A method and system for spectroscopic detection of SF6 decomposition products

Abstract

The application provides a SF6 decomposition product spectrum detection method and system, adaptive adjustment of a sampling amount is performed through a variable volume structure, a gas-liquid two-phase dissolution compensation and concentration full amount calculation model is constructed, the liquefaction volume of SF6 in each sample is ensured to be greater than a set threshold in a liquefaction enrichment process, and the theoretical solubility of SF6 in a liquid phase is calculated by combining the concentration of the upper gas phase with the partial pressure and the fugacity through spectrum detection; a solubility dynamic correction model is constructed by using a neural network, the solubility loss is compensated by performing theoretical prediction and actual correction based on the dissolution behavior of the decomposition product in the liquefaction process; and then the mass and solubility information of SF6 in the gas phase and the liquid phase in the enrichment process are comprehensively considered, so that the total concentration of the SF6 decomposition product in the gas chamber to be detected is detected; the volume of the tank body is adaptively adjusted through a piston structure, the representative gas amount that does not affect the safety of the equipment can be obtained under different gas chamber scales, and the concentration of the gas decomposition product can be safely and accurately detected.

Description

Technical Field

[0001] This invention relates to the field of detection technology, and in particular to a method and system for the spectral detection of SF6 decomposition products. Background Technology

[0002] In high-voltage power equipment, sulfur hexafluoride (SF6) gas is widely used as an insulating medium in various gas chambers. To ensure the safe and stable operation of the equipment, it is necessary to monitor trace decomposition products in SF6 gas to diagnose potential insulation defects. Currently, the detection of decomposition products mainly adopts a combination of offline sampling and laboratory analysis. The core step is to liquefy and concentrate the gas sample using an enrichment device to improve detection sensitivity.

[0003] However, existing detection systems face the following prominent contradictions in practical applications: Power equipment gas chamber volumes vary significantly, ranging from hundreds of liters for GIS busbars to just a few liters for circuit breaker chambers, all requiring regular gas testing. Existing enrichment sampling devices typically use fixed-volume enrichment tanks, with a constant gas sampling volume each time, making it difficult to adapt to the sampling requirements of gas chambers of different sizes. For large gas chambers, a fixed sampling volume that is too small will result in unrepresentative gas samples, potentially missing local fault information; for small gas chambers, the same sampling volume can easily cause a significant drop in internal pressure, affecting the normal operation and safety of the equipment. Therefore, traditional fixed-volume enrichment schemes have limitations in overall system adaptability, making it difficult to simultaneously meet the dual requirements of sampling representativeness and operational safety for gas chambers of different volumes.

[0004] Furthermore, during the enrichment process, some decomposition products dissolve in liquefied SF6, and the dissolution behavior under a fixed sampling amount is difficult to quantify accurately. If only the gaseous decomposition products are detected and the original concentration is calculated accordingly, without compensating for the dissolved portion in the liquid phase, the detection results will deviate from the true value, affecting the accuracy of fault diagnosis.

[0005] To address the issues of poor overall equipment compatibility and uncorrected dissolution losses, there is an urgent need for a sampling and testing scheme that can adapt to different gas chamber volumes and accurately calculate total decomposition products, thereby improving the reliability and coverage of SF6 insulation equipment condition monitoring.

[0006] To address this, this invention proposes a variable-volume method for sampling, detecting, and calculating SF6 decomposition products. This invention utilizes a piston structure to adaptively adjust the tank volume, ensuring representative gas sampling volumes without compromising equipment safety across different gas chamber sizes. The method first ensures that the liquefaction volume of SF6 exceeds a set value during each liquefaction enrichment process, and then detects the concentration of decomposition products in the upper gas layer. Next, combining the partial pressure and fugacity of the decomposition products in the gas phase, its solubility in the liquid SF6 is calculated. Finally, using prior experimental data and theoretical formulas, a neural network-corrected decomposition product solubility prediction model is constructed. Ultimately, by combining the volume and mass information of SF6 in both the gas and liquid phases, the total concentration of decomposition products in the SF6 in the test chamber is accurately calculated. Summary of the Invention

[0007] This invention proposes a method and system for spectral detection of SF6 decomposition products. By using a piston structure to achieve adaptive adjustment of the tank volume, it ensures that representative gas sampling volumes can be obtained without affecting equipment safety under different gas chamber sizes. It is suitable for safe and accurate detection of gas decomposition product concentrations in SF6 electrical equipment gas chambers of different volumes, especially in scenarios with large volume differences and stringent requirements for sampling safety and accuracy of total decomposition product measurement.

[0008] The present invention adopts the following technical solution.

[0009] A method for spectroscopic detection of SF6 decomposition products is disclosed. This method employs a piston-type variable-volume structure to adaptively adjust the sampling volume of the SF6 chamber under test, balancing the representativeness of the large chamber with the operational safety of the small chamber. Based on this, a gas-liquid two-phase dissolution compensation and total concentration calculation model is constructed. First, the liquefaction volume of SF6 during each sample liquefaction enrichment process is ensured to be greater than a set threshold. The theoretical solubility in the liquid phase is calculated by spectroscopic detection of the upper gas phase concentration and by combining partial pressure and fugacity. Further, based on experimental data and theoretical formulas, a dynamic solubility correction model is constructed using a neural network. This model compensates for dissolution losses by theoretically predicting and actually correcting based on the dissolution behavior of decomposition products during liquefaction. Finally, by integrating the mass and solubility information of SF6 in the gas and liquid phases during enrichment, the total concentration of SF6 decomposition products in the chamber under test is accurately inverted and detected. This method combines variable-volume sampling with dynamic dissolution compensation, solving the technical problems of existing fixed-volume enrichment tanks being unable to adapt to the needs of different sized chambers, the inability to dynamically match the gas sampling volume and enrichment factor, and measurement deviations caused by the dissolution loss of some decomposition products during liquefaction. It provides reliable technical support for the accurate diagnosis of insulation faults in SF6 electrical equipment.

[0010] An SF6 decomposition product spectral detection system employs the aforementioned SF6 decomposition product spectral detection method. The variable volume structure includes a piston-type variable volume enrichment tank for connecting to the SF6 gas chamber to be tested. The piston-type variable volume enrichment tank achieves continuous adjustment of the sampling volume within the tank through a piston structure, ensuring that the SF6 liquefaction volume is greater than a set threshold during each sampling and liquefaction process. In the piston running direction of the piston structure, the first piston air chamber (9-1) and the second piston air chamber (9-2) are respectively provided on both sides of the piston (10).

[0011] An external gas port (1) is provided at the beginning of the sampling gas path connecting the second piston gas chamber to the SF6 gas chamber under test. The opening and closing of the sampling gas path is controlled by the first solenoid valve (2-1) and the second solenoid valve (2-2) at the sampling gas path. A pressure sensor (4-1) and a temperature sensor (4-2) are provided at the sampling gas path. A first flow meter (3-1) is also provided to measure the amount of gas flowing into the first piston gas chamber from the SF6 gas chamber under test.

[0012] The second piston gas chamber is connected to the spectral detection chamber (7) via a cooled sample pipeline;

[0013] A motor (11) is provided at the second piston chamber, which drives the piston to move vertically via a connecting rod (12); the sampling process changes the volume of the first piston chamber by the vertical movement of the piston, and the total length of the second piston chamber after deducting the length of the piston is... And the cross-sectional area is ;

[0014] The connecting rod is located inside the first piston air chamber. An infrared ranging transmitter (8-1) is installed at the tail end of the connecting rod (12). An infrared ranging receiver (8-2) is located on the inner wall of the first piston air chamber in the direction of the infrared ranging transmitter's emission. The initial distance between the infrared ranging transmitter and the infrared ranging receiver is... The initial position is the position closest to the infrared ranging transmitter and the infrared ranging receiver.

[0015] During the liquefaction process of spectral detection, the sampling gas in the second piston gas chamber is stably cooled during the sampling stage by the first weak cooling temperature control module (13-1) and the second weak cooling temperature control module (13-2) located at the second piston gas chamber. The cooling temperature is controlled at -30℃, and its error range is within ±1℃.

[0016] During the liquefaction process of spectral detection, the sampling gas in the spectral detection chamber is stably cooled during the detection stage by the first forced cooling temperature control module (6-1) and the second forced cooling temperature control module (6-2) located in the spectral detection chamber. The cooling temperature is controlled at -45℃, and its error range is within ±1℃.

[0017] A third solenoid valve (2-3) is installed at the cooling sample pipeline;

[0018] The spectral detection chamber is connected to the cooling sample pipeline via a sample input pipeline; the main branch of the sample input pipeline is equipped with a third solenoid valve (2-3), and the sample input pipeline is equipped with a second flow meter (3-2).

[0019] The pipes of the detection system are polished to minimize the accumulation of decomposition products and other gases on the pipe walls.

[0020] When the detection system performs the enrichment and sampling detection of SF6 gas decomposition products, the specific process includes the following steps for different sizes of SF6 gas chambers to be tested.

[0021] Step a, preliminary preparation, specifically: turn on the motor, and use the connecting rod to drive the piston back to the position where the infrared ranging transmitter and the infrared ranging receiver are closest to each other;

[0022] Open the first solenoid valve, the second solenoid valve, and the third solenoid valve. Connect the vacuum pump through the external air port to evacuate the detection system to a vacuum state. Then close the first solenoid valve, the second solenoid valve, and the third solenoid valve to complete the preliminary preparation.

[0023] Turn on the first and second weak cooling temperature control modules to stabilize the cooling temperature of the second piston gas chamber at or near -30℃; turn on the first and second forced cooling temperature control modules to stabilize the cooling temperature of the spectral detection chamber at or near -45℃.

[0024] Step b: Obtain the volume of the SF6 gas chamber to be tested: Adjust the volume of the variable volume enrichment tank according to the volume of the electrical gas chamber to be tested, and take gas samples.

[0025] Step c: Based on the volume of the SF6 gas chamber to be measured Determine the gas sampling time :

[0026] Step d: Change the volume of the second piston gas chamber to increase the volume of liquefied SF6. , Minimum SF6 liquefaction volume: Partial liquefaction of the sampled SF6 gas is performed to ensure that the volume of liquid SF6 is greater than the set value. ;

[0027] Step e: Detection of SF6 gas decomposition product concentration; Detect and obtain the partial pressure or concentration of decomposition products in the upper gas after gas-liquid equilibrium using spectrophotometry.

[0028] Step f: Calculation of the concentration of decomposition products of the cooled and liquefied liquid SF6 gas; Based on the partial pressure or concentration, calculate the theoretical solubility of the decomposition products in liquid SF6.

[0029] Step g: Calculate and correct the solubility of liquid SF6 decomposition products based on experimental data; input the theoretical solubility and related parameters into the pre-trained neural network correction model to obtain the corrected solubility prediction value;

[0030] Step h: Calculate the concentration of SF6 gas decomposition products in the SF6 gas chamber to be tested; based on the corrected solubility prediction value, and the volume and mass of SF6 in the gas phase and liquid phase, calculate the total concentration of decomposition products in the original SF6 gas.

[0031] Step i, post-detection processing, specifically: First, start the motor, and drive the piston back to its initial position via the connecting rod. Then, turn off the motor, the first forced cooling temperature control module, the second forced cooling temperature control module, the first weak cooling temperature control module, and the second weak cooling temperature control module. Wait for the liquid SF6 in the second piston gas chamber to vaporize. Then, open the first solenoid valve and the second solenoid valve, start the motor, and drive the piston to move to the left to the outermost end of the second piston gas chamber via the connecting rod to refill the SF6 gas chamber in the second piston gas chamber into the SF6 gas chamber to be tested. Finally, close the first solenoid valve and the second solenoid valve; start the motor, drive the piston back to its initial position via the connecting rod, and turn off the motor to complete all detections.

