In a separately derived system, what determines the size of the grounded conductor?

In a separately derived system, the size of the grounded conductor is determined by Table 250.102(C)(1) of the National Electrical Code (NEC). This table provides guidelines for sizing the grounding conductors based on the largest ungrounded conductor in the system. This is crucial because the grounded conductor is designed to handle fault currents, and its size must be proportional to the ungrounded conductors to ensure proper operation of overcurrent devices and to help maintain safety in the event of short circuits.

The rationale for using this table is rooted in electrical safety standards, which take into account the potential current that could flow in the event of a fault condition. By sizing the grounded conductor accurately according to the largest ungrounded conductor, you ensure appropriate protection for the system and related equipment, minimizing the risk of electrical fires or equipment failure.

Other options, such as the physical distance from the main service or the total length of the system, do not affect the sizing of the grounded conductor as established by the NEC. Additionally, while there may be general maximum sizes for copper conductors, those do not specifically relate to the sizing rules for grounded conductors in separately derived systems. Thus, the correct choice highlights the importance of standardized tables that ensure safe