SCCR is the successor to what we used to call “withstand rating”, in that it is the amount of current that can pass THROUGH a device or series combination of devices, without it reacting to the physical forces of the magnetic repulsion-attraction resulting from that current flow causing things to become shrapnel. It doesn’t have to survive and be used again, it just has to not cause collateral damage.
There is no fixed time value in the SCCR testing procure, however the way it works is that most power devices are allowed a 10kA value with minimal non-destructive testing, or a 5kA value with no testing. To be clear though, having a 10kA rating does not guarantee that it will survive, it is just basically an acknowledgement that since 10kA is pretty much the lowest interrupt rating of OCPDs anyway, it’s not much of a risk.
Then if you want a higher value SCCR, the device must be tested either by itself or in SERIES with a SPECIFIC OCPD (fuse or circuit breaker). In that test, the entire series combination must remain passive (official term for not become shrapnel) during the short-circuit interruption period of the line side protective device.
So the time period is whatever the fault clearing time is of the fuse or breaker portion of that tested series combination. This is one reason why you cannot field apply a current limiting fuse when you have too high of a fault current or a supplier punted and just applied a 5kA SCCR to a panel rather than try to get higher. Without testing, you have no way of knowing for sure if the downstream devices “remain passive” in that clearing time.
Side note: yes, I’m aware that in theory, a licensed PE can evaluate an untested series combination and approve it via a letter. I have in several cases tried to help customers with this method, I have never found a PE willing to do it.
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