There are two indicators for the breaking capacity of circuit breakers: rated ultimate short-circuit breaking capacity Icu and rated operating short-circuit breaking capacity Ics. The rated ultimate short-circuit breaking capacity Icu is the limit parameter of the breaking capacity of the circuit breaker. After breaking several short-circuit faults, the breaking capacity of the circuit breaker will decrease. The rated short-circuit breaking capacity Ics is a breaking indicator of a circuit breaker, which means that after breaking several short-circuit faults, it can still ensure its normal operation. For molded case circuit breakers, Ics greater than 25% Icu are considered qualified, and currently most circuit breakers on the market have Ics between (50% -75%) Icu