Applying superconducting technology to power systems, it is possible to obtain a number of performance superconducting generators and superconducting transformers that cannot be or are difficult to achieve using conventional techniques, both in terms of device characteristics and system characteristics, to provide active and reactive power to the system. The response capacity opens up new ideas for the stability control of the power system. The superconducting energy storage device for the load side can improve the power supply quality and provide emergency backup power. However, the practical application of superconducting power itself has several problems to be solved. This needs further development of technology. At the same time, the development of superconductivity also needs to solve a number of non-technical problems. 1 Key issues in superconductivity science and technology. 1.1 Basic problems to be solved in superconductivity. Superconductivity is widely used in power systems. Technology must study the four basic problems of economy, technical superiority, compatibility with current technology, safety and reliability. For economic and technological superiority, it should be viewed from two aspects: superconductivity should be considered. The economics of superconducting technology for power plants should pay more attention to the introduction of superconducting technology in the power system. Overall economic benefits and technological superiority At present, the price of high-temperature superconducting wire is still relatively expensive, and the technical parameters need to be further improved. Therefore, the international prediction of superconducting technology in the power system is practical: 2000-12- ) 6 paragraphs. The journal will continue to pay attention to the research and development of superconducting power technology at home and abroad, and report the latest research results and developments in a timely manner. I believe in research. Production operation. With the joint efforts of the majority of science and technology workers in the management and other departments, superconducting technology will play an important role in the future power system with its unique performance. The application also takes 5 to 10 years. The research results of Nagoya University show that when superconducting cable technology is used in the metropolitan power grid, although the operating cost of the superconducting cable itself is relatively high, due to the high-capacity high-density transmission, Improve and optimize the network structure and power flow distribution of the metropolitan power grid, so that the network loss of the whole system can be reduced. The other is the conventional protection problem of the system after applying the superconducting device in the power system. 1.6.1 Loss in the superconducting power system Ultra-protection can also cause the "constrained problem of superconductor J. Therefore, it must carry out fciSh! system failure, which will seriously affect the power supply reliability of the system. Even the bookmark1 superconducting device can only operate below the critical temperature, and the magnetic field and the field The passing current should not exceed its critical value, otherwise the superconductivity will be lost, that is, the quench will occur. The hazard of the quench is huge. First, the superconducting device has a large power transmission capacity, and serious quenching will lead to power application. It can be said that it has just started, the Chinese wrong hospital is involved in the electrical power system from the power generation to the stability of the system, followed by the superconducting The heat generated inside the chamber may burn the superconductor in the device, and may also cause the expansion of the volume of the cooling medium to abruptly expand until the entire device is damaged (the main cryogenic cooling medium volume change is: 4.2K liquid helium evaporation, the volume is 8 times larger, After 100K liquid helium gas is evaporated, the volume is 530 times larger; after 77K liquid nitrogen evaporation, the volume is 182 times larger, and after 100K liquid nitrogen is evaporated, the volume is 250 times larger. Third, there are many factors affecting the superconductor critical value, only from the surface. There are three critical values, and the three critical values ​​are related to each other, and each is also affected by several factors, such as AC loss inside the superconductor, mechanical vibration of the magnetic flux jump, cooling stress, etc., which may lead to a decrease in the critical value, so The quench protection of the guiding device is a rather complicated problem. Fourthly, the quenching will also lead to the occurrence of concurrent failures such as overvoltage and insulation level. The super-conductivity in the superconducting force system should be studied from three aspects. :1 Starting from the superconducting wire, the meticulous study of the quench phenomenon is the basis of the quench protection, and the 2 super-protection of the superconducting device, including How to reduce the heat generated after the quench, and transfer the energy in the superconducting device as soon as possible; 3 to ensure the safe and stable operation of the power system after the quench occurs, which is a unique problem of the superconducting force system, and also makes the superconducting force The quench protection has different meanings from the quench protection of general superconducting technology. It is necessary to carry out the dynamic design of the superconducting device based on the full understanding of the dynamic characteristics of the superconducting force system, such as the rated current value of the superconducting device and The operating current value of the protection device, in the system operation management, should also avoid the operation mode that may lead to quenching. 1.6.2 Protection system in the superconducting power system The protection system in the superconducting power system must be completed in the current conventional system. In addition to the protection task, the quench protection of the superconducting device and the quench protection of the whole system are also realized. The superconducting current limiter is one of the main protection devices in the superconducting force system, which can not only limit the short circuit in the system. The current reduces the requirement for the breaking capacity of the circuit breaker and can be used as an overcurrent protection for other important superconducting devices. The system protection of the superconducting current limiter with rapid action and controllable action current value introduced into the superconducting current limiter can be considered as active protection with controllable fault current level. How to coordinate the action of superconducting current limiters and conventional protection systems will be an important research content for the safety protection of superconducting power systems.

