What is the correct term for the first disconnecting means on a separate derived system?

The correct term for the first disconnecting means on a separate derived system is the over-current device. This device is critical in electrical systems as it protects the wiring and equipment from the damaging effects of excess current that could lead to overheating, fires, or equipment failure.

In a derived system, which may be a separate source of power—such as a generator or a transformer—the over-current device serves as the initial point of disconnect when responding to overloads or faults. This ensures that the entire system is safeguarded right from the outset of the derived system, providing essential protection against unacceptable levels of current flow.

While the main breaker, service panel, and load center have their specific functions in the overall electrical distribution network, they do not specifically denote the first point of protection against over-current as defined for a separate derived system. Understanding the role of the over-current device is crucial for ensuring compliance with electrical safety codes and for proper system design.