Photo-thermal spectrum detection system for simultaneously detecting multi-component dissolved gas in transformer oil

Abstract

The invention relates to an optical fiber photo-thermal spectrum sensing system for simultaneously detecting multi-component dissolved gas in transformer oil, which is suitable for the fields of optical fiber sensing, power system state monitoring and the like and comprises a homodyne interference light path module, a pumping module and a capillary oil extraction module. The invention provides an optical fiber photo-thermal spectrum sensing system for simultaneously detecting multi-component dissolved gas in transformer oil, a broadband light source is combined with FBG filter filtering and AOM intensity modulation as pumping, multi-component gas can be detected, in order to avoid crosstalk among component signals, different modulation frequencies are set for light sources with different wavelengths, and the optical fiber photo-thermal spectrum sensing system can be used for simultaneously detecting multi-component dissolved gas in transformer oil. The simultaneous real-time detection of each component can be realized; in order to concentrate pumping energy to increase sensitivity, a capillary optical fiber with a punched side face is adopted as a detection cavity, and oil circulation between the detection cavity and a transformer oil tank is achieved through an oil pump.

Description

Technical Field

[0001] The invention relates to a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil, which is applicable to the fields of optical fiber sensing, power system status monitoring, etc. Background Art

[0002] As an important part of the power system, power transformers play a vital role in ensuring the safe and stable operation of the power system. When the transformer is overheated or has insulation failure, it will produce carbon monoxide, carbon dioxide, hydrogen and hydrocarbon gases. The operating condition of the transformer can be analyzed by detecting the content and proportion of each component gas. The traditional methods for detecting dissolved gases in transformer oil mainly include oil chromatography and photothermal spectroscopy. Due to the long detection cycle, oil chromatography cannot accurately reflect the equipment working conditions and effectively track the change trend in a timely manner, and photothermal spectroscopy cannot detect multiple gases at the same time. The use of a pump module containing a multi-gas absorption peak wavelength light source can detect multi-component gases, and has the advantages of good real-time performance and strong anti-interference ability, and has gradually become an important means of transformer status monitoring.

[0003] Photothermal spectroscopy uses the temperature signal generated by gas absorption of light energy to invert gas concentration. The light source is irradiated to the gas molecules to be measured after intensity modulation or wavelength modulation. After absorbing the light energy, the gas molecules to be measured will undergo non-radiative transition. The energy released in this process is converted into molecular internal energy. The macroscopic manifestation is the increase in the local temperature of the gas molecules. This periodic increase and decrease in local temperature causes the refractive index to change periodically. The gas concentration information can be inverted by performing frequency domain analysis on the light signal.

[0004] Oil chromatograph uses gas as mobile phase (carrier gas). When the sample is "injected" into the injector by a micro-syringe, it is carried by the carrier gas into the packed column or capillary chromatograph. Due to the difference in the distribution or adsorption coefficient between the mobile phase (gas phase) and the stationary phase (liquid phase or solid phase) in the chromatograph, the components in the sample are repeatedly distributed between the two phases under the flushing of the carrier gas, so that the tissues are separated in the column, and then the detector connected to the column detects the components in order according to the physical and chemical characteristics of the components. By analyzing the ratio of each component gas, the type of fault and its severity can be identified.

[0005] Photothermal spectroscopy can detect the concentration of a certain gas based on the characteristic absorption peaks of different gases. It has high detection accuracy and a low detection limit, but it cannot detect multiple components of gas at the same time.

[0006] Oil chromatography generally adopts periodic sampling. If the transformer fails between two samples, it is impossible to analyze its fault. If the chromatograph is directly connected to the transformer, real-time detection can be achieved, but one chromatography monitoring system can only monitor one transformer, and the utilization rate is low. At the same time, the oil chromatograph needs to oscillate and degas the oil sample, and the detection process also takes time, with poor timeliness, and cannot meet the requirements for some serious faults.

[0007] To solve the above problems, the present invention proposes a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil. A broadband light source combined with FBG filter filtering and AOM intensity modulation is used as a pump to detect multi-component gases. To avoid crosstalk between signals of each component, different modulation frequencies are set for light sources of different wavelengths, so that each component can be detected simultaneously in real time. In order to concentrate the pump energy to increase sensitivity, a capillary optical fiber with holes on the side is used as the detection chamber, and oil circulation between the oil pump and the transformer oil tank is realized through an oil pump. Summary of the invention

[0008] The invention relates to a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil, which is applicable to the fields of optical fiber sensing, power system status monitoring, etc.

