The prototype of the "sun"-shaped UHV ring network in central China is gradually emerging

China Energy Storage Network News: During the 14th Five-Year Plan period, electricity demand in the central China region will continue to grow, and the task of power supply security is arduous, requiring continuous optimization and strengthening of the grid structure.

The construction of UHV projects in Central China has entered the "fast lane". The Shaanxi-Hubei ±800 kV UHV DC project (referred to as the "Shaanxi-Hubei project") has officially been put into operation. As of April 16, it has cumulatively transmitted more than 3 billion kWh of electricity to Hubei; the Nanyang-Jingmen-Changsha 1000 kV UHV AC project (referred to as the "Nanyang-Jingmen-Changsha project") is expected to be put into operation and completed by the end of the year; the Zhumadian-Wuhan 1000 kV UHV AC project is under construction in full swing; the environmental impact assessment of the Wuhan-Nanchang 1000 kV UHV AC project (referred to as the "Wuhan-Nanchang project") was recently submitted for review.

In the eyes of the industry, the Central China Power Grid is under great pressure to ensure supply. In order to significantly improve the cross-regional resource allocation capabilities, it is necessary to build the Wuhan-Nanchang 1,000 kV UHV AC transmission and transformation project. With the environmental impact assessment submitted for review, the last "vertical" of the Central China "sun"-shaped ring network has finally been put into practice.

Power demand in Central China is strong

The Central China region is characterized by large electricity consumption, rapid growth, high costs and large gaps. In 2021, the total electricity consumption of the seven provinces (regions and cities) was close to 1.5 trillion kWh, an increase of 12.3% year-on-year, 2 percentage points higher than the national average. Four of the top five provinces (regions and cities) in the country with the fastest electricity growth are in the Central China region.

Due to the strong demand for electricity in Central China, all provinces in the region currently have electricity gaps to varying degrees. According to data, during the 14th Five-Year Plan period, the electricity gap in Central China will be about 42 million kilowatts. With the continued growth in electricity demand, the task of ensuring electricity supply has become more arduous. In particular, the four provinces of Hubei, Hunan, Henan, and Jiangxi are short of primary energy and need to receive large amounts of external electricity. Taking Henan as an example, the scale of external electricity entering Henan last year hit a record high, with electricity reaching 71.5 billion kilowatt-hours.

It is particularly noteworthy that the Central China Power Grid is located at the hub center of the national power grid, bringing together clean energy such as Northwest new energy, Southwest hydropower and Three Gorges hydropower. It is an important energy strategic channel. Optimizing and strengthening the grid structure of the Central China regional power grid through UHV projects will not only enhance the guarantee of resource mutual assistance between provinces, but also ensure the safe and stable operation of the Central China power grid.

Many industry insiders believe that as clean energy gradually becomes the main power source, it will have a fundamental impact on the safe and stable operation of large power grids. It is necessary to strengthen the safety risk management of UHV transmission channels and respond to risk challenges such as UHV AC/DC hybrid and dense transmission channels.

Improving inter-provincial power exchange capabilities

The Central China Power Grid consists of the power grids of Hubei, Hunan, Henan and Jiangxi provinces. As of the end of 2020, the total installed power capacity was 275,390 MW (including 22,400 MW of the Three Gorges Power Station). The region has achieved inter-provincial interconnection through the Hubei-Henan 1,000 kV and 500 kV lines, the Hubei-Hunan 500 kV lines, and the Hubei-Jiangxi 500 kV lines. It is connected with Sichuan and Chongqing through back-to-back asynchronous interconnection between Chongqing and Hubei, with North China through 1,000 kV lines and 500 kV lines, with the Northwest through Lingbao back-to-back and ±800 kV DC lines, with East China through ±500 kV DC lines, and with the Southern Power Grid through ±500 kV DC lines.

At present, the UHV AC transmission and transformation projects such as Nanyang-Zhumadian, Jingmen-Wuhan, Nanchang-Changsha, Nanyang-Jingmen-Changsha, and Zhumadian-Wuhan in the Central China Ring Network have been approved for construction, and only the Wuhan-Nanchang project remains to be approved.

Some people believe that in order to ensure the safe and stable operation of UHV DC projects such as Hami-Zhengzhou, Jiuquan-Hunan, Qinghai-Henan, Northern Shaanxi-Hubei, Ya'an-Jiangxi, and Jinshang-Hubei that transmit electricity to the Central China region, it is necessary to build a Central China UHV AC ring network project. The Wuhan-Nanchang project is an important part of the Central China "sun"-shaped UHV AC ring network.

It is understood that the planned Wuhan-Nanchang project can not only realize the ultra-high voltage AC interconnection between Hubei and Jiangxi, but also provide voltage support and flow transfer channels for the load center in the south of the Yangtze River in eastern Hubei, enhance the power transmission capacity outside the Central China power grid such as the Jinshang-Hubei DC project and the inter-provincial power exchange capacity between Hubei and Jiangxi, but also create favorable conditions for disconnecting the 500 kV connection between Hubei and Jiangxi provinces and sorting out the 500 kV grid in the eastern Hubei region.

Song Hongkun, Secretary of the Party Leadership Group of the Central China Regulatory Bureau of the National Energy Administration, once proposed that we should give full play to the complementary advantages of energy resources among the provinces in the central China region, especially as the regional ultra-high voltage main grid becomes increasingly perfect, the cross-provincial resource allocation capacity will be significantly enhanced, and the regional energy coordinated development capacity will be further improved. Efforts should be made to optimize the allocation of cross-provincial clean energy, promote the construction of clean energy bases in the region such as the upper reaches of the Jinsha River hydropower, and rely on the central China regional ultra-high voltage AC ring network to coordinate and optimize the consumption and utilization of clean energy in the region.

New technologies and new methods are constantly applied

The reporter learned from the interview that the Nanyang-Jingmen-Changsha project is a key construction project of the country's "14th Five-Year Plan" power planning, and it is also an important measure for State Grid to strengthen the construction of the main grid in the sending and receiving areas and cross-regional transmission channels.

In the construction of UHV in the past two years, power grid companies have continuously innovated and applied new technologies and methods. For example, in promoting the high-quality construction of the Nanyang-Jingmen-Changsha project, State Grid Henan Electric Power Co., Ltd. (hereinafter referred to as "Henan Electric Power") took the lead in carrying out mechanized construction throughout the entire process, with a mechanization rate of 100%, achieving the concept and goal of "reducing labor, reducing risks, and ensuring safety with machinery".

It is understood that the Nanyang-Jingmen-Changsha project is the first time in China that intelligent tensioning equipment has been used to carry out UHV AC engineering cross-construction. Most of the traditional transmission line tensioning and laying out are done by setting up special personnel along the line to monitor and report the laying out situation. There are problems such as too much manpower and untimely information acquisition, and safety hazards often occur. The project has realized the digitization and intelligent control of the tensioning machine and the intercommunication of tensioning field data by adding centralized control, visual monitoring, and intelligent control functions of tensioning equipment. "This is like installing a 'clairvoyance' on the equipment, and the operator can clearly see the picture of the entire laying out process in the centralized control room. Real-time control of the construction is carried out to achieve 'human-machine separation' and 'single person controlling multiple devices'." A relevant person in charge of Henan Electric Power said.

For example, the Shaanxi-Hubei project was the first large-scale application of my country's independently developed "large effective area optical cable" in the country, solving the "bottleneck" problem that has long restricted the development of my country's power transmission and transformation industry.