Comparing Methods of Calculation - atc-trng.comatc-trng.com/wp-content/uploads/2010/10/Arc-Flash-Calculation... · Calculation And found some existing needs. 12 November 17, 2004

1November 17, 2004Revised 02.08.05

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Electrical Flash Hazard Analysis

Comparing Methods of Calculation

Developed byDeveloped byNeil Van Geem, PE & W P Blackley, PE Neil Van Geem, PE & W P Blackley, PE

ATC Consulting Services ATC Consulting Services for the for the

IEEE IEEE -- IAS Workshop Denver, Colorado 2005IAS Workshop Denver, Colorado 2005



Electrical Flash Hazard AnalysisComparing Methods of

Calculation



Why we compared Five Different Methods

Our Challenge

Determine Proper PPE Levels for Utility Workers



The Challenge for Substation & Plant Workers

And How Many Work Positions

• Substation Types– Open Air– Metal Clad Gear– Inside

Buildings

• Fault Conditions– 10 to 40 kA– 240V to 500kV– ½ to 8 cycles



The Challenge for Overhead Workers

And How Many Work PositionsAerial Lifts & Structure Work

• Line Types– Transmission

• Steel Structures• Wood Structures

– Distribution• Crossarm Construction• Armless construction




The Challenge for Overhead Workers



The Challenge for Underground Workers

And How Many Work PositionsLooking Down, In & Up

• Line Types– Direct Buried– Trenches– Duct Banks– Manholes




The Challenge for Manhole Workers

And How Many Work Positions

• Fault Types– In front of me – Behind me– On my side

• Fault Conditions– 10 to 200 kA– 208V to 345kV– ½ to ??? cycles



Not to Mention Metering & Padmount Transformers

All Looking Directly at the ARC

• Boxes • Self Contained

480v meters

• Fault Conditions– 10 to 60 kA– 120/240 thru 25kV– Up to 10 cycles



And Then We Found Ourselves Comparing

Five Different Methods of Calculation

And found some existing needs



Five Different Methods

• Lee’s Method• Duke Power• NFPA 70E• Arcpro• IEEE 1584

How do I choose ?



Comparison of Published Ranges of Input Variables

YYNo Limit0.5 - 630.7 - 1060.208 - 15IEEE 1584

YNo Limit1 - 12 1 *3.5 - 21.5To sustain arcCommercial

YYNo Limit1.25316 - 500.6 and Less NFPA 70E

YNo LimitGreater than 1

**1 *Not

PublishedNot

PublishedDuke Heat

Flux

YNo Limit**1UnlimitedUnlimitedLee Method

Fault in

Box

Fault in Air

Clearing Time

Cycles

Arc Gap

Inches

1 or 3 ØIbf KAVoltage

KV Method

* - Published factors adjust results to three phase in air or box ** - Values not published



PPE Levels of Protection –NFPA 70E 2004

• 0 cal/cm2 < Level 0 < 1.2• 1.2 cal/cm2 < Level 1 < 4.0• 4.0 cal/cm2 < Level 2 < 8.0• 8.0 cal/cm2 < Level 3 < 25.0• 25.0 cal/cm2 < Level 4 < 40.0• 40.0 cal/cm2 – Don’t go there!

Too Little PPE – Bad Burn

Too Much – PPE Unnecessary Fatigue

& Stress



What & Why – Selected Currents

Fault Currents used 16kA < If < 60 kA

500 kVA Transformer Secondary Voltage 480Y/277% Impedance 3.75If = 16,038 Amperes

Lower Limits for If:NFPA 70E (2000) = 16,000 AmperesNFPA 70E (2004) = 700 AmperesIEEE 1584 = 700 Amperes

See Notes for IEEE 1584 Limitations

HmmmmmmHmmmmmm the NFPA the NFPA equation parameters equation parameters

changed but the changed but the formula did not?formula did not?



What & Why – Selected CurrentsWe chose Fault Currents of

16kA < If < 60 kA

2500 kVA Transformer Secondary Voltage 480Y/277% Impedance 5.0If = 60,142 Amperes

Upper Limit for If:NFPA 70E (2000) = 50,000 AmperesNFPA 70E (2004) = 106,000 AmperesIEEE 1584 = 106,000 Amperes


Wonder how the Wonder how the NFPA limits changed NFPA limits changed and the equation did and the equation did

not?not?



