mparenteau wrote:
All,
Opinions please:
I've read a number of research papers w/ regards to arcs @ voltages below 250V, specifically 208V. It seems to me there is a large body of evidence to suggest that MOST arcs at this voltage level self-extinguish at 10 cycles or less (I read one paper w/ regards to spot networks/network protectors, and then there is of course NESC guidance which uses that clearing time to calc PPE for utility applications).
Question: Why isn't this utilized more in the industry? I know there may be some anomalies where 208V can self-sustain for longer, but from what I've read it doesn't seem significant. Furthermore, if a technician/electrician can dress down I think this is a good thing. How many times have we all calculated AFIE at a panel fed by a small dry type, and the AFIE is off the charts? This instance doesn't make practical sense to me, it does however, if the 10 cycle clearing time is used as it drops the AFIE to what seems to me, to be a more manageable and practical number.
Thoughts? Thanks in advance,
Mike
Usually the 2-second rule can be invoked in such situations, which drops the incident energy down to a very low number. I don't know much about the greater industry at large, but I'd guess that in most circumstances, invoking the 2-second rule would be enough. I suppose that's a bit of a non-answer.
