Incident energy factorsand simple 480-V incident energy equations

BY TAMMY L. GAMMON & JOHN H. MATTHEWS

HE RELEASE OF IEEE 1584-2002, GUIDE FOR PERFORMING ARC-

Flash Hazard Calculations, is formal recognition of the danger of arcing

faults in electrical systems. The standard includes an extensive data set

used for developing the IEEE 15842002 arc-flash calculator that pre-

dicts three-phase arc current and incident energy for appropriate selection of overcurrent

protective devices and personal protective equipment (PPE), respectively. As an addition-

al benefit, the published data set can further enhance the understanding of the electrical

characteristics of arcing faults in industrial power systems. The 1584 data set has been

both quantitatively and qualitatively analyzed to assess the relationships between arc cur-

rent, arc voltage, system voltage, arc power, and incident energy, as well as other vari-

ables, such as gap widths and the effect of equipment enclosures. Simple relationships for

estimating three-phase arc current, arc power, and incident energy on low-voltage (

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The Arc as a Circuit Parameter Although a complex model depending on fundamentalphysical quantities, like plasma enthalpy, may be moreprecise when used correctly, it is often easier for elec-

trical engineers to understand the arcing fault modeledas a simple electrical circuit parameter. Furthermore,since arcing is such a dynamic and random process,arcs initiated on identical test setups are not likely toproduce identical sets of data, although the extent ofvariability depends on the setup involved.

A single-phase equivalent circuit containing an arcis shown in Figure 1 and defined as follows:

Vmax sin(t) = Riarc + L diarcdt

+ varc. (1)

For simplicity, the three-phase arc currents areassumed to be in balance and the effective groundimpedance is zero (which occurs when the three bal-anced fault currents sum to zero as they return toground through the same path). For a given supplyvoltage and system impedance, the arc current is limit-ed by the arc voltage. The precise arc voltage is anundefined, nonlinear function; the arc voltage wave-form is neither sinusoidal nor dc.

Figures 25 show the impact of several parameterson the arc voltage. For a given supply voltage and sys-tem impedance, as the magnitude of the arc voltageincreases, the arc current and the ratio of the arc currentto the short-circuit current (short-circuit ratio)decrease. Figure 2 presents the results of 13.8-kV,three-phase arc testing in open air with gap widths of13 mm (five tests) and 152 mm (16 tests) between thethree-phase conductors acting as electrodes. The twoopen-air, ungrounded, test setups had available short-circuit circuits of 20.1 kA. Figure 2 clearly shows thatlarger gap widths generate larger arc voltages, eventhough the increase is not proportional. The larger gapis 11.7 times the smaller gap, and the correspondingaverage arc voltage is only 2.8 times larger. The mea-sured rms arc voltages for each gap width demonstratethe variability in the data from identical arc test setups.

In Figure 3, the same data from the 13.8-kV testsetup with a 13 mm gap width is plotted with datafrom a 610-V test setup to show that larger supplyvoltages also tend to generate larger arc voltages. The610-V data (six tests) was collected from three-phasearc testing in open air; the ungrounded, test setup hadan available short-circuit current of 36.25 kA. Eventhough the 610-V test setup had slightly larger gapwidths and generated larger fault currents (24.225.5kA as opposed to 20.020.3 kA), the arc voltagesassociated with the lower voltage supply were signifi-cantly smaller. As in Figure 2, the change in arc volt-age was proportionally much smaller than the changein the supply voltage. The ratio of the supply voltagesis 22.6 and the ratio of the respective arc voltages isonly 2.2. Higher electric fields associated with thelarger supply voltages may be responsible for produc-ing larger arc voltages.

Figure 4 shows an interesting relationship betweenthe location of the electrodes and the arc voltage.When an arc is initiated in a box, a lower arc voltage is

Arc voltage as a function of supply voltage.

0.750

0.500

0.250

0.000

Arc

Volta

ge (k

V-Lin

e)

0 10 20 30Gap Width (mm)

13.8 kV, 587 V (Average) 610 V, 264 V (Average)

3

Arc voltage as a function of gap width.