2 Views on the development of superconductivity science and technology China's superconductivity application technology research and foreign advanced countries have a large gap between the United States, Japan, Russia, France, Germany, Sweden, Britain, Norway and other countries have developed various types Ultra-conductivity device experimental prototype China's research on the characteristics of superconducting physical materials and foreign countries is not much difference, and some even lead, and there are several research results in general superconducting application technology. However, research institutes and universities such as Tsinghua University of Huazhong University of Science and Technology have begun preliminary research work. The United States, Japan and other countries have invested a large amount of money in superconducting force application technology. In Japan, for example, almost all universities with electrical engineering disciplines are engaged in research on superconducting power applications to varying degrees. The results of Kyushu University Osaka University Nagoya University, Yokohama National University, and Tokyo University are the most significant. Large motor and cable manufacturing companies and power companies have also invested huge sums of money, Toshiba Hitachi, Mitsubishi, Fuji and other motor manufacturing plants, cable factories such as Showa, Sumitomo, Yokogawa, Fujikura, Tokyo Electric Power Company, Chubu Electric Power Company, Kansai Electric Power Company Major power companies such as Kyushu Electric Power Co., Ltd. are involved in the application research of superconducting power.

It should be noted that there is still a broad development space in the research field of superconductivity science and technology. Superconductivity has not yet realized the practical application in the true sense. Even in industrialized countries such as the United States and Japan, the research on superconductivity has been studied so far. The work also basically stays in the trial production and laboratory research stage of the single-machine superconductivity experimental device. The superconducting power has not been mentioned to the subject height for comprehensive research. As long as we lose no time to enter the trend of superconducting force science and technology progress, completely It is possible to form autonomous intellectual property rights to meet the arrival of superconducting power. The realization of superconducting power has yet to be sustained and supported by various aspects. 2.1 Superconductivity requires the country's key support. Superconducting force science and technology, although it has good application prospects, After all, it is still in the early stages of development. In the current stage of research on superconductivity in China, it is still difficult to achieve immediate results, immediately form products, occupy the market, and obtain huge economic returns. Therefore, the development of superconductivity is inseparable from national key investment.

