the power line feeding an equipment to be surge tested; this filter has a dual purpose: (1) of preventing the applied surge from being fed back to the power source where it might cause damage. (2) of eliminating loading effects of the power source on the surge generator. [C62.41.1-2002]

back flashoverA flashover of insulation resulting from a lightning stroke to part of a network or electric installation that is normally at ground potential[C62.23-1995]

back flashover (lightning)A flashover of insulation resulting from a lightning stroke to part of a network or electric installation that is normally at ground potential. [C62.41.1-2002]

back-up air gap devicesAn air gap device connected in parallel with a sealed gas tube device, having a higher breakdown voltage than the gas tube, which provides a secondary means of protection in the event of a venting to atmosphere by the primary gas tube device.[C62.31-2006]

balanced voltage limitingThe simultaneous or near simultaneous breakdown of two gas-tube surgeprotective device components in response to a longitudinal (common mode) voltage.NOTE: The two gaps are usually combined in a single, three electrode gas-tube surge-protective device component.[C62.31-2006]

basic lightning impulse insulation level (BIL)The electrical strength of insulation expressed in terms of the crest value of a standard lightning impulse under standard atmospheric conditions. BIL may be expressed as either statistical or conventional. [C62.82.1-2010]

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basic lightning impulse insulation level (BIL)(A) The electrical strength of insulation in terms of the crest value of a standard lightning impulse under standard atmospheric conditions. BIL may be expressed as either statistical or conventional.(B) A specific insulation level expressed as the crest value of a standard lightning impulse. See also: conventional basic lightning impulse insulation level (BIL); statistical basic lightning impulse insulation level (BIL).[C62.11-2005]

basic lightning impulse insulation level (BIL)The electrical strength of insulation expressed in terms of the crest value of a standard lightning impulse under standard atmospheric conditions. BIL may be expressed as either statistical or conventional.[C62.22-2009]

basic switching impulse insulation level (BSL)The electrical strength of insulation expressed in terms of the crest value of a standard switching impulse. BSL may be expressed as either statistical or conventional. [C62.82.1-2010]

basic switching impulse insulation level (BSL)The electrical strength of insulation expressed in terms of the crest value of a standard switching impulse. BSL may be expressed as either statistical or conventional.[C62.22-2009]

basic switching impulse insulation level (BSL)(A) The electrical strength of insulation expressed in terms of the crest value of a standard switching impulse. BSL may be expressed as either statistical or conventional.(B) A specific insulation level expressed as the crest value of a standard switching impulse. See also: conventional basic switching impulse insulation level (BSL); statistical basic switching impulse insulation level (BSL).[C62.11-2005]

bidirectional thyristorA thyristor having substantially the same switching behavior in the first and third quadrants of the principal voltage-current characteristic.[62.37-1996]

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blockingA term describing the state of a semiconductor device or junction that imposes high resistance to the passage of current.[62.37-1996]

blocking voltageThe maximum voltage that can be applied to current-limiting pairs of terminals of a surge protector containing one or more current-protective devices without degradation of the surge protector.[C62.36-2000]

breakdownA phenomena occurring in a reverse biased semiconductor junction, the initiation of which is observed as a transition from a region of high dynamic resistance to a region of substantially lower dynamic resistance for increasing magnitude of reverse current.[62.37-1996]

breakdownThe abrupt transition of the gap resistance from a practically infinite value to a relatively low value. In the case of a gap, this is sometimes referred to as sparkover or ignition. See

also: sparkover.[C62.31-2006]

breakdown (clamping) regionThe portion of the volt-ampere characteristic occurring in a reverse-biased P-N junction that starts with the transition from a region of high resistance to a region of substantially lower small-signal resistance for an increasing magnitude of current.[C62.35-2010]

breakdown currentI(BR)

The current through the device in the breakdown region.[62.37-1996]

breakdown regionThe portion of the characteristic that starts with the transition from the high dynamic resistance off-state to a substantially lower dynamic resistance and extending to the switching point.[62.37-1996]

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breakdown voltageV(BR)The voltage across the device at a specified pulsed dc current in the avalanche region.[C62.35-2010]

breakdown voltageV(BR)

The voltage across the device in the breakdown region (prior to the switching point) at a specified breakdown current, I(BR).[62.37-1996]

breakdown voltage, acThe minimum rms value of a sinusoidal voltage at frequencies between 15 Hz and 62 Hz that results in gas-tube sparkover.[C62.31-2006]

breakdown voltage, dcThe minimum dc voltage with a ramp rate (100 V/s to 2000 V/s) that will cause breakdown or sparkover when applied across the terminals of a gas tube.[C62.31-2006]

breakover currentI(BO)

The instantaneous current flowing at the breakover voltage.[62.37-1996]

breakover pointAny point on the principal voltage-current characteristic for which the differential resistance is zero and where the principal voltage reaches a maximum value.NOTE: For a thyristor SPD, the breakover point occurs in the breakdown region. If more than one breakover point exists in the breakdown region, the one with the highest voltage value shall be characterized.[62.37-1996]

breakover voltageV(BO)

The maximum voltage across the device in or at the breakdown region measured under specified voltage rate of rise and current rate of rise.[62.37-1996]

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Ccapacitance

C

Capacitance between two terminals of the device measured at a specific frequency and biasNOTE—Also known as CJ.[C62.35-2010]

capacitance (Varistor)CCapacitance between the two terminals of the varistor measured at specified frequency and bias.[C62.33-1982]

cascade coordinationThe planned interaction between two or more surge-protective devices (SPDs) on the same power distribution system.[C62.72-2007]

cathodeThe electrode by which current leaves the thyristor, when the thyristor is in the on-state with the gate open-circuited.NOTE: This term does not apply to bi-directional thyristors.[62.37-1996]

certification testsTests run on a regular, periodic basis to verify that selected, key performance characteristics of a product or representative samples thereof have remained within performance specifications.[C62.11-2005]

characteristicAn inherent and measurable property of a device. Such a property may be electrical, mechanical, thermal, hydraulic, electromagnetic, or nuclear, and can be expressed as a value for stated or recognized conditions. A characteristic may also be a set of related values, usually shown in graphical form.[62.37-1996]

clamping (suppression) voltage

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The peak voltage across the varistor measured under conditions of a specified peak pulse current and specified waveform. NOTE: Peak voltage and peak current are not necessarily coincident in time. [C62.41.1-2002]

clamping factor (CF)Ratio of the measured clamping voltage (VC) at a specified peak impulse current (IPP) to breakdown voltage (V(BR)): CF = VC /V(BR).[C62.35-2010]

clamping voltageVC

Peak voltage across the device during the application of a peak impulse current (IPP) for a specified wave shape.NOTE —The clamping voltage VC is the peak voltage value measured neglecting any voltage overshoot caused by the inductance of the device packaging.[C62.35-2010]

clamping voltageVC

Peak voltage across the Varistor measured under conditions of a specified peak pulse current and specified waveform.NOTE: Peak voltage and peak current are not necessarily coincidental in time. [C62.33-1982]

clamping voltagePeak voltage across the SPD measured under conditions of a specified peak pulse current and specified waveform.NOTE: Peak voltage and peak current are not necessarily coincident in time.[62.37-1996]

class of groundingA specific range or degree of grounding; e.g., effectively and noneffectively.[C62.92.1-2000]

classification of arrestersArrester classification is determined by prescribed test requirements of this standard. These classifications are station, intermediate, distribution heavy duty, distribution normal duty,

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distribution light duty.[C62.11-2005]

classifying currentThe designated current used to perform the classification tests.[C62.11-2005]

coefficient of grounding (COG)The ratio, ELG/ELL (expressed as a percentage), of the highest root-mean-square (rms) line-to-ground power-frequency voltage ELG on a sound phase, at a selected location, during a fault to ground affecting one or more phases to the line-to-line power-frequency voltage ELL that would be obtained at the selected location with the fault removed.[C62.22-2009]

combination waveThe combination wave is delivered by a generator that applies a 1.2/50 µs voltage impulse across an open circuit and an 8/20 µs impulse current into a short circuit. The voltage and current and waveforms that are delivered to the surge protective device (SPD) are determined by the generator and the impedance of the SPD to which the surge is applied. The ratio of open-circuit voltage to peak short-circuit current is 2 ω.[C62.41.1-2002]

combination wave (1.2/50, 8/20)A wave delivered by a generator that applies a 1.2/50 voltage impulse across an open circuit and an 8/20 impulse current into a short circuit. The voltage, current, and waveforms that are delivered to the surge-protective device (SPD) are determined by the generator and the impedance of the SPD to which the surge is applied. The ratio of open-circuit voltage to peak short-circuit current is 2 Ω.[C62.34-1996]

common-modeThe instantaneous algebraic average of two signals applied to a balanced circuit, both signals referred to a common reference.[C62.72-2007]

component surge-protective device — voltage limiting typeA component surge-protective device that has a high impedance when no surge is present, but that can limit voltage by progressively and smoothly reducing its impedance when responding to a surge.

