Energy is the foundation of economic development. In the past ten years, China's energy independence guarantee capability has been significantly improved, and the world's largest clean power generation system has been built. The energy structure has been continuously optimized, which has effectively guaranteed the stable operation of the national economy.
In recent years, China has gradually developed and grown in the fields of electrical engineering and power technology. After more than 60 years of development, China now has the most powerful power industry system in the world: in 2021, the country's installed power generation capacity will be about 2.38 billion kilowatts, ranking first in the world; Take the central enterprise State Grid as an example, it currently has more than 20,000 patents, ranking third in the world; the number of patents in energy storage batteries alone accounts for 67.56% of the world's total; at the same time, China is also the world's largest power exporter.
Especially in the field of UHV transmission technology, the most advanced power transmission technology in the world, China has mastered UHV transmission technology with independent intellectual property rights, which is a major independent innovation achievement leading the world. It has taken the lead in formulating international public UHV transmission line standards, so that Chinese standards and world standards are equated.
▲ Chizhou, Anhui Aerial Photography UHV Line Jiuhua Dense Channel (Image source/Visual China)
What is UHV power transmission
In China’s power grid operation system, the voltage is divided into two systems: transmission and distribution. The transmission system is for the purpose of transporting power to substations of the same level or lower level, and the general voltage level is higher. The purpose of the distribution system is to transmit power to the distribution load, and the general voltage level does not exceed 110kV.
Simply put, from the power plant to the boost substation, the transmission network is the transmission system; from the step-down substation to the distribution network to the TV, air conditioning and other electrical equipment is the distribution system.
According to Ohm's law, the current will be lost during the transmission process. Distance and materials are important reasons for the loss, especially the transmission distance. The farther the loss is, the greater the loss. One of the ways to reduce the transmission loss is to increase the transmission voltage, so there is the concept of high voltage electricity.
In China, the high-voltage power grid refers to the 220kV power grid. The ultra-high voltage developed on the basis of high-voltage electricity can reach 500kV. But even so, the ultra-high-voltage DC transmission technology is still not enough to deal with the long-distance transmission of thousands of kilometers, and the current loss can even reach 20% or more.
Continuing to increase the voltage of HVDC transmission, which cannot be tolerated by traditional insulating materials, will lead to the failure of the power grid system and increase the risk of accidents such as fires, which requires UHVDC transmission technical support.
UHV technology refers to power transmission technology with AC 1000kV and DC ± 800kV voltage levels. The biggest feature of this technology is that it can achieve long-distance and efficient power transmission, especially for countries with vast territory, large population or uneven distribution of regional resources. It is more like "sending carbon in snow", also known as "5G network in the electrical field" and "high-speed railway in the power system".
According to the data provided by the State Grid Corporation of China, the first-loop UHVDC power grid can send 6 million kilowatts of electricity, which is equivalent to 5-6 times that of the existing 500kV DC power grid, and the power transmission distance is also 2 to 3 times that of the latter, and can save 60% of land resources.
▲ Schematic diagram of UHV power transmission (picture source/Wall Street News)
From self-made to self-reliance
In fact, China's development of UHV transmission is also a "helpless move", because China's basic national conditions determine the extremely unbalanced geographical distribution of electricity production and consumption.
Two-thirds of the country's coal resources are concentrated in the three provinces and regions of Shaanxi, Shanxi and Inner Mongolia, 80% of hydropower resources are concentrated in the southwest, and photovoltaic and wind energy resources are mainly concentrated in the northwest, Inner Mongolia and other places. However, the 16 provinces in the central and eastern regions with the most densely populated and the highest demand for electricity are the 16 provinces in the central and eastern regions, which leads to a large demand for long-distance power transmission. Power technology is not only a scientific issue, but also an important guarantee for China's energy security.
Unlike "traditional advantage" fields such as bridges and civil engineering, China does not have much technical reserves in power transmission technology, and it is basically self-made. So until the early stage of reform and opening up, power cuts were common in various places due to insufficient power supply.
In order to solve the problem of power supply, in the 1980s, China introduced power transmission and transformation technology with a voltage level of 500kV from the West (previously 220kV ordinary power transmission in most areas). But with the rapid development of the economy and society, the 500kV power transmission technology has also encountered the ceiling of supply and demand, and it is necessary to continue to increase the transmission power and enter the UHV field.
In the field of energy, UHV transmission has always been a world-class problem. The United States, the Soviet Union, Japan, Italy and other countries have all carried out UHV research and tests, equipment development and engineering attempts, but due to political, economic, technological and other factors, they all ended in failure.
