A method and system for identifying capacitor faults based on the self-healing characteristics of capacitors using gas.

Abstract

This invention belongs to the technical field of capacitor fault detection and discloses a method and system for identifying capacitor faults based on the self-healing characteristic gas of capacitors. The method includes the following steps: S1, obtaining the actual mass of solid carbon when capacitors with different sheet resistances and carbon-hydrogen ratios fail; S2, calculating the theoretical mass of solid carbon generated by capacitors with different sheet resistances and carbon-hydrogen ratios at different temperatures; the theoretical mass is obtained as follows: calculating the content ratio of hydrocarbon free radicals in the capacitor at different temperatures, the sublimation temperature of carbon, and the mass of carbon in the capacitor; the mass of carbon in the capacitor above the sublimation temperature minus the mass of carbon in the capacitor below the sublimation temperature is the theoretical mass of solid carbon; S3, comparing the theoretical mass of solid carbon in capacitors with different sheet resistances and carbon-hydrogen ratios with the actual mass; capacitors with a theoretical mass greater than the actual mass are faulty, otherwise they are not faulty. This invention solves the problems of low accuracy and efficiency in capacitor fault identification.

Description

Technical Field

[0001] This invention belongs to the technical field of capacitor fault detection, and more specifically, relates to a method and system for identifying capacitor faults based on the self-healing characteristic gas of capacitors. Background Technology

[0002] Metallized film capacitors are crucial components in power systems. Due to their small size and high energy density, they are often used as core equipment in smart grids and renewable energy generation, ensuring the safe and stable operation of the power grid. Metallized film capacitors are composed of vapor-deposited electrodes wound with a polymer film. When the grid voltage reaches the breakdown voltage of the polymer film, the polymer film decomposes, generating small molecule gases and elemental carbon deposits. As the amount of polymer film decomposition increases, on the one hand, more small molecule gases are generated, causing bulging inside the capacitor; on the other hand, the amount of elemental carbon deposits gradually increases, reducing the breakdown voltage inside the capacitor. Both the decomposition products of the polymer film and the actual decomposition products can negatively impact the normal operation of capacitors in the power system.

[0003] Because metallized film capacitors are crucial components of power systems, they cannot be easily removed from the grid. Insulation failure can only be determined by existing characteristic electrical quantities, such as capacitance and dielectric loss. Current fault detection methods are mostly offline, requiring the metallized film capacitors to be taken out of service before detection, which inconveniences the stable operation of the power system and results in low accuracy and efficiency. Therefore, it is necessary to propose a method for identifying capacitor faults under different sheet resistances and hydrocarbon ratios. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a method and system for identifying capacitor faults based on the self-healing characteristics of capacitor gases, thus solving the problems of low accuracy and efficiency in capacitor fault identification.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for identifying capacitor faults based on the self-healing characteristic gas of a capacitor is provided, the method comprising the following steps:

[0006] S1 conducted withstand voltage tests on capacitors with different sheet resistances and carbon-hydrogen ratios to obtain the actual mass of solid carbon when the capacitors with different sheet resistances and carbon-hydrogen ratios failed.

[0007] S2 calculates the theoretical mass of solid carbon produced by capacitors with different sheet resistances and carbon-to-hydrogen ratios at different temperatures; the method for obtaining this theoretical mass is as follows:

[0008] By utilizing the types and thermodynamic parameters of hydrocarbon free radicals in different capacitors at different temperatures, and with the goal of minimizing the Gibbs free energy, the content ratio of hydrocarbon free radicals and the sublimation temperature of carbon in the capacitors at different temperatures are calculated.

[0009] The mass of carbon in the capacitor at different temperatures is calculated using the content ratio of the hydrocarbon free radicals and the total mass of the combined capacitor; the theoretical mass of solid carbon is obtained by subtracting the mass of carbon in the capacitor below the sublimation temperature from the mass of carbon in the capacitor above the sublimation temperature.

[0010] S3 compares the theoretical mass of solid carbon in capacitors with different sheet resistances and carbon-to-hydrogen ratios with their actual mass. Capacitors with a theoretical mass greater than their actual mass fail; otherwise, they do not fail.

