A method for detecting concentration of gas based on dielectric barrier discharge plasma emission spectrum

Abstract

The application relates to a gas concentration detection method based on medium resistance discharge plasma emission spectrum, which comprises the following steps: S1, sampling and excitation; S2, spectrum collection and pretreatment; S3, characteristic waveband integration and ratio construction; S4, pressure correction; S5, segmented function calibration and concentration inversion; and S6, judgment and output. The stable spectrum characteristics of the to-be-detected gas formed under plasma excitation are taken as information carriers, and the influences of optical path attenuation, energy fluctuation and environmental disturbance are weakened through pressure correction strategy of the ratio, so that continuous detection and quantitative inversion of the mixed gas component change are realized under the conditions that no tracer gas is introduced, the light background is not sensitive, and the anti-electromagnetic interference advantage is possessed.

Description

Technical Field

[0001] This application belongs to the field of discharge plasma spectral detection and gas concentration measurement technology, specifically relating to a gas concentration detection method based on dielectric barrier discharge plasma emission spectrum. Background Technology

[0002] In power systems, gas-insulated transmission lines (GILs) are widely used in urban underground corridors, cross-river and cross-sea passages, and power supply channels for critical loads due to their large transmission capacity and high operational reliability. With increasing environmental protection and maintenance requirements, some low-voltage GILs are beginning to use environmentally friendly gases such as nitrogen (N2) as the insulating medium to replace the traditional SF6 gas solution. In nitrogen insulation, the purity and pressure of the medium within the gas chamber directly determine the insulation strength and discharge initiation conditions. Even a minor leak can lead to external air intrusion or a drop in gas pressure, causing a shift in gas composition and a reduction in the local electric field strength, thus affecting the long-term reliable operation of the line. Therefore, engineering and maintenance of GILs requires a detection method capable of sensitively identifying and quantitatively assessing changes in the nitrogen medium's state to achieve early leak warning, trend tracking, and operational risk assessment.

[0003] Currently, gas leak and gas composition change detection mainly includes methods such as infrared imaging, tracer gas, acoustics, and pressure, as well as optical sensing and data-driven visualization reconstruction methods that have been developed in recent years. Among these: (1) Infrared imaging leak detection usually utilizes the characteristic absorption of specific gases in the infrared band to achieve temperature difference comparison imaging. It can achieve non-contact, visualization and rapid positioning at a certain distance and is suitable for scenarios such as live inspection. However, because it is very sensitive to the infrared absorption characteristics of gases, it is easily affected by factors such as background temperature field, illumination, and wind field. Furthermore, its sensitivity and stability are insufficient for small leaks and low contrast conditions.

[0004] (2) The tracer gas method introduces a small amount of inert tracer gas into the target space and uses the sensor response time, rise rate and steady-state concentration difference to achieve localization and quantification. CFD simulation can be used to guide sensor placement. However, this type of method often requires an additional gas source and operating condition calibration, making engineering implementation complex. In scenarios such as enclosed spaces or long corridors, the results are greatly affected by factors such as structural layout and ventilation conditions. The response may be slow when there is a small leak, and the long-term operation and maintenance costs are high. It may also change the original gas environment and affect the purity of the medium.

[0005] Foreign testing solutions for gas-insulated equipment include using optical sensing to supplement traditional electrical testing methods, emphasizing resistance to electromagnetic interference and reusability; infrared-based leak target detection combined with spatiotemporal feature extraction, multi-scale fusion, and temporal modeling to improve small target detection capabilities; and acoustic emission-based leak detection treating leaks as continuous sound sources, extracting features through structural surface vibration signals to assist in judgment and location.

[0006] All of these technologies demonstrate the advantages of visualization, positioning, and deployment design, but there are still some problems: First, the ability to detect small leaks in their early stages is still affected by environmental disturbances and weakening of characteristics; second, the consistency across operating conditions under continuous detection is insufficient; and third, for media systems represented by environmentally friendly gases such as pure nitrogen, existing methods still need to be strengthened in terms of engineering adaptability and maintainability.

