>> P.8
10/350µswaveform:TheLightningcurrentsthatcanoccurwithadirectlightningstrikecanbesimulatedwiththesurgecurrentof10/350µswaveform.TheClass1SPDforprotectionofdirectlightningsurgesandexternallightningprotectioncomponentsaretestedusingthiswaveform.8/20µswaveform:Thesurgescreatedbyremotelightningstrikesandswitchingoperations-indirectlightningsurges-aresimulatedwiththetestimpulseof8/20µswaveform.TheSPDsofClass2and3aretestedwiththistestimpulse.ThetypesofSPDsarecategorizedbytestingcurrentshavingwaveformssimulatingthecharacteristicsandenergysizeoftheimpulsecurrents.10/350sWaveform8/20sWaveform100%50%Current020sTime200s350somparisonofsandswaveformProtectionschemeWaveformsoftheSurgesLightningstrikesarecalledremoteiftheyoccuratafarerdistancetotheobjecttobeprotected,strikemedium-voltageoverheadlinesortheirsurroundingsoroccurascloud-to-cloudlightningdischarges.Similartoinducedsurges,theeffectsofremotelightningstrikesontheelectricalinstallationofabuildingarehandledbydevicesandcomponentswhichhavebeendimensionedaccordingto8/20µsimpulsecurrentwaves.Surgescausedbyswitchingoperations(SEMP)are,forexample,generatedby:•Disconnectionofinductiveloads(e.g.transformers,reactors,motors)•Arcignitionandinterruption(e.g.arcweldingequipment)•TrippingoffusesTheeffectsofswitchingoperationsintheelectricalinstallationofabuildingcanalsobesimulatedbyimpulsecurrentsof8/20µswaveformundertestconditions.Toensurecontinuousavailabilityofcomplexpowersupplyandinformationtechnologysystemsevenincaseofdirectlightninginterference,furthersurgeprotectionmeasuresforelectricalandelectronicinstallationsanddevicesbasedonalightningprotectionsystemforthebuildingarerequired.Itisimportanttotakeallcausesofsurgesintoaccount.Todoso,thelightningprotectionzoneconceptasdescribedinIEC62305-4isapplied.8
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