Verification method and device for mixed gas density relay with humidity detection function

Abstract

The invention relates to a method and device for verifying a mixed gas density relay with a humidity detection function, belongs to the technical field of density relay verification, and solves the problem that the humidity and the gas mixing ratio cannot be detected at the same time during density relay verification in the prior art. The method comprises the following steps: filling a verification chamber with mixed gas until the pressure is balanced; the verification chamber is refrigerated and cooled, and the actual pressure and the actual temperature in the verification chamber, the light energy value of the light rays acted by the verification chamber and the measurement pressure read by a pressure sensor of a density relay are monitored in real time; in the cooling process, the actual pressure and the measured pressure are compared, and pressure reduction verification is carried out on a pressure sensor of the density relay; by monitoring a plurality of change rates of the light energy value, humidity detection and mixing ratio detection are sequentially carried out on the mixed gas in the verification chamber. The integration of multiple tasks is realized, and the comprehensive operation and maintenance efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of density relay calibration, in particular to a calibration method and device for a mixed gas density relay with humidity detection function. BACKGROUND

[0002] C4F7N / CO2 / O2 ternary mixed gas as a new type of environmentally friendly insulating medium, its density is a key parameter to guarantee the insulation performance of electrical equipment. At present, the industry mainly installs density relay on electrical equipment to monitor the density of the ternary mixed gas online. The basic principle is to convert the monitored gas temperature and pressure data into equivalent pressure value at 20℃ through the built-in temperature-pressure characteristic curve based on the rated mixing ratio for display and judgment.

[0003] However, the density relay may drift or fail after long-term operation, resulting in deviation between the monitored gas density value (pressure at 20℃) and the actual value, which needs to be calibrated regularly to ensure its accuracy. However, the existing calibration is usually for the alarm point and the lockout point of the density relay. In addition, the humidity of the ternary mixed gas also affects its insulation performance. Currently, a dew point meter is usually used to take offline sample detection at the equipment gas inlet or exhaust outlet to obtain the humidity value at normal pressure.

[0004] The existing technology lacks online monitoring means for gas humidity, and can only rely on regular inspection using a dew point meter for offline detection, which cannot obtain the humidity status during the intermittent period of inspection, and has safety hazards. Moreover, in the current operation and maintenance process, the calibration of the density relay, the confirmation of the gas mixing ratio, and the detection of the humidity need to use three different instruments respectively, and the operation needs to be performed three times, which is cumbersome, time-consuming and laborious, and greatly affects the operation and maintenance efficiency of the power equipment. SUMMARY

[0005] In view of the above analysis, the embodiments of the present application aim to provide a calibration method and device for a mixed gas density relay with humidity detection function, to solve the problem that the existing density relay calibration cannot simultaneously detect humidity and gas mixing ratio.

[0006] In one aspect, the embodiments of the present application provide a calibration method for a mixed gas density relay with humidity detection function, comprising the following steps: filling the mixed gas into the calibration chamber to balance the pressure; cooling the calibration chamber, and monitoring the actual pressure, actual temperature, light energy value of the light after the action of the calibration chamber, and measured pressure read by the pressure sensor of the density relay in the calibration chamber in real time; During the cooling process, the pressure sensor of the density relay is verified by comparing the actual pressure with the measured pressure; the humidity of the mixed gas in the verification chamber is detected and the mixing ratio of the mixed gas is detected in sequence by monitoring multiple change rates of the light energy value.

[0007] Based on the further improvement of the above method, the mixed gas is a ternary mixed gas of C4F7N / CO2 / O2; the light energy value is obtained by monitoring the folded light path arranged in the verification chamber, and the condensate of the ternary mixed gas of C4F7N / CO2 / O2 is condensed on the reflecting surface in the folded light path.

[0008] Based on the further improvement of the above method, the humidity of the mixed gas in the verification chamber is detected and the mixing ratio of the mixed gas is detected in sequence by monitoring multiple change rates of the light energy value, comprising: When it is detected that the light energy value decreases and the absolute value of the change rate is less than or equal to a preset moisture condensation judgment threshold, it is determined that the condensate is moisture, and the humidity detection is performed; The verification chamber continues to be cooled; when it is detected that the absolute value of the change rate of the light energy value is greater than a liquefaction judgment threshold, it is determined that the condensate is C4F7N liquid, and the mixing ratio detection is performed.

[0009] Based on the further improvement of the above method, the humidity detection comprises: When it is determined that the condensate is moisture, the actual temperature and the actual pressure in the current verification chamber are obtained, and the current actual temperature is taken as the dew point temperature under the current actual pressure, and then the moisture volume fraction is obtained by querying the moisture dew point-volume fraction reference table; According to the moisture volume fraction and the actual pressure, the humidity value under the standard pressure is calculated; If the humidity value under the standard pressure is less than or equal to the standard humidity limit value, it is determined that the humidity of the gas chamber is qualified, otherwise, an alarm is issued that the humidity of the gas chamber is over standard.

