A method and system for evaluating gas insulation strength based on insulating gas current sensitivity

Abstract

The present invention provides a method and system for evaluating gas insulation strength based on the current sensitivity of insulating gas, belonging to the technical field of new environmentally friendly insulating materials for power systems, including: Step S1, building a steady-state Townsend test platform to obtain the initial current; Step S2, measuring the ionization current of SF6 gas at different distances and reduced electric fields through the steady-state Townsend test platform; Step S3, establishing a curve graph of the ionization current and electric field of SF6 gas, and extracting the electric field when the tangent line at the time when the ionization current is 8 pA passes through zero; Step S4, comparing the electric field when the tangent line at the time when the ionization current of the gas to be tested and SF6 gas passes through zero at 8 pA, and obtaining the insulation strength of the gas to be tested relative to SF6 gas. The present invention adopts the above-mentioned method and system for evaluating gas insulation strength based on the current sensitivity of insulating gas, which is used to quickly evaluate the gas insulation strength and provide a fast and effective means for evaluating the insulation strength of SF6 alternative gases or mixed gases.

Description

Technical Field

[0001] The present invention relates to the technical field of new environmentally friendly insulating materials for power systems, and in particular to a method and system for evaluating gas insulation strength based on insulating gas current sensitivity. Background Art

[0002] Sulfur hexafluoride (SF6) gas, due to its unique chemical properties, has a wide range of applications in the field of power equipment. Its high insulation strength ensures the efficient and safe operation of power transmission and distribution systems, making SF6 an indispensable component in key power equipment such as high-voltage electrical appliances, transformers, circuit breakers, and gas-insulated transmission lines. However, although SF6 plays a vital role in the electrical industry, its impact on the environment cannot be ignored. The global warming potential (GWP) of sulfur hexafluoride is extremely high, about 23,400 times that of carbon dioxide (CO2), which means that for every kilogram of SF6 gas emitted, its contribution to global warming is equivalent to the emission of 23.4 tons of CO2. Therefore, in the face of increasingly severe environmental protection challenges, finding and developing new environmentally friendly gases that can replace SF6 has become a research hotspot in the interdisciplinary field of electrical and chemical engineering.

[0003] At present, the evaluation of the dielectric strength of gases mainly relies on a variety of discharge test methods. These tests include gas breakdown characteristic test, steady-state Thomson test, and partial discharge test. After decades of unremitting efforts and test screening by scientific researchers, several alternative gases with practical application value have been discovered and confirmed, such as perfluoroisobutyronitrile (C4F7N), octafluorocyclobutane (c~C4F8), trifluoroiodomethane (CF3I) and perfluoroketone compounds (such as C5F 10 O, C6F12O), etc. These gases are regarded as potential substitutes for traditional insulating gases (such as SF6) due to their excellent insulation properties and environmental protection characteristics.

[0004] However, the phenomenon of gas insulation and breakdown is an extremely complex and variable macroscopic physical process. The critical breakdown field strength measured in the test is not a fixed value, but is affected by many factors, including differences in electric field types (such as uniform electric field, slightly non-uniform electric field and extremely non-uniform electric field), temperature and pressure conditions of the test environment, materials used for electrodes and their geometric shapes, etc. These factors are intertwined and act together on the insulation properties of the gas, resulting in the same gas showing completely different insulation strength performance under different test conditions. Therefore, when evaluating the insulation strength of the gas, the influence of these factors must be fully considered to ensure the accuracy and reliability of the evaluation results.

[0005] In addition, in the field of insulating gas insulation strength assessment, traditional mathematical methods such as the Boltzmann equation and Monte~Carlo simulation are also often used. These methods can theoretically describe the motion state and collision process of electrons in the gas more accurately, but a large number of parameters need to be input into the equation, including but not limited to various collision cross sections of the gas (such as oscillation-excited collision cross section, ionization cross section, elastic kinetic energy transfer collision cross section, inelastic excitation collision cross section and adsorption collision cross section) and electron energy distribution function. The acquisition of these parameters often requires complex experimental measurements and theoretical calculations, which is not only cumbersome, but also has certain uncertainties.

