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Advantages and disadvantages of vacuum circuit breakers

By:Nader Updated:September 09,2020 11:29AM

Vacuum circuit breakers are mostly used in high-voltage switchgear, which refers to a circuit breaker that uses vacuum as an arc extinguishing and insulating medium to open and close current in a vacuum vessel. Since the advent of vacuum circuit breakers in the early 1960s, with the improvement of various key processes and the development of new arc extinguishing chambers and operating mechanisms, the technical parameters of vacuum circuit breakers have been continuously improved, with excellent performance and outstanding performance. The advantages have been developed rapidly, and the application in high-voltage switch cabinets has become more and more extensive.

It is precisely because of the advantages of vacuum circuit breakers that the application rate in high-voltage switchgear is so high. Today, Shanxi switchgear manufacturer Jintaiheng will give you a specific introduction to the advantages and disadvantages of vacuum circuit breakers.

Advantages of vacuum circuit breakers:

  1. Extinguish the arc in a sealed container, and the arc and hot gas are not exposed. As a separate component, the arc extinguishing chamber is simple and convenient to install and debug.
  2. The contact gap is very small, generally about 10mm, the closing power is small, the mechanism is simple, and the service life is long.
  3. The arc extinguishing time is short, the arc voltage is low, the arc energy is small, the contact loss is small, and the number of breaking times is large.
  4. The inertia of the movable guide rod is small and can be used frequently.
  5. Small operating mechanism, small size and light weight.
  6. The control power is small, and the action noise is small during switch operation.
  7. The arc extinguishing medium or insulating medium does not use oil, there is no danger of living and explosion, and it is safe.
  8. The contact head is divided into a completely sealed structure, and its performance will not be reduced by the influence of moisture, dust, harmful gases, etc. Reliable work, stable on-off performance.
  9. After the arc is broken, the medium between the fractures recovers quickly, and the medium does not need to be replaced.
  10. The ring will not age or need to be replaced. Within the service life, the contact part does not need to be repaired or inspected. Generally, it can be up to about 20 years without inspection. The maintenance workload is small, and the maintenance cost is low, only about 1/20 of the oil-less circuit breaker.
  11. With multiple reclosing function, suitable for the application requirements of distribution network.

What are the disadvantages of vacuum circuit breakers:

  1. When the inductive load or capacitive load is disconnected, it is easy to cause over-voltage due to current interception, justification, reignition, etc., and corresponding over-voltage protection should be adopted.
  2. The one-time investment price of the product is relatively high, which is mainly determined by the professional production of the vacuum interrupter and the requirements of institutional reliability. If the operation and maintenance costs are comprehensively considered, the price is not high.
  3. Since the contact structure of the vacuum circuit breaker adopts the butt connection type, and the operating mechanism uses a spring, it is easy to produce closing bounce and opening rebound. Closing bounce will not only produce high overvoltages that affect the stable operation of the power grid, but also cause contact burnout or even welding, especially when the capacitor bank is used to generate inrush current and short-circuit closing. Opening bounce will reduce the distance between the contacts after the arc, leading to a heavy breakdown after the arc, and the consequences are very serious.

Vacuum circuit breakers generally used in high-voltage switch cabinets belong to indoor vacuum circuit breakers. For example, vacuum circuit breakers are used in KYN28 mid-mounted high-voltage switch cabinets. At present, my country's 10KV vacuum circuit breakers have basically replaced oil circuit breakers, and their utilization rate has exceeded 96%; the utilization rate of 35KV vacuum circuit breakers has exceeded 62%. Vacuum circuit breakers have become the most widely used circuit breakers in the medium voltage field below 35KV.