From power outages to world standards, this technology opens up the "high-speed railway" of electricity

From power outages due to poverty to 24-hour bright lights, this technology has opened up the "high-speed railway" of electricity. With independent intellectual property rights, Chinese standards are equated with world standards.

Written by reporter Zhao Tianyu Edited by Liu Zhao

New Media Editor/Fang Yongzhen

Audit Expert

Ma Jing (Professor and doctoral supervisor at the School of Electrical and Electronic Engineering, North China Electric Power University, and deputy director of the Youth Work Committee of the China Electrotechnical Society)

Energy is the cornerstone of economic development. In the past decade, my country's energy self-sufficiency has been significantly improved, the world's largest clean power generation system has been built, and the energy structure has been continuously optimized, which has effectively guaranteed the stable operation of the national economy.

In recent years, China has gradually grown and developed 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 was approximately 2.38 billion kilowatts, ranking first in the world; taking the state-owned 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; at the same time, my country is also the world's largest electricity exporter.

Especially in the field of ultra-high voltage transmission technology, the world's most advanced power transmission technology, my country has mastered ultra-high voltage transmission technology with independent intellectual property rights, which is a major independent innovation achievement leading the world. It has taken the lead in formulating internationally used ultra-high voltage transmission line standards, making Chinese standards equal to world standards.

What is UHV transmission?

In my country's power grid operation system, the voltage is divided into two systems: transmission and distribution. The purpose of the transmission system is to transmit power to the substation of the same level or lower level, and the voltage level is generally higher. The purpose of the distribution system is to transmit power to the distribution load, and the voltage level generally does not exceed 110kV.

Simply put, the transmission system is from the power plant to the step-up substation and the transmission network; the distribution system is from the step-down substation to the distribution network and then to electrical equipment such as televisions and air conditioners.

According to Ohm's law, current will be lost during transmission. Distance and materials are important causes of loss, especially the transmission distance. The longer the transmission distance, the greater the loss. One way to reduce transmission loss is to increase the transmission voltage, so the concept of high voltage came into being.

In my country, high voltage grid refers to 220kV grid. The ultra-high voltage developed on the basis of high voltage can reach 500kV. But even so, ultra-high voltage direct current transmission technology is still not enough to cope with long-distance transmission of thousands of kilometers, and the current loss can even reach 20% or more.

If the voltage of DC transmission is further increased, traditional insulation materials will not be able to withstand it, which will cause power grid system failures and increase the risk of accidents such as fire. This requires the support of ultra-high voltage DC transmission technology.

Ultra-high voltage technology refers to power transmission technology with voltage levels of 1000kV AC and ±800kV DC. The biggest feature of this technology is that it can achieve long-distance and efficient power transmission, which is especially helpful for countries with vast territories, large populations, or uneven regional resource distribution. It is also known as the "5G network in the electrical field" and the "high-speed railway in the power system."

Data provided by the State Grid Corporation of China shows that a single-circuit ultra-high voltage direct current grid can deliver 6 million kilowatts of electricity, which is 5-6 times the capacity of the existing 500kV direct current grid. The transmission distance is also 2 to 3 times that of the latter, and it can save 60% of land resources.

▲Schematic diagram of ultra-high voltage power transmission (Photo source: Wall Street Journal)

From starting from scratch to becoming self-reliant

In fact, China's development of ultra-high voltage power 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 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 and Inner Mongolia. However, the 16 provinces in the central and eastern parts of the country have the highest population density and electricity demand, 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 my country's energy security.

Unlike the "traditional advantage" fields such as bridges and civil engineering, China does not have much technical reserves in power transmission technology and basically started from scratch. Therefore, until the early days of reform and opening up, power outages were common in various places due to insufficient power supply.

In order to solve the problem of power supply, my country introduced 500kV power transmission and transformation technology from the West in the 1980s (most areas previously used 220kV ordinary power transmission). However, with the rapid development of the economy and society, 500kV power transmission technology has also encountered a supply and demand ceiling, and it is necessary to continue to increase the power transmission capacity and advance into the UHV field.

