NEC 2017 Art.100
Short-Circuit Current Rating. The prospective symmetrical
fault current at a nominal voltage to which an apparatus or
system is able to be connected without sustaining damage
exceeding defined acceptance criteria.
However it is not mentionned if the system is protected or self standing and how long duration.
In my opinion it is close to IEC 60947-1 /2004
2.5.27
short-time withstand current
current that a circuit or a switching device in the closed position can carry during a specified
short time under prescribed conditions of use and behaviour
