arc-flash analysis of utility power systems - Michigan Technological ...

He also provides charts to determine the pressure wave forces at distances from an arc
based on the fault level [5]. In 1990, the threat of an arc flash was well-established,
and OSHA updated 29 CFR-1910 Subpart S to recognize the need for arc-flash safety
[4].
Two other papers have been published that look at the energies in arcing faults.
The first published in 1997, Testing Update on Protective Clothing and Equipment for
Electric Arc Exposure, uses empirical test data to determine the incident energy at
distances from a low voltage arcing fault. This was the first paper to address the
directional effect of an arc in an enclosure. The second paper published in 2000,
Predicting Incident Energy to Better Manage the Electric Arc Hazard on 600-V Power
Distribution Systems, provided equations to determine incident energy based on the
fault level, working distance and the clearing time for arcs in air and in an enclosure
on a 600 volt system
(2.1)
! " (2.2)
where
E MA
E MB
= incident Energy (cal/cm 2 ) for an arc in open air
= incident Energy (cal/cm 2 ) for an arc in a box (20 in. maximum)
D A , D B = distance from the arc in inches
F = bolted Fault Current (kA)
t A
= time of arc exposure (seconds)
(2.1) and (2.2) were developed based on test data collected from three-phase
arc tests conducted in testing laboratories. These tests were conducted under specific
conditions in order to collect different incident energy levels. Curve fit equations
were then applied to the data to allow the incident energy of the system to be
predicted. As can be seen in the equations, the simple form of energy at a given
6