Defect resistance evaluation method and system for perfluoroisobutyronitrile mixed insulating gas

Abstract

The invention discloses a defect resistance evaluation method and system for perfluoroisobutyronitrile mixed insulating gas, and relates to the field of insulating gas performance evaluation.The defect resistance evaluation method comprises the steps that a test platform is built, and mixed insulating gas to be evaluated is filled; applying a gradually increased power frequency high voltage to obtain a corresponding voltage when the local discharge capacity reaches a preset value; continuing to increase the voltage to obtain a corresponding partial discharge amount when the voltage reaches a preset value; a breakdown voltage is obtained until the needle-plate electrode gap is broken down; calculating a first characterization factor and a second characterization factor; changing gas parameters, and repeating related steps to obtain characterization factors under different gas parameters; and comparing the values of the characterization factors, and evaluating the defect resistance of different mixed insulating gases. The defect resistance of mixed insulating gases with different formulas can be comprehensively compared from two complementary dimensions of discharge start and discharge development.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of insulating gas performance evaluation, more particularly to a kind of perfluoroisobutyl nitrile mixed insulating gas defect resistance evaluation method and system. BACKGROUND

[0002] Gas insulated electrical equipment is a key component of modern power systems, and the performance of its insulating medium is directly related to the reliability and safety of the equipment; With the increasingly stringent environmental requirements, the sulfur hexafluoride gas with extremely high global warming potential (GWP) is facing the pressure of being replaced, and the environmentally friendly mixed insulating gas represented by perfluoroisobutyl nitrile (CF3CF2C(O)N(CF3)2, FIBN) has become a key research direction and has gradually been applied in gas insulated lines, circuit breakers and other high-voltage equipment.

[0003] However, metal particles, burrs and other sharp defects will inevitably occur in the long-term operation of the equipment due to manufacturing, installation or aging, which will cause partial discharge and eventually lead to insulation failure. Therefore, it is crucial to evaluate the tolerance of the insulating gas under the condition of defects, i.e. the defect resistance, for the engineering selection of gas formula. Currently, although breakdown tests, partial discharge inception voltage tests and other methods can be used to preliminarily evaluate the insulating performance of the gas, these methods often focus on the performance of the gas in ideal uniform electric field or at the inception point of discharge, and lack quantitative characterization of the gas's ability to suppress the development of discharge from the inception to the final breakdown. This leads to a single evaluation dimension and cannot fully reflect the real tolerance performance of the gas under actual defect conditions.

[0004] Furthermore, the existing technology focuses on the influence of different proportions and different buffer gases on the basic insulation strength of the mixed gas. Although these studies provide important basic data, they have not yet formed a standardized test and analysis method specifically for evaluating the defect resistance of the mixed gas. The electrode structure, defect simulation method, voltage application procedure and evaluation index used in different studies are different, resulting in fragmented data that is difficult to compare effectively and cannot provide direct and unified decision-making basis for optimizing the gas formula in engineering.

[0005] In addition, some more complex evaluation methods may rely on special test devices or sophisticated simulation calculations, which can provide a deeper understanding, but are complex to operate, costly and require high professional skills, making it difficult to quickly and batch select multiple gas formulas in the research and development stage. To some extent, this restricts the optimization efficiency and application promotion speed of environmentally friendly insulating gas formulas.

[0006] Therefore, how to design a perfluoroisobutyl nitrile mixed insulating gas defect resistance evaluation method and system to support the rapid comparison and optimization selection of different gas formulas is a problem that needs to be solved by those skilled in the art.​ Summary of the Invention

[0007] In view of this, the present invention provides a method and system for evaluating the resistance to defects of a perfluoroisobutyronitrile mixed insulating gas, addressing the current lack of methods for evaluating environmentally friendly... The lack of effective methods for evaluating the defect resistance of mixed insulating gases has led to difficulties in optimizing key parameters such as buffer gas type, mixing ratio, and gas pressure. This method extracts key electrical parameters and calculates standardized characterization factors by simulating the discharge process under typical defects, thereby enabling a quantitative comparison and ranking of the defect resistance performance of different gas formulations, providing a direct basis for selecting high-performance gas formulations.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for evaluating the resistance to defects of a perfluoroisobutyronitrile mixed insulating gas, comprising the following steps: S1. Construct a test platform. The sealed cavity of the test platform is equipped with a needle-plate electrode structure to simulate the tip defects on the electrode surface. After evacuating the sealed cavity, fill it with the electrode to be evaluated. Mix the insulating gas to the target pressure; S2. Apply a gradually increasing power frequency high voltage to the needle electrode while keeping the plate electrode grounded, until the local discharge reaches a preset value. The voltage corresponding to time ; S3. Continue to increase the voltage until the voltage reaches the preset value. The corresponding partial discharge quantity ; S4. Continue to increase the voltage until the needle-plate electrode gap breaks down, and obtain the breakdown voltage. ; S5. Calculation is used for characterization. The first characterizing factor of the defect resistance of mixed insulating gases Second characterization factor ; S6, Change By refining the gas parameters of the mixed insulating gas and repeating steps S2 to S5, the first characterization factor under different gas parameters is obtained. Second characterization factor ; S7. By comparing the first characterization factor Second characterization factor The numerical value is used to evaluate the value under different parameter conditions. The strength of defect resistance of mixed insulating gases.

