Hybrid Arc Flash Protection Within Electrically Classified Areas

Electrical equipment installed within electrically classified areas-Class I, Division 1 (Zone 1), or Division 2 (Zone 2) locations-require techniques to mitigate flame propagation. Class I, Divisions 1 and 2, or explosion-proof (NEMA 7) techniques are the most commonly used for this purpose. Other techniques, such as enclosed break, flame proof, and restricted breathing, are commonly available methods. A previous PCIC paper (Mendler et al., 2015) explored the electrical arc flash mitigation of the NEMA 7 design. It was found that this design mitigated the electrical arc flash energies, and helped protect personnel from electrical hazard. This paper will explore the percentage reduction in electrical arc flash energies outside the enclosure when an arc occurs inside an enclosure. This will be accomplished using a simpler lighter explosion-protected design. The results will be obtained using an analytical approach, a computational fluid dynamics (CFD) analysis, and with further testing using prototypes that will show enhanced personnel protection.