LIOS Technology has been awarded to supply the online condition monitoring system for one of the largest 500 kV high voltage cable projects – a milestone in modernizing Russian industry and infrastructure.
The Federal Grid Company of Unified Energy System (JSC FGC UES) selected LIOS’ highly reliable distributed temperature sensing system based on OFDR technology for Russia’s high-technology hub Skolkovo. Load management, optimization and save grid operation describe the key factors for Russia’s federal grid company to equip the 11,5 km double circuit of 500 kV underground transmission cable with the latest fibre optic real time condition monitoring system.
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INTRODUCTION
This report shows the results of cryogenic test for confirming the KC-1 cargo containment system which will be applied to LNG ship. Open mock-up tank has already been built to prove the fabrication, assemble and construction procedures of KC-1 membrane system for ship application. A LNG carrier closed type mock-up tank as recently built, hereafter CMT, of the KC-1 type membrane system.
Experimental stress analysis systems equipped with strain gages and fibre optical sensors have been reflected in the design to perform a cryogenic test. CMT cryogenic tests were conducted by filling and discharging LNG 5 times and all the tests have been successfully completed in October 2009.
The purpose of construction and cryogenic tests of CMT are as follows
(1) Confirming the stability of KC-1 membrane system during cryogenic test
(2) Improving the quality control system of membrane and insulation system of LNG tank which assures the reliability of LNG carrier
(3) Evaluating the applicability of automatic welding machine on KC-1 membrane system
(4) Intensifying the techniques of design, material, fabrication and inspection required for the design of LNG carriers
SPECIFICATION OF CMT
This size of the tank is 12m long, 14 m wide, 7m high and inner volume of 250m3. Its construction was commenced in September 2008 and brought to completion in April 2009.
CMT is connected to DCS (Distributed Control System) of Pilot LNG Plant and operations are controlled at remote control room. CMT’s cryogenic tests were performed by repeated charging and discharging LNG for 5 times. Before operation, pre-cooldown test were also performed to lower the temperature of primary membrane to LNG temperature by spraying liquid nitrogen. Construction and cryogenic tests of CMT adopted in KC-1 membrane system were made with the purpose of consolidating the design/fabrication technology, establishing the building system for LNG carriers, establishing the quality control for construction procedure and proving the KC-1 membrane system experimentally.
CMT OPERATIONS
The following figure shows the variation of liquid level and primary membrane’s temperature during operation. IB and IBS spaces filled with nitrogen were sampled regular intervals to check the leakage of LNG during operation. After the operation of 1st and 5th pre cool down, CMT was opened and primary membrane system was checked through visual inspection.
TEMPERATURE MEASUREMENT SYSTEM
Liquefied natural gas (LNG) normally has a temperature of -162°C, so all the storage facilities such as insulation and hull systems are subject to temperature decrease caused by long-term storage. RTD sensors were installed at several points of CMT for the purpose of monitoring CMT only for the period of operation. The LIOS fibre optic temperature measurement for CMT structure has been developed to investigate the temperature distribution of KC-1 membrane system.
In case of KC-1 type cargo containment system, cone type membrane anchor structures are fixed in hull and support the reaction force of membrane during operation. Since the fibre optic sensor cable is coiled around cone anchor and measures the temperature every 50cm interval, it is possible to investigate the temperature distribution of CMT.
Two fibre optic cables were installed in the insulation and a third one was included on the cone anchor to investigate the distribution of temperature during operation. The following figure shows the whole temperature distribution of CMT during operation. All the measured data were plotted at the maximum LNG level.
The LIOS DTS system as well as the design of the applied fibre optic sensor cable could be successfully approved as an effective and reliable integrity monitoring system for the KC-1 cargo containment system. The cryogenic temperature measurements are precise and stable in course of the entire test period.
01
Mar
10
Monitoring System for Overhead Line Conductors. Meeting the demands of a changing power environment
Providing sufficient electrical power reliably requires ongoing monitoring of temperatures within overhead transmission lines that are more susceptible to atmospheric changes than buried cables. Winds, direct sunshine, ambient temperature, rain, ice and snow all affect the temperature of exposed overhead lines and can dramatically impact load limits they are capable of carrying. The fibre optic monitoring system for overhead lines is an inexpensive and highly reliable method that enables real-time monitoring of an entire network or of selected critical spans.
