The myth of “UHV”: “Only the right one is the best”

China Energy Storage Network: UHV transmission is known as the "power highway". Since the first UHV transmission line was built in China in 2009, UHV has been in operation in China for more than ten years.

On March 4, the central government proposed to accelerate the construction of new infrastructure. Later, in the interpretation of CCTV news, UHV was included in the "new infrastructure" along with 5G network, artificial intelligence, industrial Internet of Things, etc. This news caused heated discussions in the energy circle.

Recently, a series of actions and statements by State Grid Corporation of China (hereinafter referred to as State Grid) regarding ultra-high voltage have once again attracted great attention from the industry.

However, to this day, there has been constant controversy about UHV power transmission, especially AC UHV.

The hasty launch is controversial

By the end of 2019, the State Grid had completed 22 UHV projects with a cumulative investment of more than 430 billion yuan, and 6 UHV projects were under construction. The State Grid said that UHV has played an important role in ensuring power supply, promoting the development of clean energy, improving the environment, and enhancing the safety level of the power grid.

Since UHV was included in the "new infrastructure", the State Grid has set up a special "new infrastructure" leading group and held its first meeting on April 2, proposing to ensure the completion of four projects within this year and promote the approval of UHV projects that have been included in the national plan as soon as possible. On April 11, the State Grid also signed a strategic cooperation agreement with Tianjin, and promoted the accelerated construction of UHV supporting power sources as one of its important contents.

Despite this, there are still different opinions in the academic community as to whether UHV can be included in the "new infrastructure."

Wang Zhonghong, who has been retired for many years, was a researcher at the Department of Electrical Engineering and Applied Electronics Technology of Tsinghua University and has been engaged in power work for more than 30 years. In his view, the purpose of "new infrastructure" is to achieve industrial upgrading with new technologies, and the UHV transmission project is a shelved project for some reason, not a high-tech project.

"It may be due to the consideration that ultra-high voltage will drive the development of industries such as wind power and photovoltaics in the future," speculated Lin Boqiang, director of the China Energy Policy Research Institute of Xiamen University.

Yu Miaojie, Party Secretary of the National School of Development at Peking University, said in an interview with China Science Daily that it is reasonable for UHV to be included in the "new infrastructure". He said that as an infrastructure field that has not been fully explored, UHV still has room for development. "It can not only meet the society's growing demand for electricity, but also serve as a production factor to promote the better integration of other resources, thus playing the role of 'small wheels driving big wheels'."

Chen Haoyong, a professor at the School of Electric Power of South China University of Technology, disagrees with the inclusion of UHV in the "new infrastructure". "Although UHV technology has promoted the development of the electrical equipment industry, the utilization rate of the UHV transmission lines that have been built is not high."

According to data from 2018, the annual transmission energy utilization rate of 20 UHV transmission lines was only half of the design value, "reflecting the overcapacity of UHV transmission." Wang Zhonghong told China Science Daily that China's power production capacity is already in excess, and the impact of the epidemic has become even worse. UHV transmission involves an investment of several hundred billion yuan, which will inevitably increase the cost of electricity and inhibit economic recovery in both production and consumption.

In Yu Miaojie's view, although the investment cost of ultra-high voltage is relatively high, its main investment and financing channels come from the national treasury, which will eventually significantly reduce electricity prices, thereby indirectly reducing taxes and fees for small and medium-sized enterprises and increasing corporate profit margins.

"The top priority should be to conduct a post-evaluation of the utilization efficiency of these already built UHV transmission lines, rather than hastily launching new transmission lines. Otherwise, it would be equivalent to building a few roads with no traffic, which would not only fail to drive economic growth, but would instead cause a waste of resources," said Chen Haoyong.

A forgotten document

UHV includes ±800 kV direct current and 1000 kV and above alternating current. Among the many controversies about UHV, the most controversial is AC UHV.

In 2018, the Chinese Academy of Engineering, commissioned by the National Energy Administration, summarized the research and discussion results of seven units across the country and finally formed the "Advisory Opinions on the Research on my country's Future Power Grid Structure (2020)" (hereinafter referred to as the "Opinions").

