GRIDABLE project - Technology at the core of future HVDC cables


Autumn 2021

The installation of high voltage direct current (HVDC) technology in electrical power grids has been increasing due to the need to connect electrical power over large distances. In HVDC applications the electrical insulation faces specific challenges differing from those encountered in conventional AC power grid applications due to the stress buildup within the insulation material caused by the constant DC electric field stress.

This phenomenon is referred to as space charge accumulation, one of the most critical phenomena compromising the HVDC insulation reliability and lifetime. In order to secure reliable availability of clean and inexpensive electricity, the EU funded GRIDABLE project started four years ago with the goal of improving the HVDC insulation performance.

The project was concluded on 30th of June 2021 and on 14th of June an online stakeholder meeting was held. Among the many technological and scientific advances of GRIDABLE, the most relevant has been the prototype of a next generation HVDC cable with outstanding insulation properties. In fact, the test results on the HVDC model cable demonstrator show the absence of breakdown in the cable length up to 480kV and the absence of thermal runaway. The results in terms of leakage current measured on the cable are also excellent. For Nexans, one of the industrial partners in the project, the production of such a promising prototype was important to demonstrate the extrusion feasibility on existing industrial lines.

We have interviewed Gabriele Perego and Christelle Mazel, respectively the Nexans’ Scientific Director and the Products Team Leader at Nexans Research Center, who have been working on the project since its inception. We learned that GRIDABLE developed a nanocomposite formulation presenting an extremely low leakage current and no thermal runaway phenomenon. These are exceptional properties and constitute an important progress compared to the commercial reference. Moreover, the breakdown voltage obtained gives the possibility to decrease the thickness of the insulation layer and to obtain a lightweight and more reliable cable. Although the gain in thickness, of the order of a few millimeters, might seem negligible, when scaled up to the length of cables, it entails huge savings in manufacturing costs, making it a highly competitive product once on the market and even more combined with a lighter weight base formulation.

Christelle is very optimistic about future developments. With the initial objective of the project fully reached in terms of level of performance on the HVDC model cable demonstrator, she expects that the new GRIDABLE insulating material will be able to reach extra high voltage for power transmission at rated voltage up to 800kV. To understand why this will be an important breakthrough, consider that current insulation technologies for HVDC power cables based on extruded XLPE can reach a voltage rate of up to 525kV and present huge technical limits such as its maximum conductor temperature 70°C. Moreover, its recyclability is limited.

A remarkable feature of GRIDABLE cables lies in their low environmental burden thanks to the recyclability of the PP based materials. In a policy context characterized by the the green transition led by the EU (and the USA and China seem to be following), this means a larger economic and societal impact of this technology. In September 2020, Nexans disclosed its commitment to minimize the environmental impact of its activities and products and to develop cabling solutions that contribute to preservation of the environment and saving of energy. Therefore, limiting the environmental impact of power cables is a major achievement. Nexans intends to work on further developments of the GRIDABLE technology to meet a key challenge: the compounding of this material on large scale industrial facilities and with a full control of the cleanliness.

Co-founded by the Horizon 2020 Framework Programme of the European Union.