IEEE Method Vs. the NFPA 70E Tables

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IEEE Method Vs. the NFPA 70E Tables: Evaluating arc flash analysis methods

BY REZA TAJALI, Schneider Electric

Recent changes in workplace safety regulations have heightened the awareness of hazards associated with electrical arcs. The hazard level must be quantified and workers properly protected before entering proximity of exposed energized conductors. National Fire Protection Association’s (NFPA) standard 70E: “Standard for Electrical Safety in the Workplace” provides the guidelines for work involving electrical hazards and the selection of arc flash protective equipment.

In order to select the protective gear properly, one must have knowledge of the potential thermal energy of the electric arc. The Institute of Electrical and Electronics Engineers (IEEE) standard 1584: “Guide for Performing Arc-Flash Hazard Calculations” has been the de facto standard for calculating the arc energy levels at different points in the electrical power system.

However, NFPA 70E also provides the option of using the Hazard/Risk Category (HRC) task tables for personal protective equipment (PPE) selection. These tables provide pre-defined levels of PPE, which are based on the available short circuit current and the speed of the overcurrent protective device. Therefore, in order to apply the tables properly, some degree of electrical calculations must be performed and the tables could be subjected to misuse if they are applied without knowledge of the necessary calculations.

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