Calibration method of sulfur hexafluoride gas recovery equipment

Abstract

The invention relates to a calibration method of sulfur hexafluoride gas recovery equipment. The method comprises the following steps: collecting a detected sample gas, and collecting quantitative sample gas from a collection port of a carbon steel storage tank of recovery equipment into a first container of a detection device; the concentration of the sample gas is detected, the concentration of sulfur hexafluoride gas, the concentration of oxygen and the concentration of water vapor in the sample gas in the first container are detected through a sulfur hexafluoride gas sensor, an oxygen sensor and a humidity sensor which are communicated with the first container, and the sulfur hexafluoride gas sensor works according to the thermal conductivity principle; and calibrating the concentration of the sulfur hexafluoride gas, and compensating a measured value through a compensation formula. Adverse effects of oxygen, nitrogen and moisture are corrected through a compensation algorithm, so that the concentration detection precision of the sulfur hexafluoride gas during calibration is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of calibration methods of sulfur hexafluoride gas recovery equipment. BACKGROUND

[0002] Sulfur hexafluoride gas recovery equipment is used to recover the sulfur hexafluoride gas in circuit breaker arc chamber, its working principle is mainly based on refrigeration liquefaction method and multistage purification technology, through compression, cooling, separation etc. Step realizes the efficient recovery, purification and storage of SF6 gas, it mainly includes the processing module of compression, refrigeration, purification, vacuum etc. Subsystem and the storage subsystem mainly composed of carbon steel storage tank.Recovery equipment needs to be calibrated regularly to ensure recovery efficiency, recovery quality and safety etc. Among them, in order to ensure its safety and reusability, the gas concentration of sulfur hexafluoride in the carbon steel storage tank of recovery equipment needs to be detected, on the one hand, to determine whether it leaks, on the other hand, to detect its stability, to ensure that its concentration is stable at a certain value, after its concentration is stable, it can only meet the conditions of recharging to circuit breaker arc chamber by reaching the set purity after purification, the present application generally detects its concentration by using sulfur hexafluoride gas sensor based on thermal conductivity principle. However, due to insufficient sealing of equipment, impurities introduced during production or filling, water released by internal materials of equipment, etc., an uncertain amount of oxygen, nitrogen and moisture will be introduced, which will affect the detection accuracy of sulfur hexafluoride gas sensor based on thermal conductivity principle, so that the calibration accuracy cannot be guaranteed. SUMMARY

[0003] The purpose of the present application is to provide a kind of calibration methods of sulfur hexafluoride gas recovery equipment, the adverse effects of oxygen, nitrogen and moisture are corrected by compensation algorithm, so as to improve the concentration detection accuracy of sulfur hexafluoride gas during calibration.

[0004] The technical scheme of the present application is as follows: a kind of calibration methods of sulfur hexafluoride gas recovery equipment, comprising the following steps: S10, collecting the sample gas to be measured, collecting a certain amount of sample gas from the sampling port of the carbon steel storage tank of the recovery equipment into the first container of the detection device; S20, detecting the concentration of sample gas, respectively through sulfur hexafluoride gas sensor, oxygen sensor and humidity sensor communicated with the first container, detecting the concentration of sulfur hexafluoride gas, oxygen and water vapor in the sample gas in the first container, wherein the sulfur hexafluoride gas sensor works based on thermal conductivity principle; S30, calibrating the concentration of sulfur hexafluoride gas, compensating the measured value by the following compensation formula:

[0005] Wherein, represents the real SF6 concentration after compensation the uncompensated reading of the sulfur hexafluoride gas sensor the actual oxygen concentration measured by the oxygen sensor the reference oxygen concentration set at the calibration of the oxygen sensor the actual water vapor concentration measured by the humidity sensor the reference humidity concentration set at the calibration of the humidity sensor the oxygen compensation factor, the humidity compensation factor.

[0006] Further, Determined by the following method: Keeping the concentrations of sulfur hexafluoride gas and humidity constant, a fixed amount of oxygen is added to the first container from the oxygen tank connected to the first container, and the following formula is used to calculate :

[0007] wherein, represents the change in the uncompensated reading of the sulfur hexafluoride gas sensor before and after the addition of a fixed amount of oxygen; represents the change in the actual oxygen concentration measured by the oxygen sensor before and after the addition of a fixed amount of oxygen.

[0008] Further, Determined by the following method: Keeping the concentrations of sulfur hexafluoride gas and oxygen constant, a fixed amount of water vapor is added to the first container from the water vapor tank connected to the first container, and the following formula is used to calculate :

[0009] wherein, represents the change in the uncompensated reading of the sulfur hexafluoride gas sensor before and after the addition of a fixed amount of water vapor; represents the change in the actual water vapor concentration measured by the humidity sensor before and after the addition of a fixed amount of water vapor.

