Breaking capacity or interrupting rating[1][2] is the current that a fuse, circuit breaker, or other electrical apparatus is able to interrupt without being destroyed or causing an electric arc with unacceptable duration.
Calculation of the required breaking capacity involves determining the supply impedance and voltage.
In North American practice, approved general-purpose low-voltage fuses must interrupt at least 10,000 amperes.
Types used in commercial and industrial low-voltage distribution systems are rated to safely interrupt 200,000 amperes.
The rating of power circuit breakers varies according to the application voltage; a circuit breaker that interrupts 50,000 amperes at 208 volts might be rated to interrupt only 10,000 amperes at 600 volts, for example.