Nexans, the worldwide leader in the cable industry, has been called in by EnBW (Energie Baden-Wurttemberg) to use its specialized Capjet trenching system to protect the HV (high voltage) subsea power export cables for Baltic 1, Germany's first commercial offshore wind farm.
The Baltic 1 wind farm, comprising 21 wind turbines with a total capacity of 48 MW, is located around 16 km offshore from the German coast. The electricity produced by the wind farm is connected to the onshore grid by three 170 kV AC cables that make landfall close to the city of Rostock.
Because of the relatively shallow waters in this area of the Baltic Sea (typical depths range from 16 to 19 metres) it is vital that the power export cables are protected against damage by sea anchors and fishing activities. So in December 2010, Nexans started work on a four-week contract to protect a total length of some 50 km of cables by burying them into the seabed to a depth of around 1.5 metres.
Capjet in-house trenching system
The Baltic 1 cables are being buried by Nexans' specialized trenching system, developed in-house and known as Capjet. This uses a water-jet system both to create a trench and to propel the trenching machine.
The Capjet system is used for trenching umbilicals, power cables and fibre-optic cables as well as pipelines. Capjet fluidises the seabed material to create the trench - the fluidised material then falls back on top of the cablel as back-filling after the machine has passed. The cable does not pass through the machine, and no forces are directly applied to it - there is therefore no risk of damage to it during the trenching process. The machine is capable of trenching in most clay and sandy soil conditions and Nexans' Capjet machines have trenched a total of well over 8,000 km of umbilicals, cables and pipelines.
Complete trenching service for hire
Nexans originally developed the Capjet trenching technology to protect its own cables as part of a complete turnkey service for subsea power links. However, Nexans is now offering Capjet as a separate, standalone service for contract hire by other cable OEMs or contractors.
The Capjet service operates from the Nexans offshore cable development and production facility in Halden, Norway. But it can be deployed anywhere in the world either on Nexans' own vessel or on a host vessel with DP (Dynamic Positioning) and is supported by Nexans' own highly trained and experienced team of operators who can operate Capjet on a 24/7 basis if required.
"The BorWin 1 trenching contract reflects the growing interest worldwide from customers wishing to take advantage of our Capjet service on a contract-hire basis", says Trond Steinskog, Nexans sales Manager Offshore Wind Farms and Trenching. "Not only does this service help address the current shortfall in trenching capacity, it also provides a very cost-effective route for customers to adopt the very latest in efficient and environmentally-friendly cable trenching techniques."