Overview of the development and application of vacuum switches

1. Overview of the development of foreign vacuum switches

    Human beings are engaged in the application research of vacuum as an arc extinguishing and insulating medium, and it has a history of more than 100 years. As early as 1893, American Rittenhause (Rittenhause) designed the world's first vacuum interrupter and published it in the form of a patent; in 1920, Sweden's Birka company developed the world's first one. Vacuum switch: In 1926, Professor Sornsen of the California Institute of Technology published the test results of vacuum switches and predicted that the era of vacuum switches would soon come. As the vacuum technology at that time was still very backward, the practical application of vacuum switches in industry was greatly delayed.

    Around 1950, with the development of vacuum technology and related technologies such as metallurgical technology, the manufacturing technology of vacuum interrupters was improved, and the research on the industrial application of vacuum switches was restarted. In 1956, H. Cross modified the vacuum switch for high-frequency circuits produced by Jenning Radio Manufacturing Company (Jenning), and trial-produced a 15kV, 200A vacuum switch.

    In 1961, General Electric Company of the United States first successfully developed vacuum circuit breakers with rated voltages of 15kV and 12.5kA on the basis of summing up previous experiences. In 1966, they successfully developed vacuum circuit breakers with rated voltages of 15kV and breaking currents of 25kA and 31.5kA. Since then, vacuum switches have officially entered the ranks of power switches, and the United States has therefore become the first country in the world to mass-produce and use vacuum switches. Under its influence and promotion, some countries in Europe and Asia have also begun research and development work. Vacuum switches have since Recognized and developed on a global scale.

    In the early 1970s, the global oil-free wave of medium voltage switches brought unprecedented development opportunities to vacuum switches. With its own huge technical advantages, it took less than 20 years for the vacuum switch to replace the oil-less switch and become the leading product in the medium voltage field. At present, the single-break vacuum circuit breaker has reached the voltage level of 145kV, and the short-circuit breaking current has reached 200kA.

2. Overview of the development of vacuum switches in my country

    The research and development of vacuum switches in my country began in the late 1950s, basically synchronized with the United States and slightly earlier than Japan.

    In 1958, the Electrical Department of Xi’an Jiaotong University and the then Xi’an High-Voltage Switch Rectifier Factory jointly established a factory-school joint research team. Associate Professor Wang Jimei and Chief Engineer Tong Yongchao were responsible for the development of vacuum switches. Less than half a year after its establishment, the group successfully developed my country's first vacuum interrupter, and passed the 50Hz, 4kV, and 5kA current breaking test on the synthetic circuit of the Electrical Laboratory of Xi'an Jiaotong University.

    Since then, Xi’an High Voltage Electrical Apparatus Research Institute successfully developed a single-phase vacuum switch with a voltage of 6.7kV and 500A in 1960. Xi’an Jiaotong University successfully developed a 10kV, 1500A three-phase vacuum switch in 1964. In the same year, this three-phase vacuum switch When it was exhibited at the National Higher Education Exhibition in Beijing, it was praised by experts from all over the country and attracted great interest from switch manufacturers in various provinces and cities across the country. It was the starting point for promoting the production and development of vacuum switches in my country.

    On September 5, 1968, the national key national defense project (Project 6895) was implemented in Huaguang Electronic Tube Factory. In the same year, my country’s first commercial vacuum interrupter was born. Since then, Huaguang Electronic Tube Factory has become the first domestic manufacturer of vacuum interrupters. enterprise.

    Afterwards, due to the influence of the "Cultural Revolution", my country's work on vacuum arc theory research and vacuum switch development was temporarily suspended, and it was only resumed in 1976. At that time, the main domestic institutions engaged in vacuum arc theoretical research were Xi'an Jiaotong University, Xi'an High Voltage Electrical Apparatus Research Institute and Shanghai Electrical Apparatus Research Institute. After 1978, more than 10 domestic factories have formally put into the production of vacuum switches. The vacuum interrupters required are mainly produced by Baoguang Electric Industrial General Factory and Huaguang Electronic Tube Factory.

    In 1984, Xi’an High Voltage Electrical Apparatus Research Institute, Guilin Electrical Apparatus Research Institute, Baoguang Electrical Industry General Factory and Beijing Switch Factory jointly introduced the complete set of manufacturing technology (including CuCr contact material, vacuum Three parts: arc extinguishing chamber and vacuum circuit breaker). In 1986, Huaguang Electronic Tube Factory introduced a complete set of vacuum interrupter manufacturing technology (including CuCr contact material) from Westinghouse. These two introductions have greatly improved the manufacturing and design level of China's vacuum switch industry, and laid a technical foundation for the development and prosperity of my country's vacuum switch industry.

