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ProcedureforIEEE1584basedarcflashcalculations.

Normalizedincidentenergycanbefoundusingtheequationbelow:

lgEn=K1+K2+1.081*lgIa+0.0011*G(1)

EnincidentenergyJ/cm2normalizedfortimeanddistance.Theequationaboveisbasedondatanormalizedforadistancefromthepossiblearcpointtothepersonof610mm.andanarcingtimeof0.2sec.K1=0.792foropenconfigurations,andis0.555forboxconfigurations/enclosedequipment.K2=0forungroundedandhighresistancegroundedsystems,andequals0.113forgroundedsystems.Ggapbetweenconductorsinmillimeters.IapredictedthreephasearcingcurrentinkA.Itisfoundbyusingformula2a)orb)sotheoperatingtimeforprotectivedevicescanbedetermined.

For1000Vandlowersystems:

lgIa=K+0.662*lgIbf+0.0966*V+0.000526*G+0.5588*V*lgIbf0.00304*G*lgIbf(2a)

lgislogarithmbase10(log10).IaarcingcurrentinkA.EnnormalizedincidentenergyinJ/cm2ascalculatedby(1).Kequals0.153foropenconfigurations.and0.097forboxconfigurations.IbfboltedfaultcurrentforthreephasefaultsinkAsymmetricalrms.VsystemvoltageinkV.Ggapbetweencondactorsinmillimeters.

Solve

lgIa=0.00402+0.983*lgIbf(2b)

forapplicationswithasystemvoltagerangingfrom1upto15kV.

Incidentenergycanbefoundusingtheequationbelow:

E=4.184*Cf*En*(t/0.2)*(610x/Dx)(3)

EincidentenergyexposureinJ/cm2.Cfcalculationfactorequalto1.0forvoltagesabove1kV,and

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1.5forvoltagesbelow1kV.EnnormalizedincidentenergyinJ/cm2ascalculatedby(1)above.tarcingtimeinseconds.Ddistancefrompossiblearcingpointtothepersoninmillimeters.xdistanceexponent.

Forcaseswherevoltageisover15kV,orgapisoutsidetherangeofthemodel,thetheoreticallyderivedLeemethodcanbeapplied,andincidentenergycanbedeterminedusingtheequationbelow:

E=2.142*106*V*Ibf*(t/D2)(4)

EisincidentenergyinJ/cm2VissystemvoltageinkVtisaarcingtimeinsecondsDisdistancefrompossiblearcpointtopersoninmm.Ibfisboltedfaultcurrent

FortheIEEEStd15842002empiricallyderivedmodel,arcflashboundaryiscalculatedusingtheequationbelow:

DB=[4.184*Cf*En*(t/0.2)*(610x/EB)]1/x(5)

FortheLeemethod:

DB=[2.142*106*V*Ibf*(t/EB)]1/2(6)

DBdistanceoftheboundaryfromthearcpointinmillimeters.Cfcalculationfactorequalto1.0forvoltagesabove1kV,and1.5forvoltagesbelow1kV.EnnormalizedincidentenergyinJ/cm2ascalculatedby(1).EBincidentenergyinJ/cm2attheboundarydistance.IbfboltedfaultcurrentforthreephasefaultsinkAsymmetricalrms.tarcingtimeinseconds.xdistanceexponent.Ibfboltedfaultcurrent

EBisusualysetat5J/cm2(1.2cal/cm2)forbareskin,orattheratingofproposedpersonalprotectionequipment.

ArcFlashTerminology

IncidentEnergyExposureThisistheamountofthermalincidentenergytowhichtheworker'sfaceandchestcouldbeexposedatworkingdistanceduringanelectricalarcevent. Incident energy is measured in joules per centimeter squared

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(J/cm2)orcaloriespercentimetersquared(cal/cm2).Minimumreportedincident energy is 0.25 cal/cm2which is the accuracy limit of the testequipment.IncidentEnergyatArcFlashBoundaryAvalue incal/cm^2 todeterminearc flashboundary(AFB)distanceatthatIncidentEnergy.TheIncidentEnergyof1.2cal/cm^2forbareskinisused in solvingequation forarc flashboundary in IEEE1584Guidefor Performing Arc Flash Hazard Calculations. However, the Guideequationforarcflashboundarycanbesolvedwithotherincidentenergylevels as well such as the rating of proposed personal protectiveequipment (PPE). The Incident Energy at Arc Flash Boundary valueshouldbeequaloraboveincidentenergytoseconddegreeburnforbareskinexposure.

ArcFlashBoundaryThearcflashboundary isanapproachlimitatadistancefromexposedlivepartsorenclosedliveparts ifoperation,manipulation,or testingofequipmentcreatesapotentialflashhazard,withinwhichapersoncouldreceiveaseconddegreeburnifanelectricalarcflashweretooccur.Aworker entering the arc flash boundarymust be qualified andmust bewearing appropriate PPE. The arc flash boundary is required to becalculatedbyNFPA70E.HazardLevelThisistheminimumlevelofPersonalProtectiveEquipmentincaloriesper centimeter squared, as evaluated in IEEE Standard 1584, with theintent toprotect theworker from the thermaleffectsof thearc flashatworkingdistancefromthesourceofthearc.

MinIncidentEnergy,cal/cm^2

MaxIncidentEnergy,cal/cm^2

HazardLevelRequiredMinRatingofPPE,

cal/cm^20 Eb 0

Eb+0.001 4 1 44.001 8 2 88.001 25 3 2525.001 40 4 4040.001 andabove Consult NotAvailable

RecommendedPersonalProtectiveEquipment(PPE)HazardLevel PersonalProtectiveEquipment(PPE)

0Untreatednaturalfiberlongsleeveshirt&pantswithafabricweightofatleast4.5oz/yd^2,safetyglasses,earcanalinserts,heavydutyleathergloves.

