A method and device for monitoring SF6 gas in a high-voltage switch cabinet

Abstract

The application relates to the technical field of gas sensor monitoring, and discloses a high-voltage switch cabinet SF6 gas monitoring method and equipment, which comprises the following steps: collecting apparent pressure, temperature and dew point data of multiple-component media in a closed space; driving a thermal excitation unit to generate a non-steady-state thermodynamic environment when the dew point fluctuates; collecting a transient response slope in a cooling stage; combining the dew point data to determine an equivalent physical bias caused by a liquid film on a diaphragm surface; stripping the bias from the apparent pressure to restore a net absolute pressure; and further calculating a medium density index. The application realizes interface physical detection in a cooling process, strips mechanical interference caused by surface tension of the liquid film, evolves pressure collection from apparent value measurement to intrinsic state extraction, eliminates measurement baseline drift caused by micro-water adsorption under working conditions, and improves the measurement precision of the sensor in a harsh environment.

Description

Technical Field

[0001] This invention relates to a method and equipment for monitoring SF6 gas in high-voltage switchgear, belonging to the field of gas sensor monitoring technology. Background Technology

[0002] Currently, a mixture of sulfur hexafluoride and nitrogen is commonly used as the insulating medium. In order to maintain the insulation strength of the equipment, gas sensor technology integrating multiple sensing units is usually used in this field. The absolute pressure and temperature signals of the mixed gas in the gas chamber are collected by the multivariable gas sensor, and the standard density is calculated by combining the gas state equation. This method of comprehensive measurement of multidimensional physical quantities based on thermodynamic parameters and gas sensor signal processing is the mainstream technical means to ensure the safe operation of high-voltage switchgear.

[0003] Under actual operating conditions of varying temperature and pressure, trace amounts of moisture inside the gas chamber are easily adsorbed onto the pressure-sensing diaphragm surface of the sensor probe. This adsorption forms a micron-sized liquid film, which not only alters the heat conduction path of the temperature-sensing component but also applies an equivalent physical bias due to surface tension to the pressure-sensing diaphragm. Existing monitoring logic directly uses the distorted pressure signal superimposed with the physical bias for density calculation, causing baseline drift in the output gas density value as the amount of adsorbed moisture accumulates. Solutions that focus on improving hardware configuration, such as setting up physical protection structures for the sensor or adding external self-cleaning components, are unlikely to eliminate interface mechanical deviations from the underlying compensation logic. For example, Chinese invention patent application CN119860812A discloses a method utilizing... The tuning fork crystal oscillator technology for monitoring SF6 / N2 gas multi-parameter self-calibrating sensors achieves physical isolation and active air jet cleaning of dust and impurities around the sensor probe by setting up a filter box, air nozzle, and pressure gas tank. Although the industry uses heating components inside the sensor to remove the liquid film on the probe surface, the heating action can only achieve physical cleaning and cannot sense and eliminate the influence of the liquid film on the pressure balance state during the measurement window. In addition, the linear correction method of simply increasing the pressure compensation factor is difficult to eliminate parasitic errors caused by the surface tension of the liquid film due to the lack of physical perception of the micromechanical changes of the diaphragm interface. This design inertia of treating the sensor interface as an ideal mechanical state limits the measurement stability of the monitoring system under full-range operating conditions.

[0004] Therefore, the technical problem to be solved by this invention is how to utilize the thermal response characteristics of the sensor during the cooling stage to construct a multi-dimensional signal compensation mechanism to improve the measurement architecture of the gas sensor, quantify and strip the liquid film bias at the pressure-sensing interface, and restore the intrinsic pressure state of the mixed gas. Summary of the Invention

[0005] To address the problems in the background art, the technical solution of the present invention is as follows: A method for monitoring SF6 gas in a high-voltage switchgear, comprising: Step S101: Collect the apparent pressure signal, temperature signal, and dew point data of the physical signal sensing component interface of the multi-component test medium in the closed space under test. Step S102: When the time series change rate of the dew point data exceeds the drift preset threshold, drive the thermal excitation unit inside the physical signal sensing component to generate an unsteady thermodynamic environment at the pressure-sensitive diaphragm interface that satisfies the preset temperature gradient range. Step S103: Stop driving the thermal excitation unit and, during the natural cooling and temperature reduction phase of the pressure-sensitive diaphragm interface, collect the transient response slope of the pressure response signal as a function of sampling time. Step S104: Input the transient response slope and dew point data into the preset mechanical interference mapping logic. The mechanical interference mapping logic determines the equivalent physical bias caused by liquid film adsorption on the pressure-sensitive diaphragm surface based on the functional dependence of the interface unsteady heat dissipation rate and the surface tension of the liquid film. Step S105: Subtract the equivalent physical bias from the apparent pressure signal and extract the net absolute pressure value that characterizes the intrinsic mechanical state of the multi-component test medium. Step S106: Substitute the net absolute pressure value, temperature signal and dew point data into the preset medium state dependent model to calculate the medium density index in the measured closed space. Step S107: Convert the net absolute pressure value, temperature signal, and medium density index into data frames that conform to the preset bus protocol and output them to the outside.