[0010] Based on the further improvement of the above method, the mixing ratio detection comprises: When it is determined that the condensate is C4F7N liquid, the actual temperature and the actual pressure in the current verification chamber are obtained, and the current actual temperature is taken as the C4F7N liquefaction temperature, and then the actual mixing ratio is obtained by querying or linear interpolation method based on the built-in temperature-pressure-mixing ratio relationship data; If the comparison result of the actual mixing ratio and the rated mixing ratio is within the set deviation range, it is determined that the mixing ratio of the gas chamber is normal, otherwise, an alarm is issued that the mixing ratio of the gas chamber is abnormal.

[0011] Based on the further improvement of the above method, the verification method further comprises: heating and warming the verification chamber; during the warming process, comparing the actual pressure in the verification chamber with the measured pressure read by the pressure sensor of the density relay in real time, and verifying the pressure increase of the density relay.

[0012] In another aspect, the embodiment of the present application provides a verification device for a mixed gas density relay with humidity detection function, comprising: The verification chamber comprises: a first temperature sensor, a first pressure sensor, a semiconductor refrigerator and an optical monitoring assembly; the first temperature sensor and the first pressure sensor are used to detect the actual temperature and the actual pressure in the verification chamber; the semiconductor refrigerator is used to adjust the temperature in the verification chamber; the optical monitoring assembly is used to form light and monitor the light energy value of the light after being affected by the verification chamber; the verification chamber is connected with the density relay; The control assembly is used to control the semiconductor refrigerator to cool the verification chamber, and the pressure values of the first pressure sensor of the verification chamber and the second pressure sensor of the density relay are collected to perform pressure decrease verification; the light energy value of the optical monitoring assembly is monitored to detect the humidity and the mixing ratio of the mixed gas in the verification chamber in sequence.

[0013] Based on the further improvement of the above device, the optical monitoring assembly comprises: a light emitting tube, a light receiving tube and a mirror surface; the light emitting tube and the light receiving tube are horizontally opposite and installed on the inner walls of the two sides of the verification chamber, and the mirror surface is installed at the bottom of the inner surface of the verification chamber and used to reflect the light emitted by the light emitting tube to the light receiving tube to form a folded light path.

[0014] Based on the further improvement of the above device, the first temperature sensor of the verification chamber is installed below and close to the mirror surface.

[0015] Based on the further improvement of the above device, the verification chamber has a circular truncated cone structure, and the cross section thereof gradually decreases from top to bottom; the outer wall of the verification chamber is made of metal; and the semiconductor refrigerator is installed on the outer wall at the bottom of the verification chamber.

[0016] Compared with the prior art, the present application can at least achieve one of the following beneficial effects: 1. Without increasing the detection sensor, the density relay verification, humidity detection and mixing ratio detection functions are added at the same time, i.e. the three independent tasks of density relay verification, humidity detection and mixing ratio detection, which are originally completed by three instruments (density verification instrument, dew point instrument and gas chromatograph) in three times, are fused into one coherent automatic operation; the traditional operation and maintenance mode is completely changed, and multiple equipment shutdowns and multiple manual interventions are combined into one, which greatly shortens the operation and maintenance time window, reduces the labor and skill requirements, and improves the comprehensive operation and maintenance efficiency.

[0017] 2. By capturing the gradual change rate of the light energy value during the condensation of moisture in the mixed gas, the dew point is calculated in real time and converted into standard humidity, realizing "quasi-online" humidity monitoring. This facilitates the immediate detection and alarm of excessive humidity during inspection intervals, significantly improving the real-time performance and safety of equipment insulation status monitoring.

[0018] 3. By identifying the steep rate of change of light energy value during C4F7N liquefaction and combining it with temperature-pressure-mixing ratio data, the actual gas mixing ratio can be deduced. This enables effective monitoring of the gas mixing ratio without relying on additional, expensive gas chromatographs, providing a low-cost and high-efficiency technical means for judging gas leaks, stratification, or abnormal decomposition.

[0019] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0020] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. Figure 1 This is a flowchart of the calibration method for the mixed gas density relay with humidity detection function in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the calibration device for the mixed gas density relay with humidity detection function in Embodiment 2 of the present invention; Figure label: 1-Verification chamber; 2-First temperature sensor; 3-First pressure sensor; 4-Light emitting tube; 5-Light receiving tube; 6-Reflecting mirror; 7-Semiconductor cooler; 8-Density relay; 9-Second pressure sensor; 10-Second temperature sensor; 11-Test gas chamber; 12-Valve; 13-First three-way valve; 14-Second three-way valve. Detailed Implementation

[0021] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0022] Example 1 A specific embodiment of the present invention discloses a calibration method for a mixed-gas density relay with humidity detection function, such as... Figure 1 As shown, it includes the following steps: S1, filling mixed gas into the calibration chamber to balance pressure; S2, cooling the calibration chamber, and monitoring actual pressure, actual temperature, light energy value of light after the calibration chamber, and measured pressure read by the pressure sensor of the density relay in real time; S3, during the cooling process, verifying the pressure sensor of the density relay by comparing the actual pressure and the measured pressure, and detecting the humidity and the mixing ratio of the mixed gas in the calibration chamber by monitoring the multiple change rates of the light energy value.

