What is breaker-failure protection?

• A. A scheme that trips a backup breaker if the primary breaker fails to interrupt the fault.
• B. A scheme that tests breaker integrity after switching.
• C. A protection that prevents any tripping during faults.
• D. A system that resets after each fault automatically.

Answer: (A)

Breaker-failure protection is a safeguard that ensures fault current is interrupted even if the primary circuit breaker fails to open. When a fault occurs, the protection system commands the main breaker to trip, but if that breaker does not actually open within a preset time, a dedicated breaker-failure relay detects the lack of opening (or sustained fault current) and trips a backup breaker to clear the fault. This quick secondary action prevents continued current, arcing, and damage to equipment, while helping maintain system reliability and selective isolation of the fault.

This isn’t about testing breaker integrity after switching, it doesn’t aim to prevent tripping during faults (the protection is there to ensure tripping occurs), and it isn’t a function that automatically resets after each fault.