[0006] Preferably, in step S101, the multi-component test medium includes sulfur hexafluoride gas and nitrogen gas.

[0007] Preferably, in step S102, the drift preset threshold is defined as: the rate of change of the equivalent water vapor partial pressure corresponding to the dew point data within 1 second exceeds 10 Pa, or the rate of change of the temperature signal within 1 second exceeds 0.5°C.

[0008] Preferably, step S103 includes: step S1031, setting a transient sampling window during the natural cooling phase, the duration of which ranges from 10ms to 500ms; step S1032, within the transient sampling window, acquiring the change in pressure response signal relative to the sampling time, and determining the transient response slope.

[0009] Preferably, in step S104, the mechanical interference mapping logic is constructed based on the impediment effect of the specific heat capacity of the liquid film at the pressure-sensitive diaphragm interface on heat flow transfer; the transient response slope characterizes the liquid film thickness on the surface of the pressure-sensitive diaphragm, and the liquid film thickness exhibits a monotonic correlation with the equivalent physical bias.

[0010] Preferably, step S106 includes: step S1061, extracting the first virial coefficient and the second virial coefficient corresponding to the preset mixing ratio parameter; step S1062, substituting the net absolute pressure value and temperature signal into the nonlinear state equation containing the first virial coefficient and the second virial coefficient to calculate the current medium density; step S1063, using an exponential compensation operator containing the temperature signal and the temperature difference variable of a 20°C reference temperature to convert the current medium density into a medium density index.

[0011] Preferably, after step S105, the method further includes: step S1051, comparing the net absolute pressure value with the apparent pressure signal to obtain the time-series evolution index of the equivalent physical bias; step S1052, when the time-series evolution index indicates that the equivalent physical bias continues to increase and exceeds 50 Pa, generating a surface contamination warning signal for the interface of the physical signal sensing component.

[0012] Preferably, in step S1061, the first virial coefficient and the second virial coefficient are weighted based on the mole fractions of sulfur hexafluoride and nitrogen in the multi-component test medium.

[0013] Preferably, the microprocessor schedules the drive circuit of the thermal excitation unit through the instruction register and asynchronously processes the calculation task of the transient response slope in the background buffer to ensure the real-time performance of the apparent pressure signal acquisition process.

[0014] A high-voltage switchgear SF6 gas monitoring device includes: a memory for storing computer program instructions; and a processor for executing the computer program instructions to implement the steps of a high-voltage switchgear SF6 gas monitoring method.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In SF6 gas monitoring in high-voltage switchgear, an interface bias compensation mechanism based on thermal dissipation gradient is constructed. The physical quality of the surface adsorbed water film is quantified by using the temperature drop slope of the sensor probe during the natural cooling stage. The cooling process, which was originally an interference factor, is transformed into an in-situ detection method. The equivalent physical bias attached to the pressure sensing diaphragm is calculated and eliminated, so that the pressure acquisition link is transformed from the traditional apparent value measurement to the accurate extraction of the intrinsic mechanical state of the gas. The baseline drift of density measurement caused by micro water adsorption under complex working conditions is eliminated.

[0016] 2. By deeply coupling the time series drift characteristics of the dew point signal with the thermal excitation response of the probe, an automatic identification and correction closed loop for contamination of the pressure-sensing interface is formed. Utilizing the blocking effect of the specific heat capacity of the water film on the heat flow path, and with the premise of using the existing thermal components inside the sensor, the mechanical equilibrium point inside the measurement component is verified in real time. This ensures the long-term operational stability of the mixed gas density calculation in cold or high humidity environments, and avoids false alarms or missed alarms caused by the deterioration of the probe interface.

[0017] 3. By combining the preset mixed gas component ratio with the net absolute pressure after liquid film bias correction, the density characteristic value distortion caused by the cross-sensitivity of multidimensional physical quantities in complex gas chamber environments is solved through the collaborative operation of nonlinear state equations and exponential temperature compensation operators. This not only eliminates the mechanical deviation caused by surface tension, but also enables the sensor to maintain high cohesion and logical continuity of output data under different pressure ranges and temperature gradients, thereby improving the data reliability of the measurement terminal in harsh engineering environments. Attached Figure Description

