During switching a line, what is the recommended sequence for opening devices?

During switching a line, what is the recommended sequence for opening devices?

• A. Open the breaker first to interrupt current, then operate the disconnect to isolate; close in reverse order.
• B. Open the disconnect first, then breaker; close in opposite order.
• C. Open both simultaneously with a control interlock.
• D. Only open the disconnect; the breaker remains closed.

Answer: (A)

The main idea is to remove the current with the device designed to interrupt it before you physically isolate the line. Opening the breaker first stops the flow and handles the arc in a controlled way, since circuit breakers are equipped to interrupt fault currents. Once the current is interrupted, you can safely operate the disconnect to provide a visible isolation from the source. This order avoids making or sustaining current through the isolation device and reduces the risk of arcing or backfeed during isolation. When re-energizing, you reverse the sequence: close the disconnect to reestablish the physical path, then close the breaker to restore power through that path. This approach keeps the switching path safe and ensures a controlled, reliable energization.

The main idea is to remove the current with the device designed to interrupt it before you physically isolate the line. Opening the breaker first stops the flow and handles the arc in a controlled way, since circuit breakers are equipped to interrupt fault currents. Once the current is interrupted, you can safely operate the disconnect to provide a visible isolation from the source. This order avoids making or sustaining current through the isolation device and reduces the risk of arcing or backfeed during isolation. When re-energizing, you reverse the sequence: close the disconnect to reestablish the physical path, then close the breaker to restore power through that path. This approach keeps the switching path safe and ensures a controlled, reliable energization.