In the energy field, ultra-high voltage transmission has always been a world-class problem. Many countries have carried out ultra-high voltage research and experiments, equipment development and engineering attempts, but due to political, economic, technical 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 companies, to develop thousands of plans, with hundreds of thousands of people participating. In the absence of "no standards, no experience, and no equipment" internationally, they have overcome many world-class challenges in ultra-high voltage transmission technology.

The ±800kV ultra-high voltage direct current converter transformer independently developed by my country has set a world record for the largest single capacity, the highest technical difficulty and the shortest production time.

The conductivity of the ultra-high voltage energy-saving conductors developed by my country with improved technology has been increased from 61.0%IACS (conductivity is a measurement of the ability of a material to transmit electric current) to 63.5%IACS, which has greatly reduced losses in the ultra-high voltage transmission process and can reduce power transmission losses by billions of kilowatt-hours each year.

These scientific and technological innovations are inseparable from the attention of relevant national departments, and even more so from the hard work of countless scientific researchers, who have carried forward the spirit of scientists who seek truth, innovation and hard work. For example, Li Lixuan, an academician of the Chinese Academy of Engineering, is an expert in the field of UHV DC transmission in China and is known as the "first person in DC transmission". In terms of 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 Special Award and the National Technological Invention Second Prize. He has been engaged in the research of electromagnetic transient analysis methods and protection technologies for power systems for a long time. These scientific research results have effectively supported the successful development of my country's ultra-high voltage transmission technology.

Founded in 1981, the Chinese Electrotechnical Society is an academic group organization composed of electrical engineers and electrical science and technology workers. It is also an important social force in the development of China's electrical engineering. The society insists on academic exchanges as the center, facing the needs of the frontiers of electrical technology and national economic construction, and actively carries out academic exchange activities. The China Association for Science and Technology's "Guide to Important Academic Conferences (2022)" includes a total of 8 conferences from the Chinese Electrotechnical Society. Conferences such as the Chinese Electrotechnical Society Academic Annual Conference are academic conferences with great influence and a large number of participants.

▲For more information about the "Guide to Important Academic Conferences (2022)", please scan the QR code

New opportunities under the background of "dual carbon"

In 2009, my country's first ultra-high voltage transmission line, Southeast Shanxi-Nanyang-Jingmen, was fully opened, making China the first country in the world to fully master ultra-high voltage transmission technology and put it into commercial operation.

In the more than ten years since then, my country's ultra-high voltage transmission technology has made another historic breakthrough: as of the end of 2021, a total of 33 ultra-high voltage lines have been put into use in my country, covering the country's seven major power grid areas, and the transmission line project is close to 40,000 kilometers, equivalent to one circle around the earth.

The technological leadership has given China more say. Currently, in the field of UHV technology, China has taken the lead in formulating the international public UHV transmission line standards and has the right to use all patents. This means that even if other countries develop domestic technologies, they must comply with China's standards before they are allowed to sell them internationally.

China has cooperated with the Philippines, Portugal, Australia, Greece, Russia and other countries to start the global layout of UHV transmission. 168 countries around the world have signed technical cooperation agreements with State Grid, which means that China's UHV technology has begun to go abroad and to the world.

Under the background of "dual carbon", the power system is now facing a transformation, and ultra-high voltage technology has also come to a new crossroads.

In the future, as the proportion of traditional thermal power decreases and the proportion of wind power, solar power and clean energy increases, the traditional "power generation, transmission, transformation, distribution and consumption" model will change, 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 long-distance electricity transmission in the process of carbon neutrality, ultra-high voltage technology is an important support for ensuring energy security and accelerating the realization of the "dual carbon" goals, and it plays a role in balancing energy and load distribution and promoting the consumption of new energy.

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 transmission channels in Northeast my country, Western Inner Mongolia, Shanxi, Northwest China, and Southwest China need to increase their transmission capacity by 84.52 million kilowatts, and require new UHV DC project investment of 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 its development and usher in greater growth space. ■