SS 551 Code of Practice for Earthing is a Singapore Standard that provides comprehensive guidance on the design, installation, and maintenance of earthing systems for land-based electrical installations.
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 local soil conditions, lightning density, and safety practices unique to a tropical, high-rainfall, high-lightning-strike region.
Lightning Protection: Integration of the earthing system with lightning protection systems (governed by the SS 555 series). ss 551 code of practice for earthing
You can purchase the full document or view a preview through the Singapore Standards eShop, which is the official distributor for enterprise Singapore standards. SS 551:2022 - Singapore Standards
Example: For a 30 mA RCD, ( R_A \leq 50 / 0.03 = 1666 , \Omega ). But SS 551 recommends keeping below 200 Ω in practice. SS 551 Code of Practice for Earthing is
The primary objective of SS 551 is to ensure that all conductive parts of an electrical installation are connected to the general mass of earth. This creates a low-resistance path for fault currents, achieving three main goals:
Substation Interfaces: Managing the interface between low-voltage (LV) and high-voltage (HV) substations located within buildings. Continuity of protective conductors: Ensure no breaks or
In an era where Singapore is a global hub for data centers, earthing has taken on a new dimension. Modern servers operate at incredibly low voltages and are hypersensitive to "electrical noise"—random fluctuations in voltage that corrupt data.