    In 1992, the two ministries (that is, the Ministry of Machinery and Electronics Industry and the Ministry of Energy) held the "Tianjin Conference" on the widespread promotion and application of vacuum switches in power systems. Since then, my country's vacuum switches have entered a period of rapid development, and various reasons have appeared in the market. my country's independent development of vacuum circuit breakers with technical indicators reaching the foreign advanced level at that time, its representative products include ZN23, ZN28 and ZN63A. At this stage, my country has been able to produce vacuum circuit breakers with a rated voltage of 35kV and a breaking capacity of 31.5kA and 10kV, 50kA and 63kA. By 2003, my country had developed 72.5kV, 110kV/31.5kA and 18 kV/80kA single-break vacuum circuit breakers. The industry produced more than 200,000 vacuum switches per year. The world has the largest number of vacuum switch manufacturers, production and sales. With the largest volume and the most variety series, it has become a veritable "Vacuum Switch Kingdom".

3. The status of vacuum interrupter industry at home and abroad

    1. United States

    The United States is the first country in the world to start the production and use of vacuum switches. At present, the main manufacturers of vacuum interrupters are General Electric (GE), Westinghouse (WH), Cooper (Cooper) and Jenning (Jenning). It is the first company in the world to systematically study vacuum switch and vacuum arc theory.

    In the early 1960s, Li Tianhe of GE and others proposed the principle of transverse magnetic field arc extinguishing, and based on this, developed a vacuum interrupter based on the spiral groove transverse magnetic contact structure and CuBi contact material to short-circuit the vacuum switch The breaking capacity has been increased to 15kV and 12.5kA, which makes the vacuum switch truly commercially practical. Therefore, Li Tianhe is called the "father of vacuum switch." In the following two decades, GE has done a lot of work in arc extinguishing mechanism, contact materials, test methods and test equipment. Its technology has been in the leading position in the world in the mid-1980s and before , And have exported to companies in Germany, Japan and other countries.

    At present, the company mainly produces vacuum interrupters with a rated voltage of 4.16kV~45kV, a rated current of 630A~3000A, and a rated short-circuit breaking current of 18kA~60kA. The spiral groove transverse magnetic contact structure is still the main product.

    It is worth mentioning that the company has connected 14 vacuum interrupters in series and developed a vacuum circuit breaker with a rated voltage of up to 765kV and a short-circuit breaking capacity of 40kA.

    WH Company began to develop vacuum interrupters in 1960. It is another major manufacturer of vacuum interrupters and vacuum switches in the United States. At present, the company has surpassed GE in terms of technology, manufacturing process, and output. One of the largest manufacturers of vacuum interrupters. The company's 24kV and below products generally use spiral groove transverse magnetic contact structure, and 36kV and above products use coil type longitudinal magnetic structure, with an annual production capacity of more than 250,000 pieces. In addition to some self-supporting use, its products are also exported to Asia in large quantities And Europe.

    At present, the company's main products are vacuum interrupters with rated voltages of 0.4kV~38kV, rated currents of 200A~3150A, and rated short-circuit breaking currents of 12.5kA~63kA. In addition to some self-supporting applications, they are also exported to Asia and Europe.

    In 1994, the control and distribution division of WH was merged into Eaton, which established Eaton Electric (Suzhou) Co., Ltd. in Suzhou, my country in 2000, which mainly produces vacuum switches and vacuum interrupters.

    2. United Kingdom

    Britain’s research and development work on vacuum switches is almost synchronized with that of the United States. Its main manufacturer is GEC (later merged with Alsthom and AREVA in France), which made the world’s first practical vacuum contactor in 1965. In 1969, a vacuum circuit breaker for 25kV single-phase electrified railway was manufactured. GEC Company developed cup-shaped transverse magnetic contacts based on the spiral groove transverse magnetic contact structure in the 1960s, and first began to use CuCr contact materials in vacuum interrupters. At present, the company mainly produces products of 12kV~38kV, rated current 1250A~2000A, and rated short-circuit breaking current 13.1kA~40kA. The contact structure is mainly cup-shaped transverse magnetic contact.

