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Making offshore maintenance simpler!

Published:  07 February, 2014

Offshore wind technology has the potential to generate a significant percentage of the UK’s energy needs, it also presents a number of issues with regard to access and maintenance. For one wind farm in Norfolk, England, the helping hand of Alstom Grid and sub-contractor Schneider Electric, has made the process much simpler. ODEE reports.

Sheringham Shoal is an offshore wind farm, off the coast of North Norfolk, England, comprising of 88 wind turbines and generating approximately 1.1TWh of green energy per annum. In real terms, this equates to enough clean energy for almost 220,000 British homes annually or the energy needs of a town the size of Reading.

Located between 17 and 23 kilometres off the North Norfolk coast, Sheringham Shoal wind farm is reliant on two offshore substations and one onshore substation to connect the 88 turbines to the National Grid infrastructure. The two 132 KV export cables are 23km and 21km long respectively and connect the two offshore substations to the land. A further 22km of cable connect the site to the onshore substation in Salle, Norfolk.

Tom Ryan, MV maintenance manager at Schneider Electric commented: “The basic principles of wind energy generation and electrical output remain the same whether on or offshore but with a mass of water between you and the kit, there are certainly some obstacles that need to be overcome.

“Experience is therefore essential and is one of the key reasons why Alstom Grid selected Schneider Electric to work with them at Sheringham Shoal wind farm.”

Schneider Electric operates the main maintenance and servicing contract for both the onshore and offshore operations. Responsibilities include substation earthing, the 32kv distribution switchgear, the 240V and 110V AC supply distribution, 132KV, 33KV and 400V transformers and even the lighting on the platform.

Equally it’s also important to note that wind farms typically only generate energy 70-85% of the time. This intermittency affects the line rating of the grid connection and requires dynamic protection ratings as wind farms come on- and off-line. Issues can then be compounded further down the line with substations requiring automated voltage control and load balancing to avoid voltage peaks and overloads.

Continual monitoring of wind farm operations is key and this is something that is controlled by the Scira Offshore Energy team via a SCADA system at the operational centre on site. In the event of an onshore or offshore issue, the team can report directly to the Schneider Electric emergency call centre, available 24/7. If the problem cannot be solved remotely, the Schneider Electric team operate a 24/7 emergency response service.

The team is also commissioned for a four-year maintenance programme at three, six, nine and twelve month intervals across both the onshore and offshore substations.

Ryan continues: “Preventative and regular maintenance is essential for all electrical applications and offshore wind farms are no different. There is however a need for a certain amount of flexibility when it comes to offshore wind as the weather can be a real game-changer. It must be factored into all aspects of servicing contract from emergency responses to regular maintenance. “

While remote monitoring plays a crucial role in the successful operation of an offshore wind farm there is still a requirement for on-the-ground support. Needless to say, experience within this type of environment speaks volumes and where investments are at stake as well as the stability of the grid networks, it pays to employ the experts.

Alstom Grid was awarded the contract for the wind farm to design, construct, supply and install electrical distribution equipment for the site including the offshore substations and switchgear for the gathering and transfer of data to the National Grid. Schneider Electric has been appointed by Alstom Grid as the servicing contractor for the electrical distribution equipment both on and offshore.

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