[0023] It should be noted that the mixed gas in the embodiment is a short name of mixed gas, which specifically refers to C4F7N / CO2 / O2 ternary mixed gas. The method of the embodiment is an integrated verification method, which simultaneously completes the performance verification of the C4F7N / CO2 / O2 ternary mixed gas density relay and the humidity and mixing ratio state diagnosis of the gas itself in one operation.

[0024] Specifically, in step S1, first, it is ensured that the calibration chamber and the connecting pipeline thereof have been pumped to vacuum by a vacuum pump. Then, an isolation valve of the electrical equipment is opened to make the measured gas chamber, the density relay, and the calibration chamber communicate with each other. The C4F7N / CO2 / O2 ternary mixed gas in the measured gas chamber is filled into the calibration chamber until the actual pressure collected by the pressure sensor in the calibration chamber in real time and the measured pressure read by the pressure sensor of the density relay reach balance. This step ensures that the gas sample in the calibration chamber is consistent with the gas state in the measured gas chamber, thereby providing a real and reliable sample for subsequent verification.

[0025] Further, the valve is closed to isolate the measured gas chamber, and step S2 is performed to cool the calibration chamber.

[0026] Exemplarily, the calibration chamber is provided with a semiconductor refrigerator, and the semiconductor refrigerator is started to gradually reduce the temperature of the calibration chamber.

[0027] As the temperature decreases, the actual pressure of the ternary mixed gas in the calibration chamber decreases. During this process, real-time monitoring is performed, including the actual pressure collected by the pressure sensor in the calibration chamber in real time, the actual temperature collected by the temperature sensor in the calibration chamber in real time , the light energy value of light after the calibration chamber, and the measured pressure read by the pressure sensor of the density relay. The light energy value is obtained by monitoring the folded light path arranged in the calibration chamber, and the condensate of the C4F7N / CO2 / O2 ternary mixed gas condenses on the reflecting surface in the folded light path. The actual temperature in the calibration chamber is the temperature of the reflecting surface.

[0028] It is to be noted that the folded light path greatly increases the interaction distance between the light beam and the area of the reflective surface where condensate can form. Compared to the straight light path, it is more sensitive to the light scattering effect caused by the initial and trace amount of condensate (whether it is frost or liquid film) on the reflective surface, thereby significantly improving the detection sensitivity and response speed to the small changes in the state of the gas.

[0029] Exemplarily, an optical system is formed by a light emitting tube, a light receiving tube and a mirror surface in the calibration chamber. The light emitting tube continuously emits light, which is reflected by the mirror surface to the light receiving tube to form a folded light path. A temperature sensor in the calibration chamber is close to the mirror surface, and the actual temperature of the mirror surface is collected.

[0030] When the emitting surface is clean without condensate, the folded light path is in a total reflection state, and the monitored light energy value is the initial value , which is calibrated as 100%.

[0031] In the process of real-time monitoring in step S2, step S3 is executed synchronously to compare the actual pressure and the measured pressure at different time points. If the absolute value of the difference between the two satisfies , where is a set pressure difference threshold value, which is different for density relays of different accuracy levels. Taking a density relay of accuracy level 1.0 as an example, where is the abbreviation of full scale, indicating full scale), it indicates that the indication accuracy of the pressure sensor during pressure reduction is qualified, and it is determined that the pressure detection of the density relay is qualified, and the pressure reduction calibration of the C4F7N / CO2 / O2 ternary mixed gas density relay is completed.

[0032] Further, as the continuous refrigeration, the actual temperature in the calibration chamber continuously decreases, and some components in the ternary mixed gas will reach the saturation state and start to condense. The condensate condenses on the reflective surface to cause scattered light, causing the monitored light energy value to decrease, and the change rate is calculated and recorded in real time.

[0033] By monitoring multiple change rates of the light energy value, the mixed gas in the calibration chamber is sequentially subjected to humidity detection and mixed ratio detection, including: ① When it is detected that the light energy value decreases and the absolute value of the change rate is less than or equal to a preset moisture condensation judgment threshold value, it is determined that the condensate is moisture, and the humidity detection is performed.

[0034] It should be noted that when the first mutation of the light energy value is monitored (i.e., a significant decrease from the initial value), it is determined whether the absolute value of the change rate is less than or equal to the preset moisture condensation judgment threshold. If it is less than or equal to, it is determined that the condensation on the reflecting surface at this time is water (frost), the actual temperature and the actual pressure in the current calibration chamber are obtained, and the current actual temperature is taken as the dew point temperature at the current actual pressure. The dew point temperature is higher than the liquefaction temperature of the C4F7N / CO2 / O2 ternary mixed gas.

[0035] According to the dew point temperature, the moisture volume fraction is obtained by querying the moisture dew point-volume fraction table. That is, the moisture volume fraction corresponding to the dew point temperature is obtained by querying the built-in "Appendix A Moisture Dew Point-Volume Fraction Table" in GB / T 5832.2-2016 "Gas analysis Determination of trace moisture Part 2: Dew point method".

[0036] Further, the moisture volume fraction is converted to a humidity value under standard pressure by the following formula: (1), wherein, represents the humidity value under standard pressure, represents the current actual pressure, represents the standard pressure, which is 0.1013 MPa.

