The world's "four items first" UHV project will be completed and put into operation by the end of this year

In the wilderness of the hinterland of Asia and Europe, for millions of years, only sparse desert plants and yellow sheep and wild donkeys have cyclically released their vitality as winter goes to spring. But nowadays, the ancient wilderness is very lively, a group of huge silver power towers like a long dragon, lifted from the construction site, holding the thick and thin cable of the arm, relaying all the way from the Junggar Basin in Xinjiang to the east, over the Tianshan, and through The Hexi Corridor, crossing the Yellow River and the Yangtze River, reached the southern part of Anhui.

This "Changlong" is a contracted ± 1100 kV UHV DC transmission project from Zhundong to southern Anhui with the highest voltage level, the largest transmission capacity, the longest transmission distance, and the most advanced technical level in the world. As this project overcomes difficulties and will be completed and put into operation by the end of this year, China's UHV transmission technology has once again attracted widespread attention.

Technological innovation "challenge impossible"

Not long ago, near the Changji converter station in Zhundong Industrial Park, Xinjiang, from the Zhundong to southern Anhui ± 1100 kV UHV DC transmission project, the Xinjiang section with the most varied topography and the most complicated climatic conditions was fully connected.

Entering the construction site is like coming to the “Giant Kingdom”: Both base towers are over 100 meters high, 33 stories high, and the tower weighs more than 400 tons. It is a veritable “Big Mac”; the cables used in the project have the thickness of an adult ’s wrist Each of the "screw nut" and insulated porcelain bottle that fix the cable weighs more than ten kilograms.

In the past two years, the Xinjiang section of the project has conquered the desert and Gobi from the east of the Junggar Basin, crossed the wind zone and the Tianshan Mountains, and erected 1109 base iron towers on the corridor of nearly 600 kilometers.

Compared with the mature 750 kV transmission line, the voltage level is increased to 1100 kV, which means that the tower is higher and the tonnage is heavier, the foundation concrete volume is larger and the difficulty is higher, and there is no precedent for reference. The originality of the project allows Construction workers face unprecedented difficulties.

The Xinjiang section of the route will cross the second largest desert in China-the Gurbantunggut Desert. High temperature exposure and sand storms are not the biggest headache for the construction workers. It is the key for the 400-ton iron tower to "stand up" and the foundation concrete is firm. It is not easy to let the concrete "moisturize" in the desert. The previous "artificial watering method" is difficult and effective.

Under the leadership of Jin Yi, the deputy manager of the new 1st section project, the technical staff of the project team "opened their brains" and thought of "drip irrigation" for water saving in agriculture, which not only solved the problem of "maintenance" of concrete, but also saved water resources. "Concrete strength is guaranteed, and water consumption is only equivalent to 1/6 of the past." Jin Yi said. At present, the concrete drip irrigation maintenance technology in the desert area is applying for a national patent.

Crossing the East Tianshan is another difficulty in the construction of the Xinjiang section. The 60-kilometer section not only covers complex terrain such as high mountains and hills, but is in the seismic intensity zone, and it is in the wind zone of 43 meters per second. At the construction site deep in the Tianshan Mountains, the staff transported the building materials at the foot of the mountain to the tower by cableway, and then assembled the building materials “precisely” on the top of the mountain with a pole. Xu Yubo, deputy manager of the project department of the owner of Xinjiang Section, said that it took 45 days for one of the foundation towers to be assembled.

In order to prevent the solidified concrete "uphill" 15 kilometers away from solidifying, but to solidify within 24 hours after pouring, the construction party also cooperated with scientific research institutions to carry out scientific and technological research, and finally overcome this problem by adding new materials admixtures.

The converter station is the heart of the UHV DC transmission project. The investment in Changji converter station alone reached 8.1 billion. The AC power transmitted by the 7 power plants and the 750-kV substation of Wuwan Bay is converted into DC power here, and the voltage rises to ± 1100 kV before being sent out. Right now, seven converter transformers and two sets of converter valves have been installed.

