ℹ About This Calculator
Arc flash is the explosive release of energy from an electrical fault, and its severity is measured as incident energy in cal/cm² at a given working distance. IEEE 1584 is the international standard for estimating that energy and selecting the correct PPE category. This calculator applies a simplified IEEE 1584 model so you can screen panels quickly before commissioning a full arc flash study.
Incident energy scales almost linearly with fault clearing time, which makes protection settings the single biggest lever on arc flash risk - halving the clearing time roughly halves the energy. Enclosed switchgear focuses the arc and raises energy by about 50% versus open air, and energy falls sharply as working distance increases. Results above 40 cal/cm² mean no practical PPE exists and the design must be changed: faster protection, arc-resistant switchgear, remote racking or maintenance switches. This tool is a screening estimate - a full IEEE 1584 study with a validated short-circuit and coordination model is required for labelling and compliance.
Arc Flash Incident Energy Formula (IEEE 1584)
IEEE 1584
Arcing current: Ia = 0.85 × I(bolted) Incident energy (simplified IEEE 1584): log E = 1.081 × log(Ia) + 0.0011 × D − 1.081 × log(D/610) + log(t) + 0.9 × log(V) E = 10^(log E) × k Where: E = Incident energy (cal/cm²) Ia = Arcing current (kA) D = Working distance (mm) t = Fault clearing time (s) V = System voltage (kV) k = 1.5 for enclosed (box), 1.0 for open air PPE categories (cal/cm²): < 1.2 = PPE 0 | < 4 = PPE 1 | < 8 = PPE 2 < 25 = PPE 3 | < 40 = PPE 4 | > 40 = Danger
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