Short answer
High-voltage power cables are monitored through an optical fiber inside or alongside the cable. Distributed Temperature Sensing (DTS) measures conductor-related temperature and hot spots to feed real-time thermal rating (RTTR), while Distributed Acoustic Sensing (DAS) locates excavation, anchor strikes and faults. DuyuSense contributes patented DAS signal processing and FBG interrogation technology to this monitoring architecture.
What does fiber-optic power cable monitoring involve?
Fiber-optic monitoring turns the entire cable route into one continuous sensor using a single optical fiber. Most modern HV land and subsea cables carry fibers next to the conductor or in the armour layer for communication and sensing, and a separately laid fiber cable can do the same job.
An interrogator in the substation or landing station sends light pulses into the fiber and analyses the backscattered light. Depending on the scattering mechanism, it measures temperature, acoustic vibration or strain, each located to within metres along the route.
- Raman scattering: temperature (DTS)
- Rayleigh scattering: acoustic vibration and dynamic strain (DAS)
- Brillouin scattering: static strain and temperature (DSS / BOTDR, BOTDA)
- Fiber Bragg Grating (FBG): high-precision strain and temperature at selected points
How does DTS find conductor temperature and hot spots?
DTS calculates the temperature at every point along the fiber from Raman backscatter and shows the hottest sections of the cable directly. Typical systems deliver spatial resolution on the order of a metre and temperature resolution of about 1 °C or better over tens of kilometres.
Hot spots tend to form at road crossings, ducted sections, routes shared with other cables and areas of dried-out soil. Because the fiber sits in the sheath or armour rather than in the conductor, conductor temperature is derived from the measured temperature and the load current using a thermal model.
What is real-time thermal rating (RTTR)?
RTTR is a dynamic rating method that continuously calculates how much current a cable can carry under its actual thermal conditions. Static design ratings assume worst-case soil and ambient conditions, so part of the real capacity of a cable often goes unused.
RTTR combines the DTS temperature profile, the load current and thermal models based on standards such as IEC 60287 and IEC 60853. The grid operator gets additional loading headroom within safe limits, predicted emergency overload durations and early warning of temperature excursions that accelerate insulation ageing. For offshore wind export cables, with their variable generation profile, this approach is particularly valuable.
How does DAS detect excavation and anchor strikes?
DAS recognises an approaching excavator, drilling rig or dragging anchor from the vibration it produces and reports the location of the event. Third-party digging on land and anchoring and fishing activity at sea are widely cited as leading causes of cable damage.
Every few metres of fiber acts as an independent acoustic channel, so each alarm is tied to a position a response team can go to directly. DuyuSense's patented DAS signal processing targets improved spatial resolution and signal-to-noise ratio for higher event-detection accuracy against background noise from traffic, wind or waves.
- Land routes: excavators, boring machines, piling and road works
- Subsea routes: anchor drag, trawling and dredging
- Landfall zones: shoreline works and small-vessel activity
How are fault location and burial depth changes tracked?
When a cable fails, DAS locates the sudden acoustic and mechanical event on the fiber, while DTS can reveal abnormal heating in the period before the failure. This sharply narrows the search area for the repair crew, or for the repair vessel on subsea routes.
Burial depth changes are tracked indirectly: a subsea section exposed by currents or sand waves shows a different temperature profile and acoustic response from its surroundings. Comparing DTS and DAS data over time flags exposure or excessive burial and directs targeted bathymetry or ROV inspection.
When are strain sensing (DSS) and FBG needed?
Strain sensing is needed when the mechanical load on a cable matters: pulling tension during installation, ground movement, landslide zones or fatigue in dynamic subsea cables. Brillouin-based DSS measures static strain in a distributed way along long routes.
