Oil Circuit Breaker

In this type of circuit breaker oil is used, but mineral oil is preferable. It acts better insulating property than air. The moving contact and fixed contact are immerged inside the insulating oil. When the separation of current takes place, then carrier contacts in the oil, the arc in circuit breaker is initialized at the moment of separation of contacts, and because of this arc in the oil is vaporized and decomposed in hydrogen gas and finally creates a hydrogen bubble around the arc.

This highly compressed gas bubble around and arc prevents re-striking of the arc after current reaches zero crossing of the cycle. The OCB is the oldest type of circuit breakers

Minimum Oil Circuit Breaker

It is a circuit breaker which utilizes oil as the interrupting media. The minimum oil circuit breaker will place the interrupting unit in an insulating chamber at the live potential. But insulating material is available in interrupting chamber. It requires less amount of oil so it is called as minimum oil circuit breaker.

Advantages

It requires less maintenance.

It is suitable for both automatic operation and manual.

It requires smaller space

The cost for breaking capacity in MVA is also less.

Disadvantages

Oil deteriorates because of carbonization.

There is a possibility of explosion and fire

As it has a smaller quantity of oil, so carbonization increases.

It is very difficult to remove gases from the space between the contacts.