[0007] Based on existing technologies both domestically and internationally, it is of practical significance to propose a gas concentration change detection method with the core link of discharge plasma excitation-emission spectrum acquisition-characteristic spectral line ratio extraction-pressure correction-concentration inversion. Therefore, it is necessary to develop a set of gas concentration change detection methods that can be compared across operating conditions and are applicable to various types of closed systems, in order to make up for the shortcomings of existing technologies in detecting minute changes, long-term stability and quantitative consistency. Summary of the Invention

[0008] The purpose of this application is to overcome the shortcomings of the prior art and provide a gas concentration detection method based on dielectric barrier discharge plasma emission spectrum. This method can use the stable spectral characteristics formed by the gas to be measured under plasma excitation as an information carrier, and weaken the effects of optical path attenuation, energy fluctuation and environmental disturbance by using a pressure correction strategy for the ratio. Thus, it can realize continuous detection and quantitative inversion of the composition changes of mixed gas without the need to introduce tracer gas, without being sensitive to light background and with the advantage of anti-electromagnetic interference.

[0009] The technical problem solved by this application is achieved through the following technical solution: A gas concentration detection method based on dielectric barrier discharge plasma emission spectroscopy, the method comprising the following steps: S1. Sampling and Excitation: The gas in the space to be tested is sampled intermittently, and the sample gas is introduced into a sealed excitation chamber. A dielectric barrier discharge electrode structure is set in the excitation chamber. The dielectric barrier discharge electrode structure includes a high-voltage electrode and a ground electrode arranged opposite to each other. A quartz glass dielectric is set between the high-voltage electrode and the ground electrode to form a preset discharge gap. AC high-voltage excitation is applied to the high-voltage and low-voltage electrodes so that the electric field intensity in the discharge gap reaches the gas breakdown threshold and the continuous arc is suppressed under the barrier effect of the quartz glass dielectric, thereby generating a stable dielectric barrier discharge plasma in the discharge gap, which excites the sample gas and generates an emission spectrum. S2. Spectral Acquisition and Preprocessing: The emission spectrum is acquired through an optical lens and transmitted to a spectrometer to obtain the emission spectral data of dielectric barrier discharge plasma in real time; then the acquired spectral data is processed by dark current subtraction, wavelength calibration, noise suppression and outlier removal to obtain effective spectra for subsequent feature extraction and concentration inversion. S3. Characteristic Band Integration and Ratio Construction: The integrated intensity is obtained within a preset characteristic band, including the band intensities of the second positive band system (SPS), the first negative band system (FNS), and the NO, OH, and oxygen atom bands. The integrated intensity of the characteristic band is automatically calculated and output by the spectral acquisition software after setting the band window. This is then compared with the integrated intensity of the SPS characteristic band using a spectrometer. ~ Constructing spectral ratio characteristics using full-spectrum integrated intensity within the acquisition range This is used to reduce the impact of optical path attenuation, discharge energy fluctuations, and overall intensity drift on the measurement results. S4, Pressure Correction: For the aforementioned spectral ratio characteristic parameter... Perform pressure correction based on the on-site air pressure. Convert it to the equivalent characteristic quantity under the reference pressure The equivalent characteristic quantity Used for subsequent concentration calibration and inversion processing; S5. Piecewise function calibration and concentration inversion: Establishing a "ratio characteristic - concentration" based on multiple sets of gases with known concentrations. The calibration relationship was established, and a standard curve for inverting nitrogen concentration was generated. A piecewise function was used to fit and describe this calibration relationship, and a concentration inversion model was constructed to represent the equivalent characteristics of the gas to be measured. Input the concentration inversion model to obtain the inverted concentration. , This represents an estimated value of the nitrogen concentration in the gas being tested. S6. Judgment and Output: For the retrieved concentration... Perform trend analysis, output real-time concentration values ​​and threshold alarm results, and realize the detection and anomaly judgment of gas concentration changes.

[0010] Moreover, the S3 spectral ratio characteristics The calculation formula is: ; in: This represents the integrated spectral intensity of the second positive band system (SPS) within a preset characteristic band. Indicates that the spectrometer is in ~ Collect the full-spectrum integrated spectral intensity within the measurement range. Characterizing the proportion of SPS radiation energy to total radiation energy, it is used to reduce the impact of discharge intensity fluctuations, optical path attenuation, and background changes on measurement results, and serves as an input feature for subsequent pressure correction processing and piecewise function inversion.