[0010] The beneficial effects of the present application are as follows: when the calibration method of the sulfur hexafluoride gas recovery equipment of the present application is used to calibrate the recovery equipment, it can cope with the interference of air leakage into the equipment, release of moisture from the material, etc. By compensating and correcting the water vapor and oxygen therein, the sulfur hexafluoride gas concentration of the measured gas recovered by the recovery equipment can be detected with high precision and close to the true concentration. Since nitrogen is the main background gas that does not change significantly, and its concentration change is reflected by the change of other components, because the introduction of nitrogen is mainly air, and the concentration of nitrogen in air is basically fixed (78.1%), and its concentration ratio with oxygen is also fixed. The formula indirectly corrects the change of the proportion of nitrogen thermal conductivity caused by the interference of oxygen and humidity on the measured value, thereby realizing the approximate solution of the true sulfur hexafluoride concentration. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 Principle diagram of the calibration system used by the calibration method of the sulfur hexafluoride gas recovery equipment of the present application; In the figure: 1 - circuit breaker arc chamber, 2 - sulfur hexafluoride gas recovery equipment, 21 - processing module, 22 - carbon steel storage tank, 221 - sampling port, 3 - detection device, 31 - first container, 32 - sulfur hexafluoride gas sensor, 33 - oxygen sensor, 34 - humidity sensor, 35 - oxygen storage tank, 36 - water vapor storage tank, 37 - flow control valve, 38 - waste gas collection tank. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical scheme and advantages of the present application clearer and more understandable, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application, that is, the described examples are only a part of the examples of the present application, but not all the examples. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0013] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0014] It is to be understood that the terms "first" and "second" and similar such relational terms are used solely to distinguish one entity or action from another without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by an occurrence of "comprising" does not exclude the existence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0015] The features and benefits of the present application will be further described with reference to the following examples.

[0016] One embodiment of the calibration method of the SF6 gas recovery equipment of the present application: the schematic diagram is shown in Figure 1 First, the sample gas to be measured is collected, and a certain amount of sample gas is collected from the carbon steel storage tank of the recovery equipment to the first container of the detection device through the collection port of the carbon steel storage tank; Then, the sample gas concentration is detected, and the SF6 gas, oxygen, and water vapor concentrations in the sample gas in the first container are detected through the SF6 gas sensor 32, oxygen sensor 33, and humidity sensor 34 connected with the first container 31, respectively, wherein the SF6 gas sensor works by using the thermal conductivity principle; Subsequently, the SF6 gas concentration is calibrated, and the measured value is compensated by the following compensation formula:

[0017] Wherein, represents the real SF6 concentration after compensation, i.e. the final value after compensation represents the reading of the SF6 gas sensor without compensation represents the actual oxygen concentration measured by the oxygen sensor represents the reference oxygen concentration set when the oxygen sensor is calibrated, which is usually 20.9% in air represents the actual water vapor concentration measured by the humidity sensor represents the reference humidity concentration set when the humidity sensor is calibrated, which is usually 0 or a certain fixed low value represents the oxygen compensation coefficient, represents the humidity compensation coefficient.

[0018] And .

[0019] Wherein, The following method is used to determine: Keeping the sulfur hexafluoride gas and humidity concentrations constant, a fixed amount of oxygen is added to the first container 31 through the oxygen storage tank 35 connected to the first container 31, calculated according to the following formula. :

[0020] in, This represents the change in the uncompensated reading of the sulfur hexafluoride gas sensor before and after the addition of a fixed amount of oxygen; This represents the change in oxygen concentration actually measured by the oxygen sensor before and after the addition of a fixed amount of oxygen. The formula means that for every 1% vol change in oxygen concentration, the SF6 measurement will have an error by a certain percentage.

[0021] The following method is used to determine: Keeping the concentrations of sulfur hexafluoride gas and oxygen constant, a fixed amount of water vapor is added to the first container 31 through a water vapor storage tank 36 connected to the first container 31, calculated according to the following formula. :

[0022] in, This represents the change in the uncompensated reading of the sulfur hexafluoride gas sensor before and after the addition of a fixed amount of water vapor; This represents the change in water vapor concentration actually measured by the humidity sensor before and after the addition of a fixed amount of water vapor. The formula means how much error will occur in the SF6 measurement value for every 1% vol (or ppmv, etc.) change in water vapor concentration.

[0023] The compensation coefficients F are not constant; they may vary with the SF6 concentration itself, temperature, and pressure. In these complex scenarios, the linear formula above may not be applicable, and compensation is often implemented in a microprocessor using a lookup table or piecewise linear fitting.

[0024] Regarding why the nitrogen concentration term is not shown in the above formula: This is because the compensation formula is based on an implicit assumption: nitrogen (N2) is the main, but not significantly changing, background gas, and its concentration changes are reflected through changes in other components (SF6, O2, H2O).

