NFPA 70E Proposed DC Arc Flash Updated Guidance

The Standard for Electrical Safety in the Workplace (NFPA 70E) is the industry standard for electrical worker safety. In 2012 DC arc flash guidance was added to the document. There have been updates since then, but most arc flash calculations still rely on the maximum power method that has been unchanged since 2012. The maximum power method is overly conservative, and in most cases, overestimates the true hazard. Additionally, some users are multiplying the result from the maximum power method by three for anything in a cabinet even though this specific multiplier has been removed from the standard in the 2018 version. This results in an even more conservative calculation.The main issue with updating the guidance has been the lack of test data for dc arc flash. AC arc flash has been well characterized by comprehensive testing and modelling resulting in very specific guidance in IEEE 1584. However, over the past several years, several organizations have conducted dc arc flash testing and much of this has been reported. Additionally, there have been efforts, including by a co-author, to better characterize the risk through modeling using this test data.This paper will propose changes to the next revision of NPFA 70E which the authors plan on turning into public inputs which will be submitted in the summer of 2024 for the 2027 revision. These changes will attempt to provide updated guidance in both article 130 and Annex D.5, which will improve overall worker safety and provide more accurate guidance. Multipliers for events in panels and cabinets will also be considered.