Effect of Mechanical Strain on Water Treeing Mechanism of Dynamic Cable for Floating Offshore Wind Applications

海上风能是英国向可持续未来电网过渡的雄心壮志的核心。漂浮式风力涡轮机发电量的增长越来越远离海岸，并利用漂浮式风力涡轮机支撑结构。这增加了缆索承受的机械应变，潮汐和波动引起的在役振荡运动进一步增强了这一点。目前尚不清楚电缆结构中的低频物理振荡是否会带来固有的可靠性风险，因为传统的陆地电缆通常安装在相对良好的环境中。通常，电缆资产占海上风电场总投资成本的5%-10%。然而，电缆故障是海上停电的主要原因，约占该行业保险索赔的80%。本项目将研究变化的机械应变对动态拉索中水树机理的影响，并在典型试验条件下模拟这种设计的老化。自行研制了一台机械应变变化的水树试验台，并在不同的参数下进行了试验。将首先进行一系列小规模实验，以研究稳态和低频机械振动对水树生长特性变化的影响。这是为了确定机械应变的循环是否加速了水树的起始和生长过程。从而潜在地增加了动态电缆的故障风险。

Offshore wind energy is central to UK's ambition of transitioning to a sustainable future electricity grid. The growth in power generation from floating wind turbines are increasingly further away from shore and utilising the floating wind turbine support structures. This increases the mechanical strain the cable is subjected to, which is enhanced further by in-service oscillatory movement caused by tidal and wave motion. It is unknown whether low frequency physical oscillations in cable structures pose an intrinsic reliability risk since conventional land cables are typically installed in relatively benign environments. Typically, cable assets contribute to 5-10% of the total investment costs for an offshore wind farm. However, cable failures cause the majority of the offshore power outages and account for approximately 80% of insurance claims in this industry. This project will investigate the effect of varying mechanical strain on the water treeing mechanism in dynamic cable and model the ageing of such design under representative test conditions. A bespoke water treeing test rig with varying mechanical strain will be developed and to be tested under different parameters. A series of small-scale experiments will be initially carried out to investigate the impact of steady state and low frequency mechanical oscillations on the characteristic change in water tree growth. This is to determine whether cycling of mechanical strain accelerates water tree initiation and growth processes. Thereby, potentially increasing the risk of failure for dynamic cables.