Which table in the NEC is required for sizing the grounding electrode conductor for a grounded 12,470-volt system?

The correct choice for sizing the grounding electrode conductor for a grounded 12,470-volt system is found in Table 250.66 of the NEC. This table provides the necessary size for grounding electrode conductors based on the size of the service-entrance conductors.

In this case, it is essential to use Table 250.66 because it specifically outlines the requirements for the sizes of grounding conductors required to ensure adequate grounding and protection against fault currents in grounded systems of various voltages. The 12,470-volt system falls under the considerations outlined in this table, ensuring proper grounding for safety and functionality of the electrical system.

Table 250.68 pertains to grounding conductors for feeder and service equipment but does not directly specify the sizing for grounded systems. Table 250.56 focuses on grounding electrode conductors for specific types of electrodes, while Table 250.77 addresses connections for grounding and bonding. These tables serve different purposes and do not provide the specific sizing information for the grounded system as required in this scenario.