WHY AN ARC FLASH STUDY?
Recall that as part of the electrical safety program, per NFPA 70E ® -Article 110.7 The employer shall implement and document an overall safety program that directs the work activity appropriate for the voltages, energy level, and circuit conditions. If the work involves electrical hazards Article 130.3 states that a an Arc Flash Hazard Analysis shall determine the Arc Flash Protection Boundary and the personal protective equipment that people within the Arc Flash Protection Boundary shall use. As a result of the employer is responsible to promote electrical safety in the work place. As facility managers work to implement arc flash safety they want the answer to the following question:
ARC FLASH….BOUNDARY, WHAT ARE THE LIMITS?
Per NFPA 70E ® – Article 100 2012 Edition
The answer is found in the definition of shock hazard analysis and shock protection boundaries as follows:
NFPA 70E 130 Work Involving Electrical Safety Hazards
130.4 Approach Boundaries to Energized Electrical Conductors or Circuit Parts.
Shock Hazard Analysis. A shock hazard analysis shall determine the voltage to which personnel will be exposed, the boundary requirements, and the personal protective equipment necessary in order to minimize the possibility of electric shock to personnel.
(B)Shock Protection Boundaries. The shock protection boundaries identified as limited , restricted , and prohibited approach boundaries shall be applicable where approaching personnel are exposed to energized electrical conductors or circuit parts.
Table 130.4(C) (a) shall be used for the distances associated with various ac system voltages. Table130.4(C)(b) dc system voltages.
Now the Arc Flash Boundary as well as the Limited, Restricted and Prohibited Boundaries can be better understood:
Arc Flash Boundary
“an approach limit at a distance from a prospective arc source within which a person could receive a second degree burn if an electrical arc flash were to occur. Informational Note: A second degree burn is possible by an exposure of unprotected skin to an electric arc flash above the incident energy level of (1.2cal/cm2).
Limited Approach Boundary
An approach limit at a distance from an exposed energized electrical conductor or circuit part within which a shock hazard exists.
Restricted Approach Boundary
An approach limit at a distance from an exposed energized electrical conductor or circuit part within which there is an increased risk of shock, due to electrical arc-over combined with in advertent movement, for personnel working in close proximity to the energized electrical conductor or circuit part.
Prohibited Approach Boundary
An approach limit at a distance from an exposed energized electrical conductor or circuit part with in which work is considered the same as making contact with the electrical conductor or circuit part.
Although Article 130.3 Exception No. 2 permits the requirements of 130.7(C) (9), (10), and (11), in lieu of a detail incident energy analysis, a detail study can assist personal with the documentation that is an essential part of the electrical safety program.