The subject matter disclosed herein generally relates to detection systems and in particular, to a detection system for measuring at least one of a component and concentration of the component in a fluid using a photo acoustic spectroscopy (PAS) technique.
Electrical equipment, such as transformers, use fluids having good thermal and insulation properties to encapsulate components of the electrical equipment in a containment vessel for enabling dissipation of heat generated from a coil. The fluid may be an oil such as castor oil, mineral oil, synthetic oil such as chlorinated diphenyl silicone oil, or the like.
Failure of electrical equipment or components of the electrical equipment, such as coils of a transformer, may result in disruption of operation. Monitoring of the electrical equipment to predict potential failures through detection of incipient faults is desirable. A known method of monitoring the electrical equipment involves analysis of various parameters of the fluid that circulates about the equipment.
Presence of total combustible gas (TCG) in the fluid is known to provide information about operating state of the electrical equipment immersed in the fluid. To enable early detection of faults, the dissolved gases within the fluid are analyzed. Presence of gaseous components such as carbon monoxide, carbon dioxide, or the like and their concentrations, for example may be indicative of thermal aging of the equipment. Similarly, gaseous components such as hydrogen, hydrocarbons, or the like may be indicative of a dielectric breakdown among other faults.
Known methods for analyzing dissolved gases such as Gas Chromatography (GC), Optical Spectroscopy, and Photo Acoustic Spectroscopy (PAS), require the extraction of gases from the fluid. The known extraction techniques such as vacuum extraction, and head space extraction methods suffer from drawbacks such as repeatability issues and increased complexity.
There is a need for an enhanced technique to measure at least one of a component and concentration of the component in a fluid used in electrical equipment.
In accordance with one aspect, a system for detecting components in a sample fluid is disclosed. The system includes a first chamber having the sample fluid and a second chamber coupled to the first chamber, wherein the second chamber has a reference fluid. The system also includes a modulated light source for emitting a modulated light beam to the sample fluid and the reference fluid, to generate a first acoustic signal in the first chamber and a second acoustic signal in the second chamber. The system further includes a pressure sensor disposed between the first chamber and the second chamber, for detecting a difference between the first acoustic signal and the second acoustic signal. The system includes a processor based module communicatively coupled to the pressure sensor and configured to receive a signal representative of the difference from the pressure sensor and determine at least one of a component and a concentration of the component in the sample fluid based on the signal representative of the difference.
In accordance with another aspect, a method for detecting components in a sample fluid is disclosed. The method includes emitting a modulated light beam to the sample fluid in a first chamber and a reference fluid in a second chamber, wherein the second chamber is coupled to the first chamber. The method also includes generating a first acoustic signal in the first chamber and a second acoustic signal in the second chamber, in response to the emitted modulated light beam. The method further includes detecting a difference between the first acoustic signal and the second acoustic signal via a pressure sensor disposed between the first chamber and the second chamber. The method also includes transmitting a signal representative of the difference from the pressure sensor to a processor based module and determining at least one of a component and a concentration of the component in the sample fluid via the processor based module, based on the signal representative of the difference.
These and other features and aspects of embodiments of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Embodiments relate to systems and methods for detecting the presence of a component in a fluid using a spectroscopic method. Specifically, a technical effect is that in certain embodiments, the composition and concentration of a dissolved gas in a liquid is determined using photo acoustic spectroscopy (PAS) technique. A light beam from a modulated light source is emitted on a sample fluid in a first chamber and a reference fluid in a second chamber coupled to the first chamber. A pressure sensor disposed between the first chamber and the second chamber, measures a difference between a first acoustic signal generated in the first chamber and a second acoustic signal generated in the second chamber. A processor based module which is communicatively coupled to the pressure sensor, receives a signal representative of the difference from the pressure sensor and determines at least one of a component and a concentration of the component in the sample fluid based on the signal representative of the difference.
In the illustrated embodiment, the modulated light source 202 includes a light source 206 for generating the light beam 254 and a modulator device 208 for generating modulated light beams 220, 222. In one embodiment, the light source 206 is a laser light source. In alternate embodiments, the light source 206 may be a broad band light source, a tunable diode (TD) laser, or a quantum cascade laser source. In the illustrated embodiment, the modulated light source 202 includes a reflector 204 used for reflecting the light beam 254 from the light source 206.