2.0

1.5

1.0

0.5

0.0Arc

Volta

ge (k

V-Lin

e)

0 50 100 150 200Gap Width (mm)

13 mm, 587 V (Average)152 mm, 1.628 kV (Average)

2

Equivalent circuit of an arcing fault.

iarc

varc

Zsystem =R + jL

Vsupply =Vmaxsin(t)

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generated. The lower arc voltage may result from theenclosures affect of limiting the arc length. Both theopen (nine tests) and box (12 tests) tests were per-formed with three-phase voltage supplies ranging from600 V to 623 V and both test setups were ungroundedwith 32-mm (1 14 in) gaps between the conductors. The12 box tests were conducted inside a 508 mm 508mm 508 mm (508 mm = 20 in) metal box open inthe front. The three phase conductors were 102 mm (4in) from the rear wall.

Although not identified in IEEE 15842002 Stan-dard, Stokes [7], [8] has established that the rms arcvoltage is related to the rms arc current raised to apower of 0.12; Figure 5 shows this relationship. Whenthe rms arc current ( Iarc ) equals 500 A, I 0.12arc equals2.11; when Iarc increases to 50,000 A the value of I 0.12archas only increased to 3.66. Although the arc voltage isnot explicitly plotted in Figure 5, it is clear that as thearc current increases, the arc voltage will also increaseslightly.

Figures 25 demonstrate that the gap width, thesupply voltage, enclosure type, and the arc currentaffect the magnitude of the arc voltage. Although thearc voltage may seem like an unimportant quantity, itis very important when analyzing the arc as an electri-cal model, because the magnitude of the arc voltagedetermines how much current can flow. Even if the arcvoltage is not explicitly declared in arc power andenergy equations, the impact of arc voltage is certainlyembedded in them. Fundamentally, the single-phase,time-average arc power (Parc ) and arc energy (Earc ) maybe defined by the instantaneous arc phase current andarc phase voltage:

Parc =

varc iarc/(number of samples) (2)Earc =

varc iarc t. (3)

The three-phase Parc or Earc may be determined byadding the Parc or Earc , respectively, of the three phases.

Additional factors may also affect the arc voltageand current. These factors include the gap widthbetween the phase conductors (electrodes) and therear wall of the box and the type of grounding. The1584 analysis group found no correlation betweenX/R ratio of the system impedance and arc current,which means that the high-energy, three-phase arcsgenerated continuous arc currents. The recent phase-to-ground, current-dependent arc voltage modelsshowed that the X/R ratio of the system impedanceaffected the short-circuit ratio [9]. These waveformswere discontinuous, and the X/R ratio affected theshape of the waveform and the extinction time; conse-quently, the X/R ratio also affected the magnitude ofthe arc current and the short-circuit ratio. Discontin-uous arc waveforms are likely to extinguish, unlesssome mechanism initiates restrike when the arcbecomes extinct. In the case of three-phase arcs, a

higher ionization level at current zero may facilitatearc restrike at a lower restrike voltage than used inthe published current-dependent arc models.

Analysis of 1584 Test Data The data listed in Table 1 shows that the short-circuitratio generally increases as the supply voltage increases.Although the arc voltage also increases with increasingsupply voltage, the arc voltage increases at a slower ratethan the supply voltage; hence, the ratio of arc voltage tosupply voltage decreases. By applying Kirchoffs voltagelaw and Ohms law to Figure 1 to two different circuitsdefined by smaller and larger supply voltages with thesame short-circuit current, the short-circuit ratio gener-ally increases with a decreasing ratio of arc voltage tosupply voltage. The 208250 V tests in the data set maybe the exception because of the relatively close proximitybetween 208250 V and 400485 V, and because thelower-magnitude short-circuit currents available on the208250 V setups tend to result in higher short-circuitratios (based on current-dependent model analysis [10]).

Impact of arc current on arc voltage.

4

3

2

1

0

i arc

0.