[0018] Figure 1 This is a flowchart of the SF6 gas monitoring process for thermal response characteristic calibration according to the present invention. Figure 2 This is a schematic diagram of the SF6 gas monitoring device with interface liquid film interference stripping function according to the present invention.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0021] A method for monitoring SF6 gas in a high-voltage switchgear includes: Step S101: Collect the apparent pressure signal, temperature signal, and dew point data of the physical signal sensing component interface of the multi-component test medium in the closed space under test. Step S102: When the time series change rate of the dew point data exceeds the drift preset threshold, drive the thermal excitation unit inside the physical signal sensing component to generate an unsteady thermodynamic environment at the pressure-sensitive diaphragm interface that satisfies the preset temperature gradient range. Step S103: Stop driving the thermal excitation unit and, during the natural cooling and temperature reduction phase of the pressure-sensitive diaphragm interface, collect the transient response slope of the pressure response signal as a function of sampling time. Step S104: Input the transient response slope and dew point data into the preset mechanical interference mapping logic. The mechanical interference mapping logic determines the equivalent physical bias caused by liquid film adsorption on the pressure-sensitive diaphragm surface based on the functional dependence of the interface unsteady heat dissipation rate and the surface tension of the liquid film. Step S105: Subtract the equivalent physical bias from the apparent pressure signal and extract the net absolute pressure value that characterizes the intrinsic mechanical state of the multi-component test medium. Step S106: Substitute the net absolute pressure value, temperature signal and dew point data into the preset medium state dependent model to calculate the medium density index in the measured closed space. Step S107: Convert the net absolute pressure value, temperature signal, and medium density index into data frames that conform to the preset bus protocol and output them to the outside.

[0022] Preferably, in step S101, the multi-component test medium includes sulfur hexafluoride gas and nitrogen gas.

[0023] Preferably, in step S102, the drift preset threshold is defined as: the rate of change of the equivalent water vapor partial pressure corresponding to the dew point data within 1 second exceeds 10 Pa, or the rate of change of the temperature signal within 1 second exceeds 0.5°C.

[0024] Preferably, step S103 includes: step S1031, setting a transient sampling window during the natural cooling phase, the duration of which ranges from 10ms to 500ms; step S1032, within the transient sampling window, acquiring the change in pressure response signal relative to the sampling time, and determining the transient response slope.

[0025] Preferably, in step S104, the mechanical interference mapping logic is constructed based on the impediment effect of the specific heat capacity of the liquid film at the pressure-sensitive diaphragm interface on heat flow transfer; the transient response slope characterizes the liquid film thickness on the surface of the pressure-sensitive diaphragm, and the liquid film thickness exhibits a monotonic correlation with the equivalent physical bias.

[0026] Preferably, step S106 includes: step S1061, extracting the first virial coefficient and the second virial coefficient corresponding to the preset mixing ratio parameter; step S1062, substituting the net absolute pressure value and temperature signal into the nonlinear state equation containing the first virial coefficient and the second virial coefficient to calculate the current medium density; step S1063, using an exponential compensation operator containing the temperature signal and the temperature difference variable of a 20°C reference temperature to convert the current medium density into a medium density index.

[0027] Preferably, after step S105, the method further includes: step S1051, comparing the net absolute pressure value with the apparent pressure signal to obtain the time-series evolution index of the equivalent physical bias; step S1052, when the time-series evolution index indicates that the equivalent physical bias continues to increase and exceeds 50 Pa, generating a surface contamination warning signal for the interface of the physical signal sensing component.

[0028] Preferably, in step S1061, the first virial coefficient and the second virial coefficient are weighted based on the mole fractions of sulfur hexafluoride and nitrogen in the multi-component test medium.

[0029] Preferably, the microprocessor schedules the drive circuit of the thermal excitation unit through the instruction register and asynchronously processes the calculation task of the transient response slope in the background buffer to ensure the real-time performance of the apparent pressure signal acquisition process.

[0030] Preferably, a high-voltage switchgear SF6 gas monitoring device includes: a memory for storing computer program instructions; and a processor for executing the computer program instructions to implement the steps of a high-voltage switchgear SF6 gas monitoring method.

[0031] Example 1: In a real-time monitoring scenario of insulation status of a mixed gas of sulfur hexafluoride and nitrogen, the sealed gas chamber is subjected to ambient temperature fluctuations. Due to the decrease in ambient temperature, the moisture precipitated inside the gas chamber condenses on the surface of the gas sensor probe, forming a liquid film. This liquid film generates surface tension and produces an equivalent bias parameter on the pressure-sensing diaphragm of the pressure sensing component. When the time series change rate of the dew point data at the interface of the physical signal sensing component exceeds the drift preset threshold, the data processing unit of the gas sensor outputs a power control command to drive the internal thermal excitation unit, causing the pressure-sensing diaphragm interface to generate... A non-steady-state thermodynamic environment meeting the preset temperature gradient range is maintained for a first set duration. The thermal excitation unit is then stopped. During the natural cooling phase at the pressure-sensitive diaphragm interface, discrete temperature values ​​are continuously acquired via a data acquisition interface with a sampling period of 100 milliseconds. The least squares method is used to fit and analyze the discrete temperature values ​​to extract the transient response slope changing with sampling time. The attenuation difference between this transient response slope and the reference attenuation slope of the sensor in a dry state is calculated. Using a preset mechanical interference imaging model, the corresponding liquid film equivalent bias parameter is calculated based on the attenuation difference. The calculation formula is as follows: ,in, This is the equivalent bias parameter for the liquid film. This represents the attenuation difference between the transient response slope and the reference attenuation slope. The preset interfacial tension bias imaging model coefficients are used to characterize the conversion relationship between heat dissipation hindrance characteristics and surface tension interference. In this physical interference extraction process, the pressure-sensing diaphragm is affected by the transient heat flow hindrance of the surface micro liquid film. Its output dynamic pressure response signal exhibits a time-domain physical hysteresis synchronized with the cooling curve in the dynamic dimension. The transient response slope and attenuation difference fitted by the discrete temperature value are essentially the precise replacement and quantification of the mechanical response hysteresis time constant of the pressure sensing component under unsteady conditions with the evolution rate in the thermal dimension. This breaks down the cross-physical field break between mechanical response and heat dissipation in the parameter acquisition process.