What & Why – Selected Voltages

• Voltages Used– Low Voltages

• 480Y/277• 600• 1000

– Medium Voltages• 4.16Y/2.4 kV• 12.47Y/7.2 kV• 13.8Y/7.96 kV• 34.5Y/19.9 kV• 46.0Y/26.6 kV


Selected Voltages are Selected Voltages are frequently worked with frequently worked with

rubber PPErubber PPE



Variable Fault Current for 480 volts in Air, 18" Work Distance1.25" Arc Gap, 2.4 Cycle Clearing Time

0.0

2.0

4.0

6.0

8.0

10.0

12.0

16 20 30 40 50 60Current in kA

IEEE 1584 3 Phase

NFPA 70E 3 Phase

Commercial 1 Phase

Commercial 3 Phase X 1.2

Commercial 3 Phase X 2.2

Lee's Method 3 Phase

Duke Heat Flux Normal 1Phase Duke Heat Flux Normal 3Phase X 2.8

Incident Energy Vs. If in Air

Level 0

Level 1

Level 2

Level 3



V a ria b le F a u lt C u rre n t fo r 4 8 0 v o lts in B o x , 1 8 " W o rk D is ta n c e , 1 .2 5 " A rc G a p , 2 .4 C y c le C le a rin g T im e

0

4

8

12

16

20

24

28

32

16 20 30 40 50 60

C u rre n t in kA

Cal

/Cm

2

IE E E 1584 3 P has e inB ox NF P A 70E 3 P has e inB oxC om m erc ia l 1 P has e inAirC om m erc ia l 3 P has eB ox Min X 3 .7C om m erc ia l 3 P has eB ox Max X 6.5Lee 's Method Norm al 3P has e in AirD uke Heat F lux Norm al1 P has e in AirD uke Heat F lux 3P has e in B ox X 5 .0

Incident Energy Vs. If in Box

Level 0

Level 1

Level 2

Level 3

Level 4



V a ria b le C le a rin g T im e s fo r 4 8 0 V o lts in A ir, 1 8 " W o rk D is ta n c e , 1 .2 5 " A rc G a p , C u rre n t 5 0 k A

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

2.4 6.0 10.0 15.0 20.0 30.0

C le ar in g T ime C ycle s

Cal

/Cm

2

! E E E 1584

NF P A 70E

C om m erc ia l Norm al

C om m erc ia l 3 P has eAir Min. X 1 .2C om m erc ia l 3 P has eAir Max X 2 .2Lee 's Method Norm al 3P has eD uke Heat F lux Norm al

D uke Heat F lux 3P has e in Air X 2 .8

Incident Energy Vs. Clearing Time In Air @ 50kA

Level 0Level 1

Level 2

Level 3

Level 4



V ar iab le C lear in g T im es fo r 480 V o lts in B o x , 18" W o rk D is tan ce , 1 .25" Arc G ap , C u rren t 50 kA

0

50

100

150

200

250

300

2.4 6 10 15 20 30

C lear ing T im e in C ycles

Cal

/Cm

2

!E E E 1584

NFP A 70E

C ommerc ia l Normal

C ommerc ia l 3 P hase B oxMin. X 3.7C ommerc ia l 3 P hase B oxMax X 6.5Lee 's Method Normal 3P haseD uke Heat F lux Normal

D uke Heat F lux 3 P hasein B ox X 5.0

Incident Energy Vs. Clearing TimeIn Box @ 50kA

Level 4



V ar iab le C lear in g T im es 480 V o lts in Air , 18" W o rk D is tan ce , 1 .25" Arc G ap , C u rren t 16 kA

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

2.4 6.0 10.0 15.0 20.0 30.0

C lear ing T im e C ycles

Cal

/Cm

2

!E E E 1584

NFP A 70E


C ommerc ia l 3 P hase A ir M in.X 1.2C ommerc ia l 3 P hase A ir MaxX 2.2Lee's Method Normal 3 P hase

D uke Heat F lux Normal

D uke Heat F lux 3 P hase in A irX 2.8

Incident Energy Vs. Clearing Time In Air @ 16kA

Level 0

Level 1

Level 2

Level 3



V ariab le C lea r ing T im es 480 V o lt Arc in a B o x - 18" W o rk in g D is tan ce - 1 .25" Arc G ap

