Recently, the "UHV ±800kV DC transmission project" project won the special prize of the National Science and Technology Progress Award. This is not only the affirmation of UHV technology, but also the affirmation of the staff who have struggled in the front line of the power grid for many years. As the world's first transmission technology, the "UHV ±800kV DC transmission project" project is the world's highest transmission technology with the highest voltage level, the largest transmission capacity, the longest transmission distance and the most advanced technology. At present, China's UHV technology has become a global leader and has become a golden business card for “Created in China†and “China Leadsâ€.
Break the technical bottleneck
Before the UHV technology, the state of electricity consumption in our country has long been in the mode of “where electricity is needed, where is the power plant builtâ€, which not only caused the tension of coal, electricity and oil transportation, but also brought a lot of pollution. In addition, due to the extremely uneven distribution of resources and power load in China, more than 80% of energy resources are distributed in the west and north, and more than 70% of electricity consumption is concentrated in the central and eastern regions. As a result, how to transport the surplus power resources in the northwest region to the central and eastern regions has become an urgent problem to be solved.
According to Li Lizhen, the first accomplished person of the UHV ±800kV DC transmission project and the director of the Expert Committee of China Southern Power Grid Corporation, before the advent of UHV technology, the scale development of hydropower stations such as Xiangjiaba and Xiluodu in the lower reaches of the Jinsha River made China face closer. The problem of long-distance transportation of 40 million kilowatts of hydropower. Practice has found that the technology of AC transmission scheme is not feasible. At the time, the most advanced ±500 kV DC transmission technology can only transport 3 million kilowatts of electricity per revolution, requiring at least 13 times, and the DC transmission scheme covers a large area. High loss and extremely uneconomical. In this context, since 2004, Academician Li Lizhen began to preside over the construction of UHV ±800kV DC transmission project.
It is reported that at that time, our country's ±500 kV DC transmission engineering technology needs to be introduced from abroad, and various technical barriers were encountered in the course of practice. From ±500 kV to ±800 kV DC transmission, there are no products and experiences that can be borrowed at home and abroad. It faces four major challenges: insulation physical characteristics under ultra-high voltage and high current, electromagnetic environment, equipment development and system control. And puzzles. Therefore, in the process of R&D and construction, this difficult and great project has been slowly advocating the sound, and it has been completed and operated. Many people still cannot believe it.
Six years later, China's UHV ±800kV DC transmission demonstration project “Yunnan-Guangdong†and “Xiangjiaba-Shanghai†were put into operation. It is reported that the transmission capacity of these two projects can reach 5-10 million kilowatts per time, and the transmission distance exceeds 2,000 kilometers, has been operating stably and reliably for more than seven years.
Relevant data show that the transmission capacity of UHV DC project is 2-3 times of ±500 kV DC project, the economic transportation distance is increased by 2-2.5 times, the transmission capacity per unit corridor is increased by 40%, and the unit transportation distance loss is reduced by 45%. The capacity cost is reduced by 28% and the forced energy unavailability is reduced by 80%.
Liu Zehong, deputy general manager of State Grid Corporation, said that as a "electric artery" connecting China's energy base and load center, the UHV ±800kV DC transmission project can transport 240 million kWh a day, equivalent to 1200 100-ton trucks. From China's creation to China's leadership, UHV DC transmission technology is of great significance for accelerating China's energy transformation and upgrading.
Golden business card "going out"
At present, after nearly 10 years of development, China has basically completed the construction of the backbone network of UHV DC transmission projects, and has successively built 13 UHV DC projects, except for Yunnan-Guangdong and Xiangjiaba-Shanghai, which were first built in 2010. In addition to the 800 kV UHV DC transmission demonstration project, there are also Jinping-Sunan, Haminan-Zhengzhou, Xiluodu-Zhexi, Ningdong-Zhejiang, Jiuquan-Hunan, Jinbei-Jiangsu, Ximeng - Taizhou, Shanghai Temple - Shandong, Zalute - Qingzhou ± 800 kV UHV DC transmission project, and Yunnan Pu'er-Guangdong Jiangmen, Guangdong-Guangdong-Guangdong ± 800 kV UHV DC transmission project in the South Network operation area.
According to statistics, these UHV DC projects have a cumulative commutation capacity of 220 million kilowatts, a line length of 25,000 kilometers, a total transmission capacity of 110.6 million kilowatts, and more than 80% of the delivered electricity is clean energy. On this basis, the development of China's UHV technology is still in the process of continuous innovation and development. The Changji-Guquan ±1100 kV DC transmission project currently under construction spans 6 provinces with a transmission capacity of 12 million kilowatts and a total length of 3324. Kilometer is the UHV transmission project with the highest voltage level, the largest transmission capacity, the longest transmission distance and the most advanced technology level in the world.
As a globally leading technology, UHV engineering solves the problem of domestic power transmission, and it is also promising internationally. It is now going global like a high-speed rail. Li Lizhen believes that the UHV "going out to sea" can alleviate the relative saturation of the market to a certain extent, especially in terms of cooperation with countries along the "Belt and Road".
In recent years, China has successfully won the bid for the first and second phases of the ±800 kV UHV DC transmission of the beautiful mountain hydropower station in Brazil, achieving the dual output of UHV DC technology and equipment. The first phase of the Meishan project was put into operation in December 2017. It is reported that, similar to China's energy distribution, Brazil has a vast territory, 80% of the electricity load is concentrated in the developed areas of the southeast, while power generation resources are concentrated in the northern Amazon basin, and the distribution of supply and demand is extremely uneven. Relying on the experience of China's "West-to-East Power Transmission", UHV will perfectly solve the problem of power transmission in Brazil.
In addition, UHV technology is one of the core technologies for promoting the global energy Internet in China. The Global Energy Internet is a strong smart grid with a UHV grid as the backbone network and a global interconnect. The development of UHV and smart grid is the foundation of the global energy Internet. The "going out" of UHV technology in China will greatly promote China's global energy Internet.
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