Module is called Ampacity. I just checked. You can even use it in DEMO version, but cannot print report.
Its based on round conductors, but you can just use the rectangular and match the required area.

This is a sample report from it (I just keyed in some data, for illustration):

Minimum Conductor Size:
62.7609 MCM
31.7938 sq. mm
0.1252 in (radius)
3.1813 mm (radius)


Input Data:

Symmetrical RMS Current Magnitude: 12 kA

Maximum Fault Duration: 0.5 s

Ambient Temperature: 35 °C

Maximum Allowable Temperature: 1083.0000 °C (fusing temperature)

Conductor Type: Copper, annealed soft drawn (100% conductivity)

Decrement Factor: 1.0618
X/R: 20
Frequency 50 (Hz):


Material Constants of Conductor:

Name: Copper, annealed soft drawn (100% conductivity)

Reference Temperature for Material Constants: 20.0000 °C

Thermal Coefficient of Resistivity at Reference Temperature: 0.00393 1/°C

Fusing Temperature of Conductor: 1083.0000 72

Resistivity of Conductor at Reference Temperature: 1.7200 mW×cm

Thermal Capacity per Unit Volume: 3.4200 J/cm³ · °C