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Arc Flash Incident Energy & Boundary Screening Estimator

Arc flash explosions release violent blast pressure and thermal energy capable of causing fatal burns. This tool provides preliminary screening calculations based on IEEE 1584 equations to estimate incident energy (cal/cm² and J/cm²), determine the Arc Flash Boundary (AFB), and evaluate protective garment tiers under BS EN 61482-1-1 (ELIM) in accordance with EAWR 1989 Reg 14.

Safety & Compliance Advisory: Regulation 14 of the Electricity at Work Regulations 1989 prohibits work on or near live conductors unless it is unreasonable for them to be dead, reasonable to work live, and suitable precautions are taken. Above 40 cal/cm² (167 J/cm²), blast overpressure shockwaves defeat thermal PPE; under EAWR Reg 14 it is difficult to see how live working could be justified at this energy level. De-energise upstream to work dead, or operate live switchgear via remote racking outside the flash boundary.

1. System Voltage & Fault ParametersNominal System VoltageProspective Bolted Short-Circuit Current (kA)Symmetrical RMS fault level from network study or transformer rating.Protection Arcing Clearing Time (seconds)Total relay trip time + breaker mechanical opening time (e.g. 0.12s = 6 cycles).

2. Working Geometry & EnclosureWorking Distance (D) from Arc PointDistance from the operator's face/chest to the potential arc source.IEEE 1584-2018 Electrode ConfigurationConductor Busbar Gap (mm)Typical LV busbar gap: 25 mm to 32 mm; 11kV switchgear: 104 mm to 152 mm.

Thermal Blast Assessment

CALCULATING...

BS EN 61482 Protective TierELIM ≥ 8 cal/cm² (Class 1)

Estimated Arcing Current (Iarc)--

Vicinity Shock Boundary (BS EN 50110-1)--

Evaluating IEEE 1584 thermal risk...

⚠WARNING

Arc Flash and Shock Hazard Appropriate Arc-Rated Clothing Required

Flash Hazard Boundary: 1.45 m

Incident Energy: 5.8 cal/cm²

Working Distance: 457 mm

Min Clothing Rating: ELIM ≥ 8 cal/cm²

Shock Hazard: 400V •BS EN 50110-1 Vicinity Boundary: 300 mm •Standard: BS EN 50110-1 • BS EN 61482-1-1

IEEE 1584-2018 Incident Energy & Boundary Formulation

IEEE 1584-2018 & BS EN 61482-1-1 / BS EN 61482-1-2

AM2 PORTFOLIO & DESIGN AUDIT FORMATTRANSPARENT FIRST-PRINCIPLES MATHS

Scenario: 400 V main switchboard, bolted fault current of 25 kA, arcing clearing time of 0.12 s (6 cycles), working distance of 457 mm (18 in), vertical conductors in a metal box (VCB):

Arcing Current (Iarc): At 400 V with a 32 mm gap, arc impedance reduces current to approx 20.5 kA (approx 82% of bolted fault).
Incident Energy (E): Under IEEE 1584-2018 polynomial formulation, incident energy evaluates to 5.8 cal/cm².
Arc Flash Boundary (AFB): The distance at which incident energy drops to 1.2 cal/cm² is 1.45 metres. Anyone within 1.45 m must wear rated protective garments.
Protective Specification: 5.8 cal/cm² mandates arc-rated protective clothing with BS EN 61482-1-1 ELIM ≥ 8.0 cal/cm² (or Box Test Class 1 / Class 2), including arc-rated balaclava and face shield.

Blast Pressure Wave Hazard (> 40 cal/cm²): Above 40 cal/cm², arc flash events generate blast pressure shockwaves exceeding 2000 lbs/ft², vaporising copper (which expands 67,000 times) and projecting shrapnel. Thermal clothing cannot prevent concussive chest trauma. Remote racking devices or complete upstream safe isolation are strictly required under HSE HSG85.

Duty-Holder Engineering Notice: First-principles calculation based on IEEE 1584-2018 formulas and BS EN 61482-1-1/2 thermal clothing tiers for competent engineers. This tool provides preliminary estimates and does not replace a stamped site-specific electrical system power study or equipment warning label.

Engineering Standards: IEEE 1584-2018 • BS EN 61482-1-1:2019 • BS EN 61482-1-2:2014 • EAWR 1989 Reg 14 • HSE HSG85