What is Vacuum Circuit Breaker? : Working and Its Applications

May 21, 2022 | Circuit Breaker | 0 comments

Vacuum Circuit Breaker is a circuit breaker that uses vacuum as an arc extinction medium. A permanently sealed vacuum interrupter surrounds the fixed and movable contacts of this circuit breaker. As the contacts separate in high vacuum, the arc disappears. It is mostly utilised for medium voltage applications between 11 and 33 kV.

They’re employed in power systems for switching and protection. In the 1970s, vacuum circuit breakers replaced oil circuit breakers, followed by SF6 circuit breakers in the 1980s.

These breakers are the most insulating of any medium. The current is interrupted by the vacuum circuit breaker at the first current zero. It signifies that the current is interrupted in the half cycle.

What is Vacuum Circuit Breaker?

Vacuum Circuit Breaker is generally known as VCB in technical language. A vacuum circuit breaker is a sort of circuit breaker that is unique. The arc is quenched by vacuum media in this sort of circuit breaker. The vacuum is used in VCB because its dielectric strength is significantly superior to that of any other medium. When compared to other dielectric mediums, vacuum is the superior dielectric medium for extinct employing the arc.

Because a vacuum circuit breaker is used for both switching and protecting the connected equipment, it must be particularly fast-acting to ensure that if there is a fault, the breaker quickly trips before the fault current may damage the equipment. As a result, these breakers are required at network incomers and interconnectors.

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Vacuum Circuit Breaker Principle and Norms

Arc formation and extinction in a vacuum circuit breaker can be explained as follows:

When the contacts of the breaker are opened in a vacuum (10-7 to 10-5 torr), the ionisation of metal vapours in the contacts produces an arc between them. The arc is swiftly extinguished, however, because the metallic vapours, electrons, and ions created during the arc immediately condense on the surfaces of the circuit breaker contacts, restoring dielectric strength quickly.

The vacuum circuit breaker has two outstanding characteristics.

High insulating strength: Vacuum is a superior dielectric medium in contrast to other insulating media used in circuit breakers. Except for air and SF6, which are used at high pressure, it outperforms all other media.

An interruption happens at the first current zero when an arc is opened by pushing the contacts apart in a vacuum. In comparison to other breakers, their dielectric strength increases hundreds of times when the arc is interrupted.

Breakers with these two features are more efficient, less bulky, and less expensive. Their service life is likewise significantly longer than that of any other circuit breaker, and they require almost little maintenance.

Construction of Vacuum Circuit Breaker

When compared to other circuit breakers, it is extremely simple to construct. Fixed contacts, moving contacts, and an arc shield that is positioned inside the arc interrupting chamber make up the majority of their construction.

The vacuum circuit breakers exterior envelope is composed of glass, which aids in the evaluation of the breaker from the outside after operation. If the glass turns milky instead of its usual silvery mirror polish, it means the breaker is losing vacuum.

The breakers fixed and movable contacts are located inside the arc shield. When a vacuum interrupter is sealed off, the pressure is held at around 10-6 torr. Depending on the working voltage, the circuit breaker’s movable contacts move a distance of 5 to 10 mm.

The stainless steel metallic bellows are utilised to move the moving contacts. Because the life of the vacuum circuit breaker is dependent on the component’s capacity to execute repeated operations satisfactorily, the design of the metallic bellows is critical.

However the vacuum circuit breaker from EVR Power has long life compare to other vacuum circuit breaker manufacturer. Due their consistent hard work and no compromise in quality EVR Power manufacture best Vacuum Circuit Breaker in India.

Workings of Vacuum Circuit Breaker

When two contacts split owing to an exceptional scenario, an arc is formed between them, which is caused by the ionisation of metal ions and is highly dependent on the contact material.

Vacuum interrupters have a different arc dispersion than other circuit breakers. The light evaporates when the contact is isolated. This completes the contact information. The contact material is segregated from the positive ions. The density of steam is determined by the arc current. The light rate of steam reduces as the current drops.

If the vapour density is minimal, the medium regains its dielectric strength after the current zero. In a vacuum, there are many parallel pathways to the arc when the restricted current is very small. The total current is divided into many arcs. Which resist and spread across the contact surface. A scattered arc is a type of arc that is easily disturbed.

Rapid evaporation of the contact surface occurs when current is concentrated in a small area of the arc at a high value. If the arc is distributed, it is conceivable for it to be disrupted. The arc will hit again if it is immediately removed from the contact surface.

The substance of the contact and the method of handling the metal vapour have a big impact on arc destruction in a vacuum breaker. The arc’s course is altered to ensure that the temperature does not rise at any point.

After the final arc disruption, the dielectric strength rapidly increases, which is ideal for a vacuum breaker. They’re ideal for capacitor switching. Because it will perform without re-striking. The little current is interrupted before it reaches zero, which can lead it to cut at a level that is dependent on the contact material.

Vacuum Circuit Breaker Application

Vacuum circuit breakers are now used in high voltage substations and transmission networks as well as medium voltage power systems.

It’s due of VCB’s many benefits, including high interruption capability, long operation life, safety, and excellent cost-performance. Many promising new items have been developed in the past and will be developed in the future based on the uses of these superlative traits.

Vacuum circuit breakers have advanced significantly in recent years and are now employed in a variety of applications.

High Voltage Application

 Since the 1997 Kyoto Protocol, SF6 gas has been identified as one of the primary global warming gases. Since then, a vacuum circuit breaker has emerged as the most likely candidate for replacing SF6 gas circuit breakers.

A vacuum circuit breaker is considered a more desired circuit breaker than an SF6 circuit breaker since it can interrupt a current in a vacuum without emitting any special dangerous gas to the environment, and it is also composed of an ordinary ceramic or glass, and metallic components.

As a result, increasing the application voltage to replace SF6 type circuit breakers is desirable.

DC circuit breaker for other applications

VCB is deemed ideal for DC current interruption because it can interrupt under very high di/dt-dv/dt circumstances and can quickly interrupt a DC current once a high frequency current is superposed on it.

As a result, EVR Power are shaping the DC circuit breaker in a very small size because the vacuum interrupter is easy to work in very high frequency settings.


The use of vacuum circuit breaker has been on a rise as it provides reliable service for medium voltage network. It also eliminates the need for an expensive switchgear, which is necessary in case of low or high-voltage networks. The VCBs are designed to open and close automatically according to input signals from sensors.

The Vacuum Circuit Breakers from EVR Power are dependable for the current interruption in medium voltage. Currently the most consistent and reliable manufacturer of Vacuum Circuit Breakers in Chennai are EVR Power. This vacuum circuit Breakers has a voltage range of 11 to 33 kilovolts.

Within the range of voltage ratings, they must make and break all current. They go from low capacitive and inductive currents to large short-circuit currents. Hence Vacuum Circuit Breakers from EVR Power are best as they are cost effective, long lasting and also it provide relief from regular oil refilling and other maintenance cost.


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