What it means
An arc flash happens when electric current jumps through the air between conductors, or from a conductor to ground. The arc produces intense heat and light, and can create a pressure wave, loud noise and molten metal. It can be caused by things like a dropped tool, a loose or failed connection, equipment failure, or contamination such as dust or moisture.
Workplace electrical safety practices, set out in NFPA 70E, require the risk of arc flash to be assessed before work on or near energized equipment, and appropriate protective measures to be used. Much electrical equipment carries warning labels about arc flash hazards, and system studies are used to understand the hazard at different points in a facility.
An example: before opening a switchboard for maintenance, a qualified electrician reviews the equipment’s arc flash label and the site’s electrical safety procedures, puts the equipment in an electrically safe condition where possible, and uses the protective equipment the risk assessment calls for.
Why it matters
- Safety. Arc flash can cause severe injury in an instant.
- Maintenance planning. Accurate single-line diagrams and up-to-date studies support safe work and are expected by maintenance standards such as NFPA 70B.