[0032] Step b specifically involves: To avoid the risk of pressure sensor reading deviations caused by gas flow, resulting in the gas chamber pressure falling below the alarm value, when determining the gas intake volume through pressure drop, the volume of the SF6 gas chamber to be tested can be calculated first, and then the safe gas intake volume can be determined accordingly; specifically:

[0033] First, calculate the gas density of the SF6 chamber at the initial moment. Connect the SF6 gas chamber to be tested to the detection device via an external gas port, open the first solenoid valve, and record the initial pressure value of the SF6 gas chamber to be tested using a pressure sensor. The temperature sensor records the initial temperature value of the SF6 gas chamber under test. Calculate the initial density value at this time. for:

[0034] Formula 1;

[0035]

[0036]

[0037]

[0038] in, The initial pressure value of the SF6 gas chamber to be tested; The initial temperature value of the SF6 gas chamber to be tested; It is the gas constant; These are the parameters corresponding to the gravitational effect; The parameter corresponding to molecular volume / repulsion force;

[0039] Since the content of decomposition products is very low, the calculated gas density can be considered to be equal to that of SF6, and the same applies below.

[0040] Secondly, the density of SF6 gas after a portion of the SF6 gas flows from the SF6 chamber to the second piston chamber and passes through the flow meter is calculated. and the density of SF6 gas in the SF6 chamber to be tested ;

[0041] Then open the second solenoid valve to allow the mixture of SF6 gas and SF6 decomposition products in the SF6 gas chamber to enter the second piston chamber. The first flow meter records the volume of gas flowing from the SF6 gas chamber to the second piston chamber 9-2 per unit time. When the pressure in the test chamber drops to a predetermined threshold (which is much smaller than the alarm pressure drop value), the elapsed time is recorded. Then, the second solenoid valve is closed, and the gas density flowing through the first flow meter is calculated. :

[0042] Formula 2;

[0043]

[0044]

[0045]

[0046] in, The pressure value under operating conditions when the flow rate is recorded by the flow meter. ; The operating temperature value at which the flow rate is recorded by the flow meter. ; It is the gas constant; These are parameters related to gravitational effects; A parameter related to molecular volume / repulsion.

[0047] When the flow meter records the flow rate as the volume of water flowing through the system at 0℃ and 0.1 MPa, then ;

[0048] The pressure value of the SF6 gas chamber under test is recorded by pressure sensor (4-1). Temperature sensor (4-2) records the temperature value of the SF6 gas chamber to be tested. Then close solenoid valve 2-1 and calculate the density value at this time. for:

[0049] Formula 3;

[0050]

[0051]

[0052]

[0053] in, The pressure value of the SF6 gas chamber to be measured after a portion of the gas enters the second piston chamber from the gas chamber to be measured.

[0054] The temperature of the SF6 gas chamber being measured is the value after a portion of the gas enters the second piston chamber from the gas chamber being measured.

[0055] It is the gas constant;

[0056] These are the parameters corresponding to the gravitational effect;

[0057] The parameter corresponding to molecular volume / repulsion force;

[0058] Based on the law of conservation of mass, we can conclude that:

[0059] Formula 4;

[0060] in, The initial density value of the SF6 gas chamber to be tested is obtained by formula 1;

[0061] The density of the gas flowing through the first flow meter is calculated using formula 2;

[0062] The gas density value of the SF6 gas chamber to be tested after part of the gas enters the second piston gas chamber from the gas chamber to be tested is calculated by formula 3.

[0063] To record the elapsed time after the pressure in the test chamber drops to a certain threshold (which is much smaller than the alarm pressure drop value);

[0064] The volume of gas flowing from the SF6 chamber under test into the second piston chamber per unit time, as recorded by the first flow meter;

[0065] The volume of the SF6 gas chamber to be measured is the result obtained through calculation, as shown in Formula 5;

[0066] Thus, the volume of the SF6 gas chamber to be measured can be obtained. for:

[0067] Formula 5.

[0068] Step c specifically involves: opening the first and second solenoid valves, based on the SF6 gas chamber volume obtained in step b. The volume of gas flowing in per unit time is recorded by the first flow meter. At this point, the sampling time for the second SF6 gas sample taken from the chamber to be tested is determined. The calculation method is as follows:

[0069] ① Record the initial pressure value of the SF6 gas chamber to be tested Temperature sensor (4-2) records the initial temperature value of the SF6 gas chamber under test. The initial density value of the SF6 gas chamber to be tested can then be calculated using Formula 1. ;

[0070] ② Calculate the pressure drop (The pressure drop must be less than the alarm pressure) the density value of the gas chamber to be measured. The temperature at this stage is the average of the two temperature measurements taken in step b. The calculation is as follows:

[0071] Formula 6;

[0072]

[0073]

[0074]

[0075] in, The pressure value of the SF6 gas chamber to be measured after a portion of the gas enters the second piston chamber from the gas chamber to be measured. This represents the maximum pressure drop during the second gas extraction. The initial temperature value of the SF6 gas chamber to be tested; The temperature of the SF6 gas chamber being measured is the value after a portion of the gas enters the second piston chamber from the gas chamber being measured. This is the average of two temperature measurements; It is the gas constant; These are the parameters corresponding to the gravitational effect; The parameter corresponds to the molecular volume / repulsion force.

[0076] ③ Calculate the gas intake :

[0077] Formula 7;

[0078] in, The initial density value of the SF6 gas chamber to be tested is obtained by formula 1; For the second gas extraction, pressure drop The density value of the gas chamber to be tested after the pressure drop is less than the alarm pressure is calculated by formula 6;

[0079] ④ Calculate the gas sampling time :

[0080] Formula 8;

[0081] in, The density of the gas flowing through the flow meter is calculated using formula 2; The gas intake is calculated using formula 7; The first flow meter records the volume of gas flowing from the SF6 chamber under test into the second piston chamber per unit time.

[0082] When the sampling time has elapsed Then close the first and second solenoid valves to complete the gas sampling.

[0083] Step d specifically involves the following: the sampled gas enters the second piston chamber and begins to liquefy.

[0084] If the SF6 gas chamber to be tested is a small chamber, the gas intake will be small. In this case, the piston moves via the motor and connecting rod, thereby reducing the volume of the second piston chamber and increasing the gas pressure in the second piston chamber. This improves the liquefaction degree of SF6 gas and increases the enrichment rate of SF6 gas decomposition products. The adjusted volume of the second piston chamber depends on the liquefaction degree of SF6 gas, and the specific method for determining it is as follows:

[0085] ① After a preset set time, open the second solenoid valve and record the gas pressure in the second piston chamber using a pressure sensor. The gas temperature in the second piston chamber is recorded by a temperature sensor. Calculated based on the SF6 liquefaction formula:

[0086] Formula 9;

[0087] in, Based on temperature The calculated pressure value of gaseous SF6 at the theoretical liquefaction state under gas-liquid equilibrium. After a predetermined period of time (which can be considered as the time when the liquefaction gas and liquid are in equilibrium) has started, the temperature sensor records the gas temperature in the second piston gas chamber.

[0088] like The gas pressure in the second piston chamber... The theoretically calculated pressure value of gaseous SF6 in liquefied state at gas-liquid equilibrium. If the values ​​are equal, it indicates that the initial liquefaction of the sample gas has been completed;

[0089] ② To calculate the volume of liquefied SF6 at this point, first calculate the density of the gaseous SF6 at this point. for:

[0090] Formula 10

[0091]

[0092]

[0093]

[0094] in, When the liquefied gas is in equilibrium, the pressure sensor records the gas pressure in the second piston gas chamber; The temperature of the gas in the second piston chamber is recorded by the temperature sensor after a predetermined period of time (which can be considered as the time when the liquefaction gas and liquid are in equilibrium).

[0095] It is the gas constant; These are parameters related to gravitational effects; These are parameters related to molecular volume / repulsion.

[0096] Given that when the piston is in the initial position, the volume of the second piston chamber is... At this point, when the liquefied gas and liquid are in equilibrium, the volume of gaseous SF6 gas is... have:

[0097] Formula 11;

[0098] in, The density of SF6 liquid is given. Since the liquid density changes very little with temperature, it is assumed that... It is a constant value; The density value of gaseous SF6 gas at liquefied gas-liquid equilibrium; The length of the second piston chamber after subtracting the length of the piston from the total length of the second piston chamber; This represents the cross-sectional area of ​​the second piston chamber. The gas intake is calculated using formula 7;

[0099] Thus, the volume of liquefied SF6 can be calculated. for:

[0100] Formula 12;

[0101] in, The density of SF6 liquid is given. Since the liquid density changes very little with temperature, it is assumed that... It is a constant value; The density value of gaseous SF6 gas at liquefied gas-liquid equilibrium; The length of the second piston chamber after subtracting the length of the piston from the total length of the second piston chamber; This represents the cross-sectional area of ​​the second piston chamber. This represents the volume of gaseous SF6 gas at liquefied gas-liquid equilibrium. The gas intake is calculated using formula 7;

[0102] If the volume of liquefied SF6 at this time ,in To achieve the lowest liquefied SF6 volume, it is not necessary to turn on the motor; the volume of the second piston gas chamber 9-2 is changed by the connecting rod and piston.

[0103] If the volume of liquefied SF6 at this time Then the motor is turned on, and the volume of the second piston chamber is changed through the connecting rod and piston, thereby increasing the volume of liquefied SF6 to reach the minimum liquefied SF6 volume. The method for determining the piston movement distance is as follows:

[0104] Since the first weak cooling temperature control module 16-1 and the second weak cooling temperature control module 16-2 can achieve stable cooling, the temperature of the second piston gas chamber 9-2 will not change significantly and can be considered constant.

[0105] Based on Equation 9, when the temperature remains constant, the pressure of SF6 gas in equilibrium remains unchanged, and is still [value missing]. Therefore, the density value of SF6 gas in equilibrium remains unchanged. Therefore, the volume of SF6 gas for:

[0106] Formula 13;

[0107] in, The density of SF6 liquid is given. Since the liquid density changes very little with temperature, it is assumed that... It is a constant value; The density value of gaseous SF6 gas at liquefied gas-liquid equilibrium; The minimum liquefied SF6 liquid volume (set value); The gas intake is calculated using formula 7;

[0108] At this time, the volume of the second piston air chamber for:

[0109] Formula 14;

[0110] in, The minimum liquefied SF6 liquid volume (set value); The volume of gaseous SF6 gas after the second piston chamber volume is changed is calculated using formula 13.

[0111] To obtain the downward distance that the piston and connecting rod need to move. for:

[0112] Formula 15;

[0113] in, The length after subtracting the piston length from the total length of the second piston chamber; This represents the cross-sectional area of ​​the second piston chamber. The volume of the second piston chamber after the volume of the second piston chamber is changed by the piston;

[0114] Based on an infrared ranging transmitter and receiver, the downward distance of the connecting rod is recorded. When the downward distance is... The motor is controlled to stop moving the connecting rod and piston, completing the volume change of the second piston chamber; the mass of the liquid at this time is recorded. :

[0115] Formula 16;

[0116] in, The minimum liquefied SF6 liquid volume (set value); Before the piston changes the volume of the second piston chamber, the volume of SF6 liquid at the point of liquefied gas-liquid equilibrium is calculated using formula 12.

