Storing & Installation of HVDC & HVAC Offshore Wind Power Cables: Driving Efficient Renewable Energy Integration

The integration of renewable energy sources, particularly offshore wind power, into existing transmission networks is crucial for meeting global energy demands sustainably. A key aspect of this process is the storage and installation of high-voltage direct current (HVDC) and high-voltage alternating current (HVAC) cables, which are essential for transporting power generated by offshore wind farms (OWFs) to onshore grids.

This post explores the intricacies of storing and installing these offshore wind power cables, their impact on grid performance, and the role of effective project management in ensuring successful implementation.

Storage of Offshore Wind Power Cables: Design and Considerations

The storage of offshore wind power cables, whether HVDC or HVAC, is a critical stage in the cable deployment process. Proper storage ensures that cables maintain their structural integrity and are ready for seamless installation when needed.

Offshore wind power cables are typically stored on large carousels or drums, which are specifically designed to handle the weight, length, and diameter of these robust cables. The cables are carefully coiled on these storage devices to prevent damage and to facilitate easy deployment during installation.

Key Design Considerations:

A1. Carousel or Drum Design: Load Capacity:

The storage device must be designed to support the full weight of the cable without causing deformation.

This requires an understanding of the cable’s physical properties, including its diameter, length, and material composition.

A2. Minimum Bend Radius:

Each cable has a minimum bend radius, which is the smallest radius it can be bent without sustaining damage. This radius is determined by the cable's construction and must be strictly adhered to when designing the carousel or drum.

Violating the minimum bend radius can result in insulation breakdown, conductor damage, and ultimately, cable failure.

A3. Cable Layering:

The cable must be layered on the drum or carousel in a manner that avoids excessive pressure on the lower layers, which could cause deformation over time.

Carousels & Drums Applications:

This storage approach is particularly suitable for in-field cables used in offshore wind parks (OWPs), shorter beach cables, and limited water crossings.

Carousels and drums are ideal for these applications because they allow for precise handling and transport, minimizing the risk of damage during the storage and deployment phases.

Installation Methods for Offshore Wind Power Cables

The installation of offshore wind power cables involves complex procedures that require meticulous planning and execution.

One of the most widely used methods is the S-lay method.

S-Lay Method:

B1. Coiling Direction:

For an S-lay installation, the cable must be coiled clockwise on the storage drum or carousel. This is crucial because the cable will unwind in a controlled manner, following the natural curvature of the seabed as it is laid.

This method reduces mechanical stress on the cable during installation, ensuring its long-term reliability.

B2. Deployment Process:

The cable is laid onto the seabed in an S-shape, which allows for a smooth transition from the vessel to the seabed.

This method is highly effective for laying cables over varying seabed topographies, as it accommodates shifts in depth and surface conditions without imposing excessive tension on the cable.

Impact on Power Quality, Grid Voltage, Frequency, and Waveform

The integration of offshore wind power into the grid, via HVDC or HVAC cables, has significant implications for power quality, grid voltage, frequency, and waveform stability.

Positive Impacts:

• Grid Stability: Properly managed integration, particularly with the support of Battery Energy Storage Systems (BESS), can enhance grid stability by providing a steady flow of renewable energy. This helps in balancing supply and demand, particularly during peak usage times.
• Improved Power Quality: Offshore wind power, when supplemented with power conditioning equipment, can lead to cleaner energy delivery, with reduced harmonic distortions and more stable voltage levels.

Negative Impacts:

• Voltage Fluctuations: If not properly managed, the intermittent nature of wind energy can cause voltage fluctuations, leading to potential power quality issues.
• Frequency Deviations: Large-scale integration without adequate grid management can result in frequency instability, which can negatively affect the overall power quality.
• Waveform Distortions: Variations in wind speed and generation output can lead to waveform distortions, introducing harmonics that can affect sensitive electronic equipment.

Impact on Grid Impedance and Management Strategies

Grid impedance, which refers to the resistance encountered by an alternating current (AC) as it travels through the power system, can be influenced by the integration of offshore wind power.

Changes in grid impedance can lead to resonance conditions, where certain frequencies are amplified, causing power quality issues. Additionally, impedance mismatches can lead to inefficiencies in power transmission, increasing losses.

To manage grid impedance effectively, it is essential to implement dynamic reactive power compensation systems, such as STATCOMs, which help maintain a stable grid voltage by adjusting reactive power levels in real-time. Additionally, impedance matching techniques should be used during the cable design and installation phases to minimize losses and ensure efficient power flow.

Successful offshore wind power projects require precise planning and coordination. Oracle Primavera P6 is a powerful tool that aids in detailed scheduling, resource allocation, and risk management, all of which are crucial for the effective deployment of HVDC and HVAC cables.

NEC4 contracts should be integrated into the project planning process by aligning the contract’s stipulations with the project’s schedule and risk management strategies in Oracle Primavera P6. This alignment ensures that contractual obligations regarding cost, time, and quality are met, reducing the risk of disputes and delays.

The Hornsea One Offshore Wind Farm, located off the coast of Yorkshire, UK, is a prime example of successful offshore wind power integration. As the world’s largest offshore wind farm, it faced numerous challenges in cable storage, installation, and grid integration. The project utilized advanced carousel systems for cable storage, ensuring that the cables remained in pristine condition during transport and deployment. The S-lay method was employed for installation, with careful attention paid to the coiling direction to ensure smooth and effective deployment. Hornsea One employed state-of-the-art reactive power management systems and impedance matching techniques to minimize the impact of its integration on the UK grid. This ensured that the farm’s significant power output was delivered with minimal disruption to grid stability.        

The latest innovations in offshore wind power cables focus on enhancing durability and flexibility to meet the demands of increasingly complex offshore wind projects. For example, dynamic cables capable of withstanding greater mechanical stresses and thermal loads are being developed for use in floating wind turbines.

These cables are designed to handle the unique challenges of floating platforms, which move with the ocean currents, requiring more robust and flexible cable solutions.

How do you think the latest innovations in offshore wind power cables will impact the future of global renewable energy integration???

This post reflects my personal knowledge and is for educational purposes only.

#RenewableEnergy #PowerCables #HVDCPowerCables #HVACPowerCables #PowerQuality #BESS #GridCodeComplianceStudies

Reference:

Horns Rev 3 Offshore Wind Farm.”?Power Technology, 13 July 2021, www.power-technology.com/projects/horns-rev-3-offshore-wind-farm/ . Accessed 14 Aug. 2024.

Mohsin Ali Koondhar, et al. “Critical Technical Issues with a Voltage-Source-Converter-Based High Voltage Direct Current Transmission System for the Onshore Integration of Offshore Wind Farms.” Sustainability, vol. 15, no. 18, 10 Sept. 2023, pp. 13526–13526