[go: up one dir, main page]

WO2025242962A1 - Gas analyser - Google Patents

Gas analyser

Info

Publication number
WO2025242962A1
WO2025242962A1 PCT/FI2025/050255 FI2025050255W WO2025242962A1 WO 2025242962 A1 WO2025242962 A1 WO 2025242962A1 FI 2025050255 W FI2025050255 W FI 2025050255W WO 2025242962 A1 WO2025242962 A1 WO 2025242962A1
Authority
WO
WIPO (PCT)
Prior art keywords
oil
extractor
measuring cell
gas
gases
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/FI2025/050255
Other languages
French (fr)
Inventor
Andrei SELIKHANOVICH
Ivan Afonin
Artem KLIMCHUK
Dmitrii LEGOSHIN
Mikhail BALANOV
Denis ANISIMOV
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mayak Oy
Original Assignee
Mayak Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from RU2024114207A external-priority patent/RU2823517C1/en
Application filed by Mayak Oy filed Critical Mayak Oy
Publication of WO2025242962A1 publication Critical patent/WO2025242962A1/en
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/03—Cuvette constructions
    • G01N21/031—Multipass arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G01N21/03—Cuvette constructions
    • G01N21/0332—Cuvette constructions with temperature control
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/26—Oils; Viscous liquids; Paints; Inks
    • G01N33/28—Oils, i.e. hydrocarbon liquids
    • G01N33/2835—Specific substances contained in the oils or fuels
    • G01N33/2841—Gas in oils, e.g. hydrogen in insulating oils
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/314—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths
    • G01N2021/3148—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry with comparison of measurements at specific and non-specific wavelengths using three or more wavelengths
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
    • G01N2021/396—Type of laser source
    • G01N2021/399—Diode laser
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/359—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using near infrared light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/08—Optical fibres; light guides
    • G01N2201/0826—Fibre array at source, distributing
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/12—Circuits of general importance; Signal processing
    • G01N2201/121—Correction signals
    • G01N2201/1218—Correction signals for pressure variations

