HVDC Classic

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 Energy transmit up to 12 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.

Why HVDC Classic?

High-performance power highways with HVDC Classic

Today, 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 12 GW per bipolar system at a voltage level of up to ± 1100 kV
  • Station 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 fast and flexible control of power flows  
  • Grid interconnection capability to support large grids and stabilize parallel AC systems

Efficient bulk power transmission

Growing 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 Energy 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 Energy thyristors of up to 6-inch. Often, 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, e.g. 400 kV for an rated 800 kV UHVDC system.


The next level of HVDC technology was ushered in when Siemens Energy developed its 6-inch thyristor valve module and all other components required for UHVDC converter stations. Thanks to the ability to produce the entire range of components required for UHVDC voltage up to 1100 kV DC power transmission, Siemens Energy can supply turnkey solutions for complete UHVDC transmission systems. 


Yunnan-Guangdong, the world's first UHVDC transmission project, which had been contracted to Siemens Energy 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 Energy, the Xiangjiaba-Shanghai UHVDC system in China, commenced operation in 2010. Another huge Siemens Energy ±800 kV UHVDC project was implemented in Brazil.

Learn more about HVDC Classic

Download our HVDC Classic brochure to gain an overview of all technical details and possible applications. In addition the flyer provides all Siemens Energy HVDC references at a glance.

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81739 Munich



HVDC Classic: a preferred solution all over the world

Transmission system operators all over the world choose HVDC Classic and rely on Siemens Energy’s unique solution expertise and proven experience in tackling even the most complex challenges.