So there is never a need for a small breaker with an AIC greater than 5,000 amps?
Well, that depends greatly on the distribution system and the size of the transformer. In this example, yeah, 5KAIC would be all that's required. But we could easily come up with another example (say, a 15A breaker on a 400A panel bus-fed from a 3000A switchboard/1MVA transformer) feeding a receptacle 6" from the panel. In THIS case, there is potential to exceed 5KAIC and damage the cable.
But in a typical residence, shorting out the receptacle? Not likely at all. The engineer really has to calculate all this and specify the KAIC rating of the breakers if it's expected to be an issue.
[This message has been edited by SteveFehr (edited 11-07-2006).]