Cable damage at British offshore wind farms

 The offshore wind farm London Array has been fighting with problems with its export cables. (Photo: London Array)
The offshore wind farm London Array has been fighting with problems with its export cables. (Photo: London Array)

The operators of the British offshore wind farms Thanet and London Array are currently fighting with damage to their export cables. In both cases, repairs have been entrusted to the cable specialists from Visser & Smit Marine Contracting (VSMC) in the Netherlands.

In March, fate struck the export cable of the wind farm London Array in the Thames estuary. “During the laying of the second export cable, it was damaged by the leg of an installation rig which was being jacked up to install a turbine,” said Joanne Haddon, media manager for London Array. The foot plate pressed the cable into the sea bed. The installation of the first of 175 turbines commenced at the beginning of the year. Haddon: “The affected section needs to be replaced. How long it takes, will depend on the availability of a suitable cable-laying vessel.”

Vattenfall experienced a similar misfortune at its Thanet wind farm. “In 2011, routine inspections revealed a kink in one of the two export cables. That could have led to more extensive damage, and so the affected section was replaced by November 2011,” says Vattenfall press spokesman Lutz Wiese. In the meantime, a further kink has been discovered in the same cable, which now needs to be patched up a second time. During the repairs, the wind farm is only operating at half-power. “We can switch electricity transmission to the second export cable, but that means reducing the export by half,” Wiese explains.

VSMC had a vessel converted at short notice to tackle the repairs, because it is almost impossible to charter a free cable-layer. At a recent cable conference in Bremen, Ton Geul from VSMC suggested that the energy branch should invest in a maritime task force similar to that of the telecommunication sector. The latter holds vessels on standby and cable replacements in stores around the world. “If no vessels and cables are available, the repairs could take months,” he warned.(Torsten Thomas)

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