An arc flash hazard is defined by the National Fire Protection Association (NFPA) as “a dangerous condition associated with the
release of energy caused by an electric arc.” The hazard to personnel is related to the power available in the circuit and the
exposure time. People have been received injuries ranging from second degree burns of the skin to death. The causes range from
operator error, to equipment failure, to simply operating a breaker. NFPA 70E requires that a safety programs be in place to
prevent injuries and that arc flash assessments be performed.
Good statistics on arcing failures are hard to obtain. This is due to legal issues and the natural tendency of people to refuse
to report their own problems or admit mistakes. (When was the last time a corporate executive reported their insider trading?
Do you really expect a company to report that they paid out big buck because someone died from an arc blast? Most of the court
settlements are sealed.) Capschell Inc focuses on the safety issues related to arc flash. They do not care who is a fault, the
want to accumulate enough data to create reasonably accurate statistics on the number and types of arc related injuries and thus
to help prevent future injuries. They support a Fax Anonymous Registry (FAR) Project to help obtain good data on real events. Go
to the following site to contribute your experiences. http://www.capschell.com/FARProject1999.htm
When the arc is created the air in the switchboard is suddenly heated. This expansion creates a pressure wave. As metal change
state from solid to gas, more pressure is added to the environments. These pressure waves have sheared off 3/8” bolts and blown
covers off of switchboard. Substations have been blown apart by the pressure wave. This pressure wave can compress a person’s
chest enough to kill without ever burning the person. http://www.ieee-pcic.org/archive/arcs.pdf contains a paper on “Pressure Developed
by Arcs” by Ralph Lee
“Electric arc burns make up a substantial portion of the injuries from electrical malfunctions. The extremely high temperatures
of these arcs, about four time as high as that of the sun’s surface, can cause fatal burns at up to about 5 feet, an major jurns
at up to about 10 feet distance. Information for evaluation of the degree of hazard involved with various voltages and capacity
ratings of equipment is developed and the require precautions and protective means to avoid injury from this source are outlined”
in The Other Electrical Hazard: Electric Arc Blast Burns”, by Ralph Leeburns found at: http://www.ieee-p
cic.org/archive/The%20other%20Electrical%20Hazard%20%20%20Electric%20Arc%20Flash%20Burns.pdf