12

0 10,000 20,000 30,000 40,000 50,000Arc Current, iarc (A)

5

Arc voltage as a function of enclosure.

0.500

0.375

0.250

0.125

0.000

Arc

Volta

ge (k

V-Lin

e)

0 10 20 30Arc Current (kA)

Open Box4

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TABLE 1. STATISTICAL SUMMARY OF IEEE 1584 DATA SET.

Voc Electrode EnclosedEnclosed Supply Isc Iarc / Varc Varc / Parc/ Rarc / Gap Box = 1

kV kA Isc kV-line Voc VAsc Zsystem mm Open = 01 kV Three-Phase Supply (148 tests)min 2.328 2.527 0.591 0.501 0.036 0.027 0.036 13.00 0.00max 13.800 40.800 1.161 1.886 0.387 0.326 0.395 152.00 1.00mean 5.490 14.426 0.954 0.946 0.221 0.214 0.231 109.13 0.53median 2.382 15.000 0.971 0.662 0.253 0.228 0.266 102.00 1.00stdev 4.698 8.815 0.072 0.483 0.084 0.078 0.091 26.99 0.50

208250 V Three-Phase Supply (six tests)min 0.208 20.000 0.238 0.187 0.811 0.141 1.195 10.00 1.00max 0.250 87.500 0.678 0.220 0.899 0.444 3.772 12.70 1.00mean 0.243 31.250 0.565 0.208 0.855 0.250 1.755 10.45 1.00median 0.250 20.000 0.616 0.209 0.863 0.171 1.401 10.00 1.00stdev 0.017 27.557 0.164 0.012 0.035 0.144 0.996 1.10 0.00

400485 V Three-Phase Supply (41 tests)min 0.400 2.551 0.239 0.175 0.433 0.119 0.520 7.11 0.00max 0.485 103.340 0.832 0.383 0.945 0.369 3.291 38.10 1.00mean 0.411 55.857 0.477 0.283 0.691 0.303 1.601 21.30 0.93median 0.400 53.607 0.472 0.285 0.704 0.321 1.510 19.05 1.00stdev 0.025 31.628 0.132 0.047 0.121 0.048 0.628 8.96 0.26

590687 V Three-Phase Supply (116 tests)min 0.590 0.671 0.324 0.213 0.349 0.222 0.418 7.11 0.00max 0.687 106.000 0.956 0.615 1.042 0.484 1.843 76.20 1.00mean 0.601 22.761 0.768 0.317 0.526 0.348 0.711 27.72 0.83median 0.600 21.400 0.778 0.317 0.524 0.340 0.652 32.00 1.00stdev 0.015 21.447 0.125 0.070 0.113 0.059 0.248 12.92 0.38

2.3282.382 kV Three-Phase Supply (78 tests)min 2.328 2.527 0.591 0.511 0.216 0.199 0.215 102.00 1.00max 2.382 16.403 1.055 0.792 0.336 0.297 0.360 102.00 1.00mean 2.357 10.996 0.931 0.635 0.269 0.236 0.285 102.00 1.00median 2.360 13.000 0.947 0.610 0.261 0.227 0.284 102.00 1.00stdev 0.017 4.863 0.086 0.067 0.028 0.025 0.031 0.00 0.00

4.16 kV Three-Phase Supply (35 tests)min 4.160 5.440 0.742 1.487 0.358 0.244 0.366 102.00 0.00max 4.160 40.433 1.161 1.612 0.387 0.326 0.395 102.00 0.00mean 4.160 16.649 0.966 1.557 0.374 0.289 0.383 102.00 0.00median 4.160 19.833 0.971 1.572 0.378 0.286 0.386 102.00 0.00stdev 0.000 10.709 0.055 0.064 0.015 0.022 0.015 0.00 0.00

