EN.SURE

EN.SURE State-of-the-art Temperature Measurement System

LIOS EN.SURE is based on state of the art distributed temperature sensing (DTS) monitoring systems customised for the electrical T&D industry. One single EN.SURE evaluation unit provides fast temperature sensing profiles with high spatial resolution along the optical fibres route with monitoring ranges up to 40km per channel.

The LIOS‘ DTS technology has been successfully proven in critical applications like fire detection in road and rail tunnels and special hazard buildings, power cable and aerial transmission line monitoring, in oil & gas exploration for permanent downhole monitoring and for industrial induction furnaces surveillance, where these systems have been equipped in world-wide projects with more than 2500 permanent installations.

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EN.SURE DTS System

LIOS EN.SURE is based on state of the art distributed temperature sensing (DTS) monitoring systems customised for the electrical T&D industry. One single EN.SURE evaluation unit provides fast temperature sensing profiles with high spatial resolution along the optical fibres route with monitoring ranges up to 40km per channel.

The LIOS‘ DTS technology has been successfully proven in critical applications like fire detection in road and rail tunnels and special hazard buildings, power cable and aerial transmission line monitoring, in oil & gas exploration for permanent downhole monitoring and for industrial induction furnaces surveillance, where these systems have been equipped in world-wide projects with more than 2500 permanent installations.

Most of these applications are safety relevant and require high reliability and uptime of the sensor system. The EN.SURE DTS product series was carefully designed and thoroughly tested targeting reliable performance and smooth operation in industrial environments. Excellent Mean-time-between-failures (MTBF) of 28 years was reached based on the latest statistical field analysis of the current DTS product series.

Technical Highlights

  • Highly reliable industrial design with key components approved by the telecom industry (tested according to Telecordia standard GR-468, with medium lifetime >25 years)
  • Signal processing based on patented Raman OFDR-Technology (Optical Frequency Domain Reflectometry)
  • Superior hotspot detection along the whole sensor cable length even at most remote distances based on the invariant OFDR spatial resolution
  • Flexible and direct connection to management systems such as SCADA and real time thermal rating (RTTR) software calculation engines based on IEC, AEIC and IEEE standards
  • Up to 16 internal fibre optic channels – 1 EN.SURE DTS unit can cover the most complex power cable circuits
  • Temperature resolution better than 1 °C
  • Laser product class 1M according to DIN EN 60825-1: 2007
  • Maintenance free and simplified outdoor installation capability through higher allowed operating temperature range and fan-free DTS unit design
  • Impressive track record with more than 2500 permanent units installed worldwide

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EN.SURE Real Time Thermal Rating System

Rising demand for electricity is creating the need for utilizing important transmission backbones at their maximum capacity. Enormous benefits can be generated by improving utilization of existing and future installations, and this is where EN.SURE can supply valuable assistance. Based on the real time temperature measurements along the entire cable circuit and the actual electrical current reading EN.SURE offers the exact dynamic cable rating of the installation, based on the IEC 60287 and IEC 60853 standards.

The embedded RTTR calculation engine computes the current-carrying capacity (or ampacity) under given conditions of the underground cable installation for the steady state and transient. Cable Operators will greatly appreciate the transient simulation that will allow them to estimate the current that can be safely transferred from another circuit to the monitored installation, due to unusual operating conditions in situations such as emergencies, maintenance, outages, faults, etc. The EN.SURE RTTR engine can be used for emergency ratings from 10 minutes and up to 2000 hours. This covers the entire emergency rating spectrum since typically emergencies last a few hours or days.

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Power cable monitoring combined with Real Time Temperature Rating (RTTR) provides valuable data to Operators:

  • Power cable conductor temperature at the core of the conductor
  • Predictions for emergency ratings, transient calculations for Time/ Current/Temperature

Furthermore, the RTTR system can provide continuous and automatic adjustment of calculation parameters such as ambient temperature, thermal resistivity, etc..

