Even though “many do it,” I don’t think live jacking in of circuit breakers, for example, in energized I-line panelboards is condoned.
In an IEEE journal, there is some commentary that seems to discourage intentional exposure of live parts in low-voltage industrial electrical systems.
UL standards for distribution equipment are written with the understanding that abnormal conditions will occur in electrical systems. Abnormal conditions may include explosive arcing and flaming of materials, either causing or resulting from heavy overcurrent conditions including arcing faults to ground and phase-to-phase short circuits.
It should be noted that enclosures for low-voltage electrical distribution equipment are also evaluated by the short-circuit testing of equipment they contain. Under these standard testing conditions, the enclosures are expected to retain general structural integrity and, in some cases, cotton indicators are used to show that nearby materials would not ignite. However, these tests in no way evaluate the ability of these enclosures to contain abnormal arcing or flaming from conditions other than interruption of a bolted fault. Further, equipment will not protect people working inside of it during the abnormality. IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, V35 N1, JANUARY/FEBRUARY 1999
Anecdotally, there are reports of serious disasters {er, burndowns} from live removal/installation of plug-in "starter buckets" in MCCs. I don’t see bus-plug removal/installation being much different.
[This message has been edited by Bjarney (edited 07-07-2003).]
