Three Gorges (Power Station)

The idea of ​​building a large dam on the Yangtze River was originally expressed by the Kuomintang Prime Minister Sun Yat-sen in his work “China's International Development” in 1919. He said that in the area of ​​the Three Gorges, the dam is capable of generating capacity of 30 million horsepower (22 GW ) ^{[8] [1]} . In 1932, the government of the Republic of China , headed by Chiang Kai-shek , began preliminary work on plans for the construction of the dam. In 1939, during the Sino- Japanese War, Japanese forces occupied Yichang County and explored the area. The Japanese dam project was completed and only victory over united China was expected to begin its implementation .

In 1944, John Savage , chief design engineer for the American Land Reclamation Committee, surveyed the Three Gorges area and developed a proposal for a dam. About 54 Chinese engineers went to the USA for training. Surveys of the area, some economic and other studies were carried out, design work was carried out. But the government at the height of the civil war curtailed work in 1947 ^[9] .

After the victory of the Communists in 1949, Mao Zedong supported the idea of ​​building a dam in the Three Gorges. But, given the consequences of the civil war and the state of industry at that time, the country could not yet afford a project of this magnitude. In 1970, the construction of the smaller Gezhzhouba hydroelectric station began a little lower downstream. After the death of Mao Zedong with the rapid growth of the PRC economy since the late 70s, ideas about a giant dam began to gain ground. In 1988, the Hejzhouba Hydroelectric Power Station was completed, becoming the first major hydraulic engineering project of the PRC on the Yangtze River. Subsequently, in the 1990s and 2000s, all revenues from the electricity generation of the Gejobua HPP went to finance the construction of her older brother ^[1] . In 1992, the National People's Parliament of China approved the construction of the dam: out of 2,633 delegates, 1,776 voted in favor, 177 voted against, 664 abstained, and 25 members did not vote ^[10] . Construction began on December 14, 1994. It was expected that the hydropower plant would be fully operational by 2009, but additional projects, such as an underground unit of hydraulic units, delayed the date for official completion of construction until May 2012. By October 2010, the water level in the reservoir rose to a design level of 175 m above sea level ^[11] . In January 2016, the last element of the hydraulic system was opened - a ship elevator for passenger ships weighing up to 3000 tons ^[12] .

The composition of hydroelectric power plants:

• gravity concrete dam 2309 m long and 181 m high;
• the left-bank dam building of the hydroelectric power station with 14 hydraulic units ;
• the right-bank dam building of the hydroelectric power station with 12 hydraulic units;
• right-bank underground building of hydroelectric power station with 6 hydraulic units;
• two-strand five-stage navigable lock (mainly intended for cargo ships, passage time of locks about 4 hours, chamber dimensions 280 × 35 × 5 m);
• ship elevator (mainly designed for passenger ships, cargo capacity 3,000 tons, rise / lower time 10 min, passage - 30 min)

The dam is 2309 m long and 181 m high from the rocky base, made of concrete and steel . The project used 27.2 million m³ of concrete (a record amount for one project), 463 thousand tons of steel ^[13] and relocated about 102.6 million m³ of land ^{[14] [1]} .

In three buildings of the hydroelectric station, 32 radial-axial hydraulic units with a capacity of 700 MW each with a design head of 80.6 m are located. Two generators for the station’s own needs, with a capacity of 50 MW each, were also put into operation. After the addition of the underground turbine hall in 2012, the amount of electricity generated per year largely depends on the size of the Yangtze flood , the operation of which is possible by additional electric generators.

Pressure structures of hydroelectric power plants form a large reservoir with an area of ​​1045 km², a useful capacity of 22 km³. When it was created, 27,820 hectares of cultivated land were flooded, the cities of Wanxian and Wushan went under water ^[15] . The maximum permissible elevation of the upstream above sea ​​level (NPU), equal to 175 m, was first achieved in 2010 ^[11] . The reservoir can be operated up to 145 m. The height of the lower pool above sea level is 66 m. Thus, the pressure level during the year varies from 79 m to 109 m, the maximum is reached in the summer monsoon season . The hydraulic unit is equipped with a spillway with a throughput of 116,000 m³ / s.

