Final answer:
The minimum size copper grounding electrode conductor for a service with three sets of parallel 350 kcmil conductors (three conductors per phase) should be a conductor with an equivalent circular mil area (CMA) of at least 594,604 circular mils.
Step-by-step explanation:
The minimum size copper grounding electrode conductor for a service with three sets of parallel 350 kcmil conductors (three conductors per phase) can be determined using the NEC (National Electrical Code) standards. According to the NEC, for a service with three sets of parallel conductors, the minimum grounding electrode conductor size should be equal to or larger than the equivalent circular mil area (CMA) of the largest phase conductor. To determine the equivalent CMA, we can use the formula CMA = (diameter in mils)².
Since each conductor has a size of 350 kcmil, we need to find the equivalent CMA of this size. 1 kcmil is equal to 1000 circular mils, so 350 kcmil is equal to 350,000 circular mils. Using the formula, the equivalent CMA of 350 kcmil is (sqrt(350,000))^2 = 594,604 circular mils.
Therefore, the minimum size copper grounding electrode conductor for this service would be a conductor with an equivalent CMA of at least 594,604 circular mils.