Guys,

I have to admit to stepping well outside of my field of experience here. Here is what I said on my first post on the topic:
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Ungrounded systems are usually used for continuity of service. But what about an ungrounded system used for the purpose of reducing energy dissipated in a fault. If the breakers were arranged to detect and trip on a ground fault for an _ungrounded_ system, then IMHO this would meet the requirements of having a ground fault detector.

I was suggesting that if, _as a design choice_, someone were to use an ungrounded system for a reason other than continuity of service, then the requirements for ground fault detection might be met in a fashion other than indicator lights. I was offering this as a situation where ground fault detection was provided, but ground fault indicating lights were not used, and this was intended simply as a proposed answer to George's original question. This was not offered up as the next latest and greatest system design [Linked Image]

The design choice is the desire to detect and remove power from ground faults without having hundreds or thousands of amps flowing through the wiring and equipment grounding system in the event of a ground fault.

I do not know if listed devices are available that would function in this fashion. I do not know if anyone does this in NEC compliant permanent installations with this design goal in mind.

I know that normal GFCI devices are only used at 120V. So a standard GFCI breaker is out. But ground fault detection equipment certainly exists for 480V systems, people complain about GFP on this board whenever they encounter a ground fault system that is not properly coordinated. So 480V two pole and three pole ground fault detecting breakers are certainly _conceivable_ products even if you can't get them off the shelf.

-Jon