Norderney: BorWin5 Grid Connection
The transmission system operator, TenneT, has decided to build a 900 MW grid connection from the EnBW He Dreiht wind farm to the converter station at Garrel/East. The 320 kV direct current connection is meant to support the German supply network. TenneT has opted in favour of building this direct current grid connection using egeplast protective pipes for high & extra high voltage cables of up to 525 kV.
Horizontal drilling protects natural habitats
Connecting the offshore wind farms to the supply network is very important if the expansion objectives for renewable energies in Germany are to be met. One of these offshore connections is BorWin5 – a 230-km grid connection connecting the EnBW He Dreiht wind farm north of Borkum to the extra high voltage onshore grid. The grid connection point is the converter station at Garrel in the Cloppenburg region. The submarine cable measures 110 kms in length. The total
share of the underground cable is 120 kms. For the construction work, TenneT commissioned a working community comprised of three companies, Matthäi, Beermann and Matthäi Wasserbau. The pipeline construction works are carried out by Strabag by order of the working community. The offshore link runs across the island of Norderney. To protect the sensitive natural environment of the tidelands and to ensure the security of the dyke on the island, TenneT opted in favour of horizontal drilling. In this context, the high-temperature resistant
Macroduct High-T in 450 x 61.5 mm was the product of choice. It is a protective pipe for high and extra high voltage cables of up to 525 kV which provides enhanced thermal stability, enabling it to withstand the high thermal stress involved. The combination of high flexibility and the solidity of the PE pipe
provide the optimum properties required for performing these horizontal drilling operations.
High demands
The drilling operations for the high-voltage direct current transmission cable system are implemented in three construction phases with two underpasses each running parallel to one another. The first construction phase was successfully completed in the summer months of 2019. The drillings from the lighthouse to the mudflats measuring 950 meters each were carried out for two pipe strings. The second construction phase is the segment which crosses under the northern part of the island from the lighthouse to the northern beach and will be implemented in the summer months of 2020. The length involved here is 1,280 meters. The last segment is 1,090 meters long, runs from the mudflats to Hilgenriedersiel (mainland) and is scheduled for 2021. In addition to the more stringent requirements involved in construction work in a conservation area, the limited time slot for execution and the delivery logistics present additional challenges. The respective construction sites will be open from 15th July through 30th September.
Precise timing
“Due to delivery via ferries and the limited storage capacities on the island, exactly timed delivery and direct and easy contact to egeplast, with short response times, are a critical success factor. Close cooperation provided us with planning security. Under these circumstances, reliability is indispensable” Thomas Schwindeler, the project manager of STRABAG AG stated. Smooth functioning of the deliveries is essential. As a system provider, egeplast supplies the entire range of accessories required, with components including temperature-resistant electrofusion couplers in OD 450 as well as temperatureresistant stub flanges.
