|Electrical Installation Showing Main Protective Bonding|
BS 7671 strictly require that the protective bonding conductors are unbroken and have a resistance that is low enough to satisfy the standard. Protective bonding ensure that when fault occurs in the system, a dangerous potential will not occur between earthed metalwork (exposed conductive parts) and other metallic part of the building. When the protective bonding is visible in the entire location, a visual inspection will be enough. However, most of the installations have embedded wirings which make it difficult for visual inspections. Thus, testing is really necessary.
The purpose of testing protective bonding conductor is to ensure a sufficient earth path, where in the event of a fault the exposed and extraneous conductive parts will have the same potential. That is why it is called ‘equipotential bonding’. In order to achieve this it is recommended that the resistance of the bonding conductors does not exceed 0.05Ω.
BS 7671 provide a recommendation for the maximum length of copper protective bonding conductor.
|Credit: Practical Guide to Inspection, Testing & Certification of Electrical Installations|
- Practical Guide to Inspection, Testing & Certification of Electrical Installations, by: Christopher Kitcher
- City and Guilds
- BS 7671