[0009] Preferably, the needle-plate electrode satisfies the following condition: the maximum electric field strength on the surface of the needle electrode is more than 4 times the average electric field strength between the electrodes.

[0010] Preferably, the Mixed insulating gas is It is prepared by mixing with a buffer gas at a certain volume fraction ratio, wherein the buffer gas is selected from... , , One or two of them.

[0011] Preferably, the preset value The selection satisfies: ,and The value of makes the corresponding . Preferably, the first characterization factor satisfy Second characterization factor satisfy .

[0012] Preferably, the gas parameters include the type of buffer gas, The mixing ratio and gas pressure.

[0013] Preferably, the standard for evaluating the strength of defect resistance is: under different gas parameter conditions... The first characterization factor calculated from the mixed insulating gas. Second characterization factor The smaller the value, the stronger its defect resistance.

[0014] Secondly, the present invention provides a defect resistance assessment system for a perfluoroisobutyronitrile mixed insulating gas, used to implement the aforementioned defect resistance assessment method for the perfluoroisobutyronitrile mixed insulating gas, comprising: A sealed cavity, wherein the sealed cavity is provided with an air inlet and a grounding terminal; A needle-plate electrode assembly, located inside a sealed cavity, includes a needle electrode and a plate electrode; A high-voltage introduction component includes a high-voltage conductive rod penetrating a sealed cavity and an insulating sleeve, wherein one end of the high-voltage conductive rod extends into the sealed cavity and is connected to a needle electrode; A grounding assembly includes a ground potential conductive rod, one end of which is connected to a plate electrode, and the other end is used for grounding; The power frequency high voltage power supply has its output terminal connected to a high voltage conductive rod, which is used to apply power frequency high voltage to the needle electrode; The signal detection module includes a coupling impedance and a partial discharge comprehensive analyzer. The coupling impedance is connected in series in the grounding loop of the ground potential conductive rod to couple the partial discharge signal. The input terminal of the partial discharge comprehensive analyzer is connected to the coupling impedance to measure and record the partial discharge quantity. The control and calculation module is communicatively connected to both the power frequency high-voltage power supply and the partial discharge comprehensive analyzer. It controls the power frequency high-voltage power supply to boost voltage according to a preset program, receives partial discharge data from the partial discharge comprehensive analyzer, and calculates the defect resistance performance characterization factor. and Complete the performance evaluation.

[0015] As can be seen from the above technical solution, compared with the prior art, the technical solution of the present invention has the following beneficial effects: 1. This method, by clearly defining the field strength conditions of the needle-plate electrode, standardizing the power frequency high voltage test procedure, and using calculation formulas based on key parameters such as specific discharge quantity and breakdown voltage, provides a repeatable and comparable basis for testing the defect resistance performance of mixed gases under different buffer gas types, mixing ratios, and gas pressures, overcoming the problem that results are difficult to compare horizontally due to inconsistent test conditions.

[0016] 2. The scheme not only focuses on the withstand voltage of the gas under a fixed discharge amount, but also on the degree of discharge development under a specific voltage before breakdown. The first characterization factor focuses on the gas's ability to suppress the initiation and initial development of discharge, while the second characterization factor focuses on the gas's ability to suppress the violent growth of discharge under a higher field strength. The comprehensive evaluation of the gas's defect resistance performance is more comprehensive and reliable.