0 .02 .04 .06 .08 .0

1 0 .01 2 .01 4 .01 6 .01 8 .02 0 .02 2 .02 4 .02 6 .02 8 .03 0 .03 2 .03 4 .03 6 .03 8 .04 0 .0

2 .4 6 .0 1 0 .0 1 5 .0 2 0 .0 3 0 .0C le a r in g T im e in C y c le s

Cal

/Cm

2

!E E E 1 5 8 4

NF P A 7 0 E

C o m m e rc ia l No rm al

C o m m e rc ia l 3 P has eB o x M in. X 3 .7C o m m e rc ia l 3 P has eB o x M ax X 6 .5L e e 's M e tho d No rm al 3P has eD uke He at F lux No rm al

D uke He at F lux 3P has e in B o x X 5 .0

Incident Energy Vs. Clearing TimeIn Box @ 16kA

Level 0Level 1

Level 2

Level 3

Level 4



Variable Working Distance 480 Volts in Air, Clearing Time, 6 Cycle, Arc Gap, 1.25", Current 50 kA

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

18 24 30 36 42 48Working Distance - Inches

Cal

/Cm

2

!EEE 1584

NFPA 70E

Commercial Normal

Commercial 3 Phase AirMin. X 1.2Commercial 3 Phase AirMax X 2.2Lee's Method Normal 3PhaseDuke Heat Flux Normal

Duke Heat Flux 3 Phase inAir X 2.8

Incident Energy Vs. Work DistanceIn Air @ 50kA

Level 0

Level 1

Level 2

Level 3



V ar iab le W o rk in g D is tan ce fo r 480 vo lts in B o x , 6 C yc le C lear in g T im e , 1 .25" a rc g ap , C u rren t 50 kA

0 .04 .08 .0

1 2 .01 6 .02 0 .02 4 .02 8 .03 2 .03 6 .04 0 .04 4 .04 8 .05 2 .05 6 .06 0 .0

1 8 2 4 30 36 42 4 8

W o rk in g D is ta n c e - In ch e s

Cal

/Cm

2

!E E E 1 5 8 4

NF P A 7 0 E

C o m m e rc ia l No rm al

C o m m e rc ia l 3 P has e B o xM in. X 3 .7C o m m e rc ia l 3 P has e B o xM ax X 6 .5L e e 's M e tho d No rm al 3P has eD uke He at F lux No rm al

D uke He at F lux 3 P has ein B o x X 5 .0

Incident Energy Vs. Work DistanceIn Box @ 50kA

Level 0

Level 1Level 2

Level 3

Level 4



Variable Working Distance for 480 Volt Arc in Air, 6 Cycle Clearing Time, 1.25" Arc Gap, If 16,000 Amperes

0

0.5

1

1.52

2.5

3

3.5

4

18 24 30 36 42 48

Working Distance in Inches

Cal

/Cm

2

!EEE 1584

NFPA 70E

Commercial Normal

Commercial 3 PhaseAir Min. X 1.2Commercial 3 PhaseAir Max X 2.2Lee's Method Normal 3PhaseDuke Heat Flux Normal

Duke Heat Flux 3Phase in Air X 2.8

Incident Energy Vs. Work DistanceIn Air @ 16kA

Level 0

Level 1



V ariab le W o rk in g D is tan ce fo r 480 vo lt A rc in B o x , 6 C ycle C learin g T im e, 1 .25" A rc G ap , IF 16 ,000 A m p eres

012345678

18 24 30 36 42 48W o rk in g D is tan ce in In ch es

Cal

/Cm

2

!E E E 1584

NFP A 70E


C ommerc ia l 3 P hase B ox M in.X 3.7C ommerc ia l 3 P hase B ox MaxX 6.5Lee 's Method Normal 3 P hase

D uke Heat F lux Normal

D uke Heat F lux 3 P hase in B oxX 5.0

Incident Energy Vs. Work DistanceIn Box @ 16kA

Level 0

Level 1

Level 2



V a r ia b le V o lta g e 5 0 k A Ar c , 1 8 " W o r k D is ta n c e , A rc G a p V a r ie d w ith V o lta g e a s p e r IE E E 1 5 8 4

