| Altitude (m) | Approx. Factor | | :--- | :--- | | 0 – 2,000 | 1.00 | | 2,000 – 3,000 | 0.96 | | 3,000 – 4,000 | 0.92 | | > 4,000 | Engineering judgment |
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. cable rating and derating factor
Derate by 1% to 2% per 300 meters above 2,000m. | Altitude (m) | Approx