    3. Germany

    The main German manufacturers are Seimens, AEG (later merged into French Alsthom company, AREVA company) and Calor-Emag company (later merged into ABB company), and their technology sources are the United States and the United Kingdom.

    Seimens company introduced technology from British VIL company (belonging to GEC company) in the 1970s. In the 1980s, the company improved the manufacturing process of CuCr contact material of the contact structure and invented the cup-shaped longitudinal magnetic field. Contact structure and infiltration method (production of CuCr contact material). After more than 30 years of development, Seimens has become one of the largest vacuum switch manufacturers in the world. Seimens Company currently mainly produces vacuum interrupters with 1kV~38kV, rated current 400A~4000A, and rated short-circuit breaking current 12.5kA~63kA. The annual output is about 180,000 pieces. In addition to some self-supporting use, it also exports a lot to Asia and Europe.

    The vacuum interrupter of Seimens Company is mainly cup-shaped transverse magnetic contact structure, but the vacuum interrupter of 12KV, 24kV/31.5kA and 36kV adopts cup-shaped longitudinal magnetic contact structure.

    AEG company began serial production of vacuum interrupters in 1979, and its technology originated from the British GEC company. The company currently mainly produces products with a rated voltage of 12kV~36kV and a rated short-circuit breaking current of 8kA~50kA, mainly cup-shaped transverse magnetic contacts, but 12KV/63kA, 24kV, 36kV/40kA products use longitudinal magnetic contacts structure.

    Calor-Emag company introduced technology from American WH company in the 1980s. Its vacuum interrupter products generally adopt spiral groove transverse magnetic contact structure (with certain differences from WH company), and mainly produce 7.2kV~40.5kV, rated Products with a current of 400A~4000A and a rated short-circuit breaking current of 12.5kA~63kA have an annual output of about 200,000 pieces, mainly for self-supporting use.

    After Calor-Emag was merged into ABB, a lot of research work has been done on the electrode structure and external insulation of the vacuum interrupter. In 1997, the world's first solid-sealed vacuum interrupter (solid-sealed pole) was launched. The insulation characteristics of the vacuum circuit breaker have been improved and the assembly has been simplified. At present, the output has reached about 100,000.

    4. Japan

    Japan began to develop vacuum switches in the early 1960s. Its manufacturers include Toshiba, Meidensha, Fuji, Hitachi, and Mitsubishi. The products are mainly based on the longitudinal magnetic field structure, but each has its own characteristics. Among them, Toshiba is the most Representative.

    Toshiba is the first manufacturer of vacuum switches in Japan to develop. The company developed Japan’s first commercial vacuum interrupter in 1965. After introducing the technology from GE in 1968, it has developed rapidly and has accumulated production so far. With more than 2.5 million vacuum interrupters, it is the largest manufacturer in Japan. In addition to self-supporting use, its products are also exported to countries in Asia and Europe.

    Toshiba took the lead in the world to use longitudinal magnetic field contacts (coil structure) in 1976, and changed the original CuBi contact material to CuCr contact material, which greatly improved the breaking capacity of the vacuum switch. Reached 200kA (laboratory level) under 12kV. In addition, Toshiba has carried out a lot of work on high voltage and low surge.

    Toshiba mainly produces products with 7.2kV~84kV, rated current 400A~4000A, and rated short-circuit breaking current 12.5kA~100kA. The annual output is about 50,000 to 100,000.

    In recent years, the power transmission and distribution product market has shrunk due to the reduction in Japan's domestic power investment. In order to improve market competitiveness, major companies have begun strategic restructuring. In July 2001, Meidensha, Fuji and Hitachi jointly established AE Pawa Co., Ltd. on the basis of their original power transmission and distribution industries. The new company will gradually replace the power transmission and distribution business of the original three companies. In March 2002, Toshiba and Mitsubishi Corporation announced the establishment of a joint power transmission and transformation company (TMT&D), and the new company replaced the original functions of the two companies in the sales, design, development and manufacturing of power transmission and transformation, becoming the largest in Japan Transmission and transformation company.

    5. China

    my country began the practical development of vacuum interrupter in 1968, and the first commercial vacuum interrupter was born in the state-owned Huaguang Electronic Tube Factory (777) in the same year. In 1975, the ZKBD-1000/10-20 vacuum interrupter developed by the former State-owned Bao Photoelectric Factory (4401) passed the original Ministry of Machinery Industry (Ministry of Machinery Industry) and the former Ministry of Machinery Industry ( The two appraisals organized by the Ministry of Electronics Industry indicate that my country's vacuum interrupter has entered the practical stage.