Yao Bin, deputy manager of Changji converter station owner project of State Grid DC Company, said that the ± 1100 kV converter station represents the highest level of DC transmission technology in the world today, and the technical indicators such as converter capacity and electrical insulation are "tending to the limit" and have been updated. The new height of China's related equipment manufacturing.

From Zhundong to southern Anhui UHV DC transmission project, with a total length of 3,324 kilometers, a total investment of 40.7 billion yuan, the transmission voltage level was increased to 1100 kV, the transmission capacity was increased to 12 million kilowatts, and the economic transmission distance extended to more than 3,000 kilometers. In addition to the penetration of the Xinjiang section, the tower section of the Shaanxi section is currently over half, and the Anhui section has entered the release phase.

The smooth deployment of this project marks a new height in the application of UHV technology in China, strengthens China ’s international influence and competitiveness in the field of power grid technology and electrical equipment manufacturing, and promotes the orderly promotion of power interconnection in the future, driving Chinese technology and services. ” "Going out" laid the foundation.

How far is UHV fully “going to sea”

Western China is rich in energy resources, but it is thousands of miles away from the energy consumption center in the east and central regions, and the power supply and demand regions are uneven. Taking Xinjiang as an example, the local coal reserves are estimated to exceed 2 trillion tons, accounting for more than 40% of the nation ’s coal reserves. Wind and solar reserves are considerable, but underground and air resources require more than 3,000 kilometers of transportation to reach the east. It is a feasible way to transform energy intensive development into electrical energy, and UHV can greatly reduce long-distance transmission losses.

According to State Grid estimates, the Zhundong-Southern Anhui UHV project can deliver 66 billion kilowatt-hours of electricity from Xinjiang to the central and eastern regions each year, reducing 30.24 million tons of coal-fired transportation, and the transmission loss per kilometer is only 1.5%. The transmission capacity is equivalent under full load. With 6 750 kV lines, land and corridor resources are saved.

The construction of UHV power transmission projects and large-scale transmission of clean energy in the western region can alleviate the pressure of air pollution prevention and control in densely populated areas in the eastern and central regions. After the UHV project from Zhundong to southern Anhui is put into operation, it can reduce 24,000 tons of smoke and dust, 149,000 tons of sulfur dioxide, and 157,000 tons of nitrogen oxides.

At present, China has built the "eight-direction-ten-direction" UHV project, and other countries have also seen the advantages of UHV. The first phase of Brazil's beautiful mountain ± 800 kV UHV DC transmission project, jointly invested by China State Grid Corporation and Brazil's State Power Corporation, was laid the groundwork in 2015 and was completed and put into operation in December last year. This first UHV “going out” project in China delivered more than 1/3 of the power of the Meishan Hydropower Station to the load center in southeastern Brazil, meeting the annual electricity demand of 22 million people and realizing the first UHV technology landing overseas .

Right now, the second phase of the project is under construction. The industry expects that the second phase of the project will drive the export of more than 2.5 billion yuan of domestically produced power equipment, and further promote the global application of UHV transmission technology, specifications and standards.

The UHV, which frequently runs two to three thousand kilometers, may have limited appeal to some countries, but it is different for multinational power grids and intercontinental interconnections. Sun Zhengyi, CEO of Japan's Softbank Group, announced that it will build a Northeast Asian energy "super-grid" including China, Russia, Japan, South Korea, and Mongolia. Softbank's 50-megawatt wind farm built in Gobi Beach, Mongolia, was put into use last October. Zhao Huanyi, president of the Korea Electric Power Corporation, also said in a forum that “the“ super power grid ”covering Korea, China, Japan and even Russia is feasible at the economic and technical levels.”

In the fall of four years ago, the United Nations Economic and Social Commission for Asia and the Pacific had invited multinational power experts, representatives of enterprises and investment institutions to discuss the pan-Asian "super power grid" in Xinjiang. Participants analyzed that South Korea and Japan in East Asia are large consumer countries, but supply capacity is weak, Mongolia is rich in coal, wind energy and solar energy, but the consumer market is limited; Tajikistan and Kyrgyzstan in Central Asia have oversupplied hydropower supply, and There are 40 million people lacking electricity in Afghanistan and Pakistan-the conclusion is that the interconnected "Asian Super Grid" can complete cross-border power transactions and interconnections, promote regional energy supply and demand balance, and improve the economics of energy use. "This is the collective energy strategy of Asia in the future," said Derek Akinson, an energy expert at ESCAP.

