Types of Circuit Breaker Mounting:

There are four types of circuit breaker mounting, which are described below:

Cubicle Type or Cellular Type: In this type of mountings the circuit breakers and their ancillary equipment are mounted in individual chambers or cells made of slate marble or concrete with doors of sheet steel or in a completely sheet steel cubicles. In this arrangement complete isolation of the cell or cubicle from bus-bars may be obtained. Every part in the cell is accessible and any visible fault can be traced out easily but is not very safe.

Truck Type: In this types of circuit breaker mounting the circuit breaker and its auxiliaries are mounted on the movable truck, which is maintained in a masonry cell and can be withdrawn from the cubicle for maintenance and repairs purposes. On the two walls of the cells are fitted two sockets. Shutters must be arranged automatically to cover the live sockets whenever the truck is taken out, and the truck must be locked in position whenever the circuit breaker is closed. This type is suitable up to voltage of 11 kV and a short-circuit rating of 250 MVA.

Metal-Clad Type: In this case each and every live part of the switchgear is completely enclosed in metallic enclosures which are earthed. The enclosures are air, oil or compound filled. It provides proper safety, protects the switchgear from the ingress of dirt and dust from outside and reduces the space occupied to minimum. The circuit breaker can be moved away from the bus-bars either horizontally or between the guides provided by this purpose after disconnecting from live parts. This type is suitable up to voltage of 66 kV and a short-circuit rating of 1,000 MVA.

Open Type: For the largest ratings, it is economical to install the circuit breakers in open to avoid building costs. Bulk oil, low oil content and air blast circuit breakers are mainly used for outdoor installations. In some cases it is found economical to install open type switchgear in a building, the switchgear in this case being of low oil content type.

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