Over the past 15 years, the evolution in regulations, codes, standards, as well as basic understanding of the arc hazard, has elevated the importance and priority of managing and mitigating this hazard in the workplace. The authors have been at the forefront of this evolution, including leading the design and implementation of arc flash mitigation programs in industrial facilities for over twenty years. This paper discusses arc flash hazard mitigation in a manner to help safety professionals in managing this hazard through understanding and application of appropriate regulations and standards, implementing hazard assessments, evaluating mitigation options, and designing and implementing control measures to reduce/eliminate risks.
Historically, electrical hazards were viewed as primarily electric shock or electrocution hazards. Electric shock entails passage of electric current through the body. A shock victim generally must make contact with an energized conductor, or otherwise become part of the electrical circuit. While addressing the electric shock hazard is certainly important and it is the cause of the majority of fatal injuries from electrical energy [1], it has masked a second important and unique electrical hazard associated with the intense radiant and convective energy released during an electric arc flash event. Arc flash victims do not have to make physical contact with an energized conductor or be a part of the electrical circuit. The victim may be several feet away from energized conductors or equipment and be severely injured by the intense thermal energy transfer produced by an electric arc. The arc hazard is not new. It has been present in industrial and commercial facilities since the beginning of electrification in the late 19th century. What is relatively new is that the science and technology necessary to understand and manage the hazard have evolved significantly over the past two decades. During this time, we have learned a great deal. Arc flash events are usually very short occurrences - typically less than 0.5 seconds in duration. Most occur faster than the unaided human eye can perceive. High-speed photography of laboratory simulations of arcing faults have provided images of how these events can engulf workers in a ball of fire. Electric arcs are very hot - next to the laser, the most intense heat source on earth. Temperatures in the arc can reach 35,000°F. People within several feet of an arc can be severely burned. Electric arcs can be caused by human, environmental, and equipment related factors. Arc flash events are actually multiple energy events, with intense blast, mechanical and acoustic energy accompanying the intense thermal energy.
In 1980, Brown and Cadick [2] described safe electrical work practices that included application of personal protective clothing from arc flash hazards. In 1982, Lee [3] published a theoretical model for estimating the risk of injury to personnel who may be exposed to an electric arc. This work led to the introduction of arc flash hazard discussions in technical forums, regulations, codes and standards.
