Earthing Cable Size Calculator Best May 2026

Selecting the correct earthing conductor size is not arbitrary—it is a critical calculation governed by international standards. An automates this process, applying formulas from standards such as IEC 60364-5-54 or BS 7671 (UK) and NEC Table 250.66 (US) to determine the minimum safe cross-sectional area (in mm² or AWG/kcmil). Core Principle: Thermal Capacity The fundamental requirement for an earthing conductor is that it must survive the fault current without overheating or melting before the protective device operates.

| 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. earthing cable size calculator

( S = \frac\sqrt15000^2 \times 0.1143 ) ( S = \frac15000 \times 0.316143 ) ( S = \frac4743143 \approx 33.2 \text mm^2 ) Selecting the correct earthing conductor size is not

The key formula (from IEC 60364-5-54, clause 543.1.2) is: Find the minimum size