Environmentally compatible connection to the extra-high-voltage grid

Horizontal Drilling Protects Natural Area

In the course of the realization of the grid connection systems via the Baltrum corridor, the flood protection systems, dunes and particularly sensitive areas (for example, seagrass meadows) in the area of the mainland near Dornumergrode and in the following years the island of Baltrum must be crossed at its eastern end.

In deviation from previous offshore projects, the projects of the 2 GW program (= transmission capacity) are being realized with a higher voltage of 525 kV. In these lines, a so-called “metallic return conductor” is also laid. Overall, one route consisting of three boreholes (positive, negative pole and metallic return conductor) is required per grid connection system for each crossing section.

As part of the offshore grid connection projects BalWin3+4 and LanWin1, routes are being laid across the island of Baltrum to the mainland. To protect the sensitive Wadden Sea natural environment and ensure dike safety, TenneT opted for horizontal drilling to cross beneath the island and the dike structures. For these horizontal drillings, the high-temperature-resistant egeplast Power Protect PE-RT in 450 x 61.5 mm is used. It is a protective conduit for high- and extra-high-voltage cables up to 525 kV, featuring increased thermal stability to withstand the high thermal loads. The combination of high flexibility and strength of the PE pipe used offers optimum properties for carrying out these horizontal drillings.

High requirements met by egeFit®

Due to the limited working areas near the flood protection dikes, the dike foreland and the island of Baltrum, the required total lengths of the pipe strings were halved and the two partial strings were connected before drilling using egeplast connection technology egeFit® – “Golden Seam” connector. The long drilling routes did not allow any reduction in tensile forces, meaning that the “Golden Seam” was modified, thus preventing a reduction in tensile force. The modified “Golden Seam” was integrated directly into the pipe string.