13.8 kV Three-Phase Supply (35 tests)min 13.800 5.710 0.977 0.501 0.036 0.027 0.036 13.00 0.00max 13.800 40.800 1.008 1.886 0.137 0.122 0.138 152.00 0.00mean 13.800 19.847 0.994 1.514 0.110 0.090 0.110 132.14 0.00median 13.800 20.100 0.995 1.659 0.120 0.094 0.121 152.00 0.00stdev 0.000 10.266 0.007 0.401 0.029 0.026 0.029 49.35 0.00

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For the voltage supplies greater than 1 kV, the aver-age short-circuit ratio is 0.954 with an average testedgap width of 109 mm (4.29 in.). Therefore, for the rel-atively small gap widths likely in industrial buildings,the arc voltage is likely to be a fairly small percentageof a medium-voltage supply (0.221, average), and themagnitude of the arc current is likely to approach theshort-circuit current.

For voltage supplies less than 1 kV, the arc current(and short-circuit ratio) is highly dependent on thesupply voltage because the arc voltage is a significantfraction of the source, averaging 0.855, 0.691, and0.526 for the 208250 V, 400485 V, and 590687 Vsupplies, respectively. The respective average short-cir-cuit ratios are 0.565, 0.477, and 0.768. The relativelysmall changes in gap width more significantly impactthe magnitudes of the arc voltage and current generat-ed by low-voltage supplies in comparison with medi-um-voltage supplies.

The large set of data has provided validation forapplying the maximum power transfer theory to arcing-fault circuits. If the arc is assumed to be a passive linearresistance, the maximum power, 50% of the short-cir-cuit VA, is transferred to the arc when the arc resistanceequals a purely inductive system impedance [11]. Themaximum ratio of Parc to short-circuit VA (VAsc), listedin Table 1, is 0.484. Furthermore, Figure 6 shows thetheoretical curve of Parc/VAsc as a function of the ratioof arc resistance to a purely inductive system imped-ance. The data points plotted on the same graph con-firm that the theoretical maximum power curve is notexceeded; moreover, the data points follow the samegeneral trend of decreasing Parc /VAsc as the arc resis-tance increases with respect to the system impedance.For the 400485 V and 590687 V tests, the averageParc ratios are 0.303 and 0.348. These values are fairlyclose to the ratios predicted for more inductive systemsby the 480-V current-dependent arc model in [10].

IEEE 1584ARC Current and Incident Energy Accurately predicting arc current is important inselecting and coordinating overcurrent protectivedevices; accurately predicting incident Earc is impor-tant in assessing an arc-flash hazard endangering a per-son. Incident energy is defined as the amount of energy(J/cm2 or cal/cm2) impressed on a surface at a certain

TABLE 3. PPE CATEGORIES [12].

Risk Minimum PPE RatingCategory (cal/cm2) Clothing Required

0 Na 4.514 ounce/yard untreated cotton

1 4 Flame resistant (FR) shirt and pants

2 8 Cotton underclothing plus FR shirt and pants

3 25 Cotton underclothing plus FR shirt and pants, plus FR coverall

4 40 Cotton underclothing plus FR shirt and pants, plus multilayerflash suit

TABLE 2. VARIABLE DEFINITIONS FOR (5), (6), AND (7).

K 0.153, open, or 0.097, box configurationsV Three-phase supply voltage in kV

g Distance between phase conductors in mm

IEn Normalized incident energy for an arc duration of 200 ms and for a distance from the arc of 610 mm (24 in.)

Cf Calculation factor; 1.5 on LV and 1.0 on MV systems

t Time duration in seconds

D Distance from arc electrodes (phase conductors)

x Distance factor. 2.000, LV & MV open air and cable; 0.973, MV switchgear; 1.473, LV

switchgear; 1.641 LV motor control centers and panels

K1 0.792, open, or 0.555, closed configurationK2 0, ungrounded or high-resistance grounded

system; 0.113, grounded system

Parc/VAscas a function of Rarc/Zsystem.

0.5

0.4

0.3

0.2

0.1

0.0

Arc

Pow

er

/ Sho

rt-Ci

rcui

t VA

0 1 2 3 4Arc Resistance / System Impedance

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distance from the source; the arc-flash hazard increasesat closer proximities to the source.

