Siemens says that has become the technology leader in the high voltage electricity industry following successful completion of tests on the world’s first 800 kV converter transformer.
The unit is now ready for delivery to China, where it will be deployed in the Yunnan-Gunagdong high voltage direct current (HVDC) transmission link.
Siemens is contracted to deliver a total of ten 800 kV converter transformers for this link, as well as ten units with a DC voltage insulation voltage of 600 kV. The Yunnan-Guangdong link will transport 5000 MW of power over 1400 km from southwest China to Guangdong province in the south.
The link is one of the highest-rated transmission interconnections in the world and is scheduled to start operating in 2010. It will be the first in the world to transport electricity at a DC transmission voltage of +/-800 kV.
Converter transformers are a core element of HVDC systems and manufacturers have been gradually increasing operating voltages in order to help operators to reduce system losses. Most HVDC systems today operate at 500 kV. “Thanks to enormous technical efforts we have been able to increase the efficiency of these high-tech transformers by 20 per cent,” said Bertram Ehmann, CEO of the Transformers Business Unit in the Siemens Energy Sector.
The research and development work focused primarily on meeting the exceptionally high standards demanded for the insulation systems of these high-tech transformers, says Siemens. For example, because of the necessary insulating clearances in air, the two valve bushings carrying the conductors connecting the transformer to the converters are 14 m long. Another important consideration was the factory testing facility, which had to be adapted to handle the huge increase in the voltage necessary to test this new kind of transformer and to be able to perform the final testing.
As part of an additional order, Siemens will deliver ten extra-high voltage converter transformers, five of them rated at 800 kV, for the converter station on the generator side of the future HVDC transmission link from the Xiangjiaba hydroelectric power station in the south west of China to Shanghai on the country’s east coast. This link will have a transmission capacity of 6400 MW and a length of more than 2000 km.
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