The 480V Xo terminal is grounded to the transformer case and to a Ground Rod at the transformer. The transformer is a Pad-mount about 30 feet from the building served. Only the 3 phase conductors are in the nonmetallic conduit to the building. Since this is an existing installation, (appears about 4 years old replacing an overhead supply), do not know if the grounding electrode conductor in the tranformer pad opening extends into the separate building, but if the GEC does extend into the building, it definitely is not run with the circuit conductors 250.30(A)(5).
If this were a Service, 250.24(B) would require the grounded conductor to be installed with the circuit conductors to the main disconnect(s).
Since this is a SDS, and the Xo terminal is grounded, 250.30(A)1st sentence tells us that it SHALL comply with (1) thru (6). I do not interpret a correlation to 250.24(B) in 250.30.
The question is: Since the Xo terminal is grounded at the transformer, does a grounded (circuit ?) conductor need to be run with the derived phase conductors to the first disconnecting means in the seprate building?
