70E has TWO requirements on energized work. The first requirement is whether or not equipment is exposed, and there is no argument there. This captures shock hazards. The second requirement is for arc flash. It is not necessary for equipment to be exposed for a task to cause an arc flash. In this case, the argument to be made is when does it go from say cord-and-plug equipment which is defined under 70E, article 110.4(B), to equipment which uses a "plug" but which does not afford the same level of safety as cord-and-plug equipment. OSHA and NEC generally treat equipment rated 240 VAC single phase or less with up to 15-20 A plugs as distinctly different from say a 480 V, three phase, 4-wire plug, or say stabs in a busway, MCC bucket, panelboard, switchboard, or switchgear. Three major differences come to mind immediately:
1. Even without a switch to de-energize the load side, 15-20 A plugs can certainly arc. There is one recorded case in OSHA investigations in 2007 where an IT technician plugged in a laptop into a defective receptacle where it arced at the plug and burned the IT worker's hands, requiring hospitalization due to 2nd degree burns. 70E is intended to ensure survivability, not injury-free, so 70E would not require any sort of arc flash PPE to avoid this injury. Thus even if an arc flash hazard exists this type of equipment is generally acceptable even without a de-energization requirement without special PPE. Nothwithstanding even this design, GE Limitamp starters for instance are fairly well known where the linkage mechanism fails and has even caused at least one fatality and are pretty well known for "blowing up" on occasion. Here is documentation on the fatality that I know of:
http://work.alberta.ca/documents/WHS-PU ... -12-12.pdf
2. Stepping up to 480 V welding receptacles which are common in an industrial setting, the basic plug design is still a NEMA plug. The stabs can still mechanically misalign or bent into one another and cause an arc. However the arc will not self-extinguish and thus the arc flash can be substantial. These plugs have been known to explode while inserting or removing them while energized. Plugs and receptacles such as Cooper "Ark Tite" and Meltrics line of plugs as examples are mechanically interlocked such that shutters block insertion or removal while the receptacle is energized via a safety disconnect. This eliminates the issue, but the "line" side is de-energized.
3. Stepping up to panelboards, switchboards, MCC buckets, and switchgear buckets, there are sometimes mechanical shutters offering a degree of cover over the receptacles similar to the latest 2014 NEC requirement for residential 15/20 A receptacles, but generally there is not enough clearance afforded for workers to place their hands or fingers anywhere near the stabs when they engage into the bus. Irrespective of this design which would be truly shock hazard free, frequently the stabs still misalign and contact either each other or grounded enclosures and induce an arcing fault. ABB reports that 80% of arcing faults in their switchgear are due to the stab mechanism, and IEEE 493 data shows that drawout switchgear reliability is less than its bolt-in cousins.
That all being said, I personally believe that it is possible to design a plug-in arrangement where both shock and arc flash hazards can be eliminated during insertion or removal. If the stabs are spaced out where they cannot contact each other even if two of them are folded over, and the areas where the mating surfaces are at are all insulated, and keeping up with other designs, shutters are used to eliminate shock hazards, and there is a disconnect mechanism (mechanically interlocked to the shutters) on the line side. The sole remaining issue is that when the disconnect is closed, if not all stabs are electrically good connections, an arcing fault can still occur where a pin does not seat solidly into the socket. It may be possible to even design a mechanical interlock to prevent this but I'm going out on a limb here. If all of these precautions were taken then I can agree that ANY stab mechanism, not just limited to busway, can be made where I would argue that section 130.1 of 70E does not apply and that this is just operating equipment, not energized work,under the condition that if an arcing fault were to occur, it would be great enough to not satisfy condition #1 above (not above 1.2 cal/cm^2 or equivalent). This is the most conservative approach. However once you back away from this I would agree that some equipment can be provably shown to be reliable enough to not require this much. But don't fool yourself into thinking that just because there is no shock hazard that an arc flash hazard doesn't exist. And even if it does, it is not carte blanche enough to mean that it falls under 130.1. The definition of an arc flash hazard in 70E includes terms related to the likelihood of occurrence. 70E does not define this numerically because it is industry specific. But if you know your acceptance criteria then in some cases some of the more reliable equipment could be considered acceptable because the likelihood of an arc flash is no more than other comparable serious accidents and fatalities. I would argue though that in the case of data centers, the incident rate of serious injuries is pretty low, so the incident rate for arc flash should be comparable, and well below national averages.
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