Trying a 240mm² cable (base rating ~ 450A): $450A \times 0.326 = 146.7A$ (Still slightly low).
The 50mm² cable rated for 185A can only safely carry 60 Amps in these real conditions. It is entirely insufficient for a 150A load. cable rating and derating factor
Derate by 1% to 2% per 300 meters above 2,000m. Trying a 240mm² cable (base rating ~ 450A): $450A \times 0
Use thermal backfill (sand/cement mix) to lower resistivity. 4. Altitude Derating ($K_alt$) The Physics: At high altitudes, air density is lower. Less air means less convective cooling. For cables in air (not buried), above 2,000 meters (6,500 ft), you must derate. Derate by 1% to 2% per 300 meters above 2,000m
Note: Altitude affects air cooling but NOT buried cables. The Physics: Non-linear loads (VFDs, computers, rectifiers) generate harmonic currents. Triplen harmonics (3rd, 9th, 15th) add in the neutral conductor, causing overheating even if phase currents are balanced.
The NEC uses a formula based on conductor temperature rating.
Running a 90°C XLPE cable through a 70°C boiler room reduces its capacity by 42%. A 100A cable becomes a 58A cable. 2. Grouping / Bundling Derating ($K_group$) The Physics: When cables are tied together in a tray, conduit, or bundle, they heat each other. The inner cables cannot radiate heat outward.