The apparatus used for switching, controlling and protecting the electrical circuits and equipment is known as switchgear. It protects the power system from harm during fault conditions and ensures maximum continuity of supply. It switches on or off generators, transmission lines, distributors and other equipments under both normal and abnormal conditions.

It consists of switches, fuses, circuit breakers and relays etc. During normal operation switchgear permits to switch on or off equipments and during faulty conditions it detects the fault and disconnects the unhealthy section from the system.

A switch with ordinary fuse is the simplest form of switchgear and is used to control and protect lights and other equipments in homes. But such means of control presents two disadvantages. Firstly when fuse blows out it take time to restore supply. Secondly fuse cannot successfully interrupt heavy fault currents on modern high voltage and large capacity circuits. So use of switches and fuses are limited to low voltage and small capacity circuits and a dependable means of control such as circuit breakers are used on high voltage system (3.3kV).

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