05 0

1 0 01 5 02 0 02 5 03 0 03 5 04 0 04 5 0

0 .4 8 0 .6 1 2 .4 4 .1 6 1 2 .4 7 1 3 .8 2 4 .9 4 3 4 .5

V o lta g e in k V

Cal

/Cm

2

!E E E 1584 3 P hase inA irNFP A 70E 3 P hase inA irC ommerc ia l Normal 1P hase in A irC ommerc ia l 3 P hase A irM in. X 1.2C ommerc ia l 3 P hase A irMax X 2.2Lee's Method Normal 3P hase A irD uke Heat F lux Normal1 P hase in A irD uke Heat F lux 3 P hasein A ir X 2.8

Incident Energy Vs. VoltageIn Air @ 50kA with Lee’s Method

Level 4



Incident Energy Vs. VoltageIn Air @ 50kA w/o Lee’s Method

Level 0Level 1

Level 2

Level 3

Level 4

Variable Voltage 50 kA Arc, 18" Work Distance, Arc Gap Varied with Voltage as per IEEE 1584

0

5

10

15

20

25

30

35

40

0.48 0.60 1.00 2.40 4.16 12.47 13.80 24.94 34.50

Voltage

Cal

/Cm

2

!EEE 1584 3 Phasein Air

NFPA 70E 3 Phasein Air

CommercialNormal 1 Phase inAirCommercial 3Phase Air Min. X 1.2

Commercial 3Phase Air Max X 2.2

Duke Heat FluxNormal 1 Phase inAirDuke Heat Flux 3Phase in Air X 2.8



V a r ia b le V o lta g e 1 6 k A Ar c in A ir , 1 8 " W o r k D is ta n c e , A rc G a p V a r ie d w ith V o lta g e a s p e r IE E E 1 5 8 4

02 04 06 08 0

1 0 01 2 01 4 01 6 0

0 .4 8 0 .6 0 1 .0 0 2 .4 0 4 .1 6 1 2 .4 7 1 3 .8 0 2 4 .9 4 3 4 .5 0

V o lta g e in k V

Cal

/Cm

2

!E E E 1584 3 P hase in A ir

NFP A 70E 3 P hase in A ir

C ommerc ia l Normal 1P hase in A irC ommerc ia l 3 P hase A irM in. X 1.2C ommerc ia l 3 P hase A irMax X 2.2Lee's Method Normal 3P hase A irD uke Heat F lux Normal 1P hase in A irD uke Heat F lux 3 P hasein A ir X 2.8

Incident Energy Vs. VoltageIn Air @ 16kA with Lee’s Method

Level 3Level 4



V a r ia b le V o lta g e 1 6 k A A rc in A ir , 1 8 " W o rk D is ta n c e , A rc G a p V a r ie d w ith V o lta g e a s p e r

IE E E 1 5 8 4

0

2

4

6

8

1 0

1 2

0 .4 8 0 .6 0 1 .0 0 2 .4 0 4 .1 6 1 2 .4 7 1 3 .8 0 2 4 .9 4 3 4 .5 0V o ltag e

Cal

/Cm

2

! E E E 1584 3 P has e inAirNF P A 70E 3 P has e inAirC om m erc ia l Norm al 1P has e in AirC om m erc ia l 3 P has eAir Min. X 1 .2C om m erc ia l 3 P has eAir Max X 2.2D uke Heat F lux Norm al1 P has e in AirD uke Heat F lux 3P has e in Air X 2 .8

Incident Energy Vs. VoltageIn Air @ 16kA w/o Lee

Level 0

Level 1

Level 2

Level 3



V ar iab le Medium V oltage, S ing le P hase, 10 K A Arc in Air , 18" R ubber G love W ork D istance, Arc G ap 6" , 10 C ycle C lear ing T im e

0 .0

0 .5

1 .0

1 .5

2 .0

2 .5

3 .0

3 .5

4 .0

2 .4 0 4 .1 6 1 2 .4 7 1 3 .8 0 2 4 .9 4 3 4 .5 0 4 6 .0 0

S o u r c e Vo lta g e in k V

Cal

/Cm

2 C om m erc ia l N orm a l 1P has e in A irD uk e H eat F lux N orm al1 P has e in A ir

Incident Energy Vs. Medium VoltageIn Air @ 10kA 18” Work Distance

Level 1

Level 0



V a r ia b le M e d iu m V o lta g e , S in g le P h a s e , 1 0 k A Arc in A ir , 6 0 " Ho t S tic k W o r k D is ta n c e , A r c G a p 6 " , 1 0 C y c le C le a r in g T im e

