Submarine cable systems
Submarine cable systems, HVAC/HVDC, must withstand great mechanical stresses and strains during laying and operation - especially in deep waters. The high cost of any subsea maintenance work leads to a preference for well-proven technology based upon long service experience.
Submarine cables are used for power transmission to islands, across fjords and over the sea over hundreds of kilometers, demanding the strictest quality standards. An extremely important design criterion for Nexans submarine cables is reliability.
The design of submarine cables necessitates detailed and complex engineering, integrating a number of disciplines such as electrotechnical and mechanical engineering, maritime and submarine operations, metallurgy and corrosion expertise etc.
Nexans Norway also supplies power and communication systems to offshore installations from the onshore power grid, where the driver is smaller platforms, reduced manpower and lower CO2 emissions. The first offshore development where this concept was employed was the Troll field in the Norwegian sector of the North Sea in 1995. The installation was a 3-core 52 kV XLPE insulated cable with an integrated fibre optic cable 67 km long.
Nexans Norway has in-house capabilities covering all aspects of AC and DC cable systems. Our skilled staff takes care of all stages of the project, and key personnel follow the entire process from research and development, via the bid phase, through to engineering, manufacturing, testing and installation.
In 2008/2009, Nexans supplied and installed, for the BP Valhall project, 292 km of HVDC-IRC submarine cable, and a separate fibre optic cable, with associated equipment, for both the shoreside installation and the platform. This is the world’s first offshore oil field for which all power is supplied from onshore, since electricity production is not possible on the platform. The cables were manufactured by Nexans’ factories in Halden and Rognan and installed using the C/S Nexans Skagerrak cable-laying vessel and the CapJet trenching system. By using power from onshore instead of gas turbines out at the field, BP is saving some 44 million USD in investment costs and a further 7 million USD approx. in annual operating costs. This solution will also minimise the risk of fire and explosion and reduce noise and vibration.