Q. What size grounding electrode conductor is required for a 1,200A service supplied with three sets of 600 kcmil conductors per phase?

A. When not run to a ground rod, concrete-encased electrode, or ground ring, the grounding electrode conductor must be sized in accordance with Table 250.66. Because the equivalent area per phase equals 1,800 kcmil, the grounding electrode conductor is required to be 3/0 AWG.