Protective equipotential bonding

Fault protection is protection against electric shock rmder single fault conditions and is provided by protective equipotential bonding and automatic disconnection of the supply (by a fuse or MCB) in accordance with lEE Regulations 411.3 to 6. 

Protective equipotential bonding is equipotential bonding for the purpose of safety. 

In Chapter 13 of the lEE Regulations we are told that where the metalwork of electrical equipment may become charged with electricity in such a manner as to cause danger, that metalwork will be connected with earth so as to discharge the electrical energy without danger. The application of protective equipotential bonding is one of the important principles for safety. 

The method which is most universally used in the United Kingdom is, therefore. Method 1 - protective equipotential bonding coupled with automatic disconnection of the supply. 

The object of the test is to ensure that the CPC is correctly connected, is electrically sound and has a total resistance which is low enough to permit the overcurrent protective device to operate within the disconnection time requirements of Regulation 411.4.6, should an earth fault occur. Every protective conductor must be separately tested from the consumer s main protective earthing terminal to verify that it is electrically soimd and correctly connected, including the protective equipotential bonding conductors and supplementary bonding conductors. 

Disconnect the installation protective equipotential bonding from the earth electrode to ensure that the test current passes only through the earth electrode. 

Rgure 5.14 Cable Sheath Earth Supplies (TN-S System) Showing earthing and main protective equipotential bonding arrangements. 

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