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Examples are component varistor and avalanche junction semiconductor surge-protective devices.NOTE - Also commonly referred to as a "voltage clamping" device.[ C62.42-2005]

component surge-protective device — voltage switching typeA component surge-protective device that has a high impedance when no surge is present, but that can have a sudden voltage collapse to a low impedance state when responding to a surge.Examples are component air gap and gas tube surge-protective devices.NOTE - Also commonly referred to as a "crowbar" device.[ C62.42-2005]

component surge-protective device (component SPD)A discrete surge-protective device involving a single specific technology and intended to be installed as a component within a surge protector or as a component housed within the equipment to be protected.NOTE — Examples are "component air gap surge-protective device", "component gas tube surge-protective device", "component varistor surge-protective device" and "component avalanche junction semiconductor surge-protective device". The term surge arrester is also used to describe a single component.[ C62.42-2005]

conformance testsTests made, when required, to demonstrate selected performance characteristics of a product or representative samples thereof.[C62.11-2005]

continuous operating currentIcThe peak current flowing through the SPD when energized at the maximum continuous operating voltage.[C62.34-1996]

conventional basic lightning impulse insulation level (BIL)Applicable specifically to nonselfrestoring insulations. The crest value of a standard lightning impulse for which the insulation does not exhibit disruptive discharge when subjected to a specific number of applications of this impulse under specified conditions. See also: statistical

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basic lightning impulse insulation level (BIL).[C62.11-2005]

conventional basic switching impulse insulation level (BSL)Applicable specifically to nonselfrestoring insulations. The crest value of a standard switching impulse for which the insulation does not exhibit disruptive discharge when subjected to a specific number of applications of this impulse under specified conditions. See also: statistical basic switching impulse insulation level (BSL).[C62.11-2005]

conventional BILThe crest value of a standard lightning impulse for which the insulation shall not exhibit disruptive discharge when subjected to a specific number of applications of this impulse under specified conditions, applicable specifically to nonself-restoring insulations.[C62.22-2009]

conventional BIL (basic lightning impulse insulation level)The crest value of a standard lightning impulse for which the insulation shall not exhibit disruptive discharge when subjected to a specific number of applications of this impulse under specified conditions, applicable specifically to non-self-restoring insulations.[C62.82.1-2010]

conventional BSLThe crest value of a standard switching impulse for which the insulation does not exhibit disruptive discharge when subjected to a specific number of impulses under specified conditions, applicable to nonself-restoring insulations.[C62.22-2009]

conventional BSL (basic switching impulse insulation level)The crest value of a standard switching impulse for which the insulation does not exhibit disruptive discharge when subjected to a specific number of impulses under specified conditions, applicable to non-self-restoring insulations. [C62.82.1-2010]

conventional withstand voltageThe voltage that an insulation system is capable of withstanding without failure or disruptive discharge under specified test conditions. [C62.82.1-2010]

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conventional withstand voltageThe voltage that an insulation is capable of withstanding with a 0% probability of failure.[C62.22-2009]

coordination of insulationThe selection of insulation strength consistent with expected overvoltages to obtain an acceptable risk of failure.[C62.22-2009]

counterpoiseA conductor or system of conductors arranged beneath the line; located on, above, or most frequently below the surface of the earth; and connected to the grounding system of the towers or poles supporting the line.[C62.23-1995]

coupling factorThe ratio of the induced voltage to the inducing voltage on parallel conductors.For example, at the tower, the shield or coupling wires and tower crossarms are at practically the same potential (because of lightning stroke travel time). The stress across the insulator string is one minus the coupling factor multiplied by the tower top potential.

Stress = (1.0 -Kfc ž VTT)

whereKfc is the coupling factorVTT is the tower top voltage[C62.23-1995]

coupling wireA conductor attached to the transmission line structure and below the phase wires, with proper clearance, and connected to the grounding system of the towers or the pole supporting the line.[C62.23-1995]

crackingThe rupture of the weathershed material to depths greater than 0.1 mm.[C62.11-2005]

crest (peak) value (of a wave, surge, or impulse)

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The maximum value that it attains.[62.37-1996]

crest (peak) value (of a wave, surge, or impulse)The maximum value that a wave, surge, or impulse attains.[C62.11-2005]

crest value (peak value)The maximum absolute value of a function when such a maximum exists. [C62.82.1-2010]

crest value(of an impulse)The maximum value that an impulse attains. Synonym: peak value.[C62.22-2009]

critical flashover voltage (CFO)The amplitude of voltage of a given waveshape that, under specified conditions, causes flashover through the surrounding medium on 50% of the voltage applications. [C62.82.1-2010]

critical flashover voltage (CFO)The amplitude of voltage of a given waveshape that, under specified conditions, causes flashover through the surrounding medium on 50% of the voltage applications.[C62.22-2009]

critical rate of rise of off-state voltagedv/dt

The maximum rate of rise of voltage (below VDRM) that will not cause switching from the off-state to the on-state.[62.37-1996]

critical rate of rise of on-state currentdi/dt

Rated value of the rate of rise of current which the device can withstand without damage.[62.37-1996]

current chopping (rotating electric machinery)A current wave in the machine circuit forced to zero by an interrupter at other than a fundamental frequency current zero in the interrupted phase and with a forcing duration in the

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order of microseconds or less.Example: vacuum circuit breaker, or a superimposed high-frequency switching surge current with a magnitude greater than the fundamental frequency current.[C62.21-2003]

current turnoff timeThe time required for the gas tube to restore itself to a non-conducting state following a period of conduction. This definition applies only to a condition where the gas tube is exposed to a continuous specified dc potential under a specified circuit condition.[C62.31-2006]

current zero (rotating electric machinery)That instant when an oscillatory current wave passes through zero magnitude.[C62.21-2003]

Ddamage

A) Degradation or loss of function which is not recoverable due to damage of equipment (components) or software, or loss of data.B) Temporary degradation or loss of function or performance which requires operator intervention or system reset. [C62.41.1-2002]

dc holdoverIn applications where a dc voltage exists on a line, a holdover condition is one in which a surge-protective device continues to conduct after it is subjected to an impulse large enough to cause breakdown. Factors that affect the time required to recover from the conducting state include the dc voltage and the dc current.[C62.31-2006]

dc holdover voltageThe maximum dc voltage across the terminals of a gas tube under which it may be expected to clear and return to the high impedance state after the passage of a surge, under specified circuit conditions.[C62.31-2006]

DC standby current (Varistor)

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IDVaristor current measured at rated voltage, Vm(dc)

[C62.33-1982]

deadfront type arresterAn arrester assembled in a shielded housing providing system insulation and conductive ground shield, intended to be installed in an enclosure for the protection of underground and padmounted distribution equipment and circuits.[C62.22-2009]

deflectorA means for directing the flow of the gas discharge from the vent of the arrester.[C62.11-2005]

degradationIrreversible change in characteristics of any component beyond the specification limit.[C62.62-2010]

design testsTests made on each design to establish the performance characteristics and to demonstrate compliance with the appropriate standards of the industry. Once made, they need not be repeated unless the design is changed so as to modify performance.[C62.34-1996]

design testsTests made on each design to establish the performance characteristics and to demonstrate compliance with the appropriate standards of the industry. Once made, they need not be repeated unless the design is changed so as to modify performance.[C62.11-2005]

device failureAn irreversible change in characteristic, resulting in an inability to perform as intended. [C62.41.1-2002]

diodeA semiconductor device having two terminals and exhibiting a nonlinear voltage-current characteristic; in more-restricted usage, a semiconductor device that has the asymmetrical voltage-current characteristic exemplified by a single p-n junction.[62.37-1996]

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discharge counterA means for recording the number of arrester discharge operations.[C62.11-2005]

discharge currentThe current that flows through a gas tube when sparkover occurs.[C62.31-2006]

discharge indicatorA means for indicating that the arrester has discharged.[C62.11-2005]

discharge voltageThe voltage that appears across the terminals of a gas tube during the passage of discharge current.[C62.31-2006]

discharge voltage-current characteristicThe variation of the crest values of discharge voltage with respect to discharge current.NOTE: This characteristic is normally shown as a graph based on three or more current-surge measurements of the same wave shape but of different crest values.[C62.11-2005]

discharge withstand currentThe specified magnitude and wave shape of a discharge current that can be applied to an arrester a specified number of times without causing damage to it.[C62.11-2005]

discharge-voltage-current characteristicThe variation of the crest values of discharge voltage with respect to discharge current.[C62.31-2006]

disruptive dischargeThe sudden and large increase in current through an insulating medium, due to the complete failure of the medium under the electrostatic stress.[C62.11-2005]

disruptive discharge

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The sudden and large increase in current through an insulating medium due to the complete failure of the medium under electrical stress.[C62.22-2009]

distribution arrester(A) heavy duty class: An arrester most often used to protect overhead distribution systems exposed to severe lightning currents.(B) light duty class: An arrester generally installed on and used to protect underground distribution systems where the major portion of the lightning stroke current is discharged by an arrester located at the overhead line/cable junction.(C) normal duty class: An arrester generally used to protect overhead distribution systems exposed to normal lightning currents.[C62.22-2009]

duty cycle testA test to determine if a device can repeatedly function, extinguish follow current, and avoid thermal runaway.[C62.34-1996]

duty-cycle voltage ratingThe designated maximum permissible voltage between its terminals at which an arrester is designed to perform its duty cycle.[C62.11-2005]

dynamic impedance (Varistor)Zx

A measure of small signal impedance at a given operating point as defined by:Zx = dVx/dIx[C62.33-1982]

Eeffectively grounded system

A system in which the neutral points are connected directly to the ground through a connection in which no impedance has been inserted intentionally. [C62.82.1-2010]

electrical environment

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The totality of conducted electrical phenomena existing at a given location.NOTE: These phenomena become disturbances only if they degrade the performance of equipment. [C62.41.1-2002]

electrical unitPortion of an arrester in which each end of the unit is terminated with an electrode which is exposed to the external environment.[C62.11-2005]

energy depositionThe time integral of the power dissipated in a clamping-type surge protective device (SPD) during a current surge of a specified waveform. [C62.41.1-2002]

external insulationThe air insulation and the exposed surfaces of solid insulation of equipment, which are both subject to dielectric stresses and to the effects of atmospheric and other external conditions such as contamination, humidity, vermin, etc. [C62.82.1-2010]

Ffail-safe

Use of this term is not recommended. See device failure. [C62.41.1-2002]

failureThe termination of the ability of an item to perform a required function.NOTE 1 — "Failure" is an event, as distinct from "fault", which is a state.NOTE 2 — A failure usually results in a fault state.[C62.31-2006]

failure modeSee device failure. [C62.41.1-2002]

failure mode

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A manner in which failure occurs.NOTE: A failure mode may be defined by the function lost or the state transition that occurred.[C62.31-2006]

faultA state causing inability to perform a required function.NOTE 1: Inability during preventive maintenance or other planned actions, or due to lack of external resources does not constitute a fault state.NOTE 2: A fault is often the result of a failure of the item itself, but may exist without prior failure.[C62.31-2006]

fault currentA current that flows from one conductor to ground or to another conductor due to an abnormal connection (including an arc) between the two. A fault current flowing to ground may be called a ground fault current.[C62.72-2007]

fault currentThe current from the connected power system that flows in a short circuit. [C62.41.1-2002]

fault currentThe current from the connected power system that flows in a short circuit.[C62.11-2005]

ferroresonanceCan also occur between the capacitance to ground of an ungrounded circuit and voltage transformers with primary windings that are grounded. This phenomenon is also possible in gas-insulated systems.[C62.22-2009]

ferroresonanceA phenomenon usually characterized by overvoltages and very irregular wave shapes and associated with the excitation of one or more saturable inductors through capacitance in series with the inductor. [C62.72-2007]

flashover

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A disruptive discharge around or over the surface of a solid or liquid insulator.[C62.22-2009]

flashoverA disruptive discharge around or over the surface of a solid or liquid insulator.[C62.11-2005]

follow currentThe current from the connected power source that flows through a gas tube during and following the passage of discharge current.[C62.31-2006]

follow current (power)A) The current from the connected power source that flows through an arrester during and following the passage of discharge current. B) Current supplied by the electrical power system and flowing through the SPD after a discharge current impulse and significantly different from the continuous operating current (IC) [C62.41.1-2002]

forced current zero (rotating electric machinery)A current wave in the machine circuit forced to zero by an interrupter at other than a fundamental frequency current zero in the interrupted phase and with a forcing duration of several milliseconds but less than a half cycle of fundamental frequency.Example: current-limiting fuse.[C62.21-2003]

forward conducting regionThe portion of the volt-ampere characteristic occurring in a forward-biased P-N junction where there is a low small-signal resistance to the passage of current. [C62.35-2010]

forward currentIFThe current through the device in the forward conducting state.[62.37-1996]

forward direction1) The direction of current in a p-n junction that results when the p-type semiconductor region is at a positive potential relative to the n-type region.