Promoting the use of renewable energy is considered another driving force for the "Asian Super Grid." Climate change requires countries to study and design a transmission mode based on renewable energy. If you want to give power generation space to wind and photovoltaics that change at any time, the grid must be strong and smart to deal with these "unreliable" energy sources, which requires extra high voltage. The large transmission capacity and sufficient margin of the power grid.

This has been proved by practice. At present, Xinjiang has put into operation the first and second channels of 750 kV "Xinjiang Power Delivery" and ± 800 kV Hami South-Zhengzhou UHV DC transmission channels. Relying on these "electric power highways", Xinjiang's renewable electricity delivery last year accounted for more than 1/3 of the "Xinjiang electricity delivery" total electricity.

Wu Gang, chairman of Goldwind Technology Co., Ltd., said that Xinjiang is bordered by eight neighboring countries and is the core area of ​​the “Belt and Road”. In the future, it can promote the interconnection of electricity between Xinjiang and neighboring countries, deepen international energy cooperation, and serve as a country along the “Belt and Road”. Provide the best solution for energy use.

Controversy about UHV

UHV has been controversial since its birth, especially for UHV AC transmission technology.

There are three main points of view: one is unsafe and there is a danger of a major power outage. The major power outage in the United States and India is a lesson; the second is that the cost is too high, which is equivalent to "burning money". Who will invest; Third, the growth of electricity demand will slow down, and the abandonment of water, wind, and light in the west will intensify, making it difficult to digest the electricity sent by UHV across regions. Policy trends show that the price difference between the electricity transmission area and the electricity receiving area may be further narrowed. Thereby reducing the power of long-distance transmission.

However, there are also opposing views that UHV and the blackout have no direct causal relationship. In addition, the analysis of UHV project cost and economic benefits is not equivalent to the analysis of the overall benefits of UHV power grids.

Interviewed industry insiders told reporters that the advancement of UHV technology should be accompanied by a rigorous demonstration of the entire project, and continuous testing and summary through practice.

Improve the UHV technology level, continuously improve the grid structure, channel design and accident prevention, and improve the safety of UHV. At present, the State Grid has established a simulation center to avoid the failure of safety and stability control measures and prevent large-scale power outages by mastering the simulation analysis technology of power grid characteristics.

Introduce a market-based mechanism and increase the space for renewable energy consumption through cross-provincial spot transactions, which reduced the amount of wind and abandonment of photovoltaics in Gansu Province last year by 19% year-on-year, and new energy consumed through cross-provincial spot transactions accounted for new energy Increase the power generation by half. In the Northeast, thermal power plants that cannot provide in-depth peak shaving pay compensation to thermal power plants that provide in-depth peak shaving services. This market-based pricing of economic compensation encourages power generation companies to actively reduce their emissions when peak shaving is difficult, and also frees up renewable energy. Conserve space.

According to the National "Implementation Plan for Solving the Problems of Abandoned Water, Abandoned Wind, and Abandoned Light", priority will be given to the construction of transmission channels in the next few years that focus on the transmission of renewable energy and have market space in the receiving area; optimize the dispatching operation of the power grid and improve the existing transmission Channel operation efficiency, play the role of a key platform for the power grid, and create a "green channel" for hydropower, wind power and photovoltaics; carry out cross-region and cross-basin wind, water and fire joint dispatch operation according to local conditions to achieve a complementary balance of multiple energy power generation, thereby gradually solving the nation Wind abandonment problem.

It is foreseeable that China ’s UHV technology with independent intellectual property rights will not grow overnight, and there will still be controversy on the road of development, and the full “going to sea” will not be a smooth journey. In the future, it needs to improve safety, maintain advanced technology, and expand cost advantages. We also need to consider China's supply chain control capabilities and mass industrial manufacturing capabilities.