[0017] 3. The core hardware of this evaluation method consists of a sealed cavity, needle-plate electrodes, a power frequency high voltage source, and a standard-compliant partial discharge detector. The steps, from setting the electrodes, gas filling, step-by-step voltage increase, data acquisition to calculation and analysis, are logically clear and do not rely on special or expensive equipment, thus lowering the threshold for implementation and facilitating its promotion and application in R&D laboratories or testing institutions. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 A flowchart illustrating a method for evaluating the resistance to defects of a perfluoroisobutyronitrile mixed insulating gas, as provided in an embodiment of the present invention; Figure 2A framework diagram for evaluating the defect resistance of a perfluoroisobutyronitrile mixed insulating gas is provided in this embodiment of the invention. Figure 3 The 0.7MPa 9% provided in the embodiments of the present invention / 91% Partial emission-phase distribution of mixed gas at 200 pC; Figure 4 The 0.7MPa 9% provided in the embodiments of the present invention / 91% Partial discharge-phase distribution diagram of mixed gas at 56.6 kV; Figure 5 The 0.6MPa 9% provided in the embodiments of the present invention / 91% Partial emission-phase distribution of mixed gas at 200 pC; Figure 6 The 0.6MPa 9% provided in the embodiments of the present invention / 91% Partial discharge-phase distribution diagram of mixed gas at 56.6 kV; In the diagram, 1 is the needle electrode, 2 is the plate electrode, 3 is the high-voltage conductive rod, 4 is the ground potential conductive rod, 5 is the insulating sleeve, 6 is the air inlet, 7 is the sealed cavity, 8 is the grounding terminal, 9 is the power frequency high-voltage power supply, 10 is the coupling impedance, 11 is the partial discharge comprehensive analyzer, and 12 is the control and calculation module. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1; like Figure 1 As shown, this embodiment provides a method for evaluating the resistance to defects of a perfluoroisobutyronitrile mixed insulating gas, including the following steps: S1. Construct a test platform. The sealed cavity of the test platform is equipped with a needle-plate electrode structure to simulate the tip defects on the electrode surface. After evacuating the sealed cavity, fill it with the electrode to be evaluated. Mix the insulating gas to the target pressure; S2. Apply a gradually increasing power frequency high voltage to the needle electrode while keeping the plate electrode grounded, until the local discharge reaches a preset value. The voltage corresponding to time ; S3. Continue to increase the voltage until the voltage reaches the preset value. The corresponding partial discharge quantity ; S4. Continue to increase the voltage until the needle-plate electrode gap breaks down, and obtain the breakdown voltage. ; S5. Calculation is used for characterization. The first characterizing factor of the defect resistance of mixed insulating gases Second characterization factor ; S6, Change By refining the gas parameters of the mixed insulating gas and repeating steps S2 to S5, the first characterization factor under different gas parameters is obtained. Second characterization factor ; S7. By comparing the first characterization factor Second characterization factor The numerical value is used to evaluate the value under different parameter conditions. The strength of defect resistance of mixed insulating gases.

[0022] This method, by constructing a standardized needle-plate electrode testing platform and a unified boost detection process, utilizes two complementary characterization factors to achieve the evaluation of different formulations from two dimensions: discharge initiation tolerance and discharge development inhibition. A comprehensive and quantitative evaluation of the defect resistance performance of mixed insulating gases; this method is based on conventional high-voltage testing equipment, with a clear process and strong operability, providing a reliable and practical evaluation tool for the optimization and engineering application of environmentally friendly insulating gas formulations.

[0023] The following provides a further detailed explanation of each step and related features in the above method; In this implementation, the needle-plate electrode satisfies the following condition: the maximum electric field strength on the surface of the needle electrode is more than 4 times the average electric field strength between the electrodes; Its purpose is to ensure that under experimental conditions, it can effectively and stably simulate the extremely non-uniform electric field defects caused by metal burrs, particles and other particles in actual equipment. This can be achieved by using a needle tip with a very small radius of curvature (e.g. 0.1-1 mm) and a specific inter-electrode distance, so that a high field strength region sufficient to induce discharge can be reached near the needle tip under a low applied voltage, thereby accurately simulating insulation weaknesses and enabling subsequent measurement data to truly reflect the gas's tolerance characteristics under defect conditions.

[0024] In this implementation, Mixed insulating gas is It is prepared by mixing with a buffer gas at a certain volume fraction ratio, wherein the buffer gas is selected from... , , One or two of them; As a primary insulating medium, it is typically used due to its high insulating strength, but its high liquefaction temperature and high cost necessitate mixing with buffer gases to optimize overall performance. The selected... , , All of them are common, inexpensive, and environmentally friendly gases. and Its main function is to dilute and regulate the liquefaction temperature, while The addition of [a substance] can help suppress the formation of carbides during the discharge process and improve gas stability under certain specific circumstances.

