Where can I read up on this? I have been through NFPA 70E training and this was not addressed.
Hopefully this helps.
From:
NFPA 70E, Standard for Electrical Safety in the Workplace
2012 Edition
ARTICLE 100
Definitions
Arc Flash Hazard. A dangerous condition associated with
the possible release of energy caused by an electric arc.
Informational Note No. 1: An arc flash hazard may exist
when energized electrical conductors or circuit parts are
exposed or when they are within equipment in a guarded or
enclosed condition, provided a person is interacting with
the equipment in such a manner that could cause an electric
arc. Under normal operating conditions, enclosed energized
equipment that has been properly installed and maintained
is not likely to pose an arc flash hazard.
Informational Note No. 2: See Table 130.7(C)(15)(a) and
Table 130.7(C)(15)(b) for examples of activities that could
pose an arc flash hazard.
Boundary, Arc Flash. When an arc flash hazard exists, 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 5 J/cm2 (1.2 cal/cm2).
Boundary, Limited Approach. An approach limit at a distance
from an exposed energized electrical conductor or
circuit part within which a shock hazard exists.
Boundary, Prohibited Approach. An approach limit at a
distance from an exposed energized electrical conductor or
circuit part within which work is considered the same as
making contact with the electrical conductor or circuit part.
Boundary, Restricted Approach. 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 inadvertent movement,
for personnel working in close proximity to the energized
electrical conductor or circuit part.