In IEEE 15842002, the following equation is usedto calculate the three-phase arc current on low-voltage(LV, less than 1 kV) systems:

log( Iarc) = K + 0.662 log( Isc) + 0.0966 V+ 0.000526 g + 0.5588 V log( Isc) 0.00304 g log( Isc). (4)

For medium-voltage (MV, 115 kV) systems, the fol-lowing equation is used:

log( Iarc) = 0.00402 + 0.983 log( Isc). (5)

The arc power and total arc energy, intermediate stepsin finding the incident energy, are not explicitly for-mulated in 1584. For LV and MV systems, the inci-dent energy (IE) may be found from the followingIEEE 1584 equations:

IE =IEn Cf (t/0.2) (610x/Dx) (6)log(IEn) = K1 + K2 + 1.081 log( Iarc)

+ 0.00110 g. (7)

[See Table 2 for variable definitions for (5)(7).] Theunits of incident energy matchthose of the normalized incidentenergy (J/cm2 or cal/cm2), andcalories (cal) can be converted toJoules (J) by multiplying by4.184. To ease the process of ashort-circuit study and an arc-flash hazard assessment, IEEE15842002 Standard has includ-ed bolted-fault and arc-flash cal-culators. The arc-flash calculatorcomputes the incident energy(which determines PPE class) aswell as a safe flash-protectionboundary (where no PPE isrequired). The personal protec-tive equipment risk categories aredefined in Table 3.

Table 4 lists the average devia-tions of the calculated arc currentand incident energy with themeasured arc current and maxi-mum incident energy (of theseven calorimeters placed a dis-tance D in front of the elec-trodes). The percent deviation iscalculated as:

TABLE 4. AVERAGE % DEVIATIONS OF Iarc AND IE.

Open Open Closed Both>1 kV

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% deviation = 100 |meas.calc.|/meas. (8)

The formulas adopted in IEEE 15842002 have beendeveloped from extensive statistical analysis; it can beseen that the arc current formula is an excellent fitsince the average deviation is so low.

The arc current, duration, and distance from the arcsignificantly impact the incident energy. In compari-son with arc current, the energy incident on a surfaceis more variable and more difficult to accurately quan-tify. It would seem that the incident energy associatedwith open-air tests would be more predictable, sincethe arc plasma is not striking the box and being redi-rected. The results seem to demonstrate this trend,although the low-voltage tests are associated with amuch higher incident energy error. The 1.5 calculationfactor is a likely cause of the larger percent averagedeviation of the low-voltage tests.

The calculation factor was introduced in 1584 toreach a 95% confidence factor for predicting a PPEbased on incident energy levels of 1.2, 8, 25, 40, and100 cal/cm2. The 95% confidence factor was applied to165 low-voltage tests in 1584 with the followingresults: 64% correct PPE ratings and 95% PPE ratingsthat met or exceeded the requirement (in comparisonwith the respective 74% and 94% ratings listed inTable 4). The results presented in Table 4 may differsomewhat from the results published in 1584 becausethe distance factor in this analysis (selected as 1.641for every box) may differ and/or because three fewertests were included in this analysis.

Although IEEE 15842002 is an excellent achieve-ment in quantifying the arc-flash hazard, two caveats mustbe mentioned. The first is thatthe equations are based on statis-tical analysis. Real arc situationsand even arc tests performed byindependent groups may resultin arc currents and, especially,arc incident energies that do notconform well to the equationspresented in 1584. Furthermore,the maximum arc incident ener-gies have been recorded with thecalorimeters directly facing theelectrodes (for example, an elec-trician standing directly in frontof and facing an open panel). Ifthe calorimeters had been placedin-line with the electrodes (forexample, an electrical workerworking at the end of a long-runof terminating bus bars anddirectly looking at the cross-sec-tional area of the bus bars), therecorded maximum incidentenergy may have been muchlarger. Arcs tend to travel awayfrom (in the opposite direction

of) the voltage source [13]. The magnetic force, dri-ving the natural direction of the arc movement, alsodrives the plasma cloud and the convective energyassociated with the arc [8]. A more lengthy discussionof this topic is beyond the scope of this work.

