. Main protective bonding for gas or water pipes typically requires at least .
: The disconnection time of the protective device (breaker or fuse) in seconds.
The primary purpose of an earthing cable is to provide a low-impedance path for fault current.
If the phase conductor is Aluminum, the earth conductor is typically sized based on the equivalent copper current-carrying capacity, or calculated specifically to maintain impedance levels. how to select earthing cable size
According to IEC 60364-4-41 and BS 7671, the minimum cross-sectional area for the earth conductor is:
$$S = \frac\sqrt10,000^2 \times 0.1143 = \frac\sqrt10,000,000143 = \frac3162143 \approx 22.1 \text mm^2$$
Check the size of the live cables (L1, L2, L3, and Neutral) you are installing. The primary purpose of an earthing cable is
| Phase conductor area (mm²) | Min. copper earthing conductor (mm²) | |----------------------------|---------------------------------------| | ≤ 16 | Same as phase conductor | | 25 – 35 | 16 mm² | | 50 – 95 | 25 mm² | | 120 – 150 | 35 mm² | | 185 – 240 | 50 mm² | | ≥ 300 | 70 mm² |
If phase conductors are run in parallel, the total phase area is the sum of the individual cables. The earth conductor size must be calculated based on the total fault current capability of the circuit, not just one cable.
[ S = \frac\sqrtI^2 \times tk ]
For specific engineering projects, or when the earth cable is not the same material as the phase cable, you must use the . This formula verifies that the cable can withstand the thermal energy of a fault.
Three main factors determine the size of the earth cable: