Advantages and disadvantages of vacuum circuit breakers

Vacuum circuit breakers are often used in high-voltage switchgears, which refer to circuit breakers that use vacuum as an arc-extinguishing and insulating medium for current breaking and closing 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 outstanding performance and outstanding The advantages have been rapidly developed, and the application in high-voltage switchgear has become more and more extensive.

Because of the advantages of vacuum circuit breakers, the application rate in high-voltage switchgear will be so high. The following is a brief introduction to the advantages and disadvantages of vacuum circuit breakers.

Advantages of vacuum circuit breakers:

1. Extinguish the arc in a sealed container, the arc and hot gases are not exposed. As an independent 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 work 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 moving guide rod is small and can be used frequently.

5. The operating mechanism is small, the whole machine is small in size and light in weight.

6. The control power is small, and the operation noise is small when the switch is operated.

7. The arc extinguishing medium or insulating medium does not use oil, and there is no danger of being alive and exploding, and it is safe.

8. The contact part is completely sealed and will not be affected by moisture, dust, harmful gases, etc. Reliable operation and 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 replace. Within the service life, the contact parts do not need to be repaired or inspected, and generally do not need to be repaired for about 20 years. 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 functions, it is suitable for distribution network application requirements.

Disadvantages of vacuum circuit breakers:

1. When inductive or capacitive load is disconnected, overvoltage is easily caused due to interception, properness, reignition, etc., and corresponding overvoltage protection should be adopted.

2. The high investment price of the product is mainly determined by the professional production and reliability requirements of the vacuum interrupter. If the operation and maintenance costs are comprehensively considered, the price is not high.

3. Since the contact structure of the vacuum circuit breaker is a docking type, the operating mechanism uses a spring, which is easy to generate closing bounce and opening rebound. Closing bounce not only produces a higher overvoltage affecting the stable operation of the grid, but also burns or even welds the contacts, especially in the case of input capacitor banks generating inrush currents and short circuit closures. The rebound of the trip will reduce the contact spacing behind the arc, resulting in heavy breakdown after the arc, the consequences are very serious.

The vacuum circuit breaker generally used in the high-voltage switchgear is an indoor vacuum circuit breaker. For example, the vacuum circuit breaker is used in the KYN28 medium-mounted high-voltage switchgear. At present, China's 10KV voltage class vacuum circuit breaker has basically replaced the oil circuit breaker, and its utilization rate has exceeded 96%; the utilization rate of the 35KV voltage class vacuum circuit breaker exceeds 62%. Vacuum circuit breakers have become the most widely used circuit breakers in the medium voltage range below 35KV.