The modulator device 208 modulates the light beam 254 from the light source 206 via the reflector 204 by controlling at least one of an intensity of the light beam, a wavelength of the light beam, parameters of the light source 206 and/or characteristics of the reflector 204. In the illustrated embodiment, the modulator device 208 includes a rotatable disc 209 with a plurality of slots 210. The rotatable disc 209 is used for generating a modulated light beam in the form of light pulses via the slots 210. In alternate embodiments, the modulator device 208 may be used to modulate the intensity of the light beam 254 from the light source 206 by other suitable techniques. In one specific embodiment, the modulator device 208 may be used to modulate the wavelength of the light beam. In some embodiments, the modulator device 208 may also be a part of the light source 206. In certain embodiments, the light beam 254 from the light source 206 may be modulated by varying one of more parameters of the light source 206. In one embodiment, the temperature of the light source 206 may be modified to generate a modulated light beam. In another embodiment, the current used for powering the light source 206, may be varied to generate a modulated light beam. The modulated light beam has a range of wavelength suitable for detecting the presence of one or more components in the fluid.
In the illustrated embodiment, the modulated light source 202 includes a reflector 204 and the light source 206. The light source 206 generates a light beam that strikes the reflector 204 and produces a reflected light beam 254. the modulated light source 202 also includes a filter 212 for filtering the light beam 254, corresponding to the required wavelength. In a specific embodiment, the filter 212 includes a plurality of filter lenses having different wavelengths. Further, a beam splitter 214 and a reflector 215 are used to generate modulated light beams 220, 222 from a filtered output of the filter 212. In the illustrated embodiment, two modulated light beams 220, 222 are generated from a single modulated light source 202. In another embodiment, two laser sources may be used to generate two modulated light beams.
In the illustrated embodiment, the sample fluid 232 includes a component 230 dissolved in a sample liquid 242 and the reference fluid 234 includes a reference liquid 244. In another embodiment, the sample fluid may be a suspension having a component in the sample liquid. In an exemplary embodiment, the sample liquid 242 and the reference liquid 244 may be an insulation oil used in the components to be inspected, for example a transformer. The component 230 may be at least one of gaseous components such as acetylene, hydrogen, methane, ethane, ethylene, carbon dioxide, carbon monoxide, moisture, or the like. In one embodiment, the constituents of the sample liquid 242 may be exactly same as the constituents of the reference liquid 244. In another embodiment, the constituents of the sample liquid 242 may be substantially same as the constituents of the reference liquid 244.
The first acoustic signal 238 generated in the first chamber 218, includes a third acoustic signal 246 generated due to the presence of the sample liquid 242 and a fourth acoustic signal 248 generated due to the presence of the component 230. The “third acoustic signal” 246 referenced herein is a pressure signal generated due to fluctuations in temperature of the sample liquid 242 generated by the modulated light beam 220. The “fourth acoustic signal” 248 is a pressure signal generated due to fluctuations in temperature of the component 230 generated by the modulated light beam 220. The “second acoustic signal” 240 referred herein is a pressure signal generated due to fluctuations in temperature of the reference liquid 244 generated by the modulated light beam 222. In the illustrated embodiment, a light absorption spectrum corresponding to the sample liquid 242 is the same as a light absorption spectrum corresponding to the reference liquid 244. A light absorption spectrum corresponding to the component 230 is different from a light absorption spectrum corresponding to the sample liquid 242.
In the illustrated embodiment, the first chamber 218 is coupled to the second chamber 216 and separated from each other by a diaphragm 224. A pressure sensor 236 is disposed in the diaphragm 224 between the first chamber 218 and the second chamber 216. The first acoustic signal 238 is transmitted to a first side 250 of the pressure sensor 236 and the second acoustic signal 240 is transmitted to a second side 252 opposite to the first side 250 of the pressure sensor 236. The third acoustic signal 246 corresponding to the sample liquid 242 is transmitted to the first side 250 of the pressure sensor 236. In an embodiment where the constituents of the sample liquid 242 are the same as the constituents of the reference liquid 244, the third acoustic signal 246 neutralizes or cancels the second acoustic signal 240 corresponding to the reference liquid 244. In another embodiment where the constituents of the sample liquid 242 are substantially the same as the constituents of the reference liquid 244, the third acoustic signal 246 substantially neutralizes the second acoustic signal 240. In one example, the third acoustic signal 246 is reduced by about 80 dB. In other embodiments, the reduction would be in the range of about 40 to 100 dB.
The pressure sensor 236 detects a difference between the first acoustic signal 238 and the second acoustic signal 240 and generates a signal representative of the difference. In other words, the pressure sensor 236 detects the pressure signal which is representative of the component 230.
