Power Cable Sizing ^new^ Jun 2026

| Nominal CSA (mm²) | Ampacity (A) – clipped direct | VD per A·km (3-ph, cosφ=0.8) | Approx short-circuit kA·s (k=143) | |-------------------|-------------------------------|-------------------------------|------------------------------------| | 1.5 | 19.5 | 23 | 0.046 | | 2.5 | 27 | 14 | 0.128 | | 4 | 36 | 8.6 | 0.327 | | 6 | 46 | 5.7 | 0.736 | | 10 | 63 | 3.4 | 2.04 | | 16 | 85 | 2.1 | 5.23 | | 25 | 112 | 1.3 | 12.8 | | 35 | 138 | 0.94 | 25.0 | | 50 | 168 | 0.68 | 51.1 | | 70 | 213 | 0.47 | 100.2 | | 95 | 258 | 0.34 | 184.4 | | 120 | 299 | 0.27 | 294.5 |

Power cable sizing is a critical engineering task that requires a systematic approach. While software tools are commonly used for complex installations, the engineer must understand the underlying physics: power cable sizing

| Parameter | Symbol | Typical values / notes | |-----------|--------|------------------------| | Load current (steady) | (I_b) | Based on connected load & diversity | | Cable length | (L) | One-way length (m) | | Supply voltage | (U_n) | 230V, 400V, 11kV, etc. | | System type | - | Single-phase, 3-phase, DC | | Insulation material | - | PVC (70–75°C), XLPE (90°C), EPR (90°C) | | Installation method | - | In air (clipped, tray), buried, conduit, cable ladder | | Ambient temperature | (\theta_a) | 30°C (air) or 25°C (ground typical, varies) | | Soil thermal resistivity | (R_g) | 2.5 K·m/W (typical dry), 1.0 (wet) | | Grouping | - | Number of circuits touching/spaced | | Short-circuit level | (I_sc) | kA at cable point | | Nominal CSA (mm²) | Ampacity (A) –