Supplementary overcurrent protection may be used to protect internal circuits of equipment. Which of the following best describes this application?

• A. Internal circuits of equipment
• B. Branch circuits only
• C. Outdoor equipment only
• D. Service conductors only

Answer: (A)

Supplementary overcurrent protection is an extra protective device used to guard the wires and components that are inside equipment itself. It provides a targeted level of fault current interruption for the internal circuits, such as control circuits or internal wiring, beyond what the external branch-circuit protection handles. This is why the description best matches protecting internal circuits of equipment. It isn’t meant to describe protection for general branch circuits, outdoor equipment specifically, or service conductors, which are outside the equipment’s internal circuitry.