[0011] Moreover, the S4 pair Pressure correction processing is performed to obtain pressure correction characteristics. , Indicates will The equivalent characteristic quantity converted to the reference pressure (1 atm) is transformed by introducing a conversion factor to facilitate pressure correction. : ; in: It is the ratio of the integrated spectral intensity of the second positive band system (SPS) to the integrated intensity of the non-SPS spectral portion, used to characterize the relative variation of the SPS spectral components with respect to the other spectral components; Indicator spectrometer ~ Within the acquisition range, the remaining full-spectrum integrated spectral intensity after deducting the integrated intensity of the SPS preset characteristic band; Parameters were estimated using the least squares method based on multi-pressure calibration data. , To minimize the deviation between the corrected curve and the reference pressure curve, the on-site pressure was read. ,Will Corrected to the equivalent value of the reference pressure : ; in, Standard atmospheric pressure; Will Substitute and inversely deduce : ; Pressure Corrected As input to the subsequent concentration inversion model.

[0012] Furthermore, the S6 triggers an abnormal concentration: in: The baseline concentration is obtained under normal operating conditions or without leakage. A rapid alarm is triggered when the concentration change threshold is exceeded.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention constructs characteristic parameters based on the emission spectrum of dielectric barrier discharge plasma and establishes a concentration inversion relationship. The gas composition change is characterized by the ratio of the integral intensity of the characteristic spectral band of SPS to the integral intensity of the full spectrum. This can effectively reduce the influence of discharge fluctuations, optical path attenuation and background disturbances on the measurement results, and improve the measurement stability and comparability under different working conditions.

[0014] 2. Compared with leakage detection methods that require the introduction of additional tracer media such as helium, this invention directly uses the discharge emission spectrum of the gas to be tested for concentration identification, without the need for additional tracer gas injection and without changing the original insulating gas environment; at the same time, the spectral signal acquisition speed is fast, which facilitates continuous tracking of gas concentration changes and enables online detection and rapid response of the leakage process.

[0015] 3. Furthermore, this invention introduces a pressure normalization correction process, converting the spectral ratio characteristics obtained under different pressure conditions into equivalent characteristic values ​​under a preset reference pressure. This reduces spectral response shifts and calibration curve discrepancies caused by pressure changes, improving the consistency of measurement results under different pressure conditions. Therefore, concentration inversion under multiple pressure conditions can be achieved based on a unified calibration relationship, enhancing the method's adaptability to fluctuations in actual operating pressure.

[0016] 4. This invention uses segmented modeling to make different concentration ranges adopt a more matching mapping relationship, which improves the ability to identify small concentration changes in the low concentration change range and maintains inversion stability in the high concentration range, thus taking into account both early change detection and wide-range quantitative measurement, which is beneficial to engineering applications. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure detected by the present invention; Figure 2 This is a diagram showing the DBD discharge luminescence phenomenon at the observation window of the reaction chamber in this invention. Figure 3 This is a typical band plasma emission spectrum of nitrogen gas according to the present invention; Figure 4 This is a graph showing the relationship between the characteristic parameters after pressure correction and the nitrogen gas integral number of the present invention. Detailed Implementation

[0018] The present application will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present application.

[0019] A gas concentration detection method based on dielectric barrier discharge plasma emission spectroscopy is innovative in that the method comprises the following steps: S1. Sampling and Excitation: (e.g., ...) Figure 1As shown, the gas concentration detection system of this invention includes a gas supply unit, a sealed excitation chamber, a high-frequency AC power supply, a spectrometer, a high-frequency current transformer, a data acquisition unit, an oscilloscope, and a host computer. The gas supply unit supplies the sample gas to the sealed excitation chamber; the high-frequency AC power supply applies a high-frequency AC voltage to the dielectric barrier discharge electrode structure; the spectrometer acquires the discharge emission spectrum; the high-frequency current transformer, data acquisition unit, and oscilloscope acquire the discharge current and electrical response signals; and the host computer receives, stores, and processes the spectral data and electrical signals.

[0020] Intermittent sampling of the gas in the test space is performed, allowing the sample gas to enter a sealed excitation chamber. A dielectric barrier discharge electrode structure is installed within the excitation chamber. This structure includes a high-voltage electrode and a grounding electrode arranged opposite each other, with a quartz glass dielectric between the high-voltage electrode and the grounding electrode forming a predetermined discharge gap. The high-voltage output terminal of a high-frequency AC power supply is connected to the high-voltage electrode, and the grounding terminal is connected to the grounding electrode. When the applied AC voltage causes the electric field strength within the discharge gap to reach the gas breakdown threshold, the sample gas forms a stable dielectric barrier discharge plasma under the barrier effect of the quartz glass dielectric, preventing continuous arc generation and exciting the sample gas to generate an emission spectral signal.

