What is the required table to size the grounding electrode conductor for a separate derived system according to NEC?

The appropriate table for sizing the grounding electrode conductor for a separate derived system, according to the National Electrical Code (NEC), is indeed Table 250.66. This table provides the necessary sizing requirements for grounding electrode conductors based on the size of the largest ungrounded conductor or the equivalent area of multi-conductor cables.

Sizing the grounding electrode conductor correctly is critical for ensuring the effectiveness and safety of the grounding system. Proper sizing minimizes the risk of excessive current flowing through the grounding conductor during fault conditions, which can lead to equipment damage or failure to clear faults.

Table 250.30 pertains to the grounding and bonding of separately derived systems, but it does not specifically address the sizing of the grounding electrode conductor itself. Table 250.102 deals with the sizing of bonding jumpers and the connections between grounding conductors and electrodes, while Table 250.52 outlines the types of grounding electrodes that are permitted. Therefore, while these tables are related to grounding practices, Table 250.66 is the specific one that governs the sizing of the grounding electrode conductor for derived systems.