Types Of Circuit Breaker

There are many cases of mishaps in the electrical and electronics industries. This will lead to severe damage to buildings, offices, homes, schools, and industries. Current and voltage cannot be trusted, despite safety measures being taken. If circuit breakers are installed, they will control sudden voltage and current increases. 

They will protect against accidents. Electrical circuit breakers serve as the heart of a building. According to the system’s rating, different types of circuit breakers are installed. Circuit breakers are used in houses and industries. Different types of circuit breakers are used in the house and industries. We will discuss the different types of circuit breakers and their importance.

Precisely what is a circuit breaker?

An electrical circuit breaker is a switching device that can be used automatically or manually to protect and control an electrical power system. In the modern power system, the design of the circuit breaker has changed in response to the vast currents and to prevent the formation of an arc.

Whether it is the houses, offices, schools, industries, or any other place, the electricity that comes from the power distribution grids forms a large circuit. Those lines connected to a power plant at one end are called the hot wire, while the lines connecting to the ground are called the ground wire. 

Whenever electrical charge flows between these two lines, potential develops between them. During the complete circuit, the connection of loads (appliances) provides resistance to the flow of charge, and the whole electrical system inside the house or industry will operate smoothly.

So long as the appliances are sufficiently resistant and do not cause overcurrents or voltages, they will work smoothly. Too much current flowing through the circuit or short-circuiting or sudden connections of the hot wire to the ground wire could cause the wires to heat up, resulting in a fire. Such situations are prevented by the circuit breaker, which cuts off the remaining circuit.

What makes a circuit breaker crucial?

Any particular circuit breaker in the home has only two functions: safeguarding the power lines and maintaining your safety. When the wires in your home (or in a specific zone of your home) are overwhelmed with electrical current and begin to heat it up, that safeguard takes place.

Types of Circuit Breakers

The different types of high voltage circuit breakers include the following

The air circuit breaker

The circuit breaker will operate in the air; the quench medium will be an Arc at atmospheric pressure. There are many countries where an oil circuit breaker is used instead of an air circuit breaker. We will discuss an oil circuit breaker towards the end of this article. In light of this, using an air circuit breaker up to 15KV is still the preferred option. As a result, using a 15V oil circuit breaker may cause a fire.

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The SF6 Circuit Breaker

An SF6 circuit breaker is a current-carrying contact device that operates in sulfur hexafluoride gas. This material has excellent insulating properties and high electro-negativity. That makes sense since free electrons have a high affinity for absorption. The negative ion is formed when a free electron collides with the SF6 gas molecule and is absorbed. 

The negative ions formed will be much heavier than an electron. Because of this, SF6 has a much lower overall mobility of charged particles than other common gases. Among the significant factors responsible for conducting current through a gas is the mobility of charged particles. SF6 gas acquires a very high dielectric strength for heavier and less mobile charged particles. 

Low gas viscosity provides the gas with good heat transfer properties. The effectiveness of SF6 in quenching arcs is 100 times greater than that of an air circuit breaker. The voltage ranges from 33KV to 800KV, and it is used for medium and high voltage power systems.

The Vacuum Circuit Breaker

Circuit breakers that use a vacuum to extinguish an arc are called vacuum circuit breakers. Its dielectric recovery capability has excellent interruption properties and can interrupt both the line frequency current and the high-frequency current, which is caused by arc instability.

Under normal operating conditions, two electrodes will remain closed on the VCB. Assume that when a fault occurs in any part of the system, the trip coil of the circuit breaker becomes energized, and the contact becomes detached.

An arc forms between the contacts of the breaker when the contacts are open in a vacuum, i.e., 10-7 to 10-5 Torr, due to the ionization of the metal vapors on the contacts. Due to the rapid condensing of electrons, vapors, and ions produced during the arc, it quickly extinguishes. The CB contacts quickly recover their dielectric strength after extinguishing the arc.

The Oil Circuit Breaker

Circuit breakers are typically lubricated with breaker oil, but mineral oil is preferred. Mineral oil acts as a better insulator than air. In the insulating oil, the moving contact and fixed contact are immersed. After the current is separated, the carrier contacts in the oil are separated, and the arc in the circuit breaker is initiated; due to this, the arc in the oil is vaporized and decomposed in hydrogen gas, resulting in a hydrogen bubble around the arc.

This highly compressed gas bubble around the arc prevents it from striking again after the current has reached zero crossings. Circuit breakers are the earliest type of electrical device.

The Bulk Oil Circuit Breaker (BOCB)

In the BOCB, oil is used to arc the quenching media and as an insulating media between the earth parts of the breaker and the current-carrying contacts. The oil used for transformer insulation is used in the BOCB.

Its working principle says that an arc is generated between the separated current-carrying contacts in the oil when the current-carrying contacts are separated. The arc that is formed produces a rapidly growing gas bubble around it. When the moving contacts are moved away from the arc’s fixed contact, the arc’s resistance increases. This leads to a lower temperature because the resistance will increase. Therefore, the formation of gasses around the arc will be reduced.

Current quenching in the BOCB occurs when the current crosses through a zero-crossing. As the gas bubble encases inside the oil, the vessel is airtight. Oil will surround the bubble with high pressure, causing highly compressed gas around the arc. By increasing the pressure, the deionization of the gas also increases, resulting in arc quenching. The hydrogen gas will assist in cooling the arc quenching in the oil circuit breaker.

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