Definitions

  • the invention relates to measuring equipment and may be used to measure the concentration of gases: hydrogen, oxygen, carbon oxide, carbon dioxide, methane, acetylene, ethylene, ethane (H2, 02, CO, C02, CH4, C2H2, C2H4, C2H6) dissolved in transformer oil.
  • the prior art discloses a detection platform for a spectral fiber-optic sensor, which comprises a transformer oil tank, an oil-gas separator, a gas-fiber detection device, a first oil transmission tube, a first oil drain valve, a second oil transmission tube, and a discharge valve.
  • Transformer oil is filtered through the oil-gas separator used to filter out the gas dissolved in the oil.
  • the gas is fed into the sensor chamber.
  • the wavelength of incident laser light is adjusted to provide the output spectrum of the incident laser light to anastomose with the spectral group of the detected gas.
  • the components of the detected gas transmission process are determined by measuring an incident light propagation coefficient and an emanating light width, and then the data processing results are applied to a Diptych terminal, and a station operator can see directly the transformer fault and aged condition (CN 109459411 A, 12.03.2019).
  • the detection of the platform for the spectral fiber-optic sensor can lead to online detection without stopping the transformer equipment, can accurately determine the content of the gas generated by the transformer fault and aging, and thus diagnose the transformer fault type and aging degree.
  • the prior art discloses a portable multi-component online monitor of gas dissolved in transformer oil, in which many semiconductor lasers are placed in a main chassis. Each semiconductor laser is coupled to a semiconductor laser controller, each semiconductor laser is coupled to a signal generation circuitry and a 1 *N photoswitch. The 1 *N photoswitch is coupled to an output fiber-optic connector in the main chassis.
  • the output fiber-optic connector is connected to a long-optical distance gas absorption cell via an output optical fiber.
  • the long-optical distance gas absorption cell is connected to an input optical fiber.
  • the other end of the input optical fiber is connected to an input fiber-optic connector in the main chassis.
  • the input fiber-optic connector is connected to a calibration absorption cell in the main chassis and a focusing lens, an infrared photodetector.
  • An amplifier coupler and a data acquisition control module are placed sequentially at the input light output of the calibration absorption cell (CN 103411920 A, 27.11.2013).
  • the need for safe transformer monitoring is satisfied, and a highly sensitive online real-time transformer failure monitoring is actually carried out.
  • the disadvantage of this device is a low measurement accuracy.
  • the technical result of the present invention is the development of a gas analyzer having an increased measurement accuracy due to a high selectivity of measurements of various gases at their sufficiently low concentrations and a low sensitivity to other substances dissolved in oil.
  • the described gas analyzer will allow one to create a greater variety of special purpose devices, i.e., gas analyzers for gases dissolved in oil.
  • a gas analyzer for gases dissolved in oil which comprises a housing accommodating: a control unit, a vacuum extractor for extraction of the gases from the oil via hydraulic lines for supplying the oil from a transformer into the extractor and discharging the oil from the extractor, and a measuring cell for measuring a concentration of the gases.
  • the measuring cell is connected to the extractor and made as a Herriott optical system for multiple passes of laser radiation from one mirror to another and measuring an output intensity of the laser radiation,
  • the measuring cell is connected to a laser module and a reference channel for laser wavelength calibration.
  • the laser module is configured to ensure operation of each of three lasers included therein at a certain wavelength to allow measurements of different gases in a gas mixture.
  • the reference channel includes a gasproof glass transparent container for the gas mixture, and a photodiode.
  • the mirrors of the measuring cell are provided with heaters, while the measuring cell includes warm-keeping elements.
  • the extractor is equipped with a pressure sensor and configured to be automatically calibrated using level sensors installed therein at different levels and by performing extraction at the different levels of the level sensors, with subsequent measurement of the concentration of the gases at the different levels and determination of a solubility factor of the gases.
  • Fig. 1 shows a general scheme of a gas analyzer
  • Fig. 2 shows a scheme of an extractor with its technological piping and instrumentation
  • Fig. 3 shows a measuring cell, on the input side of optical (laser) radiation
  • Fig. 4 shows the measuring cell, on the side of a radiation detector
  • Fig. 5 shows a design of a reference channel
  • Fig. 6 shows a design of a laser module
  • Fig. 7 shows an example of a signal in the reference channel.
  • a gas analyzer for gases dissolved in oil comprises a single housing 1 accommodating: a control unit 2 (or a motherboard), a vacuum extractor 3 for extraction of the gases from the oil, and a measuring cell 4 for measuring a concentration of the gases.
  • the measuring cell is connected to the extractor 3 and made as a Herriott optical system for multiple passage of laser radiation from one mirror to another and measuring its output intensity using a photodiode.
  • the measuring cell 4 connects with a laser module 5 and a reference channel 6 by means of a fiber-optic assembly 7.
  • the gas analyzer includes a set of sensors 8 for measuring hydrogen and oxygen (H2 and 02) by direct immersion in transformer oil.
  • the gases are extracted from the oil in the extractor 3 under low vacuum at 200-1000 Pa.
  • the extractor 3 with its technological piping and instrumentation (a hydraulic circuit with hydraulic lines) is shown in Fig. 2.
  • the extractor 3 is gas-proof and connects via two hydraulic lines 9 and 10 of the hydraulic circuit with a transformer: one for supplying the oil, and the other for discharging the oil, respectively.
  • the oil is delivered via an oil filter 11. Vacuum is created in the extractor 3 by lowering the oil level to that of a sensor 21.
  • the oil while moving and changing its level, operates as a piston pump.
  • the technological piping of the extractor 3 includes three-way valves 12 and 13, a nozzle 14 mounted in the upper part of the extractor 3, two-way valves 15, 16, 17, 18, a pump 19, a pressure sensor 20 in the extractor 3 , oil level sensors 21 , 22, 23 for different oil levels throughout the height of the extractor 3, and a membrane assembly 24.
  • the three-way valve 12 can be arranged on the line 9 or the valve 13, while the three-way valve 13 can be arranged on the line 10 or the nozzle 14.
  • the oil remaining in the extractor 3 after lowering the level and creating low pressure is sprayed under pressure through the nozzle 14.
  • the process is monitored by means of the pressure sensor 20 in the extractor 3.
  • the released gas phase is expelled by the oil into the measuring cell 4.
  • the hydraulic circuit of the extractor which is shown in Fig. 2 (in the scheme of the extractor 3 with its technological piping and instrumentation), ensures that all the tasks assigned to the extractor are performed: putting the device into operation, change of an oil sample, extraction of the gases from the oil, transfer of a gas sample into the measuring cell 4, evacuation of the gas sample from the measuring cell 4.
  • the extractor 3 is configured to be calibrated automatically by means of the level sensors 21, 22, 23 installed therein at different levels to perform extraction at the level of these sensors, with subsequent measurement of the gas concentration at these levels and determination of the gas solubility factor.
  • the membrane assembly 24 is installed between the extractor 3 and the measuring cell 4 and comprises a polytetrafluoroethylene (PTFE) membrane to prevent the oil aerosol from entering the measuring cell 4.
  • PTFE polytetrafluoroethylene
  • the measuring cell 4 (Figs. 3 and 4) is a multipass optical system designed according to the Herriott scheme.
  • the measuring cell 4 consists of a cell body 25, spacer rings 26 and 27, spherical mirrors
  • the spherical mirrors 28 and 29 are installed in the cell body 25.
  • the spacer rings 26 and 27 of a required thickness are provided between the mirrors and the cell.
  • the seals 32 and 33 are sealed by means of the O-ring seals 32 and 33.
  • the seals are unclamped by means of the flanges 34 and 35.
  • the heaters 36 and 37 are installed between the clamping flanges 38 and 39 and the mirrors 28 and 29. The heaters are pressed against the mirrors by the clamping flanges 38 and 39.
  • the aligning unit 40 with the collimator 41 is attached to one of the clamping flanges, while the receiver unit 42 to the other.
  • the membrane assembly 24 is installed between the extractor 3 and the measuring cell 4 and comprises the polytetrafluoroethylene (PTFE) membrane to prevent the oil aerosol from entering the measuring cell 4.
  • PTFE polytetrafluoroethylene
  • the laser module (Fig. 6) comprises three diode lasers 47, 48, 49 mounted on a printed circuit board 50, a milled housing 51 in thermal contact with the lasers 47, 48, 49 through a thermally conductive spacer 52, heat insulators 53 and 54, and an active thermostating Peltier element 55 in thermal contact with the milled housing 51 , a heat pipe 56 conducting heat from the housing 51 to the Peltier element 55, a cooler 57 designed to transfer heat from the hot side of the Peltier element 55.
  • the printed circuit board 50 includes laser pumping power sources, Peltier laser element drivers, temperature sensors, photodiode amplifiers (not shown in the drawings) of the measuring cell and the reference channel.
  • the fiber-optic assembly (designated as “7” in Fig. 1) is designed to bring the radiation of the three lasers in a single fiber and connect through two outputs to the measuring cell 4 and to the reference channel through a ring resonator (not shown in the drawings).
  • the ring resonator output is connected to the reference channel 6.
  • the three diode lasers 47, 48, 49 and temperature sensitive electronics are in the laser module 5.
  • the laser module 5 is configured to ensure the operation of each of the three lasers 47, 48, 49 included therein at a specific wavelength to provide measurements of different gases of the gas mixture.
  • the laser wavelength is controlled by changing the laser pumping current from 0 to 120 mA within 1 ms. Due to a change in the pumping current, the wave number changes within 3- 5 cm 1 .
  • the diode laser temperature is kept constant by means of a thermistor (not shown in the drawings) and the Peltier element 55 which are in the laser housing.
  • the laser module 5 is thermally insulated by the heat insulators 53 and 54 and is actively thermostated using the Peltier element 55.
  • H2 and 02 are measured by the set of sensors 8 directly in the oil without extracting the gas phase.
  • H2 is measured using a solid-state Pd structure-based sensor.
  • 02 is measured, for example, by a sensor immersed in the oil and operating on the fluorescence quenching principle.
  • the laser diode temperature is selected so that the laser wavelength changes within the absorption line of the gas under study when changing the pumping current.
  • one laser is used to measure C2H2 at a wavelength of 1532 nm
  • the other laser is used to perform simultaneous measurement of CO and CO2 at a wavelength of 1580 nm
  • the third laser is used to perform simultaneous measurement of CH4, C2H4, C2H6 at a wavelength of 1680 nm.
  • the measurement is performed according to the following cycle scheme:
  • each measurement of each spectral channel includes measuring the absorption spectrum in the reference channel 6 and the measurement cell 4.
  • the temperatures of the three lasers and of the laser printed circuit board are kept constant by means of PID controllers.
  • the functions of the laser module 5 include:
  • the laser radiation enters the optical system of the measuring cell 4 through a slot in the gold-flashed spherical mirror 28, makes 73 passes from the mirror 28 to the mirror 29 and exits through a slot in the opposite gold-flashed mirror 29.
  • the output intensity of the laser radiation that has passed through the measuring cell 4 is measured by a photodiode (not shown in the drawings).
  • the laser radiation absorption is a gas concentration value. Different gases absorb different wavelength radiations.
  • the measuring cell 4 is gas-proof and connected to the extractor
  • the measuring cell 4 is connected to the laser module 5 by means of an optical fiber.
  • the reference channel 6 includes a gas-proof glass transparent container 58 for the gas mixture, an optical socket 59 for radiation input and a photodiode 60.
  • the reference channel 6 records any changes due to degradation of the electronics/laser or as a result of the electronics/laser temperature drifts.
  • the changes will be registered in the reference channel 6 and taken into account when processing the spectra of the measurement cell 4.
