Integrated Monitoring of Dynamic Cables

Mike Ellis, Business Development Manager - Offshore Renewables, Sonardyne
At FOW 2022, a representative of Sonardyne would like to describe how a FOW power cable monitoring solution will help operators understand inter-array cables dynamics by measuring cable (CPS) vibration, the cables' position, and water currents. Sonardyne has undertaken work to design a similar proposition with several fixed bottom offshore wind farm developers, which should be in service by the end of Q4, 2021. The company believes that a more advanced adaptive solution will help assess the expected greater cable dynamism associated with longer cables, floating structures, deeper water, and a harsher subsea environment.

The presentation will discuss how a combination of Sonardyne's SMART and Autonomous Monitoring Transponders (AMT) technologies can provide accurate measurements of high-frequency accelerations and rotations over 3-axes coupled with long-term position changes of the cable. While current profiles in the field will be measured using Sonardyne's newest 600 kHz ADCP technology. Cable vibration is measured utilizing the SMART sensors internal Micro Electronic Mechanical Systems Inertial Measurement Unit technology that logs X, Y and Z acceleration and rotational measurements. The position of the cable will be accurately measured using an array of four AMT's deployed on the seabed around the cable. The AMT's are pre-programmed to individually measure the range to both their AMT neighbours and the SMART sensors located at several points along the cable. At the same time, advanced ADCP lander technology provides an all-in-one unit for measuring currents throughout the water column. All units can sustain extended periods (several months) installed subsea and have the built-in capability to send data packets upon request to a surface transceiver using Sonardynes 6G wideband technology.

FOW cable behavioural patterns will differ because of changes to locational characteristics and variations in catenary design. This brings several new challenges to offshore wind cable arrays, exposing them to several potentially damaging factors such as hydrodynamic drag forces, TPD migration and cable compression, platform induced motion, and vortex-induced vibrations. Therefore, Sonardyne believes that this type of monitoring system will have a meaningful effect on building dynamic cable knowledge within the industry and subsequently limiting the chances of catastrophic cable failure.