In one embodiment, the pressure sensor 236 is positioned in the diaphragm 224. In an alternate embodiment, the diaphragm 224 may be the pressure sensor separating the first chamber 218 from the second chamber 216. In one embodiment, the pressure sensor 236 is a piezo-based pressure sensor. In such an embodiment, the pressure sensor 236 may employ a piezo-electric effect or a piezo-resistance effect to detect the difference between the first acoustic signal 238 and the second acoustic signal 240. In certain other embodiments, the pressure sensor 236 may be a cantilever-based pressure sensor or a membrane based pressure sensor, a microphone, a hydrophone or a capacitance based sensor.
A processor-based module 228 is communicatively coupled to the pressure sensor 236, and configured to receive the signal representative of the difference between the first acoustic signal 238 and the second acoustic signal 240 from the pressure sensor 236. The processor-based module 228 is also configured to determine at least one component and a concentration of the component 230 in the sample fluid 232 based on the signal representative of the difference between the first acoustic signal 238 and the second acoustic signal 240.
The processor-based module 228 may include a controller, a general purpose processor, or an embedded system. The processor-based module 228 may receive additional inputs from a user through an input device such as a keyboard or a control panel. The processor-based module 228 may also be communicatively coupled to a memory module such as a random access memory (RAM), read only memory (ROM), flash memory, or other type of computer readable memory. Such a memory module may be encoded with a program to instruct the processor-based module 228 to enable a sequence of steps to determine at least one of the components and the concentration of the component 230. In an alternate embodiment, all the components of the exemplary detection system 200 may be incorporated as a single stand-alone module integrated with inspection systems 108, 110 (shown in
The modulated light beam is also transmitted to a reference fluid in a second chamber 1308. In one embodiment, the reference fluid includes the insulation oil of the transformer system as the reference liquid. A second acoustic signal is generated 1310 in the second chamber and is representative of a pressure signal corresponding to the reference liquid. The first acoustic signal is transmitted to a first side of the pressure sensor disposed between the first chamber and the second chamber. The second acoustic signal is transmitted to a second side opposite to the first side of the pressure sensor. The third acoustic signal corresponding to the sample liquid fully neutralizes or substantially neutralizes the second acoustic signal corresponding to the reference liquid 1312. The pressure sensor detects a difference 1314 between the first acoustic signal and the second acoustic signal.
The signal representative of the difference may include one of an optical signal, an electrical signal, and a pressure signal based on the type of the pressure sensor used. The signal representative of the difference is transmitted from the pressure sensor to a processor-based module 1316. The processor based module measures an amplitude value of the signal representative of the difference. In one embodiment, the measured amplitude value may be a peak value of the signal representative of the difference. In one embodiment, the phase information of the signal representative of the difference may be used to determine the amplitude value.
The processor based module determines the component 1320 based on the range of wavelength of the modulated beam. In some embodiments, a look-up table having data corresponding to the gaseous components and their corresponding absorption spectral range may be used to determine the component. In one example, if the wavelength of the modulated light beam corresponds to a wavenumber in the range of 2200-2400 cm−1, the processor based module determines the component as carbon dioxide. In another example, if the wavelength of the modulated light beam corresponds to a wavenumber in the range of 2900-3100 cm−1, the component is detected as methane. In yet another example, if the wavelength of the modulated light beam corresponds to a wavenumber in the range of 3200-3400 cm−1, the component is detected as acetylene.
In one embodiment, a concentration of the component may be determined 1322 based on the measured amplitude value, using a predetermined calibration chart. In one embodiment, the calibration chart may be determined based on a transfer function. In another embodiment, the calibration chart may be determined based on simulation results. The calibration chart is a look-up table having data entries of concentration values for a range of amplitude values corresponding to each of the gaseous components.
The exemplary systems and methods for inspection enable determination of a concentration of a component in a fluid using photo acoustic spectroscopy (PAS). The technique detects a small amplitude photo acoustic pressure wave corresponding to the component in a relatively large amplitude photo acoustic pressure wave corresponding to the sample liquid. In the case of electrical transformer systems, for example, the exemplary technique performs analysis of dissolved gas without extracting the gaseous components from the insulation oil.
It is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or improves one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
While the technology has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention are not limited to such disclosed embodiments. Rather, the technology can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the claims. Additionally, while various embodiments of the technology have been described, it is to be understood that aspects of the inventions may include only some of the described embodiments. Accordingly, the inventions are not to be seen as limited by the foregoing description, but are only limited by the scope of the appended claims.
Number | Date | Country | Kind |
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3839/CHE/2013 | Aug 2013 | IN | national |