Construction and commissioning
Construction and commissioning covers the civil works, cable laying and, once the construction is over, the testing phase. The building of transmission infrastructure generates economic activity for the promoter’s contractors and subcontractors, and for the local community.
During the building of infrastructure or when conducting maintenance work, some equipment may be temporarily unavailable. Project promoters must coordinate with third parties, including with TSOs in neighbouring countries, to obtain planned outages of the relevant equipment and avoid particularly tense situations on the grid. Regional security coordinators support the cross-border coordination of planned outages by testing all possible combinations of upcoming work to see if any will compromise the grid’s availability, and suggest corrective solutions such as postponing work on certain lines. Projects with PCI status have priority to obtain planned outages.
Kurzeme Ring – Successful cooperation with local communities
The Kurzeme Ring project forms part of the larger NordBalt project implementation, which includes the subsea interconnection between Lithuania and Sweden and transmission network reinforcements in Latvia, Lithuania and Sweden. In service since 2019, it was one of the biggest transmission network projects in Latvia, that significantly improved security of electricity supply in normal and emergency modes or during storms and critical conditions, and provided possibilities for grid connection for new consumers and producers of electricity (mainly offshore wind) in the Western part of Latvia.
Serious difficulties related to nature protected areas were raised during the building of the 2nd stage of the project, an overhead line located close to the Riga area. Initial plans foresaw the demolition and reconstruction of a 110 KV overhead line near Jurmala city built in 1987 with installation of new pylons (no information is available on studies performed before the construction in 1987). However, it appeared that the ground works and the weight of the new pylons could affect underground sulphur deposits and the surrounding protected area. Additional study and ground assessment confirmed that demolishing and rebuilding new pylons was not possible in these conditions, and a compromise scenario was identified jointly by all involved parties including the Latvian TSO, Latvian Government, and the Municipality of Jurmala. The project route was reassessed and relocated to move around the sensitive areas, and an additional switching point was built due to security of supply reasons. The construction works continued and the cooperation and fast reaction between Latvian TSO, Latvian Government and involved municipalities allowed a timely commissioning.
Crossing the Scheldt: Tallest electricity pylons in the Benelux
Elia’s Brabo project is an essential link in strengthening the electrical interconnection with the Netherlands and Western Europe. It will shore up Belgium’s electricity grid at a local, national and international level. The project will increase the grid’s supply capacity, enabling it to cope with growing electricity consumption in the Port of Antwerp. By upgrading Belgium’s north-south axis and bolstering a network of international interconnections, the project will improve international trade opportunities and reduce reliance on Belgian generating facilities.
As part of the Brabo project, Elia had to cross the Scheldt River in the port of Antwerp. For safety reasons, the high-voltage lines had to be at least 100 metres above the surface of the water to leave enough room for ships. Therefore, Elia has erected 192-m high-voltage pylons on both banks of the Scheldt to enable the cables to span the river without disrupting maritime traffic.
The Scheldt crossing is a major technical feat in many respects. To make it possible, a 200-metre-high crane was required to erect the two high-voltage pylons consisting of 584-tons of steel; there are only 11 such machines in the whole of Europe. Elia built a foundation structure comprising of 5,000-ton of concrete to carry the weight of the high-voltage pylons. To guarantee the pressure forces, Elia first made a 3D-print of a scaled model and conducted a wind tunnel test to confirm wind hypotheses.
The conductors cross the Scheldt for a distance of around 911 metres. An extra strong conductor with a steel core was required to support such a crossing. Two ships were sent across the Scheldt River to meet each other in the middle and pass on a nylon rope that Elia used to pull the conductors on the pylons.
Another challenge was to make the pylons fit in the environment, as the mudflats and salt marshes along the Scheldt are a biotope of European importance. 11,000 cubic metres of soil (enough to fill around 110 Lorries) were removed from an area adjacent to the project site so that this part of the left and right banks can flood naturally on a regular basis. This will enable the mudflats and salt marshes to return to their original state, with the help of the river.