[0032] Subtract the liquid film equivalent bias parameter from the acquired apparent pressure signal, strip the liquid film equivalent bias parameter to restore the net absolute pressure value, and extract the first virial coefficient corresponding to the current gas mixture ratio parameter. With the second virial coefficient Substituting the net absolute pressure value and the current temperature signal into the nonlinear state equation, the current gas density is calculated. Calculate the standard density characteristic value according to the formula: ,in, To convert to the standard density characteristic value at 20℃, Given the current gas density, For real-time temperature signal acquisition, The reference temperature constant is 293.15 Kelvin. A compensation operator incorporating temperature variables is used to correct the density evolution characteristics of a gas mixture under different thermodynamic gradients. The system writes standard density characteristic values ​​into a register block with consecutive physical addresses and outputs a gas insulation state index, eliminating interface mechanical interference, to the power equipment evaluation system via a communication bus. In the gas sensor hardware architecture with an integrated microprocessor, the physical signal sensing component converts the raw electrical signals from the pressure sensing component, temperature sensing unit, and dew point sensing unit into a 24-bit high-resolution digital sequence via a dedicated analog front-end circuit. The microprocessor periodically reads the digital sequence via the data bus according to a set timing protocol and maps it to a preset physical parameter buffer. The microprocessor extracts the dew point temperature sequence from the physical parameter buffer, calculates the physical mapping value between the saturated vapor pressure of water and the corresponding dew point temperature based on Magnus's thermodynamic empirical formula, and converts the discrete dew point temperature values ​​into an equivalent water vapor partial pressure sequence. The rate of change of the dew point data time series is determined by differential calculation of the equivalent water vapor partial pressure sequence within a unit sampling time. When the microprocessor identifies the dew point data... When the rate of change of the time series exceeds the drift preset threshold, it outputs a pulse width modulation signal to the heating drive circuit through the internal general-purpose input / output interface to control the heating power of the thermal excitation unit. At the same time, it starts a high-precision timer interrupt to trigger a temperature sampling pulse with a step size of 100 milliseconds to obtain discrete response data of the probe interface during dynamic temperature change. This hardware-level data synchronization mechanism ensures the temporal continuity of the transient response slope extraction during the cooling stage and realizes seamless integration from sensing hardware to compensation algorithm. Specifically, when implementing steady-state breaking action, the microprocessor precisely adjusts the duty cycle of the pulse width modulation signal to forcibly limit the preset temperature change gradient range formed after driving to between 2°C / s and 5°C / s. The gradient setting is based on the fact that it can input a directional heat flow sufficient to drown out the high-frequency background thermal noise of the environment to the pressure-sensitive diaphragm interface, and can effectively prevent the rapid thermal shock from inducing irreversible material thermal stress deformation inside the sensing component. It provides a standardized thermodynamic initial state reference boundary for accurately capturing the extremely weak heat dissipation hysteresis effect caused by the liquid film heat capacity.

[0033] Example 2: On a test platform simulating a closed gas chamber of a high-voltage switchgear, a multi-component mixed gas environment containing 30% sulfur hexafluoride and 70% nitrogen was established to verify the intrinsic reproduction capability of the pressure signal when there is slight water interference at the probe interface. The test platform was equipped with a pressure reference gauge with a resolution of 0.01 Pascals and a constant temperature control box with a resolution of 0.01 °C to establish the physical quantity reference. Trace amounts of moisture were introduced in stages through an atomization injection device to generate a non-uniform liquid film with a thickness of 0.5 to 5.0 micrometers at the interface of the physical signal sensing component. The sampling period was set to 100 milliseconds. The logic for determining this value is to capture the transient temperature step characteristics during the probe cooling stage, while reducing the computational overhead of the gas sensor microprocessor. Gaussian white noise with a signal-to-noise ratio of 25 dB and 50 Hz power frequency electromagnetic interference were actively superimposed on the test signal to evaluate the stability of the compensation logic under a non-ideal electromagnetic environment.

