amohammed wrote:
Jim,
In your article published in NEC digest in august 2007 "How to perform an arc-flash study in 12 step", you've recommended standardizing the flash boundary distance to six feet for live work. I can't seem to understand how can one work on a piece of equipment 6 feet away? (when I say work I mean racking in breakers or any other maintenance operation)
I know remote controlling of breaker racking is feasible at much larger distances. But I am sure this method of operation is pointless at just 6 feet.
I've learned quite a bit from this article and I appreciate your contribution.
Wow, this thread slid right on by me

- sorry. Here is what I meant by standardizng.
The Arc Flash Protection Boundary defines the minimum distance from a prospective arc flash where you need to wear PPE when an arc flash hazard exists. Over the years I have heard many people get excited about having different boundaries for each location based on the results of the arc flash calculation study. The concern is confusion.
Since the boundary applies more to those that are not properly protected, my take is if you are not performing the work and wearing appropriate PPE then just get out of the way. Splitting hairs over where the unprotected person must be i.e. 3 ft, 4ft, 5 ft, etc. makes this more complicated than it needs to be - just have the non protected people stay out of the way.
Of course there could be exceptions to this such as needing a helper close by but not standing within the AFPB. But.... if something goes wrong and the unprotected helper needs to rescue you during an arc flash, it could be quite bad.
What many people have been doing is adopting a standardized AFPB based on the largest (within reason) one from the study. This could mean 6 or 8 feet everywher. Combine this with using a 2 level PPE approach and you have a much simpler program. Again, the large AFPB should not affect the protected person doing work, it only affects the unprotected person by keeping them out of the way. Also keep in mind, we don't know everything (not even close) about how the arc flash acts. Last week I threw a bus bar (it was placed on the two stabs of a pad mounted transformer) about 20 feet with only 15 kA of arcing current at 480/277V. That's well beyond the AFPB.
Hope it helps!