[overview of the development and characteristics of vacuum circuit breaker]: vacuum circuit breaker refers to the circuit breaker with contacts closed and opened in vacuum. Vacuum circuit breakers were first studied in Britain and the United States, then developed to Japan, Germany, the former Soviet Union and other countries. From 1959, China began to study the theory of vacuum circuit breakers, and in the early 1970s, it formally produced various types of vacuum circuit breakers

Vacuum circuit breaker refers to the circuit breaker that contacts close and open in vacuum.

Vacuum circuit breakers were first studied in Britain and the United States, then developed to Japan, Germany, the former Soviet Union and other countries. From 1959, China began to study the theory of vacuum circuit breakers, until the early 1970s, it formally produced all kinds of vacuum circuit breakers. With the continuous innovation and improvement of manufacturing technologies such as vacuum interrupter, operating mechanism and insulation level, the development of vacuum circuit breaker is extremely rapid, and a series of significant achievements have been made in the research of large capacity, miniaturization, intelligence and reliability.

With the advantages of good arc extinguishing characteristics, suitable for frequent operation, long electrical life, high operation reliability and long maintenance cycle, vacuum circuit breaker has been widely used in the power industry, urban and rural power grid reconstruction, chemical industry, metallurgy, railway electrification, mining and other industries. From several varieties of zn1-zn5 in the past to dozens of models and varieties now, the rated current reaches 4000A, the breaking current reaches 5oka, even 63kA, and the voltage reaches 35kV level.

The development and characteristics of vacuum circuit breaker will be seen in the following aspects: the development of vacuum interrupter, the development of operating mechanism, and the development of insulation structure.

2. Development and characteristics of vacuum interrupter

2.1 development of vacuum interrupter

The idea of using vacuum medium to extinguish the arc was put forward at the end of 19th century. The earliest vacuum interrupter was made in 1920s. However, due to the limitations of vacuum technology, materials and other technical levels, it was not practical at that time. After the 1950s, with the development of new technology, many problems in the manufacturing of vacuum interrupter have been solved, making the vacuum switch gradually reach the practical level. In the mid-1950s, General Electric Company of the United States produced a batch of vacuum circuit breakers with rated breaking current of 12ka. Then in the late 1950s, due to the development of a vacuum interrupter with transverse magnetic field contacts, the rated breaking current was raised to the level of 3oka. After the 1970s, Toshiba electric company of Japan successfully developed a vacuum interrupter with longitudinal magnetic field contacts, which further increased the rated breaking current to more than 5oka. At present, vacuum circuit breakers have been widely used in 1OkV and 35kV distribution systems. The rated breaking current can reach 5oka-100kao. Some countries have also produced 72kV / 84KV vacuum interrupters, but the number is small. DC high voltage generator

In recent years, the production and development of vacuum circuit breakers in China is also very fast. At present, the technology of vacuum interrupter in China is similar to that of foreign products. There are Vacuum Interrupters with longitudinal and transverse magnetic field technology and central pilot contact technology. The contacts made of Cu Cr alloy materials have successfully disconnected the vacuum interrupters in China of 5 Oka and 63 Kara, which have reached a higher level. The vacuum interrupters made in China can be selected completely.

2.2 characteristics of vacuum interrupter

Vacuum interrupter is the key component of vacuum circuit breaker. It is supported and sealed by glass or ceramic. There are dynamic and static contacts and shielding cover inside. There is negative pressure in the room. The vacuum degree is 133 × 109 133 × ljpa, which ensures the interrupter performance and insulation level when it is disconnected. When the vacuum degree is reduced, its breaking performance is obviously reduced, so the vacuum arc extinguishing chamber shall not be impacted by any external force, knocking, hand tapping, moving and maintenance shall not be stressed o it is forbidden to put anything on the vacuum circuit breaker to prevent the vacuum arc extinguishing chamber from being damaged when falling. Before leaving the factory, the vacuum circuit breaker shall be checked and assembled in strict parallelism. During maintenance, the bolts of the arc extinguishing chamber shall be tightened to ensure the uniform stress.

The vacuum circuit breaker interrupts the current and interrupts the arc in the vacuum arc extinguishing chamber, but the vacuum circuit breaker itself has no device for qualitative and quantitative monitoring of the vacuum degree characteristics, so the vacuum degree reduction fault is a hidden fault. At the same time, the vacuum degree reduction will seriously affect the ability of the vacuum circuit breaker to disconnect the overcurrent, and lead to the sharp decline of the service life of the circuit breaker, which will cause the switch explosion.

To sum up, the main problems of vacuum interrupter are the decrease of vacuum degree. The main reasons for the decrease of vacuum are as follows.

(1) Vacuum circuit breaker is a relatively delicate component. After leaving the factory, after many times of transport bumps, installation vibration, accidental collision, etc., leakage of glass or ceramic sealing may occur.

(2) There are some problems in the material or manufacturing process of vacuum interrupter, and there are leakage points after several operations.

(3) For the split type vacuum circuit breaker, such as the use of electromagnetic operating mechanism, when operating, due to the large distance between the operating links, it directly affects the synchronization, bounce, overstroke and other characteristics of the switch to speed up the vacuum degree reduction. DC high voltage generator

Treatment method for vacuum degree reduction of vacuum interrupter:

Frequently observe the vacuum interrupter and regularly use the vacuum degree tester of vacuum switch to measure the vacuum degree of the vacuum interrupter to ensure that the vacuum degree of the vacuum interrupter is within the specified range; when the vacuum degree is reduced, the vacuum interrupter must be replaced, and the stroke, synchronization, bounce and other characteristic tests shall be done.

3. Development of operating mechanism

The operating mechanism is one of the important aspects to evaluate the performance of the vacuum circuit breaker. The main reason that affects the reliability of the vacuum circuit breaker is the mechanical characteristics of the operating mechanism. According to operation