[0117] The density of SF6 liquid is given. Since the liquid density changes very little with temperature, it is assumed that... It is a constant value;

[0118] Record the mass of the gas at this time as :

[0119] Formula 17;

[0120] in, Before the piston changes the volume of the second piston chamber, the volume of gaseous SF6 gas at the liquefied gas-liquid equilibrium is calculated using formula 11. The volume of gaseous SF6 gas after the second piston chamber volume is changed is calculated using formula 13. This represents the density of gaseous SF6 gas at liquefied gas-liquid equilibrium.

[0121] Step e is as follows: First, close the second solenoid valve and let it stand for a period of time to ensure that the gas-liquid mixture in the second piston gas chamber reaches a state of equilibrium; then open the third solenoid valve; the cooling temperature of the first forced cooling temperature control module (6-1) and the second forced cooling temperature control module (6-2) is lower than the cooling temperature of the first weak cooling temperature control module (13-1) and the second weak cooling temperature control module (13-2), and the SF6 gas and its decomposition products in the second piston gas chamber enter the spectral detection chamber (7), and the volume of the gas flowing in per unit time is recorded by the second flow meter. After time Then, the third solenoid valve is closed, and the concentration of SF6 gas decomposition products flowing into the spectral detection chamber for the first time is detected by the spectral detection transmitter (5-1) and the spectral detection receiver (5-2). The mass of the gas entering the spectral detection chamber at this time for

[0122] Formula 18;

[0123] in, The second flow meter records the volume of gas flowing from the second piston gas chamber to the spectral detection chamber per unit time. The density of the gas flowing through the second flow meter is calculated by formula 2. Since the flow rate recorded by the flow meter is the volume of gas flowing through the flow at 0℃ and 0.1MPa, the density of the gas flowing through the second flow meter 3-2 can be considered to be equivalent to the density of the gas flowing through the first flow meter 3-1. The time it takes for the gas to flow from the second piston gas chamber to the spectral detection chamber;

[0124] Since the flow rate recorded by the flow meter is the volume of gas flowing under conditions of 0℃ and 0.1 MPa, the gas density here is consistent with the density in Formula 2. .

[0125] Based on the concentration of SF6 gas decomposition products The mass of SF6 gas decomposition products entering the spectral detection chamber from the second piston gas chamber was calculated. and SF6 gas mass :

[0126] Formula 19;

[0127] in, The concentration of SF6 gas decomposition products was detected by the spectrometer receiver during the first flow into the spectrometer detection chamber. The density of the gas flowing through the second flow meter is calculated by formula 2. Since the flow rate recorded by the flow meter is the volume of gas flowing through the flow meter at 0℃ and 0.1 MPa, the density of the gas flowing through flow meter 3-2 can be considered to be equal to the density of the gas flowing through flow meter 3-1.

[0128] The time it takes for the gas to flow from the second piston gas chamber to the spectral detection chamber; The mass of the gas entering the spectral detection chamber is calculated using Formula 18.

[0129] Step f specifically involves calculating the mass of SF6 gas decomposition products from the results of steps a through e. and SF6 gas mass The gas phase partial pressures of the SF6 gas decomposition products were calculated. Specifically:

[0130] Formula 20;

[0131] in, When the liquefied gas is in equilibrium, the pressure sensor records the gas pressure in the second piston gas chamber; The molar mass of SF6; The molar mass of the decomposition products of SF6 gas; The mass of the SF6 gas decomposition products is calculated using formula 19; The mass of SF6 gas is calculated using formula 19;

[0132] Since the amount of SF6 gas decomposition products is very small, the solubility of SF6 gas decomposition products in liquid SF6 is calculated based on the principles of chemical thermodynamics and the Beattie-Bridgman assay. Under equilibrium conditions, the fugacity of SF6 gas decomposition products in liquid SF6 is also calculated. Harmony and harmony They are equal, expressed by the formula:

[0133] Formula 21;

[0134] in, The fugacity of SF6 gas decomposition products in gaseous SF6; This represents the fugacity of SF6 gas decomposition products in liquid SF6.

[0135] The gas phase fugacity is expressed as:

[0136] Formula 22;

[0137] in, The mole fraction of SF6 gas decomposition products in gaseous SF6 is calculated using formula 23; The fugacity coefficient of the SF6 gas decomposition products in gaseous SF6 is calculated by formula 24; The partial pressure of the gas phase of the SF6 gas decomposition products is calculated using formula 20; where, The mole fraction of SF6 gas decomposition products in SF6 gas is calculated as follows:

[0138] Formula 23;

[0139] in, When the liquefied gas is in equilibrium, the pressure sensor records the gas pressure in the second piston gas chamber; The partial pressure of the gas phase of the SF6 gas decomposition products is calculated using formula 20;

[0140] The fugacity coefficient of the SF6 gas decomposition products in gaseous SF6 is calculated as follows:

[0141] Formula 24;

[0142] Where Z is the compressibility factor of the SF6 gas decomposition products; The volume of gaseous SF6 (the volume of gaseous SF6 gas when the liquefied gas-liquid equilibrium is taken into account in the calculation). (Calculated by formula 12) This refers to the amount of substance of the decomposition products of SF6 gas. Here, T is the gas constant; T is the temperature (the temperature at which the liquefied gas-liquid equilibrium is taken into account during the calculation). (i.e., the temperature in Formula 9).

[0143] Fugacity of SF6 gas decomposition products in liquid SF6 Represented as:

[0144] Formula 25;

[0145] in, This represents the mole fraction of SF6 gas decomposition products in liquid SF6. The fugacity coefficient of the SF6 gas decomposition products in liquid SF6 is calculated using formula 26. The partial pressure of the gas phase of the SF6 gas decomposition products is calculated using formula 20;

[0146] in, The fugacity coefficient of the decomposition products of SF6 gas in liquid SF6 is calculated as follows:

[0147] Formula 26;

[0148] Where Z is the compressibility factor of the SF6 gas decomposition products; The volume of liquid SF6 (the volume of liquid SF6 gas during the liquefied gas-liquid equilibrium calculation). (Calculated by formula 12) This refers to the amount of substance of the decomposition products of SF6 gas. It is the gas constant; Temperature (the temperature at which the liquefied gas-liquid equilibrium is input during calculation) (i.e., the temperature in Formula 9).

[0149] Calculate using formulas 21 to 26 :

[0150] Formula 27.

[0151] Step g specifically involves: deriving the theoretically calculated solubility of SF6 decomposition products in liquid SF6 from the calculation results of steps a-f. To further ensure the accuracy of the solubility, the experimentally obtained solubility of SF6 decomposition products in liquid SF6 is introduced for correction, thus establishing a more reasonable calculation model for the solubility of SF6 decomposition products in liquid SF6. The experiment involves liquefying SF6 gas mixed with a predetermined proportion of SF6 decomposition products, detecting the concentration of SF6 decomposition products in the upper gas layer, and then calculating the theoretically calculated solubility of SF6 decomposition products in liquid SF6 under the experimental conditions using the method described in step f. The volume of liquid SF6 Volume of gaseous SF6 partial pressure of the gas phase of SF6 decomposition products Total gas pressure Theoretical calculations of the solubility of SF6 decomposition products in liquid SF6 liquefaction temperature As input, that is: The solubility of SF6 decomposition products in liquid SF6 obtained from the experiment. As output quantity ; thereby constructing the global input matrix With output ;

[0152] The model is trained based on a residual neural network with physical constraints, and the calculations for each layer are as follows:

[0153] Layer 0, Input Layer: Formula 28;

[0154] First layer: Formula 29;

[0155] Second layer: Formula 30;

[0156] Third layer: Formula 31;

[0157] Fourth layer, output layer: Formula 32;

[0158] Finally, the predicted solubility of SF6 decomposition products in [the solution] was obtained. for: Formula 33;

[0159] in, , , , These are the weights for the first, second, third, and fourth layers, respectively. This means taking the absolute value of all weights in the fourth layer and assigning it back. middle; , , , These are the offsets for the first, second, third, and fourth layers, respectively. This is an activation function with the following rule: if the number in the parentheses is greater than or equal to 0, output it as is; if the number in the parentheses is less than 0, output 0, so that all data are in the non-negative value region. , , These are the outputs of the first, second, and third hidden layers, respectively. This represents the deviation between theoretically calculated values ​​and experimental values ​​based on model predictions.

[0160] Based on formula 33, the mass concentration of the decomposition products of liquid SF6 gas is calculated as follows: :

[0161] Formula 34;

[0162] in, The solubility of SF6 decomposition products in the solution was calculated using Equation 33. The molar mass of SF6; This represents the molar mass of the decomposition products of SF6 gas.

[0163] In step h, the mass concentration of the gaseous SF6 decomposition products actually detected in step e is: The mass concentration of the liquid-phase SF6 gas decomposition products was calculated through steps f and g. The concentration of SF6 gas decomposition products in the second piston chamber was calculated using formulas 16 and 17. for:

[0164] Formula 35;

[0165] in, The concentration of SF6 gas decomposition products was detected by the spectrometer receiver during the first flow into the spectrometer detection chamber. The mass concentration of the decomposition products of liquid SF6 gas is calculated using formula 34; The mass of liquid in the second piston gas chamber when the liquefied gas is in equilibrium is calculated using formula 16. The mass of gas in the second piston chamber at liquefied gas-liquid equilibrium is calculated using formula 17; the concentration of SF6 gas decomposition products in the second piston chamber 9-2 is... Similarly, the concentration of SF6 gas decomposition products in the SF6 gas chamber to be measured is combined with the density in Formula 1. And the volume of the SF6 gas chamber to be measured in Formula 5 The total mass of SF6 gas decomposition products in the SF6 gas chamber to be tested was obtained. for:

[0166] Formula 36;

[0167] in, To calculate the concentration of SF6 gas decomposition products in piston chamber 9-2 (i.e., to measure the concentration of SF6 gas decomposition products in the SF6 chamber), it is calculated using formula 35; The initial density value of the SF6 gas chamber to be tested is calculated using formula 3; The volume of the SF6 gas chamber to be measured is the result that needs to be calculated, obtained by formula 5.

[0168] This invention provides an SF6 decomposition product metering device and method based on variable volume sampling for concentration detection and liquid-phase solubility compensation. The core of this method lies in achieving adaptive adjustment of the sampling volume through a piston-type variable volume structure, balancing the representativeness of the large gas chamber with the operational safety of the small gas chamber. Based on this, a gas-liquid two-phase solubility compensation and total concentration calculation model is constructed. First, the liquefaction volume of SF6 during each liquefaction enrichment process is ensured to be greater than a set value. Then, the concentration of the upper gas phase is detected by spectral analysis, and its theoretical solubility in the liquid phase is calculated by combining partial pressure and fugacity. Further, based on experimental data and theoretical formulas, a dynamic solubility correction model is constructed using a neural network. Based on the dissolution behavior of decomposition products during liquefaction, theoretical predictions and actual corrections are performed to compensate for dissolution losses. Finally, by integrating the mass and solubility information of SF6 in the gas and liquid phases during the enrichment process, the total concentration of SF6 decomposition products in the test chamber is accurately retrieved. This invention combines variable volume sampling with dynamic dissolution compensation to solve the technical problems of existing fixed-volume enrichment tanks, which are difficult to adapt to the needs of gas chambers of different sizes, cannot dynamically match the gas sampling volume with the enrichment factor, and suffer from measurement deviations due to the dissolution loss of some decomposition products during liquefaction. It provides reliable technical support for the accurate diagnosis of insulation faults in SF6 electrical equipment.

