Re: GROUND FAULT INDICATION FOR 480V UNGROUNDED DELTA SYSTEM
Actually an old-fashioned electrical system, but there are still plenty of them around. It has always been a good design practice to install ground detection lights on this type system, but do not think it has ever been an NEC requirement.
Basic parts of system are usually:
(3) small 480-120V. xfmrs connected wye primary - wye secondary, (3) standard 120V. xfmr-type pilot lights with clear or white lenses, & a test pushbutton for testing the pilot lights.
There are variations of course, including using full size medium base incandescent lamps.
The assembly can be built-up, but believe that some companies like G.E./Yokogama, etc. that still sell 4-1/2" analog meters, offer these in a package.
A true 480V. 3-phase 3-wire ungrounded delta system does not "shut down" if one leg goes to ground. This was one of the reasons for the older popularity of this system, mainly in industrial applications. I think most now consider it less desirable than a solidly grounded 480/277 wye for most applications.