Reflections on China's UHV Power Grid Construction

During the “Eleventh Five-Year Plan” period, China’s electric power industry continued to develop rapidly. The scale of power supply and power grids ranked second and first in the world respectively, rapidly reversed the situation of electricity shortage across the country during the “10th Five-Year Plan” period, and satisfied the economic development. Strong demand for electricity. However, on the whole, the contradiction between China's energy resources and the reverse distribution of energy demand is still prominent. The task of optimizing the allocation of energy resources across regions is still arduous. In order to build a safe, economical, clean, and sustainable energy supply system, ensure long-term and stable power supply, and accelerate the construction of UHV power grids, it has become one of the major tasks for power development during the “Twelfth Five-Year Plan” period.

At present, UHV power grid as an advanced transmission technology has attracted the attention of all parties in society. During the two sessions this year, accelerating the construction of UHV power grids has become the focus of attention and discussion of many people’s congress representatives. Over 30 percent of representatives of the power industry have submitted proposals, proposals, and proposals for accelerating UHV and smart grid construction and optimizing resources allocation. The Resolution on the Twelfth Five-Year Plan Outline for National Economic and Social Development passed on March 14, 2011, also pointed out that we must speed up the construction of the modern power grid system, further expand the scale of West-to-East power transmission, and improve the regional backbone network. Develop high-capacity, high-efficiency, long-distance advanced transmission technologies such as UHV, rely on advanced technologies such as information, control, and energy storage to promote the construction of smart grids, strengthen the construction and transformation of urban and rural power grids, and enhance the optimization of power grids and power supply reliability for power grids. In order to meet the requirements of large-scale cross-regional transmission and new energy generation and grid connection. This will increase UHV construction into a national strategy and create a favorable external environment for accelerating the UHV grid construction.

I. What is the UHV grid?

Transmission voltage is generally divided into high voltage, ultra high voltage and UHV. High voltage usually refers to a voltage of 35-220kV; ultrahigh voltage generally refers to a voltage of 330kV or more and 1000kV or less; and UHV AC refers to a three-phase AC power transmission method with a rated voltage of 1000kV or more. UHVDC refers to a voltage of ± 750kV and above DC transmission methods. The UHV power grid refers to a modern large-scale power grid with a stratified, partitioned, and clear structure consisting of a 1000KV transmission grid as a backbone grid, an ultra-high voltage transmission grid and a high-voltage transmission grid, and UHV DC transmission, HVDC transmission and distribution networks.

The UHV power grid represents the world's highest voltage transmission technology and has the outstanding advantages of long-distance, large-capacity, low-loss, and high-efficiency power transmission. It is called the "electricity highway." After engineering verification, the transmission capacity of the 1000 kV UHV AC project is 4-5 times that of the 500 kV line; the comprehensive loss, corridor width, and project cost of the unit transmission capacity are 33% and 40% of the conventional 500 kV transmission respectively. And 73%. The transmission capacity of the ±800 kV UHVDC project is 2.5 times that of the ±500 kV DC project. The combined loss, corridor width and project cost of the unit transmission capacity are only 39%, 73% and 72% of the ±500 kV DC project respectively. %.

Second, China's UHV power grid construction status

China's research on UHV transmission technology began in the 1980s. In 1994, Wuhan High Voltage Research Institute built China’s first line of one million volt UHV transmission lines. With the nationwide networking needs and the implementation of the West-East Electricity Transmission Strategy, long-distance, large-capacity transmission has become an inevitable choice for the optimal allocation of resources in China. On December 27, 2004, at the State Grid Party Group Meeting, the construction of the UHV was first proposed. The strategic idea of ​​a strong national grid with grid as its core. During the “Eleventh Five-Year Plan” period, China’s UHV power grid construction achieved a breakthrough. By the end of “Eleventh Five-Year Plan” period, the lengths of ±800 kV UHV DC and 1000 kV UHV AC voltage lines were respectively 3282 km and 640 km.

Among them, the Jindongnan-Nanyang-Jingmen UHV AC pilot demonstration project is the first UHV transmission line in China. Since the project was put into commercial operation on January 6, 2009, it has undergone freezing, lightning, heavy rain, high winds, and high temperatures. In response to the meteorological and climatic conditions, the cumulative transmission of electricity exceeded 20,900 million kwh, among which, sending more than 13 billion kilowatt-hours of thermal power to Huazhong in North China was equivalent to over 4.2 million tons of coal transported; more than 7.9 billion kilowatts of hydropower was sent to Huabei in Central China. At that time, it was equivalent to reducing the burning of coal by more than 255 million tons.

In addition, the Yunnan-Guangdong UHV DC transmission project completed and put into operation on June 18, 2010 in China is the world’s first ±800 kV DC power transmission project, and it is also the world’s highest voltage level HVDC transmission project, according to engineering design indicators. The transmission capacity of this project is 5 million kilowatts, which is equivalent to about twice the 500 kV UHV DC line. According to the calculation of replacement of coal-fired power plants, about 17.6 million tons of carbon dioxide emissions will be reduced annually. On July 8, 2010, Xiangjiaba-Shanghai ±800kv UHVDC transmission demonstration project was put into operation, marking the completion of China's “Green Energy Grand Passage”. It is understood that under the same conditions, the line resistance loss of the project is about 40% of the ±500 kV DC project, and the maximum transmission power accounts for about 1/3 of the Shanghai peak load, and it can deliver about 32 billion kwh per year to Shanghai. Electricity can save about 16 million tons of raw coal and reduce carbon dioxide emissions by more than 30 million tons.

