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Online Condition Monitoring with Dynamic Cable Rating Pioneered at Medium Voltage Cable System in Switzerland

Online Condition Monitoring with Dynamic Cable Rating Pioneered at Medium Voltage Cable System in Switzerland

The growth of new renewable energy sources and distributed generation as well as the rising demand due to new applications like electro mobility will lead to increasing requirements as to network capacity. To meet this demand in Switzerland´s most popular metropolis Zurich, ewz, the municipal electric utility, is currently investigating and testing smart grid solutions.

The power cable manufacturer and partner for this project Nexans Suisse SA has selected the  unique frequency domain based Distributed Temperature Sensing EN.SURE DTS system by LIOS Technology. More than 2500 permanent installations worldwide, the comprehensive and 100% applied Factory Acceptance Test (FAT) of each DTS unit as well as the reliability and high precision of measurement results has fully satisfied Nexans.

Management of high thermal load on medium voltage level

The installation is an 11kV medium voltage cable system with 3 circuits, 3 phases each. The cable length is approximately 2700m and the DTS covers the entire power cable sections as well as respective joints. High energy consumption topped by demands for drilling works at a nearby tunnel construction site can lead to high cable loads. The cable system runs in a buried multiple duct system below street level. Neighbouring medium cable systems and a 150 kV high voltage cable system installed in parallel affect the thermal conditions additionally.

Online temperature sensing was requested for this cable project to ensure stable and reliable operation conditions. The  embedded Real Time Thermal Rating (RTTR) solution by LIOS was an important part of the delivery, besides the DTS system itself. The advantages for ewz of using the online RTTR results in combination with the DTS are the derived conductor temperatures in real time and the emergency calculations to predict critical operation conditions in future. The RTTR software uses ambient conditions like the distributed power cable temperature profile, given by the DTS, the electric current in real time, the thermal resistance of the soil, the cable design parameters and the installation environment for its calculations.

Maximum network efficiency - with high security of supply

The emergency ratings of the LIOS RTTR help to redefine grid load and safety limits. Available resources can be used more profitably and enhance the operating life and safety of the cable system.

The supplied system enables immediate recognition of thermal and mechanical faults in the cables. The condition monitoring system is connected via Ethernet, IEC60870 protocol to ewz’s operational management system and sends temperature and alarm data to the responsible operator directly.  This innovative monitoring technology helps ewz to securely optimise the efficiency of its distribution system.


 Special thanks to:

Nexans Suisse SA, Switzerland and ewz, Zurich, Switzerland  

Nexans Suisse SA, Switzerland and ewz, Zurich, Switzerland




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

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