[0025] In this implementation, the preset value The selection satisfies: ,and The value of makes the corresponding . Under this limitation, Must be within the starting discharge voltage With breakdown voltage In between, ensure that the measurement point is in the development stage where discharge has occurred but has not yet led to complete breakdown; furthermore... The value of makes Significantly greater than This is to ensure that the collected data is accurate. It is an easily measurable discharge quantity, which can effectively characterize the degree of intensification of discharge activity after voltage increase, avoiding the need to select data points in regions where the discharge quantity changes slowly, thus ensuring the sensitivity and effectiveness of subsequent characterization factor calculations.

[0026] In this implementation, the first characterization factor satisfy Second characterization factor satisfy .

[0027] Due to the initial discharge voltage Always below the breakdown voltage Therefore Greater than 0 and less than 1 The closer the voltage is to 1, the closer the initiation voltage is to the breakdown voltage, meaning the stronger the gas's ability to resist discharge initiation at the defect location; because Therefore Greater than 1, The smaller the value, the better the voltage from... Rise to During the process, the slower the increase in discharge, the stronger the ability of gas to suppress the development of discharge; the two factors quantify the defect resistance performance from different perspectives.

[0028] In this implementation, the gas parameters include the type of buffer gas, The mixing ratio and gas pressure; The type of buffer gas affects the thermodynamic, electrical, and chemical properties of the gas mixture. The mixing ratio determines the insulation strength and cost of the mixed gas, and gas pressure is an operating parameter closely related to equipment size and insulation strength in engineering design; it clarifies the optimization dimension targeted by the evaluation method in this embodiment, that is, to study and compare different types of buffer gases and different The concentration and defect resistance of gases under different pressures provide data support for selecting the optimal formulation combination for specific application scenarios.

[0029] In this implementation, the standard for evaluating the strength of defect resistance is: under different gas parameter conditions... The first characterization factor calculated from the mixed insulating gas. Second characterization factor The smaller the value, the stronger its defect resistance. It transforms the complex comparison of insulation performance into a direct comparison of two calculated values. The smaller the value, the smaller the proportion of the voltage that the gas can withstand when the same tiny discharge occurs to its final breakdown capability. Conversely, the larger the voltage margin between the start of discharge and the final breakdown, the better the potential for resistance to defect development. The smaller the value, the slower the rate of discharge growth as the voltage increases, meaning the stronger the gas's ability to suppress discharge deterioration. If both values ​​are small, it indicates that the gas formulation can both delay the discharge initiation and effectively suppress the discharge development when defects exist, thus exhibiting stronger defect resistance.

[0030] like Figure 2 As shown, this embodiment also provides a defect resistance assessment system for a perfluoroisobutyronitrile mixed insulating gas, used to implement the above-mentioned defect resistance assessment method for the perfluoroisobutyronitrile mixed insulating gas, including: A sealed cavity 7 is provided with an air inlet 6 and a grounding terminal 8. The needle-plate electrode assembly is located inside the sealed cavity 7 and includes a needle electrode 1 and a plate electrode 2. The high voltage introduction component includes a high voltage conductive rod 3 that penetrates the sealed cavity 7 and an insulating sleeve 5, wherein one end of the high voltage conductive rod 3 extends into the sealed cavity 7 and is connected to the needle electrode 1. The grounding assembly includes a ground potential conductive rod 4, one end of which is connected to the plate electrode 2, and the other end is used for grounding; The power frequency high voltage power supply 9 has its output terminal connected to the high voltage conductive rod 3, which is used to apply power frequency high voltage to the needle electrode 1. The signal detection module includes a coupling impedance 10 and a partial discharge comprehensive analyzer 11. The coupling impedance 10 is connected in series to the grounding loop of the ground potential conductive rod 4 for coupling partial discharge signals. The input terminal of the partial discharge comprehensive analyzer 11 is connected to the coupling impedance 10 for measuring and recording the amount of partial discharge. The control and calculation module 12 is communicatively connected to the power frequency high-voltage power supply 9 and the partial discharge comprehensive analyzer 11, respectively. It is used to control the power frequency high-voltage power supply 9 to boost voltage according to a preset program, receive partial discharge data from the partial discharge comprehensive analyzer 11, and calculate the defect resistance performance characterization factor. and Complete the performance evaluation.

