Siemens Energy, together with local partners, is to deliver 10 extra-high voltage converter transformers, five of them rated at 800 kV, for the future HVDC transmission link from the Xiangjiaba hydroelectric power plant in Southwestern China to Shanghai on the east coast of the country. With a transmission capacity of 6400 MW and a length of more than 2000 km (1240 miles), the planned HVDC transmission link will have the highest capacity of any such system in the world, and will also be the longest, according to Siemens. The order has been placed by the State Grid Corp. of China and has a value for Siemens of about 160 million euros. Completion is scheduled for 2011. Siemens will also be providing 6-inch thyristor valve technology for one of the two converter stations.

To further minimize the transmission losses of the HVDC system, it will be operated at a transmission voltage of +/- 800 kV.

"With the further development of our HVDC transmission technology, especially with respect to the 800-kV voltage level and converter technology based on the new 6-inch thyristors, we will enable our customer to transport large amounts of energy in an environmentally friendly manner with low loss,” said Udo Niehage, CEO of the Power Transmission Division in the Siemens Energy Sector.

The 10 HVDC transformers that Siemens is delivering for the Fulong converter station in Sichuan at the Xiangjiaba hydroelectric power plant will be built at the Nuremberg transformer factory, which specializes in the manufacture of converter transformers among other products. This applies particularly for the newly developed 800-kV HVDC transformers.

Siemens is equipping the valve towers of the Fulong converter station with the latest generation of 6-inch high-performance thyristors, without which the low-loss transmission of the very high direct current voltages required here would not be possible at all.

In June 2007, Siemens won an order from China to construct an HVDC transmission link together with Chinese partners between the province of Yunnan in southwestern China and the southern Chinese province of Guangdong. When this system goes online in mid-2010, it will be the first in the world to transmit electricity at a DC voltage of +/- 800 kV over a distance of 1400 kilometers (870 miles).