Which leads me to the question of 'What does it mean for a fuse to be current limiting?'
If the breaker is rated to 50kA, and the fuse is 'current limiting' to 40kA, then the breaker should never 'see' more than 40kA...but if, in the initial moment of a short you actually see more than 50kA of current, until the 'current limiting' effect kicks in, then the speed of the breaker is quite relevant.
What differentiates the following:
1) Limiting fault current via 'current limiting' fuses.
2) Limiting fault current via the resistance of extra service/feeder conductor.
3) Limiting fault current via adding line reactors.
4) Limiting fault current via coiling the service/feeder conductors up to form 'air core' inductors.
The consensus seems to be that 1) is 'hard' and that a PE would need to sign off on this application, but that 2) is easy, just part of normal fault current calculations, simply that you would need quite a bit of conductor. What about 3) and 4)?
-Jon
