I have always wondered as to why does a circuit breaker in the IEC World have so many short circuit breaking capacities such as Ics(service short circuit breaking capacity), Icu(ultimate short circuit breaking cap), Icw (short circuit breaking capacity). After running an ETAP Programme we reach an initial symmetrical short circuit current (say 40 kA) which in turn determine the short circuit rating of the switchgear for 1sec/3 sec( I..E 40kA for 1 second). Some of the suppliers consider it as the prospective short circuit current and match the Icu rating of the breaker( 40kA) to be used on such a switchgear . Shouldn't they select Icw rating of the breaker to match the switchgear short circuit withstand current for 1 sec. Your suggestions will be of great help.
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