Joe,
Sorry I'm late on this one, ThinkGood seems to have covered the 1910 ref. for Medium Voltage, you can also find references in the NESC.

The reason you'd have difficulty for under 600V is.... It's NOT allowed. You can search 1926 all you want you'll only find reference to Lockout/Tagout. They make no provisions for working energized equipment.

The concession to MV circuits was made long ago, because 1) the Utility workers are more trained in the aspect and 2) Because they are able to work energized the resulting inconvenience to customers was weighed in as part of the equation.

It also goes a bit deeper than inconvenience. When you interrupt an MV distribution circuit, you may have to reenergize by opening up lots of stuff downstream or risk system failure from overload.....

The very reason on Thursday they could not wait for the system to "Calm down" and simply reclose all breakers, the resulting inrush/locked-rotor would have devastated the system. Trumpy had the term perfect "Hunting". Yes, it is scientifically Sub-synchronous resonance, but since the gen actually "hunts" for the right spot, it is a better term.

Anyone with REALLY old CEE's would find an article on a genset of mine that did just that, at which point I dove in and opened it (it makes a BEG difference if you are the one who would have to repair the gen [Linked Image] )

Since anything under 600V is local by nature, OSHA saw no reason to have rules for working energized. Again, it also had to do with how highly trained ALL folks in that field are on the subject. This group here is pretty danged sharp, but there are lots out there that would get hurt.

Now, anyone here ever work it hot????????
Course, not!!!! [Linked Image]