What is an electric arc flash?
– NFPA 70E: “A dangerous condition associated with the release of energy caused by an electric arc”
– Blinding flash of light followed by a deafening explosion
– Large amount of energy discharged from electrical equipment with hot gases and molten metal
How is arc flash caused?
– Electrical insulation failure or insulation system can no longer withstand the applied voltage
– Inserting tool in wrong place or dropping into an energized area
– “Accidental” contact with energized electrical parts
What type of damage does it cause?
– Serious bodily injury or death
– Permanent irreparable equipment damage
– Loss of plant production
– Plant-wide outages
What can you do to protect yourself against arc flash?
– Avoid energized electrical work if possible
– Use properly rated PPE for given task
– Know hazard risk involved before working
What are the latest arc flash injury statistics?
– Capelli-Schellpfeffer: 10 to 15 workers in U.S. injured daily
– 1 to 2 deaths every day
Can the energy from an arc flash be predicted before it occurs?
– Yes, can be computed using power system analysis
– Dependent on OCPD tripping time and available fault current
– Routine PM of electrical equipment is key
Can arc flash incident energy be mitigated?
– Yes, by adjusting OCPD settings or using device with more “flexibility”
– Must keep equipment protective boundaries and load inrush requirements intact
– Should re-consider the trade-off of protective device coordination and/or system reliability versus lower arc flash incident energy levels