Overcurrent protective devices shall be so selected and coordinated as to permit the circuit protective devices used to clear a fault without extensive damage to the electrical components. This fault shall be assumed to be ___.

Overcurrent protective devices shall be so selected and coordinated as to permit the circuit protective devices used to clear a fault without extensive damage to the electrical components. This fault shall be assumed to be ___.

• A. neither I nor II
• B. II only
• C. both I and II
• D. I only

Answer: (C)

In overcurrent protection coordination, you design the system so that protective devices can clear a fault without causing extensive damage to the surrounding components. To ensure this holds for any real fault, the analysis uses a worst-case fault scenario. The standard worst case is a bolted fault—zero impedance between the fault and the source—which yields the maximum possible fault current. If the devices can clear this condition without extensive damage, they will also handle real faults, which typically have some impedance and produce less current. In practice, this worst-case is often modeled as a three-phase short circuit at the fault location, effectively representing the bolted fault scenario for coordination purposes. Therefore, both aspects described in the statements reflect valid aspects of the assumed fault condition, which is why the answer indicating both is correct.

In overcurrent protection coordination, you design the system so that protective devices can clear a fault without causing extensive damage to the surrounding components. To ensure this holds for any real fault, the analysis uses a worst-case fault scenario. The standard worst case is a bolted fault—zero impedance between the fault and the source—which yields the maximum possible fault current. If the devices can clear this condition without extensive damage, they will also handle real faults, which typically have some impedance and produce less current. In practice, this worst-case is often modeled as a three-phase short circuit at the fault location, effectively representing the bolted fault scenario for coordination purposes. Therefore, both aspects described in the statements reflect valid aspects of the assumed fault condition, which is why the answer indicating both is correct.