[0009] Figure 1 This is a schematic diagram of a homodyne interference optical path module of a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil provided by the present invention. Figure 2 A schematic diagram of a pump module of a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil provided by the present invention. Figure 3 A schematic diagram of a capillary oil production module of a photothermal spectroscopy detection system for simultaneously detecting multi-component dissolved gases in transformer oil provided by the present invention.

[0010] The process of generating pump light in the pump module is as follows: the broadband light source module 207 generates 1W broadband light of 1530-1680nm covering the absorption peaks of methane, ethane, ethylene, acetylene, carbon monoxide, and carbon dioxide, and the power is evenly distributed to six paths through the wavelength division multiplexing module 1 208, and the light at the absorption peak wavelengths of the six characteristic gases is filtered out respectively through the FBG modules 201-206, and the intensity of the six paths of light is modulated by the AOM modules 211-216 respectively. In order to avoid mutual crosstalk between the six paths of signals, the modulation frequencies of the six paths of the AOM modules 211-216 are set to 20kHz, 22kHz, 24kHz, 26kHz, 28kHz, and 30kHz respectively. After filtering and modulation, the six paths of light are combined into one path through the wavelength division multiplexer 2 module, and the optical signal is amplified to 200mW through the EDFA module 210 and output as pump light.

[0011] The working process of the capillary oil extraction module is as follows: the transformer oil in the transformer oil tank is pumped into the oil storage chamber 307 through the oil inlet 309 by the oil pump 308, and then flows into the transformer oil tank through the oil outlet 310 to complete the oil circulation. The capillary optical fiber 303 is processed to obtain the side cut hole 304. After melting its two ends to close its end faces, microholes are made at both ends of the oil storage chamber 307 to allow the capillary optical fiber to pass through and expose the end, and then sealed and fixed with ultraviolet glue. The incident optical fiber 301 is connected to the capillary optical fiber 303 through the incident light ceramic ferrule 302, and the output optical fiber 306 is connected to the capillary optical fiber 303 through the output light ceramic ferrule 306. When the gas concentration in the oil changes, the transformer oil containing dissolved gas will quickly exchange between the transformer oil tank and the capillary optical fiber 303, and the phase signal contained in the optical path will change, realizing the real-time detection of dissolved gas in the transformer.

[0012] The principle of the homodyne interference optical path module for real-time detection of multi-component gas dissolved in transformer oil is as follows: the detection light module 101 emits a narrow linewidth laser with a wavelength of 1550nm, which is divided into two paths through a coupler and enters the capillary oil production module 102 and the PZT module 104 respectively. When the transformer oil contains six characteristic gases to be detected, six phase modulation signals of 20kHz, 22kHz, 24kHz, 26kHz, 28kHz, and 30kHz will be generated under the photothermal modulation of the pump module 103. The optical signal passes through the FBG filter module 105 to filter out the optical signal with a wavelength near 1550nm, and then beats with the optical signal of the PZT module 104 through the optical coupler. The optical signal after the beat is converted into an electrical signal through the balanced photodetector module 106 and received by the data acquisition card module 107. The contents of the six characteristic gases of methane, ethane, ethylene, acetylene, carbon monoxide, and carbon dioxide can be inferred by demodulating the contents of the six phase modulation signals of 20kHz, 22kHz, 24kHz, 26kHz, 28kHz, and 30kHz respectively. Among them, the PZT module receives the beat frequency electrical signal output by the balanced photodetector module 106, and adjusts the winding single-mode optical fiber under PID control to make the homodyne interference working point in the best state. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of a homodyne interference optical path module of a photothermal spectroscopy detection system for simultaneously detecting multi-component dissolved gases in transformer oil provided by the present invention.

[0014] Figure 2 A schematic diagram of a pump module of a photothermal spectroscopy detection system for simultaneously detecting multi-component dissolved gases in transformer oil provided by the present invention.

[0015] Figure 3 A schematic diagram of a capillary oil production module of a photothermal spectroscopy detection system for simultaneously detecting multi-component dissolved gases in transformer oil provided by the present invention. Specific implementation plan The embodiments are described in detail below in conjunction with the accompanying drawings.

[0016] In order to more clearly explain the objectives, technical solutions and advantages of this patent application, the following content will describe this application in detail with reference to the accompanying drawings and examples. It should be noted that the embodiments described herein are only used to explain the contents of this application and do not constitute any limitation to this application. Any other implementation methods obtained by any person skilled in the art according to this application without performing creative work shall be deemed as the scope of protection covered by this application.