[0169] The SF6 gas decomposition product sampling device and method based on piston-type variable volume enrichment and gas-liquid two-phase calibration provided by this invention have the following significant advantages:

[0170] 1) Through the piston-type variable volume structure, the sampling volume can be intelligently adjusted according to the actual volume of the gas chamber to be tested. For large gas chambers, the gas sampling volume can be increased to ensure the representativeness of the gas sample and avoid missed faults; for small gas chambers, the gas sampling volume can be reduced accordingly to avoid a significant drop in gas chamber pressure due to excessive extraction, thus ensuring the safe and stable operation of the equipment.

[0171] In the variable volume adaptive sampling mechanism, a piston-type variable volume enrichment tank structure is adopted, combined with gas chamber volume identification and sampling volume control algorithms, to automatically match a safe and representative gas sampling volume according to different gas chamber sizes. The key technologies lie in the stability control of continuous volume adjustment and the matching model of gas sampling volume and gas chamber volume.

[0172] 2) An innovative gas-liquid two-phase dissolution compensation model is constructed to systematically correct detection deviations caused by the dissolution of some decomposition products in liquid SF6 during liquefaction. Based on the detected gas phase concentration, the theoretical solubility is calculated by combining parameters such as partial pressure and fugacity. A dynamic correction model optimized by a neural network is introduced to achieve high-precision prediction of the amount of liquid phase dissolution. This compensation mechanism significantly reduces the concentration underestimation problem caused by dissolution loss, making the final calculated total concentration of decomposition products closer to the true value.

[0173] In the gas-liquid two-phase dissolution dynamic compensation method, based on the concentration of gas phase decomposition products detected by spectrometry, the solubility of decomposition products in liquid SF6 is theoretically calculated based on partial pressure, fugacity and liquefaction conditions. A neural network model trained with experimental data is then introduced for dynamic correction to achieve accurate compensation for dissolution loss.

[0174] 3) The device and method can be flexibly adapted to SF6 gas chambers of different volumes, without the need to configure special sampling tools for different equipment, which significantly improves the versatility and standardization of the detection system and is conducive to its promotion and implementation in field testing.

[0175] The system integration and automated process control described in this invention integrates variable volume regulation, gas-liquid two-phase spectroscopic detection, dynamic dissolution compensation, and concentration inversion into a unified control unit, achieving fully automated operation from parameter input and adaptive sampling to final concentration output. It features time-series coordination among modules, reliable data interaction, and convenient human-machine interaction.

[0176] 4) The system organically combines variable volume sampling, two-phase concentration detection, dynamic dissolution compensation, and total concentration inversion to form a complete, closed-loop detection process. It supports automatic volume matching based on chamber parameters, dynamic model correction based on real-time data, and automatic calculation and output of the final concentration, significantly reducing operational complexity and human error.

[0177] In the full concentration inversion model, a comprehensive concentration calculation model is established that includes multiple parameters such as the mass, volume, and solubility of SF6 in both the gas and liquid phases. By incorporating the compensated solubility into the total concentration calculation, a high-precision inversion from limited sampling to the concentration in the entire gas chamber is achieved.

[0178] In summary, this invention, while ensuring sampling safety and equipment compatibility, achieves highly representative and accurate gas sampling and concentration detection for gas chambers of different sizes through dynamic dissolution compensation and full concentration inversion, while ensuring safe equipment operation. This provides a more reliable, universal, and efficient detection solution for insulation fault diagnosis of SF6 electrical equipment. Attached Figure Description

[0179] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0180] Appendix Figure 1 This is a hardware schematic diagram of an SF6 gas enrichment sampling and detection system applicable to different sized gas chambers in an embodiment of the present invention.

[0181] In the diagram: external air inlet (1); first solenoid valve (2-1); second solenoid valve (2-2); third solenoid valve (2-3); first flow meter (3-1); second flow meter (3-2);

[0182] Pressure sensor (4-1); Temperature sensor (4-2); Spectral detection transmitter (5-1); Spectral detection receiver (5-2); First forced cooling temperature control module (6-1); Second forced cooling temperature control module (6-2); Spectral detection chamber (7) 11; Infrared ranging transmitter (8-1); Infrared ranging receiver (8-2); First piston air chamber (9-1); Second piston air chamber (9-2); Piston (10); Motor (11); Connecting rod (12); First cooling temperature control module (13-1); Second cooling temperature control module (13-2) Detailed Implementation

[0183] like Figure 1 As shown, a method for the spectral detection of SF6 decomposition products is presented. This method uses a piston-type variable volume structure to adaptively adjust the sampling volume of the SF6 chamber under test, balancing the representativeness of the large chamber and the operational safety of the small chamber. Based on this, a gas-liquid two-phase dissolution compensation and total concentration calculation model is constructed. First, the liquefaction volume of SF6 during each sample liquefaction enrichment process is ensured to be greater than a set threshold. The concentration of the upper gas phase is detected by spectral analysis, and its theoretical solubility in the liquid phase is calculated by combining partial pressure and fugacity. Further, based on experimental data and theoretical formulas, a dynamic solubility correction model is constructed using a neural network. The dissolution behavior of the decomposition products during liquefaction is used for theoretical prediction and actual correction to compensate for dissolution losses. Finally, by integrating the mass and solubility information of SF6 in the gas and liquid phases during the enrichment process, the total concentration of SF6 decomposition products in the chamber under test is accurately inverted and detected. The proposed method combines variable volume sampling with dynamic dissolution compensation, addressing the technical challenges of existing fixed-volume enrichment tanks that cannot adapt to the needs of gas chambers of different sizes, the inability to dynamically match the gas sampling rate with the enrichment factor, and measurement deviations caused by the dissolution loss of some decomposition products during liquefaction. This provides reliable technical support for the accurate diagnosis of insulation faults in SF6 electrical equipment.

[0184] An SF6 decomposition product spectral detection system employs the aforementioned SF6 decomposition product spectral detection method. The variable volume structure includes a piston-type variable volume enrichment tank for connecting to the SF6 gas chamber to be tested. The piston-type variable volume enrichment tank achieves continuous adjustment of the sampling volume within the tank through a piston structure, ensuring that the SF6 liquefaction volume is greater than a set threshold during each sampling and liquefaction process. In the piston running direction of the piston structure, a first piston air chamber 9-1 and a second piston air chamber 9-2 are respectively provided on both sides of the piston 10;

[0185] An external gas port 1 is provided at the beginning of the sampling gas path connecting the second piston gas chamber to the SF6 gas chamber under test. The opening and closing of the sampling gas path is controlled by the first solenoid valve 2-1 and the second solenoid valve 2-2 at the sampling gas path. A pressure sensor 4-1 and a temperature sensor 4-2 are provided at the sampling gas path. A first flow meter 3-1 is also provided to measure the amount of gas flowing into the first piston gas chamber from the SF6 gas chamber under test.

[0186] The second piston gas chamber is connected to the spectral detection chamber 7 via a cooled sample pipeline;

[0187] A motor 11 is installed at the second piston chamber, which drives the piston to move vertically via a connecting rod 12; the sampling process changes the volume of the first piston chamber by the vertical movement of the piston, and the total length of the second piston chamber, excluding the length of the piston, is... And the cross-sectional area is ;

[0188] The connecting rod is located inside the first piston air chamber. An infrared ranging transmitter 8-1 is mounted at the tail end of the connecting rod 12. An infrared ranging receiver 8-2 is located on the inner wall of the first piston air chamber in the direction of the infrared ranging transmitter's emission. The initial distance between the infrared ranging transmitter and the infrared ranging receiver is... The initial position is the position closest to the infrared ranging transmitter and the infrared ranging receiver.

[0189] During the liquefaction process of spectral detection, the sampling gas in the second piston gas chamber is stably cooled during the sampling stage by the first weak cooling temperature control module 13-1 and the second weak cooling temperature control module 13-2 located at the second piston gas chamber. The cooling temperature is controlled at -30℃, and its error range is within ±1℃.

[0190] During the liquefaction process of spectral detection, the sampling gas in the spectral detection chamber is stably cooled during the detection stage by the first forced cooling temperature control module 6-1 and the second forced cooling temperature control module 6-2 located in the spectral detection chamber. The cooling temperature is controlled at -45℃, and its error range is within ±1℃.

[0191] A third solenoid valve 2-3 is installed at the cooling sample pipeline;

[0192] The spectral detection chamber is connected to the cooling sample pipeline via a sample input pipeline; the main branch of the sample input pipeline is equipped with a third solenoid valve 2-3, and the sample input pipeline is equipped with a second flow meter 3-2.

[0193] The pipes of the detection system are polished to minimize the accumulation of decomposition products and other gases on the pipe walls.

[0194] When the detection system performs the enrichment and sampling detection of SF6 gas decomposition products, the specific process includes the following steps for different sizes of SF6 gas chambers to be tested.

[0195] Step a, preliminary preparation, specifically: turn on the motor, and use the connecting rod to drive the piston back to the position where the infrared ranging transmitter and the infrared ranging receiver are closest to each other;

[0196] Open the first solenoid valve, the second solenoid valve, and the third solenoid valve. Connect the vacuum pump through the external air port to evacuate the detection system to a vacuum state. Then close the first solenoid valve, the second solenoid valve, and the third solenoid valve to complete the preliminary preparation.

[0197] Turn on the first and second weak cooling temperature control modules to stabilize the cooling temperature of the second piston gas chamber at or near -30℃; turn on the first and second forced cooling temperature control modules to stabilize the cooling temperature of the spectral detection chamber at or near -45℃.

[0198] Step b: Obtain the volume of the SF6 gas chamber to be tested: Adjust the volume of the variable volume enrichment tank according to the volume of the electrical gas chamber to be tested, and take gas samples.

[0199] Step c: Based on the volume of the SF6 gas chamber to be measured Determine the gas sampling time :

[0200] Step d: Change the volume of the second piston gas chamber to increase the volume of liquefied SF6. , Minimum SF6 liquefaction volume: Partial liquefaction of the sampled SF6 gas is performed to ensure that the volume of liquid SF6 is greater than the set value. ;

[0201] Step e: Detection of SF6 gas decomposition product concentration; Detect and obtain the partial pressure or concentration of decomposition products in the upper gas after gas-liquid equilibrium using spectrophotometry.

[0202] Step f: Calculation of the concentration of decomposition products of the cooled and liquefied liquid SF6 gas; Based on the partial pressure or concentration, calculate the theoretical solubility of the decomposition products in liquid SF6.

[0203] Step g: Calculate and correct the solubility of liquid SF6 decomposition products based on experimental data; input the theoretical solubility and related parameters into the pre-trained neural network correction model to obtain the corrected solubility prediction value;

[0204] Step h: Calculate the concentration of SF6 gas decomposition products in the SF6 gas chamber to be tested; based on the corrected solubility prediction value, and the volume and mass of SF6 in the gas phase and liquid phase, calculate the total concentration of decomposition products in the original SF6 gas.

[0205] Step i, post-detection processing, specifically: First, start the motor, and drive the piston back to its initial position via the connecting rod. Then, turn off the motor, the first forced cooling temperature control module, the second forced cooling temperature control module, the first weak cooling temperature control module, and the second weak cooling temperature control module. Wait for the liquid SF6 in the second piston gas chamber to vaporize. Then, open the first solenoid valve and the second solenoid valve, start the motor, and drive the piston to move to the left to the outermost end of the second piston gas chamber via the connecting rod to refill the SF6 gas chamber in the second piston gas chamber into the SF6 gas chamber to be tested. Finally, close the first solenoid valve and the second solenoid valve; start the motor, drive the piston back to its initial position via the connecting rod, and turn off the motor to complete all detections.