[0011] More preferably, in step S1, the calculation steps for the actual mass of the solid carbon are as follows:

[0012] All gases released from the thin film in the capacitor were obtained using a withstand voltage test.

[0013] Obtain the total mass of carbon-containing gases and the total mass of hydrogen-containing gases in all gases;

[0014] The total mass of the thin film resulting from the decomposition of the hydrogen-containing gas is calculated using the total mass of the hydrogen-containing gas.

[0015] The total mass of the thin film minus the total mass of the carbon-containing gas is the actual mass of the solid carbon.

[0016] More preferably, the total mass of carbon-containing gases and the total mass of hydrogen-containing gases in all gases are obtained by gas chromatography analysis.

[0017] More preferably, in step S2, the formula for calculating the Gibbs free energy is as follows:

[0018]

[0019] Where, n i μ is the number of moles of component i. i Let N be the chemical potential of component i, and N be the total number of components.

[0020] More preferably, the chemical potential is calculated using the following formula:

[0021]

[0022] Where, μ i 0 Let be the chemical potential of component i under standard conditions, R be the ideal gas constant, T be the temperature of the system, and a be the chemical potential of component i under standard conditions. i Let i be the activity of component i.

[0023] More preferably, in step S2, the sublimation temperature of carbon is obtained by plotting a thermodynamic curve of temperature and carbon-hydrogen free radical ratio using the ratio of hydrocarbon free radical content in the capacitor at different temperatures. The temperature corresponding to the maximum C2H2 content in the hydrocarbon free radicals in the thermodynamic curve is the sublimation temperature of carbon.

[0024] According to another aspect of the present invention, a system for identifying capacitor faults based on the self-healing characteristic gas of capacitors is provided. This system includes a solid carbon actual mass calculation module, a solid carbon theoretical mass calculation module, and a fault prediction module, wherein:

[0025] The solid carbon actual mass calculation module is used to calculate the actual mass of solid carbon when capacitors with different sheet resistances and carbon-hydrogen ratios fail.

[0026] The solid carbon theoretical mass calculation module is used to calculate the theoretical mass of solid carbon in capacitors with different sheet resistances and carbon-hydrogen ratios.

[0027] The fault prediction module is used to predict whether the capacitor will fail by utilizing the actual and theoretical mass of the solid carbon.

[0028] According to another aspect of the present invention, a system for identifying capacitor faults based on capacitor self-healing characteristic gas is provided, characterized in that the system includes an actuator for performing the above-described method for identifying capacitor faults based on capacitor self-healing characteristic gas.

[0029] According to another aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, the computer program being used to implement the above-described method for identifying capacitor faults based on capacitor self-healing characteristic gas.

[0030] According to another aspect of the invention, a computer program product is provided, comprising a computer program that, when executed by a processor, implements a method for identifying capacitor faults based on capacitor self-healing characteristic gas as described above.

[0031] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0032] 1. This invention establishes a relationship between the capacitance of a failed capacitor and the corresponding generated elemental carbon content based on changes in capacitor sheet resistance and carbon-hydrogen ratio. By judging the relationship between the theoretically generated elemental carbon content and a threshold under different sheet resistance and carbon-hydrogen ratio changes, the operating status of the capacitor is given without the capacitor exiting the system, and this is used as the failure criterion for the capacitor. This method has high identification accuracy and high efficiency.

[0033] 2. The minimum Gibbs free energy theory proposed in this invention can calculate the equilibrium composition of a thermodynamic equilibrium system under certain temperature and pressure conditions, and use this to calculate the content of elemental carbon generated theoretically. It can also quickly and accurately calculate the theoretical mass of solid carbon in a capacitor. Attached Figure Description

[0034] Figure 1 This is a flowchart of a method for identifying capacitor faults based on the self-healing characteristic gas of capacitors, constructed according to a preferred embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the thermodynamic curve constructed according to a preferred embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0037] like Figure 1 As shown, a method for identifying capacitor faults based on the self-healing characteristics of capacitors using gas is described. This method includes the following steps:

[0038] S1 conducted withstand voltage tests on capacitors with different sheet resistances and carbon-hydrogen ratios to obtain the actual mass of solid carbon when the capacitors with different sheet resistances and carbon-hydrogen ratios failed.

