• Home
  • |   Follow us on
  • For regular industry updates, follow LIOS on Twitter
  • Join LIOS on Facebook - Distributed Temperature Sensing
  • Follow LIOS Technology - Linear Optical Sensors on LinkedIn
  • Subscribe to LIOS RSS feed
Real-Time Cable Thermal Rating (RTTR) went on-line at a tunnel near Stockholm, Sweden

Real-Time Cable Thermal Rating (RTTR) went on-line at a tunnel near Stockholm, Sweden

A condition monitoring system (CMS) has been designed and installed as part of a new 245kV power cable circuit in Stockholm, Sweden by LIOS Technology. The principal aim of the CMS is to provide real time monitoring of cable conditions, and to assist in asset management to ensure reliable cable operation.

The major features of the CMS are the cable temperature monitoring and prediction functions based on a distributed temperature sensing system (DTS).
In October 2006 the commissioning of the integrated RTTR solution for real-time monitoring of cables was successfully completed. Together with a Distributed Temperature Sensor (DTS) from LIOS Technology of Germany, a parallel run of cables installed in a tunnel near Stockholm is being continuously rated by RTTR.
The RTTR calculation engine is supplied by CYME of Canada. The cable installation, owned by the Swedish utility Fortum consists of 3 km of a double circuit of 245 kV cables fitted with optical fiber sensors installed in a 20 m deep tunnel. The DTS measures the temperature external to the jacket of the cables and the ambient temperature of the tunnel. Real time temperature and current readings serve to compute the temperature of the conductor and perform emergency ratings looking into the future.


  • The cables have been installed in a 20 m deep tunnel specially constructed for housing the cables. The selected arrangement is two parallel runs of cables in trefoil.
  • Condition monitoring system (CMS)
  • Integrated measurement data in real-time
    - DTS temperature data from multiple units
    - Electrical current data from multiple circuits
  • Interface to RTTR calculation engine
    -Open interface to embed various RTTR calculation engines
    -Selection and assignment of the rating cases
    -Calculated results are stored, visualised, further processed and exported
  • RTTR calculation
    -Conductor temperature per thermal section
    -Prediction of emergency ratings per thermal section 

End user
Fortum Distribution Stockholm

DTS and RTTR commissioning 
October 2006

EN.SURE Power Cable Condition Monitoring Information

EN.SURE - Load Management, Optimization and Save Grid Operation

EN.SURE  is a continuous and cost-effective monitoring solution of the electric power transmission and distribution grid and is the key factor for a successful Smart Grid implementation.

EN.SURE DTS Brochure

EN.SURE Real Time Thermal Rating RTTR Brochure

» Technology behind Distributed Temperature Sensing

» LIOS sets benchmarks in reliability and track record