  • the measuring part of the device is calibrated. In this case, the calibration is carried out at every measurement stage.
  • the mirrors 28 and 29 are equipped with the heaters 36 and 37, and the measuring cell 4 itself is provided with the insulating elements 45 and 46.
  • the gas analyzer operates as follows.
  • the container of the extractor 3 and the measuring cell 4 are filled with dry nitrogen.
  • the container of the extractor 3 is filled gradually with the extractor valve 18 open to the atmosphere through all the hydraulic lines.
  • the gas is filled up to the level sensor 23. In this way, the air from the extractor 3 is forced out into the atmosphere through the valve 18.
  • valve 18 is then closed, and the valve 17 installed at the inlet of the measuring cell 4 is opened.
  • the oil level in the container of the extractor 3 is lowered to the level sensor 21 by the pump 19 via the valves 12 and 13 (position to the line 10).
  • the valve 17 is closed, and the valve 18 is opened.
  • the container of the extractor 3 is filled with oil through the valve 15.
  • the part of the nitrogen transferred from the measuring cell 4 into the container of the extractor 3 is emitted into the atmosphere under the oil pressure.
  • the gas extraction stage starts with refreshing the oil sample in the container of the extractor 3.
  • the fresh oil sample is taken using the pump 19 through the valves 16, 12 (position to the valve 13) and 13 (position to the line 10) at the constant oil level corresponding to the position of the sensor 23.
  • the container of the extractor 3 is specially shaped to minimize dead volumes when pumping the oil through the container of the extractor 3.
  • the oil level is then lowered to a level corresponding to the position of the level sensor 21 using the pump 19 through the valves 12 (position to the valve 13) and 13 (position to the line 10).
  • a low pressure of about 200-1000 Pa is generated in the container of the extractor 3.
  • the oil remaining in the container of the extractor 3 is further pumped through the nozzle 14 by using the pump 19 through the valves 12 and 13.
  • the nozzle 14 breaks the oil into small droplets, from which surface the oil is degassed.
  • the pressure in the container of the extractor 3 rises.
  • the pressure is monitored by means of the pressure sensor 20.
  • the extraction ends when the pressure stops rising inside the container of the extractor 3.
  • the pressure change during the extraction is proportional to the total gas content (TGC) in the oil and is used for its calculation.
  • TGC total gas content
  • Gases are extracted from the oil in the extractor 3 under low vacuum (200-1000 Pa).
  • the extractor 3 is gas-proof and connects via the two hydraulic lines 9 and 10 with the transformer: one for supplying the oil, and the other for discharging the oil.
  • the vacuum is created in the container of the extractor 3 by lowering the oil level.
  • the oil operates as a piston pump.
  • the oil remaining in the extractor 3 is sprayed under pressure through the nozzle 14. The process is monitored by means of the pressure sensor 20.
  • the released gas phase is expelled by the oil into the measuring cell 4.
  • the pressure in the container of the extractor 3 increases. As soon as the pressure in the container of the extractor 3 exceeds the pressure of the measuring cell 4 (the measuring cell includes the pressure sensor 44), the valve 17 opens. In this way, the gas flows from the extractor 3 to the measuring cell 4.
  • the pressure in the container of the extractor 3 and the measuring cell 4 continues increasing either until the set pressure in the measuring cell 4 is reached or until the oil reaches the level of the level sensor 23. If the set pressure is not reached in the measuring cell 4, the extractor 3 repeats the extraction procedure and transfers the gas sample to the measuring cell 4.
  • the device cyclogram provides for different set pressures in the measuring cell 4. The set pressure is determined based on the pressure rise during the first extraction. The set pressures are determined so as to ensure measurement of oil-dissolved gases within 0. l%-10% TGC. In the worst case, the number of extractions is not more than three.
  • the extracted gas should be transferred as carefully as possible into the measuring cell 4.
  • the oil that pushes out the gas must not be accidentally degassed when filling up the container of the extractor 3, so the gas is pushed out into the measuring cell 4 not by means of the pump 19, which can lead to turbulent flows, but by the transformer hydrostatic pressure through the open valve 15 through a thin 50-100 cm tube (not shown in the drawings).
  • the valve 12 is positioned to the valve 13.
  • the measuring cell 4 is a Herriott-based multipass optical system connected to the laser module 5 provided with the fiber-optic assembly 7.
  • the laser radiation enters the optical system through the slot (not shown in the drawings) in the gold-flashed spherical mirror, makes 73 passes from one mirror to the other and exits through the split (not shown in the drawings) in the opposite gold-flashed mirror.
  • the output intensity of the laser radiation that has passed through the measuring cell 4 is measured by the photodiode.
  • R is the radius of curvature of the mirrors
  • a is the angle of the beam rotation, which must fulfill the condition:
  • the measuring cell design ensures the selection of values of m and n such that the adjacent laser radiation scattering spots correspond to the number of passes greater than 20.
  • the frequency of interference which may occur due to the system misalignment or contamination of the mirrors, is 0.00066 cm 1 .
  • This interference frequency is more than an order of magnitude smaller than the typical absorption line width. Therefore, the occurrence of this noise component will not affect the absorption signal processing and will not result in the degradation of accuracy and sensitivity.
  • the gas sample After the measuring procedure, the gas sample must be evacuated from the measuring cell 4.
  • the oil level in the container of the extractor 3 is then lowered to the level of the level sensor 21 using the pump 19 through the valves 12 (position to the valve 13) and 13 (position to the line 10).
  • the pressure in the container of the extractor 3 becomes less than that in the measuring cell 4.
  • the oil level in the container of the extractor 3 is lowered to the level of the level sensor 21 by means of the pump 19 through the valves 12 (position to the valve 13) and 13 (position to the line 10).
  • the valve 17 is closed.
  • the gas sample partially evacuated from the measuring cell 4 is dissolved back into the oil.
  • the dissolution is as follows.
  • the pump 19 pumps the oil into the container of the extractor 3 through the valve 12 (position to the line 9) either up to the level of the level sensor 23 or until the pressure reaches 1700-2000 hPa, whichever comes first.
  • the pump 19 pumps the oil from the container of the extractor 3 through the nozzle 14 through the valve 12 (position to the valve 13) and the valve 13 (position to the nozzle 14).
  • the pressure changes during this process are registered by the pressure sensor 20. What used to result in degassing of the oil, under these operating conditions of the extractor 3, results in the dissolution of gases back into the oil.
  • the process is completed when the pressure in the container of the extractor 3 stops dropping.
  • the pump 19 pumps the oil into the container of the extractor 3 either up to the level of the level sensor 23 or until the pressure reaches 1700-2000 hPa, whichever comes first.
  • the dissolution process repeats.
  • the oil level in the container of the extractor 3 reaches the level of the level sensor 23. Thereafter, the oil sample in the container of the extractor 3 is renewed in accordance with the above-described procedure.
  • the pressure therein can become insufficiently low as compared to the set pressure.
  • the gas sample evacuation procedure may be repeated once or twice.
  • the residual pressure in the measuring cell 4 does not exceed 20% of the set pressure. In this way, a sufficient exchange of the gas sample in the measuring cell 4 is ensured. This is to ensure that the previous gas sample has as little influence as possible on the new measuring cycle.
  • oil solubility factors shall be determined at the laboratory, or each device shall be calibrated on the transformer on which it is installed.
  • the calibration of the device which involves determining the solubility factors of the gases in the oil, is performed automatically when the device is put into operation or during operation.
  • V gas is the gas volume
  • V oil is the oil volume
  • k l is the i-th component solubility factor.
  • This peculiarity is used in the automatic calibration of the device during the gas extraction for both the oil at the level of the level sensor 23 (as described earlier) and the oil at the level of the level sensor 22. Since the extraction efficiency in the two cases is different, there will be different gas concentrations in the measuring cell 4.
  • the solubility factor for each measured gas can be determined by the formula: where , C 2 are the measured concentrations of the i-th component for different levels, Vj 01 , g as phase volumes for different levels.
  • the level sensor 22 is used during the device calibration.
  • the laser radiation is fed into the working volume of the measuring cell 4 by means of the fiber collimator 41.
  • the required input angle is set manually using the aligning unit 40. Alignment is performed according to the three-point setting. The adjustment is carried out by selecting the free length of the three screws. The adjustment can be done by visual inspection of the laser radiation visible spectrum. For this purpose, a central sight glass (not shown in the drawings) is provided in the reflecting coating of the mirrors 28, 29. After the adjustment, the aligning unit 40 is fixed by the three locking screws.
  • the radiation is additionally deflected by means of the optical wedges 30 and 31 both at the input and output of the measuring cell 4. The radiation passes through the mirror substrate through a special slot in the mirror reflecting coating. A similar slot in the reflecting coating is used for the radiation exit from the cell.
  • the radiation is fed into the receiver unit 42, where the laser radiation power is registered. By means of the heaters 36, 37, the required temperature is set in the measuring cell 4.
  • the insulating elements 45 and 46 are used to ensure thermal conditioning.
  • the function of the reference channel 6 is that the effects of any changes caused by the degradation of the electronics/laser or by the electronics/laser temperature drifts will be recorded in the reference channel 6 and taken into account when processing the spectra of the measuring cell 4. In this way, the measuring part of the device is calibrated also. In this case, the calibration is carried out at every measurement stage.
  • the optical input of the reference channel 6 is connected to the optical output of the ring resonator.
  • the signal of the reference channel 6 may be, for example, like the one shown in Fig. 7.
  • Absorption lines in this case methane lines, can be seen in the signal of the reference channel. Besides, the interference pattern of the ring resonator included in the fiber-optic assembly 7 is visible.
  • the signal processing algorithm of the reference channel 6 makes it possible to determine both the centers of the absorption line and the centers of the interference pattern features.
  • the diode laser re-tuning is not linear in time, which is clearly seen in the signal of the reference channel. In reciprocal centimeters, the distance between adjacent peaks of the interference pattern is equidistant and corresponds to the free dispersion region of the ring resonator. This feature is used by the algorithm to switch from the signal time scale to the reciprocal centimeter scale.
  • the features of the interference pattern serve for relative calibration of the frequency scale
  • the centers of the absorption lines serve for absolute calibration of the scale.
  • the control unit (or motherboard) of the gas analyzer controls the following:
  • control unit is used also to store data.
  • the main measurement interface of a software menu is displayed on a PC monitor (not shown in the drawings), which shows, for example:
  • the gas analyzer makes it possible to detect the lowest gas contents - 1 ppm for C2H4, C2H6, 0.5 ppm for CH4, 0.05 ppm for C2H2, and 10 ppm for CO and CO2, - due to the long optical length and vacuum extraction.
  • the selective laser spectroscopy and correctly selected wavelengths ensure low crosssensitivity of measured gases to each other and to a wide range of substances dissolved in the transformer oil.
  • the self-calibration of the extractor leads to a higher accuracy class, independent of the transformer oil, in terms of determining the solubility factors of gases in the oil.
  • the invention will make it possible to increase the accuracy of measurements due to a high selectivity of measurements of various gases at their sufficiently low concentrations and a low sensitivity to other substances dissolved in the oil.
  • the described gas analyzer will allow one to create a greater variety of special purpose devices, i.e., gas analyzers for gasses dissolved in oil.

