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China steps up in buliding UHV power line
Updated: 2009-02-07 16:04
Despite the chilly wind, the erection of electricity pylons and the building of converter stations on one of China's most remarkable technological achievements goes ahead full swing across the mountains and plains from southwest China's Sichuan province to east China's coastal Shanghai.

Even the Spring Festival does not hold up work on the electricity power line, the world's only 800 kv direct current UHV line.

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"We cannot suspend our work even in the week-long Spring Festival holidays, which began on January 26. We must complete the project by 2010," said Li Wenyi, general manager of the Direct Current Engineering Construction Co Ltd under the State Grid Corporation of China (SGCC), in Yibin, Sichuan, on Tuesday.

Construction kicked off on Dec 12, the pilot project will wind 2,000 km eastward over eight provinces and municipalities to join up Yibin, in Sichuan with Shanghai. It will transmit hydropower generated at Xiangjiaba Hydropower Station and Xiluodu Hydropower Station on Jinshajiang River, the country's second and third largest hydropower projects, after the Three Gorges project.

UHV, defined as voltage of 1,000 kv or above in alternating current, and 800 kv or above in direct current, is designed to deliver large quantities of power over long distances with power losses less than the most commonly used 500 kv lines.

Similar UHV power lines were previously developed in Russia and Japan, but the technology was not widely used in these countries because of relatively weak demand.

"When the transmission line is completed in 2010 as scheduled, we will deliver cheaper hydropower in an endless stream from the southwest hinterland to the energy-thirsty economic powerhouse in the east and essentially solve electric power shortage that puzzled the region for decades," said Li.

Core technologies

Breakthroughs have been made in core technologies and equipment production to turn into reality the dream of transmitting electric power economically with the world's most complex UHV lines.

"Yes, the Russians and Japanese might have the technology. But the most advanced core technologies cannot be bought," said Wu Yusheng, deputy chief engineer of SGCC. "Besides, we have our own conditions and technological requirements that are different from others. Therefore, we must rely on our own efforts for independent innovation."

At the end of 2004, SGCC raised a strategy to transform its power grid development mode, and accelerate constructing a nationwide power grid with 1000 kv alternating current and 800 kv direct current UHV transmission lines as the backbone.

Bearing this objective, Chinese industrial experts have tackled more than 300 key technological problems over the past four years. The result, China has had independent intellectual property rights over UHV transmission lines and could domestically produces 90 percent equipment.

Breakthroughs were made especially in the fields of voltage standard, electromagnetism environment, over-voltage and insulation co-ordination, reactive voltage control, lightning proof technology, design of transformer substations and lines in high altitude and heavily iced areas, UHV construction techniques and great power grid operation control, said Wu.    

The technologies and equipment have succeeded in transmitting large quantities of electric power over long distances with low losses, with nearly one-month of stable and low-noise operation ofthe Shanxi-Hubei UHV transmission line, the first 1,000 kv AC linein the world, said Wu.

On January 6, SGCC successfully put into commercial operation the world's first 1,000 kv UHV alternating current transmission line, after 28 months' construction and 168 hours of test runs at full-rated voltage.

Through the 654-km transmission line, thermal power generated in North China's coal-rich Shanxi province was transmitted to Central China's Hubei province. The transmission line joined the power grid of North China with that of Central China for the firsttime. The project cost 5.7 billion yuan ($832 million),unadjusted for inflation.

That meant, residents in hydropower-rich Hubei, Hunan, Jiangxi and Sichuan provinces and Chongqing municipality started to use electric power generated with coal in North China over the just-ended Spring Festival holidays.

Badly needed 

China, an economically booming country with uneven distributionof energy resources, has to transmit electric power or power coal over thousands of miles. This is different from many western countries where power is often generated more locally.

In China, 76 percent of coal reserves are found in northern and western regions and 80 percent of hydropower in western regions, while more than 75 percent of energy demand is concentrated in the central and eastern regions. China relies on coal to generate nearly 80 percent of electric power.

