Decoding the "White Crane Beach" on the Jinsha River
The world's largest under construction, the world's largest single-unit capacity, and the world's second-largest installed capacity... On June 28 this year, amidst a burst of cheers, two million-kilowatt hydroelectric generating units on the left and right sides of the Jinsha River Baihetan Hydropower Station ran at high speeds , The first batch of units was officially put into operation for power generation.
Baihetan Hydropower Station is the backbone power source of the national energy strategic layout "West-to-East Power Transmission", and an important part of the Yangtze River flood control system.
In the construction of the project, the engineers have overcome many world-class problems and created many records.
At the same time, the world's largest single-machine capacity of hydro-turbine generators with a power of one million kilowatts has achieved a major breakthrough in my country's high-end equipment manufacturing.
This marks the completion of a historic leap from "Made in China" to "Created in China" in the construction of large-scale hydropower projects in China.
The world's largest under construction
300-meter-level dams have no one-millimeter temperature cracks
From the preliminary study of Baihetan cascade power station construction in 1991, to the full feasibility study of Baihetan Hydropower Station in 2004, from the formal preparations for construction in 2010, and then to the top of the dam on May 31 this year, it experienced 30 years of hard work. , Baihetan Hydropower Station finally ushered in the first batch of generating units put into operation.
As the largest hydropower project currently under construction in the world, Baihetan Hydropower Station is the second cascade among the four hydroelectric cascades on the lower reaches of the Jinsha River-Wudongde, Baihetan, Xiluodu, and Xiangjiaba. A world record: the total length of underground caverns is 217 kilometers, the scale of underground caverns is the largest in the world; the barrage arch dam is 289 meters high, equivalent to 100 stories high, ranking third in the world; the maximum flood discharge reaches 42348 cubic meters per second. The whole West Lake can be filled in 6 minutes, and the flood discharge power of the hub is the third in the world.
According to Lei Mingshan, Chairman of the Three Gorges Group, the core technology of Baihetan Hydropower Station is independently developed. "After all units are put into operation in July 2022, Baihetan Hydropower Station will become the second largest hydropower station in the world after the Three Gorges Hydropower Station."
To build a hydropower station in the mountains and valleys, where are the power plants built?
How to make each water turbine generator set with a height of 50 meters and a weight of over 8,000 tons lie in it?
In response, Wang Zhilin, director of the Baihetan Project Construction Department of the Three Gorges Group, introduced that the water diversion and power generation system equipment of the hydropower station was placed in underground caverns specially excavated on both sides of the mountain. The excavation volume of the underground cavern reached 25 million cubic meters, which was "enough to fill. Full of 2 West Lakes".
At the same time, the water diversion and power generation system on the left and right banks has arranged more than 160 tunnels, consisting of water inlets, pressure pipes, tailwater tunnels, tailwater outlets and other buildings, plus various corridors and pipelines, thus forming a huge Group of underground caverns.
The underground powerhouses on the left and right sides are 438 meters long and nearly 90 meters high, which is equivalent to a 30-story building with a span of 34 meters, which is also the largest in the world.
Here, it is the "habitat" of 16 million-kilowatt units.
During the construction, the engineers also overcome the world-class problem of temperature control and crack prevention of the 300-meter super high arch dam.
"The maximum height of the Baihetan Hydropower Dam is 289 meters. The overall plan is to pour 8.03 million cubic meters of low-heat concrete. The scale is huge." He Wei, Secretary of the Party Committee of the Baihetan Project Construction Department of the Three Gorges Group, said that the temperature control and crack prevention of mass concrete has always been a project. The problem of the world.
The cement hydration reaction in the concrete generates heat, which causes the temperature of the concrete to rise after pouring, and then slowly cool down to ambient temperature.
If effective temperature control measures are not taken and the concrete is allowed to expand and contract with heat, cracks will inevitably occur.
The Baihetan Hydropower Station dam did not have a millimeter-level temperature crack.
He Wei introduced that this benefitted from the help of the "Beidou" system on the one hand, and on the other hand benefited from the self-developed low-heat cement.
In order to achieve the goal of "seamless", engineers use Beidou navigation system to realize real-time monitoring and comprehensive perception of the pouring stage.
In order to solve the problem of temperature cracks from the source, the Baihetan super high arch dam adopts low-heat cement independently developed by my country to effectively control the maximum temperature of the concrete and prevent the temperature cracks of the concrete.
Intelligent construction system
Solve the world's super-large "flood discharge and energy dissipation" problem
How to realize intelligent construction under the condition of a large amount of concrete pouring has been the focus of Liu Chunfeng, an engineer of the Baihetan Project Construction Department of the Three Gorges Group.
Benefiting from long-term experience in hydropower project construction, during the construction of Baihetan Hydropower Station, the intelligent construction system equips each warehouse with an "identity card" for concrete raw materials to realize intelligent proportioning and traceability.
Nowadays, by staring at the system and clicking the mouse, the modules of the dam construction process data and scientific research results will be successively expanded.
Liu Chunfeng introduced that the system has realized all-weather uninterrupted, and quickly responded to the needs of dynamic supervision, evaluation and early warning, terminal push, etc., to ensure the most objective and direct data to help scientific decision-making on site.
After the excavation of a safe and stable underground cavern is completed, how to ensure the quality of mass concrete pouring is the focus of the engineering staff.