Landscapes

  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Engineering & Computer Science (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Optics & Photonics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Food Science & Technology (AREA)
  • Medicinal Chemistry (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

The invention relates to measuring equipment and may be used to measure the concentration of gases: hydrogen, oxygen, carbon oxide, carbon dioxide, methane, acetylene, ethylene, ethane (H2, О2, CO, CO2, CH4, C2H2, C2H4, C2H6) dissolved in transformer oil. A gas analyzer for gases dissolved in oil comprises a housing accommodating: a control unit, a vacuum extractor for extraction of the gases from the oil via hydraulic lines for supplying the oil from a transformer into the extractor and its discharge, a measuring cell for measuring the concentration of the gases. The measuring cell is connected to the extractor and made as a Herriott optical system for multiple passage of laser radiation from one mirror to another and measuring its output intensity using a photodiode. The measuring cell is connected to a laser module and a reference channel for laser wavelength calibration. There is a membrane assembly installed between the extractor and the measuring cell to prevent the oil from entering the measuring cell. The laser module is configured to ensure operation of each of its three lasers at a certain wavelength to allow measurements of different gases in the gas mixture. The reference channel includes a gas-proof glass transparent container for the gas mixture, and a photodiode. The measuring cell mirrors are provided with heaters and insulations, while the extractor can be calibrated automatically by means of pressure sensors installed in it at different levels to perform extraction at the level of these sensors, with subsequent measurement of gas concentrations at these levels and determination of the gas solubility. The invention will make it possible to improve measuring accuracy.