[0206] Step b specifically involves: To avoid the risk of pressure sensor reading deviations caused by gas flow, resulting in the gas chamber pressure falling below the alarm value, when determining the gas intake volume through pressure drop, the volume of the SF6 gas chamber to be tested can be calculated first, and then the safe gas intake volume can be determined accordingly; specifically:

[0207] First, calculate the gas density of the SF6 chamber at the initial moment. Connect the SF6 gas chamber to be tested to the detection device via an external gas port, open the first solenoid valve, and record the initial pressure value of the SF6 gas chamber to be tested using a pressure sensor. The temperature sensor records the initial temperature value of the SF6 gas chamber under test. Calculate the initial density value at this time. for:

[0208] Formula 1;

[0209]

[0210]

[0211]

[0212] in, The initial pressure value of the SF6 gas chamber to be tested; The initial temperature value of the SF6 gas chamber to be tested; It is the gas constant; These are the parameters corresponding to the gravitational effect; The parameter corresponding to molecular volume / repulsion force;

[0213] Since the content of decomposition products is very low, the calculated gas density can be considered to be equal to that of SF6, and the same applies below.

[0214] Secondly, the density of SF6 gas after a portion of the SF6 gas flows from the SF6 chamber to the second piston chamber and passes through the flow meter is calculated. and the density of SF6 gas in the SF6 chamber to be tested ;

[0215] Then open the second solenoid valve to allow the mixture of SF6 gas and SF6 decomposition products in the SF6 gas chamber to enter the second piston chamber. The first flow meter records the volume of gas flowing from the SF6 gas chamber to the second piston chamber 9-2 per unit time. When the pressure in the test chamber drops to a predetermined threshold (which is much smaller than the alarm pressure drop value), the elapsed time is recorded. Then, the second solenoid valve is closed, and the gas density flowing through the first flow meter is calculated. :

[0216] Formula 2;

[0217]

[0218]

[0219]

[0220] in, The pressure value under operating conditions when the flow rate is recorded by the flow meter. ; The operating temperature value at which the flow rate is recorded by the flow meter. ; It is the gas constant; These are parameters related to gravitational effects; A parameter related to molecular volume / repulsion.

[0221] When the flow meter records the flow rate as the volume of water flowing through the system at 0℃ and 0.1 MPa, then ;

[0222] The pressure value of the SF6 gas chamber under test is recorded by pressure sensor (4-1). Temperature sensor (4-2) records the temperature value of the SF6 gas chamber to be tested. Then close solenoid valve 2-1 and calculate the density value at this time. for:

[0223] Formula 3;

[0224]

[0225]

[0226]

[0227] in, The pressure value of the SF6 gas chamber to be measured after a portion of the gas enters the second piston chamber from the gas chamber to be measured.

[0228] The temperature of the SF6 gas chamber being measured is the value after a portion of the gas enters the second piston chamber from the gas chamber being measured.

[0229] It is the gas constant;

[0230] These are the parameters corresponding to the gravitational effect;

[0231] The parameter corresponding to molecular volume / repulsion force;

[0232] Based on the law of conservation of mass, we can conclude that:

[0233] Formula 4;

[0234] in, The initial density value of the SF6 gas chamber to be tested is obtained by formula 1;

[0235] The density of the gas flowing through the first flow meter is calculated using formula 2;

[0236] The gas density value of the SF6 gas chamber to be tested after part of the gas enters the second piston gas chamber from the gas chamber to be tested is calculated by formula 3.

[0237] To record the elapsed time after the pressure in the test chamber drops to a certain threshold (which is much smaller than the alarm pressure drop value);

[0238] The volume of gas flowing from the SF6 chamber under test into the second piston chamber per unit time, as recorded by the first flow meter;

[0239] The volume of the SF6 gas chamber to be measured is the result obtained through calculation, as shown in Formula 5;

[0240] Thus, the volume of the SF6 gas chamber to be measured can be obtained. for:

[0241] Formula 5.

[0242] Step c specifically involves: opening the first and second solenoid valves, based on the SF6 gas chamber volume obtained in step b. The volume of gas flowing in per unit time is recorded by the first flow meter. At this point, the sampling time for the second SF6 gas sample taken from the chamber to be tested is determined. The calculation method is as follows:

[0243] ① Record the initial pressure value of the SF6 gas chamber to be tested Temperature sensor 4-2 records the initial temperature value of the SF6 gas chamber under test. The initial density value of the SF6 gas chamber to be tested can then be calculated using Formula 1. ;

[0244] ② Calculate the pressure drop (The pressure drop must be less than the alarm pressure) the density value of the gas chamber to be measured. The temperature at this stage is the average of the two temperature measurements taken in step b. The calculation is as follows:

[0245] Formula 6;

[0246]

[0247]

[0248]

[0249] in, The pressure value of the SF6 gas chamber to be measured after a portion of the gas enters the second piston chamber from the gas chamber to be measured. This represents the maximum pressure drop during the second gas extraction. The initial temperature value of the SF6 gas chamber to be tested; The temperature of the SF6 gas chamber being measured is the value after a portion of the gas enters the second piston chamber from the gas chamber being measured. This is the average of two temperature measurements; It is the gas constant; These are the parameters corresponding to the gravitational effect; The parameter corresponds to the molecular volume / repulsion force.

[0250] ③ Calculate the gas intake :

[0251] Formula 7;

[0252] in, The initial density value of the SF6 gas chamber to be tested is obtained by formula 1; For the second gas extraction, pressure drop The density value of the gas chamber to be tested after the pressure drop is less than the alarm pressure is calculated by formula 6;

[0253] ④ Calculate the gas sampling time :

[0254] Formula 8;

[0255] in, The density of the gas flowing through the flow meter is calculated using formula 2; The gas intake is calculated using formula 7; The first flow meter records the volume of gas flowing from the SF6 chamber under test into the second piston chamber per unit time.

[0256] When the sampling time has elapsed Then close the first and second solenoid valves to complete the gas sampling.

[0257] Step d specifically involves the following: the sampled gas enters the second piston chamber and begins to liquefy.

[0258] If the SF6 gas chamber to be tested is a small chamber, the gas intake will be small. In this case, the piston moves via the motor and connecting rod, thereby reducing the volume of the second piston chamber and increasing the gas pressure in the second piston chamber. This improves the liquefaction degree of SF6 gas and increases the enrichment rate of SF6 gas decomposition products. The adjusted volume of the second piston chamber depends on the liquefaction degree of SF6 gas, and the specific method for determining it is as follows:

[0259] ① After a preset set time, open the second solenoid valve and record the gas pressure in the second piston chamber using a pressure sensor. The gas temperature in the second piston chamber is recorded by a temperature sensor. Calculated based on the SF6 liquefaction formula:

[0260] Formula 9;

[0261] in, Based on temperature The calculated pressure value of gaseous SF6 at the theoretical liquefaction state under gas-liquid equilibrium. After a predetermined period of time (which can be considered as the time when the liquefaction gas and liquid are in equilibrium) has started, the temperature sensor records the gas temperature in the second piston gas chamber.

[0262] like The gas pressure in the second piston chamber... The theoretically calculated pressure value of gaseous SF6 in liquefied state at gas-liquid equilibrium. If the values ​​are equal, it indicates that the initial liquefaction of the sample gas has been completed;

[0263] ② To calculate the volume of liquefied SF6 at this point, first calculate the density of the gaseous SF6 at this point. for:

[0264] Formula 10

[0265]

[0266]

[0267]

[0268] in, When the liquefied gas is in equilibrium, the pressure sensor records the gas pressure in the second piston gas chamber; The temperature of the gas in the second piston chamber is recorded by the temperature sensor after a predetermined period of time (which can be considered as the time when the liquefaction gas and liquid are in equilibrium).

[0269] It is the gas constant; These are parameters related to gravitational effects; These are parameters related to molecular volume / repulsion.

[0270] Given that when the piston is in the initial position, the volume of the second piston chamber is... At this point, when the liquefied gas and liquid are in equilibrium, the volume of gaseous SF6 gas is... have:

[0271] Formula 11;

[0272] in, The density of SF6 liquid is given. Since the liquid density changes very little with temperature, it is assumed that... It is a constant value; The density value of gaseous SF6 gas at liquefied gas-liquid equilibrium; The length of the second piston chamber after subtracting the length of the piston from the total length of the second piston chamber; This represents the cross-sectional area of ​​the second piston chamber. The gas intake is calculated using formula 7;

[0273] Thus, the volume of liquefied SF6 can be calculated. for:

[0274] Formula 12;

[0275] in, The density of SF6 liquid is given. Since the liquid density changes very little with temperature, it is assumed that... It is a constant value; The density value of gaseous SF6 gas at liquefied gas-liquid equilibrium; The length of the second piston chamber after subtracting the length of the piston from the total length of the second piston chamber; This represents the cross-sectional area of ​​the second piston chamber. This represents the volume of gaseous SF6 gas at liquefied gas-liquid equilibrium. The gas intake is calculated using formula 7;

[0276] If the volume of liquefied SF6 at this time ,in To achieve the lowest liquefied SF6 volume, it is not necessary to turn on the motor; the volume of the second piston gas chamber 9-2 is changed by the connecting rod and piston.

[0277] If the volume of liquefied SF6 at this time Then the motor is turned on, and the volume of the second piston chamber is changed through the connecting rod and piston, thereby increasing the volume of liquefied SF6 to reach the minimum liquefied SF6 volume. The method for determining the piston movement distance is as follows:

[0278] Since the first weak cooling temperature control module 16-1 and the second weak cooling temperature control module 16-2 can achieve stable cooling, the temperature of the second piston gas chamber 9-2 will not change significantly and can be considered constant.

[0279] Based on Equation 9, when the temperature remains constant, the pressure of SF6 gas in equilibrium remains unchanged, and is still [value missing]. Therefore, the density value of SF6 gas in equilibrium remains unchanged. Therefore, the volume of SF6 gas for:

[0280] Formula 13;

[0281] in, The density of SF6 liquid is given. Since the liquid density changes very little with temperature, it is assumed that... It is a constant value; The density value of gaseous SF6 gas at liquefied gas-liquid equilibrium; The minimum liquefied SF6 liquid volume (set value); The gas intake is calculated using formula 7;

[0282] At this time, the volume of the second piston air chamber for:

[0283] Formula 14;

[0284] in, The minimum liquefied SF6 liquid volume (set value); The volume of gaseous SF6 gas after the second piston chamber volume is changed is calculated using formula 13.

[0285] To obtain the downward distance that the piston and connecting rod need to move. for:

[0286] Formula 15;

[0287] in, The length after subtracting the piston length from the total length of the second piston chamber; This represents the cross-sectional area of ​​the second piston chamber. The volume of the second piston chamber after the volume of the second piston chamber is changed by the piston;

[0288] Based on an infrared ranging transmitter and receiver, the downward distance of the connecting rod is recorded. When the downward distance is... The motor is controlled to stop moving the connecting rod and piston, completing the volume change of the second piston chamber; the mass of the liquid at this time is recorded. :

[0289] Formula 16;

[0290] in, The minimum liquefied SF6 liquid volume (set value); Before the piston changes the volume of the second piston chamber, the volume of SF6 liquid at the point of liquefied gas-liquid equilibrium is calculated using formula 12.

[0291] The density of SF6 liquid is given. Since the liquid density changes very little with temperature, it is assumed that... It is a constant value;

[0292] Record the mass of the gas at this time as :

[0293] Formula 17;

[0294] in, Before the piston changes the volume of the second piston chamber, the volume of gaseous SF6 gas at the liquefied gas-liquid equilibrium is calculated using formula 11. The volume of gaseous SF6 gas after the second piston chamber volume is changed is calculated using formula 13. This represents the density of gaseous SF6 gas at liquefied gas-liquid equilibrium.