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2) The direction of current in a semiconductor device that results when the p-type semiconductor region connected to one terminal is at a positive potential relative to the n-type region connected to the other terminal.NOTE: This definition does not apply if one or more junctions are connected in series with at least one other junction whose p and n regions are reversed.[62.37-1996]

forward voltageVF

The voltage across the device in the forward conducting state at a specified current IF.[C62.35-2010]

forward voltageVF

The voltage across the device in the forward conducting state at a specified current IF.[62.37-1996]

forward-conducting diode thyristor surge protection device (SPD)A two-terminal internally triggered thyristor SPD that switches only for negative terminal-2 (cathode) voltage and conducts large currents at positive terminal-2 voltages comparable in magnitude to the on-state voltage.NOTE 1 - In conventional thyristor applications where the cathode is the common terminal, this device would be called a reverse-conducting diode thyristor.NOTE 2 - When terminal 2 (cathode) is positive, the device characteristics are similar to those of a forward biased diode.NOTE 3 - When terminal 2 (cathode) is negative, the device characteristics are similar to those of a breakover-triggered SCR.[62.37-1996]

forward-conducting triode thyristor surge protection device (SPD)A three-terminal thyristor SPD that switches only for negative main terminal-2 (cathode) voltage and conducts large currents at positive main terminal-2 voltages comparable in magnitude to the on-state voltage.NOTE 1 - In conventional thyristor applications where the cathode is the common terminal, this device would be called a reverse-conducting triode thyristor.NOTE 2 - Application of an appropriate fixed gate voltage allows switching to take place at voltages well below the intrinsic breakover value.NOTE 3 - When main terminal 2 (cathode) is positive, the device characteristics are similar to

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those of a forward biased diode.[62.37-1996]

forward/reverse conducting quadrantA quadrant of the principal voltage-current characteristic in which the device exhibits a forward direction conduction state. This will be quadrant 1 for a forward conducting thyristor SPD and quadrant 3 for a reverse conducting thyristor SPD.[62.37-1996]

front-of-wave impulse sparkover voltageThe impulse sparkover voltage with a wave front that rises at a uniform rate and causes sparkover on the wave front.[C62.11-2005]

front-of-wave lightning impulse voltage shapeA voltage impulse, with a specified rate-of-rise, that is terminated intentionally by sparkover of a gap that occurs on the rising front of the voltage wave with a specified time to sparkover, and a specified minimum crest voltage. [C62.82.1-2010]

Ggapless

Not possessing gaps, series, or parallel as in gapless arrester.[C62.11-2005]

gas-tube surge arrester (gas-tube surge-protective device component)A gap, or gaps, in an enclosed discharge medium, other than air at atmospheric pressure, designed to protect apparatus or personnel, or both, from high transient voltages.[C62.31-2006]

gateAn electrode connected to one of the semiconductor regions to introduce a control current.[62.37-1996]

gate reverse current, adjacent terminal openIGAO; IGKO

The current through the gate terminal when a specified gate bias voltage, VG, is applied and the cathode terminal for a p-gate device or anode terminal for an n-gate device is open circuited.[62.37-1996]

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gate reverse current, forward conducting stateIGAF;IGKF

The current through the gate terminal when a specified gate bias voltage, VG, is applied and a specified forward conduction current, IF, is flowing.[62.37-1996]

gate reverse current, main terminals short-circuitedIGAS;IGKS

The current through the gate terminal when a specified gate bias voltage, VG, is applied and the cathode terminal for a p-gate device or anode terminal for an n-gate device is short circuited to the third terminal.[62.37-1996]

gate reverse current, on-stateIGAT;IGKT

The current through the gate terminal when a specified gate bias voltage, VG, is applied and a specified on-state current, IT, is flowing.[62.37-1996]

gate switching chargeQGS

The charge through the gate terminal, under impulse conditions, during the transition from the off-state to the switching point, when a specified gate bias voltage, VG, is applied.[62.37-1996]

gate-to-adjacent terminal breakover voltageVGK(BO); VGA(BO)

The gate to cathode voltage for a p-type device or gate to anode voltage for an n-gate device at the breakover point. This is equivalent to the voltage difference between the breakover voltage, V(BO), and the specified gate voltage, VG.

[62.37-1996]

gate-to-adjacent terminal peak off-state voltageVGDM

The maximum gate to cathode voltage for a p-gate device or gate to anode voltage for an n-gate device that may be applied such that a specified off-state current, ID, at a rated off-state voltage, VD, is not exceeded.[62.37-1996]

24


glow currentThe current that flows after breakdown when circuit impedance limits the current to a value less than the glow-to-arc transition current. Syn:glow mode current.[C62.31-2006]

glow voltageThe voltage drop across the gas tube during glow-current flow. It is sometimes called the glow mode voltage.[C62.31-2006]

glow-to-arc transition currentThe current required for the gas tube to pass from the glow mode into the arc mode.[C62.31-2006]

grading or control ringA metal part, usually circular or oval in shape, mounted to modify electrostatically the voltage gradient or distribution.[C62.11-2005]

ground insulation (rotating electric machinery)Insulation used to insure the electric isolation of the windings from the core and mechanical parts of a machine. It separates the turn insulation from the surrounding slot steel. Ground insulation is sometimes referred to as coil insulation, or groundwall insulation.[C62.21-2003]

ground potential rise (GPR)The voltage that a station grounding grid may attain relative to a distant grounding point assumed to be at the potential of remote earth.[C62.23-1995]

ground terminalThe conducting part provided for connecting the arrester to ground.[C62.11-2005]

ground-fault factorThe ratio of the highest power frequency voltage on an unfaulted phase during a line-to-ground fault to the phase-to-ground power-frequency voltage without the fault. NOTE 1 — The ground-fault factor generally will be less than 1.3, if the zero-sequence reactance

25


is less than three times the positive-sequence reactance, and the zero-sequence resistance does not exceed the positive-sequence reactance.NOTE 2 — IEEE Std C62.1-1989 defines a “coefficient of grounding.” This coefficient can be obtained by dividing the ground-fault factor by root 3. [C62.82.1-2010]

Hholding current

IHThe minimum current required to maintain the device in the on-state.[62.37-1996]

Iimmunity (to a disturbance)

The ability of a device, equipment, or system to perform without degradation in the presence of an electromagnetic disturbance. [C62.41.1-2002]

impedance grounded neutral systemA system whose neutral point(s) are grounded through an impedance (to limit ground-fault currents). [C62.82.1-2010]

impulseA surge of unidirectional polarity.[C62.22-2009]

impulseA surge of unidirectional polarity.[C62.11-2005]

impulseA surge of unidirectional polarity.[62.37-1996]

impulse protective levelFor a defined wave shape, the higher of the maximum sparkover value or the corresponding discharge-voltage value.[C62.11-2005]

26


impulse protective volt-time characteristicThe discharge-voltage time response of the device to impulses of a designated wave shape and polarity, but of varying magnitudes.[C62.11-2005]

impulse reset timet(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.[62.37-1996]

impulse sparkover volt-time characteristicThe 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 crest voltage values plotted against time to sparkover.[C62.11-2005]

impulse sparkover voltageThe highest value of voltage attained by an impulse of a designated waveshape and polarity applied across the terminals of a gas tube prior to the flow of discharge current. Syn:surge or impulse breakdown voltage.[C62.31-2006]

impulse sparkover voltage-time curveA curve that relates the impulse sparkover voltage to the time to sparkover.[C62.31-2006]

impulse waveA 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.[62.37-1996]

impulse withstand voltage

27


The crest value of an impulse that, under specified conditions, can be applied without causing a disruptive discharge.[C62.11-2005]

In-Line SPDA two-port device connected in series between the power supply and a load where the load current passes through the conductive terminals of the SPD such that the removal of the SPD opens the circuit.[C62.62-2010]

indoor arresterAn arrester that, because of its construction, must be protected from the weather.[C62.11-2005]

insertion lossLoss resulting from the insertion of a device into a transmission system, expressed as the ratio of the power delivered to that part of the system following the device, before insertion of the device, to the power delivered to that same part after insertion of the device.NOTE —The insertion loss is generally expressed in decibels. [C62.35-2010]

insulation configurationThe complete geometric configuration of the insulation, including all elements (insulating and conducting) that influence its dielectric behavior.Examples of insulation configurations are phase-to-ground, phase-to-phase, and longitudinal. [C62.82.1-2010]

insulation coordinationThe selection of insulation strength consistent with expected overvoltages to obtain an acceptable risk of failure. [C62.82.1-2010]

insulation levelA 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.[C62.22-2009]

insulation resistance

28


The equivalent insulation resistance of the device, computed by VD / ID[62.37-1996]

internal insulationInternal insulation comprises the internal solid, liquid, or gaseous elements of the insulation of equipment, which are protected from the effects of atmospheric and other external conditions such as contamination, humidity, and vermin. [C62.82.1-2010]

ionization currentThe electric current resulting from the movement of electric charges in an ionized medium, under the influence of an applied electric field.[C62.11-2005]

ionization voltageA 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.[C62.11-2005]

