Section 6/Incident Energy Calculation
IEEE 1584 Section 6 covers incident energy calculation at the working distance using electrode configuration equations.
The incident energy calculation determines the thermal energy (cal/cm2) a worker would be exposed to at a specified working distance from an arc flash event. The 2018 edition uses empirical equations derived from extensive testing and replaces the simplified Lee method with equations covering three electrode configurations: vertical conductors in a box (VCB), vertical conductors in open air (VCBB), and horizontal conductors in a box (HCB). Inputs include the bolted fault current, the gap between conductors, the working distance, the enclosure size, and the arc duration (determined by the protective device clearing time).
Why this section exists
The incident energy value determines the minimum arc rating of PPE that a worker must wear. An underestimated incident energy leads to inadequate PPE and severe burns. An overestimated value leads to excessive PPE that reduces worker dexterity and increases heat stress. The 2018 IEEE 1584 equations are based on over 1,800 arc flash tests across a range of voltages, currents, and configurations, providing more accurate results than the previous 2002 edition, especially for equipment with enclosures (panelboards, switchgear, MCCs).
What plan reviewers look for
Plan reviewers check that the arc flash study uses the correct IEEE 1584 edition and electrode configuration for each piece of equipment. They verify the bolted fault current at each location against the short-circuit study. They check the protective device clearing times from the coordination study. They verify the working distance assumption (typically 18 inches for panelboards, 24 inches for switchgear, 36 inches for MCCs).