Earthing Arrangements and Protective Conductors

Earthing Arrangements and Protective Conductors Points : Earthing Arrangements and Protective Conductors, Connections to Earth, Earthing Arrangements, General Every means of earthing and every protective conductor shall be selected and erected so as to satisfy the requirements of these Regulations for the safety and proper functioning of the associated equipment of the installation. The earthing system of the installation may be subdivided, in which case each part thus divided shall comply with the requirements of the chapter. Connections to Earth Earthing Arrangements The consumer’s main earthing terminal shall be connected to Earth by one of the methods described in Regulations 542-2 to 542-5 as appropriate to the type of system of which ,the installation is to form part (see section 312) and in compliance with Regulations 542-6 to 542-8. The consumer’s main earthing terminal shall be consumer’s main earthing terminal shall be connected to the earthed point of the source of energy. Note The supply undertaking’s lines and equipment may form Part of the connection. For TN-CS systems, where Protective Multiple Earthing is provided by the supply underrating, means shall be provided for the-consumer’s main earthing terminal to be connected by the supply underrating to the neutral of the source of energy. For TT and IT systems, the consumer’s main earthing terminal shall be connected via an earthing conductor to an earth electrode complying with Regulations. For TN-C systems where the consumer’s installation comprises earthed concentric wiring or another system of PEN conductors, the external conductor or PEN conductor shall be connected to the consumer’s main earthing terminal. Where the supply is obtained from a privately owned transformer or converter, the main earthing terminal to be connected by the supply underrating to the neutral of the supply. The earihing arrangements may be used jointly or separately for protective or functional purposes according to the requirements of the installation. The earthing arrangements shall be such that:

(i) The value of resistance from the consumer’s main earthing terminal to the earthed point of the supply for TN systems, or to Earth for TT and IT systems, is in accordance with the protective and functional requirements of the installation, and expected to be continuously effective, and

(ii) Earth fault currents and earth leakage currents likely to occur are carried without danger, particularly from thermal, thermo-mechanical and electromechanical stresses, and

(iii) They are adequately robust or have additional mechanical protection appropriate to the assessed conditions of external influence.

Precautions shall be taken against the risk of damage in other metallic parts through electrolysis. Where a number of installations have separate earthing arrangements, any protective conductor running between any two of the separate installations shall either be capable of anything the maximum fault likely to flow through it on the earthed within our installation only and insulation from the earthing arrangements of any other installation. In the latter circumstances, if the protective conductor forms part of a cable the protective conductor shall be earthed only in the installation containing the associated protective device.