PD IEC PAS-60099-7:2004 pdf download Surge arresters — Part 7: Glossary of terms and definitions from IEC publications 60099-1, 60099-4, 60099-6, 61643-1, 61643-12, 61643-21, 61643-311, 61643-321, 61643-331 and 61643-341
2.1
surge arrester
device designed to protect electrical apparatus from high transient voltage and to limit theduration and frequently the amplitude of follow-current. The term “surge arrester” includes anyexternal series gap which is essential for the proper functioning of the device as installed forservice, regardless of whether or not it is supplied as an integral part of the device
NOTE Surge arresters ar usually connected between the electrical conductors of a network and earth althoughthey may sometimes be connected across the windings of apparatus or between electrical conductors.
2.2non-linear resistor type gapped arrester:arrester having a single or a multiple spark-gap connected in series with one or more noninear resistors
2.3
series gap of an arrester:intentional gap or gaps between spaced electrodes in series with the non-linear series resistoror resistors of the arrester
2.4non-linear series resistor of an arresterpart of the surge arrester which, by its non-linear voltage-current characteristics, acts as a lowresistance to the flow of high discharge currents thus limiting the voltage across the arresterterminals, and as a high resistance at normal power-frequency voltage thus limiting themagnitude of follow-current
2.5
section of an arrestercomplete, suitably housed part of an arrester including series gaps and non-linear seriesresistors in such a proportion as is necessary to represent the behaviour of a completearrester with respect to a particular test
2.6
unit of an arrester
completely housed part of an arrester which mav be connected in series with other units toconstruct an arrester of higher voltage rating, A unit of an arrester is not necessarily a sectionof an arrester
2.7
pressure-relief device of an arrester
means for relieving internal pressure in an arrester and preventing explosive shattering of thehousing following prolonged passage of follow-current or internal flashover of the arrester
2.8
rated voltage of an arresterdesignated maximum permissible r.m.s. value of power-frequency voltage between itsterminals at which it is designated to operate correctly. This voltage may be applied to thearrester continuously without changing its operating characteristics
2.9
rated frequency of an arresterfrequency of the power system on which the arrester is designed to be used
2.10disruptive dischargephenomena associated with the failure of insulation under electrical stress which include acollapse of voltage and the passage of current; the term applies to electrical breakdown insolid, liquid and gaseous dielectrics and combinations of these
NOTE A disruptive discharge in a solid dielectric produces permanent loss of electrical strength; in a liquid orgaseous dielectric the loss may be only temporary.
2.11
puncturedisruptive discharge through a solid
2.12
flashover
disruptive discharge over a solid surface
2.13
sparkover of an arresterdisruptive discharge between the electrodes of the gaps of an arrester
2.14
impulseunidirectional wave of voltage or current which, without appreciable oscillations, rises rapidlyto a maximum value and falls, usually less rapidly, to zero with small, if any, loops of oppositepolarity
The parameters which define a voltage or current impulse are polarity, peak value, front timeand time to half-value on the tail
2.15
rectangular impulse
impulse which rises rapidly to a maximum value, remains substantially constant for a specified