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.
This is non-negotiable under SS 551. All extraneous conductive parts entering the building must be bonded to the Main Earthing Terminal (MET). ss 551 code of practice for earthing
Extraneous parts include:
Bonding conductor size: Minimum 6 mm² copper (typically 10 mm² used for robustness). The neutral is earthed at the source, but
SS 551 was first published by Enterprise Singapore (formerly SPRING Singapore) to harmonize local earthing practices with international best practices, particularly the IEC 60364 series. Over the years, it has undergone several revisions to address emerging challenges such as increased renewable energy integration, sensitive electronic loads, and electromagnetic compatibility (EMC). Bonding conductor size: Minimum 6 mm² copper (typically
The latest version, SS 551:2018, supersedes previous editions and aligns closely with IEC 60364-4-44 and IEC 60364-5-54, ensuring that Singapore’s earthing standards remain compatible with global electrical infrastructure.