ARC Flash Exposure Outside of Enclosed Equipment

Abstract

Current standards have made good progress in helping engineers calculate the incident energy a worker would be exposed to when bare energized conductors are present. However, there are no alternate calculation methods or adjustment factors available to quantify the effects of equipment enclosures, or other conditions where a user maybe indirectly exposed to an internal arcing fault. IEEE C37.20.7, which sets criteria for Arc Resistant Switchgear, does not directly establish potential incident energy exposure levels outside the equipment under test. UL RP 2986 does begin to lay groundwork to quantify incident energy levels outside of enclosed equipment including instrumentation and testing parameters. However, it does not clearly define how to apply said procedures. This paper will address selection of appropriate parameters based on experience with testing low-voltage distribution equipment to the UL RP 2986 practice. Selected test results will be compared with the results of IEEE 1584-2018 calculations. The paper will also discuss the benefits of tested equipment that has been examined to measure the actual incident energy levels outside of enclosed equipment, including identifying situations where a worker may be shielded from incident energy levels greater than 1.2 cal/cm2.