[0295] Step e specifically involves: first, closing the second solenoid valve and allowing it to stand for a period of time to ensure that the gas-liquid mixture in the second piston gas chamber reaches equilibrium; then, opening the third solenoid valve; the cooling temperatures of the first forced cooling temperature control module 6-1 and the second forced cooling temperature control module 6-2 are lower than the cooling temperatures of the first weak cooling temperature control module 13-1 and the second weak cooling temperature control module 13-2, and the SF6 gas and its decomposition products in the second piston gas chamber enter the spectral detection chamber 7, where the volume of the gas flowing in per unit time is recorded by the second flow meter. After time Then, the third solenoid valve is closed, and the concentration of SF6 gas decomposition products flowing into the spectral detection chamber for the first time is detected by the spectral detection transmitter 5-1 and the spectral detection receiver 5-2. The mass of the gas entering the spectral detection chamber at this time for

[0296] Formula 18;

[0297] in, The second flow meter records the volume of gas flowing from the second piston gas chamber to the spectral detection chamber per unit time. The density of the gas flowing through the second flow meter is calculated by formula 2. Since the flow rate recorded by the flow meter is the volume of gas flowing through the flow at 0℃ and 0.1MPa, the density of the gas flowing through the second flow meter 3-2 can be considered to be equivalent to the density of the gas flowing through the first flow meter 3-1. The time it takes for the gas to flow from the second piston gas chamber to the spectral detection chamber;

[0298] Since the flow rate recorded by the flow meter is the volume of gas flowing under conditions of 0℃ and 0.1 MPa, the gas density here is consistent with the density in Formula 2. .

[0299] Based on the concentration of SF6 gas decomposition products The mass of SF6 gas decomposition products entering the spectral detection chamber from the second piston gas chamber was calculated. and SF6 gas mass :

[0300] Formula 19;

[0301] in, The concentration of SF6 gas decomposition products was detected by the spectrometer receiver during the first flow into the spectrometer detection chamber. The density of the gas flowing through the second flow meter is calculated by formula 2. Since the flow rate recorded by the flow meter is the volume of gas flowing through the flow meter at 0℃ and 0.1 MPa, the density of the gas flowing through flow meter 3-2 can be considered to be equal to the density of the gas flowing through flow meter 3-1.

[0302] The time it takes for the gas to flow from the second piston gas chamber to the spectral detection chamber; The mass of the gas entering the spectral detection chamber is calculated using Formula 18.

[0303] Step f specifically involves calculating the mass of SF6 gas decomposition products from the results of steps a through e. and SF6 gas mass The gas phase partial pressures of the SF6 gas decomposition products were calculated. Specifically:

[0304] Formula 20;

[0305] in, When the liquefied gas is in equilibrium, the pressure sensor records the gas pressure in the second piston gas chamber; The molar mass of SF6; The molar mass of the decomposition products of SF6 gas; The mass of the SF6 gas decomposition products is calculated using formula 19; The mass of SF6 gas is calculated using formula 19;

[0306] Since the amount of SF6 gas decomposition products is very small, the solubility of SF6 gas decomposition products in liquid SF6 is calculated based on the principles of chemical thermodynamics and the Beattie-Bridgman assay. Under equilibrium conditions, the fugacity of SF6 gas decomposition products in liquid SF6 is also calculated. Harmony and harmony They are equal, expressed by the formula:

[0307] Formula 21;

[0308] in, The fugacity of SF6 gas decomposition products in gaseous SF6; This represents the fugacity of SF6 gas decomposition products in liquid SF6.

[0309] The gas phase fugacity is expressed as:

[0310] Formula 22;

[0311] in, The mole fraction of SF6 gas decomposition products in gaseous SF6 is calculated using formula 23; The fugacity coefficient of the SF6 gas decomposition products in gaseous SF6 is calculated by formula 24; The partial pressure of the gas phase of the SF6 gas decomposition products is calculated using formula 20; where, The mole fraction of SF6 gas decomposition products in SF6 gas is calculated as follows:

[0312] Formula 23;

[0313] in, When the liquefied gas is in equilibrium, the pressure sensor records the gas pressure in the second piston gas chamber; The partial pressure of the gas phase of the SF6 gas decomposition products is calculated using formula 20;

[0314] The fugacity coefficient of the SF6 gas decomposition products in gaseous SF6 is calculated as follows:

[0315] Formula 24;

[0316] Where Z is the compressibility factor of the SF6 gas decomposition products; The volume of gaseous SF6 (the volume of gaseous SF6 gas when the liquefied gas-liquid equilibrium is taken into account in the calculation). (Calculated by formula 12) This refers to the amount of substance of the decomposition products of SF6 gas. Here, T is the gas constant; T is the temperature (the temperature at which the liquefied gas-liquid equilibrium is taken into account during the calculation). (i.e., the temperature in Formula 9).

[0317] Fugacity of SF6 gas decomposition products in liquid SF6 Represented as:

[0318] Formula 25;

[0319] in, This represents the mole fraction of SF6 gas decomposition products in liquid SF6. The fugacity coefficient of the SF6 gas decomposition products in liquid SF6 is calculated using formula 26. The partial pressure of the gas phase of the SF6 gas decomposition products is calculated using formula 20;

[0320] in, The fugacity coefficient of the decomposition products of SF6 gas in liquid SF6 is calculated as follows:

[0321] Formula 26;

[0322] Where Z is the compressibility factor of the SF6 gas decomposition products; The volume of liquid SF6 (the volume of liquid SF6 gas during the liquefied gas-liquid equilibrium calculation). (Calculated by formula 12) This refers to the amount of substance of the decomposition products of SF6 gas. It is the gas constant; Temperature (the temperature at which the liquefied gas-liquid equilibrium is input during calculation) (i.e., the temperature in Formula 9).

[0323] Calculate using formulas 21 to 26 :

[0324] Formula 27.

[0325] Step g specifically involves: deriving the theoretically calculated solubility of SF6 decomposition products in liquid SF6 from the calculation results of steps a-f. To further ensure the accuracy of the solubility, the experimentally obtained solubility of SF6 decomposition products in liquid SF6 is introduced for correction, thus establishing a more reasonable calculation model for the solubility of SF6 decomposition products in liquid SF6. The experiment involves liquefying SF6 gas mixed with a predetermined proportion of SF6 decomposition products, detecting the concentration of SF6 decomposition products in the upper gas layer, and then calculating the theoretically calculated solubility of SF6 decomposition products in liquid SF6 under the experimental conditions using the method described in step f. The volume of liquid SF6 Volume of gaseous SF6 partial pressure of the gas phase of SF6 decomposition products Total gas pressure Theoretical calculations of the solubility of SF6 decomposition products in liquid SF6 liquefaction temperature As input, that is: The solubility of SF6 decomposition products in liquid SF6 obtained from the experiment. As output quantity ; thereby constructing the global input matrix With output ;

[0326] The model is trained based on a residual neural network with physical constraints, and the calculations for each layer are as follows:

[0327] Layer 0, Input Layer: Formula 28;

[0328] First layer: Formula 29;

[0329] Second layer: Formula 30;

[0330] Third layer: Formula 31;

[0331] Fourth layer, output layer: Formula 32;

[0332] Finally, the predicted solubility of SF6 decomposition products in [the solution] was obtained. for: Formula 33;

[0333] in, , , , These are the weights for the first, second, third, and fourth layers, respectively. This means taking the absolute value of all weights in the fourth layer and assigning it back. middle; , , , These are the offsets for the first, second, third, and fourth layers, respectively. This is an activation function with the following rule: if the number in the parentheses is greater than or equal to 0, output it as is; if the number in the parentheses is less than 0, output 0, so that all data are in the non-negative value region. , , These are the outputs of the first, second, and third hidden layers, respectively. This represents the deviation between theoretically calculated values ​​and experimental values ​​based on model predictions.

[0334] Based on formula 33, the mass concentration of the decomposition products of liquid SF6 gas is calculated as follows: :

[0335] Formula 34;

[0336] in, The solubility of SF6 decomposition products in the solution was calculated using Equation 33. The molar mass of SF6; This represents the molar mass of the decomposition products of SF6 gas.

[0337] In step h, the mass concentration of the gaseous SF6 decomposition products actually detected in step e is: The mass concentration of the liquid-phase SF6 gas decomposition products was calculated through steps f and g. The concentration of SF6 gas decomposition products in the second piston chamber was calculated using formulas 16 and 17. for:

[0338] Formula 35;

[0339] in, The concentration of SF6 gas decomposition products was detected by the spectrometer receiver during the first flow into the spectrometer detection chamber. The mass concentration of the decomposition products of liquid SF6 gas is calculated using formula 34; The mass of liquid in the second piston gas chamber when the liquefied gas is in equilibrium is calculated using formula 16. The mass of gas in the second piston chamber at liquefied gas-liquid equilibrium is calculated using formula 17; the concentration of SF6 gas decomposition products in the second piston chamber 9-2 is... Similarly, the concentration of SF6 gas decomposition products in the SF6 gas chamber to be measured is combined with the density in Formula 1. And the volume of the SF6 gas chamber to be measured in Formula 5 The total mass of SF6 gas decomposition products in the SF6 gas chamber to be tested was obtained. for:

[0340] Formula 36;

[0341] in, To calculate the concentration of SF6 gas decomposition products in piston chamber 9-2 (i.e., to measure the concentration of SF6 gas decomposition products in the SF6 chamber), it is calculated using formula 35; The initial density value of the SF6 gas chamber to be tested is calculated using formula 3; The volume of the SF6 gas chamber to be measured is the result that needs to be calculated, obtained by formula 5.

[0342] Example:

[0343] This example proposes at the device level: a variable volume enrichment sampling device for SF6 gas decomposition products, comprising: a piston-type variable volume enrichment tank, an adjustment mechanism for driving the piston to move to change the tank's internal volume, a refrigeration unit for cooling and liquefying SF6, and a spectroscopic gas phase detector for detecting the concentration of decomposition products in the upper gas layer inside the tank.

[0344] The device also includes a control unit, which controls the adjustment mechanism based on the input volume information of the gas chamber to be sampled, so that the volume of the liquefied liquid SF6 is greater than a preset threshold. .

[0345] This example proposes a method for the spectral detection of SF6 decomposition product concentrations based on variable volumetric enrichment, comprising the following steps:

[0346] a. Based on the volume of the electrical gas chamber to be tested, adjust the volume of the variable volume enrichment tank and take gas samples;

[0347] b. Liquefy the sampled SF6 gas portion, ensuring the volume of liquid SF6 is greater than the set value. ;

[0348] c. Spectroscopic methods are used to detect and obtain the partial pressure or concentration of decomposition products in the upper gas layer after gas-liquid equilibrium;

[0349] d. Based on the partial pressure or concentration, calculate the theoretical solubility of the decomposition products in liquid SF6;

[0350] e. Input the theoretical solubility and related parameters into the pre-trained neural network correction model to obtain the corrected solubility prediction value;

[0351] f. Based on the corrected solubility prediction, and the volume and mass of SF6 in the gas and liquid phases, calculate the total concentration of decomposition products in the original SF6 gas.

[0352] This example presents the following regarding systems and models:

[0353] a. An intelligent analysis system for the concentration of SF6 decomposition products by spectroscopic method, characterized in that it includes a sampling device and a data processing unit; the data processing unit stores and runs the neural network correction model to perform the calculation steps described above at the method level.

[0354] b. A neural network model for correcting the calculation of solubility of decomposition products in SF6. The model is obtained by training with theoretical solubility calculation results, temperature, pressure, and types of decomposition products as input features and experimentally measured real solubility as the training target. It is used to correct the deviation of the output results of the gas-liquid equilibrium theoretical formula.

