Corrosion is one of the most significant threats to the long-term integrity of earthing systems. Buried earth electrodes and earthing conductors are exposed to varying soil conditions that can cause deterioration over time, leading to increased earth resistance and potential system failure.
SS 551 is the definitive Singaporean guide for the design, installation, verification, and maintenance of earthing systems in electrical installations (typically up to 66 kV, though principles apply beyond). Unlike the more prescriptive BS 7671 (IET Wiring Regulations) which Singapore also references, SS 551 focuses specifically on , lightning density , and safety practices unique to a tropical, high-rainfall, high-lightning-strike region.
Stabilizing voltage levels relative to earth during normal operation and transient events.
This refers to connecting all non-current-carrying metal parts of an installation (such as switchboard enclosures, cable trays, conduits, and motor frames) to the earth electrode. If an internal wire chaffs and touches a metal enclosure, the current flows straight to earth instead of passing through a human operator. Principles of Equipotential Bonding ss 551 code of practice for earthing
The effectiveness of any earth electrode depends heavily on the surrounding soil. SS 551 emphasizes performing a soil resistivity test (typically using the Wenner Four-Pin Method) before final design. Soil moisture, temperature, and chemical composition directly dictate the required depth and number of earth rods. Touch and Step Voltages
Copper or galvanized iron plates buried vertically.
a) Protective earthing of low voltage installations to SS 638 (the Singapore Code of Practice for Electrical Installations); Corrosion is one of the most significant threats
Adhering to is not just a matter of following the law—it is a fundamental commitment to safety. By implementing the rigorous standards for earthing and bonding outlined in this code, professionals ensure that Singapore’s electrical infrastructure remains resilient against faults and lightning alike.
The (formerly known as CP 16) is Singapore's national standard governing the design, installation, testing, and maintenance of electrical earthing systems. Earthing—often referred to as grounding—is the fundamental safety mechanism that protects human life, safeguards electrical equipment, and ensures power system stability.
Protects occupants, maintenance personnel, and the public from lethal electric shocks. Unlike the more prescriptive BS 7671 (IET Wiring
Guidance on managing high-magnitude fault currents and the design of earth grids in substations.
Earthing is the process of connecting the exposed conductive parts of an electrical installation to the general mass of the earth via a low-impedance path. SS 551 outlines several fundamental reasons why this is critical:
Dissipates transient overvoltages, lighting surges, and fault currents safely into the ground.
The performance of any earth electrode depends heavily on soil resistivity (