250.30(a)(4)

[Smart $]

http://www.schneider-electric.com/s...ility-safety/low-voltage-minus-1kv/ect172.xml

See page 8.

The High Impedance Wye neutral is connected to the grounding system through a high impedance resistance that effectively isolates it from ground. It therefore acts like an ungrounded system. There is no other connection to the Wye neutral. Yes it is considered an IT grounding system.

The ungrounded Delta is also an IT grounding system.

The solidly grounded Wye is the only TT grounding system of the three at our site.

OK... I must have glance through your post (#77), because I thought you were saying the HIG wye system was TT. But now that I've reread [actuall read] the post I see that is not the case... my bad