Power cable integrity and condition monitoring

Distributed Temperature Sensing (DTS) for long power cables

Considering using distributed fiber optic sensing for your power cables monitoring project ?

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How does distributed fiber optic sensing help you manage risk in power cable projects to ensure sustainable, efficient and resilient networks?

Power cables have an anticipated life of 40 years, many last much longer.
Knowing their temperature behavior can help you understand their condition and where they are in their lifecycle. Why replace a power cable when all is going well?

Most high-voltage HV and EHV cables have optical fibers included for monitoring the cable’s temperature.

fibrisTerre interrogators use Brillouin Frequency Domain Analysis (BOFDA). This technique provides advantages for monitoring longer power cables.

A fibrisTerre system detects temperature changes over a distance of 80 km.

More precise measurement provides
  • earlier fault detection and location enabling earlier mitigation
  • reliable data transmitted to a Real-Time Thermal Rating (RTTR) or Dynamic Cable Rating (DCR) software for cable loading optimization.

This means you can monitor the cable’s temperature and condition continuously, all along its length, and receive alarms when the temperature, anywhere along the cable, strays outside its preset limit.

Why monitor onshore cables?

Direct buried, in ducts, and cables in tunnels – all benefit from continuous temperature monitoring.
Challenges to power cables include:

  • Changes in the buried environment and its thermal resistivity (thermal runaway, thermal bottleneck)
  • Water ingress
  • Changes in load and load direction
  • Aging of the materials and insulation.

A fibrisTerre system detects and reports temperature events continuously, allowing the cable to be operated at maximum load, without exceeding its maximum permitted operating temperature.

Why monitor subsea cables?

Offshore windfarms continue to push the boundaries for power cables

  • Increasing distances from shore, larger arrays, offshore grids, and interconnectors
  • Reducing the costs and improving the performance of the cable
  • Expanding wind turbine generation capacity (15 MW turbines in demonstration)
  • Withstanding the challenges that floating windfarm generation brings.

Higher voltage cables are required to transport the electricity and improve the economics of installation, with inter-array cables increasing to 66 kV and export cables moving to 275 kV.

Interconnectors enable energy to be moved efficiently between countries and continents, offering enormous value to populations and businesses.

Direct Electrical Heating (DEH) cables and umbilicals are subject to rapid changes in load.

Temperature along the cable is monitored to ensure the asset is operating within pre-defined limits. If the heating fails, the system can trigger a pipe or flowline shutdown.

The cost of cable failure is high; repairs are slow and difficult.
Condition monitoring with a fibrisTerre system helps you detect and locate an incipient fault, giving you time to mitigate its effects.

Strain event detection, location, and measurement in power cables

Subsea cables

Interconnectors, export, and umbilical cables may suffer strain during installation or rock dumping.
In operation geological faults, scouring, seabed movements, anchor drag, or landslides may strain the cable, even causing it to fail.

The expected lifetime of dynamic floating offshore wind farm cables is difficult to predict.

Dedicated fiber optic strain sensing incorporated within the cable
  • monitors bending and compression during cable installation
  • detects and locates fatigue (strain) developing in the cable during its operation.

Combining strain and temperature monitoring provides insight into the integrity of dielectric materials. The data may be compared to models or digital twins to inform cable maintenance and life expectancy decisions.

Buried cables

Duct settlement, ground movement, or climate effects may affect a cable.
Including a strain sensing fiber within the power cable structure allows it to be monitored, either permanently or surveyed periodically to measure how the strain is developing.