The New IEEE-1584 Guide For Performing Arc-Flash Calculations

Transcription

The New IEEE-1584Guide for Performing Arc-FlashCalculationsDavid Rewitzer10/21/2019

Standard differences Brief historyIEEE 1584 DefinitionsAgenda Significant differences General guide line Where arc flash and electrical safety isheading

TheStandardsWhat’s thedifference?IEEE 1584 2018Guide for Performing Arc FlashHazard CalculationsNFPA 70E 2018Governs EmployeeWorkplace Safety

D2. Lee Calculation Method (1981) Arc as a pointIEEE 15842018 D.3 Doughy Neal Paper (2000) D.3.2 Arc In open Air D.3.3 Arc in a cubic box D.4 1584-2002 Calculation Method (2002)Evolution ofIncident Energyprescribed inAnnex D of NFPA70ESource: NFPA-70E-2018 75k plus help from the Navy

IEEE 15842018Evolution ofIncident EnergyVoltage Number of tests208V (3ph) 240V (1ph)195480V400600V3402700V3204160V18014.3kV270 3.5million donated for these testsSource: IEEE-1584-2018

IEEE 15842018HighlightsKey Changes New arcing fault (Iarc) equations New incident energy (IE) equations Electrode Configuration-Very Significant! Enclosure size factor (CF) New guidance for equipment 240VSource: IEEE-1584-2018

Arc: Plasma cloud formed in a gap between two electrodes with sufficientpotential differenceIEEE 15842018Highlights Arc flash: An electric arc event with thermal energy dissipated asDefinitions Bolted fault: A short-circuit condition that assumes zero impedanceradiant, convective, and conductive heat. Fault current: A current that flows from one conductor to ground or toanother conductor due to an abnormal connection between twoconductors.exists at the point of the fault. Arcing fault current (Arc current): A fault current flowing throughan electric arc plasma. General rule of thumb AF 50% of BF @480V Incident Energy (IE in cal/cm2): the amount of thermal energyimpress on a surface, a certain distance from the source, generated duringan electric arc event.Source: IEEE-1584-2018

Incident Energy (IE)based at defined distanceIEEE 15842018HighlightsDefinitionsDistance for 2nd degree burnBased on PNLVoltage at EquipmentGlove Class based on VoltageShock HazardVoltage Based DistancesEquipment of interest* I.E. Incident EnergyArticle 100-Definitions1.2 cal/cm2 second degree burn

Step1:Collect system and installation data Step2: Determine the system modes of operationIEEE 15842002The 9 stepprogram Step3:Determine bolted fault currents Step4: Determine arcing fault currents Step5: Find protective device characteristics and duration of arcs Step6: Document system voltages and classes of equipment Step7: Select working distances Step8:Determine Incident Energy(IE) for all equipment Step9: Determine Flash-protection boundary for all equipmentSource: IEEE-1584-2002

1. Collect system and installation data2. Determine the system modes of operation3. Determine bolted fault currentsIEEE 15842018The 10 stepprogram4. Determine typical gap and enclosure size based on systemvoltages and classes of equipment5. Determine equipment electrode configuration (HCB, VOA, etc.)6. Determine working distances7. Calculate arcing current8. Calculate arc duration (through OCPD)9. Calculate Incident energy (IE)10. Determine arc flash boundary for all equipmentNote: Black new for study engineer, Red new for softwareSource: IEEE-1584-2018

IEEE 1584-2018 HighlightsElectrode configuration

VCB Vertical Conductors in a Box (IEEE 2002)ElectrodeConfigurationNow Includes FiveVertical andHorizontalConfigurations VCBB Vertical Conductors in a Box with an insulatingBarrier HCB Horizontal Conductors in a Box VOA Vertical Conductors in Open Air (IEEE 2002) HOA Horizontal Conductors in Open AirSource: IEEE-1584-2018

ElectrodeConfigurationVCB VerticalConductors in aBox (IEEE-2002)Source: PCIC-2019 Tutorial 1&7

ElectrodeConfigurationVCBB VerticalConductors in aBox with a BarrierSource: PCIC-2019 Tutorial 1&7

For LV - IE up to 2x that of VCBKey Findings Arcing current (Iarc) reported to be higher thanVCBVCBB 208V arcs sustained down to 4kA According to testing electrode shape and gap areimportant at this levelSource: PCIC-2019 Tutorial 1&715

ElectrodeConfigurationHCB HorizontalConductors in aBoxSource: PCIC-2019 Tutorial 1&7

ElectrodeConfigurationVOA HorizontalConductors in aOpen AirSource: PCIC-2019 Tutorial 1&7

ElectrodeConfigurationHOA HorizontalConductors in aOpen AirSource: PCIC-2019 Tutorial 1&7

Arcing faultvsBolted faultLV System100ms clearingtimeThe maximum arcing fault spread is 25-40% higherSource: PCIC-2019 Tutorial 1&719

Incident EnergyvsBolted Fault480V systemClearing time100msSource: PCIC-2019 Tutorial 1&720

Incident EnergyvsBolted FaultBox vs Open AirSource: PCIC-2019 Tutorial 1&721

Arc FaultvsBolted FaultMV SystemNew Model considers the effect of arc impedance athigh fault current levelsSource: PCIC-2019 Tutorial 1&722

Incident EnergyvsBolted Fault4160-SWGRClearing time100msMore linear than LV, but bigger spreadSource: PCIC-2019 Tutorial 1&723

VCBB vs. VCBIEEE-1584-2018IEEE-1584-2002

VCB vs. VCBB vs. HCBIEEE-1584-2018IEEE-1584-2002

So, what is going on here?

