The next edition of IEEE 1584 no longer makes a distinction between grounded and ungrounded/impedance grounded systems.

Just out of curiosity, what types of grounding have you encountered?
Select ALL that apply.

Solidly Grounded
Ungrounded
Impedance Grounded (all types)

I voted all 3.

We have reactors on a couple of 7500 KVA, 34.5 to 4.16 kV transformers because without them our L-G fault current is a little higher than the equipment is rated for. If memory serves I think they are 0.1 ohm each. Not 100% sure on that though. I didn't design that installation.

We have dozens solidly grounded of delta-wye pad mounted transformers on campus for 480Y/277V and 208Y/120V "services".

We have several old 240V ungrounded delta "services" with fault indicator lights on the switchboards (see other thread on this.)

We have one 240V corner grounded delta "service" that I can think of off the top of my head.

We have a couple of 120/240V high leg delta "services" that I can think of. Those are center tap grounded.