Submarine power cables stand as the key “nuclei” of the worldwide power system. They silently transport vast amounts of power in the unseen depths of the ocean to make sure that we have a reliable and secure supply of electricity. Fulfilling the role of an artery in a global economy, submarine cables are now more important than ever as countries are relying on renewable energy sources more and more. The booming offshore wind farm market also explains the growing submarine cable market. This blog aims to address all the crucial questions regarding submarine cables and its utilization over the ocean. Explore this now!
Submarine Power Cable Market Development Status
Global market size growth: the global pursuit of clean energy and the proliferation of offshore wind power projects is directly driving the demand for submarine power cable market. With the increase in government investment in renewable energy, especially the construction of offshore wind farms in Europe, Asia and North America, the importance of submarine cables as a key infrastructure is becoming increasingly prominent. Meanwhile, cross-sea power interconnection projects, which aim at connecting power grids of different countries through submarine cables for optimal allocation and sharing of energy, has become another important aspect of growing market demand. The global submarine power cable market size has reached a significant level by 2024 and is expected to continue growing in the coming years.
Technological advancement and innovation: with the advancement of technology, the design, materials and manufacturing technologies of submarine cables have been optimized to improve the transmission efficiency, durability and reliability of the cables. It is especially true for high-voltage direct current (HVDC) cables. Technological advances have made it possible to transmit power over long distances.
What Are the Key Components of Submarine Power Cables?
Submarine cables are located in an extremely complex and harsh environment. Long-term immersion in a high concentration of seawater, cable cables are extremely susceptible to seawater corrosion. It consists of the following key components:
Conductor: Usually made of copper or aluminum, the conductor is responsible for the transmission of current. In submarine cables, the conductor needs to be designed with high conductivity and corrosion resistance in mind to provide efficient and reliable power transmission.
Insulation: Wrapped around the outside of the conductor, it is used to isolate the conductor from the external environment and prevent current leakage. Materials used include polyethylene (PE), polyvinyl chloride (PVC), cross-linked polyethylene (XLPE), etc., which are able to withstand submarine high-voltage environments while reducing power loss.
Shielding layer: For high-voltage cables, especially AC cables, a conductor shield and an insulation shield are usually provided to even out the electric field distribution and reduce electromagnetic interference.
Armor layer: In order to resist the physical pressures of the seabed, biological nibbling, and potential man-made damage, submarine cables are armored with one or more layers of steel wire or steel tape to provide mechanical protection.
Sheath: the outermost protective layer is usually made of polyvinyl chloride, polyurethane or special synthetic materials. It is useful for waterproofing and corrosion protection in order to adapt to the extreme environment of the seabed and to protect the internal structure from seawater and external physical damage.
How are submarine cables waterproofed?
A cable’s sheath, its insulation, or its joints can get severed as a result of some energy impact or mechanical forces, and seepage of either moisture or water can take place through the radial and longitudinal interfaces/sheath of the cable. It is for this reason that appropriate measures for waterproofing a high voltage submarine cable have to be included in the cable. Two primary methods for waterproofing are employed: transverse or radial waterproofing and longitudinal waterproofing:
- Radial measures are mainly in the cable insulation layer outside the winding semiconductor resistance water expansion tape. The tape expands when exposed to water and enhances the sealing.
- Longitudinal waterproofing mainly in the wire between and cable core shielding area to add water-blocking powder and other substances, these substances absorb water can quickly expand to form a gel to prevent the spread of water along the inside of the cable.
What are submarine power cables used for?
Submarine Power Cables for Distribution and Transmission
Submarine power cables are usually available in voltage levels ranging from 35kv to 220kv, and even higher voltage cables of 500kv are also used in some high-end projects. Such cables play a central role in the distribution and transmission of electricity, especially when it comes to international power trading and connecting remote renewable energy sites to ensure the efficient distribution and utilization of energy.