[0006] However, the above two methods still have some limitations in practical applications. For example, although the Boltzmann equation can describe the motion state and energy distribution of electrons in an electric field, it usually requires simplification and assumptions about the collision process between electrons and gas molecules, which may limit the accuracy of the calculation results. Although Monte~Carlo simulation can simulate the random motion process of electrons in gas, it is computationally intensive, time-consuming, and requires high computer performance, which limits its application in large-scale evaluations.

[0007] Therefore, a new gas insulation strength evaluation method is urgently needed to solve the above problems. Summary of the invention

[0008] The purpose of the present invention is to provide a method and system for evaluating the insulation strength of gas based on the current sensitivity of insulating gas. The method builds a steady-state Townsend test platform, uses ultraviolet light to excite electrons to obtain initial current, and then measures the ionization current of SF6 gas at different distances and reduced electric fields. By establishing a curve of SF6 gas ionization current and field strength, and extracting the electric field when the tangent line passes through zero when the ionization current is 8pA, the electric field of the gas to be tested is compared with that of SF6 gas, thereby evaluating the insulation strength of the gas to be tested. The method has the characteristics of high accuracy and strong reliability, is suitable for the insulation strength evaluation of various insulating gases, and provides strong technical support for the safe operation of equipment such as power systems.

[0009] To achieve the above object, the present invention provides a method for evaluating gas insulation strength based on insulating gas current sensitivity, comprising the following steps:

[0010] Step S1, building a steady-state Townsend test platform to obtain an initial current;

[0011] Step S2, measuring the ionization current of SF6 gas at different distances and reduced electric fields through a steady-state Townsend test platform;

[0012] Step S3, establishing a curve diagram of SF6 gas ionization current and field strength, and extracting the electric field when the tangent line crosses zero when the ionization current is 8 pA;

[0013] Step S4, comparing the electric field of the gas to be tested with that of the SF6 gas when the tangent line crosses zero when the ionization current is 8 pA, to obtain the insulation strength of the gas to be tested relative to the SF6 gas.

[0014] Preferably, in step S1, the method for obtaining the initial current is: using ultraviolet light to excite the electrons of the 2nm platinum metal coating to obtain the initial current.

[0015] Preferably, in step S1, the curve of current versus reduced electric field strength obtained by SST test measurement is completed under uniform test conditions.

[0016] Preferably, in step S2, the distance range is 1-10 mm.

[0017] Preferably, in step S2, the reduced electric field range is 240~450Td.

[0018] Preferably, in step S3, extracting the electric field when the tangent line crosses zero when the ionization current is 8 pA comprises the following steps:

[0019] Step S31: Based on the initial current obtained in step S1, the ionization current in the outer loop is calculated using the following formula:

[0020] ;

[0021] in, is the ionization current; Ionization coefficient; The distance between electrodes; is the initial current;

[0022] Step S32: Obtain the following form of ionization current through local linearization processing:

[0023] ;

[0024] in, is the electric field when the tangent line crosses zero when the ionization current is 8pA; is the slope of the ionization current as the electric field changes; is the intercept.

[0025] Preferably, in step S3, the 8pA ionization current is the point in the loop where the slope between the electric field and the current is the largest.

[0026] Based on the above-mentioned gas insulation strength evaluation method based on insulating gas current sensitivity, the present invention also provides a system for the gas insulation strength evaluation method based on insulating gas current sensitivity, including an initial current acquisition module, an ionization current measurement module, an electric field extraction module and an insulation strength evaluation module;

[0027] Among them, the initial current acquisition module is used to build a steady-state Townsend test platform to obtain the initial current;

[0028] The ionization current measurement module is used to measure the ionization current of SF6 gas at different distances and reduced electric fields through a steady-state Townsend test platform;

[0029] The electric field extraction module is used to establish a curve diagram of SF6 gas ionization current and field strength, and to extract the electric field when the tangent line crosses zero when the ionization current is 8pA;

[0030] The evaluation module is used to compare the electric field when the tangent of the gas to be tested and the SF6 gas cross zero when the ionization current is 8pA, so as to obtain the insulation strength of the gas to be tested relative to the SF6 gas.

