Offshore cable laying for the UK end of the BritNed electricity link is the latest stage of the ?600m project. It involves the first ever power supply connection between Great Britain and the Netherlands, with cable testing underway in 2010 and full commercial operations planned for 2011.
BritNed is a joint venture between the UK National Grid, which owns and maintains the high voltage electricity transmission system in England and Wales, and NLink, a subsidiary of the Dutch transmission system operator TenneT. The project consists of two bundled high voltage bipolar 1GW capacity cables laid across the Thames Estuary and southern North Sea between the Isle of Grain on the River Medway in the UK and the Maasvlakte near Rotterdam, a distance of 260km.
The link is described as a commercial (non-socialised) interconnector accessible for all market participants with power trading taking the form of explicit and implicit auctions. The former allows participants to buy capacity from BritNed and electricity from traders while with the latter the participants buy capacity and electricity in one single transaction. Benefits include security of supply for northwestern European countries, the environmental advantages of access to a larger supply of green electricity, and market benefits including potential price levelling.
The distance involved requires the electricity to be converted to DC for the journey with conversion to and from AC taking place at convertor stations at Grain and Maasvlakte. Contractor BAM Nuttall is responsible for the civil side of the £23m installation at Grain with associated company BAM Civiel constructing the convertor station at Maasvlakte. Consortium partner Siemens Power Transmission and Distribution is providing the transformers and other electrical components for each facility.
Fareham UK based Red Penguin Associates Ltd is providing marine consultancy services to BritNed with the ABB Group appointed to carry out a range of tasks including the designing, supplying and laying of the cable and UK based Global Marine Systems subcontracted by ABB to handle the actual cable installation work. Papendrecht based Visser & Smit Hanab are carrying out the shorelanding elements of the cable works, with the Dutch end of the connection already underway, including two 29km sections of cable now installed to the shore at Maasvlakte.
The main cable lay vessel involved at Maasvlakte was the 1999 built Team Oman, owned by Topaz Energy & Marine associate Nico Middle East. Global Marine Systems' 2001 built cable layer Atlantic Guardian carried out the survey and touchdown monitoring work with the 2002 built offshore support vessel Edda Fjord, owned by Ostensjo Rederi of Norway, assisting with offshore burial work utilising its Excalibur ROV. Den Helder based workboat owner Acta Marine provided two vessels, the shallow draft workboat Coastal Worker carrying out the inshore burial tasks assisted by the 1987 built Coastal Enterprise, described as an ultra shallow draft craft capable of operation in waters as shallow as 1.1m. A variety of other support vessels were also involved including the TSHD Pearl River owned by the Belgian DEME Group, and the workboat Nova K and pontoon Stemat 63, both from Rotterdam based Stemat Marine Services.
Operations have also been progressing at the UK end of the link. In July the Nova K carried out grapnel clearance runs with the Team Oman laying cable and the Edda Fjord carrying out the subsea trenching and cable burial over a 25km stretch in the inner Thames Estuary between the Nore Sand and western end of the Princess Channel.
The next phase is about to see 63km of cable being laid in the outer Thames Estuary. While the actual vessels involved may change, those earmarked include Dredging International"s THSD Lange Wapper, scheduled to carry out a sand wave pre-sweep over a 25km stretch, with the Atlantic Guardian carrying out grapnel clearance runs. At the time of writing it was still to be decided which Oceanteam BV cable vessel will be laying the cable although trenching and cable burial operations are expected to be carried out by the Edda Fjord.