Fiber-Optic Sensors (FOS) for Smart High Voltage Composite Cables—Numerical Simulation of Multi-Parameter Bending Effects Generated by Irregular Seabed Topography

Abstract

Offshore renewable energy requires reliable high-voltage electric power cables to transport electricity to onshore stations. These power cables are critical infrastructures that are shipped to deep seas through shipping and handling operations and, once mounted, must then evolve in extreme conditions (sea, salt, wind, water-pressure, seabed topography, etc.). All of these operations and working conditions can lead to yielding of copper conductors, often resulting in electric shutdown. Indeed, copper is an excellent electric conductor (conductivity), but its mechanical properties are very poor. If any negligence occurs during the shipping and/or handling operations, copper can undergo plasticity, with effects on both mechanical and electric properties. It is therefore of prime importance to establish a reliable structural health-monitoring (SHM) technique that will enable the continuous recording of copper strain and temperature along a cable, and this has been proven using fiber-optic (FOS) sensors, when the phase is under tensile loading. In this prospective article, the scope is to maintain previous simulations and thus show that by the judicious placement of FOS, one can monitor strain and temperature within cables that are submitted to a bending. This article does not aim to deal directly with the case of a cable that undergoes bending on sloppy areas in seabeds. The idea behind the work is to suggest a concept for the use of embedded fiber-optic sensors and to think about all of what remains to be done as research in order to further suggest this technology to cable manufacturers.

New Concept of Dual-Sinusoid Distributed Fiber-Optic Sensors Antiphase-Placed for the SHM of Smart Composite Structures for Offshore

“…However, embedded FOSs are "foreign" materials whose diameters (e.g., 125 µm) are much larger than that of carbon fibers (e.g., 5~10 µm) [19], thereby inevitably resulting in perturbed strain states around them. They could act as internal flaws that might initiate damage (e.g., debonding and delamination) and cause premature failures [1][2][3][4][5].…”

“…that might initiate damage (e.g., debonding and delamination) and cause premature failures [1][2][3][4][5].…”

“…In recent years, many research works have been devoted to the placement of sensors inside composites for structural health monitoring (SHM) of the offshore wind sector (e.g., offshore wind turbine blades and high-voltage power cables) [1][2][3][4][5][6] because it is fast-growing and more promising than its onshore counterpart in helping wind energy stay on course for the 1.5 • C and net zero pathway set out by International Renewable Energy Agency [5,[7][8][9]. Current offshore wind turbine blades manufactured by companies General Electric, Vestas, MingYang, and Siemens exceed 100 m to realize exceptional energy-generation performances and reduce the leveraged cost of energy [10][11][12].…”

“…Areas of weakness in a CFRP blade have been identified as the root sections and trailing edge bonds, and corresponding reinforcement strategies have been suggested to ensure reliability [1][2][3][4][5]13,14]. Meanwhile, a continuous, automatic, and in situ SHM system is highly desirable.…”

“…To er maximum information concerning health conditions of structures under various conditions, ideally, nerves/sensors provide full coverage of not only structural surbut also structural volume. This requires sensors be bonded/embedded into strucs at representative locations, in addition to being installed on surfaces, which can also nce protection of sensors from external harsh environments [1][2][3][4][5]15,[18][19][20][21]. Fiber-optic sensors (FOSs), as shown in Figure 1, have proven strain-measuring calities and suitability for embedment into CFRP composites [15,[22][23][24][25][26].…”