NFPA 70e Calculations - Determining Safe Work Practices

NFPA 70e calculations are necessary to properly determine the explosive arc flash energy level of a worker who could be exposed. This explosive energy is measured in calories/cm2. This is outlined by NFPA 70E - 2004, Electrical Safety Requirements for Employee Workplaces, states, “A hazard analysis shall be done in order to protect personnel from the possibility of being injured by an arc flash. The analysis shall determine the Flash Protection Boundary and the personal protective equipment that people within the Flash Protection Boundary shall use.”

NFPA 70e arc flash regulations have been developed by the National Fire Protection Association as a standard for Electrical Safety in the Workplace. It is one of the foremost consensus standards for electrical safety. It covers employee protection from the electrical hazards of shock, arc flash and arc blasts.

Annex D in NFPA 70E offers the same incident energy level equations that appear in IEEE Std. 1584, but the latter goes into more detail. NFPA 70E doesn't specify that the IEEE Std. 1584 method has to be used. The incident energy level could be determined using one of the several arc-flash software programs that are currently available on the market.

As understanding of NFPA 70e calculations has grown, several methods for calculating the hazard have been developed. Three of these methods will be examined in this section—the theoretical model, the equations and tables used in NFPA 70E-2004