The value of distributed optical fibre sensors in qualifying energy cables for offshore wind farms

The development of renewable energies and the transmission of data around the world are two of the major challenges of our century. More than 420 submarine cables crossed the world in 2021, representing more than 1.3 million kilometres of cables in the oceans. Among these submarine cables, the dynamic cables, which are used for exporting the power of all floating offshore wind turbines, are critical components that are subjected to challenging constraints.

 As part of the DYNAMO (DYNAmic cable MOnitoring) project, a series of mechanical tests (traction, compression and cyclical bending) were carried out on dynamic cables fitted with optical fibres. The objective of DYNAMO is to outline the best options for monitoring dynamic cables, on the basis of current state-of-the-art on sensors and monitoring practices, elaborated in connection with a thorough review of mechanical, electrical and thermal failure modes. The data were acquired using the DxS interrogator from FOSINA consisting of both DAS (Distributed Acoustic Sensing) and DSTS (Distributed Strain and Temperature Sensing) methods. In addition to the optical fibre, three thermocouple sensors (two in the cable and one to measure the ambient temperature) were used during the experiments to compare the results. The force exerted on the cable is also known. The combination of these data showed that armor wires breaks could be detected by the fibre.

These results are taken from the Time Machine Tool, developed by FOSINA, which enables the raw data to be reprocessed to obtain the most optimal acquisition parameters for detecting the desired phenomenon. In this way, data with a spatial sampling of just a few centimeters could be achieved.