[0031] The applied power frequency high voltage at this location is 50 Hz, and the measurements by the partial discharge comprehensive analyzer comply with IEC 60270 or GB / T 7354-2018 standards.

[0032] In the needle-plate electrode assembly, the radius of curvature of the needle electrode 1 is 0.1 mm to 1.0 mm, and the distance between the needle electrode 1 and the plate electrode 2 is adjustable, with an adjustment range of 1 mm to 50 mm.

[0033] The working process of this evaluation system includes: the operator first adjusts the distance between the needle electrode and the plate electrode, and selects a needle tip with a specific radius of curvature to construct a defect model that can produce a predetermined field strength distortion; then, the sealed cavity is evacuated through the air inlet, and filled with a preset air pressure and formula. Mix insulating gas; after preparation is complete, the control and calculation module sends a command to the power frequency high voltage power supply to apply a 50 Hz AC high voltage to the needle electrode introduced into the cavity through the high voltage conductive rod at a preset voltage boost rate, while the plate electrode is reliably grounded through the ground potential conductive rod. Throughout the pressurization process, the system enters the real-time monitoring and data acquisition phase. When the voltage increases, the high-field region at the needle tip will induce ionization and generate a partial discharge pulse. This pulse current is transmitted through the grounding loop, extracted by the coupling impedance connected in series in the loop, and converted into quantitative discharge quantity data by the partial discharge comprehensive analyzer, which is then uploaded to the control and calculation module in real time. This module simultaneously monitors the voltage value and discharge quantity, automatically identifies and records when the discharge quantity first reaches the preset threshold. Voltage at time And when the voltage rises to a preset value The corresponding discharge amount The voltage is continuously increased until the gap breaks down, and the voltage at the moment of breakdown is recorded. Finally, the control and calculation module uses the formula... and The characterization factor is automatically calculated, and the evaluation conclusion of the defect resistance performance is output by comparing the calculation results under different gas formulations.

[0034] Example 2; This embodiment, combined with its specific application scenario, provides a... The evaluation method for the defect resistance of mixed insulating gases includes the following specific implementation steps: 1) Construct a test platform. The sealed cavity of the test platform is equipped with a needle-plate electrode structure to simulate sharp defects on the electrode surface. The needle electrode has a radius of curvature of 0.5 mm, and the distance between the needle and plate electrodes is 10 mm. After setting up the electrodes, a vacuum pump is used to evacuate the cavity, and then the prepared 9% of the material to be evaluated is filled in. / 91% The mixed gas is brought to a pressure of 0.7 MPa; 2) Apply a high voltage to the needle tip electrode, and ground the plate electrode, such as... Figure 3 As shown, while increasing the voltage, a partial discharge comprehensive analyzer is used to measure the partial discharge, and the specific partial discharge level is recorded. The corresponding voltage ; 3) While increasing the voltage, such as Figure 4 As shown, record a specific voltage. Partial discharge at 56.6kV =1015pC; 4) Gradually increase the voltage until the gap breaks down, thus obtaining the breakdown voltage. =66.5kV; 5) Calculate 0.7MPa 9% / 91% The defect resistance characterization factor of the mixed gas is: =51.6 / 66.5=0.77, =1015 / 200=5.1; 6) Change 9% / 91% The pressure of the mixed gas is 0.6 MPa, such as Figure 5 As shown, a specific local discharge rate is obtained. The voltage corresponding to =200pC is: =44.6kV; and such Figure 6 As shown, a specific voltage is obtained. Partial discharge at 56.6kV =962pC; further increasing the voltage yields its breakdown voltage. =61.0kV, from which its =44.6 / 61.0=0.73, =962 / 200=4.8, both of which are less than the values ​​at 0.7MPa; Therefore, 0.6 MPa 9% can be obtained. / 91% The defect resistance of the mixed gas is better than that at 0.7 MPa 9%. / 91% Mixed gases.

[0035] In summary, the above embodiments systematically elucidate the standard procedure of the evaluation method, the physical meaning and selection principles of key parameters, and the composition and working process of the dedicated evaluation system, establishing a complete and clear technical framework for the application of this method; and further illustrating it with specific examples. Taking the testing of mixed gases under different pressures as an example, this paper demonstrates the entire process from experimental operation, data acquisition, calculation and analysis to performance comparison, verifying the feasibility and practicality of the method. Multiple embodiments combined, from the theoretical framework to practical application, fully demonstrate the operability of this evaluation method and its guiding role. The application value of mixed insulating gas formulation optimization.