Why adding RTTR to Distributed Temperature Sensing?

Real Time Thermal Rating (RTTR) or Dynamic Cable Rating removes all uncertainty left by the DTS. The DTS measures the real time temperature at the sheath or jacket of a cable. The sheath temperature gives a good idea of the temperature of conductor, but unless an accurate model for the conductor is provided there will be some uncertainly left. The uncertainty is small during steady state operation, but it could be (very) large during an emergency situation. The following figure illustrates the temperature of the jacket and conductor during an emergency situation.

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One can appreciate that while the temperature difference between the jacket and the conductor can be small in steady state. However, moments after the onset of an emergency situation the temperature difference could be very large. The reason is that cable insulation has a large inertia and therefore the heating of the conductor can only be detected at the jacket several minutes (to hours) later. Additionally, the temperature difference changes with the loading level. The temperature difference is larger for larger loading levels.

Typically the actual maximum temperature reading of each configured cable section and the actual electrical current reading are computed to build the dynamic cable rating of the installation, based on the IEC 60287 and IEC 60853 standards.

Intelligent and Precise Load Management Even During Hot Emergency Events

The EN.SURE emergency rating provides the following information useful for the cable operator under newly given operating conditions:

  • Based on a higher load applied for so many hours: What will the cable temperature be at the end of the emergency case?
  • Given the operating temperature and the applied (over) load, the EN.SURE RTTR solution predicts the temperature of the cable in the future.
  • Based on a higher load for a given period of time: When will the installation reach its design emergency temperature?
  • Given the operating temperature and the applied (over) load, the RTTR gives the time that it will take for the cable to reach a specified emergency temperature.
  • Based on initial conditions and a maximum operating temperature: What is the maximum current that can be carried by the system?
  • Given the operating temperature and a time frame for an over load, the EN.SURE RTTR computes the maximum current that the circuit can carry to reach certain emergency temperature.

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The passive and maintenance-free fibre optic sensor cable is the basis for the EN.SURE real time condition monitoring solution, either integrated directly inside an insulated high voltage underground cable (for instance FIMT, fibre in metal tube) or mounted externally on the cable jacket or installed in a separate duct close to the power cable.

LIOS Technology provides the appropriate sensor cable for every application. The optical fibres are the most important components in the sensor cable. The optical fibres are preferably encased in a stainless steel tube which significantly increases the mechanical stability of the cable. In addition, the inside of the pipe is lined with gel to ensure that the sensor cable remains permanently water-proof. There are various options for jacketing the outside of the stainless steel tube, so that the sensor cable can be optimally adapted to every application.

Also fully dielectric cable design types are available where no grounding precautions needs to be taken.

The fact that temperatures are measured purely optically produces two major advantages for this technology. Firstly, the high electro-magnetic tolerance means that fields of disturbance, such as the high voltage cable itself, electric motors (pumps etc.) or any kind of transmitter (e.g. mobile phones), do not trigger disturbances. Secondly, the sensor cable is practically maintenance-free. All maintenance work can be performed from the evaluation unit.

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The optical fibre serves as the distributed temperature sensor for LIOS EN.SURE DTS systems and is typically surrounded by a protective layer. It is preferably encased in a stainless steel tube which significantly increases the mechanical stability of the sensor.

Fibre encapsulated in stainless steel tube or short “Fibre In Metal Tube (FIMT)” is a hermetically sealed rugged construction for very long lengths of optical fibres. Furthermore, it is particularly effective in protecting against the hydrostatic pressures, high temperature effects and corrosive environments.

The inside of the FIMT metallic tube may lined with gel to ensure that the sensor cable remains permanently water-proof. This viscous gel protects the fibres from many environmental concerns, prevents damage from microbending conditions and helps to minimize the forces applied during spooling and deployment.
An important parameter to consider with FIMT is the Excess Fibre Length. It is defined by the percentage of excess fibre loaded into the metal tube during processing to relieve induced stresses directly related to the differing thermal coefficient of expansions of each material contained in the construction. FIMT is exposed to drastic and often rapid changes in temperature and pressure, so the Excess Fibre Length must be considered to ensure continuous, robust performance across all operational conditions.

