I was looking for terms like "current limiting"
A class T fuse is "current limiting", and if a fault (in an AC circuit) delivers as much as 200,000A short circuit current, the class T fuse blows so fast energy deposited in other series-connected components (switches, smaller breakers or fuses) is no more than they would normally experience when a 20,000A fault is cleared.
What this would do is allow a 22kA interrupt capability main breaker to hold together, not explode, while the class T fuse blew.
It isn't really limiting current, the 200,000A will flow, but time is limited because the class T fuse blows faster.
Similarly, a 22kA rated main breaker trips fast enough that 10kA rated branch circuit breakers don't become a safety hazard.
So that's what I thought "limiter" might mean. But I didn't find any such reference.
(My first thought was it was the British word for fuse. They use funny terms, you know.)
... because it won’t clear a short in the normal 4 ms.
Have any links to charts quoting clearing times that short?
The trip curves I've seen aren't shown below 10 milliseconds, which is a bit more than one phase of 60 Hz AC.
I haven't seen details on how the DC rated OCP devices perform with DC, in terms of clearing.
I've only observed that class T, rated 200kA for AC, is rated 20kA for DC. And while it is "current limiting" for that high AC current, down at 20kA it doesn't blow fast enough to protect anything downstream rated for less. Would be good to find a fuse that protects 2kA or 5kA devices.