© TenneT
Ecologically sound connection to the extra-high voltage network
In the summer of 2024, TenneT set out to connect as many as three offshore wind farms off the island of Baltrum to the extra-high voltage network. The new 525-kV DC connections for the 2-GW offshore grid connection projects BalWin3+4 as well as LanWin1 will strengthen the German power grid and increase the share of green electricity. As a protective pipe, the egeplast Power Protect PERT featuring 450 x 61.5 mm was selected – using horizontal drilling to protect the natural environment.
Three offshore network connection projects featuring a total route length of 795 km, 530 of them at sea – off the island of Baltrum another milestone on the way to ensuring supply with green electricity was initiated in the summer of 2024. Connecting BalWin3+4 and LanWin1 to the extra-voltage network strengthens the German electricity grid and represents another step towards the energy transition.
Connecting offshore wind farms to the extra-high voltage grid requires so-called grid connection systems. For the 2-GW offshore grid connection projects BalWin3+4 as well as LanWin1, the transmission network operator, TenneT, carried out horizontal drilling from the land side of the embankment to a work pontoon in the tidal mud flats in summer 2024. The grid connection of these projects will be in Unterweser and Wilhelmshaven. The 525-kV DC connections will boost the German power grid in the future. TenneT builds these DC grid connections with egeplast protective pipes for high and extra-high voltage cables for up to 525 kV.
“The new connections will strengthen the German power grid and increase the share of green electricity.”
Heiner Dokters
Horizontal drilling protecting the natural environment
In the course of the realisation of the grid connection systems via the Baltrum corridor, the route traverses the flood protections systems, dunes and particularly sensitive areas (e. g. seagrass beds) in the mainland area next to Dornumergrode as well as the East end of the island of Baltrum in the subsequent years. Notwithstanding the previous offshore projects, the projects related to the 2-GW programme (= transmission capacity) are realized with a higher voltage amounting to 525 kV. These power lines are installed with an additional so-called “metallic return collector“. All in all, one route each consisting of three drillings (plus and minus pole and metallic return collector) per grid connection system are required for every underpass section.
The offshore connections will run from the island of Baltrum to the mainland. To protect the sensitive environment consisting in the mud flats and to guarantee the security of the dyke, TenneT opted in favour of horizontal drilling to cross under the island and the embankments. For these horizontal drillings, the high temperature-resistant egeplast Power Protect PE-RT, 450 x 61.5 mm are used, a protective pipe for high- and extrahigh voltage cables of up to 525 kV featuring enhanced thermal stability and designed to withstand the high thermal loads involved. With its combination of high flexibility and stability, the PE pipe used here provides the optimal properties for the execution of these horizontal drillings.
The route length for BalWin3 totals 245 kilometers, 200 kilometers thereof at sea and 45 kilometers onshore. BalWin4 features a route length of 275 kilometers, 165 kilometers at sea, and 110 kilometers onshore. The route of LanWin1 is also 275 kilometers long, 165 kilometers at sea and 110 kilometers onshore.
For the purpose of executing the construction works, a consortium consisting of MATTHÄI Bauunternehmen GmbH & Co KG, MATTHÄI Wasserbau GmbH & Co KG, Bohlen & Doyen Bau GmbH and Beermann Bohrtechnik GmbH was commissioned by TenneT. The pipeline construction works are executed on behalf of the consortion by MATTHÄI and Bohlen & Doyen.
egeFit® fullfilling high requirements
In view of the limited working space around the protective dykes, the embankment foreland and the island of Baltrum, the required total lengths of the pipe strings were halved and the two partial strings connected with the help of the egeplast joining technology using the egeFit® connector, the “Golden Joint”, prior to the drilling process. The long drilling routes did not allow for any reductions of the tensile forces, thus modifying the “Golden Joint“ and thereby preventing a reduction of the tensile force. The modified “Golden Joint“ was integrated directly with the pipe string.
egeplast
Power Protect PE-RT
| Protection layer pipes for high and very high voltage cables featuring a low-friction internal layer and individual identification markers. |
| UV-resistant signal colour layer |
| Solid wall or coextruded, optionally with stripes |
| Inspection-friendly inner layer: optionally low-friction or abrasion-resistant |
egeplast
egeFit® connection technology Golden Joint
| “Golden Joint” |
| No obstracting weld seam! |
The egeFit® “Golden Joint“ prevents a reduction in tensile force where space is limited. The “Golden Joint“ is generated by means of a specifically designed integrated recess which automatically receives the inner bead. Subsequent removal of the weld bead can thus be done without. This type of connection is particularly suitable for connecting relatively long pipe strings if space at the construction site is limited. The “Golden Joint“ is available as a built-in integrated solution with Power Protect pipe strings. Serving as an adapter, the connector piece can be welded flexibly onto any pipe end.
Projectdata
| Project description | 525 kV DC cables / LanWin1; BalWin3 and BalWin4 Connection of the offshore wind farms to the network node point in Unterweser or Wilhelmshaven resp. |
| Challenges | Construction of a cable conduit system for 525 kV extra-high DC transmission (HVDC) by means of connecting pipe strings > 600 m |
| Solution | Protect PE-RT cable conduit system made of PE with enhanced thermal stability for high and extra-high voltage cables for up to 525 kV combined with egeFit® – “Golden Joint“ connector with and without pressure reduction factor |
| Installation | 2023 – 2030 |
| Construction phase | Closed construction (HDD) |
| Pipe system (2024) | 10.632 m egeplast Power Protect PE-RT 450 x 61,5 mm 1.380 m egeplast Power Protect PE 280 x 38,3 mm 16x egeFit® – “Golden Joint” connector 450 x 61,5 mm; 2x egeFit® – “Golden Joint” connector 280×38,3 mm Electrofusion couplers, loose flanges, additional accessories |
| Parties involved in the project | Client: TenneT Offshore GmbH Execution Matthäi Bauunternehmen GmbH & Co. KG, Matthäi Wasserbau GmbH & Co. KG, Bohlen & Doyen Bau GmbH, Beermann Bohrtechnik GmbH |
Contact
Heiner Dokters
Head of Sales Infrastructure & Energy Solutions
Tel. +49 2575 9710 141
heiner.dokters@egeplast.de
Michael Große Hokamp
Product Management Cable Protection Systems
Tel. +49 2575 9710 180
michael.grossehokamp@egeplast.de
