ABSTRACT
The meaning of the word 'protection' as used in the electrical industry is no different from that in everyday usage. People protect their property by the installation of security measures such as locks and/or alarm systems. There are two ways of receiving an electric shock: by contact with intentionally live parts and by contact with conductive parts made live due to a fault. It is obvious that people need to provide protection against both of these conditions. The Health and Safety Executive accepts that a voltage of 63.5 V to earth, three phase, or 55 V to earth, single phase, will give protection against severe electric shock. It must be remembered that the priority of the fuse is to protect the circuit conductors, not the appliance or the user. Calculation of cable size therefore automatic-ally involves the correct selection of protective devices.