Description

GAS ANALYSER
TECHNICAL FIELD OF THE INVENTION
The invention relates to measuring equipment and may be used to measure the concentration of gases: hydrogen, oxygen, carbon oxide, carbon dioxide, methane, acetylene, ethylene, ethane (H2, 02, CO, C02, CH4, C2H2, C2H4, C2H6) dissolved in transformer oil.
BACKGROUND
The prior art discloses a detection platform for a spectral fiber-optic sensor, which comprises a transformer oil tank, an oil-gas separator, a gas-fiber detection device, a first oil transmission tube, a first oil drain valve, a second oil transmission tube, and a discharge valve. Transformer oil is filtered through the oil-gas separator used to filter out the gas dissolved in the oil. Then, the gas is fed into the sensor chamber. The wavelength of incident laser light is adjusted to provide the output spectrum of the incident laser light to anastomose with the spectral group of the detected gas. The components of the detected gas transmission process are determined by measuring an incident light propagation coefficient and an emanating light width, and then the data processing results are applied to a Diptych terminal, and a station operator can see directly the transformer fault and aged condition (CN 109459411 A, 12.03.2019).
The detection of the platform for the spectral fiber-optic sensor can lead to online detection without stopping the transformer equipment, can accurately determine the content of the gas generated by the transformer fault and aging, and thus diagnose the transformer fault type and aging degree.
The prior art discloses a portable multi-component online monitor of gas dissolved in transformer oil, in which many semiconductor lasers are placed in a main chassis. Each semiconductor laser is coupled to a semiconductor laser controller, each semiconductor laser is coupled to a signal generation circuitry and a 1 *N photoswitch. The 1 *N photoswitch is coupled to an output fiber-optic connector in the main chassis. The output fiber-optic connector is connected to a long-optical distance gas absorption cell via an output optical fiber. The long-optical distance gas absorption cell is connected to an input optical fiber. The other end of the input optical fiber is connected to an input fiber-optic connector in the main chassis. The input fiber-optic connector is connected to a calibration absorption cell in the main chassis and a focusing lens, an infrared photodetector. An amplifier coupler and a data acquisition control module are placed sequentially at the input light output of the calibration absorption cell (CN 103411920 A, 27.11.2013).
According to the portable multi-component online monitor, the need for safe transformer monitoring is satisfied, and a highly sensitive online real-time transformer failure monitoring is actually carried out.
The disadvantage of this device is a low measurement accuracy.
SUMMARY OF THE INVENTION
The technical result of the present invention is the development of a gas analyzer having an increased measurement accuracy due to a high selectivity of measurements of various gases at their sufficiently low concentrations and a low sensitivity to other substances dissolved in oil.
The described gas analyzer will allow one to create a greater variety of special purpose devices, i.e., gas analyzers for gases dissolved in oil.
The specified technical result is achieved in a gas analyzer for gases dissolved in oil, which comprises a housing accommodating: a control unit, a vacuum extractor for extraction of the gases from the oil via hydraulic lines for supplying the oil from a transformer into the extractor and discharging the oil from the extractor, and a measuring cell for measuring a concentration of the gases. The measuring cell is connected to the extractor and made as a Herriott optical system for multiple passes of laser radiation from one mirror to another and measuring an output intensity of the laser radiation, The measuring cell is connected to a laser module and a reference channel for laser wavelength calibration. There is a membrane assembly installed between the extractor and the measuring cell to prevent the oil from entering the measuring cell. The laser module is configured to ensure operation of each of three lasers included therein at a certain wavelength to allow measurements of different gases in a gas mixture. The reference channel includes a gasproof glass transparent container for the gas mixture, and a photodiode. The mirrors of the measuring cell are provided with heaters, while the measuring cell includes warm-keeping elements. The extractor is equipped with a pressure sensor and configured to be automatically calibrated using level sensors installed therein at different levels and by performing extraction at the different levels of the level sensors, with subsequent measurement of the concentration of the gases at the different levels and determination of a solubility factor of the gases.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by drawings, in which:
Fig. 1 shows a general scheme of a gas analyzer; Fig. 2 shows a scheme of an extractor with its technological piping and instrumentation;
Fig. 3 shows a measuring cell, on the input side of optical (laser) radiation;
Fig. 4 shows the measuring cell, on the side of a radiation detector;
Fig. 5 shows a design of a reference channel;
Fig. 6 shows a design of a laser module;
Fig. 7 shows an example of a signal in the reference channel.
DETAILED DESCRIPTION
A gas analyzer for gases dissolved in oil comprises a single housing 1 accommodating: a control unit 2 (or a motherboard), a vacuum extractor 3 for extraction of the gases from the oil, and a measuring cell 4 for measuring a concentration of the gases. The measuring cell is connected to the extractor 3 and made as a Herriott optical system for multiple passage of laser radiation from one mirror to another and measuring its output intensity using a photodiode.
The measuring cell 4 connects with a laser module 5 and a reference channel 6 by means of a fiber-optic assembly 7.
Besides, the gas analyzer includes a set of sensors 8 for measuring hydrogen and oxygen (H2 and 02) by direct immersion in transformer oil.
The gases are extracted from the oil in the extractor 3 under low vacuum at 200-1000 Pa.
The extractor 3 with its technological piping and instrumentation (a hydraulic circuit with hydraulic lines) is shown in Fig. 2.
The extractor 3 is gas-proof and connects via two hydraulic lines 9 and 10 of the hydraulic circuit with a transformer: one for supplying the oil, and the other for discharging the oil, respectively. The oil is delivered via an oil filter 11. Vacuum is created in the extractor 3 by lowering the oil level to that of a sensor 21. The oil, while moving and changing its level, operates as a piston pump.
Besides, the technological piping of the extractor 3 includes three-way valves 12 and 13, a nozzle 14 mounted in the upper part of the extractor 3, two-way valves 15, 16, 17, 18, a pump 19, a pressure sensor 20 in the extractor 3 , oil level sensors 21 , 22, 23 for different oil levels throughout the height of the extractor 3, and a membrane assembly 24. The three-way valve 12 can be arranged on the line 9 or the valve 13, while the three-way valve 13 can be arranged on the line 10 or the nozzle 14.
To accelerate degassing, the oil remaining in the extractor 3 after lowering the level and creating low pressure is sprayed under pressure through the nozzle 14. The process is monitored by means of the pressure sensor 20 in the extractor 3. The released gas phase is expelled by the oil into the measuring cell 4. The hydraulic circuit of the extractor, which is shown in Fig. 2 (in the scheme of the extractor 3 with its technological piping and instrumentation), ensures that all the tasks assigned to the extractor are performed: putting the device into operation, change of an oil sample, extraction of the gases from the oil, transfer of a gas sample into the measuring cell 4, evacuation of the gas sample from the measuring cell 4.
The extractor 3 is configured to be calibrated automatically by means of the level sensors 21, 22, 23 installed therein at different levels to perform extraction at the level of these sensors, with subsequent measurement of the gas concentration at these levels and determination of the gas solubility factor.
The membrane assembly 24 is installed between the extractor 3 and the measuring cell 4 and comprises a polytetrafluoroethylene (PTFE) membrane to prevent the oil aerosol from entering the measuring cell 4.
The measuring cell 4 (Figs. 3 and 4) is a multipass optical system designed according to the Herriott scheme.
The measuring cell 4 consists of a cell body 25, spacer rings 26 and 27, spherical mirrors
28 and 29, optical wedges 30 and 31, seals 32 and 33, seal unclamping flanges 34 and 35, heaters 36 and 37, clamping flanges 38 and 39, an aligning unit 40, an optical collimator 41, a receiver unit 42, a union 43 for connection to the extractor 3, a pressure sensor 44 and insulating elements 45 and 46. The spherical mirrors 28 and 29 are installed in the cell body 25. The spacer rings 26 and 27 of a required thickness are provided between the mirrors and the cell. The mirrors 28 and
29 are sealed by means of the O-ring seals 32 and 33. The seals are unclamped by means of the flanges 34 and 35. The heaters 36 and 37 are installed between the clamping flanges 38 and 39 and the mirrors 28 and 29. The heaters are pressed against the mirrors by the clamping flanges 38 and 39. The aligning unit 40 with the collimator 41 is attached to one of the clamping flanges, while the receiver unit 42 to the other.
The membrane assembly 24 is installed between the extractor 3 and the measuring cell 4 and comprises the polytetrafluoroethylene (PTFE) membrane to prevent the oil aerosol from entering the measuring cell 4.
The laser module (Fig. 6) comprises three diode lasers 47, 48, 49 mounted on a printed circuit board 50, a milled housing 51 in thermal contact with the lasers 47, 48, 49 through a thermally conductive spacer 52, heat insulators 53 and 54, and an active thermostating Peltier element 55 in thermal contact with the milled housing 51 , a heat pipe 56 conducting heat from the housing 51 to the Peltier element 55, a cooler 57 designed to transfer heat from the hot side of the Peltier element 55. The printed circuit board 50 includes laser pumping power sources, Peltier laser element drivers, temperature sensors, photodiode amplifiers (not shown in the drawings) of the measuring cell and the reference channel.
