3.1 - Introduction

Electrical installations must be protected from the effects of short circuit and over-load. In addition, the people using the installations, as well as the buildings containing them, must be protected from the effects of fire and of other hazards arising from faults or from misuse.

Not only must automatic fault protection of this kind be provided, but an installation must also have switching and isolation which can be used to control it in normal operation, in the event of emergency, and when maintenance is necessary.

This Chapter will consider those regulations which deal with the disconnection of circuits, by both manual and automatic means, the latter in the event of shock, short circuit or overload. It does not include the Regulations which concern automatic disconnection in the event of an earth fault: these are considered in {Chapter 5}.

In order that anyone operating or testing the installation has full information concerning it, a diagram or chart must be provided at the mains position showing the number of points and the size and type of cables for each circuit, the method of providing protection from direct contact (see {3.4.5}) and details of any circuit in which there is equipment, such as passive infra-red detectors or electronic fluorescent starters, vulnerable to the high voltage used for insulation testing.