We have several mission critical facilities that use an ungrounded delta system.
In the event of a ground fault the system stays energized until it can be corrected.
The only time that the system goes down is when there is a second ground fault before the first one gets cleared.
An ungrounded delta is kinda capacitively coupled to the Earth, so a ground detector device is used.
There are 3 lights wired from phase to a ground rod and all glow continuously at the same brightness.
If one of the phases has a ground fault that light will go out and the other 2 get much brighter.
That tells you which phase the ground fault is on...but finding where it is becomes very challenging.
One of our facilities has had a ground fault on one of the phases for several years...and the maintenance folks are still trying to chase it down.
I think there may be a ground in 2 places on the same phase; which is like trying to find the 2 bad bulbs in an old string of Christmas lights.
