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EQOS Energie executes HTLS overhead line work for the ELIA Group

Modernisation of about 60 kilometres of overhead lines between Belgium and France

The Luxembourg experts of EQOS Energie were awarded the commission for one of the most comprehensive overhead line remodelling projects of the ELIA Group – one of the largest European transmission network operators in the energy sector. Under the project title “Horta”, EQOS Energie will work for the Belgium-based ELIA Group in the area of HTLS overhead line technology for the first time. During this project, a total of 60 kilometres between Belgium and France will be provided with 400-kV HTLS overhead lines (high-temperature-low-sag conductors). EQOS Energie will be fully responsible for the planning, construction, fitting and functional commissioning of two of the four project sections, which extend over six cantons. By exchanging the regular overhead lines with HTLS lines, whose span does not depend on the temperature of the cable, the ELIA Group can benefit from safer, more stable and more highly performant energy transmission in the future. This way, EQOS Energie contributes to the Group’s comprehensive modernisation process and to greater network quality in the entire region. The project starts in November 2019 and will likely be finalised in April 2021.

Virginie Delattre, head of the Overhead Line Construction profit center at EQOS Energie in Luxembourg: “We have implemented numerous overhead line construction projects for the ELIA Group in the past. For us, the Horta project is an exciting cross-national opportunity to contribute our expertise in HTLS overhead line technology. However, the tight timeframe is a challenge. We have a maximum of 24 weeks for each section (i. e. two times 12 weeks of downtime for reasons of maintaining network stability). This is a very short time period when you consider that six separate roll-out phases are required for each section. Therefore, we are banking on perfect planning and coordination as well as core teams and expert know-how that optimally complement each other.”

400-kV HTLS lines: Strong transit potential based on higher thermal resistance

The advantage of 400-kV HTLS lines compared to conventional overhead lines is their significantly higher electrical transit capacity. Due to their carbon core and their aluminium coating, they are able to withstand much higher temperatures. In fact, HTLS cables expand less than regularly used types of overhead lines, which means that the distance between cables and obstacles is reduced, even at high temperatures.

Project execution by EQOS Energie to exchange the overhead lines will proceed in three phases. All planning and preparatory work for exchanging the existing conductors with 400-kV HTLS overhead lines starts in November 2019. “The cable exchange work of Lot 5 will run from March to November 2020,” said Delattre. “The second execution phase will run from July to September 2021. Each roll-out phase must be organised with the greatest precision to ensure that the subsequent work can run smoothly and in optimally coordinated fashion.”