[0034] The sensor was divided into a control group and a prototype group. The control group used the apparent pressure signal to calculate the state equation, while the prototype group operated based on an interface bias compensation mechanism using a thermal dissipation gradient. When the liquid film thickness was set to 2.0 micrometers, the raw pressure data collected by the control group showed a positive deviation relative to the reference value of 125.4 Pascals. The prototype group drove its internal thermal excitation unit to 80°C and maintained it for 5 minutes. During the natural cooling phase, the transient response slope was extracted, and the corresponding attenuation difference was calculated. The value is 0.45℃ per second; using a preset interfacial tension bias image model, the equivalent bias parameter of the liquid film generated by the surface tension of the liquid film is calculated for the sample group of this invention. The value is 122.8 Pascals; the equivalent bias parameter of the liquid film is extracted from the apparent signal. The net absolute pressure output of the sample group of this invention is 101325.2 Pascals, and its deviation from the pressure reference gauge is reduced to 2.6 Pascals. The pressure error of the control group under the same operating conditions remains above 120 Pascals, confirming the effectiveness of using the thermal characteristic feedback mechanism to remove interfacial mechanical interference. The nonlinear evolution law of water injection gradient and pressure deviation was investigated. When the interfacial liquid film thickness increases in the range of 0.5 micrometers to 3.5 micrometers, the equivalent bias parameter of the liquid film is generated. Difference from attenuation It exhibits a monotonically increasing trend; when the liquid film thickness exceeds 4.0 micrometers, the liquid film gravity effect dominates over surface tension, at which point the liquid film equivalent bias parameter... The growth rate slows down, and the data curve enters the saturation plateau region. This performance inflection point establishes the physical boundary of the liquid film surface tension interference.

[0035] Under high-concentration water injection conditions with a liquid film thickness of 5.0 micrometers, the sample group of this invention dynamically adjusts the compensation operator to obtain the calculated standard density characteristic value. The deviation was controlled within 0.2%. Due to the lack of removal of interfacial mechanical interference, the output density index of the control group showed a trend of 1.5% drift with the accumulation of moisture, deviating from the safety threshold for power equipment insulation assessment. Through the comparison under the above moisture interference gradient, it was confirmed that the technical method of quantifying and compensating for the mechanical deviation of the pressure-sensing interface by utilizing the heat dissipation characteristics of the sensor during the cooling stage is feasible in engineering. While suppressing high-frequency environmental noise, the net absolute pressure of the mixed gas was extracted to eliminate the measurement baseline drift caused by the adhesion of micro-water in the closed gas chamber of the high-voltage switchgear. The output gas insulation status index maintained consistency with the physical benchmark under the full range of operating conditions, achieving the calibration of the gas sensor measurement accuracy under temperature change environment.

[0036] Example 3: This example combines Figures 1 to 2 A description of a method and equipment for monitoring SF6 gas in a high-voltage switchgear, such as... Figure 1 As shown, in step S101, apparent pressure signals, temperature signals, and dew point data of the physical signal sensing component interface of the multi-component test medium in the enclosed space are collected. In step S102, when the rate of change of dew point data exceeds a threshold, the thermal excitation unit is driven to generate an unsteady thermodynamic environment at the pressure-sensing diaphragm interface that satisfies the preset temperature gradient range. Then, in step S103, the thermal excitation unit is stopped, and during the natural cooling phase of the pressure-sensing diaphragm, the transient response slope of the pressure response signal as a function of sampling time is collected. In step S104, the transient response slope and dew point data are input into... The mechanical interference mapping logic is used to determine the equivalent physical bias caused by the adsorption of liquid film on the surface of the pressure-sensitive diaphragm. Then, in step S105, the equivalent physical bias is subtracted from the apparent pressure signal to extract the net absolute pressure value characterizing the intrinsic mechanical state of the multi-component test medium. After that, in step S106, the net absolute pressure value, temperature signal and dew point data are substituted into the preset medium state dependence model to calculate the medium density index in the closed space. Finally, step S107 is executed to convert the net absolute pressure value, temperature signal and medium density index into data frames that conform to the preset bus protocol and output them to the outside.

[0037] like Figure 2 As shown, the SF6 gas monitoring equipment for high-voltage switchgear includes a dew point data timing monitor and a drift preset threshold identification module. After identifying the phase change trend, this module is associated with the thermal excitation unit drive logic and the unsteady thermodynamic environment construction stage. It realizes liquid film thickness perception through natural cooling transient slope extraction and heat dissipation rate feature acquisition logic. At the same time, it combines the signal containing liquid film surface tension interference obtained by the apparent pressure signal sampler, and inputs them together into the mechanical interference mapping and stripping core to perform the stripping physical interference processing, and finally forms an intrinsic mechanical state extraction field at the bottom.

