Siemens Energy has completed the testing and installation of a high-voltage gas-insulated line (GIL) for the Jinping I hydropower plant, which is claimed to be the world's tallest hydropower plant.
With a single pole tube length of 3.2km, the specially-designed GIL features a vertical section measuring around 230m, with three parallel systems spanning the shaft and transits 3,500MVA of power at a voltage of 550kV.
The GIL project includes three, three-pole GIL systems from Siemens installed vertically in two shafts and each system can safely and efficiently transmit 2,200MVA to the overhead power lines, ensuring a reliable grid connection of the plant at the cavern floor.
The line's high performance component allows the transmission of a high amount of energy than cables, and for this plant, transmission will take place between the base of the 305m high dam wall and the overhead line at the dam's water level.
Siemens has carried out welding of GIL's non-flammable aluminum tubes at self-installed temporary tarpaulins and maintained site cleanliness throughout the installation, though the high-tech welding process requires clean-room conditions that is challenging at the construction site.
The GILs are suitable for cavern power plants as fewer systems are required due to their large transmission capacity, their tunnel shafts reduce the transmission route space, and the tunnel for such lines can also be used as ventilation and service shafts, the company claims.
Located in the Liangshan Yi district of the Sichuan province in China, the 3.6GW has commenced electricity generation in August 2013 for Yalong River Hydropower Development.
The underground hydropower plant is a key element in the Southern Corridor of the West-East electricity transfer project in China.