Green DTS
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LIOS Technology Inc.
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We work on condition monitoring solutions for the power industry and markets our fiber sensors also in fire detection and downhole well monitoring.
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DTS are Distributed Temperature Sensing systems which measure temperatures by means of optical fibers functioning as linear sensors.

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.

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CIGRE Session 44: A Gathering of 6000 Executives and Experts from the Worldwide Power Industry in Paris

Posted on June 18, 2012 at 5:35am 0 Comments

Cigre Session 44 - 2012 Palais des Congres Paris - LIOS Technology

LIOS Technology is pleased to cordially invite you to attend the CIGRE Technical Exhibition in Paris:

International Council on Large Electric Systems

Technical Exhibition LIOS booth 232

27 - 31 AUGUST 2012, Palais des Congres de Paris, Paris,…


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Posted on November 18, 2010 at 2:00pm 0 Comments

LIOS Technology has completed a power cable monitoring project at a South American mining facility of Codelco in Chile. The Korean made 220 kV, 630 mm 2 XLPE high voltage cable system includes…


LIOS - 10 Years On- Join us for the Cigré 2010 Session in Paris

Posted on June 20, 2010 at 9:59am 0 Comments

LIOS 10 Year On We at LIOS Technology would like to thank you for your continuous interest in our products throughout the recent years. The year 2010 marks the10th year for LIOS Technology in the industry. The formal company launch dates back to August 2000. LIOS Technology GmbH is pleased to cordially invite you to visit Cigre 2010 Session, taking place on August 22 - 27, 2010 in… Continue

Smartgrid: Why adding RTTR to Distributed Temperature Sensing?

Posted on March 31, 2010 at 10:30am 0 Comments

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… Continue

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