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IEEE 1584:2018

Arc Flash Calculator

Free arc flash calculator for IEEE 1584:2018 incident energy, arc flash boundary, and PPE category. Built for Australian conditions. No login. No watermark.

Inputs

Fills the gap, working distance, enclosure size and electrode configuration with the typical values from IEEE 1584:2018 Tables 8 and 10. Every field stays editable.

Line-to-line, 0.208 to 15 kV. For a 230/400 V supply enter 0.4.

Three-phase prospective fault current at the equipment. 0.5 to 106 kA at 600 V and below, 0.2 to 65 kA above.

Protective device clearing time at the full arcing current

IEEE 1584:2018 also runs the calculation at a reduced arcing current (11.90 kA here). Read the clearing time at that current off the device curve. A slower trip can give the higher energy.

Arc to face and chest. Typically 455 mm for panels, 610 mm for LV switchgear, 910 mm for MV switchgear. Minimum 305 mm.

VCB suits most switchboards. VOA and HOA are open air, so the enclosure dimensions are not used.

Typical: 13 mm cable junction box, 25 mm MCC and panelboard, 32 mm LV switchgear, 104 mm 5 kV switchgear, 152 mm 15 kV switchgear. Range 6.35 to 76.2 mm at 600 V and below, 19.05 to 254 mm above.

▶Enclosure dimensions

Height and width set the equivalent enclosure size. Below 600 V, a box under 508 mm high and wide and no more than 203.2 mm deep is treated as shallow. The width must be at least four times the conductor gap.

Results

Incident Energy

7.01

cal/cm²

29.33 J/cm², full arcing current case governs

PPE Category

Cat 2

Minimum arc rating 8 cal/cm²

Arc Flash Boundary1373 mm
Arcing Current (full)13.64 kA
Arcing Current (reduced)11.90 kA
Full case, 200 ms7.01 cal/cm², 1373 mm
Reduced case, 200 ms6.15 cal/cm², 1265 mm
Enclosure Correction Factor1.000
Equivalent Enclosure Size (typical)20.00 in

Notes

  • Both cases use the same 200 ms clearing time. Read the clearing time at the reduced arcing current of 11.90 kA off the protective device curve and enter it: a lower current can take much longer to clear and raise the energy.

PPE

Category 2 (minimum arc rating 8 cal/cm²). Arc-rated shirt and trousers or coverall, arc-rated face shield and balaclava or hood, gloves, hearing protection.

Show the working
Step by step derivation of the result
StepWorkingResultReference
Equipment class and resolved geometryVCB (Vertical conductors in a box), gap G = 32 mm, working distance D = 455 mm, enclosure 508 x 508 x 508 mm (H x W x D)Custom (no auto-fill)IEEE 1584:2018 Table 8 and Table 10
Intermediate arcing current at 600 V (Iarc_600)10^(k1 + k2 lg Ibf + k3 lg G) x (k4 Ibf^6 + ... + k9 Ibf + k10) = 10^(-0.04287 + 1.035 x lg 20 + (-0.083) x lg 32) x 1.0782 = 10^1.1788 x 1.0782 = 16.272 kA16.272 kAIEEE 1584:2018 Equation 1, Table 1
Final arcing current (Iarc)1 / sqrt((0.6 / 0.4)^2 x (1 / 16.272^2 - (0.6^2 - 0.4^2) / (0.6^2 x 20^2))) = 13.643 kA (68.2% of Ibf)13.643 kAIEEE 1584:2018 Equation 25
Arcing current variation correction factor (VarCf)k1 Voc^6 + k2 Voc^5 + ... + k6 Voc + k7 at Voc = 0.4 kV gives 0.255, so the reduced arcing current is Iarc x (1 - 0.5 x 0.255) = Iarc x 0.8720.255IEEE 1584:2018 Equation 2, Table 2
Reduced arcing current (Iarc_min)13.643 kA x 0.872 = 11.903 kA. Check the protective device clearing time at this current: a lower current can take much longer to clear.11.903 kAIEEE 1584:2018 Equation 2
Enclosure typeNot a shallow enclosure (shallow needs Voc below 600 V, height and width both under 508 mm, and depth 203.2 mm or less)TypicalIEEE 1584:2018 Clause 4.8
Equivalent enclosure size (EES)Adjusted width 20.000 in, adjusted height 20.000 in, EES = (20.000 + 20.000) / 2 = 20.000 in20.000 inIEEE 1584:2018 Equations 11 to 13, Table 6
Enclosure size correction factor (CF)-0.000302 x EES^2 + 0.03441 x EES + 0.4325 = 1.0001.000IEEE 1584:2018 Equation 14, Table 7
Incident energy, full arcing current (E)12.552 / 50 x T x 10^(k1 + k2 lg G + k3 Iarc_600 / (k4 Ibf^7 + ... + k10 Ibf) + k11 lg Ibf + k13 lg Iarc + lg(1 / CF) + k12 lg D) with T = 200.0 ms, Iarc = 13.643 kA, CF = 1.000, D = 455 mm gives 29.330 J/cm² = 7.01 cal/cm²29.330 J/cm²IEEE 1584:2018 Equation 6, Table 3
Arc flash boundary, full arcing current (AFB)Distance at which the energy falls to 1.2 cal/cm² (5.0208 J/cm²): 1373 mm1373 mmIEEE 1584:2018 Equation 10
Incident energy, reduced arcing current (E)12.552 / 50 x T x 10^(k1 + k2 lg G + k3 Iarc_600 / (k4 Ibf^7 + ... + k10 Ibf) + k11 lg Ibf + k13 lg Iarc + lg(1 / CF) + k12 lg D) with T = 200.0 ms, Iarc = 11.903 kA, CF = 1.000, D = 455 mm gives 25.739 J/cm² = 6.15 cal/cm²25.739 J/cm²IEEE 1584:2018 Equation 6, Table 3
Arc flash boundary, reduced arcing current (AFB)Distance at which the energy falls to 1.2 cal/cm² (5.0208 J/cm²): 1265 mm1265 mmIEEE 1584:2018 Equation 10
Governing caseFull 7.01 cal/cm² against reduced 6.15 cal/cm², so the full case governs with 7.01 cal/cm². The boundary is the larger of the two, 1373 mm.Full arcing currentIEEE 1584:2018 Clause 4.10
PPE category7.01 cal/cm² against the 4 / 8 / 25 / 40 cal/cm² bands gives category 2, so PPE must be rated for at least 8 cal/cm²2NFPA 70E Table 130.7(C)(15)(c) minimum arc ratings