China's great growth is expected to see it consume 7.4 trillion kWh electric power in 2020, more than doubling the 3.4268 trillion kwh consumed in 2008, said Lu Yanchang, director-general of Chinese Society for Electrical Engineering (CSEE) on Jan 17.

"Under these circumstances, UHV transmission lines become helpful," said Lu.

Lu said when conveying same quantity of electric power, 1,000 kv UHV transmission lines can send the electric power three times in distance than traditional 500 kv lines, while their electric losses account for only 25 percent to 40 percent of the traditional lines. UHV can also save 60 percent of land used to construct the transmission lines.

"Delivering electric power with UHV lines also becomes more economical than transporting power coal to generate electricity atthe destination," Lu said.

China's existing six regional power grids charge local consumers diversified prices for the use of electric power. In North China's Inner Mongolia and Northwest China's Xinjiang, coal-rich areas, electric power is charged at 0.30 yuan per kWh. In contrast, in East China's Zhejiang and Shanghai, electricity ischarged at 0.46 yuan per kWh.

Sending electric power with UHV transmission lines from the north to the east will lower charges by 0.03-0.08 yuan per kWh, compared with transporting power coal to generate power, Lu said.

"It has become a natural choice for the country to distribute energy resources in greater areas to ensure national energy security. Developing UHV transmission lines may effectively solve the problem of sending large quantities of electric power over long distances," said Lu.

Take China's first UHV transmission line. When in full operation, Lu said, it would bring an additional 3 million kW of thermal power to Hubei province and save the central province about 7 million tons of power coal every year, or 90 percent of power coal purchased from other provinces.

The saved amount is equivalent to building another Gezhouba hydro power plant, which is the first hydro station constructed on the Yangtze River in Yichang City, Central China, consisting of 21turbines.

In response to the SGCC blueprint, Shanxi province has mapped out a strategy to give priority to directly transmitting electric power with UHV lines and other voltage lines to end users, while not neglecting coal transportation, over the next two to three years.

"The province will invest 100 billion yuan to construct and run 25 power plants, totaling 20 million kw. installed capacity, and 9,000 km transmission lines of various voltages over the next two years," said Wang Jun, governor of the province, in mid January.

"By 2011, the province will have a total of 70 power plants, with 55 million kW installed capacity. In this way, the province will be able to deliver 120 billion kWh electric power to other provinces from the present 51 billion kWh," said Wang.

More to Come 

In addition to the aforesaid two transmission lines, China approved another pilot 800 kv direct current UHV transmission line linking Jinping, Sichuan with southern Jiangsu Province in the east in November 2008. SGCC Sichuan Branch started to make early preparations and construct converter stations from December 2008 on. The project is to be completed in 2012.

The direct current UHV line, together with the one under construction, has a combined investment of 40 billion yuan.

In addition, on January 18, SGCC announced it would start construction of three more alternating current UHV transmission lines this year. These lines would respectively connect Huainan of Central China's Anhui province and Xilingol of North China's Inner Mongolia with energy-thirsty Shanghai in the east, and the northern part of North China's Shaanxi province with Changsha in Central China's Hunan.

Though it did not give specifics on investment in these three lines, SGCC said it would invest 83 billion yuan in UHV transmission lines in 2009 and 2010 to make long-distance transmission more efficient. They were separated into 57 billion yuan in UHV alternating current transmission lines and 26 billion yuan in UHV direct current transmission lines.

"China needs to develop both alternating current UHV lines and direct current UHV lines," said Zhang Wenliang, president of China Electric Power Research Institute.

"The two have respective advantages. Alternating current UHV isfit for backbone power grid construction and power grid connection. Direct current UHV is ideal to transmit electric power from large-scale hydropower and thermal power stations over long distances," said Zhang.

"Although the current global economic slowdown has led to a smaller demand for electric power in the country, China's electric power sector remains less developed, compared with per capita installed capacity in developed countries. SGCC will double installed capacities in 2020 over the existing volume," said Shu Yinbiao, deputy general manager of SGCC on January 17.

Shu estimates UHV transmission lines will have a transmission capacity of 300 million kW. in 2020, with 78 million kW. Dedicated to hydropower transmission.

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