The “Avelin-Gavrelle” overhead power line between the cities of Lille and Arras is vital for the energy supply in the North of France. Next to supplying electricity to over 1,7 million inhabitants and 220,000 employees in over 530 municipalities, the 400 kv line constitutes an important link between the European and French national energy grids. As the line could no longer guarantee future energy supply needs, French grid operator RTE opted to fully reconstruct it over a distance of 30 km. Lamifil was chosen to provide 650 km of AAAC overhead conductors for this crucial high voltage upgrade that was executed with great care for the impact on the environment and local community. Tripling the transport capacity from 1,500 MW to 4,600 MW, the new line will help bolster regional development and drive the energy transition in France.
Line reconstruction benefits local, national and international goals
First built in 1963, the original Avelin-Gavrelle high voltage line had reached its end-of-life in the 21st century. A full upgrade of the line was initiated with three objectives in mind. First of all, securing and improving the region’s electricity supply, the upgrade would directly support the economic development of the Hauts-de-France and the Lille metropolitan regions. Moreover, a new and vastly more powerful connection would facilitate a smooth and increasing exchange of electricity between the region, the French national grid and neighboring countries such as Belgium and the UK. Finally, strengthening the Avelin-Gavrelle line would be vital to support the transition to and development of renewable energy production in the region.
A sustainable solution addressing stakeholder concerns
10 years after the first public debate, reconstruction works kicked off in November 2019. Only two years later, the new line became operational on December 16, 2021. From the very start, the whole project was conceived with great care for the impact on the environment and local community. No stone was left unturned from a conceptual and technical point of view to find solutions to address key stakeholder concerns. Before opting for a full reconstruction, RTE investigated the options of mere reconductoring and underground cables, but these were abandoned due to the scope of the upgrade and lack of possible capacity respectively.
Choosing a low impact and reliable new infrastructure
A first important choice was to plot the new line on a trajectory with the least impact on the local living environment, based on stakeholder meetings and in-depth environmental and landscape analyses. In addition, for the Northern and more densely populated part of the line, 45 Equilibre towers were constructed. These brand new and unique towers are designed to best preserve the living environment, improve landscape integration, reduce the level of electromagnetic fields and the use of agricultural land.
Next to low impact towers, RTE chose an overhead conductor type to match the specific requirements for this project. RTE awarded the contract to its certified partner Lamifil, after assessing proposals based on innovation, sustainability, total cost of ownership, experience and logistics. Lamifil provided a total of 350km of Aster 570 and 300km of Aster 851 AAAC lines. The Aster 851 AAAC conductors were surface treated to limit noise emissions and installed in a triple bundle configuration to further improve noise reduction.
As a fully certified RTE partner, Lamifil performed a number of mandatory mechanical tests in its own accredited lab to verify the conductor’s reliability, safety and durability. A stress strain test was carried out to assess the conductor’s performance in terms of tensile strength and elongation when exposed to increased tensions levels. A breaking load test determined and verified the ultimate tensile strength of the conductor in order to ensure long term reliability under all circumstances, including during installation or when subject to climatic loads. Finally, Lamifil performed an SRE (système de reprise d’efforts) test, specifically required by RTE to validate the compatibility of the UPK working camps with the conductor.
A challenging conductoring project
The reconstruction of the Avelin-Gavrelle line was in many respects quite challenging. As the old line crossed the new line trajectory in over 10 places, it had to be taken down before the new line could be constructed. As a result, a nuclear power plant connection had to be interrupted from September to November 2021. On top of this, the new line included both a crossing with a high-speed train line as well as the A1 Highway, one of the busiest roads in France. Unique cranes were used in order to make the highway crossing with minimal interruptions. In spite of these challenges, this extraordinary conductoring project was commissioned in time as a result of close collaboration between Lamifil and contractors Eiffage, Omexon and SLEH.
Care for the environment and return for the community
The new Avelin-Gavrelle line construction was a major project for the French region, requiring a 215 millions euros investment and generating over 80 millions euros of direct local economic benefits. At the outset, a return for the local economy was realized by involving local contractors. In addition, RTE set up a support plan to fund projects that contribute to local development and directly benefit the region’s inhabitants. Next to dozens of other projects, the renovation of a local swimming pool and schools, the expansion of a library and the construction of a day care were financed through this plan.
Since well into the previous century, Lamifil has been committed to help build the French national grid and address its current and future overhead line challenges. We are excited to have been able to contribute to the essential reconstruction of the Avelin-Gavrelle line, a project with benefits on a local, national and international level.