What does kA rating for a circuit breaker imply?

All circuit breakers are subjected to short circuit testing at their marked rating and are capable of successfully interrupting the fault current without undue damage to the circuit breaker. The circuit breaker should not be installed into an area where the prospective fault level is higher than the rating of the circuit breaker (except where cascading is used as a design feature under Wiring Rules). Commercial installations and installations close to distribution transformers will have relatively higher fault levels. Consult your energy distributor for the fault level at a given installation.