Arc Flash Boundary & Incident Energy Calculator

Commercial-grade Arc Flash analysis tool based on IEEE 1584-2018. Calculates Incident Energy ($E$), Arc Flash Boundary ($AFB$), and generates compliant NFPA 70E Labels. Accounts for Enclosure Geometry (VCB, HCB, etc.) and System Grounding.

1. System Parameters
2. Equipment Geometry (IEEE 1584)

Technical Deep Dive: IEEE 1584-2018

Table of Contents

1. The Physics of Arc Flash: Air Plasma

An arc flash is an electrical explosion caused by a low-impedance connection through air to ground or another phase. Unlike a bolted fault where current flows through copper bars, an arc fault flows through ionized air (plasma).

This plasma is extremely hot (up to 35,000°F), causing the air to expand explosively. The calculation model estimates the Incident Energy (heat) released, which determines the severity of burns to a worker standing at a specific distance.

Incident Energy ($E$)

Energy is proportional to Time. If a breaker fails to trip, energy skyrockets linearly. $$ E \propto V \times I_{arc} \times Time \times \frac{1}{Distance^2} $$ The IEEE 1584-2018 model refines this with empirical coefficients derived from thousands of lab tests.

2. Electrode Configurations: Direction Matters

The 2018 standard introduced five electrode geometries because the direction of the arc blast significantly changes the energy hitting the worker:

  • VCB (Vertical in Box): Standard panel setup. Arc is pushed down, but heat reflects out.
  • HCB (Horizontal in Box): Conductors point at the worker. The magnetic force propels the plasma directly outward. This configuration produces the highest incident energy (often 2-3x VCB).
  • VOA (Vertical Open Air): Overhead lines. Heat dissipates in all directions. Safer.

3. Arcing Current Variation ($I_{arc}$)

Arcing current is always lower than the bolted fault current ($I_{bf}$) because the arc itself has resistance. However, arcing current is chaotic. It can fluctuate.

The Danger: If $I_{arc}$ drops too low, it might fall into the "long time" portion of a breaker's trip curve. A 10% drop in current could increase trip time from 0.05s to 2.0s, increasing energy by 40x!

4. The Arc Flash Boundary ($AFB$)

This is the distance from the arc source where the incident energy drops to 1.2 cal/cm².
Significance: 1.2 cal/cm² is the onset of a second-degree burn (curable). Anyone inside this boundary must wear appropriate PPE. Outside this boundary, no special arc PPE is required (though shock protection may still apply).

5. Applicable Standards

  • IEEE 1584-2018: Guide for Performing Arc-Flash Hazard Calculations. The math engine behind this tool.
  • NFPA 70E-2024: Standard for Electrical Safety in the Workplace. Defines PPE Categories (1, 2, 3, 4) and labeling requirements.
  • OSHA 1910.269: Electric Power Generation, Transmission, and Distribution. Mandates hazard assessment.