Arc Current, Parc , and Incident Energy EstimatesUsing simple estimations provides ballpark numbersquickly and helps confirm whether plausible solutionsare obtained from complex formulas. In this section,simple formulations are used to provide ballpark esti-mates of arc current, arc power, and incident energyfor low-voltage systems, particularly 480-V systems.Since the data used in this formulation included onlyone 208-V test, these results cannot be applied to208-V systems. Arc data on 208-V systems is scarcebecause it is difficult to sustain arcs on 208-V systems

Ballpark and probable range for three-phase, 480-V, shallow-box incident energy

at 610 mm (24 in).

25

20

15

10

5

0

Inci

dent

Ene

rgy

(cal/c

m 2)

0.0 0.1 0.2 0.3 0.4 0.5Time (s)

Zsystem = 5 mZsystem = 10 mZsystem = 35 m

7

TABLE 8. TYPICAL 480-V BUILDING-SYSTEMIMPEDANCES.

Zsystem MVAsc Isc Iload Iratedm MVA A A A

5 46.037 55,400 2,770 4,000

10 23.019 27,700 1,385 2,000

15 15.346 18,467 923 1,200

20 11.509 13,850 693 1,000

25 9.207 11,080 554 700

35 6.577 7,914 396 500

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in laboratory test setups. One factor contributing tothis difficulty is that the arc voltage is such a large frac-tion of the 208-V supply.

From the mean and the standard deviation listed forthe short-circuit and arc power ratios in Table 1 underthe heading of

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Since many arcing-fault accidents occur when elec-trical maintenance workers are performing routinework on panels, shallow-box calculations are featuredin the remainder of this section. Some typical systemimpedance values in a 480Y/277 V system are listedin Table 8. The short-circuit current and MVA can befound from a known system impedance. The load cur-rent is assumed to equal 5% of the short-circuit cur-rent. Typical overcurrent-protective-device ratings,assumed to be at least 1.25 times the load current, arealso listed in Table 8. Figures 7 and 8 show the ball-park and probable range of the incident energy as afunction of time. The incident energies associatedwith a shallow box for 5-, 10-, and 35-m systemimpedances are graphed in Figure 7. The 5-m sys-tem impedance energies associated with a shallow box,a cubic box, and open air are graphed in Figure 8.

As an example, likely values and ranges of values forthe 5-m system impedance are calculated. The avail-able three-phase short-circuit current and short-circuitMVA are

Isc = 277/0.005 = 55, 400 A. (13)

MVAsc = 3 277 Isc = 46.037 MVA. (14)

The multipliers found in Table 5 and Table 6 are usedto predict the ballpark and probable range for arc cur-rent, arc power, and incident energy. The computationsare shown in Table 9. For the 5-m system imped-ance, the ballpark arc current is around 38.1 kA andthe probable range is 28.148.1 kA. The ballpark arcpower is around 15.3 MVA and the probable range is12.318.3 MVA.

The shallow-box configuration from Table 6 hasbeen used to calculate the ballpark and probable rangefor the rate of incident energy at 610 mm (24 in.) as aratio to the short-circuit MVA. The response time foran overcurrent protective device determines the dura-tion of arcing; in this example, the arc duration isassumed to equal 0.1 s. As listed in Table 9, ballparkincident energy is around 4.19 cal/cm2 and the proba-ble range is 3.185.21 cal/cm2. These numbers can beverified from Figure 7 or Figure 8.

Conclusions IEEE 15842002 was developed to help protect peo-ple from arc-flash hazard dangers. The predicted arccurrent and incident energy are used in selectingappropriate overcurrent protective devices and person-al protective equipment, as well as defining safe work-ing distances. Since the magnitude of the arc currentis inherently linked with the degree of arc hazard, thearc is examined as a circuit parameter in this work.From a circuit perspective, the magnitude of the arcvoltage determines the arc current in a given system.Therefore, the 1584 data set has been used to illus-trate how several parameters influence the arc voltage;

larger gap widths, higher supply voltages, and open-air configurations have been associated with greaterarc voltages.