Chen Haoyong is a member of the advisory expert group and participated in the drafting of the Opinion. In his opinion, the Opinion is relatively objective and pertinent.

The "Opinion" denies the technical direction of ultra-high voltage AC transmission projects because ultra-high voltage AC projects have drawbacks such as huge investment and very low utilization rate. They have limited effects on power grid security and will also bring new safety risks.

In September 2018, the National Energy Administration issued a related notice, planning to approve nine key transmission and transformation lines in 2018 and 2019, involving 12 UHV lines of "7 AC and 5 DC". State Grid recently announced that it will speed up the approval of 10 UHV lines of "5 AC and 5 DC" within the year and the preliminary scientific research work in 2020.

However, as of now, the "Opinion" has not received any public response from relevant departments.

"AC ultra-high voltage power transmission technology is not the preferred choice, and the dispute has been unresolved for many years. This has no precedent in the history of world power transmission technology," said Wang Zhonghong.

Wang Zhonghong has participated in the demonstration and consulting work of all AC UHV transmission projects since 2005. He said that except for the first test demonstration line, all other AC UHV transmission lines, although given various reasons for development by the State Grid, have not passed the expert demonstration.

In Chen Haoyong's opinion, although UHV DC technology has played a certain role in the "West-to-East Power Transmission" strategy and is necessary in specific situations, the high cost of UHV AC and its utilization rate has always been low, which should be reflected upon.

"Providing power supply for UHV transmission channels is putting the cart before the horse," added Chen Haoyong.

In recent years, as the development of AC UHV has slowed down, the voices of opposition seem to have decreased. But in fact, experts such as Chen Haoyong said helplessly: "It's useless to oppose." Even retired experts such as Wang Zhonghong have been raising objections through various channels, saying that "right and wrong are more important than whether they are adopted or not."

An expert told China Science Daily that if it were a normal enterprise in the market, the high transmission costs brought by the AC UHV project would not be sustainable for a long time. However, China's electricity industry is a monopoly industry, and the electricity price is calculated by cost plus, so the situation is relatively "special".

Urgent need for truly independent and scientific evidence

Whether it is UHV or other transmission methods, the goal should be to transmit electricity in the simplest, most economical and safest way to meet the needs of the load center.

In my country, voltage is divided into five levels: safe voltage, low voltage, high voltage, ultra-high voltage and extra-high voltage. "It is not the case that the higher the voltage level, the better." Chen Haoyong said.

"Only the most suitable one is the best." Wang Zhonghong explained to China Science Daily that the voltage of the power grid is positively correlated with its capacity. At present, the capacity of a single power grid in the world has reached 800 million kilowatts, using ultra-high voltage power grids. The largest power grid capacity in my country is about 200 million kilowatts, and there is still a lot of room for development.

The "Opinion" also mentioned that the maximum load of the Central China Power Grid reached 149 million kilowatts in 2017, and the total installed capacity reached 226 million kilowatts. The scale of the power grid is large, but the 500 kV ultra-high voltage main grid still has great potential. After taking necessary strengthening measures, it can absorb a large amount of external electricity and ensure the safety of the power grid.

my country's development of UHV can be traced back to the 1990s. Zhou Heliang, former director of the Electrical Engineering Bureau of the Ministry of Machinery Industry, recalled in an article that at that time, from the perspective of the imbalance between my country's energy resources and economic development, relevant units visited Europe, Japan and Russia, and after a series of expert discussions and reports, the development of UHV was approved by the State Council.

Coincidentally, countries such as Italy, the United States, and Japan have not promoted UHV on a large scale. Chen Weijiang, an academician of the Chinese Academy of Sciences and deputy chief engineer of the State Grid Corporation of China, once pointed out that although these countries have researched and developed UHV transmission technology, in the end, due to economic reasons, the projects were stopped, suspended, or the transmission voltage level was reduced.