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Three Gorges Project Hydroelectricity Generation and Distribution
Total Generating Capacity
The Three Gorges Dam is the world's largest hydro-electric power station by total capacity, which will be 22,500 MW.It will have 34 generators in total. Thirty two of them are main generators, each with a capacity of 700 MW, and the other two are plant power generators, each with capacity of 50 MW. Fourteen are installed in the north side of the dam, twelve in the south side and the remaining six in the underground power plant in the mountain south of the dam. After completion, the expected annual electricity generation would be over 100 TWh, 18% more than originally predicted 84.7 TWh, since six more generators were added to the project in 2002.
Generators
Each of the main generators weighs about 6000 tonnes and are designed to produce at least 700 MW of power, which is enough to power a large city. The designed head of the generator is 80.6 m. The flow rate varies between 600 cu m to 950 cu m depending on the head available. The Three Gorges Dam project installs Francis Turbines. The Francis Turbine is the most efficient turbine in the world. The diameter of the turbine is 9.709/10.427m(VGS design/Alstom's design). It rotates at a speed of 75 rpm. The normal rated power of the generator is 778 MVA. The maximum power is 840 MVA. The power factor is 0.9. The generator produces electrical power at 20 kV. The outer diameter of the generator stator is 21.42/20.9m. The inner diameter is 18.5/18.8m. The height of the stator is 3.13/2.95m. It is the biggest stator in the world. The load at the bearing is 5050/5500 tonnes. The average efficiency of the generators is over 94%, and the highest is 96.5%.
The generators are manufactured by two joint ventures. One of them includes Alstom, ABB, Kvaerner and the Chinese company Haerbin Motor. The other includes Voith, General Electric, Siemens (abbreviated as VGS), and the Chinese company Oriental Motor. The technology transfer agreement was signed together with the contract. More than 8 of the 32 generators are made in China. Most of the generators are water-cooled. Some newer ones are air-cooled, which are simpler in design, manufacture and easier to maintain.
Generator Installation Progress
The 14 generators in the north side of the dam have already been installed. The first one (No.2) started to power on July 10, 2003. The last one (No.9) started to power on September 7, 2005. All of the 14 generators first ran to full power (9800 MW) on October 18, 2006 after the water level had been raised to 156 m.
The 12 generators in the south side of the dam have already been installed. The first generator (No. 22) in the south side of the dam started working on June 11, 2007. The last generator (No. 15) on the south side of the dam was completed and brought to the power grid on Oct.30, 2008.The sixth generator in the south side (No. 17) started working on December 18, 2007. It brought the total capacity of the dam to 14.1 GW, surpassing the generating capacity of Itaipu (14.0 GW), to become the largest hydroelectric power plant in the world. The seventh generator in the south side (No. 17) started working on December 27, 2007.The eighth generator in the south side (No. 24) started working on April 25, 2008. The ninth generator in the south side (No. 19) started working on June 18, 2008.The tenth generator in the south side (No. 16) started working on July 2, 2008. The eleventh generator in the south side (No. 23) started working on August 19,2008. The total capacity of the plant is currently at 18.30 GW. Added to the project in 2002, the underground power plant and its six generators are still under construction. The Three Gorges Dam project also sets the record of having most generators being installed in one year (2007),that is 7 units with a capacity of more than 5000 MW.
Total Energy Generated
As of October 30, 2008 the Three Gorges Dam Project had generated over 274.4 TWh of electricity, more than one fourth of the 1000 TWh it needs to generate to cover the cost.With 18,300 MW installed capacity, the generation capacity of the Three Gorges Dam Project is about 4,300 MW more than that of the Itaipu Dam. In July 2008, the Three Gorges Dam generated 10.3 TWh of electricity, which is the first time to generate more than 10 TWh in a month.
Power Distribution
The electricity generated by the Three Gorges Dam project was sold to the State Grid Corporation and China Southern Power Grid at a flat rate of 250 CNY per MWh ($35.7 US) until July 1st, 2008. The price of electricity now is different depending on which province is selling to, ranging from 230.6 CNY per MWh to 311.1 CNY per MWh. Nine provinces and two cities consume the power from it, including Shanghai.
The power distribution and transmission of the Three Gorges Dam project cost about 34.387 billion Yuan. It was completed in December 2007, one year ahead of time.
Power is sent in three directions. The 500 kV DC transmission line to the East China Grid has a capacity of 7,200 MW. There are three 500 kV DC transmission lines: HVDC Three Gorges-Shanghai(3,000 MW), HVDC Three Gorges-Changzhou(3,000 MW) and HVDC Gezhouba - Shanghai(1,200 MW). The 500 kV AC transmission line to Central China Grid has a capacity of 12,000 MW. The other 500 kV DC transmission line HVDC Three Gorges-Guangdong to South China Grid has a capacity of 3,000 MW and supplies Guangdong.
In the original plan, it was expected to provide 10% of electricity consumption in China. However, China's demand for electricity has increased at a higher rate than was planned, and if fully operational now, it would support about 3% of the total electricity consumption in China.
