In the rapidly expanding world of offshore wind energy, the significance of cable protection systems (CPS) cannot be overstated. Export and inter-array cables are pivotal components of wind farm infrastructure, playing a crucial role in the transmission of power. The implementation of robust CPS is crucial to ensure the sustained functionality and durability of subsea power cables in the face of various environmental challenges. This article highlights the role of CPS in safeguarding subsea power cables from dynamic forces and external factors that could undermine their longevity.
Cable protection systems (CPS) help protect cables against impact, abrasion, fatigue, and damaging movement such as overbending at vulnerable locations. This is particularly important for floating wind turbines which use dynamic cables to enable movement. CPS are needed to reduce costs involved in maintaining, repairing, or replacing cables.
They also play a crucial role in safeguarding vulnerable sections of subsea power cables from the effects of wave and ocean current action, including scour. These critical locations typically include the cable entry and exit points on the floating substructure and offshore substation, the touch-down point on the seabed, and areas where the cable is exposed and cannot be buried.
There are three primary types of cable protection:
- Vertebrae bend restrictors
- Dynamic bend stiffeners
- Cable sleeves / abrasion protection
Each serves to restrict or dampen impacts on the cable during installation or operational life. Bend stiffeners and bend restrictors work to reduce or limit the bending moments (bending forces) applied to cables, preventing overbending. Protective cable sleeves offer both abrasion protection and touch-down protection, ensuring the safety of the cable where it lies exposed on the seabed, where it enters or exits the seabed, or where it intersects with other cable routes.
The need and challenges for cable protection in wind farm operations
The cable protection system is a critical defence mechanism for subsea power cables, protecting against issues such as excessive bending, impacts from falling objects, and wear resulting from prolonged stretching from seabed to monopile or J-tube. Recent reports highlight a significant cause of CPS failures related to the displacement of these protective systems over rock layers designed to prevent seabed erosion. This displacement has led to substantial abrasion, particularly near wind turbine foundations, raising concerns about potential cable damage and the need for replacements. By safeguarding cables from damage and wear caused by these dynamic forces, CPS contributes to the extension of cable lifespan, ultimately reducing operational costs.
Developers grapple with a range of challenges, including corrosion, suboptimal material selection, intricate calculations, unfulfilled performance assurances, and the absence of standardized industry guidelines. Contributing factors encompass inadequate oversight by developers, alterations in project approaches, and lapses on the part of CPS suppliers.
In response to these challenges, developers are refining their procurement processes and intensifying engineering oversight concerning CPS installations. Inspection frequencies have been augmented in certain cases. Publicly disclosed statements from a developer indicate a strategic shift in CPS stabilization design, acknowledging its pivotal role in failures and instituting a comprehensive reversal for all forthcoming projects.
Confidentiality and disclosure dilemmas in wind farm repairs
While initial estimates projected substantial costs for CPS repairs, further scrutiny has unveiled opportunities for cost reduction through improved repair designs and installation practices.
The norm within the wind farm industry is to keep issues discreet, disclosing only what is legally obligatory. The confidentiality surrounding such matters is compounded by contractual clauses that prohibit contractors and suppliers involved in repairs from divulging information about their involvement, restricting the disclosure of successful implementations or clientele.
Optimizing wind farm cable specifications and costs
Employing CPS presents a significant advantage in optimizing subsea power cable specifications. By eliminating the necessity for additional cable armouring, CPS not only streamlines the design but also enables the production of cost-effective cables that meet the stringent requirements of a 20-year lifespan, or longer. This is particularly crucial for offshore wind farm developers who aim to strike a delicate balance between performance, durability, and cost-efficiency in their projects.
Numerous case studies have demonstrated that the integration of CPS results in cables with enhanced longevity and reduced susceptibility to wear and tear, thus contributing to a more robust and cost-effective wind farm infrastructure.
Monopile interface and innovative cable protection in wind farms
At the core of CPS design is the strategic concept of the monopile interface, acting as a pivotal point to mitigate cable vulnerability. The innovative adoption of a ‘latching’ CPS model, penetrating the monopile’s outer wall through a bespoke angled aperture, represents a paradigm shift in traditional monopile designs. This forward-looking approach not only streamlines construction processes but also diminishes the need for post-pile driving interventions involving divers. Rapidly emerging as an industry norm, this approach offers windfarm developers a means to optimize construction expenditure.
Field trials and real-world applications of the ‘latching’ CPS model have demonstrated a reduction in construction time and costs, showcasing its efficiency and feasibility in diverse offshore environments.
Protect cables for smoother wind farm operation
CPS plays a pivotal role in addressing a spectrum of operational challenges, primarily safeguarding cables against fatigue and overbending, two critical phenomena that could otherwise compromise cable functionality. Moreover, CPS acts as a shield, ensuring uninterrupted service by protecting cables until they reach burial areas, even in dynamic seabed conditions with the potential for localized scouring.
Conclusion
Summing up, cable protection systems are indispensable for optimizing wind farm operations. By safeguarding subsea power cables from dynamic forces, overbending, and external threats, CPS significantly enhances cable longevity, reduces operational costs, and augments the overall viability of wind farm projects. To maximize the advantages of cable protection systems, wind farm developers are encouraged to:
- Continuously explore and integrate innovative monopile interface designs, leveraging ‘latching’ CPS systems for enhanced efficiency.
- Collaborate closely with CPS manufacturers to tailor solutions that align precisely with specific wind farm topographies and seabed conditions.
- Invest in ongoing research to identify emerging threats and challenges that CPS can address, thereby enhancing its adaptability and overall effectiveness.
As offshore wind energy continues to grow globally, the role of cable protection systems will undoubtedly become even more pronounced. Their evolution and innovation will be pivotal in ensuring the sustained growth and profitability of the industry, solidifying CPS’s status as a linchpin technology within the wind farm ecosystem.
By Shaik Ejamani
Senior Consultant,
Asset Management, Power Systems APAC,
Energy Systems.
DNV Singapore Pte. Ltd.
Nguồn: https://renewablewatch.in/2024/03/08/enhancing-wind-farm-cable-protection-systems-for-long-life-and-efficiency/