[0017] The drawings mentioned in the patent only show some examples or implementations of the present patent application. For those of ordinary skill in the art, they can apply the principles of the present application to other similar situations based on these drawings without performing creative work. At the same time, it should also be recognized that although complex efforts may be required during the development process, for those of ordinary skill in the art, the adjustments and changes in design, manufacturing or production based on the technical content disclosed in the present application are merely routine technical operations and should not be regarded as incompleteness of the disclosure of the present application.

[0018] Figure 1 This is a schematic diagram of a homodyne interference optical path module of a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil provided by the present invention. Figure 2 A schematic diagram of a pump module of a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil provided by the present invention. Figure 3 A schematic diagram of a capillary oil production module of a photothermal spectroscopy detection system for simultaneously detecting multi-component dissolved gases in transformer oil provided by the present invention.

[0019] Embodiment 1: Figure 1The present invention provides a schematic diagram of a homodyne interference optical path module of a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil, and provides the homodyne interference optical path structure of the present invention. The principle of the homodyne interference optical path module for real-time detection of multi-component dissolved gases in transformer oil is as follows: the detection light module 101 emits a narrow linewidth laser with a wavelength of 1550nm, which is divided into two paths through a coupler and enters the capillary oil production module 102 and the PZT module 104 respectively. When the transformer oil contains six characteristic gases to be detected, six phase modulation signals of 20kHz, 22kHz, 24kHz, 26kHz, 28kHz, and 30kHz will be generated under the photothermal modulation of the pump module 103. The optical signal passes through the FBG filter module 105 to filter out the optical signal with a wavelength near 1550nm, and then beats with the optical signal of the PZT module 104 through the optical coupler. The optical signal after the beat is converted into an electrical signal through the balanced photodetector module 106 and received by the data acquisition card module 107. The contents of the six characteristic gases of methane, ethane, ethylene, acetylene, carbon monoxide, and carbon dioxide can be inferred by demodulating the contents of the six phase modulation signals of 20kHz, 22kHz, 24kHz, 26kHz, 28kHz, and 30kHz respectively. Among them, the PZT module receives the beat frequency electrical signal output by the balanced photodetector module 106, and adjusts the winding single-mode optical fiber under PID control to make the homodyne interference working point in the best state.

[0020] Embodiment 2: Figure 2 A schematic diagram of a pump module of a photothermal spectroscopy detection system for simultaneously detecting multi-component dissolved gases in transformer oil provided by the present invention is provided, and a pump optical path of the photothermal spectroscopy detection system of the present invention is provided, the broadband light source module 207 generates 1W broadband light of 1530-1680nm covering the absorption peaks of methane, ethane, ethylene, acetylene, carbon monoxide, and carbon dioxide, the power is evenly distributed to six paths through the wavelength division multiplexing 1 module 208, the lights at the absorption peak wavelengths of six characteristic gases are respectively filtered out through the FBG modules 201-206, and the six paths of light are intensity modulated by the AOM modules 211-216, and in order to avoid mutual crosstalk among the six paths of signals, the modulation frequencies of the six paths of the AOM modules 211-216 are respectively set to 20kHz, 22kHz, 24kHz, 26kHz, 28kHz, and 30kHz. After filtering and modulation, the six optical paths are combined into one path through the wavelength division multiplexer 2 module, and the optical signal is amplified to 200 mW through the EDFA module 210 and output as pump light.

[0021] Embodiment 3: Figure 3The present invention provides a schematic diagram of a capillary oil extraction module of a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil, which provides the principle of the capillary oil extraction module of the present invention. The transformer oil in the transformer oil tank is pumped into the oil storage chamber 307 through the oil inlet 309 by the oil pump 308, and then flows into the transformer oil tank through the oil outlet 310 to complete the oil circulation. The capillary optical fiber 303 is processed to obtain the side cut hole 304. After melting its two ends to close its end face, microholes are made at both ends of the oil storage chamber 307 to allow the capillary optical fiber to pass through and expose the end, and then sealed and fixed with ultraviolet glue. The incident optical fiber 301 is connected to the capillary optical fiber 303 through the incident light ceramic ferrule 302, and the output optical fiber 306 is connected to the capillary optical fiber 303 through the output light ceramic ferrule 306. When the gas concentration in the oil changes, the transformer oil containing dissolved gas will quickly exchange between the transformer oil tank and the capillary optical fiber 303, and the phase signal contained in the optical path will change, thereby achieving real-time detection of dissolved gas in the transformer.