The early superconductivity research work in the United States and Japan was also based on state investment. The Ministry of International Trade and Industry and the New Energy Development Agency included superconducting force application research in the "Sunshine" plan "Moonlight" plan and "New Sunshine" plan. With the support of these programs, the fund has established a joint organization (Super-GM, established in 1988) with the main purpose of developing research and superconducting generators and related technologies, which is centered on state support and participated by several research institutions and enterprises. And the International Center for Superconductivity Research (ISTEC, established in 1991) with the main purpose of developing and researching superconducting magnetic energy storage systems and related technologies. At the same time, it also provides a large amount of support for other superconducting devices. The investment in the superconducting generator superconducting magnetic energy storage partnership initiative research plan, Table 1 is the SPI project superconductivity related projects and investment (both high temperature superconducting), the Ministry of Energy (DOE) investment 50% (data from the Internet) 2.2 Superconductivity requires the support of the industrial sector. From the industrial field, superconductivity requires both the power industry. Love, also need a new technology in the mechanical manufacturing industry, and Table 1 US spi plan main content and investment super-conductivity main technical parameters investment situation million dollars device related enterprises transformer current limit power cable motor magnetic suspension flywheel energy storage The power sector will realize the true application and development when it fundamentally recognizes its necessity and technical economic superiority. Although most of the superconducting devices are similar to the basic principles and structures of conventional devices, they are special electromagnetic due to superconductors. Performance, the design principle of the superconducting device, the manufacturing process, etc. are still the research topics of the manufacturer. Only the manufacturer has mastered the production technology of the mature superconducting device, and there will be a wide range of real applications in Japan. Major power companies, several motor cables and related equipment (such as vacuum cryogenic equipment) manufacturers are not only actively involved in the joint research of Supei.-GM and ISTEC, which are supported by the Ministry of International Trade and Industry or the New Energy Development Agency, and carry out their own research. Research work on several other superconducting science technologies, such as Tokyo Electric Power The company and Sumitomo Electric jointly conducted research and development work on high-temperature superconducting power (000A, 100m). The two sides invested 50% each, a total of 1.8 billion yen (about RMB 13.5 million). The author participated in the full closure of the University of Nagoya, Japan. Research work on superconducting integrated transmission model (superconducting transformer 6000V, 250A, 5m), the project applies for 16 million yen for national research funding, and the central power company supports 20 million yen. Showa wire and cable company can provide superconducting wire. It is said that leaving the support of the power industry and the electrical manufacturing industry, the research on superconductivity science and technology is difficult to carry out. The development of China's superconductivity science and technology needs to be actively participated in the power industry and manufacturing plants, and the challenges are forward-looking. Scientific research topics to form autonomous intellectual property 23 Superconductivity requires a wide range of interdisciplinary superconductivity First of all is the combination of superconducting application technology and power system. The current superconducting technology is inseparable from the low temperature and low temperature technology. It not only provides the most basic operating conditions for superconducting, but also directly relates to the efficiency and safety reliability of superconducting equipment. It is the practical application of superconducting technology to the power system. One of the keys. Superconductivity is inseparable from the most important application areas of superconducting. The two rely on each other and promote each other. It is a typical cross-disciplinary and interdisciplinary topic. The development of new superconducting materials and the research on improving the application performance of superconducting materials are One of the important foundations of superconductivity. Power electronics is an indispensable technical tool when applying superconducting technology in power systems, especially when applying superconducting energy storage systems. It can be seen that the development of superconductivity requires extensive integration of superconducting physical superconducting materials, cryogenic engineering, power electronics, power systems, automatic control, and mechanical manufacturing. Conversely, the development of superconductivity can be triggered not only in the power industry. The technological revolution can also promote the development of several related disciplines. 3 Conclusion In China, because the distribution of energy resources and energy consumption is extremely uneven, the high-voltage long-distance West-East power transmission is inevitable, which makes the system stability problem very Highlighting the long-term power consumption, the scale of the power system is getting larger and larger, and the current-breaking capacity of the circuit breaker has been difficult to meet the requirements of long system short-circuit capacity; excessive short-circuit current has put forward higher electromagnetic force for the power device. Electric and thermal technical indicators use copper and aluminum with electrical resistance as conductive materials, the network loss is huge in large cities, the power consumption density is long, but the power transmission channel is getting more and more tight, and it is difficult to meet the high density of big cities with conventional technology. Large-capacity power transmission requirements Because superconductivity has a resistance of 0 and other superior characteristics, the application of superconducting technology We sincerely hope that superconducting power will become a research hotspot in China's electric power and electrician industry. We hope that through the efforts of the vast number of scientific and technological workers, we will push our superconducting technology from basic theory, basic materials to superconducting force applications to a brand new The level of development has placed China in a favorable position in the technological competition among countries in the 21st century.

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October 28, 2021