Standards referenced

  • IEEE 1584:2018. Guide for Performing Arc-Flash Hazard Calculations
  • IEEE 1584:2018 Clause 4.2. Range of the model
  • IEEE 1584:2018 Table 1. Arcing current coefficients (Equation 1)
  • IEEE 1584:2018 Table 2. Arcing current variation correction factor (Equation 2)
  • IEEE 1584:2018 Table 3, 4, 5. Incident energy and arc flash boundary coefficients
  • IEEE 1584:2018 Table 6, 7. Enclosure size correction factor (Equations 11 to 15)
  • IEEE 1584:2018 Table 8, 10. Typical conductor gaps, enclosure sizes and working distances
  • IEEE 1584:2018 Clause Annex D. Worked examples used to verify this calculator
  • NFPA 70E Table 130.7(C)(15)(c). PPE categories and minimum arc ratings

Where a lookup value is marked indicative, it has not been transcribed from the current edition of the standard. Check results against your own copy before relying on them for design.

Important: Calculated with the IEEE 1584:2018 model and checked against the standard's Annex D worked examples. The result is only as good as the fault level and clearing times entered. Check it against the standard and have it signed off by the person responsible for the installation before it goes on a hazard label or PPE schedule.

Parameters

Three inputs are required. The rest carry defaults, and the equipment class selector fills them with the typical values from IEEE 1584:2018. Inputs outside the range the model was built on are rejected rather than calculated, because the standard's equations are not valid there.

