Which protective device can interrupt current flow through a distribution line?

• A. Fuse
• B. Circuit breaker
• C. Transformer
• D. Capacitor

Answer: (B)

When protecting a distribution line, you need a device that can quickly open the circuit to isolate a fault and then be reset afterward. A circuit breaker does exactly this: it trips to interrupt the current when overcurrent or a fault occurs, isolating the faulty section. After the fault is cleared, it can be reset and put back into service, which is essential for maintaining reliability on the system.

Fuses also interrupt current, but they are single-use and must be replaced after they blow, which isn’t as practical for continuous protection and automatic reclosure on distribution lines. A transformer changes voltage and current levels, not protect or interrupt faults, and a capacitor is used for reactive power and voltage support, not fault interruption.