Page 13: of Marine Technology Magazine (November 2011)

www.seadiscovery.com Marine Technology Reporter 13connections in the cable remain intact and prevent them from twist- ing during the 360° movement. Scotrenewables and MacArtney worked together to custom design the 6.6kV umbilical that can carry the required 250kW. For this prototype, the 3500m cable also has two signalSTPs (screened twisted pairs) that transfer data to and from the turbine to shore. Protecting the cable extends its functional life and preventing bending and twisting of the cable atthe termination point is vital for pre- venting cable fatigue and failure. At the point of contact between cable and turbine, a steel stress termination on the high voltage wet mateable connector pair take the strain off thecable. The termination point where the cable exits the stress termination is also vulnerable as vibrations in thecable can weaken it over time. A bend stiffener was designed into the systemto dampen the vibrations to help pro- tect the cable from fatigue and extend its working life. Close CooperationMark Hamilton, CTO at Scotrenewables said, ?MacArtney was the ideal subsea engineering partner for us in this our first venture into large-scale offshore deployment. Their vast experience in component supply, and support during the design and installation phases were instrumental in delivering our project on time and on budget.?The system will be tested in thewaters off Orkney for two years, exporting power to the grid. Testing the turbine in real sea conditions will provide the company with invaluable advice and experience before produc- ing the full scale 1-2MW version. MTR#9 (1-17):MTR Layouts 11/29/2011 10:20 AM Page 13