    In the mid-1980s, the former Guoyingbao Optoelectronics Factory and Huaguang Electronic Tube Factory introduced the manufacturing technology of vacuum interrupter and contact material from Germany and the United States, which greatly shortened the gap between my country's vacuum interrupter industry and foreign companies. Therefore, my country's vacuum interrupter and vacuum switch industry have laid a solid foundation for the take-off. At present, my country has formed a vacuum interrupter industrial system led by the former state-owned military industrial enterprises 4401, 779, 771 and 777. In 2004, the industry produced more than 800,000 (no low pressure statistics), becoming the world's largest vacuum interrupter. Interrupter production base.

    At present, my country has been able to produce various vacuum interrupters with a rated voltage of 0.38kV~40.5kV and a rated short-circuit breaking current of 12.5kA~80kA. Among them, the vacuum interrupter for circuit breakers adopts coil contact structure in the 40.5kV part. All adopt cup-shaped longitudinal magnetic field contact structure.

    Over the past 30 years, my country's vacuum interrupter design theory, manufacturing process, and quality level have all made qualitative leaps. Rough division, it can be considered that the development of domestic arc extinguishing chamber has gone through five generations. The first-generation vacuum interrupter made in China, with a rated voltage of 12kV and a φ145mm glass insulated shell, the electrode structure is Archimedes spiral groove transverse magnetism, the use of CuBi alloy contacts, the breaking capacity reaches 20kA, and the rated current is 1250A ZKBDl250 /10-20 type vacuum interrupter is the representative; the second generation vacuum interrupter is the introduction of Siemens 3AF series vacuum interrupter, which is characterized by exposed shielding cylinder, ceramic insulation shell, and electrode structure with cup-shaped transverse magnet. CuCr50 alloy ring contact, breaking capacity up to 31.5kA, rated current up to 2500A, after development, rated current up to 3150A, breaking capacity up to 40kA; developed the third-generation vacuum killer based on digestion and absorption of imported technology The arc chamber is characterized by a built-in shielding cylinder, a φ88~125mm ceramic insulating shell, a cup-shaped longitudinal magnetism electrode structure, CuCr50 contact material, a breaking capacity of 40kA, and a rated current of 3150A. During this period, some coil types were also developed. The arc extinguishing chamber of the longitudinal magnetic field electrode mainly improves the breaking capacity, but it is still dominated by cup-shaped longitudinal magnetism; the overall quality of the fourth-generation vacuum interrupter represented by the one-time sealing technology has been greatly improved. At this time, the comprehensive application of various mature technologies has developed a large number of vacuum interrupters with various parameters of 12kV, 24kV, 40.5kV, and low voltage 0.38kV~1.14kV. The products cover the entire medium voltage field. The miniaturized vacuum interrupter with external insulation protection can be called the fifth generation product, and it has begun to be supplied to the market in batches.

Fourth, the development trend of vacuum interrupter

    Since its inception, the vacuum interrupter has been continuously developing towards miniaturization, high reliability, and low cost. With the expansion of the application range of vacuum switches, the vacuum interrupter also has a new development direction.

1. Miniaturization

    The development of vacuum arc theory and optimization of internal electric field make the volume of vacuum interrupter smaller;

    The application of composite insulation technology greatly reduces the structural size of the vacuum interrupter;

    The improvement of the mechanical characteristics of the vacuum circuit breaker, the synchronous breaking technology and the application of high-performance contact materials make it possible to "upgrade" the vacuum interrupter and use it.

    The miniaturization of the vacuum interrupter has been carried out for many years both at home and abroad, and has achieved certain results. The VC2 vacuum circuit breaker newly developed by Calor-Emag, Germany, has a 12kV, 20kA vacuum interrupter with a contact diameter of only 40mm, and a 12kV, 50kA vacuum interrupter with a contact diameter of 80mm.

    The third-generation vacuum interrupter newly launched by German AEG has reduced its volume ratio to 1/3 of the original product.

    Toshiba Corporation of Japan has successfully developed the SADE technology. The volume of the vacuum interrupter using this technology is only half of the product with the coil contact structure.

