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Macroduct, Telecommunications – 13. August 2020

Norderney: BorWin5 Grid Connection

The transmission system operator TenneT is building a 900 MW grid connection from the EnBW He Dreiht wind farm to the converter station in Garrel/Ost. The 320 kV DC connection strengthens the German supply network. TenneT is building this DC grid connection with egeplast protective pipes for high and extra-high voltage cables up to 525 kV.

Horizontal Drilling Protects Natural Area

To achieve Germany’s expansion targets for renewable energy, connecting offshore wind farms to the supply grid is of great importance. One of these offshore connections is BorWin5 – a 230 km grid connection linking the EnBW He Dreiht wind farm, north of Borkum, to the extra-high voltage grid on land. The grid connection point is the Garrel substation in the Cloppenburg area. The submarine cable is 110 km long. The underground cable portion is 120 km. For the construction, a joint venture (ARGE) consisting of the companies Matthäi, Beermann, and Matthäi Wasserbau was commissioned by TenneT. The pipeline construction work is being carried out by STRABAG on behalf of the joint venture. The offshore connection runs across the island of Norderney. To protect the sensitive Wadden Sea environment and ensure dike safety, TenneT opted for horizontal drilling on the island. The high-temperature resistant Macroduct High-T in 450 x 61.5 mm is being used here. It is a protective pipe for high and extra-high voltage cables up to 525 kV, featuring increased thermal stability to withstand high thermal stresses. The combination of high flexibility and strength of the PE pipe used offers optimal properties for carrying out these horizontal drillings.

High Demands

The drilling for the HVDC (High-Voltage Direct Current) cable system is being carried out in three construction phases, each with two parallel undercrossings. The first phase was successfully completed in the summer of 2019. Two pipe strings, each 950 m long, were drilled from the lighthouse to the Wadden Sea. The second phase passes under the northern part of the island from the lighthouse to the north beach and will be constructed in the summer of 2020. The length here is 1,280 m. The final section is 1,090 m long, runs from the Wadden Sea to Hilgenriedersiel on the mainland, and is planned for 2021. In addition to the strict requirements for working in a nature reserve, the short execution window and delivery logistics are further challenges. The construction window is open from July 15 to September 30 each year.

Exact Timing

“Due to delivery via ferries and the limited storage space on the island, precisely timed deliveries and direct, unconventional contact with egeplast with short response times are key success factors. Close coordination gave us planning certainty. Reliability is an indispensable component under these conditions,” explains Thomas Schwindeler, Project Manager at STRABAG AG. A smooth delivery process is essential here. All necessary accessory components are supplied by egeplast as a system provider – these include temperature-resistant electrofusion couplers in OD 450 and temperature-resistant stub ends.

Project Description

320 kV DC cable / BorWin5 connection of the EnBW He Dreiht offshore wind farm, grid connection point in Garrel/Ost

Challenges

Installation of a cable protective pipe system for a 320 kV High-Voltage Direct Current (HVDC) transmission

Solution

Use of ege-com® Macroduct High-T PE cable protective pipe system made of PE with increased thermal stability for high and extra-high voltage cables up to 525 kV

Installation

Trenchless construction (HDD)

Pipe System

6,640 m ege-com® Macroduct High-T PE 450 x 61.5 mm
852 m ege-com® Macroduct Mono PE 250 x 34.2 mm
– incl. accessories & electrofusion couplers, loose flanges

Client

TenneT TSO GmbH

Project Participants

Beermann Bohrtechnik GmbH, STRABAG AG, Matthäi Bauunternehmen GmbH & Co. KG, Matthäi Wasserbau GmbH & Co. KG

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