Since 2000, relevant departments have organized dozens of scientific research institutions and universities, and hundreds of equipment manufacturing enterprises, forming thousands of sets of plans, with a total of hundreds of thousands of people participating. Under the circumstance of "no standards, no experience, and no equipment" in the world, many world-class problems of UHV transmission technology have been overcome.
The ± 800kV UHVDC converter transformer independently developed by China has created a world record with the largest single capacity, the highest technical difficulty and the shortest output time in the world.
The conductivity of UHV energy-saving conductors developed by China improved technology has increased from 61.0% IACS (conductivity, which is a measurement value indicating the strength of material transmission current capacity) to 63.5% IACS, which greatly reduces the loss in the process of UHV power transmission, and can reduce power transmission losses by billions of degrees every year.
▲ On June 26, 2022, in Chongqing, at the construction site of the Chongqing Qianjiang section of the Baihetan-Zhejiang ± 800kV UHVDC transmission project, workers carried out aerial work at a height of more than 100 meters (Image source/Vision China)
These scientific and technological innovation achievements are inseparable from the attention of relevant state departments, and even more inseparable from the hard work of countless scientific researchers, carrying forward the scientific spirit of truth-seeking innovation and hard work. For example, Li Lixuan, an academician of the Chinese Academy of Engineering, is an expert in the field of UHVDC transmission in China and is known as the "first person in DC transmission". In UHV ± 800kV DC technology, he led experts and teams to overcome difficulties, developed 73 major electrical equipment in 13 categories, obtained 141 key technologies, created 37 world firsts, and became one of the main promoters of my country's "leading the world" in this field.
Chen Weijiang, an academician of the Chinese Academy of Sciences, is an expert in high voltage and insulation technology. He has won the National Science and Technology Progress Award and the Second Prize of the National Technology Invention Award. He has been engaged in the research on electromagnetic transient analysis methods and protection technology of power systems for a long time. These scientific research achievements have effectively supported the successful research and development of my country's UHV power transmission technology.
Founded in 1981, the China Electrotechnical Society is an academic group organization with electrical engineers and electrical science and technology workers as the main body, and is also an important social force in the development of China's electrical engineering undertakings. The Society adheres to academic exchanges as the center, faces the frontiers of electrical technology and the needs of national economic construction, and actively conducts academic exchange activities. In the "Guide to Important Academic Conferences (2022) " of the China Association for Science and Technology, a total of 8 conferences from the China Electrotechnical Society are included, such as the Academic Annual Meeting of the China Electrotechnical Society, the 5th International Electrical and Energy Conference, and the China branch of the World Electric Vehicle Conference. Meetings are all academic conferences with greater influence and a large number of participants.
New opportunities in the context of "dual carbon"
In 2009, China's first UHV transmission line, Jindongnan-Nanyang-Jingmen, was fully connected, and China became the first country in the world to fully master UHV transmission technology and put it into business operations.
Since then, more than ten years, China's UHV transmission technology has made a historic breakthrough: by the end of 2021, a total of 33 UHV lines have been put into use in my country, covering seven major power grid areas in the country. The transmission line project is close to 40,000 kilometers, which is equivalent to going around the earth.
Technological leadership has given China more voice over. At present, in the field of UHV technology, China has taken the lead in formulating international UHV transmission line standards and has full patent rights. This means that even if other countries have developed domestic technology, they must abide by Chinese standards before they are allowed to sell it internationally.
China has successively cooperated with the Philippines, Portugal, Australia, Greece, Russia and other countries to start the global layout of UHV power transmission. 168 countries around the world have signed cooperation agreements with State Grid in the field of technology, which means that China's UHV technology has begun to go abroad and go to the world.
Under the background of "carbon peaking and carbon neutrality", the power system is now facing a profound revolution, and UHV technology has also reached a new intersection.
In the future, with the decline in the proportion of traditional thermal power and the increase in the proportion of wind power and solar green power and clean energy, the traditional "power generation, transmission, transformation, distribution and electricity consumption" model will change accordingly, which will also bring more opportunities and challenges to the development of China's power engineering industry.
On the one hand, as a carrier for remote power transmission in the process of carbon neutrality, UHV technology is an important support for ensuring energy security and accelerating the realization of the "double carbon" goal, balancing energy and load distribution, and promoting new energy consumption.
On the other hand, UHV projects can also effectively drive local economic development. According to estimates, during the "14th Five-Year Plan" period, the DC delivery channels in Northeast China, Mengxi, Shanxi, Northwest China, Southwest China and other regions need to increase the transmission capacity by 84.52 million kilowatts, and the new UHVDC project investment is about 260 billion yuan, which will play a positive role in promoting the development of upstream and downstream industrial chains. UHV is expected to continue to accelerate development and usher in greater growth space.