Initially, the government estimated the cost of the Three Gorges project at 180 billion ¥ ($ 26.9 billion) ^[16] . By the end of 2008, expenditures reached 148.365 billion ¥, of which 64.613 billion ¥ was spent on construction, 68.557 billion ¥ on allowances for the affected residents and their relocation, and 15.195 billion ¥ on loan payments ^[17] . In 2009, it was determined that the cost of the dam will pay off when it produces 1000 TW · hr of electricity, which is ¥ 250 billion at electricity prices in China. According to calculations, the payback period was ten years after the dam started operation ^[16] , however, the Three Gorges hydroelectric station fully paid for itself by December 20, 2013 - 4 years after the commissioning of the first turbines and a year after the official commissioning ^[18] .

Sources of financing for the dam were: The Three Gorges Construction Fund, income from the Gezhzhuba HPP, loans from the China Development Bank , loans from Chinese and foreign commercial banks, corporate bonds , income received from the dam itself before and after its full commissioning . Additional charges were also established: in each province receiving electricity from the Three Gorges hydroelectric power station, a surcharge of 7 ¥ per MWh was established, in all other provinces, with the exception of the Tibet Autonomous Region , the surcharge was 4 ¥ per MWh ^{[ 19]} .

Three Gorges HPP is of great importance for the Chinese economy, providing coverage for annual growth in electricity consumption. The power plant, together with the Gezhoub hydroelectric station in the downstream, has become the center of China's integrated energy system. Initially, it was expected that the hydropower plant would cover 10% of China's electricity needs. However, over 20 years of construction, electricity consumption grew at a faster pace, and in 2012, hydropower plants generated only 1.7% of all Chinese electricity (98.1 out of 4692.8 TW · h) ^{[20] [21]} .

The dam regulates the water regime of the Yangtze, the devastating floods of which over the past 2000 years have occurred more than 200 times. In the 20th century, catastrophic river spills caused the death of about half a million people. In 1991, the damage from the violence of the water element amounted to 250 billion ¥ (which is equivalent to the cost of building a hydroelectric power station). However, the 2010 flood did not result in casualties or significant damage. Thus, the spillway and the dam itself successfully cope with the functions assigned to them ^{[15] [1]} .

Equipping the waterworks with locks and the formation of a reservoir improved shipping conditions in this part of the Yangtze. Cargo turnover in this section increased from 10-18 million tons per year to 100 million tons per year, while transportation prices decreased by more than a third. These facts to a large extent contributed to the rapid economic development of the western (relative to the dam) areas of China, primarily the city of Chongqing ^[1] .

Generators

The main generators of the power plant weigh 6,000 tons each with an estimated capacity of 700 MW each. The design head for the main generators is 80.6 m. The water flow rate varies from 600 to 950 m³ / s, depending on the current head (from 79 to 109 m). The greater the current head, the less water flow is required to achieve rated power. The Three Gorges Generators use radial-axis turbines (Francis turbines) . The diameter of the turbines is from 9.7 to 10.4 m (depending on one of the two design options), and the estimated rotation speed is 75 rpm. In accordance with this, to produce current at a frequency of 50 Hz, the rotors of the generator have 80 poles . The rated power of the generators is 778 MW, the maximum is 840 MW, and the power factor is 0.9. Generators produce electricity at a voltage of 20 kV. Then the generated voltage is increased by transformers to 500 kV and then transmitted to the network at a frequency of 50 Hz. The outer diameter of the stator is from 21.4 to 20.9 m, the inner is from 18.5 to 18.8 m, and the height is 3–3.1 m. These sizes make these generators the largest of their kind. The supporting load of the generators is 5050–5500 tons, the average efficiency is 94% with the maximum reached 96.5% ^[22] .

The generators were manufactured according to two design options by two joint groups of enterprises: one of them - Alstom , ABB Group , Kvaerner and the Chinese company Haerbin Motor; the other is Voith , General Electric , Siemens and the Chinese company Oriental Motor. An agreement on technological cooperation between the groups was signed along with the contract. Most generators are water cooled . Some newer models have an air one , which has an advantage in the simplicity of design, manufacture, and maintenance ^[23] .

