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27.06.2007 
Siemens will build China’s highest-capacity direct current power line. The
link will transport electricity over a distance of 1,400 kilometers to the
Pearl River delta in the province of Guangdong, where it will supply energy
to Hong Kong, Shenzen and Guangzhou — megacities with a total population of
about 30 million inhabitants. Siemens’ share of the contract is more than
ˆ300 million.
The high voltage direct current (HVDC) system that Siemens and its Chinese
partners have been commissioned to build will usher in a new era of power
transmission: It will be the first such system to transmit electricity at a
voltage of 800 kilovolts and with a capacity of 5,000 megawatts. The higher
voltage allows more capacity to be transmitted at considerably fewer losses.
The HVDC lines currently operated by Siemens have a voltage of 500 kilovolts
and a transmission capacity of up to 3,000 megawatts. One benefit of the system
is that the energy for the HVDC line is generated by hydroelectric plants in
the province of Yunnan, which means no carbon dioxide (CO2) will be emitted.
Without the new transmission line, the energy would have to be generated by
new power plants using fossil fuels. As a whole the new system will therefore
prevent more than 30 megatons of harmful CO2 emissions every year.
HVDC transmission is better than alternating current for above-ground lines
covering 7 00 kilometers or more. This is because the additional cost incurred
for converter stations is offset by lower transmission losses. A special feature
of the Siemens system is its light-triggered thyristors, which are very reliable.
Another advantage of high-voltage transmission is that the flow of energy can be
"steered" as desired. This enables the facilities to stabilize other connected
networks and help prevent disruptions.
The new long-distance transmission line is the fifth such facility from Siemens
in China, which is the world’s largest market for high-voltage transmission.
According to experts, this transmission technology will become increasingly
important as energy demand increases worldwide. In the future, HVDC systems
could help to exploit reserves of regenerative energy, whose sources (power
plants using wind, water or solar energy, for example) are located far from
consumers.
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