In the realm of electrical engineering and building safety, the primary objective of any electrical installation is to prevent hazards such as electric shock, fire, and equipment damage. At the heart of this safety infrastructure lies proper earthing (or grounding) and bonding. For professionals operating in Singapore and adopting similar international guidelines, serves as the foundational, authoritative standard .
The neutral is earthed at the source, but the exposed conductive parts are earthed locally at the installation, independent of the source earth. This is common in rural areas or temporary supplies.
The effectiveness of any earthing system hinges on the electrical resistivity of the surrounding soil. SS 551 outlines methodology for site assessments and calculations:
[ R_A \times I_\Delta n \leq 50 , \textV ] ss 551 code of practice for earthing
Installations must be tested at regular intervals as mandated by the Energy Market Authority (EMA) and guided by SS 551.
| Phase conductor cross-section (mm²) | Minimum PE cross-section (mm²) | |--------------------------------------|--------------------------------| | ≤ 16 | Same as phase | | 25 – 35 | 16 | | > 35 | Half of phase conductor (rounded up) |
| Feature | SS 551 | BS 7430 | IEC 60364-4-44 | |---------|--------|---------|----------------| | Max touch voltage (general) | 50 V | 50 V | 50 V | | Preferred electrode material | Copper-bonded steel | Copper, steel, cast iron | Any suitable material | | Earthing conductor min. size (Cu) | 16 mm² | 10 mm² | 6 mm² (if mechanically protected) | | Lightning earth bonding | Mandatory | Mandatory | Not covered | | Soil resistivity testing | Required for > 1000 m² | Recommended | Not specified | In the realm of electrical engineering and building
This article delves deep into the SS 551 standard—what it is, its core principles, and how it ensures the safety and reliability of modern electrical installations. What is SS 551?
Ensure inspection chambers are built to facilitate regular maintenance and testing by LEWs.
To eliminate dangerous voltage differences between metallic parts, SS 551 requires bonding. The neutral is earthed at the source, but
Fulfills statutory requirements and ensures that insurance policies remain valid in the event of an electrical fire or accident. How to Get Started with SS 551
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.
SS 551 outlines strict definitions and structural requirements for the components that comprise an earthing network: 1. Earth Electrodes
: Managing the interface between LV and High Voltage (HV) substations within buildings. Generators
Singapore Standard SS 551:2009 – Code of Practice for Earthing (Reconfirmed 2019)