Pauluk:
277 volt fixtures here are rare but they do exist... Often its a case where a building contains a lot of machinery designed for use in the U.S.A and a 277Y / 480V supply is used. (The PoCo will NOT supply this , you must step 600V down to 277Y / 480 yourself). There are only two buildings I know of in the area that use this system as well and I will make mention there is one other building in this city that has a "240Y 416V" system in it.. VERY rare in Canada and why it was done I do not know but the 240V electric heating we installed was connected to this system and was all connected line-neutral which is a bit bizarre for us Canucks, as 240V is usually a line-line voltage!
This brings be back to some of the different lighting voltages we have here for lighting .. We do have some H.I.D stuff in parking lots that is sometimes "208V" or "240V" and it works fine and is safe because these voltages originate from supplies that are 120V to ground. The catch with that is with standard autotransformer type H.I.D ballasts whereby one side of the line is connected to the appropriate ballast "tap" and the other is connected to the ballast "Common" lead which is also connected to the metal screw-shell of the lamp... See the problem here? Should someone decide to change a lamp in a live fixture wired 208V or 240V and they happen to touch the screw-shell of the lamp and ground while doing so, blammo they get a 120V shock.
We also have 600V lighting as well but again this is rare and generally its found in the steel mills where the system originates from a 600V ungrounded delta supply
(according to my Father), and the ballasts for these are "isolation" type, so no real chance of touching the screwshell of a bulb and getting a 347V blast..
My highschool was another oddity that had 600V fluorescent lighting in 1/2 the building, only because the half that contained this lighting also contained all the machine / welding, wood, electrical,and auto shops as well as the boilers and all its related equipment,all of which was 600V, and in 1963 when the place was built I don't think 347V lighting even existed let alone a 347Y/600V service being availible from the PoCo, although it may have originated from a grounded Y secondary, no neutral was present as far as I can remember.
A.D