The fiber-optic assembly (designated as “7” in Fig. 1) is designed to bring the radiation of the three lasers in a single fiber and connect through two outputs to the measuring cell 4 and to the reference channel through a ring resonator (not shown in the drawings). The ring resonator output is connected to the reference channel 6.
The three diode lasers 47, 48, 49 and temperature sensitive electronics are in the laser module 5. The laser module 5 is configured to ensure the operation of each of the three lasers 47, 48, 49 included therein at a specific wavelength to provide measurements of different gases of the gas mixture.
The laser wavelength is controlled by changing the laser pumping current from 0 to 120 mA within 1 ms. Due to a change in the pumping current, the wave number changes within 3- 5 cm 1. The diode laser temperature is kept constant by means of a thermistor (not shown in the drawings) and the Peltier element 55 which are in the laser housing. The laser module 5 is thermally insulated by the heat insulators 53 and 54 and is actively thermostated using the Peltier element 55.
CO, CO2, CH4, CH4, C2H2, C2H4, C2H6 are measured by laser absorption spectroscopy. H2 and 02 are measured by the set of sensors 8 directly in the oil without extracting the gas phase. H2 is measured using a solid-state Pd structure-based sensor. 02 is measured, for example, by a sensor immersed in the oil and operating on the fluorescence quenching principle.
The laser diode temperature is selected so that the laser wavelength changes within the absorption line of the gas under study when changing the pumping current. In this case, one laser is used to measure C2H2 at a wavelength of 1532 nm, the other laser is used to perform simultaneous measurement of CO and CO2 at a wavelength of 1580 nm, and the third laser is used to perform simultaneous measurement of CH4, C2H4, C2H6 at a wavelength of 1680 nm.
The measurement is performed according to the following cycle scheme:
- the 1532 nm laser switches on to measure C2H2;
- the laser reaches the thermal mode within 5 minutes;
- the absorption spectrum in the 1532 nm reference channel is registered;
- the absorption spectrum in the 1532 nm measuring cell is registered;
- the laser switches off.
The above-described steps are repeated for the two remaining lasers: to measure CO and CO2 at 1580 nm and to measure CH4, C2H4, C2H6 at 1680 nm. Thus, each measurement of each spectral channel includes measuring the absorption spectrum in the reference channel 6 and the measurement cell 4. In this case, the temperatures of the three lasers and of the laser printed circuit board are kept constant by means of PID controllers.
The functions of the laser module 5 include:
- controlling the diode laser wavelength;
- controlling the diode laser temperature;
- controlling the PCB temperature;
- outputting the radiation to the measuring cell and the reference channel.
The laser radiation enters the optical system of the measuring cell 4 through a slot in the gold-flashed spherical mirror 28, makes 73 passes from the mirror 28 to the mirror 29 and exits through a slot in the opposite gold-flashed mirror 29. The output intensity of the laser radiation that has passed through the measuring cell 4 is measured by a photodiode (not shown in the drawings). The laser radiation absorption is a gas concentration value. Different gases absorb different wavelength radiations. The measuring cell 4 is gas-proof and connected to the extractor
3 by a tube. The measuring cell 4 is connected to the laser module 5 by means of an optical fiber.
The reference channel 6 includes a gas-proof glass transparent container 58 for the gas mixture, an optical socket 59 for radiation input and a photodiode 60.
The reference channel 6 records any changes due to degradation of the electronics/laser or as a result of the electronics/laser temperature drifts. The changes will be registered in the reference channel 6 and taken into account when processing the spectra of the measurement cell 4. In this way, the measuring part of the device is calibrated. In this case, the calibration is carried out at every measurement stage.
The mirrors 28 and 29 are equipped with the heaters 36 and 37, and the measuring cell 4 itself is provided with the insulating elements 45 and 46.
The gas analyzer operates as follows.
When the device is installed, the container of the extractor 3 and the measuring cell 4 are filled with dry nitrogen. During the first connection to the transformer, the container of the extractor 3 is filled gradually with the extractor valve 18 open to the atmosphere through all the hydraulic lines. The gas is filled up to the level sensor 23. In this way, the air from the extractor 3 is forced out into the atmosphere through the valve 18.
The valve 18 is then closed, and the valve 17 installed at the inlet of the measuring cell 4 is opened. The oil level in the container of the extractor 3 is lowered to the level sensor 21 by the pump 19 via the valves 12 and 13 (position to the line 10). Thus, the pressure in the measuring cell
4 drops. The valve 17 is closed, and the valve 18 is opened. The container of the extractor 3 is filled with oil through the valve 15. The part of the nitrogen transferred from the measuring cell 4 into the container of the extractor 3 is emitted into the atmosphere under the oil pressure.
Pumping the nitrogen out of the measuring cell 4 when putting into operation can be repeated 3-4 times. Putting into operation is completed when the oil level reaches the respective position of the level sensor 23.
The gas extraction stage starts with refreshing the oil sample in the container of the extractor 3. The fresh oil sample is taken using the pump 19 through the valves 16, 12 (position to the valve 13) and 13 (position to the line 10) at the constant oil level corresponding to the position of the sensor 23. The container of the extractor 3 is specially shaped to minimize dead volumes when pumping the oil through the container of the extractor 3.
The oil level is then lowered to a level corresponding to the position of the level sensor 21 using the pump 19 through the valves 12 (position to the valve 13) and 13 (position to the line 10). In this way, a low pressure of about 200-1000 Pa is generated in the container of the extractor 3. The oil remaining in the container of the extractor 3 is further pumped through the nozzle 14 by using the pump 19 through the valves 12 and 13. The nozzle 14 breaks the oil into small droplets, from which surface the oil is degassed. During this process, the pressure in the container of the extractor 3 rises. The pressure is monitored by means of the pressure sensor 20. The extraction ends when the pressure stops rising inside the container of the extractor 3. The pressure change during the extraction is proportional to the total gas content (TGC) in the oil and is used for its calculation.
Gases are extracted from the oil in the extractor 3 under low vacuum (200-1000 Pa). The extractor 3 is gas-proof and connects via the two hydraulic lines 9 and 10 with the transformer: one for supplying the oil, and the other for discharging the oil. The vacuum is created in the container of the extractor 3 by lowering the oil level. The oil operates as a piston pump. To accelerate degassing, the oil remaining in the extractor 3 is sprayed under pressure through the nozzle 14. The process is monitored by means of the pressure sensor 20. The released gas phase is expelled by the oil into the measuring cell 4.
As the oil level rises, the pressure in the container of the extractor 3 increases. As soon as the pressure in the container of the extractor 3 exceeds the pressure of the measuring cell 4 (the measuring cell includes the pressure sensor 44), the valve 17 opens. In this way, the gas flows from the extractor 3 to the measuring cell 4.
The pressure in the container of the extractor 3 and the measuring cell 4 continues increasing either until the set pressure in the measuring cell 4 is reached or until the oil reaches the level of the level sensor 23. If the set pressure is not reached in the measuring cell 4, the extractor 3 repeats the extraction procedure and transfers the gas sample to the measuring cell 4. The device cyclogram provides for different set pressures in the measuring cell 4. The set pressure is determined based on the pressure rise during the first extraction. The set pressures are determined so as to ensure measurement of oil-dissolved gases within 0. l%-10% TGC. In the worst case, the number of extractions is not more than three.
The extracted gas should be transferred as carefully as possible into the measuring cell 4. The oil that pushes out the gas must not be accidentally degassed when filling up the container of the extractor 3, so the gas is pushed out into the measuring cell 4 not by means of the pump 19, which can lead to turbulent flows, but by the transformer hydrostatic pressure through the open valve 15 through a thin 50-100 cm tube (not shown in the drawings). In this case, the valve 12 is positioned to the valve 13.
The measuring cell 4 is a Herriott-based multipass optical system connected to the laser module 5 provided with the fiber-optic assembly 7. The laser radiation enters the optical system through the slot (not shown in the drawings) in the gold-flashed spherical mirror, makes 73 passes from one mirror to the other and exits through the split (not shown in the drawings) in the opposite gold-flashed mirror. The output intensity of the laser radiation that has passed through the measuring cell 4 is measured by the photodiode. The basic formula describing the Herriott system is as follows: cos a =1-L/R, where L is the distance between the mirrors,
R is the radius of curvature of the mirrors, a is the angle of the beam rotation, which must fulfill the condition:
2ma = 2rur, where m and n are natural numbers.
