Substation circuit breakers automatically provide opening and closing under fault conditions.

• A. True
• B. False
• C. Opening only
• D. Closing only

Answer: (A)

Substation circuit breakers work with protective relays that sense faults and trip the breaker to open, removing the fault current to protect equipment and keep people safe. Many schemes also include automatic reclosing, which closes the breaker after the fault is cleared to restore service. So, the system both opens automatically during a fault and can close automatically as part of restoring service. That makes the statement true. If you only consider opening, you’d miss the automatic closing after clearing the fault; if you only consider closing, you’d miss the essential opening during a fault; and calling it false would ignore the automatic protective actions.