[0031] Preferably, the steady-state Townsend test platform includes a test chamber, one side of the test chamber is connected to a controllable flow meter, the other side of the controllable flow meter is connected to a gas cylinder, and the test chamber is also connected in series with a DC voltage source and a picoammeter.

[0032] Preferably, an ultraviolet lamp and two electrodes with a 2nm platinum metal coating are provided in the test chamber.

[0033] Therefore, the present invention adopts the above-mentioned gas insulation strength evaluation method and system based on insulating gas current sensitivity, and the beneficial technical effects are as follows:

[0034] (1) Improve the accuracy of the assessment: The present invention builds a steady-state Townsend test platform and uses ultraviolet light to accurately excite the electrons of the 2nm platinum metal coating to obtain the initial current. This step ensures that the initial conditions of the test are highly consistent. Subsequently, the ionization current of the SF6 gas is accurately measured within a distance range of 1 to 10 mm and a reduced electric field range of 240 to 450Td. By establishing a relationship curve between the ionization current and the field strength, and paying special attention to the electric field when the tangent crosses zero when the ionization current is 8pA, this method can capture the most sensitive change point between the current and the electric field, thereby significantly improving the accuracy of the insulation strength assessment.

[0035] (2) Enhanced applicability: The present invention not only conducts a detailed study on SF6 gas, but also constructs a universal relationship model between ionization current and field strength, so that the method can be easily extended to other insulating gases. This means that whether it is the performance evaluation of existing insulating gases or the research and development of new insulating gases, the present invention can provide a unified and standardized evaluation process, greatly enhancing the versatility and applicability of the technology.

[0036] (3) Improved safety: By accurately measuring and evaluating the insulation strength of insulating gas, the present invention can promptly detect potential insulation defects in electrical equipment. Especially in environments with high voltage and high electric field strength, this accurate assessment capability is crucial to preventing electrical accidents. By providing early warning and taking measures, the risk of equipment failure and safety accidents can be significantly reduced, and the safe operation level of the entire power system can be improved.

[0037] (4) Promoting technological innovation: The invention not only solves some problems in existing insulation strength evaluation methods, such as insufficient accuracy and limited scope of application, but also provides new ideas and methods for research and application in related fields. For example, by introducing the steady-state Townsend test platform and the relationship model between ionization current and field strength, new technical means and theoretical basis are provided for the performance evaluation of insulating gas. This innovative method not only promotes the development of insulation strength evaluation technology, but also provides new ideas for researchers in related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A flow chart of a method for evaluating gas insulation strength based on insulating gas current sensitivity according to the present invention;

[0039] Figure 2 It is a structural schematic diagram of a gas insulation strength evaluation system based on insulating gas current sensitivity of the present invention;

[0040] Figure 3 It is a schematic diagram of the structure of the steady-state Townsend test platform;

[0041] Figure 4 is the ionization current in SF6 gas under different discharge gaps and reduced electric fields;

[0042] Figure 5 is the relationship between ionization current and field strength in N2 gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] 1. Test chamber; 2. UV lamp; 3. Picoammeter; 4. DC voltage source; 5. Controllable flow meter; 6. Gas cylinder; 7. Electrode; 8. Shielding room. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not intended to limit the embodiments of the present invention. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions.

[0046] It should be noted that the terms "include", "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or server comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or devices.

[0047] Like reference numerals and letters denote similar items in the following drawings, and thus, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0048] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0049] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] Embodiment 1

[0051] like Figure 1 As shown, the present invention provides a gas insulation strength evaluation method based on the current sensitivity of insulating gas, which can efficiently and accurately evaluate the insulation performance of different gases, and is particularly suitable for the screening of new environmentally friendly gases that replace the traditional high greenhouse effect gas sulfur hexafluoride (SF6). The evaluation method includes the following steps:

[0052] Step S1: build a steady-state Townsend test platform (SST platform) to obtain the initial current.

