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Terms and definitions -1/2

Terms and definitions of IEC 61643-11: LOW-VOLTAGE SURGE PROTECTIVE DEVICES (1/2)


                                                           Part 11: Surge protective devices connected to low-voltage power systems –Requirements and test methods

 Terms and definitions

 3.1.1 surge protective device


device that contains at least one nonlinear component that is intended to limit surge voltages and divert surge currents

NOTE: An SPD is a complete assembly, having appropriate connecting means.

3.1.2 one-port SPD

SPD has no intended series impedance

NOTE A one-port SPD may have separate input and output connections.

3.1.3 two-port SPD

SPD has a specific series impedance connected between separate input and output


3.1.4 voltage switching type SPD

SPD that has a high impedance when no surge is present but can have a sudden change in

impedance to a low value in response to a voltage surge

NOTE: Common examples of components used in voltage-switching type SPDs are spark gaps, gas tubes and thyristors. These are sometimes called "crowbar type" components.

3.1.5 voltage limiting type SPD

SPD that has a high impedance when no surge is present but will reduce it continuously with increased surge current and voltage

NOTE Common examples of components used in voltage-limiting type SPDs are varistors and avalanche breakdown diodes. These are sometimes called "clamping type" components.

3.1.6 combination type SPD

SPD incorporates both, voltage switching components and voltage limiting components. The SPD may exhibit voltage switching, limiting or both

3.1.7 short-circuiting type SPD

SPD is tested according to Class II tests which change its characteristic to an intentional

internal short-circuit due to a surge current exceeding its nominal discharge current In

3.1.8 mode of protection of an SPD

an intended current path, between terminals that contains protective components, e.g. line-to line, line-to-earth, line-to-neutral, neutral-to-earth.

3.1.9 nominal discharge current for class II test


crest value of the current through the SPD having a current waveshape of 8/20– 12 –

61643-11 IEC:2011

3.1.10 impulse discharge current for class I test


crest value of a discharge current through the SPD with specified charge transfer Q and

specified energy W/R in the specified time

3.1.11 maximum continuous operating voltage


maximum r.m.s. voltage, which may be continuously applied to the SPD's mode of protection

NOTE The UC value covered by this standard may exceed 1 000 V.

3.1.12 follow current


peak current supplied by the electrical power system and flowing through the SPD after a

discharge current impulse

3.1.13 rated load current


maximum continuous rated r.m.s. current that can be supplied to a resistive load connected to the protected output of an SPD

3.1.14 voltage protection level


maximum voltage to be expected at the SPD terminals due to an impulse stress with defined voltage steepness and an impulse stress with a discharge current with a given amplitude and waveshape

NOTE The voltage protection level is given by the manufacturer and may not be exceeded by: – the measured limiting voltage, determined for front-of-wave sparkover (if applicable) and the measured limiting voltage, determined from the residual voltage measurements at amplitudes corresponding to I n and/or I imp respectively for test classes II and/or I; – the measured limiting voltage at UOC, determined for the combination wave for test class III.

3.1.15 measured limiting voltage

The highest value of voltage that is measured across the terminals of the SPD during the

application of impulses of specified waveshape and amplitude

3.1.16 residual voltage


crest value of voltage that appears between the terminals of an SPD due to the passage of

discharge current

3.1.17 temporary overvoltage test value


test voltage applied to the SPD for a specific duration tT, to simulate the stress under TOV conditions

3.1.18 load-side surge withstand capability for a two-port SPD

the ability of a two-port SPD to withstand surges on the output terminals originating in circuitry

downstream of the SPD IEC61643-11  IEC:2011

3.1.19 voltage rate-of-rise of a two-port SPD

rate of change of voltage with time measured at the output terminals of a two-port SPD under specified test conditions

3.1.20 1,2/50 voltage impulse

voltage impulse with a nominal virtual front time of 1,2 µs and a nominal time to half-value of 50 µs

NOTE: The Clause 6 of IEC 60060-1 (1989) defines the voltage impulse definitions of front time, time to halfvalue and waveshape tolerance.

3.1.21 8/20 current impulse

current impulse with a nominal virtual front time of 8 µs and a nominal time to half-value of

20 µs

NOTE: The Clause 8 of IEC 60060-1 (1989) defines the current impulse definitions of front time, time to half-value and waveshape tolerance.

3.1.22 combination wave

a wave characterized by defined voltage amplitude (UOC) and waveshape under open-circuit conditions and a defined current amplitude (ICW) and waveshape under short-circuit conditions

NOTE The voltage amplitude, current amplitude and waveform that is delivered to the SPD are determined by the combination wave generator (CWG) impedance Zf and the impedance of the DUT.

3.1.23 open circuit voltage


open circuit voltage of the combination wave generator at the point of connection of the

device under test

3.1.24 combination wave generator short-circuit current


prospective short-circuit current of the combination wave generator, at the point of connection of the device under test

NOTE When the SPD is connected to the combination wave generator, the current that flows through the device is generally less than I cw.

3.1.25 thermal stability

SPD is thermally stable if, after heating up during the operating duty test, its temperature

decreases with time while energized at specified maximum continuous operating voltage and at specified ambient temperature conditions

3.1.26 degradation (of performance)

undesired permanent departure in the operational performance of equipment or a system from its intended performance

3.1.27 short-circuit current rating


maximum prospective short-circuit current from the power system for which the SPD, in

conjunction with the disconnector specified, is rated– 14 – 61643-11  IEC:2011

3.1.28 SPD disconnector (disconnector)

device for disconnecting an SPD, or part of an SPD, from the power system

NOTE This disconnecting device is not required to have isolating capability for safety purposes. It is to prevent a persistent fault on the system and is used to give an indication of an SPD’s failure. Disconnectors can be internal (built-in) or external (required by the manufacturer). There may be more than one disconnector function, for example an over-current protection function and a thermal protection function. These functions may be in separate units.

3.1.29 degree of protection of the enclosure


classification preceded by the symbol IP indicating the extent of protection provided by an enclosure against access to hazardous parts, against ingress of solid foreign objects and

possibly harmful ingress of waterers' specifications. Imax is equal to or greater than In.

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