[0037] The humidity value under standard pressure is compared with the standard humidity limit value (such as set to 500 μL / L). If it is less than or equal to the standard humidity limit value, it is determined that the chamber humidity is qualified, otherwise, the chamber humidity exceeds the standard alarm is issued.

[0038] Compared with the prior art, the embodiment realizes the humidity from offline sampling to online real-time diagnosis, which is convenient for timely discovery of humidity hidden dangers during intermittent inspection.

[0039] ② Continue to cool the calibration chamber; when the absolute value of the change rate of the light energy value is greater than the liquefaction judgment threshold, it is determined that the condensed material is C4F7N liquid, and the mixing ratio detection is performed.

[0040] After the moisture is liquefied, the temperature is continuously lowered, and the second mutation point of the monitored light energy value is detected. It is determined whether the absolute value of the change rate of the light energy value is greater than the liquefaction judgment threshold. If it is greater, it is determined that the condensation on the reflecting surface at this time is C4F7N liquid, and the actual temperature and the actual pressure in the current calibration chamber are obtained. The current actual temperature is taken as the C4F7N liquefaction temperature.

[0041] Further, according to the C4F7N liquefaction temperature and the current actual pressure, the actual mixing ratio is obtained by querying or linear interpolation method based on the built-in temperature-pressure-mixing ratio relationship data.​

[0042] It should be noted that the temperature-pressure-mixing ratio data were obtained through experiments. Table 1 lists the values ​​of different pressures and C4F7N liquefaction temperatures for ternary gas mixtures under four mixing ratio conditions. The actual mixing ratio can be deduced based on this table.

[0043] Table 1 Liquefaction Temperature of C4F7N / CO2 / O2 Mixed Gas

[0044] If the comparison result between the actual mixing ratio and the rated mixing ratio (i.e., the difference) is within the set deviation range, such as the absolute value of the difference being less than or equal to 1%, then the gas chamber mixing ratio is determined to be normal; otherwise, an abnormal gas chamber mixing ratio alarm is issued.

[0045] Compared with existing technologies, this embodiment achieves effective monitoring of gas mixing ratio without adding specialized equipment such as gas chromatographs, providing a key basis for judging gas leakage or decomposition.

[0046] After completing pressure verification, humidity detection, and mixing ratio detection during the refrigeration and depressurization process described above, the verification chamber is heated by controlling the semiconductor cooler. During the heating process, the liquefied gas re-vaporizes, and the pressure inside the verification chamber rises. The actual pressure inside the verification chamber is compared in real time. The pressure measured by the pressure sensor read by the density relay If the absolute value of the difference between the two satisfies If the reading is within acceptable limits, it indicates that the pressure sensor's reading accuracy is qualified during the pressurization process. The pressure detection of the density relay is deemed qualified, and the pressurization verification of the C4F7N / CO2 / O2 ternary mixed gas density relay is completed, thus realizing the bidirectional full-stroke verification of the density relay's pressure sensing function.

[0047] It should be noted that the water condensation judgment threshold and liquefaction judgment threshold used in step S2 to identify whether the condensate is water or C4F7N liquid are the key to achieving accurate identification. This embodiment provides the following two methods for pre-calibration.

[0048] (1) Theoretical modeling method It should be noted that, ideally, the condensate forms a uniform, transparent frost layer (moisture) or thin film (C4F7N liquid film) on the reflective surface, the thickness of which is proportional to the condensation mass. In the initial condensation stage, the light energy value... Attenuation and condensation layer thickness They form an approximately linear relationship, that is The condensation rate depends on the speed at which water molecules or C4F7N molecules diffuse to the reflective surface.

[0049] ①Based on Fick's diffusion law, a mass condensation rate model of condensate diffusing and condensing on the reflecting surface in the calibration chamber is established, and a first function relationship between the condensation layer thickness growth rate and the gas state parameters and the physical parameters of the condensate is obtained.

[0050] Specifically, the formula of the mass condensation rate model is as follows: (2), wherein, represents the mass condensation rate of the condensate, and the unit is ; represents the diffusion coefficient, and the unit is , represents the diffusion ability of water vapor or C4F7N gas in the background gas (CO2 / O2); represents the mass concentration of the condensate in the mainstream gas near the reflecting surface, and the unit is ; represents the mass concentration of the condensate on the reflecting surface, and the unit is , when completely condensed, ; represents the effective condensation area on the reflecting surface, and the unit is ; represents the thickness of the diffusion boundary layer near the reflecting surface, and the unit is , which is related to the gas flow state.

[0051] It is to be noted that in formula (2) is the key to calculation, which is directly related to the state of the measured gas, and is calculated by the following formula: (3), wherein, represents the partial pressure of the condensate (water or C4F7N); represents the universal gas constant, ; represents the molar mass of the condensate, and the unit is ; represents the absolute temperature of the gas.

[0052] It is to be noted that the mass of the condensate is calculated by the following formula: (4), wherein, represents the liquid or solid density of the condensate, and the unit is ; represents the condensation layer thickness, and the unit is .

[0053] The mass of the condensate in formula (4) is Differentiating with respect to time, we obtain the following formula representing the mass condensation rate: (5).

