Arc Flash

Arc flash events occur when an electric arc forms in air — through equipment failure, accidental contact, or insulation breakdown — releasing intense thermal radiation, pressure waves, and molten metal. The thermal energy at the worker's position, measured in calories per square centimetre, determines the severity of potential burns and the level of personal protective equipment required. IEEE 1584-2018 introduced an updated empirical model based on extensive testing that accounts for electrode configuration, enclosure size, gap distance, and system voltage. The calculation requires knowing the bolted fault current, protective device clearing time, and working distance. Results categorise hazard levels from below 1.2 cal/cm² (minimal PPE) to above 40 cal/cm² (extremely dangerous). Arc flash studies are mandatory in many jurisdictions for switchboards rated above certain thresholds. The arc flash boundary defines the distance at which incident energy falls to 1.2 cal/cm² — the onset of second-degree burns. Reducing clearing times through faster protective devices is the most effective way to lower incident energy levels.