The measuring cell design ensures the selection of values of m and n such that the adjacent laser radiation scattering spots correspond to the number of passes greater than 20.
The frequency of interference, which may occur due to the system misalignment or contamination of the mirrors, is 0.00066 cm 1. This interference frequency is more than an order of magnitude smaller than the typical absorption line width. Therefore, the occurrence of this noise component will not affect the absorption signal processing and will not result in the degradation of accuracy and sensitivity.
After the measuring procedure, the gas sample must be evacuated from the measuring cell 4. The oil level in the container of the extractor 3 is then lowered to the level of the level sensor 21 using the pump 19 through the valves 12 (position to the valve 13) and 13 (position to the line 10). The pressure in the container of the extractor 3 becomes less than that in the measuring cell 4. For this purpose, the oil level in the container of the extractor 3 is lowered to the level of the level sensor 21 by means of the pump 19 through the valves 12 (position to the valve 13) and 13 (position to the line 10). The valve 17 is closed.
The gas sample partially evacuated from the measuring cell 4 is dissolved back into the oil. The dissolution is as follows. The pump 19 pumps the oil into the container of the extractor 3 through the valve 12 (position to the line 9) either up to the level of the level sensor 23 or until the pressure reaches 1700-2000 hPa, whichever comes first. Then, the pump 19 pumps the oil from the container of the extractor 3 through the nozzle 14 through the valve 12 (position to the valve 13) and the valve 13 (position to the nozzle 14). The pressure changes during this process are registered by the pressure sensor 20. What used to result in degassing of the oil, under these operating conditions of the extractor 3, results in the dissolution of gases back into the oil. The process is completed when the pressure in the container of the extractor 3 stops dropping. If the oil does not reach the level of the level sensor 23, the pump 19 pumps the oil into the container of the extractor 3 either up to the level of the level sensor 23 or until the pressure reaches 1700-2000 hPa, whichever comes first. The dissolution process repeats.
Thus, in several iterations, the oil level in the container of the extractor 3 reaches the level of the level sensor 23. Thereafter, the oil sample in the container of the extractor 3 is renewed in accordance with the above-described procedure. In one described cycle of the sample evacuation from the measuring cell 4, the pressure therein can become insufficiently low as compared to the set pressure. In this case, the gas sample evacuation procedure may be repeated once or twice. In the worst case, the residual pressure in the measuring cell 4 does not exceed 20% of the set pressure. In this way, a sufficient exchange of the gas sample in the measuring cell 4 is ensured. This is to ensure that the previous gas sample has as little influence as possible on the new measuring cycle.
To ensure reproducibility of the results, proper conditions for temperature stabilization are created in the container of the extractor 3. For this purpose, six heaters (not shown in the drawings) are installed on the container of the extractor 3 to stabilize the temperature in the container of the extractor 3 to about 45° C.
Since the transformers may be filled with unknown mixtures of oils, oil solubility factors shall be determined at the laboratory, or each device shall be calibrated on the transformer on which it is installed. The calibration of the device, which involves determining the solubility factors of the gases in the oil, is performed automatically when the device is put into operation or during operation.
There is a certain relationship between the concentration of the gases in the oil and their concentration in the gas phase after the extraction procedure. This relationship depends on the gasin-oil solubility factors. These factors depend on the type of oil. The degassing efficiency Et of the i -th component depends not only on the solubility factors, but also on the ratio of the oil volume/free volume above the oil during extraction.
1 Ei = - y— l + kl gas
Vgas is the gas volume,
Voil is the oil volume, kl is the i-th component solubility factor.
This peculiarity is used in the automatic calibration of the device during the gas extraction for both the oil at the level of the level sensor 23 (as described earlier) and the oil at the level of the level sensor 22. Since the extraction efficiency in the two cases is different, there will be different gas concentrations in the measuring cell 4.
Assuming that the concentration of the gases in the oil has not changed during this process, the solubility factor for each measured gas can be determined by the formula: where , C2 are the measured concentrations of the i-th component for different levels, Vj01 , gas phase volumes for different levels.
So, the level sensor 22 is used during the device calibration.
The laser radiation is fed into the working volume of the measuring cell 4 by means of the fiber collimator 41. The required input angle is set manually using the aligning unit 40. Alignment is performed according to the three-point setting. The adjustment is carried out by selecting the free length of the three screws. The adjustment can be done by visual inspection of the laser radiation visible spectrum. For this purpose, a central sight glass (not shown in the drawings) is provided in the reflecting coating of the mirrors 28, 29. After the adjustment, the aligning unit 40 is fixed by the three locking screws. The radiation is additionally deflected by means of the optical wedges 30 and 31 both at the input and output of the measuring cell 4. The radiation passes through the mirror substrate through a special slot in the mirror reflecting coating. A similar slot in the reflecting coating is used for the radiation exit from the cell. The radiation is fed into the receiver unit 42, where the laser radiation power is registered. By means of the heaters 36, 37, the required temperature is set in the measuring cell 4. The insulating elements 45 and 46 are used to ensure thermal conditioning.
The function of the reference channel 6 is that the effects of any changes caused by the degradation of the electronics/laser or by the electronics/laser temperature drifts will be recorded in the reference channel 6 and taken into account when processing the spectra of the measuring cell 4. In this way, the measuring part of the device is calibrated also. In this case, the calibration is carried out at every measurement stage.
The optical input of the reference channel 6 is connected to the optical output of the ring resonator. The signal of the reference channel 6 may be, for example, like the one shown in Fig. 7.
Absorption lines, in this case methane lines, can be seen in the signal of the reference channel. Besides, the interference pattern of the ring resonator included in the fiber-optic assembly 7 is visible.
The signal processing algorithm of the reference channel 6 makes it possible to determine both the centers of the absorption line and the centers of the interference pattern features. The diode laser re-tuning is not linear in time, which is clearly seen in the signal of the reference channel. In reciprocal centimeters, the distance between adjacent peaks of the interference pattern is equidistant and corresponds to the free dispersion region of the ring resonator. This feature is used by the algorithm to switch from the signal time scale to the reciprocal centimeter scale. In this case, the features of the interference pattern serve for relative calibration of the frequency scale, and the centers of the absorption lines serve for absolute calibration of the scale.
Further signal processing takes place in the frequency scale. So, the concentration recovery from the spectra is not sensitive to thermal deviations of the laser/electronics and their degradation during operation.
The control unit (or motherboard) of the gas analyzer controls the following:
- the extractor operation;
- the laser operation;
- the measuring cell thermal stability,
- the laser module and the device cabinet;
- reading of signals from photodiodes;
- processing of the photodiode signals;
- concentration calculations;
- reading of hydrogen and oxygen sensor data. The control unit is used also to store data.
The main measurement interface of a software menu is displayed on a PC monitor (not shown in the drawings), which shows, for example:
- components to be determined for the gas analyzer;
- measurement results of the components to be determined;
- measuring ranges;
- measuring units.
The gas analyzer makes it possible to detect the lowest gas contents - 1 ppm for C2H4, C2H6, 0.5 ppm for CH4, 0.05 ppm for C2H2, and 10 ppm for CO and CO2, - due to the long optical length and vacuum extraction.
The selective laser spectroscopy and correctly selected wavelengths ensure low crosssensitivity of measured gases to each other and to a wide range of substances dissolved in the transformer oil.
High stable accuracy of measurements over a long period of time is due to:
- the membrane assembly preventing the oil aerosol from reaching the measuring cell optics;
- maintaining vacuum in the measuring cell with simultaneous heating of the mirrors between measurement cycles, ensuring the optics self-cleaning from heavy hydrocarbons dissolved in the oil;
- use of the reference channel that compensates for temperature drifts and laser and electronics degradation effects.
The self-calibration of the extractor leads to a higher accuracy class, independent of the transformer oil, in terms of determining the solubility factors of gases in the oil.
The invention will make it possible to increase the accuracy of measurements due to a high selectivity of measurements of various gases at their sufficiently low concentrations and a low sensitivity to other substances dissolved in the oil.
The described gas analyzer will allow one to create a greater variety of special purpose devices, i.e., gas analyzers for gasses dissolved in oil.

