High-voltage direct current (HVDC) power links are now able to utilize Nexans state-of-the-art XLPE cables that are qualified to 320kV, while type testing at 525kV has just been successfully completed. At the same time Nexans has qualified the first 600kV mass impregnated cable with a paper-based insulation.

Nexans’ focus on HVDC cables is driven by the growing interest in the world for HVDC power links. Typically these are grid interconnections with land or submarine sections, connections for offshore wind parks and the anticipated electric highways that will provide very-high capacity links bringing electricity from remote renewable sources to areas of consumption. HVDC links will therefore play a key role in the reduction of the global carbon footprint by allowing consumers to access renewable energy while minimizing transmission losses.

Nexans has responded to these challenges by developing three cable technologies to provide transmission system operators (TSOs) with the most appropriate solutions for their HVDC links: XLPE insulation, mass-impregnated paper insulation and superconductors. Three major milestones have been met with the first two technologies.

XLPE cable technology qualified for 320kV and type tested at 525kV

Nexans has fully qualified land and submarine XLPE cable system technology for 320kV through the combination of type tests and long-term pre-qualification tests, all carried out according to international standards. The same technology principle was applied to achieve a step up in voltage, which led to the successful completion of a type test at 525kV. This world-class result demonstrates the potential of the Nexans technology for DC links at all voltage levels currently requested by customers and lays the ground for further achievements.

Mass impregnated cables now ready for 600kV

Mass impregnated HVDC cables are the preferred solution for long-distance submarine transmission of large amounts of electrical energy at the highest voltages. Recent examples include the 100km subsea element of Canada’s new 900MW interconnection to be constructed between Labrador and Newfoundland. The same cable design is also being used for the Skagerrak 4 interconnector between Denmark and Norway.

Through the decades mass impregnated cable technology has delivered excellent service for a large number of power transmission links operating at voltages up to 525kV and a power rating exceeding 800MW per cable. To meet the demand for even higher power ratings, Nexans has qualified the first 600kV mass impregnated cable with a paper-based insulation providing a power transmission capacity of 1,900MW in a bipole configuration. This achievement consolidates Nexans’ leading position in the mass impregnated HVDC cable business, and proves that such cables are highly competitive for the future realization of high-power HVDC transmission systems.

Superconducting power cables for DC systems

Nexans is also the world leader in the field of superconducting power cables. Further to successful tests some years ago at 200kV, Nexans is engaged in the European project Best Paths aiming at developing a 320kV DC cable system with a capacity of 6.4GW per bipole, which represents the combined production of multiple nuclear reactors.

This ongoing project will set the basis for the next generation of electric highways and offers innovative solutions to transfer the full transmission power of a HVDC overhead line corridor into one cable system.

"These technological achievements demonstrate the efficiency of the organization we recently put in place to speed up developments in the field of HVDC systems", said Jean-Maxime Saugrain, chief technical officer of Nexans High-Voltage and Underwater Cables Business Group.

"The cable systems we have developed and successfully tested up to 525kV and 600kV are just the tip of the iceberg. A major effort was made to address specific issues in HVDC systems, in particular issues related to accumulation and mobility of electrical charges. This is of key importance for the long-term reliability of HVDC cable systems and therefore for the satisfaction of our customers."