Cable span monitoring
A developer had recently installed a wind farm in the East Irish Sea and found that some cables were spanning around the wind turbine towers. Fatigue assessment of the cable components had been carried out based on predicted motions.
Whilst the fatigue analysis predicted that the armour windings had sufficient fatigue life, our client wished to verify this assessment by validating the predicted cable motions.
We were asked to develop a system to monitor the behaviour of the cables. Motion was the critical loading condition for fatigue and therefore the equipment had to be tailored to clearly define both horizontal and vertical motion.
We addressed our client’s requirements by:
- Analysing options for monitoring the cable motions
- Carrying out a detailed design of the preferred system
- Managing procurement, fabrication, assembly and testing of the equipment
- Installing the equipment and downloading the data created
- Analysing, interpreting and reporting on data findings
To monitor the motion of the cables, our team designed and installed an accelerometer-based monitoring system, the cable-linked back to a power station and data logging unit mounted on the monopile access platform. Data was transmitted via fibre optics to shore where it could then be securely sent over the internet to any computer.
An Acoustic Wave and Current (AWAC) monitoring system was also installed locally to monitor metocean conditions.
The new innovative technology designed by our specialist engineers, allowed our client to review the actual movement of the cables in real-time from remote office locations. The data collected enabled the predicted fatigue life to be validated against the observed conditions, giving the client assurance and confidence the cables would not fail due to fatigue before predicted.
The development of a real-time monitoring system avoids the need to wait for suitable sea conditions to retrieve the data and reduces the risk of the data retrieval operation.