| Parameter | Description | Example | |-----------|-------------|---------| | | Maximum prospective earth fault current at the point of installation | 10 kA (10,000 A) | | Fault clearing time (t) | Operating time of the upstream overcurrent device (fuse/MCCB) | 0.2 seconds | | Material | Copper (most common), Aluminum, or Galvanized Steel | Copper | | Insulation type | PVC (lower k value), XLPE (higher k value), bare conductor | PVC (k = 143 for Cu) | | Initial & final temperature | Defaults based on standard (e.g., 30°C initial, 160°C final for PVC-insulated Cu) | Embedded in k factor | Step-by-Step Working Example (IEC Method) Scenario: A 415V industrial panel has a prospective earth fault current of 15 kA. The upstream MCCB trips in 0.1 seconds. The earthing conductor is copper with PVC insulation (k = 143). Find the minimum size.
When in doubt, consult the relevant national standard (NEC, IEC, BS 7671, AS/NZS 3000) and consider a safety margin. Correctly sized earthing cables are not merely a regulatory checkbox—they are the last line of defense between a fault and a fatal electric shock. earthing cable size calculator
[ S = \frac\sqrtI^2 \times tk ]