The easy-to-install, low-maintenance system offers a multitude of advantages. By enabling dynamic analysis of network structure, it increases the overall safety and reliability of the grid. It facilitates applying dynamic reactions to transmission requests, resulting in more flexible capacity and revenue management in both the short and long term. And the potential for cost-savings is enormous: downtimes and blackouts can be avoided, and the need for new lines and upgrades (e.g. increasing the height of overhead transmission lines) can be greatly reduced.
Customers dynamically rating the critical spans of their overhead line system can also increase earnings by activating previously unused resources in existing power lines. Dynamic metering of grid capacity and maximized transmission capacity make it possible to respond quickly and dynamically to transmission requests. As new sources of energy are added to the grid, precise load predictions are possible and it is easier to react quickly to overload conditions.
With the help of dynamic network-structure analysis, temperature profile can be monitored over span fields and fittings, depending on the length of the sensor. Load parameters are bundled and transmitted to network control stations online, allowing for real time thermal rating – which means real time supervision of network capacity. This makes it possible to predict load precisely and to avoid wire fatigue caused by repeated high thermal loads. Because decisions based on thermal load often influence upgrading or installation of lines, this translates into better control of grid and wire conditions, as well as optimal sag control and line clearance without requiring new construction activities.
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.
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.
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11
Dec
09
Fiber Optic Distributed Temperature Monitoring for Oil & Gas Production & Reservoir Engineering
How to get more from available resources
Technology is the key driver in the quest for greater efficiency. In the oil and gas industry, there is keen interest and high demand for low-cost, reliable, and easily installable systems to enhance downhole production and recovery.
Trusted partner
Distributed Temperature Sensing Systems have shown great promise for helping the Oil & Gas industry meet the global demand for energy. LIOS Technology GmbH – a trusted partner to the Oil & Gas industry and a leading expert in fiber optic sensing technology – has unleashed the potential for this technology on a number of exciting oil well projects in the Far-East. Along with Integrated Intelligent Smart Well Service Company, the team has successfully developed downhole temperature sensing systems that meet the sector’s unique requirements for performance, cost-effectiveness, and systems feasibility.
Field-proven reliability
Oil reservoirs represent a harsh environment for sensitive electronic components. Equipment deployed downhole must be able to perform 100 % reliably while withstanding heat, pressure, moisture, vibration, and corrosion. Breakdowns can cause unacceptable delays and lost output costing hundreds of thousands of dollars. LIOS Technology offers the most reliable and functional continuous downhole temperature sensing and logging system available for both simple and complex wells. Our modulebased system and open standard protocols enable us to offer you customized solutions for your unique needs.
Features
- Impressive track record – more than 2000 successful fixed installations in more than 80 countries on all continents
- Dependable and field proven system design – no sensitive electronic components or power supply downhole, only the Fiber Optic cable acting as the sensor
- Rugged and durable semiconductor laser diode sensor. Fulfils Telcordia GR-468 quality standard with average product lifetime of 25+ years
- Patented OFDR technology (MM or SM) based on Raman effect delivers temperature readings accurate to within ± 0.06° C (±0.1 F) and 0.5 m (1.5 ft) along the entire sensor length from distances up to 30 km (98425 ft) away
- Market leading calibration features like automated point calibration using 3 rd party temperature source, multi fiber segment calibration and double ended calibration operation mode
- Low-cost third-party optical pressure gauges can be added using the same fiber optic cable for even more detailed measurements
- The multichannel LIOS DTS unit can accommodate up to 8 independent fibers, enabling comprehensive surveillance and Real Time Field Management (RTFM) of multiple wells
- Entirely self-contained DTS unit transmits measurement data via cyber secure, TLS encrypted link to remote SCADA database systems. No on-site PC to power or hack into
- No need to visit well-site to collect data
- Entire DTS system is independently certified for quality by VdS [the German asset insurers association] and many other international certifying bodies
24/7 Data-to-Desk – Easy to install and integrate
Here at LIOS Technology, our goal is to deliver optimal communication solutions to you. We supply your specialists with accurate and real-time information delivered to their desks round-the-clock so that critical decisions can be made immediately. LIOS Technology can easily and economically interface its DTS temperature and pressure measurement system with your system to create a fully Data-to-Desk solution customized to your needs.