[0021] S2. Spectral acquisition and preprocessing: such as Figure 2 As shown, an optical observation window is provided on the sidewall of the sealed excitation cavity, through which the emitted light of the dielectric barrier discharge plasma formed in the discharge gap can be output. The emitted light is collected by an optical lens and transmitted to a spectrometer to obtain the emission spectrum data of the dielectric barrier discharge plasma in real time. Subsequently, the collected spectral data is processed by dark current subtraction, wavelength calibration, noise suppression and outlier removal to obtain the effective spectrum for subsequent feature extraction and concentration inversion. S3. Characteristic Band Integration and Ratio Construction: The integrated intensity is obtained within a preset characteristic band, including the band intensities of the second positive band system (SPS), the first negative band system (FNS), and the NO, OH, and oxygen atom bands. The integrated intensity of the characteristic band is automatically calculated and output by the spectral acquisition software after setting the band window. Figure 3 As shown, dielectric barrier discharge plasma generates multiple identifiable characteristic spectral peaks under different excitation voltage conditions, and the absolute spectral intensity of each peak changes with the discharge excitation conditions. To reduce the influence of discharge energy fluctuations and overall luminescence intensity variations on the concentration detection results, the integrated intensity of the SPS characteristic band is compared with that of the spectrometer. ~ Constructing spectral ratio characteristics using full-spectrum integrated intensity within the acquisition range This is used to reduce the impact of optical path attenuation, discharge energy fluctuations, and overall intensity drift on the measurement results. Spectral ratio characteristics The calculation formula is: ; in: This represents the integrated spectral intensity of the second positive band system (SPS) within a preset characteristic band. Indicates that the spectrometer is in ~ Collect the full-spectrum integrated spectral intensity within the measurement range. Characterizing the proportion of SPS radiation energy to total radiation energy, it is used to reduce the impact of discharge intensity fluctuations, optical path attenuation, and background changes on measurement results, and serves as an input feature for subsequent pressure correction processing and piecewise function inversion.

[0022] S4, Pressure Correction: For the aforementioned spectral ratio characteristic parameter... Perform pressure correction based on the on-site air pressure. Convert it to the equivalent characteristic quantity under the reference pressure ,like Figure 4 As shown, the spectral ratio characteristics obtained under different pressure conditions, after being converted to a reference pressure, tend to have the same trend as the standard curve under the reference pressure, thereby reducing the characteristic shift and calibration relationship discrepancy caused by pressure changes; the equivalent characteristic quantity Used for subsequent concentration calibration and inversion processing; right Pressure correction processing is performed to obtain pressure correction characteristics. , Indicates will The equivalent characteristic quantity converted to the reference pressure (1 atm) is transformed by introducing a conversion factor to facilitate pressure correction. : ; in: It is the ratio of the integrated spectral intensity of the second positive band system (SPS) to the integrated intensity of the non-SPS spectral portion, used to characterize the relative variation of the SPS spectral components with respect to the other spectral components; Indicator spectrometer ~ Within the acquisition range, the remaining full-spectrum integrated spectral intensity after deducting the integrated intensity of the SPS preset characteristic band; Parameters were estimated using the least squares method based on multi-pressure calibration data. , To minimize the deviation between the corrected curve and the reference pressure curve, the on-site pressure was read. ,Will Corrected to the equivalent value of the reference pressure : ; in, Standard atmospheric pressure; Will Substitute and inversely deduce : ; Pressure Corrected As input to the subsequent concentration inversion model.

[0023] S5. Piecewise function calibration and concentration inversion: Establishing a "ratio characteristic - concentration" based on multiple sets of gases with known concentrations. The calibration relationship was established, and a standard curve for inverting nitrogen concentration was generated. A piecewise function was used to fit and describe this calibration relationship, and a concentration inversion model was constructed to represent the equivalent characteristics of the gas to be measured. Input the concentration inversion model to obtain the inverted concentration. , This represents an estimated value of the nitrogen concentration in the gas being tested. S6. Judgment and Output: For the retrieved concentration... Perform trend analysis, output real-time concentration values ​​and threshold alarm results, realize the detection and anomaly judgment of gas concentration changes, and trigger concentration anomalies: in: The baseline concentration is obtained under normal operating conditions or without leakage. A rapid alarm is triggered when the concentration change threshold is exceeded.

