The world’s first transformer, which Siemens developed and manufactured for high-voltage direct-current (HVDC) transmission systems with what is currently the highest transmission voltage of ± 1,100 kilovolts (kV), recently passed its type test. Siemens developed, manufactured and tested the HVDC transformer in its transformer factory in Nuremberg. It is the first of a total of seven ±1,100 kV transformers that Siemens and a partner company are building for what is currently the world’s largest HVDC transmission system. This type of transformer is among the most powerful single-phase units in the world, with a transmission capacity of 587.1 megavolt amperes (MVA). Siemens is building the transformers in its network of factories led by its Nuremberg plant, in cooperation with its factory for HVDC transformers in Guangzhou, China, as well as another Chinese partner. These factories are manufacturing the machines according to the specifications and documentation of the lead factory in Nuremberg. Commissioning of the world’s largest HVDC link – and thus also the transformers – is scheduled for 2018.
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 3,284 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.