2. Low cost

    The miniaturization of the vacuum interrupter ensures the possibility of low-cost realization. In the past 20 years, the volume of the domestic vacuum interrupter has been reduced by 50%, and the price has been reduced by about 70%. Among them, some manufacturers have improved the process level (such as the universal use of one-time sealing process) to improve production efficiency and Efforts to reduce production costs are also closely related to the cost reduction of parts such as contacts, bellows, and ceramic shells.

3. High voltage

    With the continuous improvement of vacuum switch manufacturing technology and theoretical research level, the development of vacuum switch has been trying to develop in the direction of high voltage and large capacity. The General Electric Company of the United States produced 168kV/40kA double-break vacuum circuit breakers after 1980, Japan Meidensha Company began to produce 145kV/31.5kA single-break vacuum circuit breakers in 1980, and Japan Toshiba Company successfully developed 145kV/31.5 in 1987. kA single-break vacuum interrupter and 168kV double-break vacuum circuit breaker. In addition, Japan's Mitsubishi Corporation has successfully developed a 270kV single-break vacuum interrupter and is preparing to develop a 500kV double-break vacuum circuit breaker. Once it is successfully developed, it is estimated that its cost will be lower than that of the SF6 circuit breaker of the same voltage level. At present, 126kV vacuum circuit breakers developed by Beijing Switchgear Factory and Xi'an High-Voltage Switchgear Factory (all adopt the vacuum interrupter of Japan's Meidensha) have passed all type tests and completed the appraisal at one time.

4. Large current

    Due to the large rated operating current of generator protection circuit breakers, it is difficult for vacuum circuit breakers to meet the temperature rise requirements. At the same time, due to the high transient recovery voltage rise rate after the short-circuit current is interrupted, a higher medium recovery speed is required , Therefore, its use has been restricted. However, in recent years, there have been considerable developments in vacuum circuit breakers and vacuum interrupters for generator protection. At present, 6300A/80kA vacuum generator protection circuit breakers can be produced in China.

5. Low voltage

    Low-voltage switch electrical products are basic electrical components with a large quantity and a wide range. Because vacuum switches have the characteristics of explosion-proof and long life, as long as the price is limited to a certain level, there is a huge market prospect. In 1994, German Siemens introduced vacuum circuit breakers with rated voltages of 380V to 1140V, rated currents of 630A to 2500A, and rated short-circuit breaking currents of 20kA to 65kA. At present, low-voltage vacuum circuit breakers and vacuum interrupters with 380V~1140V, rated current of 1600A~3200A, and rated short-circuit breaking current of 30kA~80kA have been developed in China.

6. Solid-sealed pole (solid-sealed vacuum interrupter)

    Using APG technology, the vacuum interrupter and other connecting components are solidly sealed into poles, which greatly improves the weather resistance of the vacuum circuit breaker, reduces the phase spacing, and makes the vacuum circuit breaker more compact and smaller in size; The application of solid sealing technology has strengthened the external insulation level of the vacuum interrupter. The height of the vacuum interrupter, especially the size of the insulating shell, can be shortened as much as possible. Based on the optimization of internal insulation, the volume of the vacuum interrupter Also reduced accordingly. However, the solid sealing technology requires a good combination between the vacuum interrupter and the buffer layer, and the buffer layer and epoxy resin. There should be no air gap, otherwise it is easy to cause insulation breakdown.

7. Long life

    On-board switches and circuit breakers frequently operated for electric arc furnaces require a mechanical life of 100,000 or even 250,000 cycles. With the development of new operating mechanisms such as permanent magnet mechanisms, improvements in bellows manufacturing technology, and optimization of vacuum interrupter assembly processes, long-life mechanisms and vacuum interrupters have been developed one after another, although 10 million mechanical life The vacuum interrupter has passed the type test, but there is still a lot of work to be done in the long-life vacuum interrupter. First of all, we must ensure consistency, and secondly, we must march towards higher life requirements to meet market needs.

8. Specialization

    In today's increasingly segmented market, some dedicated switches have emerged. In view of the fact that the overvoltage caused by the reignition of the vacuum switch when opening and closing the capacitor bank will cause serious harm to the power system, it is necessary to develop a special vacuum switch for opening and closing the capacitor bank. Similarly, in ferroalloy plants, switches used in arc smelting furnaces require relatively high operating overvoltages and harsh operating environments, requiring high insulation levels between the poles and the ground, low overvoltages, and long service life of vacuum switches. It is necessary to develop new vacuum switches and vacuum interrupters for ferroalloy plants.