Increasing demand for power is forcing power utilities to load power cables to their physical limit, and safety and efficiency concerns are making it more and more critical for operators to understand what is happening thermally both inside the cables themselves, and along the cable route.
Real Time Determination of Thermal Conditions along HV Power Cable Systems
During high-load conditions and under emergency circumstances (such as when a failure occurs in a segment of the grid and power must be shifted to other sections to compensate) it often becomes necessary to load cables right up to the limits permitted by the relevant regulations. In these operational situations, it must be ensured that maximum temperature limits are not exceeded. Due to the increasing complexity of the thermal relationships along cable routes, the ability to continuously measure the temperatures along the cable has proven invaluable, providing critical operational data to engineers, especially in the case of a system faults such as a hot spots that could result in cable failure if they are not corrected.
The intrinsic temperature measuring system DTS based on LIOS Technology’s design, with fibre optic sensors either installed within the power cable’s cross section (FIMT – Fibre in metal tube ) or attached to the exterior of the cable, makes it possible to record the temperature profile along an entire cable route continuously, and to pinpoint the exact location of hot spots within a metre. Since the measuring principle employed is purely optical, the presence of electromagnetic influences, which can result in false sensor signals in other technologies, does not affect the DTS unit.
Distributed temperature sensing is a powerful tool that allows the accurate rating of high voltage power cables in real time, and provides the following operating benefits:
- Reduce power outages or blackouts
- Ensure continuity of supply
- Activate hidden capacity reserves of existing assets
- React quickly to overload conditions
- Conduct precisely and in real-time load predictions as new sources of energy are added to the grid
The temperature profile data, in any desired form or format, can be transmitted via standard interfaces from systems of the OTS product series as required, and be either displayed or further processed by PC, PLC or SCADA systems. As a result of the increasing demands placed on the ability to network and integrate measuring systems into management systems, LIOS offers network components that summarise DTS data from several DTS units and transport or convert it to the required network standards and protocols like Modbus, DNP3, IEC60870-5 or XML based data interfaces.
Dynamic Cable Rating
LIOS also provides an integrated Real Time Thermal Rating (RTTR) package via a well defined interface between its DTS data visualisation software and a commercialised – the industry’s de facto standard – cable ampacity program based on IEC standardised methods (mainly IEC 60287 and IEC 60853). Dynamic rating software couples the accurate temperature data provided by the DTS unit to predictive functions of cable ratings, providing engineers with even more information upon which they can base distribution and load decisions. The result is dramatically more efficient transmission of power, fewer “brown-outs”, and decreased operating costs.
Distributed Temperature Sensing Systems (DTS) are optoelectronic devices which measure temperatures by means of optical fibres functioning as linear sensors. Temperatures are recorded along the optical sensor cable, thus not at points, but as a continuous profile. A high accuracy of temperature determination is achieved over great distances.
Measuring Principle – Raman Effect
Physical measurement dimensions, such as temperature or pressure and tensile forces, can affect glass fibres and locally change the characteristics of light transmission in the fibre. As a result of the attenuation of the light in the quartz glass fibres through scattering, the location of an external physical effect can be determined so that the optical fibre can be employed as a linear sensor.
Optical fibres are made from doped quartz glass. Quartz glass is a form of silicon dioxide (SiO2) with amorphous solid structure. Thermal effects induce lattice oscillations within the solid. When light falls onto these thermally excited molecular oscillations, an interaction occurs between the light particles (photons) and the electrons of the molecule. Light scattering, also known as Raman scattering, occurs in the optical fibre. Unlike incident light, this scattered light undergoes a spectral shift by an amount equivalent to the resonance frequency of the lattice oscillation.
