LEWs typically test commercial and industrial earthing systems annually or biannually as part of licensing requirements to ensure earth loop impedance values remain within safe thresholds. 8. Summary Checklist for SS 551 Compliance
Typically copper-clad steel rods driven vertically into the soil.
SS 551:2022 “Code of practice for earthing” is an essential standard for anyone involved in electrical installations in Singapore. It provides comprehensive guidance on the design, installation, testing, and maintenance of earthing systems, ensuring the safety of people, property, and equipment. ss 551 code of practice for earthing
One of the most emphasized aspects of SS 551 is equipotential bonding. Danger arises when there is a potential difference between two simultaneously accessible conductive parts. The code mandates the bonding of all extraneous conductive parts—such as metallic water pipes, gas lines, structural steelwork, and central heating systems—to the MET. This ensures that the entire facility rises to the same electrical potential during a fault, neutralizing shock hazards. Soil Resistivity and Resistance Calculations
: The central bar or terminal where all protective and functional earthing conductors are interconnected. 3. Major Sections and Design Considerations 2022 revision SS 551:2022 “Code of practice for earthing” is
SS 551 requires the following tests upon completion and periodically thereafter:
: Arrangements for low-voltage standby generators, including star-point switching and neutral earthing transformers. Earth Electrode Systems Danger arises when there is a potential difference
While the specific resistance target depends on the nature of the installation (LV vs. HV), a common rule of thumb for standard low-voltage consumer installations is to achieve an earth electrode resistance of for substations, and generally under 10 Ohms for standard commercial distribution, though lower is always preferred to ensure rapid protective device operation. Electrode Configurations
SS 638:2018+C1/A1:2022 Code of practice for electr... - NLB eResources
| 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) |