Claims

1. A method for spectroscopic detection of SF6 decomposition products, characterized in that: The method uses a piston-type variable volume structure to adaptively adjust the sampling amount of the SF6 gas chamber under test, and constructs a gas-liquid two-phase dissolution compensation and full concentration calculation model. First, it ensures that the liquefaction volume of SF6 is greater than a set threshold during the liquefaction and enrichment process of each sample, and calculates its theoretical solubility in the liquid phase by detecting the concentration of the upper gas phase by spectrum and combining partial pressure and fugacity. A solubility dynamic correction model is constructed using a neural network. Based on the dissolution behavior of decomposition products during liquefaction, theoretical predictions and actual corrections are performed to compensate for dissolution losses. Furthermore, by integrating the mass and solubility information of SF6 in the gas and liquid phases during the enrichment process, the total concentration of SF6 decomposition products in the test chamber can be detected.

2. A spectral detection system for SF6 decomposition products, employing the spectral detection method for SF6 decomposition products as described in claim 1, characterized in that: The variable volume structure includes a piston-type variable volume enrichment tank for connecting to the SF6 gas chamber to be tested. The piston-type variable volume enrichment tank achieves continuous adjustment of the sampling volume inside the tank through a piston structure, ensuring that the SF6 liquefaction volume is greater than a set threshold during each sampling and liquefaction process. In the piston running direction of the piston structure, a first piston air chamber (9-1) and a second piston air chamber (9-2) are respectively provided on both sides of the piston (10). An external gas port (1) is provided at the beginning of the sampling gas path connecting the second piston gas chamber to the SF6 gas chamber under test. The opening and closing of the sampling gas path is controlled by the first solenoid valve (2-1) and the second solenoid valve (2-2) at the sampling gas path. A pressure sensor (4-1) and a temperature sensor (4-2) are provided at the sampling gas path. A first flow meter (3-1) is also provided to measure the amount of gas flowing into the first piston gas chamber from the SF6 gas chamber under test. The second piston gas chamber is connected to the spectral detection chamber (7) via a cooled sample pipeline; A motor (11) is provided at the second piston chamber, which drives the piston to move vertically via a connecting rod (12); the sampling process changes the volume of the first piston chamber by the vertical movement of the piston, and the total length of the second piston chamber after deducting the length of the piston is... And the cross-sectional area is ; The connecting rod is located inside the first piston air chamber. An infrared ranging transmitter (8-1) is installed at the tail end of the connecting rod (12). An infrared ranging receiver (8-2) is located on the inner wall of the first piston air chamber in the direction of the infrared ranging transmitter's emission. The initial distance between the infrared ranging transmitter and the infrared ranging receiver is... The initial position is the position closest to the infrared ranging transmitter and the infrared ranging receiver; During the liquefaction process of spectral detection, the sampling gas in the second piston gas chamber is stably cooled during the sampling stage by the first weak cooling temperature control module (13-1) and the second weak cooling temperature control module (13-2) located at the second piston gas chamber. During the liquefaction process of spectral detection, the sampling gas in the spectral detection chamber is stably cooled during the detection stage by the first forced cooling temperature control module (6-1) and the second forced cooling temperature control module (6-2) located in the spectral detection chamber. A third solenoid valve (2-3) is installed at the cooling sample pipeline; The spectral detection chamber is connected to the cooling sample pipeline via a sample input pipeline; the main branch of the sample input pipeline is equipped with a third solenoid valve (2-3), and the sample input pipeline is equipped with a second flow meter (3-2).

3. The SF6 decomposition product spectral detection system according to claim 2, characterized in that: When the detection system performs the enrichment and sampling detection of SF6 gas decomposition products, the specific procedure varies depending on the size of the SF6 gas chamber to be tested. Includes the following steps, Step a, preliminary preparation, specifically: turn on the motor, and use the connecting rod to drive the piston back to the position where the infrared ranging transmitter and the infrared ranging receiver are closest to each other; Open the first solenoid valve, the second solenoid valve, and the third solenoid valve. Connect the vacuum pump through the external air port to evacuate the detection system to a vacuum state. Then close the first solenoid valve, the second solenoid valve, and the third solenoid valve to complete the preliminary preparation. Turn on the first and second weak cooling temperature control modules to stabilize the cooling temperature of the second piston gas chamber at or near -30℃; turn on the first and second forced cooling temperature control modules to stabilize the cooling temperature of the spectral detection chamber at or near -45℃. Step b: Obtain the volume of the SF6 gas chamber to be tested: Step c: Based on the volume of the SF6 gas chamber to be measured Determine the gas sampling time : Step d: Change the volume of the second piston gas chamber to increase the volume of liquefied SF6. , The minimum volume of SF6 to be liquefied; Step e: Detection of SF6 gas decomposition product concentration; Step f: Calculation of the concentration of decomposition products of liquefied liquid SF6 gas after cooling and liquefaction; Step g: Correction model for calculating the solubility of liquid SF6 decomposition products based on experimental data; Step h: Calculate the concentration of SF6 gas decomposition products in the SF6 gas chamber to be tested.

4. The SF6 decomposition product spectral detection system according to claim 3, characterized in that: Step b specifically involves: first calculating the volume of the SF6 gas chamber to be tested, and then determining the safe gas intake based on this volume; specifically: First, calculate the gas density of the SF6 chamber at the initial moment. Connect the SF6 gas chamber to be tested to the detection device via an external gas port, open the first solenoid valve, and record the initial pressure value of the SF6 gas chamber to be tested using a pressure sensor. The temperature sensor records the initial temperature value of the SF6 gas chamber under test. Calculate the initial density value at this time. for: Official 1; in, The initial pressure value of the SF6 gas chamber to be tested; The initial temperature value of the SF6 gas chamber to be tested; It is the gas constant; These are the parameters corresponding to the gravitational effect; The parameter corresponding to molecular volume / repulsion force; Secondly, the density of SF6 gas after a portion of the SF6 gas flows from the SF6 chamber to the second piston chamber and passes through the flow meter is calculated. and the density of SF6 gas in the SF6 chamber to be tested ; Then open the second solenoid valve to allow the mixture of SF6 gas and SF6 decomposition products in the SF6 gas chamber to enter the second piston chamber. The first flow meter records the volume of gas flowing from the SF6 gas chamber to the second piston chamber 9-2 per unit time. Once the pressure in the test chamber drops to a predetermined threshold, the elapsed time is recorded. Then, the second solenoid valve is closed, and the gas density flowing through the first flow meter is calculated. : Official 2; in, The operating pressure value when the flow rate is recorded by the flow meter; The operating temperature value when the flow rate is recorded by the flow meter; It is the gas constant; These are parameters related to gravitational effects; A parameter related to molecular volume / repulsion. The pressure value of the SF6 gas chamber under test is recorded by pressure sensor (4-1). Temperature sensor (4-2) records the temperature value of the SF6 gas chamber to be tested. Then close the first solenoid valve and calculate the density value at this time. for: Official 3; in, The pressure value of the SF6 gas chamber to be measured after a portion of the gas enters the second piston chamber from the gas chamber to be measured. The temperature of the SF6 gas chamber being measured is the value after a portion of the gas enters the second piston chamber from the gas chamber being measured. It is the gas constant; These are the parameters corresponding to the gravitational effect; The parameter corresponding to molecular volume / repulsion force; Based on the law of conservation of mass, we can conclude that: Official 4; in, The initial density value of the SF6 gas chamber to be tested is obtained by formula 1; The density of the gas flowing through the first flow meter is calculated using formula 2; The gas density value of the SF6 gas chamber to be tested after part of the gas enters the second piston gas chamber from the gas chamber to be tested is calculated by formula 3. To record the elapsed time after the pressure in the test chamber drops to a certain threshold; The volume of gas flowing from the SF6 chamber under test into the second piston chamber per unit time, as recorded by the first flow meter; The volume of the SF6 gas chamber to be measured is the result obtained through calculation, as shown in Formula 5; Thus, the volume of the SF6 gas chamber to be measured can be obtained. for: Official 5.

5. The SF6 decomposition product spectral detection system according to claim 4, characterized in that: Step c specifically involves: opening the first and second solenoid valves, based on the SF6 gas chamber volume obtained in step b. The volume of gas flowing in per unit time is recorded by the first flow meter. At this point, the sampling time for the second SF6 gas sample taken from the chamber to be tested is determined. The calculation method is as follows: ① Record the initial pressure value of the SF6 gas chamber to be tested Temperature sensor (4-2) records the initial temperature value of the SF6 gas chamber under test. The initial density value of the SF6 gas chamber to be tested can then be calculated using Formula 1. ; ② Calculate the pressure drop The density value of the gas chamber to be tested afterward The pressure drop is less than the alarm pressure. The temperature at this stage is the average of the two temperature measurements taken in step b. The calculation is as follows: Official 6; in, The pressure value of the SF6 gas chamber to be measured after a portion of the gas enters the second piston chamber from the gas chamber to be measured. This represents the maximum pressure drop during the second gas extraction. The initial temperature value of the SF6 gas chamber to be tested; The temperature of the SF6 gas chamber being measured is the value after a portion of the gas enters the second piston chamber from the gas chamber being measured. This is the average of two temperature measurements; It is the gas constant; These are the parameters corresponding to the gravitational effect; The parameter corresponds to the molecular volume / repulsion force. ③ Calculate the gas intake : Official 7; in, The initial density value of the SF6 gas chamber to be tested is obtained by formula 1; For the second gas extraction, pressure drop The density value of the gas chamber to be tested is then calculated using formula 6. ④ Calculate the gas sampling time : Official 8; in, The density of the gas flowing through the flow meter is calculated using formula 2; The gas intake is calculated using formula 7; The first flow meter records the volume of gas flowing from the SF6 chamber under test into the second piston chamber per unit time. When the sampling time has elapsed Then close the first and second solenoid valves to complete the gas sampling.

