ECN Forum Forums General Topics of the Trade General Discussion Area Ungrounded Delta Service

I don't think you can measure voltage from phase to ground on a straight delta system, only phase to phase.

Lear with a typical DVM you can measure voltages to ground from an ungrounded system.

However I agree with Ryan that the readings you get will be erratic and meaningless.

If you have a delta system feeding line-to-neutral loads, it's not corner grounded, but center-tap grounded. The "main" winding has the tap, just like your 240/120v. home, and the other two windings meet at the "high leg".

Nope, seperate neutral. Three phase service with one leg at "0" potential to ground and 240 volt between all phases.

Twice in 20 years and I'm not sure those faciities are still wired as such.

If you had a delta system with a neutral tap on one of the secondaries, and a corner ground, then you would get a pretty dangerous situation that would _work_ with most loads. For 3 phase loads you would have 240-240-0, just like a normal corner grounded system. But for single phase loads you would have 240-120-0 instead of the normal 120-0-120 (all voltages relative to ground). Standard 120V lamps would function in sockets, but the socket would _always_ be energized. Add anything with a ground-neutral bond and _bang_.

-Jon