FIMT constructions contain individual or multiple fibres (single mode or multi mode) and are available in sizes ranging from 1 mm to 3 mm outer diameter, variations in effective wall thickness are possible as well. FIMT serves as the core for various fibre optic sensor cable constructions or may be integrated into high voltage cable designs directly.

The FIMT is manufactured from a special stainless steel strip. During the manufacturing process this strip is formed to a tube and welded along its length. The stainless steel tubes must be hermetically sealed for all applications. For this reason the complete weld seam is subjected to a leak proof test by means of eddy current. By means of a drawing process the desired final diameter is attained on the one hand and an increase in strength through cold conversion on the other. During the manufacturing process the optical fibres are inserted into the tube. They are clearly differentiated by means of a specific colour code. At the end of the production process the tubes are subjected to a complete optical attenuation measurement and then documented for back-tracing. Additionally, each length produced is subjected to a weld penetration test, each weld seam undergoes a leak test, and the Excess Fibre Length is checked.

LIOS offers a variety of FIMT constructions perfectly suitable for distributed temperature sensing applications along power cable transmission systems.

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The crucial benefit of this cooperation between two leading suppliers to the T&D market is characterised by the innovative concept of Global Condition Monitoring supporting different sensors (PD, DGA, DTS, Tan-delta and Vibrations) through a unique system integrating diagnostic algorithms upon data coming from these sensors. This complemented combination of DTS and PD solutions provides grid owners an even better control and monitoring possibility of their grids.

LIOS in cooperation with its partner TechImp provide the world’s first combined Distributed Temperature Sensing (DTS) equipment together with Partial Discharge (PD) solutions to the power industry. This complemented combination of DTS and PD solutions provides grid owners an even better control and monitoring possibility of their grids.
Together with Real Time Thermal Rating (RTTR), a platform has been created for a complete scope of condition assessment, control, monitoring and ampacity predictions.

The Global Condition Monitoring approach allows most of the failure modes of apparatus and electrical assets to be diagnosed, thus increasing reliability and decreasing maintenance costs, thanks to phenomena correlation.

  • Diagnostics allows failure uncertainty to be reduced.
  • Optimization of the maintenance procedures
  • Condition Based Maintenance
  • Maximization of the system components availability.

The crucial benefit of this cooperation between two leading suppliers to the T&D market is characterised by the innovative concept of Global Condition Monitoring, based on general purpose platforms, supporting different sensors (PD, DGA, DTS, Tan-delta and Vibrations) through a unique system integrating diagnostic algorithms upon data coming from these sensors. Therefore an overall reinforcement of the diagnostic effectiveness and robustness of the diagnostic power is obtained, but at a lower cost.

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Such a superior diagnostic power is achieved by advanced tools, formerly developed for PD, based on TechImp’s unique SID (Separation, Identification, Diagnosis) strategy, which allows noise rejection, PD source separation and identification. TechImp patented technology provides a powerful and efficient diagnostic approach able to disentangle even the most critical PD phenomena, thus improving PD identification from different overlapping PD and noise sources.

TechImp PD separation technology allows different Partial Discharge phenomena to be classified on the basis of their pulse shape and split in different clusters (TF map®), so that further analysis can be carried out on each dataset, separately. This enhances the likelihood of PD source identification, even for non skilled operators.

Now this technologies have been extended to integrate novel sensors and data, adding integrated diagnostic levels based on fuzzy logic and artificial intelligence techniques for a cross-correlation on the whole set of data, giving a better and global coverage of possible faults, comprising, electrical, chemical/physical, mechanical degradation of the monitored electrical asset.