Uraduct. 5.4.11.16 Inter-array cable protection: cable crossings.
221. It has been anticipated that there will be up to ten inter-array cable crossings within the East Anglia THREE site. Where cable crossings occur they will be protected using the methods as used for cable protection when cable burial is not possible (as described in section 5.4.11.5). The anticipated maximum footprint of cable crossing within the East Anglia THREE site would be 720m2 with the maximum height of 1.5m.
5.4.11.17 Inter-array cables: hook up methods to wind turbines
222. It is planned not to use divers for cable installation. The hook up would be done by the support of ROV vehicles.
223. A typical methodology for installing the cable into a J-tube is as follows. However, alternative cable entry details and installation methods are being considered.
A cable barge or a specialist cable installation vessel would be mobilised to the site. The cables would be supplied either on cable reels or as a continuous length.
The vessel transits to site and takes up station adjacent to a wind turbine structure and either holds station on DP or sets out a mooring pattern using anchors. A cable end is floated off from the cable reel on the vessel towards the wind turbine and connected to a pre-installed messenger wire in the J-tube. The messenger wire allows the cable to be pulled up the J-tube.
The cable is pulled up the J–tube in a controlled manner with careful monitoring. When the cable reaches the cable temporary hang-off (at a later date a cable jointer would terminate the cable and install the permanent hang-off), the pulling operation ceases and the cable joint is made. The cable is laid away from the J-tube on the first wind turbine towards the J-tube on the second wind turbine.
When the cable installation vessel nears the J-tube on the second wind turbine structure, the cable end is taken from the reel, ready for pulling up the J-tube.
The cable end is attached to the messenger wire from the bellmouth of the second J-tube. A tow wire is taken from the cable installation vessel and connected to the messenger line at the top of the J–tube and the pulling operation is repeated in the same manner as was employed at the first J-tube.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 5 Description of the Development Page 50
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