[0038] Example 4: In the calibration of gas sensor parameters for the enclosed gas chamber of a high-voltage switchgear, to establish the key parameters used in the pressure acquisition logic for stripping interface mechanical interference, an analytical atmosphere chamber with high-precision temperature and humidity control capability was used to simulate the microscopic condensation process of the mixed gas. The gas sensor was placed in a pure and dry mixed gas atmosphere consisting of 30% sulfur hexafluoride and 70% nitrogen by mass, with the ambient pressure set at 0.1 MPa and the temperature maintained at 20°C. The thermal excitation unit was driven to generate an unsteady thermodynamic environment that met the preset temperature gradient range, and the reference cooling curve of the probe interface was recorded. By performing linear fitting on the temperature sampling points within a time window of 3 to 10 seconds during the cooling phase, the reference attenuation slope was calculated and stored. To determine the preset threshold for the drift of the time series change rate of the dew point data, the ambient humidity was increased in the atmosphere chamber at a gradient of 1% per minute. The dew point data output by the dew point sensing unit was monitored in real time, and the deviation value of adjacent sampling periods was calculated. When the dew point data showed a unidirectional trend shift with increasing humidity, and When the deviation value exceeds 0.05℃ for five consecutive sampling points, microscopic condensation is determined to have occurred at the probe interface. Based on this, the drift preset threshold is set at 0.05℃ per cycle. This value is determined by identifying the critical inflection point where the dew point signal transitions from random thermal noise fluctuations to a physical phase change trend. Combined with the 100-millisecond timing sampling frequency set at the system's underlying level, the 0.05℃ step deviation accurately captured within a single sampling cycle, after accumulating for one second, directly and equivalently extrapolates and maps the macroscopic temperature baseline drift characteristic rate exceeding 0.5℃. Simultaneously, the saturated state physical parameters of this microscopic critical phase change node are directly input into the aforementioned Magnus thermodynamic empirical formula for inverse analytical calculation. The precise calculation shows that the water vapor partial pressure jump amplitude induced by this equivalent temperature variable in the closed chamber's background pressure dimension reaches exactly 10 Pascals. This establishes a numerical mapping verification closed loop at the physical parameter level for the monitoring equipment to perform cross-validation based on pressure or temperature to define the drift preset threshold within one second, thus establishing a mechanical interference mapping model. The offline reconstruction parameters were obtained by dripping deionized water with varying mass gradient onto the pressure-sensitive diaphragm surface using a precision micro-injection device, forming a liquid film layer with an evolving thickness ranging from 0.5 micrometers to 5.0 micrometers. For each set of liquid film thicknesses, the mechanical bias value output by the reference pressure gauge and the transient response slope extracted by the sensor during the cooling phase were simultaneously acquired. The attenuation difference between the transient response slope and the aforementioned reference attenuation slope was calculated. .

[0039] Using the least squares method to analyze multiple sets of attenuation differences The model is fitted with the corresponding mechanical bias value, and the scaling factor of the fitted curve is extracted as the coefficient of the interfacial tension bias image model. Interfacial tension bias image model coefficients The calculation formula is as follows: ,in, These are the coefficients of the interfacial tension bias image model. To calibrate the sample index, The total number of samples, For the first The decay difference between the transient response slope measured in the group of experiments and the reference decay slope. For the first The equivalent bias voltage measurement values ​​of the liquid film corresponding to the group of experiments show that, due to the standardized manufacturing process of the pressure-sensing diaphragm in the physical signal sensing component, its inherent surface roughness and the polarity of the stainless steel material keep the solid-liquid interface contact angle during micro-water condensation a constant. Under the prerequisite of the solidification of the micro-geometric morphology of the pressure-sensing interface, the micro-surface tension effect of the attached liquid film is only monotonically strongly correlated with its physical mass. Therefore, the liquid film heat capacity characterized by the depth of heat dissipation hysteresis can serve as a physical bridge to directly and monotonically map across scales to the macroscopic mechanical bias voltage vector excited on this specific diaphragm, ensuring the self-consistent closed loop of the theoretical compensation logic at the level of micro-morphology and macroscopic features. During the operation of the gas sensor, the data processing unit reads the interface tension bias voltage mapping model coefficients pre-stored in the non-volatile memory. By using the reference attenuation slope, dynamic correction of the apparent pressure signal acquired in real time is achieved; this calibration method converts the abstract interface interference quantity into a linear compensation operator that can be determined by offline experiments, eliminating the risk of algorithm divergence caused by the uncertainty of condensation degree during operation; by solidifying the dimensionally aligned calibration parameters at the bottom layer of the sensor, the system extracts the net absolute pressure value under temperature change conditions, supporting the restoration of the mixed gas density index.

[0040] Example 5: During the commissioning of a gas sensor deployed to a high-voltage switchgear in a substation, to eliminate the influence of the gas chamber's geometric volume and installation stress on the initial stress state of the pressure-sensing diaphragm, the field maintenance unit uses an external standard pressure source to inject gas into the gas chamber in a stepped manner to establish a pressure reference point. At each pressure gradient, the thermal excitation unit is driven to record the initial thermal response signal of the pressure-sensing diaphragm. Because the physical signal sensing component experiences measurement reference drift due to the aging of the sensor's encapsulation material during long-term operation, the gas sensor's data processing unit reads the initial calibration slope recorded in the non-volatile memory before each monitoring cycle begins. Calculate the adaptive compensation gain coefficient under the current environment based on the real-time temperature decay value under the current no-load condition. , It is a dimensionless calibration factor used to correct for deviations in heat transfer efficiency. The reference slope is set at the factory and this gain coefficient is applied to the mechanical interference mapping model to update the coefficients of the interfacial tension bias mapping model. .

