I found out today when I got back to the office that a guy on another job was electricuted and airlifted by medical helicopter to a pittsburgh hospital's burn unit.
From what I understand, the guy was installing a test switch on an emergency ballast on a 2X4 trougher 277V. He was doing this with the power on.
He was working in a room alone with people near in other rooms. When he was being electricuted he could not let go. So, he kicked his ladder out from under himself. He fell about 4' to the floor. He was awake and breathing OK with no "bad" visible burn marks. They flew him as a precaution. Eveyone seems to think that he will be OK.
Sometimes it seems like it takes something like this to happen to us or around us to wake us up. When we hear stuff like NFPA 70E we think "we never had to do this kind of stuff before so I'll be fine". Tonight this guy is not at home with his family. He is in the hospital.
Please think about this the next time you decide to do something with the power on.
I'm glad he's OK. BTW, I was in a training class about a year ago, and the instructor seemed very proficient on the NEC. He told us we can expect a NEC change in the future that will require new light fixtures to have a local disconnect switch on them. I never researched this, and I don't know where he got this info, but it does seem to make sense.
Your instructor is probably correct. The new 2006 Canadian Electrical Code has the same requirement. All 347V lighting are to have a local disconnect means at *each* fixture. A recent report states that there has been a 30% increase in guys getting electrocuted due to working live.
Probably not on existing lights, but it might be a good idea to start adding it to bids on jobs that call for existing fixtures to have their ballasts replaced. I was surprised at the level of resistance to this change during the Code review process. Since every reputable manufacturer offers a fuse as on option, it seemed like a simple matter to expand it a bit into a disconnecting means and then make it mandatory. I thought that it should have been effective immediately upon adopting the new NEC, but at least it's in there now...January 2008 can't come soon enough for me.