OK ... let's see if this link works:
http://printfu.org/read/electrical-...Ll2ubbyuOhrrG5mKihlLm0w7jTrbi0oNnS2oiw6gIt should take you to a paper called "Electrical Breakdown Limits for MEMS," at a site called Printfu . "MEMS" stands for 'Micro Electro-Mechanical Systems." The paper seems to be part of an electrical engineering course. Engineers: Were you sleeping through this class?
The paper opens with the graph that Mr. Engle SHOULD have had in his article.
It seems that "Paschen's Law" is at the root of some of the problems in developing micro-technology. Simply put, there aren't enough ait molecules to let an arc form at distances much less than a human hair's thickness.
OK ... so the reference to Paschen's law was relevant, and correct. Where does that leave us?
It seems to leave us with the strange situation that a sustained electrical arc - as opposed to the occasional spark - cannot cannot form between two ROUNDED COPPER electrodes in ordinary air at household voltages. We can discount the high impulse voltage that is created when the circuit opens since this is not a sustained voltage. Sparks, yes; arc, no.
For an arc to form, something else must happen. Jagged contacts. Materials other than just plain copper. An atmosphere besides air.
Oddly enough, this conforms to a sample I had, where a nicked wire was able to very neatly arc-cut through EMT for a length of about 1/8".
That still leaves us with any 'arc detecting' device being dependent on something else also happening. Sounds pretty iffy to me.
So, I'll grant Mr. Engle his point. Arc detection is pretty much a solution in search of a problem.
NEC Panels: Time to dump the AFCI. Period. Completely. It's pure snake oil. Absence of any actual arc testing in the UL standard ought to make that plain. (Perhaps that's why the standard is priced at approximately it's weight in gold).
Where do we go from here? Well, now it's the 'glowing contact.' I'm not so sure about Mr. Engle's opinions there, and that's a topic for another thread.
