CIRCUIT BREAKER TYPES

A circuit breaker is an electrical switch which makes or breaks an electrical circuit during a short circuit fault or overload condition. It comes under the protection of the power system where large amount of fault current hampers the system. In case a fault occurs in any electrical system, the relay senses the fault and sends the message to the circuit breaker which disconnects the circuit from the fault circuit thus protecting the electrical equipments. A circuit breaker can resume its normal operation after the fault has been cleared. A circuit breaker is an important protection device used for the timely disconnection and reconnection of the electrical circuit after the clearance of the large magnitude fault current.

Operating principle:

There are two operating principles under which a circuit breaker works.

Mechanical principle:

There are two contacts present in any circuit breaker- fixed contact and movable contact. Under normal operating condition when the circuit breaker is switched “on”, both the contacts remain connected to each other. There is a stored potential energy in between the contacts in form of any pressure or compressed air which is released only when the switching signal is given. On occurrence of a fault, the contact gets disconnected and this stored potential energy is released in form of kinetic energy thus disconnecting the fault circuit from the healthy one with a greater force.

Electrical principle:

On account of the high faulty power that is carried by the circuit breaker there is a possibility of a dangerously high arc taking place between the fixed and movable contacts during its operation. In order to eliminate this arcing sufficient dielectric strength has to be provided in between the contacts by cooling or compressing the air between the contacts.

Types of circuit breakers, Based on their arc quenching media

·         Oil circuit breaker

·         Gas filled circuit breaker

·         Vacuum circuit breaker

·         SF₆ circuit breaker

Types of circuit breakers Based on their services offered

·         Outdoor circuit breaker

·         Indoor circuit breaker

Types of circuit breakers Based on their mechanism of operation

·         Pneumatic controlled circuit breaker

·         Spring operated circuit breaker

·         Hydraulic circuit breaker

Based on their installation voltage

·         Low voltage circuit breaker

·         Medium voltage circuit breaker

·         High level circuit breaker

Uses of circuit breakers:

Circuit breakers have a vast application in field of power system. They are used in both indoor and outdoor power transfer circuits.

-          Used as plug-in breakers directly connected to the main bus bar for emergency power supply

-          Fire resistance breakers used in the switchboards

-          Used as DSN switches for higher operating capacity in case of high fault power

-          Motor circuit breakers for the reliable operation and protection of motors

-          Circuit breakers are also installed in the panel boards.

-          Used in the switchyards where transmission and distribution of power plays an important role

-          Generally used in lines with high current and voltage ratings