Power Generation

In July 2008, for the first time, the monthly power generation of hydropower plants exceeded the bar of 10 TWh (10.3 TWh) ^[24] . On June 30, 2009, after the Yangtze flow exceeded 24,000 m³ / s, all 28 generators were turned on, producing only 16,100 MW, because the installed capacity of the generators was still not enough to handle the increased flow during the flood period ^[25] . During a flood in August 2009, a hydropower plant for the first time reached its maximum output of 18,200 MW for a short period ^[26] .

During the dry season from November to May, the hydroelectric power generation capacity is limited by the volume of the river flow, as can be seen in the diagrams on the right. If there is sufficient flow, the output power is limited by the capabilities of the generators. The maximum power curves were calculated on the basis of the average flow rate, provided that the water level is 175 m and the gross efficiency of the energy center is 90.15%. Actual capacity in 2008 was obtained on the basis of monthly electricity sent to the grid. ^{[27] [28]}

The estimated maximum water level of 175 m was first reached on October 26, 2010, and the estimated annual production of 84.7 TWh was realized for the same year ^[11] . In 2012, 32 power units of HPPs produced a record world power of 98.1 TWh of electricity, which amounted to 14% of the generation of all HPPs in China ^[4] . By August 2011, the hydroelectric power station produced 500 TWh of electricity ^[29] .

Power Distribution

Until July 2008, state-owned companies State Grid Corporation of China and China Southern Power Grid Paid hydroelectric power plants a flat rate of 250 ¥ per MWh (2.5 rubles per kWh). Now the rate for the provinces varies from 228.7 to 401.8 ¥ per MWh. Many paying consumers, such as Shanghai , receive priority in the distribution of electricity ^[41] .

For the transmission of electricity from hydroelectric power stations to consumers, 9484 km of high-voltage networks of power transmission lines were erected, including 6519 km of alternating current with a voltage of 500 kV and 2965 km of direct current lines with a voltage of ± 500 kV and higher. The total installed capacity of transformers at AC voltage is 22.75 GV · A , and for a DC system - 18 GW . A total of 15 high-voltage lines diverge from the hydroelectric station in 10 different provinces of China. The construction of the entire transformer and transport power network from the hydroelectric station cost 34.387 billion ¥. Its construction was completed in December 2007 - a year ahead of schedule ^[1] .

Gateways

Near the dam, two sluice lines are arranged ( ). Each of them consists of five steps and has a travel time of approximately 4 hours. Sluices pass ships with a displacement of not more than ten thousand tons ^[42] . The length of the lock chambers is 280 m, the width is 35 m, the depth is 5 m ^{[43] [44]} This is 30 m longer than the locks on the St. Lawrence Sea Route , but it is twice as inferior in depth. Before the dam was built, the maximum cargo turnover at the Three Gorges section was 18.0 million tons per year. From 2004 to 2007, the turnover through locks totaled 198 million tons. The river’s capacity increased six-fold, while the cost of transportation decreased by 25%. It is assumed that the throughput of the gateways will reach 100 million tons per year ^[45] .

Gateways are a type of tubeless gateway. The gates are a very vulnerable hinge structure, their breakage will lead to disruption of the functioning of the entire gateway thread. The presence of two threads, separately for raising and lowering, provides more efficient work compared to the option when one thread serves alternately for raising and lowering ships.

Lifts

In addition to the locks, the hydraulic unit is equipped with a ship elevator for ships with a displacement of up to 3000 tons ^[46] (the original design provided for a lift with a lifting capacity of 11 500 tons). The height of the lift varies depending on the levels of the upper and lower pools, the maximum height is 113 m ^[47] , and the size of the lifting chamber is 120 × 18 × 3.5 m. After commissioning, the ship elevator will move the ships in 30–40 minutes, compared with 3-4 hours, if they moved through the gateways ^[48] . During its design and construction, the main difficulty was the need to ensure operation in conditions of significant changes in water levels. It is required to ensure the operation of the ship elevator in conditions where the water level can go within 12 m from the lower side and 30 m from the top.

