On Wed, 18 May 2016 05:27:39 -0500, "Dean Hoffman"
wrote:

That's an odd thing on the terminology. We deal with 3 phase 480.
The underground cable we bury is called quad. One wire is marked as
the ground from the factory. #4 has all the wires the same size. Cable
larger than that has the ground one size smaller than the other three.

250.122 will allow a smaller grounding conductor in any cable larger
than #10 (30a O/C device) as a general rule. The regular #8-3 with
ground will have a bare #10 in it for the EGC.