Oleg Strashnov Installs Two Substations at Sheringham Shoal Offshore Wind Farm (UK)

The two large offshore substations, each weighing nearly 1,000 tonnes, arrived off the North Norfolk coast at 22:00 the 3rd. of May to be installed at the Sheringham Shoal Offshore Wind Farm.

The substations will channel the energy generated by the Sheringham Shoal Offshore Wind farm to the onshore substation at Salle for distribution into the National Grid.

Construction of the offshore substations was performed by Heerema, Alstom’s subcontractor for construction of the offshore substations at their yard located in Hartlepool, North East England. The complex logistics operation to transport them to the Sheringham Shoal site commenced in November 2010 when they were transferred from the fabrication hall to an outside location.

The operation to get the substations out of the Victoria Quay and on to Dina Launcher, the barge which brought the substations to site required careful planning and precise manoeuvring.

“The conditions were quite challenging,” reports John Short, barge engineer.

He was not only concerned about the swells which measured 2,5 metres, but also worried about the difference between high and low tide which is approximately four metres on average in the area.

“I thought that perhaps the most challenging aspect was to monitor the barge so it wouldn’t touch the sea bottom at low tide. But it went really well,” Short says.

The handover took 30 minutes.

“It was one of the best handovers I’ve ever seen,” the experienced barge engineer comments.

The foundations for the substations were installed in the seabed during Autumn 2010 and the substations were lifted onto their individual foundations by the state-of-the-art crane vessel Oleg Strashnov, which has already been working on site.

The Oleg Strashnov is ideally suited for this major operation; it is 183 metres long, 47 metres wide, can lift up to 5000 tons and can accommodate up to 395 personnel.

The first substation was installed at its location at 23:32hrs the 8th of May and the second substation was lifted onto its foundation at 04:20hrs on the 10th of May. “’The operation was well prepared and everything went according to plan,” says Erik Kringland, vessel representative on the Oleg Strashnov.

Statoil oil and gas experience in offshore installations have been a major contribution to reduce risks in this operation – both in the planning process but also when it comes to the lifting performance.

“We’ve had a strong focus on safe installation together with our contractors. This cooperation has been essential for a successful result,” says project director Elly Kristine Bjerknes.

The successful installation of the two substations is a key milestone in the project. However, this is only the beginning. We have a lot of challenges ahead of us that require detailed planning and coordination, and we are dependent on good weather conditions. In early summer the main hook-up work and commissioning of the offshore substations will start and this is expected to continue throughout the coming months. Erection and commissioning of turbines will begin this during the summer continue through the remaining year and first quarter of 2012.

When completed the Sheringham Shoal Offshore Wind Farm will generated 317MW of electricity, enough to power 220,000 domestic homes. This electricity will be distributed from these two offshore substations via sea bed cables to landfall at the North Norfolk coastal village of Weybourne, and from there by underground cable to a new purpose built substation at Salle, near Norwich, before entering the National Grid.

The Sheringham Shoal Offshore Wind Farm is owned equally by Statoil and Statkraft through the joint venture company Scira Offshore Energy Limited. Statoil is the operator for the project during the development phase. Scira will be the operator of the wind farm.

(scira)

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Source: scira, May 16, 2011