[0053] like Figure 3 As shown, the steady-state Townsend test platform is arranged in a shielded room 8. The steady-state Townsend test platform comprises a test chamber 1, one side of the test chamber 1 is connected to a controllable flow meter 5, the other side of the controllable flow meter 5 is connected to a gas cylinder 6, and the test chamber 1 is also connected in series with a DC voltage source 4 and a picoammeter 3.

[0054] An ultraviolet lamp 2 and two electrodes 7 with a 2 nm platinum metal coating are arranged in the test chamber 1 .

[0055] The steady-state Townsend test platform uses ultraviolet light to illuminate a quartz glass electrode coated with a 2nm platinum metal coating, which stimulates the electrons of the platinum metal to escape (work function is 4.1eV) to form an initial current. This step provides a stable and controllable starting condition for subsequent current measurement.

[0056] Step S2: Figure 4 As shown, this embodiment accurately measures the ionization current of SF6 gas in the range of 1-10 mm (the distance between two parallel plate electrodes) and the range of reduced electric field strength of 240-450 Td. These measurement data are plotted as a curve of ionization current versus reduced electric field strength, providing an experimental basis for subsequent insulation strength evaluation.

[0057] Step S3, establish a curve graph of SF6 gas ionization current and field strength, and extract the electric field when the tangent line passes through zero when the ionization current is 8pA (8pA ionization current is the point with the largest slope between the electric field and current in the loop).

[0058] Extracting the electric field when the tangent line crosses zero when the ionization current is 8 pA includes the following steps:

[0059] Step S31: Based on the initial current obtained in step S1, the ionization current in the outer loop is calculated using the following formula:

[0060] ;

[0061] in, is the ionization current; Ionization coefficient; The distance between electrodes; is the initial current;

[0062] Step S32: Obtain the following form of ionization current through local linearization processing:

[0063] ;

[0064] in, is the electric field when the tangent line crosses zero when the ionization current is 8pA; is the slope of the ionization current as the electric field changes; is the intercept.

[0065] When the gas When it is large, it is sensitive to changes in electric field, usually It is also relatively large. If the insulation strength reaches that of SF6, it can be used as the insulating gas for electrical equipment such as GIL.

[0066] when When it is larger, it means that the gas molecular structure is stable and it is not easy to ionize in the process of increasing the electric field, that is, lose electrons and cause electron avalanche, and it has good insulation properties.

[0067] Step S4: The gas to be tested (such as Figure 5 As shown, taking N2 as an example), the electric field when the tangent line crosses zero when the ionization current is 8pA with that of SF6 gas is compared to obtain the insulation strength of the gas to be tested relative to SF6 gas.

[0068] Specifically, the gas to be tested is mixed with SF6 gas. By comparison, the insulation strength of the gas to be tested relative to SF6 is obtained. K . Measured typical gases (SF6, N2, CO2, CF4, C2F6, C3F6, C3F8, c~C4F8, CF3I, C4F7N, C5F 10 O, He, SO2F2, C3H2F4, Ne) As shown in Table 1, the insulation gas K The insulation properties of different gases can be compared intuitively.

[0069] Table 1 Initial dielectric strength of typical insulating gases E i and K value

[0070]

[0071] like Figure 2 As shown, the present invention also provides a system for a gas insulation strength evaluation method based on insulating gas current sensitivity, comprising an initial current acquisition module, an ionization current measurement module, an electric field extraction module and an insulation strength evaluation module;

[0072] Among them, the initial current acquisition module is used to build a steady-state Townsend test platform to obtain the initial current;

[0073] The ionization current measurement module is used to measure the ionization current of SF6 gas at different distances and reduced electric fields through a steady-state Townsend test platform;

[0074] The electric field extraction module is used to establish a curve diagram of SF6 gas ionization current and field strength, and to extract the electric field when the tangent line crosses zero when the ionization current is 8pA;

[0075] The evaluation module is used to compare the electric field when the tangent of the gas to be tested and the SF6 gas cross zero when the ionization current is 8pA, so as to obtain the insulation strength of the gas to be tested relative to the SF6 gas.