Claims

A gas analyzer for gases dissolved in oil, the gas analyzer comprising a housing that accommodates: a control unit, a vacuum extractor for extraction of the gases from the oil via hydraulic lines for supplying the oil from a transformer into the extractor and discharging the oil from the extractor, and a measuring cell for measuring a concentration of the gasses; wherein the measuring cell is connected to the extractor and made as a Herriott optical system for multiple passes of laser radiation from one mirror to another and measuring an output intensity of the laser radiation; wherein the measuring cell is connected to a laser module and a reference channel for laser wavelength calibration; wherein a membrane assembly is installed between the extractor and the measuring cell to prevent the oil from entering the measuring cell; wherein the laser module is configured to ensure operation of each of three lasers included therein at a certain wavelength to allow measurements of different gases in a gas mixture; wherein the reference channel includes a gas-proof glass transparent container for the gas mixture, and a photodiode, wherein the mirrors of the measuring cell are provided with heaters, while the measuring cell includes warm-keeping elements; wherein the extractor is equipped with a pressure sensor and configured to be calibrated automatically using level sensors installed therein at different levels and by performing extraction at the levels of the level sensors, with subsequent measurement of the concentration of the gases at the levels and determination of a solubility factor of the gases.
PCT/FI2025/050255 2024-05-24 2025-05-16 Gas analyser Pending WO2025242962A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
RU2024114207A RU2823517C1 (en) 2024-05-24 Gas analyser
RU2024114207 2024-05-24

Publications (1)

Publication Number Publication Date
WO2025242962A1 true WO2025242962A1 (en) 2025-11-27

Family

ID=95933714

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI2025/050255 Pending WO2025242962A1 (en) 2024-05-24 2025-05-16 Gas analyser

Country Status (1)

Country Link
WO (1) WO2025242962A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103411920A (en) 2013-07-03 2013-11-27 安徽建筑大学 Portable multi-component online monitor of gas dissolved in transformer oil
CN109459411A (en) 2018-12-29 2019-03-12 云南电网有限责任公司电力科学研究院 A kind of detection platform for spectral type fibre optical sensor
CN108254338B (en) * 2018-03-20 2023-10-13 湖南五凌电力科技有限公司 Online monitoring device for gas content in transformer oil based on spectral absorption method

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103411920A (en) 2013-07-03 2013-11-27 安徽建筑大学 Portable multi-component online monitor of gas dissolved in transformer oil
CN108254338B (en) * 2018-03-20 2023-10-13 湖南五凌电力科技有限公司 Online monitoring device for gas content in transformer oil based on spectral absorption method
CN109459411A (en) 2018-12-29 2019-03-12 云南电网有限责任公司电力科学研究院 A kind of detection platform for spectral type fibre optical sensor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
JIANG JUN ET AL: "Multi-gas detection in power transformer oil based on tunable diode laser absorption spectrum", IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION, IEEE SERVICE CENTER, PISCATAWAY, NJ, US, vol. 26, no. 1, 2019, pages 153 - 161, XP011706695, ISSN: 1070-9878, [retrieved on 20190122], DOI: 10.1109/TDEI.2018.007535 *

Similar Documents

Publication Publication Date Title
CN108254338B (en) Online monitoring device for gas content in transformer oil based on spectral absorption method
US7499169B2 (en) Fuel cell and product of combustion humidity sensor
CN101782514B (en) Online monitoring device for concentration of hydrogen sulfide by laser
KR101098124B1 (en) Multigas Monitoring And Detection System
US6037592A (en) System for measuring gases dissolved in a liquid
CN207946353U (en) A kind of gas concentration detection apparatus
CN207992053U (en) Gas content in transformer oil on-Line Monitor Device based on spectral absorption method
US9212993B2 (en) Determination of sulphur dioxide in a liquid
CN109085133B (en) Off-axis integral cavity atmosphere CH based on real-time reflectivity correction4Concentration measuring device and measuring method thereof
JP2007509318A (en) Method and apparatus for detecting water vapor in natural gas
CN105765381B (en) For the method and system for the gas concentration for measuring the gas of dissolving in a liquid
Li et al. A highly sensitive low-pressure TDLAS sensor for detecting dissolved CO and CO2 in transformer insulating oil
CN110186867A (en) A kind of acetylene on-line monitoring system and method suitable for few oily equipment
US11060971B2 (en) Method and device for monitoring the quality of gaseous media
CN116499980A (en) Lunar soil water ice content and oxyhydrogen isotope calibration system and measurement system
Drouin et al. Validation of ozone intensities at 10 µm with THz spectrometry
CN212301293U (en) Modularized laboratory equipment for detecting trace gas based on photoacoustic spectroscopy principle
CN110057779B (en) Method and device for measuring gas concentration based on automatic temperature compensation TDLAS technology
WO2025242962A1 (en) Gas analyser
RU2823517C1 (en) Gas analyser
Vattulainen et al. Experimental determination of SO2, C2H2, and O2 UV absorption cross sections at elevated temperatures and pressures
Ke et al. Research on low-pressure water vapor measurement based on TDLAS technology
CN113281292A (en) Gas leakage detection device
CN112903628A (en) Trace gas detection device in negative pressure state and detection method thereof
WO2008011140A2 (en) Humidity sensor for fuel cells and combustion exhaust streams