On the whole, as China’s UHV AC/DC transmission projects are put into operation one after another, it has laid a foundation for the balanced transformation of power distribution from the local balance to the country and beyond, and fundamentally solved the long-standing tension in coal and electricity transportation. The solid foundation has played an important role in promoting the transformation of power development mode. At the same time, through the construction of UHV AC/DC transmission projects, the domestic production and technical level of power transmission and transformation equipment and localization capabilities have also been continuously improved, and accumulated rich experience and research results for the independent development of UHV transmission technologies. At present, China has comprehensively conquered the world's major problems in the UHV AC/DC frontier areas and seized the commanding heights. It has taken the lead in international research in theoretical research, engineering construction, operation management, testing capabilities, and standard setting. China has laid a solid foundation from a big power country to a powerful power science and technology country; at the same time, China has already possessed the comprehensive capabilities of production and system integration of a full set of UHV DC key equipment, which has significantly improved the independent innovation capability and core competitiveness of China's electrical equipment manufacturing industry. It has created conditions for the industrial upgrading and leap-forward development of China's electrical equipment manufacturing industry.

Third, the significance of China's construction of UHV power grid

UHV power grid construction, give full play to UHV transmission technology in long-distance, large-capacity, low-loss power transmission and other advantages, not only can achieve the optimal allocation of resources across the country, but also can guide the optimization of power distribution, promote the coordinated development of the regional economy At the same time, the construction of ultra-high voltage power grids can promote the development and utilization of clean energy, and it is conducive to the adjustment of power supply structure and the transformation of power development methods.

First of all, the construction of UHV power grids is an effective way to achieve optimal allocation of resources and solve the bottleneck of energy constraints in China's economic development. It is of great significance to ensure energy security and the healthy and sustainable development of the national economy.

On the one hand, from the perspective of the distribution of energy resources in China, 76% of China's coal resources are located in the north and northwest; 80% of hydropower resources are distributed in the southwestern part of the country; the vast majority of terrestrial wind and solar energy resources are distributed in the northwest; At the same time, over 70% of energy demand is concentrated in the eastern and central regions. With the acceleration of the construction of large coal-fired power stations, large hydropower stations, large nuclear power stations, and large-scale clean energy bases, it is urgently necessary to accelerate the construction of UHV power grids to realize large-scale, cross-regional, long-distance transmission of energy resources in China.

On the other hand, the characteristics of coal-based energy resources in China determine that China's coal-based power supply structure will be difficult to change for a long time. At present, 80% of China’s electricity is generated from thermal power. More than half of the coal transported by China’s railways and highways is electric coal, which brings tremendous pressure on the transportation sector. If we can convert a part of the coal into local production sites, For electric energy, it is transmitted to consumer sites through UHV to realize simultaneous coal transportation and transmission. This not only can effectively ease the tight situation of coal and electricity transportation, but also fundamentally solve the problem of tight supply of electric energy in the central and eastern regions. It can also significantly reduce the coal transportation process. Environmental pollution and waste of resources to promote the sustained and healthy development of the national economy.

Secondly, the construction of ultra-high voltage power grids and the transformation of China's energy transportation methods will reorient the distribution of the power industry and help promote the coordinated development of the regional economy.

On the one hand, from the perspective of areas where electricity is exported, by increasing the construction of power plants and accelerating the development of transmission, it is possible to promote the export of high-value-added power products in the region, increase the return rate of resources and production factors in these areas, and increase employment opportunities. The region’s advantages in energy resources have turned into advantages in economic development, inject new vitality into local economic development, and narrow the gap between regions. On the other hand, because the electricity-receiving regions receive clean power, this will reduce the construction of local coal-fired power plants, thereby reducing the pressure on the environment to a greater extent, which will be conducive to the transformation of the economic development mode of the power-receiving areas; In terms of power-receiving regions, the UHV power grid can significantly reduce the power supply cost, thereby increasing the competitiveness of local products and promoting the rapid development of the local economy.

In addition, the construction of UHV power grids can greatly increase the capacity of clean energy absorption, promote the accelerated development and full use of clean energy, and promote the optimization of power supply structure adjustment and the transformation of power development mode.

According to the plan of the State Grid, in 2015, the proportion of clean energy installed in the operating area of ​​the State Grid reached 29.2%, of which non-water renewable energy was 11.1%; the proportion of power generation reached 20.2%, of which non-water renewable energy was 8.2%. In 2015, the share of clean energy production in primary energy consumption increased from 6.8% in 2005 to 11.1%, of which non-water renewable energy increased from 0.3% in 2005 to 4.5%. As a whole, China’s clean energy development is mainly concentrated in the northwestern region, and the local capacity for digesting and absorbing electricity is limited. Long-distance transmission and large-scale absorption capabilities of UHV power grids can effectively solve the problem of difficult access to clean energy such as wind power. Provide support for cross-regional transfer of clean energy, thus promoting the optimization of power supply structure adjustment and the transformation of power development mode.

At present, China has made some important scientific research achievements in the UHV field and has trained a large number of technical experts with high theoretical level and rich practical experience. This has provided the technical basis for the construction of UHV power grids; at the same time, the level of our country’s electrical equipment industry continues to increase. In particular, it has strong independent R&D and innovation capabilities in the production of power transmission and transformation equipment, providing the equipment foundation for the construction of UHV power grids. In general, China already has the conditions for the large-scale construction of UHV power grids. Under the impetus of the 12th Five-Year Plan, China’s UHV power grid construction will usher in a broad space for development.