A Schneider catalogue that I have has a technical section on tripping curves. It discusses a C20 M.C.B. It states that it will interrupt a current of 100 Amps (20 times the rated current) in:
0.45 seconds at least
6 seconds at most.
For tripping currents exceeding 20 times the rated current the time-current curves do not give a sufficiently precise representation. The breaking of high short circuit currents is characterized by the current limiting curves, in peak current and energy.
The total breaking time can be estimated at 5 X the value of the ratio (I2t)/(I)2. Is that I squared t divided by I squared? Just what is that?
Z.