Earthing — Ss 551 Code Of Practice For

The SS 551:2022 Code of Practice for Earthing is the current Singapore Standard governing the design, installation, and maintenance of earthing systems for land-based electrical installations. Key Overview

TN-C-S (PME – Protective Multiple Earthing)

• PEN conductor from transformer to the building, then split into separate PE and N.
• The PEN conductor is earthed at multiple points.
• Widely used in residential estates.
• Caution per SS 551: PME should not be used for EV charging points or swimming pools without additional risk assessment.

This is the physical conductor (usually copper rods or mats) driven into the soil. SS 551 specifies the materials and depths required to achieve the desired Earth Resistance value, typically keeping it below 1 Ohm for major installations. Main Earthing Terminal (MET) ss 551 code of practice for earthing

Typical Earth Resistance Targets:

| 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) | The SS 551:2022 Code of Practice for Earthing

Simplified Requirements:

Whether you are an electrical contractor, a licensed electrical worker (LEW), or a facility manager, understanding SS 551 is critical for regulatory compliance and operational safety. 1. What is SS 551? PEN conductor from transformer to the building, then

Every installation must have a central point where all earthing conductors are connected. This terminal allows for easy testing and ensures all metalwork in the building is at the same potential. Equipotential Bonding