Llifetime 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.[62.37-1996]

lifetime rated pulse currents (Varistor).derated values of Itm for impulse durations exceeding that of an 8/20 µs waveshape, and for multiple pulses which may be applied over device's rated lifetime.[C62.33-1982]

lightningAn electric discharge that occurs in the atmosphere between clouds or between clouds and ground. [C62.72-2007]

lightning

29


An electric discharge that occurs in the atmosphere between clouds or between clouds and ground.[C62.11-2005]

lightning impulse protective level of a surge-protective deviceThe maximum lightning impulse voltage expected at the terminals of a surge-protective device under specified conditions of operation.NOTE — The lightning impulse protective levels are given by following: 1) Front-of-wave impulse sparkover or discharge voltage, and 2) the higher of either a 1.2/50 impulse sparkover voltage or the discharge voltage for a specified current magnitude and waveshape. [C62.82.1-2010]

lightning overvoltageA type of transient overvoltage in which a fast front voltage is produced by lightning or fault. Such overvoltage is usually unidirectional and of very short duration. [C62.82.1-2010]

lightning overvoltageThe crest voltage appearing across an arrester or insulation caused by a lightning surge.[C62.22-2009]

lightning surgeA transient electric disturbance in an electric circuit caused by lightning.[C62.22-2009]

lightning surgeA transient electric disturbance in an electric circuit caused by lightning.[C62.11-2005]

lightning surgeA transient electric disturbance in an electric circuit caused by lightning. [C62.72-2007]

line terminalThe conducting part of the arrester provided for connecting the arrester to the circuit conductor.[C62.11-2005]

liquid-immersed type arrester

30


An arrester designed for use immersed in an insulating liquid.[C62.22-2009]

local surge (rotating electric machinery)A surge that originates on the same voltage system as the machine with no transformation between.[C62.21-2003]

longitudinal (common) mode voltageThe voltage common to all conductors of a group as measured between that group at a given location and an arbitrary reference (usually earth).[C62.31-2006]

longitudinal insulation configurationAn insulation configuration between terminals belonging to the same phase, but which are temporarily separated into two independently energized parts (e.g., open switching device). [C62.82.1-2010]

longitudinal overvoltageAn overvoltage that appears between the open contact of a switch. [C62.82.1-2010]

Mmain overcurrent protective device

The first overcurrent device between the secondary terminals of the distribution or power class transformer and the load terminals of the service entrance equipment. Also identified as the service entrance main. [C62.72-2007]

main terminal 1The main terminal that is named 1 by the device manufacturer.[62.37-1996]

main terminal 2The main terminal that is named 2 by the device manufacturer.[62.37-1996]

main terminals

31


The two terminals through which the principal current flows.NOTE: The main terminals may be named by application usage. In telecommunications, terminals may be named after the line connections of R(ing), T(ip), and G(round) or A, B, and C(ommon).[62.37-1996]

mainsThe ac power source available at the point of use in a facility. It consists of the set of electrical conductors (referred to by terms including service entrance, feeder, or branch circuit) for delivering power to connected loads at the utilization voltage level. [C62.41.1-2002]

mainsThe ac power source available at the point of use in a facility. It consists of the set of electrical conductors (referred to by terms including service entrance, feeder, or branch circuit) for delivering power to connected loads at the utilization voltage level. [C62.72-2007]

maximum continuous operating voltage (MCOV)The maximum designated root-mean-square (rms) value of power-frequency voltage that may be applied continuously between the terminals of the arrester. [C62.41.1-2002]

maximum continuous operating voltage (MCOV)The maximum designated root-mean-square (rms) value of power-frequency voltage that may be applied continuously between the terminals of the arrester.[C62.11-2005]

maximum continuous operating voltage (MCOV)The maximum designed root-mean-square (rms) value of power frequency voltage that may be applied continuously between the terminals of the arrester. [C62.72-2007]

maximum continuous operating voltage rating (MCOV)The maximum designated root-mean-square (rms) value of power frequency voltage that may be applied continuously between the terminals of the arrester.[C62.22-2009]

maximum design cantilever load-static (MDCL-static)

32


The maximum cantilever load the surge arrester is designed to continuously carry.[C62.11-2005]

maximum discharge currentIpThe maximum surge current that the SPD withstands without damage. The maximum discharge current is a peak impulse current, with a wave shape of 8/20.[C62.34-1996]

maximum junction temperatureTJM

The maximum value of permissible junction temperature, due to self heating, which a device can withstand without degradation.[C62.35-2010]

maximum junction temperatureTJM

The maximum value of permissible junction temperature, due to self heating, which a thyristor SPD can withstand without degradation.[62.37-1996]

maximum rating (absolute maximum rating)A rating that establishes either a limiting capability or a limiting condition beyond which damage to the device may occur.NOTE: A limiting condition may be either a maximum or a minimum.[62.37-1996]

maximum system voltageVm

The highest root-mean-square (rms) phase-to-phase voltage that occurs on the system under normal operating conditions, and the highest rms phase-to-phase voltage for which equipment and other system components are designed for satisfactory continuous operation without deterioration of any kind. [C62.82.1-2010]

maximum system voltageThe highest voltage at which a system is operated.NOTE: This is generally considered to be the maximum system voltage as prescribed in ANSI Std

33


C84.1-1995 (Reaff 2001).[C62.11-2005]

maximum-continuous operating voltage (MCOV)Uc

The maximum rms value of power-frequency voltage that may be applied continuously between the terminals of the arrester without degradation or deleterious effects.[C62.34-1996]

means of groundingThe physical devices by which various degrees of grounding are achieved; e.g., inductance grounding, resistance grounding, or resonant grounding. [C62.92.1-2000]

measured limiting voltageThe maximum magnitude of voltage that is measured across the terminals of the surge protective device (SPD) during the application of a series of impulses of specified wave shape and amplitude. [C62.41.1-2002]

measured limiting voltageThe maximum magnitude of voltage that is measured across the terminals of the SPD during the application of a series of impulses of specified wave shape and amplitude.[C62.34-1996]

mechanical unitPortion of an arrester in which the valve elements within the unit are mechanically restrained from moving in an axial direction.[C62.11-2005]

metal-oxide surge arrester (MOSA)A surge arrester utilizing valve elements fabricated from nonlinear resistance metal-oxide materials.[C62.11-2005]

metal-oxide surge arrester (MOSA)A surge arrester utilizing valve elements fabricated from nonlinear resistance metal-oxide materials.[C62.22-2009]

34


Mode of ProtectionAn SPD's protective component(s) may be connected wherever protection is required against transient overvoltages. These may include Line to Neutral (L-N), Line to Ground (L-G), Line to Line (L-L) and Neutral to Ground (N-G).[C62.62-2010]

multiport surge protectorA surge protector that provides surge protective function to two or more circuits, such as, but not limited to, paired conductors, coaxial cables, or mains, whereby all conductors connected to the protected circuits are routed through a common enclosure having a shared common terminal.[C62.36-2000]

Nn-gate thyristor

A three-terminal thyristor in which the gate terminal is connected to the n-region adjacent to the region to which the anode is connected and that is normally switched to the on state by applying a negative signal between the gate and anode terminals.[62.37-1996]

negative differential-resistance (region)The region of the principal voltage-current characteristic in the switching quadrant where the differential resistance is negative and the thyristor is switching between the breakdown and on-state regions.[62.37-1996]

negative-breakdown resistance thyristor surge protection device (SPD)A thyristor SPD, whose static breakdown characteristic has a net negative-resistance slope prior to switching.[62.37-1996]

nominal discharge currentInThe discharge current that can be applied to an SPD a specified number of times without causing damage to it. The nominal discharge current is a peak surge current, with a wave shape of 8/20.[C62.34-1996]

35


nominal rate of rise (of an impulse wave front)The slope of the line that determines the virtual zero. It is usually expressed in volts or amperes per microsecond.[C62.11-2005]

nominal rate of rise(of an impulse)For a wave front, the slope of the line that determines the virtual zero. It is usually expressed in volts or amperes per microsecond.

nominal system voltageA nominal value assigned to designate a system of a given voltage class. [C62.41.1-2002]

nominal system voltageThe rms phase-to-phase voltage by which the system is designated and to which certain operating characteristics of the system are related.NOTE — The nominal system voltage is near the voltage level at which the system normally operates. To allow for operating contingencies, systems generally operate at voltage levels about 5%-10% below the maximum system voltage for which systems components are designed.[C62.82.1-2010]

nominal system voltageA nominal value assigned to designate a system of a given voltage class.NOTE: See ANSI C84.1-1995.[C62.34-1996]

nominal system voltageA nominal value assigned to designate a system of a given voltage class.NOTE: See ANSI Std C84.1-1995 (Reaff 2001).[C62.11-2005]

nominal system voltageA nominal value assigned to designate a system of a given voltage class.[C62.22-2009]

nominal Varistor voltageVN(dc)

Voltage across the varistor measured at a specified pulsed dc current, IN(dc), of specific

36


duration. IN(dc) is specified by the varistor manufacturer. [C62.33-1982]

non-repetitive current ratingA maximum rating that may be applied to the device for a minimum of 100 times over the life of the device without failure. During the rated condition, the device is permitted to exceed its maximum rated junction temperature for short periods of time. The device is not required to block voltage or retain any gate control during or immediately following this rated condition until the device returned to the original thermal equilibrium conditions. This rated condition may be repeated after the device has returned to the original thermal equilibrium conditions.[62.37-1996]

non-repetitive peak forward currentIFSM

Rated maximum (peak) value of ac power frequency forward surge current of specified wave shape and frequency which may be applied for a specified time or number of ac cycles.[62.37-1996]

non-repetitive peak on-state currentITSM

Rated maximum (peak) value of ac power frequency on-state surge current of specified wave shape and frequency which may be applied for a specified time or number of ac cycles.[62.37-1996]

non-repetitive peak pulse currentIPPS

Rated maximum value of peak impulse pulse current of specified amplitude and wave shape that may be applied.[62.37-1996]

non-self-restoring insulationAn insulation that loses its insulating properties or does not recover them completely, after a disruptive discharge caused by the application of a test voltage; insulation of this kind is generally, but not necessarily, internal insulation. [C62.82.1-2010]

nonlinear exponentA measure of varistor nonlinearity between two given operating currents, I1 and I2, as described by I = kVα where k is a device constant, I1 < I < I2, and α

