What is Electrical Arc Flash and what are the Standards?

What is an Electrical Arc Flash?

An electrical arc flash, as defined by National Fire Protection Association (NFPA), is “a dangerous condition associated with the release of energy caused by an electric arc.” It occurs when electrical insulation or isolation between conductors is broken or can no longer withstand the applied voltage (Electricity Forum, n.d.).

Arc flash can result when employees work on or near energized conductors and circuits, move near or make contact with the equipment, or a failure of the equipment occurs. Any of these conditions may cause a phase-to-ground and/or a phase-to-phase electrical fault (Electricity Forum, n.d.).

The temperature of an arc can reach more than 5000° F as it creates an intense flash of light and a loud noise. An enormous amount of concentrated radiant energy explodes outward from the electrical equipment, spreading hot gases, melting metal, and creating pressure waves (Fischer, n.d.).

The Dangers of Arc Flash

Every day in the United States, between 5 and 10 arc flash explosions occur. These explosions cause injuries which can range from minor burns to life threatening injuries and possible death. More specifically, the creation of pressure waves can damage hearing or brain function, and the intense flash can damage eyesight and can burn exposed or even covered flesh. In addition to these injuries, the fast-moving pressure wave can also harm other workers in the area who can be struck by loose material such as flying pieces of equipment, metal tools, and other projectiles (Electricity Forum, n.d.).

Standards for Electrical Arc Flash: Protecting Workers

The National Fire Protection Agency (NFPA) 70e standard requires the calculation of a “flash protection boundary” within which a person could receive a second-degree burn if an electrical arc flash were to occur. This imaginary boundary, which surrounds the potential arc point, specifies what level of personal protective clothing and equipment must be used by qualified workers who enter within that boundary. This standard also defines incident energy as “the amount of energy impressed on a surface, a certain distance from the source, generated during an electrical arc event.” That surface could be a person (Fischer, n.d.).

Incident energy is expressed in calories per cubic centimeter squared (cal/cm2). The flash protection boundary is the point at which the energy number is 1.2 cal/cm2, equating to a second-degree burn. As workers get closer to the energized equipment, that energy figure rises. This boundary is different for different types of equipment and depends in part on the voltages involved (Fischer, n.d.).

Although companies may be reluctant to enforce the 70E compliance standard due to the costs of increased PPE, it can be looked at as a type of arc flash insurance. Companies that do not comply with this standard may be subject to claims for personal injury and incidents resulting to death, which could cost millions of dollars in legal fees.

Proposed changes to OSHA 's general industry electrical installation standard (1910 Subpart S) focus on safety in the design and installation of electric equipment in the workplace. The changes draw heavily from the NFPA 70E standard.

Other standards that establish procedures for preventing arc flash incidents and ensure employee safety include: NFPA 70-2002, which requires that companies place a warning label on equipment likely to cause arc flash conditions; and IEEE Standard 1584-2002, which provides a method to calculate the incident energy in order to specify the level of PPE required for workers (Fischer, n.d.).

To view the entire NFPA 70E standard, [click here]

For more information about OSHA ’s general industry electrical installation standard proposed revisions, [click here]


References:

Electricity Forum, The. (n.d.). Arc Flash Defined. Retrieved 21 June, 2007.
http://electricityforum.com/arc-flash/arc-flash-defined.html

Fischer, Linda K. (n.d.). The Dangers of Arc Flash Incidents. Retrieved 21 June, 2007. http://www.mt-online.com/articles/0204arcflash.cfm#requirements