Submarine Power Cables for Offshore Renewable Energy Integration
Submarine power cables bridge the gap between offshore energy facilities, such as offshore wind farms, tidal energy and ocean thermal power, and the land-based power grid. But do you understand how offshore wind power is delivered? Electricity generated by offshore wind is boosted by offshore booster stations to increase the voltage before it is transmitted back to land through the submarine power transmission system. As offshore wind farms are often located tens of kilometers offshore, submarine cables are the only way to transmit power. These cables allow for the capture and transmission of large amounts of clean energy, supporting the green energy transition.
Submarine Power Cables for Long-Distance Power Transmission
Submarine cables provide a way to power remote coastal communities or islands that lack local power generation capacity. A typical submarine cable has a service life of about 25 years. Local sources of energy, such as diesel generators, which are less efficient or more polluting, are often replaced.
Submarine Cabling Installation & Repair
Due to the complexity and uncertainty of the submarine environment, submarine power cables must overcome a variety of factors such as water depth, currents and submarine topography during the laying process, so the requirements for laying and maintenance are very high.
When laying submarine power cables, detailed exploration of the seabed topography and environment through underwater detectors is first required to keep the safety of the laying path. Specific submarine conditions should be taken into account when designing the cable structure, including the strength of the armor layer and the choice of insulation material. Use specialized laying vessels to coil and load the cables on board, and equip underwater robots (ROVs) to assist subsea operations.
The vessel needs to move slowly and release the cable with precise control. In deep sea areas, the cable can be laid directly, while offshore or in areas with special requirements, a trenching machine is used to bury the cable on the seabed. To assure the safety of the cable, a plow-type trenching machine is used to create a trench in the seabed, which is then placed and backfilled to protect the cable from physical damage.
Repair work also requires special attention in the event of a cable failure:
- The location of the damage to the cable is determined by optical signal testing or sonar systems, which often require accurate seabed maps and advanced positioning techniques.
- Then, a specialized repair vessel and diving equipment are dispatched to the point of failure with specialized tools and spare parts.
- For deep-sea repairs, sealed repair bins can be used to drain the internal seawater and create a dry workspace to prevent seawater from entering the interior of the cable.
- When carrying out deep sea repairs, it is important to guarantee that the pressure in the repair environment is controlled to prevent internal pressure imbalance.
- Once the repair is complete, rigorous testing is required to safeguard the integrity of the signal or power transmission, and finally the cable is reburied or secured to the seabed.
What is the cost of laying submarine power cables underwater?
At a total cost of £1.7 billion, the Viking Link submarine power cable is currently the longest underwater power cable project of its kind in the world. It is the first high-voltage DC submarine power line that connects United Kingdom and Denmark directly. Depending on the voltage to be carried, the distance to be traveled, and the type of power, the cable will vary in thickness and construction. Generally speaking, cables for AC power will be thicker, while cables for DC power will be relatively simple. Whether it is the internal conductor, the external insulation, or the entire assembly process, the production process of cables is actually very complex, which leads to an increase in the price of cables. Submarine power cables, for example, cost about US$2.5 million per kilometer. Deep sea laying is usually more expensive than shallow sea because deep sea operations require more specialized equipment and technical support.
Key Players in the Industry
Major Manufacturers
Several leading manufacturers have emerged as key players in the submarine power cable industry. These companies have made a significant impact on the market with their vast experience and advanced technology.
Prysmian Group: One of the largest manufacturers, the Prysmian Group specializes in high-voltage dynamic power cables for submarine applications. They have specialized knowledge in cable design and installation technology.
Nexans: Nexans is known for its advanced submarine cable solutions, with a focus on sustainability and efficiency. Their involvement in numerous offshore renewable energy projects has contributed to the growth of the industry.
ZW Cable: ZW Cable manufactures a range of high quality power and communication cables for subsea applications. The cables meet the reliability and efficiency needs of the power market.
NKT: NKT emphasizes innovation and is committed to developing state-of-the-art submarine cable technology. The result is durable, efficient cables that meet the demands of modern energy transmission.
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