Check out 250.20 and 250.21.Is it legal to leave the XO unbonded (no bond/ground conductor of any kind attached to the XO) on a XFMR if it is only used as an isolation XFMR?
There is a detailed list of the types of supply for which one conductor must be grounded, along with some exceptions based on the intended usage.
A question is why you need an isolation transformer in the first place.
What they are used for, doesn't have anything to do with the code rules that require the use of grounded systems.There are 12 of these XFMR's installed at a casino. I'm told they are used as filter XFMR's for clean power.