Where higher precision is required at specific points (joints, terminations, J-tube exits, bridge and tunnel crossings), Fiber Bragg Grating (FBG) sensors are used. Near 1550 nm an FBG typically shifts about 1.2 pm per microstrain and about 10 pm/°C, with resolution in the microstrain class. DuyuSense's patented FBG interrogation system is designed for real-time, high-speed readout in harsh environments.
Why is power cable monitoring gaining importance in Turkey?
Subsea power links such as the Marmara and Dardanelles crossings, grid interconnections with neighbouring countries and planned offshore wind projects make fiber-based cable monitoring increasingly important in Turkey. These routes cross busy shipping lanes and anchorage areas, where a single fault can mean long repair times and significant transmission losses.
DTS and Brillouin systems are complementary parts of this architecture and are supplied by other manufacturers. DuyuSense brings patented technology in DAS signal processing and FBG interrogation, together with system design, prototyping, integration, consultancy and training support, and welcomes pilot projects with grid operators and cable owners.
| Feature | DAS | DTS | DSS |
|---|---|---|---|
| Physical principle | Rayleigh backscatter | Raman backscatter | Brillouin scattering (BOTDR / BOTDA) |
| Measured quantity | Acoustic vibration, dynamic strain | Temperature | Static strain and temperature |
| Main use | Excavation, anchor strikes, third-party interference, fault events | Hot spots, RTTR, burial change indicator | Mechanical load, ground movement, installation tension |
| Response time | Real time, milliseconds | Measurement cycle typically in the order of minutes | Measurement cycle typically in the order of minutes |
| Typical range | Tens of km, often cited around 40-50 km | Tens of km | Tens of km |
| Spatial resolution | Typically a few metres | Typically around a metre | Typically around a metre |
Frequently asked questions
How do you monitor a subsea power cable with fiber optics?
An optical fiber inside or alongside the cable is connected to interrogators at the landing station. DTS provides the temperature profile and hot spots, while DAS reports events such as anchor drag, trawling and faults with their location. There are no electronics in the water; all active equipment stays onshore.
What is RTTR used for?
Real-time thermal rating (RTTR) calculates the current a cable can safely carry under its present thermal conditions. By using measured data instead of the conservative assumptions behind static ratings, it gives grid operators additional capacity within safe limits and forecasts of how long an overload can be sustained.
Can DAS detect anchor strikes and fishing damage on subsea cables?
In most scenarios, yes. A dragging anchor or trawl gear produces clear vibration on the seabed before it reaches the cable. DAS reports the approach with its location, and the operator can identify and warn the vessel using AIS. Warning time depends on vessel speed and burial depth.
Can cable burial depth be measured with fiber?
Not directly; it is tracked indirectly. An exposed or over-buried section shows a temperature and acoustic response that differs from its surroundings. Changes in DTS and DAS data over time flag these sections, while exact depth still requires bathymetry or ROV inspection.
Can the fiber inside an existing power cable be used for sensing?
Often, yes. Spare (dark) fibers among those installed in HV cables for communication can be connected to a DTS or DAS interrogator. Suitability depends on fiber type, number of splices, optical loss budget and where the fiber sits within the cable construction.
DTS or DAS for power cables: which do I need?
They answer different questions and are usually used together. DTS tracks thermal state and loading capacity, while DAS tracks mechanical threats and fault events. If thermal management is the priority, DTS leads; if damage prevention is the priority, DAS leads. Both can share separate fibers in the same cable.
Does DuyuSense sell DTS systems?
No. DTS and Brillouin systems are complementary techniques supplied by other manufacturers. DuyuSense develops patented DAS signal-processing and FBG interrogation technology, and works as a project partner in multi-technology monitoring architectures through system design, integration and consultancy support.
What does DuyuSense offer for power cable monitoring?
DuyuSense develops DAS signal processing for third-party interference and event detection, and FBG sensor and interrogation solutions for strain and temperature at critical points. It welcomes pilot projects with grid operators and cable owners. Contact: contact@duyusense.com, +90 212 285 6987.