What are the parameters Icu, Ics and Icm for low voltage switchgear? What is the meaning?

"Low-voltage switchgear and control equipment Low-voltage circuit breaker" standard, the meaning of the above parameters are as follows:

Icu: rated ultimate short-circuit breaking capacity, refers to the conditions specified in the test program O-t-CO, the circuit breaker can not continue to carry its rated current capacity of the ability to break. That is, the circuit breaker can reliably break the short circuit current. The circuit breaker can continue to be used only under certain constraints.

Ics:Rated operational short-circuit breaking capacity, refers to the breaking capacity of a circuit breaker that can continue to carry its rated current capacity under the conditions specified in test procedure O-t-CO-t-CO. That is, the maximum short-circuit current that the circuit breaker can still reliably break. After cutting off this short-circuit current, the circuit breaker can still be used.

Icm:Rated short-circuit switching capacity Refers to the short-circuit current that can be switched on by the circuit-breaker equipment at rated operating voltage -10%, rated frequency and specified power factor under the conditions specified in the test procedure O-t-CO-t-CO.

In general, Icu ? Ics, Icm = n x Ics.

Note: O - breaking; t - intermittent time; CO - connecting and breaking.