Dynamic Medium Voltage Power Cables

Abstract Designing dynamic subsea power cables for various renewable energy applications presents a range of challenges. The four most technologically demanding considerations are: maximum submersible depth, maximum cable capacity/voltage, maximum length before switching from AC to DC transmission and stress limits for dynamic cables. This paper discusses the cable designs that exist for subsea power links and their benefits and limitations. Particular focus is placed on self-supporting cables, which tolerate gentle flexing through special flexible conductors and screening systems, and proven dielectric insulation systems. The latter enable subsea power cables to operate within water without rigid metallic barriers, such as lead, which would ultimately fail in such a dynamic environment. To qualify this paper's findings, various data has been collected, cables developed and computer modeling completed in order to validate the conclusions. There is a significant application under development, Ocean Thermal Energy Conversion (OTEC) plants, which will require dynamic submarine power cables. It is widely accepted that OTEC is economically viable for plant sizes of more than 100 MWe-net power generation and a plant of this size will require offshore platforms located in water depths of at least 1000 m. At these water depths, a fixed position mooring is not possible so floating platforms and deepwater, dynamic subsea power cables are needed to supply OTEC-generated electricity from platform to shore. A dynamic power cable of this size and at this water depth has not yet been developed but is required to enable OTEC to become economically viable. Electrical stress limits for dynamic cables will also be discussed, detailing several options, work in progress and their limitations. European wet systems (which are immersed in water), historical data, type tests and reliability type testing will be also referenced. This paper will significantly advance research and development efforts in dynamic subsea power cable technology that will, in turn, help advance many offshore energy technologies.