Export cable installation for Thanet wind energy project – February 2010

Using its revolutionary SpiderPlow system, Spencer ECA carried out a highly successful installation of heavy-duty export cables for the largest offshore wind energy project in the world. The work took place in Pegwell Bay near Thanet, Kent, in an area designated as an SSSI (Site of Special Scientific Interest) and, what would traditionally take an army of men and a fleet of excavators working for a number of days, was carried out by a small team of operatives and Spencer’s SpiderPlow in a matter of hours.

Main contractors Sub Ocean approached Spencer to see if the SpiderPlow could overcome a series of issues that surrounded this major project. These included the handling and installation of 250 tonnes of 132kv cable - with a 225mm external diameter - had to be located at a depth of up to two meters and would involve the crossing of a chalk-based (limestone) beach and a salt-marsh designated as a SSSI. Added to this was the race against the tide that would only allow a limited window of opportunity for the cable to be laid.

Having assessed the work that was required and, after carrying out an on-site test some six months beforehand, Spencer arranged for specific modifications to be carried out to its SpiderPlow in order to ensure the job could be performed efficiently and effectively. Work started in February and, once the installation process began, the Spencer team was able to install 1.1 kilometers of cable in less than four hours!

The cable was fed from a barge anchored on the shoreline and supported along its length as the SpiderPlow was pulled along by its independent power winch. The cable was then guided through the blade of the plough and positioned at a specified depth in a consistently formed narrow aperture, which was subsequently closed as the SpiderPlow moved forward.

Because of this method of operation, the SpiderPlow caused far less disturbance to the ground in comparison to that of conventional open-trench styles of cable laying - another extremely important consideration with the construction of this landmark project.

With the installation process carried out so smoothly the main contractors for this massive project were delighted:
“Getting cables across the beach and the salt marsh areas initially appeared to be a potential problem for us”, said Beach Master for Sub Ocean Graham Park. “However, once Spencer became involved and showed us what its SpiderPlow could do, we realised there was a way around this issue. In fact, the actual job went even better than expected and we are absolutely delighted, not just with the efficiency of the installation itself, but the speed in which the work was carried out. The SpiderPlow provided an ideal solution for us.”

The contractors also noted that following fibre-optic tests carried out to inspect any possible damage to the 132KV cable after installation, the results demonstrated better cable integrity than would normally be detected using traditional cable laying techniques. So good news all round for Spencer!