37


α12, = log (I2 /I1) / (log(V2 /V1)[C62.33-1982]

nonlinear loadAn electrical load that draws current discontinuously or whose impedance varies during the cycle of the input ac voltage waveform.[C62.48-2005]

nonlinear load currentLoad current that is discontinuous or is not proportional to the ac voltage. [C62.48-2005]

nonself-restoring insulationAn insulation that loses its insulating properties or does not recover them completely after a disruptive discharge caused by the application of a test voltage; insulation of this kind is generally, but not necessarily, internal insulation.[C62.22-2009]

normal interruption (rotating electric machinery)A machine circuit interruption by an interrupting device at a current zero of the fundamental frequency current.[C62.21-2003]

normal lightning currentLightning currents of 65 kA or less. See also: severe lightning current.[C62.11-2005]

normal-modeThe voltage that appears differentially between two signal wires and that acts on the circuit in the same manner as the desired signal. [C62.72-2007]

Ooff-state capacitance

CO

The capacitance in the off-state measured at specified frequency, f, amplitude, Vd, and dc bias, VD.[62.37-1996]

38


off-state currentIDThe dc value of current that results from the application of the off-state voltage.[62.37-1996]

off-state of a thyristor surge protection device (SPD)The state of a thyristor SPD, in a quadrant in which switching can occur, that corresponds to the high dynamic-resistance portion of the characteristic between the origin and the beginning of the breakdown region.[62.37-1996]

off-state voltageVD

The dc voltage when the device is in the off-state.[62.37-1996]

on-state (region)The condition of the thyristor corresponding to the low-resistance low-voltage portion of the principal voltage-current characteristic in the switching quadrant(s).[62.37-1996]

on-state currentITThe current through the device in the on-state condition.[62.37-1996]

on-state voltageVT

The voltage across the device in the on-state condition at a specified current.[62.37-1996]

one-port SPDA SPD with protective components connected in shunt with the circuit to be protected. A one-port SPD may have separate input and output terminals without a specified series impedance between these terminals.[C62.34-1996]

open-circuit voltage (OCV)

39


The voltage available from the complete test set-up as configured (surge generator, coupling circuit, back filter, connecting leads), prior to connecting the equipment under test (EUT), at the terminals where the surge protective device (SPD) under test will be connected. [C62.41.1-2002]

operating duty cycleOne or more unit operations, as specified.[C62.11-2005]

oscillatory surgeA surge that includes both positive and negative polarity values. [C62.41.1-2002]

oscillatory surgeA surge that includes both positive and negative polarity values.[C62.11-2005]

outdoor arresterAn arrester that is designed for outdoor use.[C62.11-2005]

overhead groundwire (lightning protection)Grounded wire or wires placed above phase conductors for the purpose of intercepting direct strokes in order to protect the phase conductors from the direct strokes. They may be grounded directly or indirectly through short gaps.[C62.23-1995]

overshoot duration (Varistor)The time between the point at which the wave exceeds the clamping voltage level (VC) and the point at which the voltage overshoot has decayed to 50% of its peak. For the purpose of this definition, clamping voltage is defined with an 8/20 µs current waveform of the same peak current amplitude as the waveform used for this over-shoot duration.[C62.33-1982]

overvoltageAbnormal voltage between two points of a system that is greater than the highest value appearing between the same two points under normal service conditions. Overvoltages may be low-frequency, temporary, and transient (surge).[C62.22-2009]

40


overvoltageVoltage, between one phase and ground or between two phases, having a crest value exceeding the corresponding crest of the maximum system voltage. Overvoltage may be classified by shape and duration as either temporary or transient.NOTE 1 — Unless otherwise indicated, such as for surge arresters, overvoltages are expressed in per unit with reference to maximum rms system voltage, Vm*(2/3)0.5.NOTE 2 — A general distinction may be made between highly damped overvoltages of relatively short duration (transient overvoltages) and undamped or only slightly damped overvoltages of relatively long duration (temporary overvoltages). The transition between these two groups cannot be clearly defined.[C62.82.1-2010]

Pp-gate thyristor

A three-terminal thyristor in which the gate terminal is connected to the p-region adjacent to the region to which the cathode is connected and that is normally switched to the on state by applying a positive signal between the gate and cathode terminals.[62.37-1996]

parameterA device descriptor that is measurable or quantifiable, such as a characteristic or rating.[62.37-1996]

partial discharge (PD)A localized electric discharge resulting from ionization in an insulation system when the voltage stress exceeds the critical value. This discharge partially bridges the insulation between electrodes.[C62.11-2005]

peak forward recovery voltageVFRM

The maximum value of forward conduction voltage across the device upon the application of a specified voltage rate of rise and current rate of rise following a zero or specified reverse-voltage condition.[62.37-1996]

peak gate switching current

41


IGSM

The maximum value of current through the gate terminal during the transition from the off-state to the switching point, when a specified gate bias voltage, VG, is applied.[62.37-1996]

peak impulse currentIPP

The peak current for a series of essentially identical impulse waveforms.[C62.35-2010]

peak nominal Varistor voltageVN(ac)

Voltage across the varistor measured at a specified peak ac current, IN(ac), of specific duration. IN(ac) is specified by the varistor manufacturer. [C62.33-1982]

peak off-state gate currentIGDM

The maximum gate current that results from the application of the peak off-state gate voltage, VGDM.[62.37-1996]

peak pulse impulse currentIPPM

Rated maximum value of peak impulse pulse current (IPP) applied for 10 pulses with 10/1000 µs waveform and maximum duty factor of 0.01% without causing failure.[62.37-1996]

peak valueSee: crest value.[C62.22-2009]

per unit (pu)The ratio of the actual value of a quantity to the base value of the same quantity.[C62.21-2003]

per unit surge voltage (rotating electric machinery)The ratio of a surge voltage crest magnitude to the crest value of the machine rated voltage. For a three-phase machine, the divisor (1pu) is the crest value of the rated phase-to-neutral voltage

42


and equals phase-to-phase rated voltage V times the square-root of two divided by the square-root of three, V(2/3)0.5.[C62.21-2003]

performance criterionThe criterion upon which the insulation strength or withstand voltages and clearances are selected. The performance criterion is based on an acceptable probability of insulation failure and is determined by the consequence of failure, required level of reliability, expected life of equipment, economics, and operational requirements. The criterion is usually expressed in terms of an acceptable failure rate (number of failures per year, years between failures, risk of failure, etc.) of the insulation configuration. [C62.82.1-2010]

phase-to-ground insulation configurationAn insulation configuration between a terminal and the neutral or ground. [C62.82.1-2010]

phase-to-phase insulation configurationAn insulation configuration between two-phase terminals. [C62.82.1-2010]

positive-breakdown-resistance thyristor surge protection device (SPD)A thyristor SPD, whose static breakdown characteristic has a net positive-resistance slope prior to switching.[62.37-1996]

power crossAn event in an electrical distribution system where a higher voltage conductor, such as from a transmission line, falls on a lower voltage conductor, such as a distribution or secondary line. [C62.48-2005]

power-frequency sparkover voltageThe root-mean-square (rms) value of the lowest powerfrequency sinusoidal voltage that will cause sparkover when applied across the terminals of an arrester.[C62.11-2005]

power-frequency withstand voltage

43


A specified root-mean-square (rms) test voltage at a power frequency that will not cause a disruptive discharge.[C62.11-2005]

preferred valuesThe parameters listed for various tests are preferred in the sense that their use promotes uniformity. However, specific applications may require values other than the listed preferred values.[C62.34-1996]

principal currentA generic term for the current through the device excluding any gate current.NOTE: It is the current through both main terminals.[62.37-1996]

principal voltageThe voltage between the main terminals.NOTE 1 - In the case of reverse blocking and reverse conducting thyristors, the principal voltage is called positive when the anode potential is higher than the cathode potential, and called negative when the anode potential is lower than the cathode potential.NOTE 2 - For bidirectional thyristors, the principal voltage is called positive when the potential of main terminal 2 is higher than the potential of main terminal 1.a

NOTE 3 - For forward-conducting thyristors the principal voltage is called positive when the cathode potential is higher than the anode potential, and called negative when the cathode potential is lower than the anode potential.[62.37-1996]

principal voltage-current characteristicThe function, usually represented graphically, relating the principal voltage to the principal current.[62.37-1996]

production testsSee: routine tests.[C62.11-2005]

prorated sectionA complete, suitably housed part of an arrester, comprising all necessary components, including gaseous medium, in such a proportion as to accurately represent, for a particular test, the

44


characteristics of a complete arrester.[C62.11-2005]

prospective (available) short-circuit current (at a given point in a circuit)The maximum current that the power system can deliver through a given circuit point to any negligible impedance, short circuit applied at the given point or at any other point that will cause the highest current to flow through the given pointNOTE 1 This value can be in terms of either symmetrical or asymmetrical, peak or root-mean-square (rms) current, as specified.NOTE 2 In some resonant circuits, the maximum available short-circuit current may occur when the short circuit is placed at some other point than the given one where the available current is measured.[C62.11-2005]

prospective overvoltageThe theoretical voltage that a lightning event might couple or induce into a power system if it were not truncated by flashover of insulation or action of an surge protective device (SPD). [C62.41.1-2002]

protective margin (PM)The value of the protective ratio (PR), minus one, expressed in percent. PM = (PR-1) x 100. [C62.82.1-2010]

protective ratio (PR)The ratio of the insulation strength of the protected equipment to the overvoltages appearing across the insulation. [C62.82.1-2010]

protectorSee surge protector.[C62.36-2000]

pulse lifeThe number of surges of specified voltage, current amplitudes, and wave shapes that may be applied to a device without causing degradation beyond specified limits. The pulse life applies to a device connected to an ac line of specified characteristics and for pulses sufficiently spaced in time to preclude the effects of cumulative heating. [C62.41.1-2002]

45


puncture(A) A disruptive discharge through a solid dielectric.(B) A disruptive discharge through solid insulation.(C) Term used to denote when a disruptive discharge occurs through a solid dielectric and produces permanent loss of dielectric strength; in a liquid or gaseous dielectric, the loss may be only temporary.[C62.11-2005]

Qquadrant

When the principal voltage-current characteristic is expressed graphically, the voltage, v, and current, I, axes create four areas called quadrants. These quadrants are numbered counter clockwise as 1 through 4. The characteristic occurs in quadrant 1, +v and +i, and quadrant 3, -v and -i.[62.37-1996]