[0025] In most practical applications, this assumption holds true, for the following reasons:

[0026] 1. Assumptions regarding the background gas: In many thermal conductivity SF6 concentration detection applications (especially in fields such as power equipment monitoring), the background gas for SF6 is usually considered to be air.

[0027] The main components of air are nitrogen (about 78.1%), oxygen (about 20.9%), and small amounts of other gases.

[0028] The sensor is calibrated at the factory or during field calibration using a known background gas (such as standard dry air) as a reference. In this reference background gas, the ratio of N2 to O2 is fixed.

[0029] Relationship of the four main gas components: Assume the gas mixture consists of four main gases: SF6, O2, H2O, and N2.

[0030] Since the sum of the concentrations of all gases is 100% (or 1), then the actual concentration of nitrogen is... It can be represented as:

[0031] The focus of the compensation mechanism: SF6 is the target measurement object.

[0032] O2 and H2O are interfering substances with significantly different thermal conductivity from the background gas and large concentration fluctuations.

[0033] when or or When changes occur, An equal amount of negative change will also occur (to maintain the total volume at 100%).

[0034] Since the thermal conductivity of N2 is relatively close to that of the reference thermal conductivity in air (a mixture of N2 and O2), its variation typically has a smaller impact on thermal conductivity than the independent variations of SF6, O2, and H2O. Therefore, compensation formulas usually focus only on SF6, O2, and H2O, which have the strongest and most volatile thermal conductivity disturbances.

[0035] In short, the formula indirectly corrects the change in the proportion of nitrogen thermal conductivity caused by the interference of oxygen and humidity on the measured value, thus achieving an approximate solution for the true SF6 concentration. Only when the background gas assumption (i.e., mainly N2) does not hold (e.g., in SF6 / He or SF6 / Ar mixtures) is it necessary to explicitly introduce a compensation term for nitrogen (or helium, xenon, etc.).

[0036] When calibrating the sulfur hexafluoride gas recovery equipment using the calibration method of this application, interferences such as air leakage and moisture release from materials can be addressed. By compensating for water vapor and oxygen, the concentration of sulfur hexafluoride gas recovered by the equipment can be detected with a high-precision standard that is closer to the true concentration. Since nitrogen is the main background gas that does not change significantly, and its concentration change is reflected by the changes in other components, because the introduction of nitrogen is mainly from air, and the concentration of nitrogen in air is basically fixed (78.1%), and its concentration ratio with oxygen is also fixed, the formula indirectly corrects the change in the proportion of nitrogen thermal conductivity caused by the interference of oxygen and humidity on the measurement value, thereby achieving an approximate solution for the true sulfur hexafluoride concentration.

[0037] It should be noted that the oxygen sensor and humidity sensor in this embodiment are high-precision sensors.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A calibration method of a sulfur hexafluoride gas recovery device, comprising the following steps: S10, collecting a sample gas to be measured, collecting a quantitative sample gas from a carbon steel storage tank of the recovery device to a first container of a detection device through a sampling port of the carbon steel storage tank; S20, detecting a sample gas concentration, detecting sulfur hexafluoride gas, oxygen and water vapor concentrations of the sample gas in the first container through a sulfur hexafluoride gas sensor, an oxygen sensor and a humidity sensor in communication with the first container respectively, wherein the sulfur hexafluoride gas sensor works by using a thermal conductivity principle; S30, calibrating a sulfur hexafluoride gas concentration, compensating a measured value by using the following compensation formula: ； wherein, represents the true SF6 concentration after compensation represents the uncompensated reading of the SF6 gas sensor represents the actual measured oxygen concentration of the oxygen sensor represents the reference oxygen concentration set at calibration of the oxygen sensor represents the actual measured water vapor concentration of the humidity sensor represents the reference humidity concentration set at calibration of the humidity sensor represents the oxygen compensation factor, represents the humidity compensation factor.

2. The calibration method of a sulfur hexafluoride gas recovery plant according to claim 1, characterized in that, Determined using the following method: The concentration of sulfur hexafluoride gas and humidity is kept constant, and a certain amount of oxygen is added to the first container through an oxygen tank connected to the first container, and the following formula is used to calculate : ； wherein, represents the change in the uncorrected reading of the sulfur hexafluoride gas sensor before and after the addition of the quantitative oxygen; represents the change in the actual measured oxygen concentration of the oxygen sensor before and after the addition of the quantitative oxygen.

3. The calibration method of a sulfur hexafluoride gas recovery plant according to claim 1 or 2, characterized in that, Determined using the following method: The concentration of sulfur hexafluoride gas and oxygen gas is kept constant, and a constant amount of water vapor is added to the first container from a water vapor tank connected to the first container, and the following formula is used for calculation : ； wherein, represents the change value of the uncorrected reading of the sulfur hexafluoride gas sensor before and after the addition of a constant amount of water vapor; represents the change value of the actual water vapor concentration measured by the humidity sensor before and after the addition of a constant amount of water vapor.

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