myElectrical Engineering Ltd.

Cable fault withstand is measured in fault Amperes squared, multiplied by the duration: A²S. This is calculated by the application for your cable.  

When you enter the fault level and duration, the fault A²S is calculated and compared to the maximum allowable by the cable.  You should enter the actual expected fault level and expected maximum duration.

If you have an A²S level (not fault kA and duration), you can use this by setting the duration to a value (say 0.2) and calculating the equivalent kA by taking the square root of the A²S divided by the duration.

For example, if your let though energy is 5x10⁶  A²S, this is equivalent to √ (5x10⁶ /0.02) = 15.8 kA for 0.02 seconds.