PEX HVDC underground transmission cables

Energy- and resource-efficient power transmission

The German power grid is subject to an extensive process of change in the course of the energy transition. The constantly increasing integration of renewable sources of energy and the associated fluctuating and decentralised nature of generation and feed-in demand a change in thinking and the restructuring of the power transmission system. In order to create a solution for this problem, the test centre for high voltage direct current (HVDC) transmission at the Technical University of Dortmund is researching materials for next-generation HVDC underground transmission cables, which will allow more efficient and secure power transmission.

The expansion of the power grid is fundamental to the success of the energy transition. According to the Federal Ministry for Economic Affairs and Energy (BMWi), more than 7,500 kilometres of the transmission grid need to be optimised, reinforced or rebuilt over the coming years. The reasons for this lie in the constantly growing proportion of renewable sources of energy involved in power generation and the decentralisation of production to numerous widely-dispersed plants, which tend to be a long way from the centres of consumption. HVDC transmission technology takes on a particular role in this scenario, since, in addition to providing low-loss power transmission over long distances, it also makes it possible to better compensate for the voltage and current fluctuations caused by the volatility of energy supply from renewable sources. For this reason, the Technical University of Dortmund is working in collaboration with Südkabel GmbH to research and develop materials for HVDC underground transmission cables and their casings. In the course of the project, concepts for measuring and testing technology are being developed to investigate the material properties and determine the interactions in various conditions. Verification of the practical application of the technology is carried out in the newly-opened test centre for HVDC transmission at the Technical University of Dortmund.

Engine for progress:

  • Research and development of materials for next-generation HVDC transmission cables
  • Expansion of the field of application of HVDC transmission technology towards higher voltage levels
  • Innovative use of PEX insulation for HVDC transmission cables with voltage levels of over 320 kV
  • Resource- and energy-efficient power transmission

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Photo: TU Dortmund/ Berns

Induction heating system with reference and main loops, coupling high voltage up to 800 kV.

Higher voltage levels, innovative insulation

Compared to conventional cables for high voltage AC transmission, HVDC transmission technology offers considerable benefits: it reduces transmission losses in power transport, facilitates better control of the grid and allows greater transmission capacity for the same copper diameter. The new 525-kV cables produced by other manufacturers have not yet been verified in terms of their sustainability. With the research results from the project, it should be possible to use the technology at higher voltage levels such as 640 kV and above. In addition, a new type and preparation of insulation is used: cross-linked polyethylene (PEX). This is not only lighter and sturdier, but also more eco-friendly than the previous design which was insulated with lead-sheathed, oil-impregnated paper. Avoiding this technique minimises the risk of environmental damage in the event of a fault.

Climate protection par excellence

With the results obtained in the project, conditions will be laid for a new generation of HVDC transmission cables in Germany. This will not only make a substantial contribution to the success of the energy transition; in addition to supporting the integration of renewable energy, using this technology and innovative method of insulation will also preserve valuable resources and reduce environmental pollution.

Photo: TU Dortmund

“The development and testing of materials for cross-linked polyethylene (PEX) cables is an important target in terms of the sustainability and operational safety of HVDC transmission cables and their casings. The experimental set-up helps to verify the theoretical models in practice.”

Prof. Frank Jenau, Chair of the Institute of High Voltage Technology at the Technical University of Dortmund

Partners and sponsors

  • Südkabel
  • Forschungszentrum für Hochspannungs-Gleichstrom-Übertragung (HGÜ)
  • Ministerium für Innovation, Wissenschaft und Forschung (MIWF)
  • Bundesministerium für Wirtschaft und Energie (BMWi)