[0054] In formula (2) Substituting into formula (5), the simplified result is the growth rate of the condensed layer thickness. The first functional relationship between the gas state parameters and the physical parameters of the condensate: (6).

[0055] ②Based on the relationship between the attenuation of light energy value and the thickness of the condensate layer, and the first functional relationship, the second functional relationship between the rate of change of light energy and the physical parameters of the condensate is obtained.

[0056] Specifically, based on the optical attenuation model, the relationship between the attenuation of light energy and the thickness of the condensation layer is expressed by the following formula: (7), in, This represents the attenuated light energy value. This represents the initial light energy value; This represents the attenuation coefficient, which is measured in advance through calibration experiments.

[0057] Furthermore, according to Combining formulas (6) and (7), the second functional relationship is obtained as follows: (8).

[0058] ③ Substitute the physical property parameters of water and C4F7N into the second function relationship respectively to calculate the theoretical reference values ​​for water condensation and liquefaction. Then, based on their respective safety margins, obtain the water condensation judgment threshold and liquefaction judgment threshold.

[0059] It should be noted that the physical properties include: the molar mass of the condensate. Density of condensate and diffusion coefficient Correspondingly, the physical properties of water condensation are as follows: , (ice), The physical properties of C4F7N liquefaction and condensation are as follows: , (liquid), .

[0060] The thickness of the diffusion boundary layer near the reflective surface is set to 1 mm when the mixing ratio of the C4F7N / CO2 / O2 ternary mixed gas is 8.56%:86.03%:5.41%, the rated pressure is 0.8 MPa, and the humidity value is 500 μL / L The mass concentration of water condensation is calculated to be about about , and the mass concentration of C4F7N liquefaction condensation is calculated to be about about .

[0061] Finally, the C4F7N liquefaction condensation rate is calculated to be 273 times the water condensation rate according to formula (8), that is, , which indicates that the absolute value of the light energy value change rate during C4F7N liquefaction condensation is about 273 times that during water condensation. The signal characteristics of the two condensates are significantly different, and the risk of misjudgment is extremely low.

[0062] According to the measured attenuation coefficient in the actual application scene, the water condensation theoretical reference value and the liquefaction theoretical reference value can be calculated.

[0063] To compensate for the errors caused by model simplification and ensure reliability, a safety margin is usually set based on the theoretical reference value to obtain the water condensation judgment threshold and the liquefaction judgment threshold. The water condensation judgment threshold is usually set to 10 to 30 times the water condensation theoretical reference value, and the liquefaction judgment threshold is usually set to 1 / 5 to 1 / 20 of the liquefaction theoretical reference value.

[0064] Preferably, the water condensation judgment threshold is set to 20 times the water condensation theoretical reference value, and the liquefaction judgment threshold is set to 1 / 10 of the liquefaction theoretical reference value in the present embodiment.

[0065] (2) Experimental calibration method Simulate the field application conditions and build the same test platform.

[0066] Fill the measured gas chamber with C4F7N / CO2 / O2 with a standard humidity of 500 μL / L and a rated mixing ratio to an absolute pressure of 0.8 MPa; according to the method of the present embodiment, cool at a rate of 0.5 ℃ / min (to avoid supercooling effect), and real-time collect the actual temperature , actual pressure , light energy value, light energy value change rate, measure the maximum slope of the light energy value curve in the water condensation stage, and take the upper limit as the water condensation judgment threshold.

[0067] The dry C4F7N / CO2 / O2 mixture with the rated mixing ratio is filled into the measured gas chamber to an absolute pressure of 0.8 MPa; according to the method of the embodiment, the initial slope of the light energy value curve in the C4F7N mass condensation stage is measured at a rate of 0.5 ℃ / min, and the lower limit is taken as the liquefaction judgment threshold.

[0068] The above two threshold determination methods are parallel and equivalent. In actual application, according to different needs for accuracy, cost and development stage, any one of them is adopted, or a preliminary determination is made through theoretical calculation, and then an accurate calibration is made through experimental calibration. No matter which method is adopted, as long as the finally determined liquefaction judgment threshold is significantly greater than the moisture condensation judgment threshold, the reliable implementation of the diagnostic logic described in the application can be ensured.

[0069] It should be noted that although there is currently no humidity standard for C4F7N / CO2 / O2 ternary mixed gas electrical equipment, C4F7N / CO2 / O2 ternary mixed gas electrical equipment is mostly a gas chamber without arc decomposition products. Referring to the SF6 gas standard, if the humidity value at the standard pressure is less than or equal to 500 μL / L, the gas chamber humidity is qualified, otherwise, an alarm is issued that the gas chamber humidity is out of standard. The judgment basis in the SF6 gas standard (Q / GDW 10471-2022 “Supervision and Management Specification for Sulfur Hexafluoride Gas in Operating Electrical Equipment”) is usually the humidity value at 20 ℃, pressure, so according to formula (1), the C4F7N / CO2 / O2 ternary mixed gas electrical equipment is operated at a pressure corresponding to a humidity volume fraction . According to the moisture dew point-volume fraction table, the dew point value corresponding to this volume fraction is about -5 ℃. This indicates that for electrical equipment with a rated pressure of 0.8 MPa, the method of the embodiment needs to be able to measure a dew point of at least -5 ℃ to cover the standard requirements. Further, it is necessary to ensure that the proportion of C4F7N in the ternary mixed gas does not exceed a certain limit value, so that the C4F7N liquefaction temperature is lower than -5 ℃, so that the moisture can be condensed first.

