Which oil is used in minimum oil circuit breaker?
It is also known as a minimum oil circuit breaker or live tank circuit breaker. In a minimum oil circuit breaker very small quantity of insulating oil is used in the arc extinguishing chamber. For insulation purposes, different insulating materials like porcelain, bakelised paper, glass-fiber, etc. are used.
What is minimum oil circuit breaker?
Minimum Oil Circuit Breaker or MOCB However, unlike bulk oil circuit breaker, a minimum oil circuit breaker places the interrupting unit in insulating chamber at live potential. The insulating oil is available only in interrupting chamber.
What makes the difference between minimum oil and bulk oil circuit breaker?
In this type of circuit breaker minimum oil is used as an arc quenching medium and it is mounted on a porcelain insulator to insulate it from the earth. Minimum oil circuit breaker requires less space as compared to bulk oil circuit breaker which is an important feature in large installations.
Why frequent maintenance is needed in the minimum oil circuit breakers?
Maintenance of oil circuit breaker Also, the dielectric oil gets carbonized in the area of the contacts, thereby losing its dielectric strength. This results in the reduced breaking capacity of the breaker. Therefore, the maintenance of oil circuit breaker is essential for checking and replacement of oil and contacts.
What is the advantage of low oil circuit breaker?
Arc energy is absorbed in decomposing of oil. The gas formed which is mainly hydrogen, has high diffusion rate and high heat absorption in changing from diatomic to mono-atomic and thus provides good cooling properties.
Which is to be checked periodically is an oil circuit breaker?
Hence proper maintenance of an oil circuit breaker consists of following checkpoints. Regularly check the contacts and the dielectric strength of the oil (for every 3 to 6 months). The tripping and the closing circuit should be checked periodically. The insulation must be free from carbon particles.
Why does minimum oil circuit breaker has less volume of oil?
Unlike bulk oil circuit breaker, a minimum oil circuit breaker places the interrupting unit in insulating chamber at live potential. The insulating oil is available only in interrupting chamber. Hence oil requirement will be less and hence MOCB has less volume of oil.
Which circuit breaker is used less oil to extinguish arc?
Minimum Oil Circuit Breaker It uses less space as compared with bulk oil type. It is not used where the repeated operation is necessary. The main benefits of this circuit breaker are, it uses less oil, less space, less weight, tank size is small, less maintenance, etc.
What is the major disadvantage of using oil circuit breakers for indoor installations?
Oil may be flammable and can cause fire hazards, if a defective oil circuit breaker should fail under pressure and cause an explosion. There is a risk of formation of explosive mixture with the air.
What oil goes in a circuit breaker?
An oil circuit breaker is one kind of circuit breaker where the insulating oil can be used as an arc quenching medium. Once the fault occurs within the system, then circuit breaker contacts will be separated and the arc will be struck among the contacts.
What are the advantages and disadvantages of SF6 breakers?
Advantages of SF6 circuit breaker: Their decomposition products are on explosive ad hence there is the risk of fire or explosion. Electric clearance is very much reduced because of the high electric strength of SF6. Its performance is not affected due to variations in atmospheric conditions.
Why do you need a minimum oil circuit breaker?
When the moving contact moves downwards, it forces the insulating oil to enter into the arc control devices . Thus, the arc gets extinguished. Minimum oil circuit breaker requires less space as compared to bulk oil circuit breaker which is an important feature in large installations.
How does an oil circuit breaker work in a transformer?
Oil filling plugs. The construction of an oil circuit breaker is simple. It involves sinking the fixed and movable contacts of the breaker into a metal tank containing the transformer oil. The oil serves both as an insulator and as a medium for arc quenching.
What are the different types of circuit breakers?
There are two major types of oil circuit breakers, they include: Bulk Oil Circuit Breaker (BOCB). For bulk oil circuit breakers, the oil serves two purposes. It serves as an arc quenching medium, and an insulator to the current-carrying contacts and earth parts of the breaker.
How does the arc work in a circuit breaker?
The arc causes a release of much energy that increases the temperature of the oil, turning them into gas. The high-pressure gas surrounds the arc and its volatile bubbles displace the oil, pushing apart the contacts. Hydrogen gas formed during arc separation helps in cooling the system.
How is a minimum oil circuit breaker different from a bulk circuit breaker?
However, unlike bulk oil circuit breaker, a minimum oil circuit breaker places the interrupting unit in insulating chamber at live potential. The insulating oil is available only in interrupting chamber. The features of designing MOCB is to reduce requirement of oil, and hence these breaker are called minimum oil circuit breaker. 15 August 2015 10
What causes reignition in an oil circuit breaker?
Reignition happens when therestriking voltage of the system causes a renewed formation of the arc, (after completion of the first interruption) and continuation of flow of current. The arcing chamber designs are either of the axial or radial venting type. Often, a combination of both are used in the design of minimum oil, MV CB’s.
How do you repair an oil circuit breaker?
To repair an oil leaking circuit breaker, find the leaking point, which may be the bushing or the drain valves. Repair it using the drill and injection method, custom design enclosures, or the clamp injection method with a rubber-based, non-adhering sealant to repair the breaker.
How does arc quenching in bulk oil circuit breaker work?
• The arc quenching in bulk oil circuit breaker takes place when current passes through zero crossing. • As the gas bubble is enclosed by the oil inside the totally air tight vessel, the oil surround it will apply high pressure on the bubble, which results highly compressed gas around the arc.