| Installation Type | Recommended Maximum Earth Resistance | |------------------|----------------------------------------| | General LV supply | ≤ 1 Ω (for high fault current systems) | | TT system (with RCD) | ≤ 200 Ω (practical limit for RCD operation) | | Lightning protection (combined earth) | ≤ 10 Ω | | Telecommunications earth | ≤ 1 Ω (often ≤ 0.5 Ω) |
| Feature | SS 551:2018 | BS 7430 (UK) | IEEE 80 (US) | IEC 62305-3 (Lightning) | |----------------|-------------|--------------|--------------|--------------------------| | Step/touch calcs | Mandatory >1 kA | Recommended | Mandatory for substations | Not covered | | Soil testing depth | Up to electrode length | Variable | Up to grid diagonal | Not specified | | Corrosion protection | Moderate (material choice) | Basic | Detailed (incl. coating) | Minimal | | Software requirement | No | No | Yes (for large grids) | No | | Tropical adaptation | High | Low | Low | Moderate | ss 551 code of practice for earthing
The primary objective of SS 551 is to limit the electrical potential of current-carrying conductors and non-current-carrying metalwork to protect human life, animals, and property. System Earthing | Installation Type | Recommended Maximum Earth Resistance
Disclaimer: This content is a summary for educational purposes. For actual design, installation, or compliance auditing, please refer to the full official text of published by Enterprise Singapore. Earthing for medical equipment
SS 551 applies to most land-based installations in and around buildings. However, it explicitly cover: Ships, aircraft, or offshore installations. Earthing for medical equipment.