What is the minimum size grounding electrode conductor (GEC) to the ground rod required for a panel fed from a transformer with four 500 kcmil copper conductors?

To determine the minimum size grounding electrode conductor (GEC) required for a panel fed from a transformer with four 500 kcmil copper conductors, it is essential to follow the guidelines provided by the National Electrical Code (NEC). The NEC specifies that the size of the GEC is based on the size of the largest ungrounded conductors supplying the panel.

In this scenario, the largest conductors are the four 500 kcmil copper conductors. According to NEC Table 250.66, the minimum grounding electrode conductor size for a grounding system connected to a grounding rod must align with the size of the feeder conductors. For a conductor size of 500 kcmil copper, the corresponding minimum size for the GEC is typically 6 AWG copper.

This minimum size ensures adequate ground fault protection, reduces the risk of electrical shock, and facilitates the safe operation of the electrical system. Therefore, choosing the 6 AWG size as the grounding electrode conductor provides both compliance with NEC regulations and safety for the electrical installation.