Rradio-influence voltage (RIV)

A high-frequency voltage, generated by all sources of ionization current, that appears at the terminals of electric-power apparatus or on power circuits.[C62.11-2005]

rated average power dissipationPM(AV)

Maximum average power dissipation in the device due to repetitive pulses at a specified current and temperature without causing device failure.[C62.35-2010]

rated dc voltage (Varistor)Vm(dc)

Maximum continuous dc voltage which may be applied. [C62.33-1982]

rated forward surge currentIFSM

Maximum peak current of specified wave shape through the unidirectional device during its forward conduction mode without causing device failure.[C62.35-2010]

rated peak impulse current

46


IPPM

Rated maximum value of peak impulse current (IPP) of specified wave shape that may be applied without causing device failure.[C62.35-2010]

rated peak impulse powerPPPM

Product of rated peak impulse current (IPPM) and clamping voltage (VC): PPPM = IPPM x VC.NOTE 1—For this calculation the value of VC is measured with IPP equal to IPPM.NOTE 2—PPPM is a fictive value as the peak values of current and voltage do not occur at the same time.[C62.35-2010]

rated peak single pulse transient current (Varistor)ItmMaximum peak current which may be applied for a single 8/20 µs impulse, with rated line voltage also applied, without causing device failure.[C62.33-1982]

rated peak single-pulse transient currentMaximum peak current that may be applied for a single 8/20 µs impulse, with rated line voltage also applied, without causing device failure. [C62.41.1-2002]

rated recurrent peak voltage (Varistor)Vpm

Maximum recurrent peak voltage which may be applied for a specified duty cycle and waveform. [C62.33-1982]

rated RMS Voltage (Varistor)V m(ac)

Maximum continuous sinusoidal rms voltage which may be applied.[C62.33-1982]

rated single pulse transient energy (Varistor)Wtm

Energy which may be dissipated for a single impulse of maximum rated current at a specified waveshape, with rated rms voltage or rated dc voltage also applied, without causing device

47


failure. [C62.33-1982]

rated single-pulse transient energyEnergy that may be dissipated for a single impulse of maximum rated current at a specified wave shape, with rated root-mean-square (rms) voltage or rated dc voltage also applied, without causing device failure. [C62.41.1-2002]

rated standby power dissipationThe power dissipated in a protective device while connected to an ac line having a voltage and frequency equal to the rating of the device and with no load current flowing and no surges applied. [C62.41.1-2002]

rated standoff (working) voltageVWM

Maximum peak working or DC voltage which may be continuously applied to the device.[C62.35-2010]

rated test voltage (rotating electric machinery)The rms fundamental frequency test voltage specified for the rated voltage, V, of the machine in the standard under which the machine is manufactured.[C62.21-2003]

rated transient average power dissipation (Varistor)Pt(AV)m

Maximum average power which may be dissipated due to a group of pulses occurring within a specified isolated time period, without causing device failure. [C62.33-1982]

rated voltageThe designated maximum permissible root-mean-square (rms) value of power-frequency voltage between its line and earth terminals at which it is designed to operate correctly. [C62.41.1-2002]

rated voltage (rotating electric machinery)The rms voltage specified at the terminals of a machine, V.[C62.21-2003]

48


ratingThe designation of an operating limit for a device. [C62.41.1-2002]

ratingThe designation of an operating limit for a device.[C62.11-2005]

ratingThe nominal value of any electrical, thermal, mechanical, or environmental quantity assigned to define the operating conditions under which a component, machine, apparatus, electronic device, etc., is expected to give satisfactory service.NOTE: Rating is a generic term, but also see maximum rating.[62.37-1996]

recovery voltageThe voltage that occurs across the terminals of a pole of a circuit-interrupting device upon interruption of the current.NOTE: For an arrester, this occurs as a result of interruption of the follow current. [C62.41.1-2002]

reference currentIref

The peak value of the resistive component of a power-frequency current high enough to make the effects of stray capacitance of the arrester negligible. This current level shall be specified by the manufacturer.NOTE: Depending on the arrester design, the reference current will typically be in the range of 0.05 mA to 1.0 mA per square centimeter of disk area.[C62.11-2005]

reference voltageVref

The lowest peak value independent of polarity of power-frequency voltage, divided by the square root of 2, required to produce a resistive component of current equal to the reference current of the arrester or arrester element. The reference voltage of a multi-unit arrester is the sum of the reference voltages of the series units. The voltage level shall be specified by the manufacturer.[C62.11-2005]

49


reignitionA resumption of current between the contacts of a switching device during an opening operation after an interval of zero current of less than 1/4 cycle at normal frequency.[C62.21-2003]

remote earth (potential)The location outside the influence of local grounds. Always assumed to be at zero potential.[C62.23-1995]

remote surge (rotating electric machinery)A surge that originates at least one voltage transformation removed from the machine.[C62.21-2003]

repetitive peak forward currentIFRM

Rated maximum (peak) value of ac power frequency forward current of specified wave shape and frequency which may be applied continuously.[62.37-1996]

repetitive peak off-state currentIDRM

The maximum (peak) value of off-state current that results from the application of the repetitive peak off-state voltage.[62.37-1996]

repetitive peak off-state voltageVDRM

Rated maximum (peak) continuous voltage that may be applied in the off-state conditions including all dc and repetitive alternating voltage components.[62.37-1996]

repetitive peak on-state currentITRM

Rated maximum (peak) value of ac power frequency on-state current of specified wave shape and frequency which may be applied continuously.[62.37-1996]

repetitive peak reverse current

50


IRRM

The maximum (peak) value of reverse current that results from the application of the repetitive peak reverse voltage, VRRM.[62.37-1996]

repetitive peak reverse voltageVRRM

Rated maximum (peak) continuous voltage that may be applied in the reverse blocking direction including all dc and repetitive alternating voltage components.[62.37-1996]

repetitive ratingA maximum rating that may be continuously applied to the thyristor.[62.37-1996]

repetitive surge and follow-current withstandThe number of surges of specified voltage and current amplitudes and wave shapes that may be applied to a device without causing degradation beyond specified limits. The repetitive surge and follow-current withstand applies to a device connected to an ac line of specified characteristics and for pulses applied at specified rates and phase angles. The effects of any cumulative heating that may occur are included. [C62.41.1-2002]

resistance (Varistor)Rx

Static resistance of the varistor at a given operating point as defined by:Rx = dVx/dIx[C62.33-1982]

resonant grounded neutral systemA system in which one or more neutral points are connected to ground through reactors that approximately compensate the capacitive component of a single-phase-to-ground-fault current.NOTE — With resonant grounding of a system, the fault current is limited such that an arc fault in air will be self-extinguishing. [C62.82.1-2010]

response time (Varistor)The time between the point at which the wave exceeds the clamping voltage level (VC) and the peak of the voltage overshoot. For the purpose of this definition, clamping voltage is defined

51


with a 8/20 µs current waveform of the same peak current amplitude as the waveform used for this response time. [C62.33-1982]

restrikeA resumption of current between the contacts of a switching device during an opening operation after an interval of zero current at 1/4 cycle at normal frequency or longer.[C62.21-2003]

reverse direction1) The direction of current in a p-n junction that results when the n-type semiconductor region is at a positive potential relative to the p-type region.2) The direction of current in a semiconductor device that results when the n-type semiconductor region connected to one terminal is at a positive potential relative to the p-type region connected to the other terminal.NOTE: This definition may not apply if one or more junctions are connected in series with at least one other junction whose p and n regions are reversed.[62.37-1996]

reverse-blocking diode thyristor surge protection device (SPD)A two-terminal thyristor SPD that exhibits a blocking state for positive cathode voltage.[62.37-1996]

reverse-blocking quadrantQuadrant 3 of the principal voltage-current characteristic in which the device exhibits a reverse blocking state.[62.37-1996]

reverse-blocking triode thyristor surge protection device (SPD)A three-terminal thyristor SPD that exhibits a blocking state for positive cathode voltage.[62.37-1996]

ring waveAn open-circuit voltage wave characterized by a rapid rise to a defined peak value, followed by a damped oscillation in which every successive peak has an amplitude of about 60% of the value of the peak that preceded it. For the 100 kHz Ring Wave, the rise time is nominally 0.5 µs and the ringing frequency is approximately 100 kHz. No short-circuit current waveform is defined; the exact wave that is delivered is determined by the instantaneous impedance to which the

52


Ring Wave is applied. [C62.41.1-2002]

riser pole type arresterAn arrester for pole mounting most often used to protect underground distribution cable and equipment.[C62.22-2009]

routine testsTests made by the manufacturer on every device or representative samples, or on parts or materials, as required, to verify that the product meets the design specifications. [C62.41.1-2002]

routine testsTests made by the manufacturer on every device or on representative samples, or on parts or materials as required to verify that the product meets the design specifications.[C62.34-1996]

routine testsTests made by the manufacturer on every device or representative samples, or on parts or materials, as required, to verify that the product meets the design specifications.[C62.11-2005]

Ssecondary arrester

A surge-protective device that is intended to be connected to the low-voltage ac supply mains (1000 V rms and less, frequency between 48 Hz and 62 Hz) at locations between and including the secondary terminals of the distribution transformer and the main service entrance panel.[C62.34-1996]

self-restoring insulationInsulation that completely recovers its insulating properties after a disruptive discharge caused by the application of a test voltage; insulation of this kind is generally, but not necessarily, external insulation. [C62.82.1-2010]

self-restoring insulationInsulation that completely recovers its insulating properties after a disruptive discharge caused by the application of an overvoltage; insulation of this kind is generally, but not necessarily,