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1Arcrated(AR)shirtandARpantsorARcoverall,ARfaceshield,ARjacket,safetyglasses,hardhat,earcanalinserts,heavydutyleathergloves,leatherfootwear.

2Arcrated(AR)shirtandARpantsorARcoverall,ARflashsuithood,ARjacket,safetyglasses,hardhat,earcanalinserts,heavydutyleathergloves,leatherfootwear.

3Arcrated(AR)coveralloverARshirtandARpants,ARflashsuit,ARhood,safetyglasses,hardhat,earcanalinserts,ARgloves,leatherfootwear.

4Multilayerarcrated(AR)flashsuitoverARcoveralloverARshirtandARpants,ARflashsuithood,safetyglasses,hardhat,earcanalinserts,ARgloves,leatherworkshoes.

EquipmentClassClasses of equipment included in IEEE 1584 and typical bus gaps areshownintablebelow:

Classesofequipment Typicalbusgaps,mmOpenAir 1040

Lowvoltageswitchgear 3215kVswitchgear 1525kVswitchgear 104

LowvoltageMCCsandpanelboards 25

Cable 13GapbetweenConductorsEquipment bus gap in mm. Gaps of 3 to 40 mm were used for lowvoltage testing to simulate gaps between conductors in low voltageequipment and cables.Gaps 13, 104 and 152mm.were used in 5 and15kVequipmenttestings.ForcaseswheregapisoutsidetherangeoftheEmpirical model, the theoretically derived Lee method can be appliedanditisnowincludedinARCAD'sarcflashassessmentsoftware.GroundingTypeTwogroundingclassesareappliedintheIEEE1584procedure,asfollows:a)Ungrounded,whichincludedungrounded,highresistancegroundingandlowresistancegrounding.b)Solidlygrounded.

WorkingDistanceTypicalworkingdistanceisthesumofthedistancebetweentheworkerstandinginfrontoftheequipment,andfromthefrontoftheequipmenttothepotentialarcsourceinsidetheequipment.

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Arcfashprotection isalwaysbasedon the incidentenergy levelon theperson's faceandbodyat theworkingdistance,not the incidentenergyon the hands or arms. The degree of injury in a burn depends on thepercentage of a person's skin that is burned. The head and body are alarge percentage of total skin surface area and injury to these areas ismuch more life threatening than burns on the extremities. Typicalworkingdistancesareshownintablebelow:

Classesofequipment Typicalworkingdistance,mmLowvoltageswitchgear 61015kV/5kVswitchgear 910

LowvoltageMCCsandpanelboards 455Cable 455

ArcDuration/TotalClearingTimeUse protective device characteristics, which can be found inmanufacturer's data. For fuses, the manufacturer's timecurrent curvesmayincludebothmeltingandclearingtime.Ifso,usetheclearingtime.Iftheyshowonlytheaveragemelttime,addtothattime15%,upto0.03seconds,and10%above0.03secondstodeterminetotalclearingtime.Ifthearcingfaultcurrent isabove the totalclearing timeat thebottomofthecurve(0.01seconds),use0.01secondsforthetime.

For circuit breakers with integral trip units, the manufacturer's timecurrentcurvesincludebothtrippingtimeandclearingtime.

Forrelayoperatedcircuitbreakers,therelaycurvesshowonlytherelayoperating time in the timedelay region. For relays operating in theirinstantaneous region, allow 16 milliseconds on 60 Hz systems foroperation. The circuit breaker opening time must be added. Openingtimes for particular circuit breakers can be verifed by consulting themanufacturer'sliterature.

Available3PhaseBoltedFaultCurrentAvailable3phaseboltedfaultcurrentfortherangeof700Ato106kAatthepointwhereworkis tobeperformedisenteredinto thisboxinkA.Example: if 42,350 amps are available, enter 42.35 into this box. If16,000 amps are available, enter 16 into this box. Please considerARCAD's short circuit calculation software to determine the availablefaultcurrentsinyourpowerdistributionsystem.Predicted3PhaseArcingCurrentThearcingcurrentdependsontheavailable3phaseboltedfaultcurrentfor the range of 700A to 106kA at the point where work is to beperformed, configuration, system voltage and gap between conductors.Leave the field blank, the program calculates the value based on thesystemparameters.Thearcdurationshouldbedeterminedbasedonthepredictedarcingcurrent.

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Writeusat:

SystemVoltageSystemLinetoLineVoltagefortherangeof208Vto15000Visenteredinto the box in Volts. For cases where voltage is over 15kV, thetheoreticallyderivedLeemethodcanbeappliedanditisnowincludedinARCAD'sarcflashassessmentsoftware.EffectofarccurrentvariationondeterminationofclearingtimeForprotectivedevicesoperatinginthesteepportionoftheirtimecurrentcurves,asmallchangeincurrentcausesabigchangeinoperatingtime.Incidentenergy is linearwith time,soarccurrentvariationmayhaveabigeffectonincidentenergy.Thesolutionistomaketwoarccurrentandenergy calculations one using the calculated expected arc current andoneusingareducedarccurrentthatis15%lower.

ARCAD's arc flash assessment software makes possible bothcalculations foreachcaseconsidered. It requires thatanoperating timebe determined for both the expected arc current and the reduced arccurrent. Incident energy is calculated for both sets of arc currents andoperating times and the larger incident energy is taken as the modelresult. This solution was developed by comparing the results of arccurrent calculations using the best available arc current equation withactualmeasuredarccurrentinthetestdatabase.

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