The light scattered back from the fibre optic therefore contains three different spectral shares:
- the Rayleigh scattering with the wavelength of the laser source used,
- the Stokes line components with the higher wavelength in which photons are generated, and
- the Anti-Stokes line components with a lower wavelength than the Rayleigh scattering, in which photons are destroyed.
The intensity of the so-called Anti-Stokes band is temperature-dependent, while the so-called Stokes band is practically independent of temperature. The local temperature of the optical fibre is derived from the ratio of the Anti-Stokes and Stokes light intensities.
Measuring Principle – OFDR Technology
Latest DTS evaluation units deploy the method of Optical Frequency Domain Reflectometry (OFDR) . The OFDR system provides information on the local characteristic when the backscatter signal detected during the entire measurement time is measured as a function of frequency in a complex fashion, and then subjected to Fourier transformation. The essential benefits of OFDR technology are the quasi continuous wave mode employed by the laser and the narrow-band detection of the optical back scatter signal, whereby a significantly higher signal to noise ratio is achieved than with conventional pulse technology (OTDR). This technical benefit allows the use of affordable semiconductor laser diodes and electronic assemblies for signal averaging.
The optical frequency domain reflectometry has been developed as a high-resolution measurement process for the characterisation of optical wave guides with length dimensions of just a few millimetres. In contrast, its application for the Raman backscatter measurement was introduced and patented by the company LIOS Technology.
Schematic system set up
The temperature measuring system consists of a controller (frequency generator, laser source, optical module, HF mixer, receiver and micro-processor unit) and a quartz glass fibre (fibre optic) as line-shaped temperature sensor.
The design is three-channel, since an additional reference channel is required besides the two measurement channels (Anti-Stokes and Stokes). Corresponding to the OFDR system, the power output of the laser runs through the sinus-shaped frequency starting from a starting frequency in the kilohertz range through the ending frequency in the high megahertz range within a measurement time interval with the help of the High Frequency (HF) modulator. The resulting frequency shift is a direct measurement of the local resolution of the reflectometer. The frequency-modulated laser light is connected to the fibre optic-sensor via the optical module.
The continuously back-scattered Raman light is spectrally filtered in the optical module and converted into electrical signals by means of photo detectors. Then the measurement signals are amplified and mixed in the Low Frequency spectral range (LF range). The Fourier transformation of the averaged LF signals results in the two Raman backscatter curves. The amplitudes of these backscatter curves are proportional to the intensity of the Raman scattering of the viewed location. The fibre temperature along the sensor cable results from the amplitude ratio of the two measurement channels.
The optical fiber serves as the distributed temperature sensor for LIOS 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 “Fiber 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 Fiber Length. It is defined by the percentage of excess fiber 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 Fiber Length must be considered to ensure continuous, robust performance across all operational conditions.
FIMT constructions contain individual or multiple fibers (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 fiber 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 fibers 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 Fiber Length is checked.
LIOS offers a variety of FIMT constructions perfectly suitable for distributed temperature sensing applications along power cable transmission systems.
The biggest Danish utility owner has successfully completed the installation of LIOS’ Single Mode DTS equipment to monitor the power cable temperature of an offshore UK wind farm. This wind farm consists of 25 wind turbines and running in total 150.000 hours/year, designed for operational usage for in total 20 years. The high voltage power cable route is approx 20km long and connecting the offshore substation to a substation onshore. The DTS system provides real time distributed temperature sensing of the HV cable sections subsea and those inside the towers and ensures save and stable grid operation. Furthermore it helps activating hidden capacity reserves during dynamic transmission requests.
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Distributed temperature monitoring of power cables
This post is part of Blog Action Day 2009.
For ADWEA’s / TRANSCO’s project ICAD (Industrial City Abu Dhabi ) the German DTS (Distributed Temperature Sensing) manufacturer LIOS Technology GmbH provided its well recognized OTS range equipment along with RTTR (Real Time Thermal Rating) to monitor the temperature of the extra high voltage power cables supplied by cable manufacturer Silec Cable in France.
This project runs on three circuits of 6km each equipped with fibre optic cables.
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