53


external insulation.[C62.22-2009]

series gapIntentional gap(s) between spaced electrodes in series with the valve elements across which all or part of the impressed arrester terminal voltage appears.[C62.11-2005]

series gapAn intentional gap between spaced electrodes: It is in series with the valve or expulsion element of the arrester, substantially isolating the element from line or ground, or both, under normal line-voltage conditions. [C62.41.1-2002]

series gapAn intentional gap(s) between spaced electrodes in series with the valve elements across which all or part of the impressed arrester terminal voltage appears.[C62.22-2009]

service entrance equipmentThe necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service entrance conductors to a building facility, or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the electrical service supply. [C62.72-2007]

service equipmentThe necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuses and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control or cutoff of the supply. [C62.41.1-2002]

service voltageThe voltage at the point where the electric system of the supplier and the electric system of the user are connected. [C62.41.1-2002]

severe lightning current

54


Lightning currents greater than 65 kA but not greater than 100 kA. See also: normal lightning current.[C62.11-2005]

shield wire (electromagnetic fields)A wire employed to reduce the effects on electric supply or communication circuits from extraneous sources.[C62.23-1995]

shielding angleThe angle between a vertical line through the overhead ground wire and a line connecting the overhead ground wire to the shielded conductor.[C62.23-1995]

short circuitAn abnormal connection of relatively low impedance, whether made accidentally or intentionally, between two points of different potential in a circuit.[C62.31-2006]

short-circuit current (SCC)The current that the test set-up (surge generator, coupling circuit, back filter, connecting leads) can deliver at the terminals where the surge protective device (SPD) under test will be connected, with the SPD replaced by bonding the two lead terminals. (Sometimes abbreviated as “SCI.”) [C62.41.1-2002]

short-circuit current rating (SCCR) of a surge-protective deviceThe level at which a surge-protective device (SPD) is suitable for use on an ac power circuit that is capable of delivering not more than the declared root-mean-square symmetrical current at a declared voltage during a short-circuit condition. [C62.72-2007]

short-circuit current rating (SCCR) of an SPDThe level at which a surge-protective device (SPD) is suitable for use on an ac power circuit that is capable of delivering not more than the declared root-mean-square symmetrical current at a declared voltage during a short-circuit condition.[C62.62-2010]

shunt gap

55


Intentional gap(s) between spaced electrodes that is electrically in parallel with one or more valve elements.[C62.11-2005]

sparkoverA disruptive discharge between electrodes of a measuring gap, voltage control gap, or protective device.[C62.31-2006]

stand-by currentIDCurrent that flows through the device at rated stand-off voltage at the specified temperature.NOTE 1—It may also be called leakage current (IR).[C62.35-2010]

stand-off (nonconducting) regionThe portion of the volt-ampere characteristic occurring in a reverse-biased p-n junction where there is a high resistance to the passage of current. [C62.35-2010]

standard chopped wave impulse voltage shapeA standard lightning impulse that is intentionally interrupted on the tail by sparkover of a gap or other equivalent chopping device. Usually the time to chop is 2 µs to 3 µs. [C62.82.1-2010]

standard lightning impulseThe wave shape of the standard impulse used is 1.2/50 µs (when not in conflict with products standards).[C62.22-2009]

standard lightning impulse voltage shapeAn impulse that rises to crest value of voltage in 1.2 µs (virtual time) and drops to 0.5 crest value of voltage in 50 µs (virtual time), both times being measured from the same origin and in accordance with established standards of impulse testing techniques. It is described as a 1.2/50 impulse. [C62.82.1-2010]

standard power-frequency short-duration voltage shape

56


A sinusoidal voltage with frequency between 48 Hz and 62 Hz, and duration of 60 s. [C62.82.1-2010]

standard switching impulse voltage shapeA full impulse having a time-to-crest of 250 µs and a time-to-half value of 2500 µs. It is described as a 250/2500 impulse.NOTE — Some apparatus standards use a modified waveshape where practical test considerations or particular dielectric strength characteristics make some modification imperative (see IEEE Std 4-1995). [C62.82.1-2010]

standard switching impulsesThe wave shapes of standard impulse tests depend on equipment being tested:a) For air insulation and switchgear: 250/2500 µsb) For transformer products: 100/1000 µsc) For arrester sparkover tests: 1) 30-60/90-180 µs 2) 50-300/400-900 µs 3) 1000-2000/3000-6000 µs (The tail duration is not critical)[C62.22-2009]

statistical basic lightning impulse insulation level (BIL)Applicable specifically to self-restoring insulations. The crest value of a standard lightning impulse for which the insulation exhibits a 90% probability of withstand (or a 10% probability of failure) under specified conditions. See also: conventional basic lightning impulse insulation level (BIL).NOTE: See ANSI Std C62.2-1987..[C62.11-2005]

statistical basic switching impulse insulation level (BSL)Applicable specifically to self-restoring insulations. The crest value of a standard switching impulse for which the insulation exhibits a 90% probability of withstand (or a 10% probability of failure) under specified conditions. See also: conventional basic switching impulse insulation level (BSL).NOTE: See ANSI Std C62.2-1987.[C62.11-2005]

statistical BIL

57


The crest values of a standard lightning impulse for which the insulation exhibits a 90% probability of withstand (or a 10% probability of failure) under specified conditions applicable specifically to self-restoring insulation. [C62.82.1-2010]

statistical BILThe crest values of a standard lightning impulse for which the insulation exhibits a 90% probability of withstand (or a 10% probability of failure) under specified conditions, applicable specifically to self-restoring insulations.[C62.22-2009]

statistical BSLThe crest value of a standard switching impulse for which the insulation exhibits a 90% probability of withstand (or a 10% probability of failure), under specified conditions applicable to self-restoring insulation. [C62.82.1-2010]

statistical BSLThe crest value of a standard switching impulse for which the insulation exhibits a 90% probability of withstand (or a 10% probability of failure), under specified conditions, applicable to self-restoring insulations.[C62.22-2009]

statistical withstand voltageThe voltage that an insulation is capable of withstanding with a given probability of failure, corresponding to a specified probability of failure (e.g., 10%, 0.1%).[C62.82.1-2010]

statistical withstand voltageThe voltage that an insulation is capable of withstanding with a given probability of failure, corresponding to a specified probability of failure (e.g., 10%, 0.1%).[C62.22-2009]

steep-front surge (rotating electric machinery)A voltage surge having a rise time of less than one microsecond.[C62.21-2003]

surge

58


A transient wave of current, potential, or power in an electric circuit.[C62.22-2009]

surgeA transient wave of voltage or current. (The duration of the surge is not tightly specified but is usually less than a few milliseconds.) [C62.72-2007]

surgeA transient wave of current, potential, or power in an electric circuit. NOTE: The use of this term to describe a momentary overvoltage consisting of a mere increase of the mains voltage for several cycles is deprecated. See also: swell. [C62.41.1-2002]

surgeA transient wave of current, potential, or power in an electric circuit.[C62.11-2005]

surgeA transient wave of voltage or current. The duration of a surge is not tightly specified, but it is usually less than a few milliseconds.[C62.34-1996]

surgeA transient wave of current, potential, or power in an electric circuit.[62.37-1996]

surge arresterA protective device for limiting surge voltages on equipment by discharging or bypassing surge current; it limits the flow of power follow current to ground, and is capable of repeating these functions as specified.[C62.22-2009]

surge arresterA protective device for limiting surge voltages on equipment by diverting surge current and returning the device to its original status. It is capable of repeating these functions as specified.NOTE: Hereafter, the term arrester as used in this standard shall be understood to mean surge arrester.[C62.11-2005]

59


surge let-throughThe part of the surge that passes by a surge protective device (SPD) with little or no alteration. See also: surge remnant. [C62.41.1-2002]

surge protective device (SPD)a) A device intended either to limit transient overvoltages or divert surge currents, or both. It contains at least one nonlinear component.b) An assembly of one or more components intended to limit or divert surges. The device contains at least one nonlinear component.c) A device that is intended to limit transient overvoltages and divert surge currents. It contains at least one nonlinear component. [C62.41.1-2002]

surge protectorA specific complete surge-protective device, as opposed to a component of a surge protector or a generic surge-protective device.[ C62.42-2005]

surge protectorAn assembly of protective devices consisting of one or more series, parallel, or any combination of elements used to limit surge voltages, currents, or both to a specified level. Syn: protector.[C62.36-2000]

surge protectorA protective device, consisting of one or more surge-protective device components, a mounting assembly, optional fuses and short-circuiting devices, etc, which is used for limiting surge voltages on low-voltage (<1000 V rms or <1200 V dc) electrical and electronic equipment or circuits.[C62.31-2006]

surge remnantThe part of an applied surge that remains downstream of one or several protective devices. See also: surge let-through. [C62.41.1-2002]

surge response voltage

60


The voltage profile appearing at the output terminals of a surge protective device (SPD) and applied to downstream loads, during and after a specified impinging surge, until normal, stable conditions are reached. [C62.41.1-2002]

surge-protective deviceAn assembly of one or more components intended to limit or divert surges. The device contains as least one nonlinear component. [C62.72-2007]

surge-protective device (SPD)A device that is intended to limit transient overvoltages and divert surge current. It contains at least one nonlinear component.[C62.34-1996]

swellA momentary increase in the power-frequency voltage delivered by the mains, outside of the normal tolerances, with a duration of more than one cycle and less than a few seconds. See also: surge. [C62.41.1-2002]

switching currentISThe instantaneous current flowing through the device at the switching voltage, VS.[62.37-1996]

switching impulse protective level of a surge-protective deviceThe maximum switching impulse expected at the terminals of a surge-protective device under specified conditions of operation.NOTE — The switching impulse protective levels given by the higher of either: 1) the switching impulse discharge voltage for a specified current magnitude and waveshape, or 2) the switching impulse sparkover voltage for a specified voltage waveshape. [C62.82.1-2010]

switching overvoltageA transient overvoltage in which a slow front, short-duration, unidirectional or oscillatory, highly damped voltage is generated (usually by switching or faults). [C62.82.1-2010]

61


switching overvoltageAny combination of switching surge(s) and temporary overvoltage(s) associated with a single switching episode.[C62.22-2009]

switching pointThe point in the principal voltage-current characteristic which the thyristor regenerates and initiates switching into the on-state. This point occurs at the termination of the breakdown region and the start of the negative differential-resistance region.[62.37-1996]

switching quadrantA quadrant of the principal voltage-current characteristic in which the device is intended to switch between the off-state and the on-state. For a bi-directional thyristor the switching quadrants will be 1 and 3. For a reverse blocking or reverse conducting thyristor the switching quadrant will be quadrant 1. For a forward conducting thyristor the switching quadrant will be quadrant 3.[62.37-1996]

switching resistanceRs

The equivalent slope resistance of the breakdown region, RS, computed by (V(BO) - VS) / (IS - I(BO))[62.37-1996]

switching surgeA heavily damped transient electrical disturbance associated with switching. System insulation flashover may precede or follow the switching in some cases but not all.[C62.22-2009]

switching voltageVS

The instantaneous voltage across the device at the final point in the breakdown region prior to switching into the on-state.[62.37-1996]

system (circuit) voltageThe root-mean-square (rms) power-frequency voltage from line to line as distinguished from the voltage from line to neutral.[C62.41.1-2002]

