Subsea cables

Difficult to access and expensive to repair, subsea cables are vital assets that you cannot afford to ignore. Sensornet’s Digital Strain Profiling and Dynamic Cable Rating solutions provide integrity during the critical installation stage and enable better lifetime prediction.

Power cable links can be critical assets in project commercial viabilities. In the Oil and Gas market power links are used to energise offshore installations. Outages have tangible commercial implications and it is therefore critical that project risks are managed more effectively through better asset life management (extensive condition monitoring means more effective maintenance).

Typical Subsea Cable Issues

Most longer length high voltage subsea cable installations are challenging and as a result there are risks that have to be mitigated.

  • Routine testing equivalent to land cables cannot be carried out due to cable length
  • HV XLPE subsea cables are normally dry core designs with lead sheaths – susceptible to fatigue
  • Commissioning tests are even more limited than routine tests therefore any defects introduced as a result of transport or installation are likely to be undetected
  • Quantitative installation data is limited especially if a two pass operation is required (laying and then trenching), mainly visual records are available (ROV surveys)
  • Post commissioning cables are still at risk due to external damage as well as environmental effects such as scour and sediment migration. Exposed cables can vibrate in strong currents and thus susceptible to fatigue failure. Cables buried to much greater depth than expected can overheat and fail due to thermal runaway.
  • Dynamic cable sections may be exposed to conditions outside of their design criteria (large oscillations, greater bending movement)

With Distributed Temperature and Strain Sensing use is made of the Fibre Optic usually embedded in the cable construction for telecom purposes. The fibre is used as a continuous sensor and can supply thermal as well as stress/strain dynamic information to a monitoring station.

 knowledge = power