Voltage transformation

Siemens

has successfully completed testing of a new transformer for the world’s first ultra-high-voltage DC transmission system (UHVDC). According to Siemens, it is the first transformer for a 800kV HVDC.

High-voltage DC transmissions systems (HVDC) have the advantage of operating at a lower cost and transmit power over greater distances than AC systems. Current HVDCs operate at a standard transmission voltage of 500kV.

The increase in the system’s voltage proved challenging to engineers at the Siemens facility in Nuremberg. To construct the 800kV transformers, a new, specially air-conditioned production hall had to be built to prevent the insulation from absorbing moisture from the atmosphere during assembly.

Siemens is supplying 10 high-performance transformers for the Yunnan-Guangdong HVDC system on the south coast of China. From mid 2012 onwards the transformers will generate 5,000MW of power over a distance of 1,400km.

Siemens also has an order for 10 UHVDCs for the HVDC transmission system between the Xiangjiaba hydroelectric power plant in south west China and Shanghai. These units will transmit 6,400MW over a distance of more than 2,000km.