According to any top vcb manufacturer, among other circuit breakers such as oil, Airblast, and sulfur hexafluoride circuit breakers, the vacuum circuit breaker is the most dependable.
In this article, we will learn all there is to know regarding vacuum circuit breakers, including their construction and operation, as well as the benefits, drawbacks, and uses of this circuit breaker.
When it comes to using an arc quenching medium in a vacuum circuit breaker, the excerpts recommend using the vacuum of the order of 10-5 to 10-7 torr. (1 torr = 1mm of Hg). A vacuum is defined as a pressure lower than atmospheric pressure in which no gas exists. They are utilized in power systems for switching and protection.
In the 1970s, vacuum circuit breakers replaced oil circuit breakers, and in the 1980s, SF6 circuit breakers were also replaced by vacuum circuit breakers. Just like the new and modern valves manufacturer replaced the typical tap system.
The insulating strength of these breakers is greater than that of any other medium. At the initial current zero, the vacuum circuit breaker interrupts the current. This somehow upsets the current during the half-cycle. This line will be discussed in depth in the second half of this post.
Working of VCB
The fixed and moving contacts are first linked to each other, and current can flow between them. When a failure arises in the system, however, the moving contact begins to separate from the stationary contact, and the arcing event happens among two.
Vacuum circuit breakers generate arcs in a different manner. The arc is caused by the evaporation of metal vapors first from the contact surface. A contact surface features a high number of tiny projections that are activated when current passes through them.
We now understand that after removing the contacts, the final source of charge will be the contact surface, resulting in high current density at these spots and resistive heating.
Metal ions begin to vaporize from the contact surface as a result of overheating. Whenever these ions come into touch with two contacts, they establish a channel for the current, and the power begins to flow, resulting in an arc. In these breakers, arc is generated in this manner.
Construction of VCB
It features a glass outer envelope that is linked with end caps. This glass shield is meant for purpose to be an inspection tool for the breaker after an intervention. Now if the color appears milky white, the breaker is simply losing its vacuum. Two contacts are used: fixed contact and moving contact. The primary arcing occurs between these two connections.
The moving contact is coupled by metallic bellows that are constructed with the use of stainless steel. These bellows are responsible for moving the moving element up and down, and they are operated by a spring mechanism attached to the bellows.
A stainless steel sputter shield is installed to prevent metal vapor from reaching and harming the outer envelope. In order to insulate the chamber, a ceramic exterior is also provided.
Applications of VBC
With even a modest rating of 60 to 100 megavolt-amperes, they are acceptable for the number of rural applications. A vacuum circuit breaker is used as an extremely high-speed making switch in several industrial applications due to its tiny gap and excellent recovery. Even if you own a tin can packaging machine that works on a small scale, you can use VCB with reliability.
Whenever the voltage applied is on the higher side and the current to be disrupted seems to be little, these breakers clearly outperform the others.
In comparison to other interrupting devices, the cost for minor fault interrupting capacity is minimal. Furthermore, owing to the low maintenance needs, these breakers are ideal for systems requiring voltages ranging from 11 to 33 kV.
These types of circuit breakers are suitable for both indoor and outdoor usage. Because they need less care and last longer, they are ideal for distant regions such as hills or rural areas. Reactor switching, capacitor bank switching, and transformer switching are all done using vacuum circuit breakers.
Advantages of VBC
Following are some top benefits of VCB:
- There seem to be no fire dangers or fire risks.
- Such breakers have a small footprint.
- VCBs are less maintenance-requiring tools due to which they have a longer lifespan.
- These are quite dependable. This implies they have a very high possibility of successfully completing the arc extinction process every time.
- The operation that is noiseless or silent
- When compared to other circuit breakers, arc energy is modest.
- They are also resistant to lightning strikes.
- Rapid operation (interrupts current during its first half cycle.
Disadvantages of VBC
Have a look to learn some minor disadvantages of VCBs:
- They have a restricted voltage range and cannot be utilized for higher voltage levels somewhat like the SF6 circuit breaker.
- If they are utilized at voltage levels over 36kV, certain units must be linked in series, increasing complexity as well as expense.
- Extra precautions should be taken to prevent leaking.
Well, now you have it all: a thorough explanation of vacuum circuit breakers and their properties. Whether it is about their advantages, disadvantages, how VCBs work, and how they are constituted; we have everything covered above.