The power plant poses a formidable challenge: The power generated must be transmitted in the power plant cavern in a vertical tunnel over a distance of about 220 meters. Unlike a high voltage cable, a GIL features a special design that does not entail a risk of fire. A GIL’s transmission losses are lower than those of high voltage cables or overhead lines. The gas insulation system remains practically unaffected by the passing of time, so the simple, nearly maintenance-free construction ensures a long service life. In addition, the GIL tubes are produced using seamless welding along their entire length. This not only boosts operational safety; it also lends the GIL a certain degree of flexibility. This means it can, if needed, conform to changes to the tunnel wall. GILs can be used for any kind of terrain, including long distances or inclines as well as vertical sections.

Jinping I is a hydropower plant currently under construction in Sichuan province in southwestern China. When it goes into operation, which is scheduled for 2012, the plant will be able to transmit 3,500 megawatt of power at a voltage of 500 kilovolts (kV). The gas-insulated transmission lines installed by Siemens for the power transmission consist of three three-phase GIL systems, each 350 meters in length, which connect the high voltage switchgear in the power plant cavern at the foot of the dam wall and the overhead line that transmits power to the surface. Gas-insulated high voltage lines are part of Siemens’ environmental portfolio, with which the company generated nearly €19 billion in sales in fiscal year 2008.
 
Reference Number: IN 2009.02.4e