Cable Derating Factor May 2026

| Conductor Insulation | 30°C (Base) | 35°C | 40°C | 45°C | 50°C | |----------------------|-------------|------|------|------|------| | 70°C (PVC) | 1.00 | 0.94 | 0.87 | 0.79 | 0.71 | | 90°C (XLPE/EPR) | 1.00 | 0.96 | 0.91 | 0.87 | 0.82 |

(I_derated = 210A \times 0.35 = 73.5A)

| Depth | Factor (up to 10kV) | |-------|---------------------| | 0.5 m | 1.00 | | 0.8 m | 0.96 | | 1.0 m | 0.94 | | 1.5 m | 0.90 | Reduced air density lowers convection cooling.

Note: For high temperatures >55°C, special cables are required. When multiple cables run together, each heats its neighbors.

| Number of circuits/cables | Spacing (touching) | Spacing (≥1 cable diameter) | |---------------------------|--------------------|-----------------------------| | 1 | 1.00 | 1.00 | | 2 | 0.80 | 0.85 | | 3 | 0.70 | 0.80 | | 4-5 | 0.60 | 0.75 | | 6-8 | 0.50 | 0.70 | Standard soil is 1.2 K·m/W (e.g., damp clay). Dry sand or backfill can be >2.5 K·m/W.