[0070] The present embodiment can obtain the critical proportion of about 13.67% by calculation according to the Wagner-type equation and the Dalton partial pressure law. The current engineering commonly used mixing ratio (as shown in Table 1) is lower than this value, so the method has wide engineering applicability.

[0071] It should be noted that according to the following Wagner-type equation, the C4F7N gas pressure value is calculated: (9), wherein, is the C4F7N gas pressure value, The critical pressure of C4F7N gas. ; The reference temperature is the temperature at which C4F7N gas is compared. Given the current thermodynamic temperature, This is the critical temperature of C4F7N gas. ; This is a dimensionless intermediate variable, representing the ratio of the difference from the critical temperature; All are fitting coefficients: a = -6.84, b = -1.65, c = 9.26, d = -165.39.

[0072] After converting -5℃ to a thermodynamic temperature, substituting it into formula (9) yields the gas pressure of C4F7N gas at that temperature. .

[0073] Since C4F7N gas is easier to liquefy than CO2 and O2, the liquefaction temperature of the C4F7N gas mixture depends only on the liquefaction temperature of C4F7N.

[0074] The van der Waals empirical equation is adopted as the equation of state for C4F7N gas: (10), in, This indicates the pressure value, and the unit is Pa. It represents thermodynamic temperature, and its unit is K; This represents the molar volume of a gas, and the unit is _____. ; This represents the gas pressure correction factor; This represents the gas volume correction factor.

[0075] Will Substituting T = 268.15 K (-5℃) into formula (10), the molar volume of the gas is calculated. Since molar volume is independent of temperature, and mass remains constant, molar volume also remains constant. Therefore, according to molar volume... Substituting T=293.15K (20℃) into formula (10), the corresponding C4F7N gas pressure at 20℃ is calculated. .

[0076] For a C4F7N gas mixture with a total pressure of 0.8 MPa at 20°C, the partial pressures of each component at 20°C are calculated using the following formula based on Dalton's law of partial pressures: (11), in, This represents the pressure value of C4F7N gas in a ternary gas mixture, in MPa. The proportion of C4F7N gas in the ternary mixed gas is 13.67%, which is obtained by calculation.

[0077] Compared with the prior art, the verification method of the mixed gas density relay with humidity detection function provided by the embodiment can complete the verification of the density relay while increasing the mixed ratio detection and humidity detection function without increasing the detection sensor, that is, the three independent tasks of the density relay verification, humidity detection, and mixed ratio detection, which originally need to be completed three times by using three instruments (a density verification instrument, a dew point instrument, and a gas chromatograph), are fused into one continuous automatic operation. The traditional operation and maintenance mode is completely changed, and the multiple device shutdowns and multiple manual interventions are combined into one, so that the operation and maintenance time window is greatly shortened, the manual work and skill requirements are reduced, and the comprehensive operation and maintenance efficiency is improved. By capturing the change rate of the light energy value of the water condensation in the mixed gas, the dew point is calculated in real time and converted into the standard humidity, so that the "quasi-online" monitoring of the humidity is realized, the humidity exceeding the standard can be found and an alarm can be given in the intermittent period of the inspection, and the real-time performance and safety of the equipment insulation state monitoring are significantly improved. By identifying the steep change rate of the light energy value of the steep C4F7N liquefaction, and combining the temperature-pressure-mixed ratio relationship data, the actual mixed ratio of the gas is inversely deduced, so that the effective monitoring of the gas mixed ratio is realized without relying on an additional and expensive gas chromatograph, and a low-cost and efficient technical means is provided for judging the gas leakage, layering, or abnormal decomposition.

[0078] Embodiment 2 Another embodiment of the present application discloses a verification device of a mixed gas density relay with humidity detection function, so as to realize the verification method of the mixed gas density relay with humidity detection function in the embodiment 1. The specific implementation modes of the components in the device are referred to the corresponding descriptions in the embodiment 1. As shown in the figure, the device comprises: Figure 2 a verification chamber 1 comprising a first temperature sensor 2, a first pressure sensor 3, a semiconductor refrigerator 7, and an optical monitoring component; the first temperature sensor 2 and the first pressure sensor 3 are used to detect the actual temperature and the actual pressure in the verification chamber 1; the semiconductor refrigerator 7 is used to adjust the temperature in the verification chamber 1; the optical monitoring component is used to form light and monitor the light energy value of the light after the action of the verification chamber 1; the verification chamber 1 is connected with a density relay 8; a control component used to control the semiconductor refrigerator 7 to cool the verification chamber 1, to perform pressure reduction verification by collecting the pressure values of the first pressure sensor 3 of the verification chamber 1 and the second pressure sensor 9 of the density relay 8; and to perform humidity detection and mixed ratio detection on the mixed gas in the verification chamber 1 in turn by monitoring the multiple change rates of the light energy value of the optical monitoring component.

