The Problem
A cable protection system that had moved
The cable protection system (CPS) at one of the wind farm’s turbines, WTG A11, needed a close look. A CPS carries the cable from the monopile bellmouth to the point where it is buried, and it only does its job while it stays where it was installed.
Hydrodynamic forces, sediment movement and installation issues can all leave a CPS exposed, misaligned or under tension. At A11 the concerns were specific: sections of cable looked exposed or under-protected, the rock bags placed to secure the CPS appeared to have gaps, and the CPS seemed to leave the bellmouth at the wrong angle, which suggests uneven tension on the cable. Each of those is a deviation from the design, and each needed confirming and measuring before the operator could plan a repair.
The Inspection
Bellmouth to burial point, measured end to end
The full CPS run on video
A high-definition video survey of the whole system, from the monopile bellmouth to the burial point, recording the exposed cable, the rock bag placement and the exit angle at the bellmouth.
Distances, not impressions
The distance between each anomaly, the burial point and the monopile was measured and logged, including the misalignment on the A11 to A12 connection, so the client had positions and lengths to plan against.
What is happening around it
The seabed around the CPS was checked for scour and sediment movement, the factors most likely to be behind the movement, and the rock bags were assessed for how well they were still protecting the cable.
Our Solution
HD video and sonar from a compact ROV
The team deployed the Ocean Modules V8 M500 ROV with high-definition video and imaging sonar. The sonar gives the position and shape of the CPS, the rock bags and the seabed even where visibility is poor, and the video records the detail of each anomaly.
Working from a compact system meant the inspection could be mobilised quickly and run from a small vessel, with the ROV holding position close to the monopile while the measurements were taken.
The Scope
What was inspected at WTG A11
Bellmouth exit
The angle at which the CPS leaves the monopile bellmouth, checked against the design.
CPS run
The full length from bellmouth to burial point, with every section of exposed or under-protected cable recorded.
Rock bags
Placement and effectiveness of the protective rock bags, including where cable ran out beyond them.
Measurements
Distances between anomalies, burial points and the monopile, logged for remediation planning.
Seabed and scour
Sediment movement and scour around the CPS and the base of the monopile.
Anomaly record
Each anomaly recorded with video, sonar imagery and measurements.
From the ROV
The Result
Six anomalies, measured and ready to fix
The inspection recorded six anomalies at WTG A11: exposed cable, misaligned CPS exits and rock bags that were no longer doing their job. The key figures were about 7 metres of exposed cable and 2 metres of cable running out beyond the rock bags, with the misalignment confirmed on the A11 to A12 connection.
Because every anomaly came with a position, a length and supporting video and sonar, the operator could plan targeted remediation rather than a general survey of the whole array.
Delivered to the client
- High-definition video of the full CPS run, bellmouth to burial point
- Imaging sonar of the CPS, rock bags and surrounding seabed
- Six anomalies logged with positions and measurements
- Exposed cable lengths and rock bag gaps quantified
- Seabed and scour assessment around the CPS
- A report built for remediation planning
A CPS that has moved is a repair waiting to be scheduled. Measuring it properly the first time is what lets the operator fix the right thing, once.
Why Atlantas Marine
What made the difference
Compact system
The V8 M500 mobilised quickly and worked close in to the monopile where the detail was, without a large vessel or spread.
Measured, not estimated
Exposed cable lengths and rock bag gaps were measured and positioned, so the remediation scope was clear from day one.
Sonar and video together
Sonar gave the shape and position of the CPS in poor visibility; video gave the detail of each anomaly.
Operational experience
The team inspects CPS runs regularly and knows what a misaligned bellmouth exit and a displaced rock bag look like before the data is analysed.
One turbine. Six anomalies. A clear repair scope. Save time. No dive. No risk.
Need a cable protection system inspected?
Talk to a team that surveys CPS runs from bellmouth to burial point and hands over measurements the remediation contractor can work from.
How can we help?
Tell us about your inspection campaign
Send the ROV operations team a few details about the asset, the location and the timing, and we will come back to you with how we would approach it.