Earthing Cable Size Calculator May 2026

| 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.

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. earthing cable size calculator

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