[0079] ​It should be noted that the first pressure sensor 3 in the calibration chamber 1 is installed at the top of the calibration chamber 1, directly measuring the gas pressure, avoiding the influence of condensate at the bottom on the measurement accuracy.

[0080] The optical monitoring assembly includes a light emitting tube 4, a light receiving tube 5 and a mirror surface 6; the light emitting tube 4 and the light receiving tube 5 are horizontally opposite installed on the inner walls of the two sides of the calibration chamber 1, and the mirror surface 6 is installed on the bottom of the inner surface of the calibration chamber 1, used for reflecting the light emitted by the light emitting tube 4 to the light receiving tube 5 to form a folded light path. The installation angle and height of the light emitting tube 4 and the light receiving tube 5 ensure that the light can irradiate to the mirror surface 6 and reflect to the light receiving tube 5.

[0081] The light path is reflected once by the mirror surface 6 to form a folded light path, greatly increasing the interaction distance of light and condensate, and improving the detection sensitivity of trace condensation.

[0082] The first temperature sensor 2 of the calibration chamber 1 is installed below and close to the mirror surface 6, which is convenient for real-time and accurate measurement of the mirror surface temperature, i.e. the mirror surface temperature at which condensation occurs, which is the key to obtaining the dew point temperature and the liquefaction temperature.

[0083] It should be noted that the calibration chamber 1 has a circular truncated cone structure, and its cross section gradually decreases from top to bottom, i.e. it is a circular truncated cone with a wide top and a narrow bottom. Correspondingly, the mirror surface 6 is circular.

[0084] The circular truncated cone structure is conducive to natural convection of the gas during the cooling process, concentrates the low-temperature area at the bottom, promotes the uniform formation of condensate on the mirror surface at the bottom, and at the same time reduces the thermal interference of the upper space, ensuring the controllability and consistency of the temperature field and the condensation process.

[0085] The outer wall of the calibration chamber 1 is made of metal; the semiconductor cooler 7 is installed on the metal outer wall at the periphery of the bottom of the calibration chamber 1. The metal outer wall (such as aluminum alloy) has good thermal conductivity, which can ensure that the refrigeration / heating power is quickly and uniformly transmitted to the entire bottom of the chamber, thereby accurately controlling the temperature change rate of the mirror surface.

[0086] Arranging the semiconductor cooler 7 at the bottom in combination with the circular truncated cone structure forms a temperature gradient from top to bottom, which is convenient for realizing the monitoring of pressure at the top and the induction and monitoring of condensation at the bottom.

[0087] The control assembly is signal connected or connected through data line with the first temperature sensor 2, the first pressure sensor 3, the semiconductor cooler 7 and the optical monitoring assembly, the second pressure sensor 9 and the second temperature sensor 10 of the density relay 8 of the calibration chamber 1; the control assembly includes an operation unit, and the operation unit includes a touch screen for displaying, setting data and sending instructions.

[0088] The check chamber 1 is communicated with the valve 12 of the measured gas chamber 11 and the density relay 8 through the second three-way valve 14 and the first three-way valve 13 in turn.

[0089] Specifically, the three ports of the first three-way valve 13 are connected to the valve 12 of the measured gas chamber 11, the density relay 8 and one end of the second three-way valve 14 respectively; the other two ports of the second three-way valve 14 are connected to the check chamber 1 and a vacuum pump or a gas supplement port respectively.

[0090] During the check, the vacuum pump is started to ensure that the check chamber 1 and the connecting pipeline thereof are vacuumized by the vacuum pump. Then, the valve 12 is opened to communicate the measured gas chamber 11, the density relay 8 and the check chamber 1.

[0091] The control assembly internally stores a check program for coordinating the actions of other assemblies, collecting sensor data, table lookup, data calculation, logical judgment and outputting check results or alarm signals to perform all comparisons, calculations, table lookups, logical judgments and alarm outputs in the method of Embodiment 1.

[0092] Since the check device of the gas mixing density relay with the humidity detection function in the embodiment is related to the check method of the gas mixing density relay with the humidity detection function, the two can be mutually referred to, and thus repeated description is not given here.

[0093] Compared with the prior art, the device of the embodiment integrates pressure monitoring, optical monitoring and precise temperature control in a compact chamber through its unique structural design, not only provides a reliable hardware platform for the implementation of the integrated check method, but also creates an ideal physical environment for high-precision pressure measurement, accurate condensation temperature capture and controllable condensation process through the features such as the circular truncated cone structure, optimized sensor layout and metal heat-conducting outer wall, and fundamentally guarantees the accuracy of the data and the reliability of the results of the whole method. Since the device embodiment has the same principle as the method embodiment, the device embodiment also has the corresponding technical effects of the method embodiment.

[0094] Those skilled in the art can understand that all or part of the processes of the above-mentioned embodiments can be completed by a computer program instructing related hardware, and the program can be stored in a computer readable storage medium. The computer readable storage medium is a disk, an optical disk, a read-only memory or a random access memory, etc.

[0095] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited to this. Any changes or replacements within the technical range disclosed by the present application can be easily thought of by those skilled in the art, and should be covered within the protection scope of the present application.

