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Arc Flash Incident Energy (IEEE 1584)
IEEE 1584-2018 arc flash incident energy formula — calculate cal/cm² to determine PPE category and arc flash boundary.
Formulas
E = 4.184 × Cf × En × (t/0.2) × (610^x / D^x)
IEEE 1584-2002 incident energy simplified (for reference)
Ia = 10^(K + 0.662×lg(Ibf) + 0.0966×V + 0.000526×G + 0.5588×V×lg(Ibf) − 0.00304×G×lg(Ibf))
IEEE 1584-2018 arcing current (simplified form)
Variable Definitions
E=Incident energy at working distance(cal/cm²)
Ia=Arcing current(amperes (A))
Ibf=Bolted fault current(kiloamps (kA))
V=System voltage(volts (V))
G=Gap between conductors(millimeters (mm))
D=Working distance(millimeters (mm))
t=Arc duration (protective device clearing time)(seconds (s))
Worked Example
480V switchboard, 20 kA bolted fault, 32mm gap, 610mm working distance, 0.5s clearing time.
- Step 1: Calculate arcing current using IEEE 1584-2018 model
- Step 2: Determine clearing time from protective device TCC at arcing current
- Step 3: Calculate incident energy using IEEE 1584 equations
- Note: Full IEEE 1584-2018 calculation requires software (SKM, ETAP, EasyPower)
Answer: Use IEEE 1584 software — example result: ~8-12 cal/cm² (PPE Category 2)
When to Use
- •Arc flash hazard analysis per OSHA/NFPA 70E requirements
- •Determining required PPE level for electrical work
- •Calculating arc flash boundary distance
- •Evaluating protective device coordination for arc flash reduction
Standards & References
- NEC 110.16 — Arc Flash Warning Labels
- NFPA 70E — Standard for Electrical Safety
- IEEE 1584-2018 — Arc Flash Hazard Calculations
- OSHA 29 CFR 1910.269