FEATURE
World ’ s first 1,100 kV HVDC transformer
On January 24 , 2018 , the most powerful high-voltage direct-current ( HVDC ) transformer began its journey from the transformer factory in Nuremberg , Germany , to China . The transformer will first be transported to the harbor in Nuremberg by special heavy load transporter , where it will be loaded onto a ship . Its journey will take it to Rotterdam via the Main-Danube Canal , and from there it will be shipped to China , where it will arrive after several weeks on the high seas . In July 2016 , Siemens received an order to manufacture four transformers of this type . About a year later , the world ’ s first 1,100 kV transformer was completed and successfully passed the tests in the testing facility . The enormous dimensions of the transformer – 37.5 meters long , 14.4 meters tall , and 12 meters wide – posed a logistical challenge for the team . In operation , the transformer weighs just under 900 tons and its efficiency is well above 99 % of the rated power . For the first time , the transformer will enable a high-voltage directcurrent ( HVDC ) transmission with low losses over a record distance of 3,284 kilometers with a transmission capacity of 12 gigawatts . HVDC transformers are part of the converter station that convert alternating current into direct current at the beginning of the transmission line and convert it back again at the end of the line . The conversion from alternating current to direct current helps to transmit energy over long distances with low losses . Transformers are key components of an HVDC line : Thanks to the transformer , the Changji- Guquan project will be able to transmit direct current with a huge 1,110 kilovolts for the first time in the world . The new transformer not only makes the transmission of this record voltage level possible , but it is also the world ’ s most powerful tested transformer with a capacity of 587 megavoltamperes . Siemens has thus achieved a new dimension in high-voltage direct-current transmission . The HVDC line between Changji and Guquan will be operated by State Grid Corporation
( SGCC ), a Chinese grid operator .
The transformers will be installed in the Guquan converter station of the HVDC link between the Chinese cities of Changji ( Xinjiang ) and Guquan ( Anhui ). This is the world ’ s most powerful HVDC transmission system in terms of transmission capacity , voltage and length . It will transmit power with a DC voltage of ± 1,100 kV for the first time anywhere in the world . The HVDC link is 3,324 kilometers long and will transmit electricity from the northwestern Xinjiang region to Anhui Province in eastern China . With a transmission capacity of twelve gigawatts ( GW ), it will replace what was previously the most powerful system with a capacity of 10 GW . In these systems , the transformers are used to feed power from conventional AC transmission grids into so-called converter stations . These generate the DC voltage on one side and convert it back to AC voltage on the receiving side . Due to the type of connection to the converters , the transformers will also be loaded with the very high DC quantities of the transmission voltage and current .
Based on many years of experience with HVDC transformers , Siemens further developed all key components of this type of transformer , thus reaching a new transmission level in HVDC technology . The workflows for manufacturing and testing this product were challenging due to the transformer ’ s extreme dimensions ( LxWxH : 37.5 m x 12.0 m x 14.5 m ). Nevertheless , the ± 1,100 kV prototype was able to pass every test in terms of functionality , emissions and load level . The type-tested HVDC transformer is now being prepared for its long journey to China by road and sea .
The connection is expected to begin operation in 2019 . www . siemens . com
34 Global MDA Journal may 2018