Why does anyone use grounded delta transformers? A friend of mine was pulling his hair out on a service call that looked like a ground-fault on a B-phase of the service lateral and turned out to be a corner-grounded delta.
What is the utility of a corner-ground or center-tap ground delta? It seems like a waste of a perfectly good phase when a wye would have worked just fine.
I've heard that high-legs can be useful if you want to run a 208 single-phase lighting load. But even this seems questionable: I've only seen a couple of high-legs and they have never had any single phase loads on the "B" phase. Also, if you heavily load "B" phase, doesn't it ruin the ability of that phase to contribute to three-phase loads?
With a corner grounded delta, it seems like there is an advantage over a high leg in that there isn't the risk of inadvertantly burning up single phase loads put on "B" phase, but that phase is still useless otherwise.
I've heard that corner grounded delta banks were popular because it gave you the voltage stability of a wye, but it could be left running as an open-delta while one transformer was removed for service. Any truth to this? Does it also apply to high-leg deltas?
What's the deal?
-John