[0041] When a gas sensor faces the aging stage of its service life exceeding 12 months, the system monitors the steady-state temperature rise peak of the thermal excitation unit under the same driving power. The evolution characteristics are used to identify the degree of thermal degradation of the probe interface. The highest temperature value after thermal excitation equilibrium is obtained, and the interfacial tension bias image model is re-corrected online according to the preset time decay weight; the data processing unit of the gas sensor extracts the average cooling rate of the last 10 desorption processes. If the deviation of this rate from the initial calibration value reaches 1%, the judgment boundary between the first set time and the drift preset threshold is automatically fine-tuned according to the linear compensation relationship. This achieves the maintenance of the mechanical interference process of the peeling interface in the pressure acquisition logic, so that the mixed gas density index remains logically converged with the physical reference throughout the entire life cycle of the equipment.

[0042] Example 6: In the deployment scenario of multi-component proportional switching of the enclosed gas chamber of a high-voltage switchgear, the physical signal sensing component is equipped with a diameter of 18 mm and a surface roughness of... A pressure-sensitive diaphragm made of SUS316L stainless steel with a diameter of 0.2 micrometers was used. The volume percentage of sulfur hexafluoride in the analytical atmosphere chamber was increased from 10% to 90% in 10% increments. For each component ratio, water mist with a mass gradient of 0.1 mg was injected into the sensor probe interface at 20°C. The mass of the adsorbed liquid film was calibrated using an electronic balance with a measurement accuracy of 0.01 mg. The second derivative characteristics of the dew point data at the phase transition point were calculated simultaneously. Based on this, a preset drift threshold corresponding to different component ratios was determined to identify the critical inflection point where the dew point signal changes from random thermal noise fluctuations to a physical phase transition trend. This led to the establishment of a segmented parameter index table stored in the sensor's non-volatile memory.

[0043] To correct for mechanical deviations caused by intermolecular interactions between different components, a calibration procedure based on the second virial coefficient interaction term was performed during the initialization phase. Within a pressure range of 0.1 MPa to 0.6 MPa, the second virial coefficient of the mixed gas was calculated using formulas based on measured apparent pressure and temperature signals. : ,in, The second virial coefficient of the gas mixture. This represents the mole fraction of sulfur hexafluoride. This represents the mole fraction of nitrogen. The second virial coefficient of pure sulfur hexafluoride. The second virial coefficient for pure nitrogen gas. The virial coefficient, representing the interaction between sulfur hexafluoride and nitrogen molecules, was determined by performing pressure backtracking calculations on a standard mixture of known density under calibration conditions. The measured values ​​are obtained and stored in the data processing unit. When the system detects that the time series change rate of the dew point data exceeds the drift preset threshold, it calls the corresponding interfacial tension bias image model coefficients in real time according to the currently identified component proportions. and This process offsets the mechanical losses at the interface of the pressure-sensitive diaphragm and extracts the intrinsic mechanical parameters of the mixed gas.