6. The SF6 decomposition product spectral detection system according to claim 5, characterized in that: Step d specifically involves the following: the sampled gas enters the second piston chamber and begins to liquefy. If the SF6 gas chamber to be tested is a small chamber, the gas intake will be small. In this case, the piston moves via the motor and connecting rod, thereby reducing the volume of the second piston chamber and increasing the gas pressure in the second piston chamber. This improves the liquefaction degree of SF6 gas and increases the enrichment rate of SF6 gas decomposition products. The adjusted volume of the second piston chamber depends on the liquefaction degree of SF6 gas, and the specific method for determining it is as follows: ① After a preset set time, open the second solenoid valve and record the gas pressure in the second piston chamber using a pressure sensor. The gas temperature in the second piston chamber is recorded by a temperature sensor. Calculated based on the SF6 liquefaction formula: Official 9; in, Based on temperature The calculated pressure value of gaseous SF6 at the theoretical liquefaction state under gas-liquid equilibrium. After a predetermined period of time has elapsed since liquefaction began, the temperature sensor records the gas temperature in the second piston chamber. like The gas pressure in the second piston chamber... The theoretically calculated pressure value of gaseous SF6 in liquefied state at gas-liquid equilibrium. If the values ​​are equal, it indicates that the initial liquefaction of the sample gas has been completed; ② To calculate the volume of liquefied SF6 at this point, first calculate the density of the gaseous SF6 at this point. for: Official 10 in, When the liquefied gas is in equilibrium, the pressure sensor records the gas pressure in the second piston gas chamber; The temperature sensor records the gas temperature in the second piston chamber after a predetermined period of time following the start of liquefaction and settling. It is the gas constant; These are parameters related to gravitational effects; These are parameters related to molecular volume / repulsion. Given that when the piston is in the initial position, the volume of the second piston chamber is... At this point, when the liquefied gas and liquid are in equilibrium, the volume of gaseous SF6 gas is... have: Official 11; in, The density of SF6 liquid; The density value of gaseous SF6 gas at liquefied gas-liquid equilibrium; The length of the second piston chamber after subtracting the length of the piston from the total length of the second piston chamber; This represents the cross-sectional area of ​​the second piston chamber. The gas intake is calculated using formula 7; Thus, the volume of liquefied SF6 can be calculated. for: Official 12; in, The density of SF6 liquid; The density value of gaseous SF6 gas at liquefied gas-liquid equilibrium; The length of the second piston chamber after subtracting the length of the piston from the total length of the second piston chamber; This represents the cross-sectional area of ​​the second piston chamber. This represents the volume of gaseous SF6 gas at liquefied gas-liquid equilibrium. The gas intake is calculated using formula 7; If the volume of liquefied SF6 at this time ,in To achieve the lowest liquefied SF6 volume, it is not necessary to turn on the motor; the volume of the second piston gas chamber 9-2 is changed by the connecting rod and piston. If the volume of liquefied SF6 at this time Then the motor is turned on, and the volume of the second piston chamber is changed through the connecting rod and piston, thereby increasing the volume of liquefied SF6 to reach the minimum liquefied SF6 volume. The method for determining the piston movement distance is as follows: Since the first weak cooling temperature control module 16-1 and the second weak cooling temperature control module 16-2 can achieve stable cooling, the temperature of the second piston gas chamber 9-2 will not change significantly and can be considered constant. Based on Equation 9, when the temperature remains constant, the pressure of SF6 gas in equilibrium remains unchanged, and is still [value missing]. Therefore, the density value of SF6 gas in equilibrium remains unchanged. Therefore, the volume of SF6 gas for: Official 13; in, The density of SF6 liquid is given. Since the liquid density changes very little with temperature, it is assumed that... It is a constant value; The density value of gaseous SF6 gas at liquefied gas-liquid equilibrium; The minimum liquefied SF6 liquid volume (set value); The gas intake is calculated using formula 7; At this time, the volume of the second piston air chamber for: Formula 14; in, The minimum volume of liquefied SF6 liquid; The volume of gaseous SF6 gas after the second piston chamber volume is changed is calculated using formula 13. To obtain the downward distance that the piston and connecting rod need to move. for: Official 15; in, The length after subtracting the piston length from the total length of the second piston chamber; This represents the cross-sectional area of ​​the second piston chamber. The volume of the second piston chamber after the volume of the second piston chamber is changed by the piston; Based on an infrared ranging transmitter and receiver, the downward distance of the connecting rod is recorded. When the downward distance is... The motor is controlled to stop moving the connecting rod and piston, completing the volume change of the second piston chamber; the mass of the liquid at this time is recorded. : Official 16; in, The minimum volume of liquefied SF6 liquid; Before the piston changes the volume of the second piston chamber, the volume of SF6 liquid at the point of liquefied gas-liquid equilibrium is calculated using formula 12. The density of SF6 liquid is given. Since the liquid density changes very little with temperature, it is assumed that... It is a constant value; Record the mass of the gas at this time as : Official 17; in, Before the piston changes the volume of the second piston chamber, the volume of gaseous SF6 gas at the liquefied gas-liquid equilibrium is calculated using formula 11. The volume of gaseous SF6 gas after the second piston chamber volume is changed is calculated using formula 13. This represents the density of gaseous SF6 gas at liquefied gas-liquid equilibrium.

7. The SF6 decomposition product spectral detection system according to claim 6, characterized in that: Step e is as follows: First, close the second solenoid valve and let it stand for a period of time to ensure that the gas-liquid mixture in the second piston gas chamber reaches a state of equilibrium; then open the third solenoid valve; the cooling temperature of the first forced cooling temperature control module (6-1) and the second forced cooling temperature control module (6-2) is lower than the cooling temperature of the first weak cooling temperature control module (13-1) and the second weak cooling temperature control module (13-2), and the SF6 gas and its decomposition products in the second piston gas chamber enter the spectral detection chamber (7), and the volume of the gas flowing in per unit time is recorded by the second flow meter. After time Then, the third solenoid valve is closed, and the concentration of SF6 gas decomposition products flowing into the spectral detection chamber for the first time is detected by the spectral detection transmitter (5-1) and the spectral detection receiver (5-2). The mass of the gas entering the spectral detection chamber at this time for Official 18; in, The second flow meter records the volume of gas flowing from the second piston gas chamber to the spectral detection chamber per unit time. The density of the gas flowing through the second flow meter is calculated using formula 2; The time it takes for the gas to flow from the second piston gas chamber to the spectral detection chamber; Based on the concentration of SF6 gas decomposition products The mass of SF6 gas decomposition products entering the spectral detection chamber from the second piston gas chamber was calculated. and SF6 gas mass : Official 19; in, The concentration of SF6 gas decomposition products was detected by the spectrometer receiver during the first flow into the spectrometer detection chamber. The density of the gas flowing through the second flow meter is calculated using formula 2; The time it takes for the gas to flow from the second piston gas chamber to the spectral detection chamber; The mass of the gas entering the spectral detection chamber is calculated using Formula 18.

8. The SF6 decomposition product spectral detection system according to claim 7, characterized in that: Step f specifically involves calculating the mass of SF6 gas decomposition products from the results of steps a through e. and SF6 gas mass The gas phase partial pressures of the SF6 gas decomposition products were calculated. Specifically: Official 20; in, When the liquefied gas is in equilibrium, the pressure sensor records the gas pressure in the second piston gas chamber; The molar mass of SF6; The molar mass of the decomposition products of SF6 gas; The mass of the SF6 gas decomposition products is calculated using formula 19; The mass of SF6 gas is calculated using formula 19; Based on the principles of chemical thermodynamics and the Beattie-Bridgman calculation, the solubility of SF6 gas decomposition products in liquid SF6 was calculated. Under equilibrium conditions, the fugacity of SF6 gas decomposition products in liquid SF6 was also determined. Harmony and harmony They are equal, expressed by the formula: Official 21; in, The fugacity of SF6 gas decomposition products in gaseous SF6; This represents the fugacity of SF6 gas decomposition products in liquid SF6. The gas phase fugacity is expressed as: Official 22; in, The mole fraction of SF6 gas decomposition products in gaseous SF6 is calculated using formula 23; The fugacity coefficient of the SF6 gas decomposition products in gaseous SF6 is calculated by formula 24; The partial pressure of the gas phase of the SF6 gas decomposition products is calculated using formula 20; where, The mole fraction of SF6 gas decomposition products in SF6 gas is calculated as follows: Official 23; in, When the liquefied gas is in equilibrium, the pressure sensor records the gas pressure in the second piston gas chamber; The partial pressure of the gas phase of the SF6 gas decomposition products is calculated using formula 20; The fugacity coefficient of the decomposition products of SF6 in gaseous SF6 is calculated as follows: Formula 24; Where Z is the compressibility factor of the SF6 gas decomposition products; Given the volume of liquid SF6, calculate the volume of liquid SF6 gas when liquefied gas-liquid equilibrium is reached. It is calculated using formula 12; This refers to the amount of substance of the decomposition products of SF6 gas. It is the gas constant; For temperature, calculate the temperature at which the liquefied gas-liquid equilibrium is reached. That is, the temperature in Formula 9; Fugacity of SF6 gas decomposition products in liquid SF6 Represented as: Official 25; in, This represents the mole fraction of SF6 gas decomposition products in liquid SF6. The fugacity coefficient of the SF6 gas decomposition products in liquid SF6 is calculated using formula 26. The partial pressure of the gas phase of the SF6 gas decomposition products is calculated using formula 20; in, The fugacity coefficient of the decomposition products of SF6 gas in liquid SF6 is calculated as follows: Official 26; Where Z is the compressibility factor of the SF6 gas decomposition products; This represents the volume of liquid SF6. This refers to the amount of substance of the decomposition products of SF6 gas. It is the gas constant; For temperature; Calculate using formulas 21 to 26 : Official 27.

9. The SF6 decomposition product spectral detection system according to claim 8, characterized in that: Step g specifically involves: deriving the theoretically calculated solubility of SF6 decomposition products in liquid SF6 from the calculation results of steps a-f; then correcting this by incorporating the experimentally obtained solubility of SF6 decomposition products in liquid SF6 to establish a calculation model for the solubility of SF6 decomposition products in liquid SF6. The experiment involves liquefying SF6 gas mixed with a predetermined proportion of SF6 decomposition products, detecting the concentration of SF6 decomposition products in the upper gas layer, and then calculating the theoretically calculated solubility of SF6 decomposition products in liquid SF6 under these experimental conditions. The volume of liquid SF6 Volume of gaseous SF6 partial pressure of the gas phase of SF6 decomposition products Total gas pressure Theoretical calculations of the solubility of SF6 decomposition products in liquid SF6 liquefaction temperature As input, that is: The solubility of SF6 decomposition products in liquid SF6 obtained from the experiment. As output quantity ; thereby constructing the global input matrix With output ; The model is trained based on a residual neural network with physical constraints, and the calculations for each layer are as follows: Layer 0, Input Layer: Formula 28; First layer: Formula 29; Second layer: Formula 30; Third layer: Formula 31; Fourth layer, output layer: Formula 32; Finally, the predicted solubility of SF6 decomposition products in [the solution] was obtained. for: Formula 33; in, , , , These are the weights for the first, second, third, and fourth layers, respectively. This means taking the absolute value of all weights in the fourth layer and assigning it back. middle; , , , These are the offsets for the first, second, third, and fourth layers, respectively. This is an activation function with the following rule: if the number in the parentheses is greater than or equal to 0, output it as is; if the number in the parentheses is less than 0, output 0, so that all data are in the non-negative value region. , , These are the outputs of the first, second, and third hidden layers, respectively. This represents the deviation between theoretically calculated values ​​and experimental values ​​based on model predictions. Based on formula 33, the mass concentration of the decomposition products of liquid SF6 gas is calculated as follows: : Official 34; in, The solubility of SF6 decomposition products in the solution was calculated using Equation 33. The molar mass of SF6; This represents the molar mass of the decomposition products of SF6 gas.

10. The SF6 decomposition product spectral detection system according to claim 9, characterized in that: In step h, the mass concentration of the gaseous SF6 decomposition products actually detected in step e is: The mass concentration of the liquid-phase SF6 gas decomposition products was calculated through steps f and g. The concentration of SF6 gas decomposition products in the second piston chamber was calculated using formulas 16 and 17. for: Official 35; in, The concentration of SF6 gas decomposition products was detected by the spectrometer receiver during the first flow into the spectrometer detection chamber. The mass concentration of the decomposition products of liquid SF6 gas is calculated using formula 34; The mass of liquid in the second piston gas chamber when the liquefied gas is in equilibrium is calculated using formula 16. The mass of gas in the second piston chamber at liquefied gas-liquid equilibrium is calculated using formula 17; the concentration of SF6 gas decomposition products in the second piston chamber 9-2 is... Similarly, the concentration of SF6 gas decomposition products in the SF6 gas chamber to be measured is combined with the density in Formula 1. And the volume of the SF6 gas chamber to be measured in Formula 5 The total mass of SF6 gas decomposition products in the SF6 gas chamber to be tested was obtained. for: Official 36; in, The concentration of SF6 gas decomposition products in piston chamber 9-2 is calculated using formula 35. The initial density value of the SF6 gas chamber to be tested is calculated using formula 3; The volume of the SF6 gas chamber to be measured is the result that needs to be calculated, obtained by formula 5.

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