Alstom successfully delivers the first unit of the Xiangjiaba hydro power plant

The worlds most powerful hydroelectric unit enters service as Alstom successfully delivers the first unit of the Xiangjiaba hydro power plant.

The unit passed a reliability trial run of 72 hours, and recently began commercial operation.

The Xiangjiaba power plant, owned by the China Three Gorges Corporation (CTG), is designed with 800 MW class Francis turbines and 889 MVA generators each; the most powerful ever built. When completed, the station will have a total capacity of 6400 MW of renewable power generation.

Awarded to Alstom in autumn 2008, the Xiangjiaba contract covered the design, engineering, manufacturing and supervision of erection and commissioning of four 800 MW class Francis type turbine/generator units. 

The units supplied by Alstom incorporate numerous unique technological breakthroughs. The turbine runner, almost 10m in diameter and weighing over 400 tonnes, has an advanced hydraulic design to ensure very smooth machine behavior even in challenging operating zones. 

In order to achieve an optimal generator design at such high power outputs, Alstom provided the worlds first air-cooled 23kV stator windings. Such windings require very high quality raw materials, careful design, and high dimensional precision during manufacturing.

Until recently, only one hydro power plant operated at such a voltage, with windings supplied by Alstom, though using water cooling through the stator windings to evacuate the heat created during electricity generation. The challenge at Xiangjiaba was to build 23kV air-cooled stator windings, which require less auxiliary equipment, space and maintenance.

In-depth research on ventilation and stator windings, including extensive testing of stator bars, were used to validate the design of the generator. The tests during commissioning and now the successful connection to the grid are the final elements which confirm this latest technological breakthrough in the design of very large rotating electrical machines. 

This project is one of the series of successful cooperations between Alstom and China Three Gorges Corporation (CTG), which included deliveries in Three Gorges Left Bank, Three Gorges Right Bank and Three Gorges Underground.

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