Equipment class
Fills the conductor gap, working distance, enclosure dimensions and electrode configuration from IEEE 1584:2018 Table 8 (gaps and enclosure sizes) and Table 10 (working distances). Options are LV switchgear, LV MCC or panelboard, shallow LV panelboard, LV cable junction box, MV switchgear to 5 kV and to 15 kV, and open air conductors.
Gotcha. If you override the gap or working distance afterwards, the calculator notes that it differs from the class typical. That is information, not a failure.
System voltage (kilovolts)
Nominal line-to-line voltage at the equipment. Enter 0.4 for a 230/400 V supply, 0.415 for 415 V, 11 for an 11 kV switchboard.
Valid range. 0.208 to 15 kV. At 600 V and below the model works from the 600 V coefficients and corrects the arcing current to the actual voltage. Above 600 V it calculates at 600 V, 2700 V and 14 300 V and interpolates.
Bolted fault current (kiloamperes)
The prospective three-phase short-circuit current at the equipment, from a fault study or from the transformer and cable impedances back to the source.
Valid range. 0.5 to 106 kA at 600 V and below, 0.2 to 65 kA above.
Arc duration (seconds)
The protective device clearing time at the full arcing current, including breaker opening time. Read it off the device curve at the arcing current the calculator returns, not at the bolted fault current.
Gotcha. Incident energy is directly proportional to this value. Halve the clearing time and you halve the energy.
Arc duration at reduced arcing current (seconds, optional)
IEEE 1584:2018 requires a second calculation at a reduced arcing current, because arcing current varies from fault to fault. The calculator shows that current. Read the clearing time at it off the same device curve and enter it here.
Gotcha. Left blank, both cases use the same time, and the calculator says so. On an inverse-time device a lower current can trip much more slowly, and the reduced case then gives the higher energy.
Working distance (millimetres)
Distance from the arc to the worker's face and chest, not their hands.
Typical values. From Table 10: 455 mm for panelboards, MCCs and cable junction boxes, 610 mm for LV switchgear, 910 mm for MV switchgear. The model needs at least 305 mm.
Electrode configuration (VCB, VCBB, HCB, VOA, HOA)
The conductor arrangement at the arc: vertical or horizontal, in a box or in open air, and for VCBB whether the conductors terminate in an insulating barrier. Each has its own set of coefficients in the standard.
Gotcha. Horizontal conductors in a box (HCB) usually give the highest energy, since the arc is driven straight out of the enclosure towards the worker. Picking VOA or HOA makes the calculation open air and ignores the enclosure dimensions.
Gap between conductors (millimetres)
The phase-to-phase gap at the arc point. Typical values from Table 8: 13 mm cable junction box, 25 mm MCC and panelboard, 32 mm LV switchgear, 104 mm 5 kV switchgear, 152 mm 15 kV switchgear.
Valid range. 6.35 to 76.2 mm at 600 V and below, 19.05 to 254 mm above.
Enclosure height, width and depth (millimetres)
The enclosure the arc occurs in. Height and width set an equivalent enclosure size, which drives the enclosure size correction factor. Not used for open air configurations.
Gotcha. Below 600 V an enclosure under 508 mm high and wide and no deeper than 203.2 mm is treated as shallow and uses a different correction. Otherwise anything under 508 mm counts as 508 mm, so a deep small box returns the same result as a 508 mm cube. The width must be at least four times the conductor gap.

The model and how it was checked

The calculator implements the full IEEE 1584:2018 empirical model for three-phase AC systems from 208 V to 15 kV, in this order:

  1. Intermediate arcing currents at 600 V, 2700 V and 14 300 V from Equation 1 and the Table 1 coefficients for the chosen electrode configuration.
  2. The final arcing current. At 600 V and below this is Equation 25; above 600 V it is interpolated to the system voltage.
  3. The reduced arcing current, using the arcing current variation correction factor from Equation 2 and Table 2.
  4. The enclosure size correction factor from Equations 11 to 15 and Tables 6 and 7.
  5. Incident energy from Equations 3 to 6 and Tables 3 to 5, for both the full and reduced arcing current, each with its own clearing time, interpolated to the system voltage above 600 V.
  6. The arc flash boundary for each case from Equations 7 to 10, at 1.2 cal/cm².

The higher incident energy of the two cases governs, and the larger boundary is reported.

Verification

The calculator is tested against both worked examples in Annex D of IEEE 1584:2018: the 4.16 kV medium voltage example in D.1 and the 480 V low voltage example in D.2. Every intermediate value the standard prints, from the intermediate arcing currents through the enclosure correction, energies and boundaries, is reproduced to the number of decimal places shown. It was also run against 105 120 cases from the official IEEE 1584-2018 spreadsheet calculator, and every result agreed to within 0.001 percent. The method follows the open source arcflash library by Li-aung Yip, which was verified the same way.

Limits

  • Three-phase AC only, 208 V to 15 kV. There is no single-phase or DC arc flash model, and nothing for systems above 15 kV.
  • The result is only as good as the fault level and clearing times you enter. Wrong clearing times are the most common source of error in an arc flash study.
  • One clearing time per case. Where a fault is fed from several sources that clear at different times, or the fault current changes as motors stop contributing, a multi-step calculation is needed.
  • There is no credit for arc-resistant switchgear, arc quenching systems, or maintenance switching modes. Model those by entering the clearing time they actually achieve.
  • The PPE category is the lowest whose minimum arc rating covers the calculated energy. Check it against your own PPE schedule and the clothing actually issued.

Check the result against the standard, and have it signed off by the person responsible for the installation before it goes on a hazard label or a PPE schedule. Redo it whenever protection settings or the supply change.