Electrode configuration makes a big differencein IETakeawaysConfigurationMatters!! HCB has worst case IE VCB/VCBB-Which to Use? Depends on theOCPD characteristics If not sure on equipment, run both and take moreconservative number HOA & VCB- IE is close at LV27

Software makes study engineer chooseTakeawaysElectrodeconfigurationmakes the biggestdifference HCB – Highest Incident Energy Drawout Switchgear Busduct stabs Tranformers Termination compartmentsThe above information is a list of examples only, only the qualified Study Engineer can decide on what selections to use.

HCBExamplesElectrodeconfigurationmakes the biggestdifference600V DrawoutSwitchgear600V DrawoutSwitchgear withIron Frame600V DrawoutSwitchgear breakercompartmentThe above information is a list of examples only, only the qualified Study Engineer can decide on what selections to use.Source: PCIC-2019 Tutorial 1&7

s the biggestdifference15kV / 480V Transformercompartments480V TransformercompartmentsThe above information is a list of examples only, only the qualified Study Engineer can decide on what selections to use.Source: PCIC-2019 Tutorial 1&7

VCB vs. VCBBTakeawaysElectrodeconfigurationmakes the biggestdifferenceLow Voltage PowerDistribution PNLLow VoltageSwitchboardLow Voltage FusedDisconnectThe above information is a list of examples only, only the qualified Study Engineer can decide on what selections to use.Source: PCIC-2019 Tutorial 1&7

IEEE 1584-2018 HighlightsEnclosure Dimensions

EnclosureDimensionsCorrection Factorfor LargerEnclosures Equations normalized for a “typical” box size(20”x20”x20”) CF used when box is bigger than typical Usually found in submittals Record enclosure height and width todetermine the “equivalent” box size Between 20” and 26” Between 26” and 49” Greater than 49” use 49”Source: IEEE-1584-201833

EnclosureDimensionsShallow OptionAddedSource: IEEE-1584-2018 Box considered “shallow” when Height and width both less than 20 inches The depth is less than 8” System voltage is less than 600V34

Box alTypicalShallowTypicalTypicalTypicalTypical

Box configurationTakeawaysEnclosureconfiguration Modest difference Larger box by volume less conservative by a little Shallow box less conservative smaller IE Default enclosure size usually sufficient Software packages use defaults When on the bubble between two PPE levels goback and investigate box sizeThe above information is a list of examples only, only the qualified Study Engineer can decide on what selections to use.36

IEEE 1584-2018 HighlightsConductor Gap

Conductor Gap – Defined Gap is the distancebetween conductors Greater the gap, greaterarc flash incident energy Usually not in submittals Dangerous to obtain Is it worth measuring?

Gaps

IE vs BFLV systemVCBSource: PCIC-2019 Tutorial 1&740

Conductor Gap – TypicalSource: IEEE-1584-201841

TakeawaysFor Gap Gap Wider gap more conservative (Higher IE) Software packages use defaults Be reasonable in choosing gapThe above information is a list of examples only, only the qualified Study Engineer can decide on what selections to use.

IEEE 1584-2018Other Key Changes

125kVATransformerException2002 vs. 2018Source: IEEE-1584-2018& IEEE-1584-2002“Equipment below 240 V need not be consideredunless it involves at least one 125kVA or larger lowimpedance transformer in its immediate powersupply.”Replaced with “Sustainable arcs are possible but lesslikely in three-phase systems operating at 240Vnominal or less with an available short circuit currentbelow 2000 Amps.”

125kVATransformerExceptionWhat Does this2018 ChangeMean to You More equipment must be included in yourstudy Every device from your 125kVA transformers downto your 30kVA transformers Could dramatically impact the scope and cost ofyour facility arc flash hazard analyses Should be addressed during your next study updateor before

2-secondRuleNo Change Basically says most peoplecan move away from an arcflash in less than twoseconds, but could be sloweddown by: Obstacles or barriers Being elevated in a bucket Being restrained by othersafety equipment, etc. Your studies professionalmust “use engineeringjudgement when applyingany maximum arc durationtime for incident energyexposure calculations”Source: IEEE-1584-2018

In-Closing

New standard makes modeling more complexIEEE 1584Study Complexity Based on test data (not theoretical) More accurate Some arc flash values are higher, some lower Strongly suggest using commercial softwarefor analysis48

Stay in communication with your Qualified Arc FlashEngineer/ Client on what is going on, be reasonablein your assumptions.GeneralGuide Vendors are not opening/maintaining equipment if AFIEhigh One label per equipment, keep it simple Manufacturers – Spending on lowering AFIE intheir equipment Design Engineers – Safety by design Must decide if critical load can be de-energized, if not, howto maintain it?

130.1- Electrically Safe Work Conditions.Energized electrical conductors and circuit parts operating atvoltages equal to or greater than 50 volts shall be put into anelectrically safe work condition before an employee performswork .NFPA-70EShut downIt’s the law!!130.1(A)- Energized Work.(1) 130.1(A)(1)- Additional Hazards or Increased Risk.Energized work shall be permitted where the employer candemonstrate that de-energizing introduces additional hazards orincreased risk. (2) 130.1(A)(2)- InfeasibilityEnergized work shall be permitted where the employer candemonstrate that the task to be performed is infeasible in ade-energized state due to equipment design or operationlimitations. Source: NFPA 70E-2018Interruption of life supportDeactivation of emergency alarm systemsShutdown of hazardous location ventilation equipmentDiagnostics and testingIntegral part of a continuous process

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21.10.2019 · IEEE 1584- 2018 Highlights. Definitions. Distance for 2nddegree burn Incident Energy (IE) based at defined distance Voltage at Equipment Glove Class based on Voltage Shock Hazard Voltage Based Distances Equipment of interest Based on PNL * I.E. Incident Energy. Article 100-Definitions.