When overcurrent devices are selectively coordinated and a fault occurs somewhere on a branch circuit, what is expected to happen?

When evaluating the scenario of selectively coordinated overcurrent devices during a fault on a branch circuit, the expected outcome is that the branch circuit overcurrent protective device (OCPD) nearest to the fault should open. This coordination is a design strategy that ensures that only the protective device closest to the fault experiences the fault current and trips, thereby isolating the fault without affecting the entire system.

This selective coordination is crucial in allowing other circuits and downstream devices to continue operating while protecting the affected circuit. It helps maintain system availability and prevents unnecessary interruptions of service. If the main circuit breaker were to trip, as suggested by another option, it would lead to a more extensive outage than necessary, impacting more circuits than intended.

In contrast, expecting all connected devices to automatically shut down or presuming that the fault should correct itself does not align with standard electrical safety practices or design principles. The design is specifically aimed at ensuring that the least amount of disturbance occurs while safely managing overloads or faults.