Worked examples

Each figure below is what the calculator returns for the inputs shown. Open the working panel under the results to see every intermediate step with your own numbers.

Example 1: 400 V MCC, 20 kA, 0.25 s clearing

Equipment class LV motor control centre or panelboard: VCB, 25 mm gap, 455 mm working distance, enclosure 356 by 305 by 254 mm.

  1. Arcing current at 600 V from Equation 1: 10 raised to (minus 0.04287 plus 1.035 times lg 20 minus 0.083 times lg 25), times the Table 1 polynomial of 1.0782, which is 16.609 kA.
  2. Correcting to 400 V with Equation 25 gives a final arcing current of 14.098 kA, 70.5 percent of the bolted fault current.
  3. The variation factor at 400 V is 0.255, so the reduced arcing current is 14.098 multiplied by 0.872, which is 12.300 kA.
  4. The enclosure is 305 mm wide and 356 mm high but 254 mm deep, so it is typical rather than shallow. Both dimensions are under 508 mm and count as 20 inches, so the equivalent size is 20 inches and the correction factor is 1.000.
  5. Incident energy from Equation 6 at 250 ms: 35.04 J/cm², which is 8.37 cal/cm², at the full arcing current, and 7.35 cal/cm² at the reduced current with the same time.

Result. 8.37 cal/cm² from the full arcing current case, arc flash boundary 1535 mm, PPE category 3 with a minimum arc rating of 25 cal/cm².

Example 2: the same MCC with a slower trip at the reduced current

Same inputs, but the device curve shows a 0.4 s clearing time at the 12.3 kA reduced arcing current instead of 0.25 s.

  1. The full case is unchanged at 8.37 cal/cm² and 1535 mm.
  2. The reduced case at 400 ms gives 49.20 J/cm², which is 11.76 cal/cm², with a 1898 mm boundary.

Result. 11.76 cal/cm² from the reduced case, boundary 1898 mm, still PPE category 3. A lower fault current gave 40 percent more energy because the device took longer to clear it. That is why the standard requires the second case.

Example 3: 11 kV switchgear, 12 kA, 0.2 s clearing

Equipment class MV switchgear up to 15 kV: VCB, 152 mm gap, 910 mm working distance, enclosure 1143 by 762 by 762 mm.

  1. Intermediate arcing currents are 8.598 kA at 600 V, 10.209 kA at 2700 V and 11.266 kA at 14 300 V. Interpolated to 11 kV that is 10.965 kA. The reduced current is 10.827 kA.
  2. Width 762 mm adjusts to 29 inches and height 1143 mm to 45 inches, an equivalent size of 37 inches and a correction factor of 1.292.
  3. Intermediate energies for the full case are 7.673, 10.304 and 11.527 J/cm², interpolating to 11.18 J/cm², which is 2.67 cal/cm². The reduced case gives 2.69 cal/cm².

Result. 2.69 cal/cm² from the reduced case, boundary 1522 mm, PPE category 1. At medium voltage the arcing current is close to the bolted fault current and the two cases sit close together.

Example 4: how much the electrode configuration and distance matter

Example 1 again, changing one thing at a time:

  • VCB, the base case: 8.37 cal/cm², boundary 1535 mm.
  • VCBB: 11.40 cal/cm², boundary 1580 mm.
  • HCB: 16.64 cal/cm², boundary 1662 mm.
  • VOA (open air): 3.85 cal/cm², boundary 944 mm.
  • HOA (open air): 7.86 cal/cm², boundary 1170 mm.
  • VCB worked from 910 mm instead of 455 mm: 2.77 cal/cm².

Horizontal bus in a box doubles the energy of the vertical case. Doubling the working distance cuts it to about a third, not a quarter, because for VCB at low voltage energy falls with distance to the power 1.6 rather than 2.

Arc Flash Analysis for IEEE 1584:2018

Arc flash is the sudden release of thermal and radiant energy during an electrical fault. It can reach temperatures of 19,000 °C in milliseconds and produce pressure waves strong enough to throw a worker across a switch room. This calculator implements the IEEE 1584:2018 model to determine the incident energy at a defined working distance, the arc flash boundary, and the corresponding PPE category.

