Arc flash: other methods
IEEE 1584-2002 empirical model (superseded, for comparison with older studies)
- where
- arcing current (kA)
- −0.153 open air, −0.097 box
- bolted fault current (kA)
- system voltage (kV)
- conductor gap (mm)
- normalised incident energy (J/cm², 0.2 s, 610 mm)
- −0.792 open air, −0.555 box
- 0 unearthed or high-resistance earthed, −0.113 solidly earthed
- incident energy (J/cm²; shown in cal/cm²)
- 1.5 at ≤1 kV, 1.0 above
- arcing time (s)
- distance exponent
- working distance (mm)
- arc flash boundary (mm)
- incident energy at the boundary (J/cm²)
Explain this equation
Reproduces the superseded 2002 IEEE 1584 model, mainly to compare with older studies and labels.
Ia is found from a log-log fit to bolted current Ibf, voltage V and gap G; above 1 kV the arc voltage is small enough that Ia is a simple fraction of Ibf. En is the normalised energy at 0.2 s and 610 mm. K, K1 and K2 switch between open air and box and between earthing methods. Cf = 1.5 at LV is a calculation factor added for conservatism.
Energy scales linearly with t/0.2 and falls with distance as (610/D)^x. The exponent x is 2 for open air (like a point source) and lower in switchgear because the enclosure directs the energy forwards; 0.973 for HV switchgear means energy falls only slowly with distance.
Sense check: 480 V switchgear at 20 kA, 0.2 s, 610 mm gives about 4.8 cal/cm²; doubling the time doubles the energy.
Watch out: at LV the 2002 guide also required a run at 85 % of Ia with its own clearing time.
The 2002 edition of IEEE 1584. It is superseded by the 2018 model but still appears in older studies and labels, so it is useful for comparison.
Enter your values to see the result.
Good to know
K = −0.153 open air, −0.097 in a box; K1 = −0.792 open, −0.555 box; K2 = 0 for unearthed or high-resistance earthed systems and −0.113 for solidly earthed. Cf = 1.5 at or below 1 kV, 1.0 above. Distance exponents x: open air and cable 2.000; switchgear 1.473 (≤1 kV) and 0.973 (1–15 kV); MCC and panels 1.641 (≤1 kV). Below 1 kV the 2002 guide required a second calculation at 85 % of Ia with its own clearing time; this calculator uses the one time you enter, so repeat it with the time at 0.85 Ia. The 2018 model often gives markedly different results (higher for HCB and for small LV boxes), so do not mix methods on one site.
Common mistake
Keeping old 2002 labels after a system change or assuming 2018 results will be lower. The 2018 model replaced the open-air/box split with five electrode configurations and enclosure size, and HV results in particular can differ substantially.
Limits
IEEE 1584-2002 range: 0.208–15 kV, three-phase, 50 or 60 Hz, bolted fault 0.7–106 kA, gap 13–152 mm. Superseded by IEEE 1584-2018; use only for comparison or to reproduce an existing study. UK duty: under the Electricity at Work Regulations 1989 work on or near live conductors is allowed only where reg 14 is met (unreasonable to make dead, reasonable to work live, suitable precautions); regs 12 and 13 require isolation and precautions for dead working, and reg 4(4) requires suitable protective equipment. HSE HSG85 and your DNO or company safety rules (ENA-based distribution safety rules) take precedence. Apply the hierarchy of controls: de-energise first, then engineering controls (faster protection, maintenance switches, remote racking/operation, arc-resistant switchgear), then distance and procedures; arc-rated PPE is the last line of defence.
Sources
- IEEE Std 1584-2002 IEEE Guide for Performing Arc-Flash Hazard Calculations (superseded; empirical model and Lee method)
- ABB / Thomas Domitrovich et al.: Arc flash hazard analysis and mitigation (restates IEEE 1584-2002, Lee and Doughty–Neal equations)
- The Electricity at Work Regulations 1989 (SI 1989/635), regulations 4, 12, 13 and 14
For competent high-voltage engineers. Results are calculations from the published methods shown and depend entirely on the data you enter. They are not a substitute for a system study, manufacturer data, the applicable standards and Engineering Recommendations, or your organisation’s safety rules. Never use a result to justify working on or near live HV equipment.