| dc.description.abstract | The offshore wind industry is experiencing significant growth, with wind farms expanding in size, capacity, and moving to more challenging locations. However, cable faults remain a major concern, particularly during the installation of inter-array and export cables. This thesis aims to research and analyse the installation steps of inter-array cables at the Utsira Nord offshore wind farm. It further seeks to enhance the installation process by identifying functional sea states through a combination of previous work and new data.
The research focuses on answering key questions related to the installation of inter-array cables. This includes identifying the main steps, defining critical phases, and analysing the typical loads that impact cable installation to determine the parameters affecting the process. Additionally, the thesis seeks to determine the optimal environmental conditions for cable installation. The methodology employed in this thesis includes literature studies, experience from employees at DeepOcean regarding offshore operations, and the use of Orcaflex and Excel.
The analysis, primarily conducted using Orcaflex, concentrates on the installation of 1st and 2nd end dynamic section. The floating windmill is treated as a fixed structure in the Orcaflex model, neglecting its movement due to the ongoing development of the foundation concept and limited comprehensive information on weather and environmental factors. The study primarily focuses on tension and curvature acting on the cable during installation, disregarding boat and floating structure considerations that are not directly relevant to the research objectives.
From the knowledge gained in the literature review, an analysis was carried out to investigate crucial parameters in the cable laying process and a conclusion for when it is optimal to do inter-array cable installation operations at Utsira Nord was given. The focus was on tension loads, minimum bending radius, and potential clashes with the Moonpool. This was conducted with both Gumbel and Rayleigh analysis with irregular vessel motions. The result of the analysis illustrated the extent of impact the various environmental wave conditions had on the system.
Throughout the study, certain wave conditions were found to be more favourable than others. Wave directions ranging from 90-135° and 225-270°, simulated with a current velocity of 0.3 m/s, offered the most optimal conditions for cable installation. In contrast, the analysis showed that sea states with wave directions of 0° and 180°, as well as current at 1.0 m/s, presented a higher risk of cable damage.
To enhance the findings of this master's thesis, further analysis of different current velocities is recommended to identify operable sea states under higher currents. Additionally, analysing the system with a moving floating wind turbine, given that sufficient data is available. | |