A summary of statistical information regarding the1584 data set has been provided to promote a betterunderstanding of the origin of the numbers predictedby the 1584 arc-flash calculator. The analysis alsoindependently lends confidence to the accuracy of the1584 arc current and incident energy equations. Fur-thermore, since estimations are often useful, simpleequations for predicting ballpark arc current, arcpower, and incident energy values and probable rangesare presented in this work.

References [1] IEEE 15842002, New York: IEEE, 2002.[2] T. Neal, A. Bingham, and R. Doughty, Protective clothing guide-

lines for electric arc exposure, IEEE Trans. Ind. Applicat., vol. 33,no. 4, pp. 10411054, July/Aug 1997.

[3] R. Doughty, T. Neal, T. Dear, and A. Bingham, Testing update onprotective clothing & equipment for electric arc exposure, IEEEInd. Applicat. Mag., vol. 5, no. 1, pp. 3749, Jan/Feb 1999.

[4] R. Doughty, T. Neal, and H. Floyd, Predicting energy to bettermanage the electric arc hazard on 600 v power distribution sys-tems, IEEE Trans. Ind. Applicat., vol. 36, no. 1, pp. 257269,Jan/Feb 2000.

[5] R. Jones, M. Capelli-Schellpfeffer, R. Downey, S. Jamil, D. Liggett, T. Macalady, L. McClung, V. Saporita, L. Saunders, and A. Smith,Staged tests increase awareness of arc-flash hazards in electricalequipment, IEEE Trans. Ind. Applicat., vol. 36, no. 2, pp. 659667,Mar/Apr 2000.

[6] S. Jamil, R. Jones, and L. McClung, Arc and flash burn hazards atvarious levels of an electrical system, IEEE Trans. Ind. Applicat.,vol. 33, no. 2, pp. 359366, Mar/Apr 1997.

[7] D. Stokes and W.T. Oppenlander, Electric arcs in open air, J.Phys. D, vol. 24, no. 1, pp. 2635, Jan. 14, 1991.

[8] D. Stokes and D.K. Sweeting, Electric arcing burn hazards, inProc. 7th Int. Conf. Electric Fuses and their Applications, Gdansk,Poland, Sept. 2003.

[9] T. Gammon and J. Matthews, Instantaneous arcing-fault modelsdeveloped for building system analysis, IEEE Trans. Ind. Applicat.,vol. 37, no. 1, pp. 197203, Jan/Feb 2001.

[10] T. Gammon and J. Matthews, Conventional and recommendedarc power and energy calculations and arc damage assessment,IEEE Trans . Ind . Appl i ca t . , vo l . 39, no . 3 , pp. 594599,May/June 2003.

[11] R.H. Lee, The other electrical hazard: Electric arc blast burns,IEEE Trans. Ind. Applicat., vol. 18, no. 3, pp. 246251, May/June1982.

[12] NFPA 70E-2004, Standard for Electrical Safety in the Workplace,Quincy, MA: National Fire Protection Agency, 2004.

[13] L. Fisher, Resistance of low-voltage ac arcs, IEEE Trans. Ind. Gen.Applicat., vol. IGA-6, pp. 607616, Nov./Dec. 1970.

Tammy L. Gammon (tlgammon@ieee.org) and John H.Matthews (jomatthews@infoave .net) are with JohnMatthews & Associates in Cookeville, Tennessee. This arti-cle first appeared in its original form at the 2004 Indus-trial & Commercial Power Systems Technical Conference.

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01: v

02: vi

03: vii

04: viii

05: ix

06: x

footerL1: 0-7803-8408-3/04/$20.00 2004 IEEE

headLEa1: ISSSTA2004, Sydney, Australia, 30 Aug. - 2 Sep. 2004