Gwynt Y Môr - Cable Repair

Gwynt y Môr Offshore Wind Farm Limited has developed an offshore wind farm of up to 750 MW to be known as the Gwynt y Môr Offshore Wind Farm.

Gwynt y Môr Offshore Wind Farm site is located:

  • 13km off the North Wales coast at the nearest point to shore
  • 16km from Llandudno
  • 18km from the Wirral

The Gwynt y Môr Offshore Wind Farm comprises an array of WTGs, supported on foundations, and connected to offshore substation platforms by subsea array cables. The offshore substation platforms are connected via a 20km offshore export cable route to landfall and a 12km onshore export cable route to an onshore substation at St Asaph in North Wales where the wind farm is connected to the National Grid at 400kV. A fault had occurred on one of the export cables some 2.5 kilometers from the offshore substation. Water depths in the area were 16m LAT with a large tidal range and high currents.

Facts and figures

Year of construction
Number of cables
1 x replacement length (600m) with 2 x cable joints
Type of cable
132KV Export Cable
CLV Ndurance
Project categories

Scope of work

  • Mobilisation of cable repair vessel and auxiliary equipment
  • Determine cable position along cable route
  • Deburial of cable along cable route
  • Cut, test and seal operations
  • Removal of sea end cable till jointing location
  • Cut cable and joint to new cable section
  • Lay down joint No.1 on sea bottom and lay new section of cable
  • Recover shore end and joint both cable ends
  • Lay down joint No.2 and omega on sea bottom
  • Post lay ROV survey

After establishing a strong working relationship with the developer RWE during previously executed remedial works, VBMS were asked to facilitate a repair to one of the export cables connecting the Gwynt Y Mor offshore wind farm. The export cable had suffered a fault some 2.5 kilometers from the offshore substation. Fault pin pointing activities had already been executed by cable manufacturer NKT who were later contracted directly by VBMS to complete the cable and fiber jointing. By initiating this, VBMS were able to offer their client a turnkey solution for the repair scope. The DP2 cable laying vessel “Ndurance” which is operated by VBMS was mobilized to include: A full work class ROV spread, subsea tooling for cable cutting and a mass flow excavation spread for de-burial in the repair area. This accompanied by the advanced cable laying system and extremely capable DP system installed on the vessel, made for a very effective repair platform. The Vessel arrived on site during the afternoon of 15th June 2014 and began to load the spare cable at the RWE facility within Cammell Laird docks, Birkenhead (UK). Once the spare cable was successfully loaded, the vessel left for the work site to commence the repair scope. A combination of sound engineering, correct equipment selection, team work and good communication, allowed the repair to run without issue and on schedule. Only 19 days later on the 4th July 2014, the CLV Ndurance left the work site after tests confirmed that the fault section had successfully been replaced and the export cable was again fully functioning. The RWE project manager Martin Knagg, commended the professionalism of VBMS and their capabilities during the very delicate repair operation.

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