V-TES was approached by a major North Sea Oil & Gas operator following a cable fault being suspected on the 11kV subsea incomer/interconnector cabling between two offshore platforms.

The requirement was to carry out Time Domain Reflectometer (TDR) testing of the 11kV feeder cable between platforms after a failure during operation. The length of the subsea cable was believed to be approximately 5.1km, which was discussed and confirmed by the platform electrical technicians.

Testing was to be carried out at both platforms to build up a clear picture of the precise location of the failure within the cable.

At short notice, V-TES deployed an Engineer, all required testing equipment and software to go to the offshore locations in order of completing TDR & IR testing on the 11kV / 5km subsea cable.

Multiple meetings were held between V-TES and other project teams, including the Global Marine Group and cable manufacturers to make sure that the best solution was being offered for repairing or replacing the 11kV cables (HV and with Fibre Optic included).

It was decided the best route forward was to replace the cabling due to there being water ingress detected.

V-TES sister company, AISUS, carried out work to clean the J tubes, burst the diaphragms and run-in messenger lines to allow the ease of access for the new Subsea cables coming from the seabed and up to the platform.

V-TES mobilised the HV jointing & fibre optic team to work between the offshore locations. This included preparation works to the connection cubicles, cable containment, checking & marking up drawings and making sure all was in place to accommodate the newHV and FO cables/terminations.

The Engineers moved from platform to platform, and rolled from days to nights and back to days to work around platform operations, all whilst working closely with the cable-laying vessel Normand Cutter of Global Marine Group.


The requirement was to replace, terminate, test and
commission the main 11kV interconnector HV subsea
and fibre optic cabling between two offshore oil and
gas platforms in a time-critical window.

The project was split between two offshore platforms
The test kit and special tooling needed to be logistically precise, as it was shuttled from platform to platform
V-TES Engineers rolled from day to night shift and back again, in order of working at the most optimal shifts/times
Multiple parties were involved
Time and safety-critical
11kV – brings a high level of skill and training to ensure the works are carried out to the highest standard

To arrive at the best course of action and solution, multiple planning and preparation meetings were held. This ensured that all options were considered and the best approach was taken as soon as the cable fault was sourced.

  • V-TES, multiple partners and client all involved in the prep leading up to the full install and replacement of the 11kV subsea cabling.
  • V-TES opted to supply 2 Engineers as opposed to the original 4 (2 on each platform). The reason and thought process behind this was to limit personal due to reduced POB allocation on the platforms during a high-profile project.

V-TES ensured that both Engineers were dual-trained to carry out the 11kV HV Jointing & Terminations (all V-TES Engineers are trained to the highest standard via Nexans training centre) and that they could perform “FO” fibre optic splicing, terminations, and testing on the main FO cable. This was coupled with the Engineers being trained and experienced to
perform all the HV and FO cable testing from both platforms.

This provided the client and all of the associated partners, the confidence before energising the 11kV cable and FO communications line


Overall, the project ran smoothly, on time and produced great results. All of the HV and fibre optic testing was complete with no issues. Client provided feedback highlighting the success of the wider project which was safely and executed on time. The client now has full power at its disposal from both platforms within the field.

Reduced POB
Dual skilled team
Clear Communications
Full project solution from one provider. Testing / Critical Parts / Installation / Commissioning / project work packs

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