Circuit breaker
A switch built to interrupt normal and fault current.
An open breaker contact separates the two sides of a circuit. This is a schematic representation.
A circuit breaker can open a circuit carrying normal or fault current, within its interrupting ratings. Protection systems can command it to isolate a faulted part of the grid.
Opening a circuit under current
In a mechanical circuit breaker, separating current-carrying contacts can create an arc that must be extinguished. The breaker is designed to interrupt current within its ratings, including specified fault conditions. Its mechanism and insulating medium vary with the application.
The breaker is the part that physically interrupts the circuit. Protection relays or built-in protection decide when a fault requires opening it. A disconnect switch has a different role and may not be rated to interrupt load or fault current.
Why it matters
A breaker lets protection isolate a damaged section before a fault causes wider damage or disruption.