[0024] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A gas concentration detection method based on dielectric barrier discharge plasma emission spectroscopy, characterized in that: The steps of the method are as follows: S1. Sampling and Excitation: The gas in the space to be tested is sampled intermittently, and the sample gas is introduced into a sealed excitation chamber. A dielectric barrier discharge electrode structure is set in the excitation chamber. The dielectric barrier discharge electrode structure includes a high-voltage electrode and a ground electrode arranged opposite to each other. A quartz glass dielectric is set between the high-voltage electrode and the ground electrode to form a preset discharge gap. AC high-voltage excitation is applied to the high-voltage and low-voltage electrodes so that the electric field intensity in the discharge gap reaches the gas breakdown threshold and the continuous arc is suppressed under the barrier effect of the quartz glass dielectric, thereby generating a stable dielectric barrier discharge plasma in the discharge gap, which excites the sample gas and generates an emission spectrum. S2. Spectral Acquisition and Preprocessing: The emission spectrum is acquired through an optical lens and transmitted to a spectrometer to obtain the emission spectral data of dielectric barrier discharge plasma in real time; then the acquired spectral data is processed by dark current subtraction, wavelength calibration, noise suppression and outlier removal to obtain effective spectra for subsequent feature extraction and concentration inversion. S3. Characteristic Band Integration and Ratio Construction: The integrated intensity is obtained within a preset characteristic band, including the band intensities of the second positive band system (SPS), the first negative band system (FNS), and the NO, OH, and oxygen atom bands. The integrated intensity of the characteristic band is automatically calculated and output by the spectral acquisition software after setting the band window. This is then compared with the integrated intensity of the SPS characteristic band using a spectrometer. ~ Constructing spectral ratio characteristics using full-spectrum integrated intensity within the acquisition range This is used to reduce the impact of optical path attenuation, discharge energy fluctuations, and overall intensity drift on the measurement results. S4, Pressure Correction: For the aforementioned spectral ratio characteristic parameter... Perform pressure correction based on the on-site air pressure. Convert it to the equivalent characteristic quantity under the reference pressure The equivalent characteristic quantity Used for subsequent concentration calibration and inversion processing; S5. Piecewise function calibration and concentration inversion: Establishing a "ratio characteristic - concentration" based on multiple sets of gases with known concentrations. The calibration relationship was established, and a standard curve for inverting nitrogen concentration was generated. A piecewise function was used to fit and describe this calibration relationship, and a concentration inversion model was constructed to represent the equivalent characteristics of the gas to be measured. Input the concentration inversion model to obtain the inverted concentration. , This represents an estimated value of the nitrogen concentration in the gas being tested. S6. Judgment and Output: For the retrieved concentration... Perform trend analysis, output real-time concentration values ​​and threshold alarm results, and realize the detection and anomaly judgment of gas concentration changes.

2. The gas concentration detection method based on dielectric barrier discharge plasma emission spectrum according to claim 1, characterized in that: The S3 spectral ratio characteristics The calculation formula is: ； in: This represents the integrated spectral intensity of the second positive band system (SPS) within a preset characteristic band. Indicates that the spectrometer is in ~ Collect the full-spectrum integrated spectral intensity within the measurement range. Characterizing the proportion of SPS radiation energy to total radiation energy, it is used to reduce the impact of discharge intensity fluctuations, optical path attenuation, and background changes on measurement results, and serves as an input feature for subsequent pressure correction processing and piecewise function inversion.

3. The gas concentration detection method based on dielectric barrier discharge plasma emission spectrum according to claim 1, characterized in that: The S4 pair Pressure correction processing is performed to obtain pressure correction characteristics. , Indicates will The equivalent characteristic quantity converted to the reference pressure (1 atm) is transformed by introducing a conversion factor to facilitate pressure correction. : ； in: It is the ratio of the integrated spectral intensity of the second positive band system (SPS) to the integrated intensity of the non-SPS spectral portion, used to characterize the relative variation of the SPS spectral components with respect to the other spectral components; Indicator spectrometer ~ Within the acquisition range, the remaining full-spectrum integrated spectral intensity after deducting the integrated intensity of the SPS preset characteristic band; Parameters were estimated using the least squares method based on multi-pressure calibration data. , To minimize the deviation between the corrected curve and the reference pressure curve, the on-site pressure was read. ,Will Corrected to the equivalent value of the reference pressure : ； in, Standard atmospheric pressure; Will Substitute and inversely deduce : ； Pressure Correction As input to the subsequent concentration inversion model.

4. The gas concentration detection method based on dielectric barrier discharge plasma emission spectrum according to claim 1, characterized in that: The S6 triggers an abnormal concentration: in: The baseline concentration is obtained under normal operating conditions or a leak-free condition. A rapid alarm is triggered when the concentration change threshold is exceeded.

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