Arc Flash - Extent of Study
Arc Flash - Extent of Study
(OP)
I'm wondering how far all the experts are presently taking the arc flash analysis to. I have a 480 V MCC which supplies loads such as VFD's, motors, unit heaters. I've been on sites where tests were made at each of these, with covers off. The hazard could therefore exist, which implies analysis made at terminals of all those items.






RE: Arc Flash - Extent of Study
RE: Arc Flash - Extent of Study
RE: Arc Flash - Extent of Study
RE: Arc Flash - Extent of Study
We do not generally put arc-flash labels on motors.
RE: Arc Flash - Extent of Study
RE: Arc Flash - Extent of Study
I know a case can be made for labeling the disconnect switches, but we generally try to avoid it.
RE: Arc Flash - Extent of Study
RE: Arc Flash - Extent of Study
Arc flash hazard calculations
Tinsley, H.W. Hodder, M. Graham, A.M.
Eaton Electr., Warrendale, PA;
This paper appears in: Industry Applications Magazine, IEEE
Publication Date: Jan.-Feb. 2007
Volume: 13, Issue: 1
On page(s): 58-64
ISSN: 1077-2618
INSPEC Accession Number: 9243927
Digital Object Identifier: 10.1109/MIA.2007.265802
Date Published in Issue: 2006-12-26 08:38:30.0
Abstract
This article discusses a method for generalizing the arc flash calculations for select areas of a power distribution system. The method presented here helps to reduce the number of equipment locations and also calculations which are analyzed using a commercial software package. In an industrial example, this method reduced the number of small feeder locations that required a detailed analysis by 94%. This resulted in a large reduction of onsite data collection, detailed modeling, and arc flash warning labels
RE: Arc Flash - Extent of Study
As a practical matter, 480 V feeders downstream of a molded-case circuit breaker or current-limiting fuse will have arc-flash levels less than 8 cal/cm2 and probably less than 4 cal/cm2 except for situations with very low available fault current.
RE: Arc Flash - Extent of Study
jghrist, I found that article very useful.
RE: Arc Flash - Extent of Study
RE: Arc Flash - Extent of Study
I see two issues that you may have considered synonymous, when they are in fact opposite! Protection coordination is the opposite of arc flash protection. When we try to limit the arc energy, we do this by making the tripping time as short as possible, but when we try to coordinate trip times, we try to "delay" some protection setting to let the breaker nearer the fault to clear first.
RE: Arc Flash - Extent of Study
Very true. A consultant asked me, not long ago, a coordination study to reduce the energy at some switchgear...
RE: Arc Flash - Extent of Study