0 .0 0

0 .0 5

0 .1 0

0 .1 5

0 .2 0

0 .2 5

0 .3 0

0 .3 5

2 .4 0 4 .1 6 1 2 .4 7 1 3 .8 0 2 4 .9 4 3 4 .5 0 4 6 .0 0

S o u rce V o ltag e in kV

Cal

/Cm

2 C om m erc ia l No rm a l 1P hase in A ir

D uke Hea t F lux No rm a l1 P hase in A ir


Level 0



V ar iab le M ed iu m V o ltag e , S in g le P h ase , 25 kA Arc in Air , 18" R u b b er G lo ve W o rk D is tan ce , Arc G ap 6", 10 C yc le C lear in g T im e

0.0

2.0

4.0

6.0

8.0

10.0

12.0

2.40 4.16 12.47 13.80 24.94 34.50 46.00

S ource V o ltage kV

Cal

/Cm

2

C ommerc ia l Normal1 P hase in A ir

D uke Heat F luxNormal 1 P hase in


Level 0

Level 1

Level 2

Level 3



V a ria b le M e d iu m V o lta g e , S in g le P h a s e , 2 5 K A A rc in A ir, 6 0 " H o t S tic k W o rk D is ta n c e , A rc G a p 6 " , 1 0 C y c le C le a rin g T im e

0.0

0.2

0 .4

0 .6

0 .8

1 .0

1 .2

2 .40 4.16 12.47 13.80 24.94 34.50 46.00

S o u rce V o lta g e in kV

Cal/C

m2

C om m erc ia l N orm al 1 P has ein A irD uk e H eat F lux N orm al 1P has e in A ir


Level 0



Flash ProtectionLet me see I determine

the hazard then select the PPE



Flash Protection Summary

Additional research is needed for higher voltages

and electrode materials

• No Method covers all situations• Each has different input

parameters• Each has limitations• Each may require different PPE

Levels• IEEE 1584 may be the median• Commercial method may be better

at medium voltages• Different types of electrodes are

not considered



Additional NeedsEffects on Work Positions

Looking down into equipmentWorking in manholesWorking in vaultsWorking under bus and conductors



Additional Needs

Medium Voltage ApplicationsOpen AirMetal Switch GearSubstations Overhead Open Air LinesCables Manholes & Vaults



Additional Issues

•Blast Effects•Concussion•Flying Debris•Hearing



Flash ProtectionThese tables and information are designed to provide comparativeThese tables and information are designed to provide comparativeinformation concerning the arc/flash hazard.information concerning the arc/flash hazard.

They do not address the hazards associated with any other arc byThey do not address the hazards associated with any other arc by products. products. They also assume the worker is exposed horizontal to the arc locThey also assume the worker is exposed horizontal to the arc location. ation. Workers who are positioned in such a manner as to allow the arc Workers who are positioned in such a manner as to allow the arc to rise to rise towards them will experience a more severe condition. towards them will experience a more severe condition. This information is limited to specific cases as described in thThis information is limited to specific cases as described in the charts. e charts. It can serve to give all workers a better understanding of the iIt can serve to give all workers a better understanding of the intensity of ntensity of electrical arcs and give safety personnel a comparison of the reelectrical arcs and give safety personnel a comparison of the results of the sults of the available calculation methods.available calculation methods.

These values were determined using the input conditions shown with the charts and:1. No automatic reclosure or restrike of arc for medium voltage cases. (Reclosers turned off)2. PPE protection levels are based on data from Table 130.7(C)(11), page 34 NFPA 70E 20043. Comparisons were made using the same input parameters for the calculation methods selected

no other verification was attempted.

REMEMBER NO AMOUNT OF PROTECTION WILL REPLACE AN ALERT WORKERREMEMBER NO AMOUNT OF PROTECTION WILL REPLACE AN ALERT WORKER



To All Those Who Have Gone Before


We appreciate all the work all of you have

done to get us to this level!

We know contributions you & others have made this a safer world for electrical workers

We say THANKS and hope this presentation will help the industry continue to improve

Comparing Methods of Calculation - atc-trng.comatc-trng.com/wp-content/uploads/2010/10/Arc-Flash-Calculation... · Calculation And found some existing needs. 12 November 17, 2004

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