General – Cable Repair
Netherlands-headquartered subsea solutions provider N-Sea has completed a nearshore export cable repair in the Irish Sea after a fault in one of its client’s four subsea cables reduced transmission capacity between offshore and onshore substations.
According to N-Sea, the company was awarded a contract to provide a turnkey, fast-response repair solution in a nearshore location with water depths of 0 to 2 meters at the lowest astronomical tide (LAT).
N-Sea’s fault-finding and engineering efforts led to the installation of a spare cable section between the onshore transition joint bay (TJB) and an offshore location at KP1.0. Acting as the principal contractor and designer under the CDM, N-Sea handled the engineering, analysis, and preparatory work required for both onshore and offshore stages before initiating the repair.
The project involved pre-survey techniques, including a multi-beam echosounder hydrographic system (MBES), side-scan sonar (SSS), sub-bottom profiler (SBP), magnetometer, light detection and ranging (LIDAR), and onshore clean propulsion technologies (CPT), to secure a viable cable route. N-Sea then loaded and transported a spare cable from its storage facility in the Netherlands to the UK for mobilization.
For the offshore phase, N-Sea said it had deployed two jack-up barges equipped with cable-lay and jointing equipment, cranes, accommodation modules, and supporting tugs. An additional multi-cat vessel with a mooring spread was mobilized to carry out cable de-burial, fault finding, subsea cutting, and removal of the damaged cable, with the new cable buried after the repair.
Onshore operations included setting up a full site to facilitate cable landing, handling two cable crossings, and removing the old cable before burying the replacement and applying thermal grouting of the HDD. The TJB was also modified to house a new onshore joint.
Both onshore and offshore joints were installed to finalize the repair, with the TJB fully reinstated, allowing the client to re-energize the cable and resume green energy transportation.
