>> P.7
Failureoftechnicalinstallationsandsystemsinresidentialandfunctionalbuildingsisveryunpleasantandexpensive.Therefore,faultlessoperationofdevicesmustbeensuredbothduringnormaloperationandthunder-storms.Aprofessionalsolutionallowstotakeadequateprotectionmeasures.Thelightningprotectionzoneconcept,forexample,enablesdesigners,constructorsandoperatorsofbuildingsandinstallationstoconsider,implementandmonitordifferentprotectionmeasures.Allrelevantdevices,installationsandsystemsarethusreliablyprotectedatareasonableexpense.SourcesofinterferenceSurgesoccurringduringathunderstormarecausedbydirect/nearbylightningstrikesorremotelightningstrikes.Directornearbylightningstrikesarelightningstrikestoabuilding,itssurroundingsorelectricallyconductivesystemsenteringthebuilding(e.g.low-voltagesupply,telecommunicationanddatalines).TheresultingimpulsecurrentsandimpulsevoltagesaswellastheassociatedLightningElectromagneticPulse(LEMP)areparticularlydangerousforthedevicestobeprotectedwithregardtotheamplitudeandenergycontentinvolved.Incaseofadirectornearbylightningstrike,surgesarecausedbythevoltagedropattheconventionalearthingimpedanceRstandtheresultingpotentialriseofthebuildinginrelationtotheremoteearth.Thismeansthehighestloadforelectricalinstallationsinbuildings.Thecharacteristicparametersoftheimpulsecurrentpresent(peakvalue,rateofcurrentrise,charge,specificenergy)canbedescribedbymeansofthe10/350simpulsecurrentwaveform.Theyhavebeendefinedininternational,Europeanandnationalstandardsastestcurrentforcomponentsanddevicesprotectingagainstdirectlightningstrikes.Inadditiontothevoltagedropattheconventionalearthingimpedance,surgesaregeneratedintheelectricbuildinginstallationandthesystemsanddevicesconnectedtoitduetotheinductiveeffectoftheelectromagneticlightningfield.Theenergyoftheinducedsurgesandoftheresultingimpulsecurrentsisfarlowerthantheenergyofadirectlightningimpulsecurrentandisthereforedescribedbya8/20simpulsecurrentwaveform.Componentsanddevicesthatdonothavetoconductcurrentsresultingfromdirectlightningstrikesarethereforetestedwithsuch8/20simpulsecurrents.Directlightningstrikesareacommoncauseforbuildingfiresandmechanicaldamagetobuildings.Thiscanbepreventedbyanexternallightningprotectionsystem.Nevertheless,thelightningcurrentsflowingincaseofadirectlightningstrikecausealocalpotentialriseoftheearthpotentialintheprotectedbuilding.Asaresult,flashovertosupplysystemsenteringthebuildingmayoccur.Therefore,lightningcurrentarrestersmustbeinstalledtoprotectelectricalinstallationsandsystems.Nearbylightningstrikescausetransientvoltageimpulsesonthesupplylinesofthebuildingduetothehighlightningelectromagneticfield(LEMP).Thesevoltageimpulsescanreachpeakvaluesofseveral1,000volts.Surgearrestersforpowersupplyandinformationtechnologysystemsarerequiredtoprotectelectricalinstallationsandsystems.PowerlineCommunicationlineLightningstrikeLargecurrentandVoltagegeneratedIntrusionthroughpowerline/CommunicationlineChangesinspatialelectromagneticfields7
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