62


system voltageThe root-mean-square (rms) phase-to-phase power frequency voltage on a three-phase alternating-current electric system.[C62.22-2009]

system voltageThe root-mean-square (rms) power-frequency voltage from line to line as distinguished from the voltage from line to neutral.[C62.11-2005]

system voltageThe rms power-frequency voltage from line-to-line as distinguished from the voltage from line- to-neutral. [C62.72-2007]

Ttemperature coefficient of breakdown voltage

αV(BR), dV(BR)/dTJ

Ratio of the change in breakdown voltage, V(BR), to the change in temperature.NOTE—Expressed as either millivolts per Kelvin (mV/K) or per cent per Kelvin (%/K) with reference to the 25 °C value of breakdown voltage. Alternatives to mV/K and %/K are mV/°C and %/°C.[C62.35-2010]

temperature coefficient of breakdown voltageαV(BR); dV(BR)/dTJ

The ratio of the change in breakdown voltage, V(BR), to changes in temperature. Expressed as either millivolts per degree Celsius (mV/°C), or percent per degree Celsius (%/°C) with reference to the 25 °C value of breakdown voltage (mV/°C or %/°C).[62.37-1996]

temperature deratingChange of ratings with temperature above a specified base temperature.NOTE 1—Expressed in percentage of the rating at the base temperature.[C62.35-2010]

temperature derating

63


Derating with temperature above a specified base temperature, expressed as a percentage, such as may be applied to peak pulse current[62.37-1996]

temporary overvoltageAn oscillatory phase-to-ground or phase-to-phase overvoltage that is at a given location of relatively long duration (seconds, even minutes) and that is undamped or only weakly damped. Temporary overvoltages usually originate from switching operations or faults (e.g., load rejection, single-phase fault, fault on a high-resistance grounded or ungrounded system) or from nonlinearities (ferroresonance effects, harmonics), or both. They are characterized by the amplitude, the oscillation frequencies, the total duration, or the decrement. [C62.82.1-2010]

temporary overvoltage (TOV)An oscillatory overvoltage, associated with switching or faults (for example, load rejection, single-phase faults) and/or nonlinearities (ferroresonance effects, harmonics), of relatively long duration, which is undamped or slightly damped.[C62.22-2009]

terminalsThe conducting parts provided for connecting the arrester across the insulation to be protected.[C62.11-2005]

thermal resistanceRθJL, RθJC, RθJA

Effective temperature rise per unit power dissipation of a designated junction, above the temperature of a stated external reference point (lead, case or ambient) under conditions of thermal equilibrium.[C62.35-2010]

thermal resistanceRθJL; RθJC; RθJA

The effective temperature rise per unit power dissipation of a designated junction, above the temperature of a stated external reference point (lead, case, or ambient) under conditions of thermal equilibrium.[62.37-1996]

thyristor

64


A bistable semiconductor device comprising three or more junctions that can be switched from the off-state to the on-state or vise versa, such switching occurring within at least one quadrant of the principal voltage-current characteristic.[62.37-1996]

time-to-crest valueTr

The time that an impulse rises to crest value. [C62.82.1-2010]

time-to-half valueTh

The time that an impulse drops to 0.5 crest value. [C62.82.1-2010]

time-to-impulse sparkoverThe time between virtual zero of the voltage impulse causing sparkover and the point on the voltage wave at which sparkover occurs.[C62.11-2005]

trackingIrreversible degradation of surface material from the formation of conductive carbonized paths.[C62.11-2005]

transfer timeThe time duration of the transverse voltage.[C62.31-2006]

transient overvoltageA short-duration highly damped, oscillatory or nonoscillatory overvoltage, having a duration of few milliseconds or less. Transient overvoltage is classified as one of the following types: lightning, switching and very fast front, short duration. [C62.82.1-2010]

transient thermal impedanceZθJL, ZθJC, ZθJA

change in the difference between the virtual junction temperature and the temperature of a specified reference point or region (lead, case, or ambient) at the end of a time interval divided by the step function change in power dissipation at the beginning of the same time interval

65


which causes the change of temperature-difference.NOTE—It is the thermal impedance of the junction under conditions of change and is generally given in the form of a curve as a function of the duration of an applied pulse.[C62.35-2010]

transient thermal impedanceZθJL(t); ZθJC(t); ZθJA(t)

The change in the difference between the virtual junction temperature and the temperature of a specified reference point or region (lead, case, or ambient) at the end of a time interval divided by the step function change in power dissipation at the beginning of the same time interval that causes the change of temperature-difference.NOTE: It is the thermal impedance of the junction under conditions of change and is generally given in the form of a curve as a function of the duration of an applied pulse.[62.37-1996]

transient voltage surge suppressor (TVSS)A device that functions as a surge-protective device (SPD) or surge suppressor. [C62.72-2007]

transition currentThe current required at a given temperature and duration to cause a current-protective device to change state.[C62.36-2000]

transition timeThe time required for the voltage across a conducting gap to drop into the arc region after the gap initially begins to conduct.[C62.31-2006]

transmission line arresterA surge arrester installed on a transmission line, usually for the purpose of protecting transmission line insulation.[C62.22-2009]

traveling waveThe resulting wave when an electrical variation in a circuit such as a transmission line takes the form of translation of energy along a conductor, such energy being always equally divided between current and potential forms.[C62.22-2009]

66


turn insulation (rotating electric machinery)The insulation applied to provide electrical separation between the turns of a coil.NOTE: In the usual case, the insulation encircles each turn. It is sometimes referred to as turn-to-turn insulation.[C62.21-2003]

two-port SPDAn SPD with two sets of terminals, input and output. A specific series impedance is inserted between these terminals.[C62.34-1996]

Type 1 SPDPermanently connected SPDs intended for installation between the secondary terminal of the supplying transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt-hour meter socket enclosures and intended to be installed without an external overcurrent protective device. [C62.62-2010]

Type 2 SPDPermanently connected SPDs intended for installation on the load side of the service equipment overcurrent device; including SPDs located at the branch panel. [C62.62-2010]

Type 3 SPDPoint of utilization SPDs, installed at a minimum conductor length of 10 meters (30 feet) from the service equipment to the point of utilization, for example cord connected, direct plug-in, receptacle type and SPDs installed at the utilization equipment being protected. The distance (10 meters) is exclusive of conductors provided with or used to attach SPDs. If the nominal discharge current test is performed on a Type 3 SPD, the minimum distance from the service equipment does not apply.[C62.62-2010]

Type 4 SPDComponent SPDs, including discrete components as well as component assemblies.[C62.62-2010]

Uultimate mechanical strength-static (UMS-static)

67


The load at which any part of the surge arrester fails to perform its mechanical function.[C62.11-2005]

ungrounded (isolated) systemA system, circuit, or apparatus without an intentional connection to ground, except through potential-indicating or measuring devices or other very-high-impedance devices. [C62.82.1-2010]

unidirectional thyristor surge protection device (SPD)A thyristor SPD that has switching characteristics in only quadrant.NOTE: The main unidirectional thyristor SPDs are the reverse-blocking, reverse conducting and forward conducting thyristor SPDs.[62.37-1996]

unit operationDischarge of a surge through an arrester while the arrester is energized.[C62.22-2009]

unit operationA discharge of a surge through an arrester while the arrester is energized.[C62.11-2005]

upsetMalfunction of a system because of electrical disturbances. [C62.41.1-2002]

utilization voltageThe root-mean-square (rms) phase-to-phase or phase-to-neutral voltage at the line terminals of utilization equipment.[C62.41.1-2002]

Vvalve arrester

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

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

68


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

Varistor voltageVX

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

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

very fast front voltage shapeThis category has not been standardized at this time. [C62.82.1-2010]

very fast front, short-duration overvoltageA 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

69


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 temperatureTJ

A theoretical temperature representing the temperature of the junction(s) calculated on the

70


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 levelA 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]

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voltage ratingThe 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 shapeA 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]

Wwave

The variation with time of current, potential, or power at any point in an electric circuit.[62.37-1996]

waveThe variation with time of current, potential, or power at any point in an electric circuit.[C62.11-2005]

wave front (of a surge or impulse)That part that occurs prior to the crest value.[C62.11-2005]

wave front (of an impulse)That part of an impulse that occurs prior to the crest value.[C62.22-2009]

wave shapeThe graph of the wave as a function of time.[62.37-1996]

wave shape (of an impulse test wave)The graph of an impulse test wave as a function of time.[C62.22-2009]

wave shape (of an impulse test wave)

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The graph of the wave as a function of time.[C62.11-2005]

wave shape designation (of an impulse)The wave shape of an impulse (other than rectangular) of a current or voltage is 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.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 1000 μs wave[C62.22-2009]

wave shape designation (of an impulse)1) The wave shape of an impulse (other than rectangular) of a current or voltage is designated by a combination of two numbers. The first, an index of the wavefront, is the virtual duration of the wavefront 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.2) 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 1000 μs wave.[62.37-1996]

wave shape designation (of an impulse)(A) The wave shape of an impulse (other than rectangular) of a current or voltage is 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.(B) 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 1000 μs wave.[C62.11-2005]

wave tail (of an impulse)

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That part between the crest value and the end of the impulse.[C62.22-2009]

wave tail (of an impulse)That part between the crest value and the end of the impulse.[C62.11-2005]

wave tail (of an impulse)That part between the crest value and the end of the impulse.[62.37-1996]

waveformA 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.[62.37-1996]

wavefront (of a surge or impulse)That part which occurs prior to the crest value.[62.37-1996]

withstand voltageThe voltage that an insulation is capable of withstanding. In terms of insulation, this is expressed as either conventional withstand voltage or statistical withstand voltage. [C62.82.1-2010]

withstand voltageThe voltage that an insulation is capable of withstanding with a given probability of failure. In terms of insulation, this is expressed as either conventional withstand voltage or statistical withstand voltage.[C62.22-2009]

withstand voltageThe voltage that an insulation is capable of withstanding. In terms of insulation, this is expressed as either conventional or statistical withstand voltage.NOTE: See IEEE Std 1313.1-1996.[C62.11-2005]

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