[0076] Therefore, the present invention adopts the above-mentioned gas insulation strength evaluation method and system based on the current sensitivity of insulating gas. This method builds a steady-state Townsend test platform, uses ultraviolet light to excite electrons to obtain initial current, and then measures the ionization current of SF6 gas at different distances and reduced electric fields. By establishing a curve graph of SF6 gas ionization current and field strength, and extracting the electric field when the tangent line passes through zero when the ionization current is 8pA, the gas to be tested is compared with the electric field of SF6 gas, thereby evaluating the insulation strength of the gas to be tested. This method has the characteristics of high accuracy and strong reliability, is suitable for the insulation strength evaluation of various insulating gases, and provides strong technical support for the safe operation of equipment such as power systems.

[0077] It is worth noting that the contents not elaborated in detail in this application are all prior art and are well known to those skilled in the art.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for evaluating gas insulation strength based on insulating gas current sensitivity, characterized in that: The following steps are involved: Step S1, building a steady-state Townsend test platform to obtain an initial current; Step S2, measuring the ionization current of SF6 gas at different distances and reduced electric fields through a steady-state Townsend test platform; Step S3, establishing a curve diagram of SF6 gas ionization current and field strength, and extracting the electric field when the tangent line crosses zero when the ionization current is 8 pA; Step S4, comparing the electric field of the gas to be tested with that of the SF6 gas when the tangent line crosses zero when the ionization current is 8 pA, to obtain the insulation strength of the gas to be tested relative to the SF6 gas; In step S3, extracting the electric field when the tangent line crosses zero when the ionization current is 8 pA comprises the following steps: Step S31: Based on the initial current obtained in step S1, the ionization current in the outer loop is calculated using the following formula: ； in, is the ionization current; Ionization coefficient; The distance between electrodes; is the initial current; Step S32: Obtain the following form of ionization current through local linearization processing: ； in, is the electric field when the tangent line crosses zero when the ionization current is 8pA; is the slope of the ionization current as the electric field changes; is the intercept; In step S3, the 8pA ionization current is the point where the slope change rate between the electric field and the current in the outer loop is the largest.

2. A method for evaluating gas insulation strength based on insulating gas current sensitivity according to claim 1, characterized in that: In step S1, the method for obtaining the initial current is: using ultraviolet light to excite the electrons of the 2nm platinum metal coating to obtain the initial current.

3. A method for evaluating gas insulation strength based on insulating gas current sensitivity according to claim 2, characterized in that: In step S1, the curve of current versus reduced electric field intensity obtained by SST test measurement is completed under uniform test conditions.

4. A method for evaluating gas insulation strength based on insulating gas current sensitivity according to claim 3, characterized in that: In step S2, the distance range is 1-10 mm.

5. A method for evaluating gas insulation strength based on insulating gas current sensitivity according to claim 4, characterized in that: In step S2, the reduced electric field range is 240~450Td.

6. A system for implementing the gas insulation strength evaluation method based on insulating gas current sensitivity as described in any one of claims 1 to 5, characterized in that: It includes an initial current acquisition module, an ionization current measurement module, an electric field extraction module and an insulation strength evaluation module; Among them, the initial current acquisition module is used to build a steady-state Townsend test platform to obtain the initial current; The ionization current measurement module is used to measure the ionization current of SF6 gas at different distances and reduced electric fields through a steady-state Townsend test platform; The electric field extraction module is used to establish a curve diagram of SF6 gas ionization current and field strength, and to extract the electric field when the tangent line crosses zero when the ionization current is 8pA; The evaluation module is used to compare the electric field when the tangent of the gas to be tested and the SF6 gas cross zero when the ionization current is 8pA, so as to obtain the insulation strength of the gas to be tested relative to the SF6 gas.

7. A system for evaluating gas insulation strength based on insulating gas current sensitivity according to claim 6, characterized in that: The steady-state Townsend test platform includes a test chamber, one side of the test chamber is connected to a controllable flow meter, the other side of the controllable flow meter is connected to a gas cylinder, and the test chamber is also connected in series with a DC voltage source and a picoammeter.

8. The system of the method for evaluating gas insulation strength based on insulating gas current sensitivity according to claim 7, characterized in that: The test chamber is equipped with an ultraviolet lamp and two electrodes with a 2nm platinum metal coating.

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