Claims

1. A method for calibrating a mixed gas density relay with a humidity detection function, characterized in that, The method comprises the following steps: The mixed gas is filled into the calibration chamber to balance the pressure; The calibration chamber is cooled by refrigeration, and the actual pressure, the actual temperature, the light energy value of the light after being affected by the calibration chamber, and the measured pressure read by the pressure sensor of the density relay in the calibration chamber are monitored in real time; During the cooling process, the pressure sensor of the density relay is verified by comparing the actual pressure and the measured pressure; the humidity detection and the mixed ratio detection of the mixed gas in the calibration chamber are sequentially performed by monitoring the multiple change rates of the light energy value.

2. The method of claim 1, wherein the method further comprises: determining whether the humidity sensor is operating properly based on the comparison. The mixed gas is C4F7N / CO2 / O2 ternary mixed gas; the light energy value is obtained by monitoring the folded light path arranged in the calibration chamber, and the condensate of the C4F7N / CO2 / O2 ternary mixed gas is condensed on the reflecting surface in the folded light path.

3. The method of claim 2, wherein the method further comprises: determining whether the humidity sensor is operating properly based on the comparison. The humidity detection and the mixed ratio detection of the mixed gas in the calibration chamber are sequentially performed by monitoring the multiple change rates of the light energy value, comprising: When it is detected that the light energy value decreases and the absolute value of the change rate is less than or equal to a preset moisture condensation judgment threshold, it is determined that the condensate is moisture, and the humidity detection is performed; The calibration chamber is continuously cooled; when it is detected that the absolute value of the change rate of the light energy value is greater than a liquefaction judgment threshold, it is determined that the condensate is C4F7N liquid, and the mixed ratio detection is performed.

4. The method of claim 3, wherein the method further comprises: The humidity detection comprises: When it is determined that the condensate is moisture, the actual temperature and the actual pressure in the current calibration chamber are obtained, the current actual temperature is taken as the dew point temperature under the current actual pressure, and then the moisture volume fraction is obtained by querying the moisture dew point-volume fraction table; According to the moisture volume fraction and the actual pressure, the humidity value under the standard pressure is calculated; If the humidity value under the standard pressure is less than or equal to the standard humidity limit value, it is determined that the gas chamber humidity is qualified, otherwise, a gas chamber humidity exceeds the standard alarm is issued.

5. The method of claim 3, wherein the method further comprises: determining whether the humidity sensor is operating properly based on the comparison. The mixed ratio detection comprises: When it is determined that the condensate is C4F7N liquid, the actual temperature and the actual pressure in the current calibration chamber are obtained, the current actual temperature is taken as the C4F7N liquefaction temperature, and then the actual mixed ratio is obtained based on the built-in temperature-pressure-mixed ratio relationship data by querying or linear interpolation method; If the comparison result of the actual mixed ratio and the rated mixed ratio is within the set deviation range, it is determined that the gas chamber mixed ratio is normal, otherwise, a gas chamber mixed ratio abnormal alarm is issued.

6. The method of claim 1, wherein the method further comprises: determining whether the humidity sensor is operating properly based on the comparison. The verification method further comprises: heating the calibration chamber; during the heating process, the actual pressure in the calibration chamber and the measured pressure read by the pressure sensor of the density relay are compared in real time, and the density relay is verified by pressure.

7. A calibrating device for a mixed gas density relay with a humidity detecting function, characterized in that, Comprise: The calibration chamber comprises a first temperature sensor, a first pressure sensor, a semiconductor refrigerator, and an optical monitoring assembly; The first temperature sensor and the first pressure sensor are used to detect the actual temperature and the actual pressure in the calibration chamber; the semiconductor refrigerator is used to adjust the temperature in the calibration chamber; the optical monitoring assembly is used to form light and monitor the light energy value of the light after acting on the calibration chamber; the calibration chamber is connected with the density relay; The control assembly is used to control the semiconductor refrigerator to cool the calibration chamber, and the pressure values of the first pressure sensor of the calibration chamber and the second pressure sensor of the density relay are collected to perform pressure reduction calibration; the light energy value of the optical monitoring assembly is monitored to obtain multiple change rates, and the mixed gas in the calibration chamber is sequentially subjected to humidity detection and mixed ratio detection.

8. The calibrating device of the mixed gas density relay with the humidity detecting function according to claim 7, characterized in that, The optical monitoring assembly comprises a light emitting tube, a light receiving tube and a mirror surface; the light emitting tube and the light receiving tube are horizontally and oppositely installed on the inner walls of the two sides of the calibration chamber, and the mirror surface is installed on the bottom of the inner surface of the calibration chamber and is used to reflect the light emitted by the light emitting tube to the light receiving tube to form a folded light path.

9. The calibrating device of the mixed gas density relay with the humidity detecting function according to claim 8, characterized in that, The first temperature sensor of the calibration chamber is installed below and close to the mirror surface.

10. The calibrating device of the mixed gas density relay with the humidity detecting function according to claim 7, characterized in that, The calibration chamber has a circular truncated cone structure, and the cross section thereof gradually decreases from top to bottom; the outer wall of the calibration chamber is made of metal; and the semiconductor refrigerator is installed on the outer wall at the bottom of the calibration chamber.

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