Fault Rating
Check that a conductor can withstand the fault current.
Questions
Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.
What does the fault rating calculator do?
The tool applies the adiabatic check to a conductor. It works out the minimum size for the prospective fault current and the clearing time. It also reports the fault current the entered size can withstand for that time. The check passes when the installed size is at or above the minimum.
Where does the k factor come from?
The k factor comes from AS/NZS 3008.1.2:2017 Table 52. It depends on the conductor material and the insulation type. A failed check cites AS/NZS 3008.1.2:2017 Clause 5.3, which gives the adiabatic equation I²t = K²S². Change the material or the insulation and the k factor changes with it.
Which inputs matter most?
The prospective fault current and the clearing time drive the minimum size. The clearing time must match the device that clears the fault, not the downstream device. Material and insulation set the k factor. Cables in parallel are treated as one conductor of the combined cross section.
What does this check not cover?
The adiabatic method assumes that no heat leaves the conductor during the fault. It does not check the current rating, the voltage drop or the loop impedance. Use the cable size tool for those checks. The inputs sit in the page address, so a link reproduces the same check.