Claims

1. The present invention proposes a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil, which comprises three parts: a homodyne interference optical path module, a pump module, and a capillary oil production module. The homodyne interference optical path module includes a detection light module 101, a capillary oil production module 102, a pump module 103, a PZT module 104, a FBG filter module 105, a balanced photodetector module 106, and a data acquisition card module 107; the pump module includes FBG modules 201-206, a broadband light source module 207, a wavelength division multiplexer 1 module 208, a wavelength division multiplexer 2 module 209, an EDFA module 210, and AOM modules 211-216; the capillary oil production module includes an incident optical fiber 301, an incident light ceramic ferrule 302, a capillary optical fiber 303, a side cut hole 304, an output light ceramic ferrule 305, an output optical fiber 306, an oil storage chamber 307, an oil pump 308, an oil inlet 309, and an oil outlet 310.

2. The pump module of the photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil according to claim 1, characterized in that: The process of generating pump light in the pump module is as follows: the broadband light source module 207 generates 1W broadband light of 1530-1680nm covering the absorption peaks of methane, ethane, ethylene, acetylene, carbon monoxide, and carbon dioxide, and the power is evenly distributed to six paths through the wavelength division multiplexing module 1 208, and the light at the absorption peak wavelengths of the six characteristic gases is filtered out respectively through the FBG modules 201-206, and the intensity of the six paths of light is modulated by the AOM modules 211-216 respectively. In order to avoid mutual crosstalk between the six paths of signals, the modulation frequencies of the six paths of the AOM modules 211-216 are set to 20kHz, 22kHz, 24kHz, 26kHz, 28kHz, and 30kHz respectively. After filtering and modulation, the six paths of light are combined into one path through the wavelength division multiplexer 2 module, and the optical signal is amplified to 200mW through the EDFA module 210 and output as pump light.

3. The capillary oil production module of a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil according to claim 1, characterized in that: The working process of the capillary oil extraction module is as follows: the transformer oil in the transformer oil tank is pumped into the oil storage chamber 307 through the oil inlet 309 by the oil pump 308, and then flows into the transformer oil tank through the oil outlet 310 to complete the oil circulation. The capillary optical fiber 303 is processed to obtain the side cut hole 304. After melting its two ends to close its end faces, microholes are made at both ends of the oil storage chamber 307 to allow the capillary optical fiber to pass through and expose the end, and then sealed and fixed with ultraviolet glue. The incident optical fiber 301 is connected to the capillary optical fiber 303 through the incident light ceramic ferrule 302, and the output optical fiber 306 is connected to the capillary optical fiber 303 through the output light ceramic ferrule 306. When the gas concentration in the oil changes, the transformer oil containing dissolved gas will quickly exchange between the transformer oil tank and the capillary optical fiber 303, and the phase signal contained in the optical path will change, realizing the real-time detection of dissolved gas in the transformer.

4. The homodyne interference optical path module of a photothermal spectrum detection system for simultaneously detecting multi-component dissolved gases in transformer oil according to claim 1, characterized in that: The principle of the homodyne interference optical path module for real-time detection of multi-component gas dissolved in transformer oil is as follows: the detection light module 101 emits a narrow linewidth laser with a wavelength of 1550nm, which is divided into two paths through a coupler and enters the capillary oil production module 102 and the PZT module 104 respectively. When the transformer oil contains six characteristic gases to be detected, six phase modulation signals of 20kHz, 22kHz, 24kHz, 26kHz, 28kHz, and 30kHz will be generated under the photothermal modulation of the pump module 103. The optical signal passes through the FBG filter module 105 to filter out the optical signal with a wavelength near 1550nm, and then beats with the optical signal of the PZT module 104 through the optical coupler. The optical signal after the beat is converted into an electrical signal through the balanced photodetector module 106 and received by the data acquisition card module 107. The contents of the six characteristic gases of methane, ethane, ethylene, acetylene, carbon monoxide, and carbon dioxide can be inferred by demodulating the contents of the six phase modulation signals of 20kHz, 22kHz, 24kHz, 26kHz, 28kHz, and 30kHz respectively. Among them, the PZT module receives the beat frequency electrical signal output by the balanced photodetector module 106, and adjusts the winding single-mode optical fiber under PID control to make the homodyne interference working point in the best state.

Images