Arc Flash Newsletter is a quick update on arc flash issues and ARCAD solutions addressing these issues. Visit us at www.arcadvisor.com for complete product offerings including free online arc flash calculator, and PC-based software solutions for arc flash and short circuit analysis and labeling.
Arc Blast Explosive Equivalent Calculations
The explosive nature of an electric arc has been documented in a number of case studies. The intense heat from an arc flash causes sudden expansion of air resulting in a blast, pressure waves and the resulting explosions rival that of explosive substances. Energies produced by arc flash explosions have been known to propel large objects such as switchboard doors, bus bars and personnel several feet at very high speeds.
Electric arcs produce some of the highest temperatures known to occur on earth - up to 35000 degrees Fahrenheit, 19500 degree Celsius. This temperature is four times higher than the temperature on the surface of the Sun. The intense heat from an arc causes sudden expansion of air resulting in a blast [...]. The arc flash blast energy or pressure is not currently addressed in IEEE 1584 or NFPA 70E. Ralph Lee's IEEE paper Pressures Developed by Arcs addresses arc blast phenomenon and provides the formula for calculating initial impulse force.
Previous edition of NFPA 70E from year 2009 required that labels to display either the available incident energy or the minimum arc flash rating for the Personal Protection Equipment (PPE). Also, every arc flash warning label had to list the system voltage, arc flash boundary, equipment identification and the date of the arc flash analysis listed on it.