[0036] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0037] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for evaluating the defect resistance of a perfluoroisobutyronitrile mixed insulating gas, characterized in that, Includes the following steps: S1. Construct a test platform. The sealed cavity of the test platform is equipped with a needle-plate electrode structure to simulate the tip defects on the electrode surface. After evacuating the sealed cavity, fill it with the electrode to be evaluated. Mix the insulating gas to the target pressure; S2. Apply a gradually increasing power frequency high voltage to the needle electrode while keeping the plate electrode grounded, until the local discharge reaches a preset value. The voltage corresponding to time ; S3. Continue to increase the voltage until the voltage reaches the preset value. The corresponding partial discharge quantity ; S4. Continue to increase the voltage until the needle-plate electrode gap breaks down, and obtain the breakdown voltage. ; S5. Calculation is used for characterization. The first characterizing factor of the defect resistance of mixed insulating gases Second characterization factor ; S6, Change By refining the gas parameters of the mixed insulating gas and repeating steps S2 to S5, the first characterization factor under different gas parameters is obtained. Second characterization factor ; S7. By comparing the first characterization factor Second characterization factor The numerical value is used to evaluate the value under different parameter conditions. The strength of defect resistance of mixed insulating gases.

2. The method for evaluating the resistance to defects of a perfluoroisobutyronitrile mixed insulating gas according to claim 1, characterized in that, The needle-plate electrode satisfies the following condition: the maximum electric field strength on the surface of the needle electrode is more than 4 times the average electric field strength between the electrodes.

3. The method for evaluating the resistance to defects of a perfluoroisobutyronitrile mixed insulating gas according to claim 1, characterized in that, The Mixed insulating gas is It is prepared by mixing with a buffer gas at a certain volume fraction ratio, wherein the buffer gas is selected from... , , One or two of them.

4. The method for evaluating the resistance to defects of a perfluoroisobutyronitrile mixed insulating gas according to claim 1, characterized in that, The preset value The selection satisfies: ,and The value of makes the corresponding .

5. The method for evaluating the resistance to defects of a perfluoroisobutyronitrile mixed insulating gas according to claim 1, characterized in that, The first characterization factor satisfy Second characterization factor satisfy .

6. The method for evaluating the resistance to defects of a perfluoroisobutyronitrile mixed insulating gas according to claim 1, characterized in that, The gas parameters include the type of buffer gas, The mixing ratio and gas pressure.

7. The method for evaluating the resistance to defects of a perfluoroisobutyronitrile mixed insulating gas according to claim 1, characterized in that, The standard for evaluating the strength of defect resistance is: under different gas parameter conditions. The first characterization factor calculated from the mixed insulating gas. Second characterization factor The smaller the value, the stronger its defect resistance.

8. A defect resistance assessment system for a perfluoroisobutyronitrile mixed insulating gas, used to implement the defect resistance assessment method for the perfluoroisobutyronitrile mixed insulating gas as described in any one of claims 1 to 7, characterized in that, include: A sealed cavity (7) is provided with an air inlet (6) and a grounding terminal (8); The needle-plate electrode assembly is located inside the sealed cavity (7) and includes a needle electrode (1) and a plate electrode (2); The high voltage introduction component includes a high voltage conductive rod (3) penetrating the sealed cavity (7) and an insulating sleeve (5), one end of which extends into the sealed cavity (7) and is connected to the needle electrode (1); The grounding assembly includes a ground potential conductive rod (4), one end of which is connected to the plate electrode (2), and the other end is used for grounding; The power frequency high voltage power supply (9) has its output end connected to the high voltage conductive rod (3) and is used to apply power frequency high voltage to the needle electrode (1); The signal detection module includes a coupling impedance (10) and a partial discharge comprehensive analyzer (11). The coupling impedance (10) is connected in series to the grounding loop of the ground potential conductive rod (4) for coupling partial discharge signals. The input terminal of the partial discharge comprehensive analyzer (11) is connected to the coupling impedance (10) for measuring and recording the amount of partial discharge. The control and calculation module (12) is connected to the power frequency high voltage power supply (9) and the partial discharge comprehensive analyzer (11) respectively. It is used to control the power frequency high voltage power supply (9) to boost voltage according to a preset program, receive partial discharge data from the partial discharge comprehensive analyzer (11), and calculate the defect resistance performance characterization factor. and Complete the performance evaluation.

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