Classification of Circuit Breakers

 Classification of Circuit Breakers

There are quite a few ways to classify the circuit breakers. However, the most general way of classification is on the basis of medium used for the arc extinction.

1. Based on Voltage : 

On the basis of the voltage levels for which they are used, the circuit breakers are classified as listed in table (with corresponding voltage ranges of use).

Category                                                    Range of Voltage
Low voltage                                                   Less than 1 kV
Medium voltage                                              1 kV to 52 kV
High/Extra High voltage                                   66 kV to 765 kV
Ultra High voltage                                         Above 765 kV

2. Based on Location : 

Circuit breakers are, based upon where they are located, classified as, indoor and outdoor types.

Medium and low voltage breakers are categorized as Indoor circuit breakers, whereas the circuit breakers which have air as external insulating medium are classified as outdoor circuit breakers.

3. Based on External Design : 

Outdoor circuit breakers can be identified as either dead tank or live tank type circuit breakers, from the point of view of their physical structural design.

In the dead tank circuit breakers, the switching device is located, with suitable insulator supports, inside a metallic vessel at ground potential and filled with insulating medium. In dead tank circuit breakers, the incoming and outgoing conductors are taken out through suitable insulator bushings, and low voltage type current transformers are located at lower end of both insulator bushings, i.e. at the line side and the load side.

In live tank circuit breakers, the interrupter is located I an insulator bushing, at a potential above ground potential. The live tank circuit breakers are cheaper (with no current transformer), and require less mounting space.

4. Based on Interrupting Media : 

The interrupting media has been a vital factor in the evolution of circuit breakers. It dedicates the overall design parameters of the breaker. The choice of air and oil, as the interrupting media, was predominant till late 70s. but today, vacuum and SF6 are the only dominant interrupting technologies, for medium and high voltage segments of circuit breaker design respectively. The medium used for the arc extinction can be:

- Oil
- Air
- Vacuum
- Sulphur Hexafluoride (SF6)