Time-tested and future-proof
Energy systems around the world are becoming increasingly decarbonized, distributed – and demanding. That’s why HVDC Classic steps into the limelight: It provides transmission system operators with an exceptionally economical and efficient opportunity to supply load centers. Such a bulk power transmission system delivers the required amounts of power, stabilizes heavily strained AC grids, and establishes an interconnected power system across regions and countries. The proven technology behind HVDC Classic, which is based on line-commutated current-sourced converters (LCC), has been continuously improved over the years. Today, HVDC Classic systems from Siemens transmit up to 10 GW of power, this way providing the secure, stable, and profitable backbone for today’s increasingly complex transmission systems as well as for grid interconnection and for UHVDC transmission.
High-performance power highways with HVDC ClassicToday, many transmission system operators are required to provide additional grid capacity and improve grid performance and resilience. They’re also expected to take an active part in the establishment of interconnected power systems and contribute to CO2 emissions reduction through the integration of power from renewable sources. HVDC Classic provides the opportunity to tackle these challenges successfully.
The key to reliable, efficient long-distance power transmission
- Transmission capacity of more than 10 GW per bipolar system at a voltage level of ±800 kV (± 1100 kV)
- Highly efficient converter stations with losses of approximately 0.7% of rated power
- Significantly lower costs for rights of way and overhead lines than with comparable AC solutions
- Possibility to establish a bulk power transmission system bridging more than 2,000 km for infrastructure improvements
- Compensation of dynamic AC system disturbances thanks to high overload ratings
- Grid interconnection capability to support large grids and stabilize parallel AC systems
Efficient bulk power transmissionGrowing power demand and the worldwide push for the decarbonization of energy systems call for new approaches in power transmission. The challenge is to establish bulk power transmission systems to get power from lucrative but far off renewable energy sources right to the load centers. UHVDC transmission technology from Siemens provides the efficient, reliable solution.
How to transmit more power over longer distances at lower losses
At the core of a UHVDC transmission system is the converter. It consists of a number of thyristor modules equipped with Siemens thyristors of up to 6-inch. Typically, the valves of one pole are arranged in two series-connected 12-pulse groups to overcome possible transport limitations. A major benefit of this layout is the relatively small size of the converter transformers. It also increases the redundancy of the bulk power transmission system, as each of the four converters can be bypassed with the assigned DC line still operating at a reduced voltage level of 400 kV.
The next level of HVDC technology was ushered in when Siemens developed its 6-inch thyristor and all other components required for UHVDC converter stations. Thanks to the ability to produce the entire range of components required for 800 kV DC power transmission, Siemens can supply turnkey solutions for complete UHVDC transmission systems.
Yunnan-Guangdong, the world's first UHVDC transmission project, which had been contracted to Siemens by China Southern Power Grid in 2007, started commercial operation of the first pole in December, 2009. The first bulk power transmission system equipped with 6-inch thyristors from Siemens, the Xiangjiaba-Shanghai UHVDC system in China, commenced operation in 2010. Another huge Siemens ±800 kV UHVDC project was implemented in Brazil.