The first tests of the ship elevator took place on July 15, 2016, during which the cargo ship was raised to the upper reach, the lifting time was 8 minutes. ^[49] . In October, the world's largest ship elevator at the world's largest power plant was launched ^[50] .

Rail Lift

There are plans to build rail tracks for transporting ships through the dam. To do this, they are going to lay short rail tracks on both sides of the river. The 88-kilometer northern rail section will run from the Taipingxi port area on the north side of the Yangtze River, up from the dam through the Yichang East Railway Station to the Baiyang Tianqihe Port Port Area in Baiyang City ^[51] . The 95-kilometer southern section will pass from Maopin (on the upper side of the dam) through the Ichan South railway station to Zhizeng ^[51] .

At the end of 2012, preparatory work began on laying these railways ^[52] .

Considering the fact that in China 366 g of coal is burned to generate 1 kWh of electricity ^[53] , it is expected that the commissioning of the power plant will lead to a reduction in coal consumption by 31 million tons per year, which will not be released into the atmosphere 100 million tons of greenhouse gases , millions tons of dust, 1 million tons of sulfur dioxide, 370 thousand tons of nitric oxide, etc. It is also announced that increasing the Yangtze level due to the creation of a reservoir will allow much more capacious vessels to pass along the river, which will also reduce organic emissions of combustion products The fuel ^{[54] [55] [45]} .

At the same time, many scientists point out the possible negative consequences of the construction of a hydroelectric power station. Before the construction of the Yangtze dam and its tributaries, eroding the banks, carried out millions of tons of sediment annually. Due to the overlap of the channel, this number will be significantly reduced, which is believed to lead to greater vulnerability of the underlying areas to floods, as well as to changes in species diversity ^{[56] [57]} . It is also noted that the construction of the dam cannot fail to damage a number of species that inhabit the river and surrounding areas. In particular, flooding of marshes where this rare bird overwinters can cause significant damage to the population of virtually extinct Siberian Crane ^[58] . It is expected that a change in temperature and water regime due to the construction of the "Three Gorges" will inevitably affect a number of fish species living in the Yangtze, in particular, the sturgeon family. As for the Chinese river dolphin , which was most likely extinct by the beginning of the construction of the hydroelectric station, it is believed that the construction of the dam will finally put an end to the survival of this species ^{[59] [60]} .

In the event of a breakthrough of the dam, about 360 million people may be at risk of entering the flood zone.

• 1992 - the beginning of the construction of a hydroelectric station;
• December 14, 1994 - the beginning of the construction of the dam;
• 1997 - laying of the first concrete layers;
• November 8, 1997 - the overlapping of the Yangtze;
• 2003 - launch of the first hydraulic units (June 10 - the first hydrogenerator ^[15] );
• September 2005 - commissioning of the left building of the hydroelectric power station; the station reached a capacity of 9.8 GW;
• May 20, 2006 - the construction of the dam is completed;
• December 7, 2007 - commissioning of the 20th hydroelectric unit, the station's capacity reached 14.1 GW ^{[61] [62]} ;
• August 2008 - the completion of the dam building near the hydroelectric station, with the introduction of the 26th unit, the station reached a capacity of 18.2 GW ^[25] ;
• October 29, 2008 - all 26 hydrogenerators of the main buildings were launched ^[15] ;
• in 2011 - the commissioning of the underground building of the hydroelectric station and the completion of the construction of ship elevators;
• July 4, 2012 - the completion of the construction and commissioning of the last 32nd power unit was officially announced.
• October 2016 - the launch of the ship elevator.

According to NASA , when a reservoir was formed, raising 39 billion tons of water to a height of 175 m above sea ​​level increased the moment of inertia of the Earth and reduced its rotation speed , thereby increasing the day length by 0.06 microseconds ^{[63] [64]} .

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  "Sansya"

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  Reservoir

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  Layout of a part of the Sansya structures

• Photo tour of the hydroelectric station: view of the dam, locks, a complex of hydraulic structures. Lock