Earthing Repack | Ss 551 Code Of Practice For

Used in substations or areas with rocky terrain where driving deep rods is impractical.

SS 551 provides two methods for sizing protective conductors (PE):

Before diving into clauses, it is vital to understand the three primary functions of an earthing system as defined by SS 551:

An earthing system is only effective if it remains intact. SS 551 emphasizes the importance of: ss 551 code of practice for earthing

| Test | Method | Acceptance Criteria | |------|--------|----------------------| | | 3-terminal or 4-terminal fall-of-potential method | ≤ design value (typically ≤ 1 Ω for LV supplies) | | Earth fault loop impedance (Zs) | Loop impedance tester at furthest point | Zs ≤ 0.8 × (Uo / Ia) where Ia = operating current of protective device | | Continuity of protective conductors | Low-resistance ohmmeter (200 mA – 10 A) | R ≤ 0.1 Ω (typical for short bonding runs) | | Touch voltage measurement | Voltmeter between exposed conductive part and reference earth | ≤ 50 V AC | | RCD testing | Dedicated RCD tester | Tripping time ≤ 300 ms (general); ≤ 40 ms for 30 mA RCD) |

SS 551 classifies earthing systems using standardized notation (First letter: Source earthing; Second letter: Installation earthing). The most common configuration in Singapore is the system.

: Annual testing of earth resistance is generally recommended to ensure values remain within safe limits. Used in substations or areas with rocky terrain

Copper-clad steel rods driven vertically into the ground. These are highly popular due to ease of installation. They can be deeply driven and coupled together to reach low-resistivity water tables.

Mandatory for all licensed electrical installations in Singapore. Recommended as a reference for tropical countries (Malaysia, Indonesia, Thailand) lacking their own detailed earthing code.

Where:

For engineers and contractors executing projects in Singapore, ensuring compliance with SS 551 involves adhering to this fundamental workflow:

A critical safety mandate within SS 551 is the implementation of Main Equipotential Bonding. Simply grounding electrical equipment is insufficient if adjacent metal structures remain floating.