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exmweb.com | 1-800-363-2423 | [email protected] DATAARC FLASH CONSIDERATIONS814DEFINITIONArc Flash is a short circuit that flashes from one exposed live conductor to another, or to ground. The air immediately surrounding the short circuit can ionize. The resulting ionized air can create electrically conductive superheated plasma that can reach temperatures of 5000%u02da F. The explosion takes less than one second and produces a brilliant flash, intense heat and a strong pressure blast. HOW AND WHEN DOES IT OCCURArc Flash usually occurs while electrical equipment is being disconnected, inspected or serviced. It can be caused by a varieties of factors such as: 1) Accidental contact with live parts 2) Coming close to a high-amp source with a conductive object can cause the electricity, to flash over 3) Breaks or gaps in insulation or buildup on electrical terminals. 4) Dust, corrosion, presence of fumes, chemical vapors or other impurities that reduce the breakdown voltage of the air 5) Over voltage conditions 6) Equipment failure due to the use of substandard parts, improper installation, or even normal wear and tear 7) Sparks generated from racking in breakers, replacing fuses, or even from dropped tools Note: Arc flash in a panel cannot occur once all electrical power is disconnected. This is accomplished by disconnecting the remote disconnect that feeds the panel, as the panel disconnect does not kill the power to the line side of the panel disconnect. GENERAL BACKGROUND INFORMATION ON ARC FLASH The frequency of accidents and serious injuries resulting from Arc Flash had become too serious to ignore. Since 2002 many organizations have been developing rules and regulations to deal with the potential dangers of Arc Flash. These organizations are : National Fire Protection Association ( NFPA ) The Occupational Safety and Health Administration ( OSHA ) The National Electrical Code ( NEC ) The Institute of Electric and Electronic Engineers ( IEEE ) The NFPA 70E - 2004, which is a Standard for Electrical Safety in the Workplace, has become the norm and it has been adopted by NEC & OSHA. The NFPA 70E Standard provides assistance in determining severity of potential exposure, planning safe work practices, and selecting personal protective equipment. The IEEE has developed Standard 1584 Guide for Performing Arc Flash Calculations. Arc Flash is defined as incident energy impressed on a surface, a certain distance from a source, generated during an electrical arc event and it is measured in calories per centimeter squared ( cal / cm2 ) OSHA 29 CFR 1910.331-.335, Electrical Safety-Related Work Practices is the main defining requirements for protecting workers who may be exposed to electrical hazards. In enforcing worker safety procedures, OSHA cites the NFPA 70E standard as the \ance. OSHA is now citing and fining employers for failure to protect employees from the dangers of Arc Flash. 35,000 %u00baF Molten MetalPressure WavesSound WavesShrapnelHot Air-Rapid ExpansionIntense LightElectrical ArcCopper Vapor:Solid to VaporExpands by67,000 times