Molded case circuit breakers are a type of electrical protection device that is commonly used when load currents exceed the capabilities of miniature circuit breakers. They are also used in applications of any current rating that require adjustable trip settings, which are not available in plug-in circuit breakers and MCBs.
Any electrical network needs protection against over currents - currents whose strength exceeds the working value of the electrical circuit. They occur as a result of a short circuit or overload and can damage circuit elements or cause a fire to the insulation of the conductors.
However, in some countries, notably France and Italy, the air circuit breakerwas developed and used for systems up to 15 kV, but in general, its use is restricted to low voltage applications or high security installations where the risk of an oil fire or oil contamination of the environment is too high to be tolerated.