"The maximum lifting capacity of the underground powerhouse bridge crane is 1,300 tons. When the traction rotor runner is hoisted, the rock wall beam is required to bear such a huge load." Wang Zhilin said, if the rock wall beam is not densely poured and the concrete is not fastened, the consequences are unimaginable.
In order to overcome the challenge, the engineering staff made the facade of the underground cavern of Baihetan "free of decoration".
According to Wang Zhilin, "renovation-free" means that the facade is smooth and delicate, the concrete is poured directly, and there is no need for decoration in the later period to have a ceramic touch.
This is due to the engineering staff's excellence in the selection of pouring formwork and structural layout.
"For example, the choice of formwork. Conventional steel formwork can be reused, but once the formwork is deformed, it will cause potholes in the poured concrete." For this reason, the builders chose a formwork that can only be used twice to ensure pouring. Flat and smooth.
The distribution of precipitation in the Jinsha River Basin is extremely uneven during the year. The annual precipitation is mainly concentrated from May to October, which can account for more than 80% of the annual precipitation.
The Baihetan Arch Dam is located in the narrow valley on the Jinsha River. After the fierce and heavy rains flow into the Jinsha River during the flood season, floods rushed towards the dam.
The maximum discharge volume is 42348 cubic meters per second, the discharge drop is as high as 190 meters, and 90,000 megawatts of energy need to be braked.
Such a large "flood discharge and energy dissipation" is also the most difficult in the world.
In order to solve the problems of flood discharge and energy dissipation under the conditions of narrow river valley and large discharge volume, the East China Survey and Design Institute, which is responsible for the design, used the dam orifice and the bank spillway tunnel to discharge the flood.
Through in-depth research on the maximum discharge volume of the dam body, the engineers reasonably determined the distribution ratio of discharge volume between the dam body and the spillway tunnel on the bank.
Regarding the flood discharge and energy dissipation of the dam body, the engineers comprehensively analyzed the downstream river bed bearing capacity, the arrangement of the dam body orifice, and the influence of the dam body opening on the dam body structure. After verification by a large number of hydraulic model tests, the engineers decided to adopt " The “two-layer orifice of the dam body” is designed to control the maximum discharge volume of the dam body orifice to 30,000 cubic meters per second. The discharge structure has strong super discharge capacity and high operational reliability, which effectively solves the problem of asymmetrical arches with large flood discharge scales. The technical problem of dam body flood discharge and energy dissipation.
"Zero Counterweight" Million Kilowatt Unit
Help carbon peak and carbon neutral
It is understood that the Baihetan Hydropower Station has a total installed capacity of 16 million kilowatts, and eight 1 million kilowatt hydropower units are installed on the left and right banks.
On June 28, the first two units were put into production for power generation.
According to the relevant person in charge of Dongfang Electric Co., Ltd., which developed the generator set, the single unit capacity of Baihetan Hydropower Station is one million kilowatts, which is the largest single unit capacity in the world.
The optimal efficiency of the turbine reaches 96.7%, and the rated efficiency of the generator exceeds 99%, making it the world's highest efficiency turbine generator set.
At the same time, the temperature rise of the stator winding of the unit does not exceed 63K, and the temperature rise of the rotor winding does not exceed 58K, which is the most stringent temperature rise control level in the hydropower industry; the rated voltage is 24 kV, which is the highest voltage level in the hydropower industry.
The core components of the generator set realize intelligent manufacturing.
Zou Yingdong, the relevant person in charge of the process department of Dongfang Electric Co., Ltd., introduced that the production and manufacturing of the core components of the Baihetan generator stator bar, rotor coil, and stator punching piece adopts digital workshop production, which greatly improves production efficiency and greatly reduces operating costs. Product development The cycle is greatly shortened, and the product defect rate and energy consumption are greatly reduced.
Different from the past, the rotating parts of the operating unit consist of tens of thousands of parts and weighing 2600 tons, but after the final assembly, it has achieved "zero counterweight", becoming the world's first giant hydroelectric generating unit without trial operation. The case that the weight meets the quality index is also the first "zero-counterweight" unit in the history of hydropower.
According to Leng Jianhua, the person in charge of the Baihetan project department of Dongfang Electric, the million kilowatt unit consists of runners, rotors, and main shafts, and tens of thousands of parts are assembled.
"If these parts are not produced by a machine tool, there may be slight weight differences. Then there will be torque imbalance deviations when they are turned, and the next step can be entered after the'counterweight'." Leng Jianhua said, but Baihetan Million-kilowatt units have achieved "zero counterweight" and almost no torque imbalance, indicating that they have achieved the ultimate in R&D, design, manufacturing and processing, and installation deviation control.
It is worth noting that all parts and components of hydroelectric power stations have been made domestically.
According to reports, Dongfang Electric has fully summarized past experience and formed the development of a new type of rotor support including unit overall design, runner research and development, core component manufacturing, magnetic pole winding air internal cooling technology, low-loss bearing technology, 24 kV insulation system, and balanced force. A series of independent intellectual property rights and core technologies.
"After the completion of the hydropower station, the average annual power generation will be about 62.4 billion kilowatt-hours, which can save 19.68 million tons of standard coal and reduce carbon dioxide emissions by 51.6 million tons." Wang Zhilin said, this is important for my country to achieve carbon peaks in 2030 and carbon emissions in 2060 on schedule. The neutralization goal will play an important role.
Wang Yongzhan