Typical Subsea Cable Issues
Most longer length high voltage subsea power cable installations are challenging and as a result there are risks that have to be mitigated.
Routine testing equivalent to land-based power cables cannot be carried out due to cable length
HV XLPE subsea power 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.
Power 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 Fiber Optic sensor cable usually embedded in the cable construction for telecom purposes. The fiber is used as a continuous sensor and can supply thermal as well as stress/strain dynamic information to a monitoring station.