Significance and Main components of switchgear

main components of switchgear

Significance of switchgear

We all have seen MCB and fuse in our home. A fuse uses to protect equipment against overload and short circuit. These type of protecting devices are necessary for the electric circuit. Switchgear is a general term which includes a wide range of equipment concerned with protection.

The equipment uses in the protection of power system, that equipment denotes as switchgear. It includes circuit breaker, switches, MCB, isolator, CT, PT, fuse, relays, control panel etc.

Main components of switchgear

  1. Circuit breaker
  2. Isolator
  3. Earth switch
  4. Fuses

1) Circuit breaker

A circuit breaker is a mechanical switch. Circuit breaker design to protect equipment or system or particular electrical circuit from damage caused by the excess current. The excess amount of current produced by the overload or short circuit. The basic function of the circuit breaker is to break the electrical circuit in case of abnormal conditions like fault and overload. In normal condition, the circuit breaker allows flowing the current.

circuit breaker

2) Isolator

The isolator is a mechanical switch and it is also known as a disconnect switch. The isolator uses to disconnect a system or part of the system. This switch operates under a no-load condition. In loading condition, when current is flowing through the system, in this case, the isolator cannot operate.

Generally, it connected at both the ends of the circuit breaker. This provides a confirmation that the conductors have been opened. The isolators are slow speed device. Therefore, this device is not used for the current interruption. This device designed to carry load current continuously.

The operation of isolator can be designed for vertical and horizontal operation. Several connections of isolators are available.

  1. Vertical break
  2. Double side break
  3. Single side break
  4. Pantograph (vertical reach)
  5. Centre break


3) Earthing switch

Earthing switch place between the line conductor and earth. It is a mechanical device. Normally it is open. When the line is disconnected, the earthing switch is closed. By this way, it discharges the trapped electrical charges and capacitance to the earth. It is able to withstand currents for a specified time under abnormal conditions. But it not require to carry normal service current. The earthing switch is mounted on the frame of the disconnect switch.

The sequence of operation while opening

  • Open circuit breaker
  • Open isolator
  • Close earthing switch

The sequence of operation while opening

  • Firstly, Open earthing switch
  • Close isolator
  • Close circuit breaker

4) Fuses

A fuse is a current interrupting device. When the current exceeds a certain predefined value, it opens circuit by fusing the element. It uses for the overload and short circuit protection in medium voltage and low voltage application. The fuse operates due to the heating effect of current. Therefore, It requires replacement after every operation.


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