[0044] In the process of performing density index reduction using the nonlinear equation of state for a mixed gas, the microprocessor employs a numerical iterative algorithm to calculate the density index, including the first virial coefficient. With the second virial coefficient The algorithm solves the functional equation and calculates the first virial coefficient in real time based on the current temperature signal in each density reduction cycle. With the second virial coefficient The thermodynamic correction term is used, and the net absolute pressure value after removing the equivalent bias parameter of the liquid film is substituted into the objective function for residual verification. An iteration depth of at least 10 iterations is set to bring the relative error of the calculation results below 0.0001. The objective function is constructed based on the truncated virial equation of state for mixed gases, and its expression is as follows: ,in, Represents the net absolute pressure value. This represents the current gas density parameter during the iteration process. Represents the ideal gas constant. Representing the real-time absolute temperature signal, the second virial coefficient is used to construct the core of this higher-order nonlinear state function. In the thermodynamic analysis of a mixture, this parameter refers to the third-dimensional Lie constant characterizing the three-body interactions. The specific calculation method for obtaining this parameter involves using the three-body interaction constants of pure sulfur hexafluoride, pure nitrogen, and the higher-order correlation constants of the interaction between the two gases. A polynomial weighted combination calculation is performed according to the currently identified mole fraction ratios of each component in the measured medium. The derived constant value is pre-written into a read-only memory segment in the form of a static index data table during the equipment's on-site initialization phase for direct addressing and retrieval by the iterative solution process. After meeting the convergence accuracy requirement, the microprocessor extracts the characteristic constants of the thermal expansion of the medium pre-stored in the non-volatile memory. An exponential compensation operator is constructed based on the thermodynamic nonlinear scaling law. The current gas density Multiplying with the compensation operator, the density index of the medium at the output reference temperature is calculated. This dynamic iterative strategy based on physical dimension alignment eliminates the truncation error of the empirical equation under high pressure in the gas chamber, ensuring that the density index obtained by the power equipment evaluation system has physical fidelity under different component ratio conditions.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for monitoring SF6 gas in a high-voltage switchgear, characterized in that, include: Step S101: Collect the apparent pressure signal, temperature signal, and dew point data of the physical signal sensing component interface of the multi-component test medium in the closed space under test. Step S102: When the time series change rate of the dew point data exceeds the drift preset threshold, drive the thermal excitation unit inside the physical signal sensing component to generate an unsteady thermodynamic environment at the pressure-sensitive diaphragm interface that satisfies the preset temperature gradient range. Step S103: Stop driving the thermal excitation unit and, during the natural cooling and temperature reduction phase of the pressure-sensitive diaphragm interface, collect the transient response slope of the pressure response signal as a function of sampling time. Step S104: Input the transient response slope and dew point data into the preset mechanical interference mapping logic. The mechanical interference mapping logic determines the equivalent physical bias caused by liquid film adsorption on the pressure-sensitive diaphragm surface based on the functional dependence of the interface unsteady heat dissipation rate and the surface tension of the liquid film. Step S105: Subtract the equivalent physical bias from the apparent pressure signal and extract the net absolute pressure value that characterizes the intrinsic mechanical state of the multi-component test medium. Step S106: Substitute the net absolute pressure value, temperature signal and dew point data into the preset medium state dependent model to calculate the medium density index in the measured closed space. Step S107: Convert the net absolute pressure value, temperature signal, and medium density index into data frames that conform to the preset bus protocol and output them to the outside.

2. The method for monitoring SF6 gas in a high-voltage switchgear according to claim 1, characterized in that, In step S101, the multi-component test medium includes sulfur hexafluoride gas and nitrogen gas.

3. The method for monitoring SF6 gas in a high-voltage switchgear according to claim 1, characterized in that, In step S102, the drift preset threshold is defined as: the rate of change of the equivalent water vapor partial pressure corresponding to the dew point data within 1 second exceeds 10 Pa, or the rate of change of the temperature signal within 1 second exceeds 0.5°C.

4. The SF6 gas monitoring method for high-voltage switchgear according to claim 1, characterized in that, Step S103 includes: Step S1031, setting a transient sampling window during the natural cooling phase, with the duration of the transient sampling window ranging from 10ms to 500ms; Step S1032, within the transient sampling window, acquiring the change in pressure response signal relative to the sampling time, and determining the transient response slope.

5. The method for monitoring SF6 gas in a high-voltage switchgear according to claim 1, characterized in that, In step S104, the mechanical interference mapping logic is constructed based on the impediment effect of the specific heat capacity of the liquid film at the pressure-sensitive diaphragm interface on heat flow transfer; the transient response slope characterizes the liquid film thickness on the surface of the pressure-sensitive diaphragm, and the liquid film thickness exhibits a monotonic correlation with the equivalent physical bias.

6. The method for monitoring SF6 gas in a high-voltage switchgear according to claim 1, characterized in that, Step S106 includes: Step S1061, extracting the first virial coefficient and the second virial coefficient corresponding to the preset mixing ratio parameter; Step S1062, substituting the net absolute pressure value and temperature signal into the nonlinear state equation containing the first virial coefficient and the second virial coefficient to calculate the current medium density; Step S1063, using an exponential compensation operator containing the temperature signal and the temperature difference variable of the 20°C reference temperature to convert the current medium density into a medium density index.

7. The method for monitoring SF6 gas in a high-voltage switchgear according to claim 1, characterized in that, Step S105 is followed by: Step S1051, comparing the net absolute pressure value with the apparent pressure signal to obtain the time-series evolution index of the equivalent physical bias; Step S1052, when the time-series evolution index indicates that the equivalent physical bias continues to increase and exceeds 50 Pa, generating a surface contamination warning signal for the interface of the physical signal sensing component.

8. A method for monitoring SF6 gas in a high-voltage switchgear according to claim 6, characterized in that, In step S1061, the first virial coefficient and the second virial coefficient are weighted based on the mole fractions of sulfur hexafluoride and nitrogen in the multi-component test medium.

9. The method for monitoring SF6 gas in a high-voltage switchgear according to claim 1, characterized in that, The microprocessor schedules the drive circuit of the thermal excitation unit through the instruction register and asynchronously processes the calculation task of transient response slope in the background buffer to ensure the real-time performance of the apparent pressure signal acquisition process.

10. A high-voltage switchgear SF6 gas monitoring device, characterized in that, include: Memory is used to store computer program instructions; A processor for executing computer program instructions to implement the steps of the SF6 gas monitoring method for a high-voltage switchgear as described in claim 1.

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