Earth Cable — Sizing Hot!

[ S = \frac\sqrtI^2 \times tk ]

| Phase Conductor (mm²) | Min. Copper Earth (mm²) – if same material | |-----------------------|---------------------------------------------| | 1.5 | 1.5 | | 2.5 | 2.5 | | 4 | 4 | | 6 | 6 | | 10 | 10 | | 16 | 16 | | 25 | 16 | | 35 | 16 | | 50 | 25 | | 70 | 35 | | 95 | 50 | | 120 | 70 | earth cable sizing

If you’re designing or installing an electrical system, you already know the importance of live and neutral conductors. But the earth cable (protective conductor or grounding conductor) is arguably the most critical wire for safety . It’s the silent guardian—the path that clears a fault and saves lives. [ S = \frac\sqrtI^2 \times tk ] |

But how do you size it correctly? Too small, and it could vaporize under a fault. Too large, and you’re wasting copper. Let’s break down the rules, the math, and the practical steps. When a fault occurs (say, a live wire touches a metal casing), the earth cable must carry the full fault current until the protective device (breaker or fuse) trips. During that short time—milliseconds to a few seconds—the earth wire heats up. It’s the silent guardian—the path that clears a

When in doubt: . The cost of one cable size up is trivial compared to the cost of a failed protection path.