When a fault occurs in the AC generation system, which component activates to protect the circuits?

• A. Circuit breaker
• B. Generator breaker
• C. Fuse
• D. Battery disconnect switch

Answer: (B)

When a fault occurs in the AC generation system, the device that protects the circuits by isolating the generator is the generator circuit breaker. This breaker sits between the generator and the bus and is controlled by protective relays that monitor current, voltage, and other fault indicators. When a fault is detected, these relays trip the generator circuit breaker, quickly interrupting the generator’s connection to the system. This prevents the fault current from spreading, protects the generator windings and switchgear, and helps maintain overall system stability.

The other options aren’t as suitable for this protective role. A general circuit breaker protects downstream parts of the distribution system but isn’t the primary device for isolating a faulty generator from the grid. A fuse can’t reliably handle the high fault current and rapid isolation needs of a generator, and it isn’t easily reset for quick re-energization. A battery disconnect switch isolates the battery, not the generator, and isn’t used to clear faults in the generation circuitry.