What are guidelines and the scope of arc flash assessment?

The arc flash study calculation procedure should be in accordance with IEEE 1584 Standard and any amendments including IEEE Std 1584a and IEEE Std 1584b-2011. It is assumed that the equipment in the study is installed, operated, and maintained in accordance with manufactures' instructions or industry recognized standards. Three-phase AC circuits outside the range of IEEE Standard 1584 may be analyzed using other industry-accepted methods such as the Lee equations, which are also defined within IEEE 1584. Other equipment not covered by IEEE 1584 such as direct current, and overhead transmission and distribution systems, must either be excluded from the study or analyzed based on other industry-recognized methodology. Calculations can be run for single-phase equipment using IEEE Std 1584, assuming it has three-phase service that will yield conservative results. The guideline applies to existing systems, the expansion and modification to existing systems, and new construction.

For each piece of equipment under study, the analysis is used to determine the estimated short circuit and arcing currents, incident energy, incident energy at arc flash boundary (AFB) and AFB. As a minimum, the arc flash study should encompass all equipment likely to require service or inspection while energized from the customer owned service entrance equipment down through end user equipment rated 208 V nominal. The results of the arc flash study may also be used to develop recommendations such as changes to protective device settings in order to reduce the incident energy at locations where the incident energy level is deemed too high by the owner's representative. Prior to the start of the study, it is recommended that the lead investigator interview all the stake holders to obtain a snap shot on the health of the electrical system. These individuals should include owners, facility engineers, electrical superintendents, and line foremen.