Arc flash calculation walkthrough

  1. Bolted fault current. The prospective short-circuit current at the equipment, calculated from source, transformer and cable impedances.
  2. Arcing currents. The model converts the bolted fault current into a full and a reduced arcing current. At low voltage these are well below the bolted fault current.
  3. Clearing times. The time the upstream protective device takes to clear each arcing current, read off its operating curve.
  4. Equipment geometry. Electrode configuration, conductor gap and enclosure size.
  5. Working distance. 455 mm for panelboards and MCCs, 610 mm for LV switchgear, 910 mm for MV switchgear.
  6. Solve. The calculator returns incident energy, boundary and PPE category for the governing case.

Electrode configurations explained

  • VCB. Vertical conductors in a box. The most common arrangement for LV switchboards.
  • VCBB. Vertical conductors in a box, terminated in an insulating barrier. The barrier stops the arc running off the ends of the conductors, so it stays put and the energy at the worker is usually higher than VCB.
  • HCB. Horizontal conductors in a box. The arc is driven straight out of the enclosure, typically the highest energy of the five.
  • VOA. Vertical conductors in open air, such as outdoor bus work. Usually the lowest energy.
  • HOA. Horizontal conductors in open air. Higher than VOA because the arc is driven towards the worker.

PPE categories

Each category is defined by the minimum arc rating of the clothing:

  • Category 1 (minimum 4 cal/cm²): arc-rated shirt and trousers or coverall, arc-rated face shield, safety glasses, hearing protection, leather gloves.
  • Category 2 (minimum 8 cal/cm²): as category 1, with an arc-rated balaclava with the face shield, or a flash suit hood.
  • Category 3 (minimum 25 cal/cm²): arc flash suit and hood, arc-rated gloves.
  • Category 4 (minimum 40 cal/cm²): arc flash suit and hood rated to 40 cal/cm². Above 40 cal/cm² live work should not go ahead.

How to reduce arc flash hazard

  1. De-energise before work. Always the first option under AS/NZS 4836.
  2. Clear the fault faster with lower protection settings, a maintenance switch, or arc detection, within discrimination limits. Halving the clearing time halves the incident energy.
  3. Increase working distance with remote racking, remote switching or live-line tools.
Disclaimer: Arc flash hazard analysis should be carried out by a competent person to IEEE 1584:2018 and AS/NZS 4836, and redone whenever upstream protection or system topology changes. Check results against the standard before using them on a hazard label.

Common questions

What is incident energy in an arc flash analysis?+

Incident energy is the thermal energy received per unit area at the working distance during an arc fault, measured in cal/cm² or J/cm² (1 cal/cm² is 4.184 J/cm²). It sets the arc rating of the PPE a worker needs. IEEE 1584:2018 calculates it from the system voltage, bolted fault current, arc duration, conductor gap, electrode configuration, enclosure size and working distance.

How do I select the right PPE category?+

PPE categories are defined by minimum arc rating: Category 1 is 4 cal/cm², Category 2 is 8 cal/cm², Category 3 is 25 cal/cm² and Category 4 is 40 cal/cm². This calculator picks the lowest category whose rating covers the calculated incident energy. Above 40 cal/cm² there is no category and live work should not go ahead. Whatever the category, the arc rating of the clothing must be at least the calculated incident energy.

What is the arc flash boundary?+

The arc flash boundary is the distance from the arc at which incident energy falls to 1.2 cal/cm², the onset of a second-degree burn on bare skin. Anyone closer needs arc-rated PPE. It varies widely with fault current, clearing time and equipment. For a 400 V MCC with a 20 kA fault cleared in 0.25 s it is about 1.5 m.

What does the electrode configuration parameter mean?+

IEEE 1584:2018 tested five configurations: VCB (vertical conductors in a box), VCBB (vertical conductors in a box terminated in an insulating barrier), HCB (horizontal conductors in a box), VOA (vertical conductors in open air) and HOA (horizontal conductors in open air). Each has its own coefficient set. HCB and VCBB push the arc plasma out of the enclosure towards the worker and usually give the highest incident energy. VCB suits most switchboards.

Why does arc duration matter so much?+

In the IEEE 1584:2018 model incident energy is directly proportional to arc duration: double the clearing time and the energy doubles. Arc duration is the protective device clearing time at the arcing current, which is lower than the bolted fault current. The standard also requires a second run at a reduced arcing current, because a lower current can push a device onto a slower part of its curve. Faster protection is the most effective way to cut arc flash energy.

Is IEEE 1584:2018 valid for Australian installations?+

Yes. There is no Australian arc flash calculation method, and IEEE 1584:2018 is the model used for arc flash studies in Australia and New Zealand. AS/NZS 4836 requires the hazard to be assessed before work on or near live low-voltage equipment, and an IEEE 1584 calculation is the usual way to do that. The model covers three-phase AC systems from 208 V to 15 kV.

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