Omnisens - Model Cobra -Fiber Optic Distributed Sensing System for Power Cables

Condition Monitoring
In both underground and subsea cables incipient faults often result in temperature events. Using optical fibers integrated into the power cable or laid close by, Distributed Temperature Sensing (DTS) helps detect changes and faults allowing the operator to intervene before the cable fails. It is suitable for deployment in any cable where an optical fiber is present, including HVDC, HVAC, export, inter-array, transmission and distribution.

Performance and Design Optimization
Power cable performance and design can be optimized using the Dynamic Cable Rating (DCR) module. (Note: DCR is also known as RTTR and DRS).

Monitor condition and performance from the shortest to the longest cable

Omnisens Cobra fiber optic distributed sensing system provides:

Continuous real time monitoring with early detection and location of temperature and/or strain events.

Enabling the operator to:

Monitor even the longest cables all along their length. For subsea cables this means along the entire cable, not just the shore ends. And if it just shore ends, then Omnisens systems enable a longer distance from the shore end. That means more of the cable is monitored against failure.

Detect and locate temperature (or strain) events anywhere along the cable, for investigation.

High performance DTS (Distributed Temperature Sensing).

Enabling the operator to:

Detect, locate and track small events.

Obtain rapid, reliable extrapolations for load management decisions when Dynamic Cable Rating system (DCR) is used.

Dynamic Cable Rating system (DCR/DRS/RTTR)

Enabling the operator to:

Make timely, informed decisions about their cables and maximize the financial performance of these high fixed-cost items.

Modular system

Enabling the operator to:

Benefit from cost effective monitoring for every project, with optional Geographical Information System interface and Dynamic Cable Rating.

Omnisens Cobra is a modular fiber optic distributed sensing solution for power cable condition monitoring and performance optimization.

Omnisens Cobra provides high performance, long distance monitoring enabling operators and utilities to optimize their power cables.
The system comprises:

Omnisens High Performance Distributed Temperature Sensing (DTS)
Based on Brillouin or Raman scattering depending on the project requirements, DTS detects, locates and profiles small temperature changes along the entire length of a power cable continuously, in real time.

• Omnisens DITEST (Distributed Temperature and Strain Sensing) interrogators are based on Brillouin sensing using single mode optical fibers as the sensor. The DITEST is a DTS which provides effective monitoring of long cables, or where the sensing fiber experiences significant optical loss, with consistent spatial resolution. It detects temperature and/or strain. Due to manufacturing, transport and installation challenges of long cables, the sensing fiber may be placed under tension and strained. The affected cable sections can be successfully monitored for temperature using compensation techniques developed by Omnisens. Whether unintentionally detected or actively monitored for using an appropriate fiber optic sensor design, strain provides another insight into the power cable`s condition. Knowing where strain exists or is developing, the operator can mitigate against the effects this may have. One or more dedicated servers are included for data processing and storage.
• Omnisens Raman DTS interrogators provide temperature monitoring of power cables using multimode optical fiber as the sensor. For many cables, particularly shorter, direct buried cables, this is an ideal solution.

Omnisens Map
An optional customizable graphical user interface, Omnisens Map provides a simple ‘see at a glance’ visualization of the entire asset, showing alerts and events.

Information from Omnisens Cobra Dynamic Cable Rating can be integrated into Omnisens Map, e.g.: position of lowest and highest monthly temperature.

Dynamic Cable Rating.
The optional Dynamic Cable Rating (DCR) module establishes the relationship between load and temperature. This information helps manage the performance of the cable as well as providing ratings in emergency situations.
Dynamic Cable Rating uses algorithms based on IEC 60287 and 60853. The DCR calculates the conductor temperature based on the cable construction, electrical design, laying configuration and environment.

Knowing the temperature of the conductor and the load, the following predictions can be made:

• Time before maximum temperature is reached, given a permanent or dynamic load pattern and the maximum conductor temperature limit for the cable
• Temperature of the cable at the end of a given period of (over) load
• Maximum ampacity of the cable, given the duration (time) and the allowable temperature during an emergency situation.

During design studies for new cables, Dynamic Cable Rating informs decisions on specifications, e.g.: conductor diameter.
(Note: DCR is also known as RTTR and DRS)