[0039] The steps for calculating the actual mass of solid carbon are as follows:

[0040] All gases released from the thin film in the capacitor were obtained using a withstand voltage test.

[0041] The total mass of carbon-containing gases and the total mass of hydrogen-containing gases in all gases were obtained by gas chromatography analysis.

[0042] The total mass of the thin film resulting from the decomposition of the hydrogen-containing gas is calculated using the total mass of the hydrogen-containing gas.

[0043] The actual mass of solid carbon is the difference between the total mass of the thin film and the total mass of the carbon-containing gas.

[0044] Except for the variable conditions, all other factors of the capacitor should be the same, and a withstand voltage test should be carried out according to the standard to obtain the failure capacitance of the capacitor under different variable conditions. Then, the actual mass of solid carbon corresponding to the failure capacitance is obtained and used as the threshold of elemental carbon content.

[0045] Capacitor withstand voltage testing should be conducted according to the test methods recommended by relevant national or IEC standards. The environmental conditions for capacitor withstand voltage testing should be similar to the operating or application conditions to avoid introducing other variables that could affect the capacitor's failure capacitance.

[0046] S2 calculates the theoretical mass of solid carbon produced by capacitors with different sheet resistances and carbon-to-hydrogen ratios at different temperatures; the method for obtaining this theoretical mass is as follows:

[0047] By utilizing the types and thermodynamic parameters of hydrocarbon free radicals in different capacitors at different temperatures, and with the goal of minimizing the Gibbs free energy, the content ratio of hydrocarbon free radicals and the sublimation temperature of carbon in the capacitors at different temperatures are calculated.

[0048] In one embodiment of the present invention, such as Figure 2 As shown, the sublimation temperature of carbon is obtained by plotting a thermodynamic curve of temperature and carbon-hydrogen free radical ratio using the ratio of hydrocarbon free radicals in a capacitor at different temperatures. The temperature corresponding to the maximum C2H2 content in the hydrocarbon free radicals in this thermodynamic curve is the sublimation temperature of carbon.

[0049] The mass of carbon in capacitors at different temperatures can be calculated using the ratio of hydrocarbon free radicals and the total mass of the capacitor. The theoretical mass of solid carbon is the mass of carbon in capacitors above the sublimation temperature minus the mass of carbon in capacitors below the sublimation temperature.

[0050] The minimum Gibbs free energy theory describes the state of free radicals at different temperatures and defines the equilibrium composition of a thermodynamic equilibrium system. Based on thermodynamic data, it describes the minimum total Gibbs free energy of each component under certain temperature and pressure conditions.

[0051] The total Gibbs free energy of the system can be expressed as

[0052]

[0053] In the formula, n i μ is the number of moles of component i. i Let be the chemical potential of component i.

[0054] Chemical potential μ of different components i It is related to the partial pressure and standard chemical potential of the components and can be expressed as follows:

[0055]

[0056] In the formula, μ i 0 Let R be the chemical potential of component i under standard conditions (P = 100 kPa, T = 298 K), and R be the ideal gas constant, which is 8.314 J·mol⁻¹. -1 ·K-1 T is the temperature of the system, a i Let a be the activity of component i. Assuming that the calculated equilibrium components are all ideal gases, then a i P is the partial pressure of component i. i .

[0057] S3 compares the theoretical mass of solid carbon in capacitors with different sheet resistances and carbon-to-hydrogen ratios with their actual mass. Capacitors with a theoretical mass greater than their actual mass fail; otherwise, they do not fail.

[0058] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for identifying capacitor faults based on the self-healing characteristics of capacitor gases, characterized in that, The method includes the following steps: S1 conducts withstand voltage tests on capacitors with different sheet resistances and carbon-hydrogen ratios to obtain the actual mass of solid carbon when capacitors with different sheet resistances and carbon-hydrogen ratios fail. S2 calculates the theoretical mass of solid carbon produced by capacitors with different sheet resistances and carbon-to-hydrogen ratios at different temperatures; the method for obtaining this theoretical mass is as follows: By utilizing the types and thermodynamic parameters of hydrocarbon free radicals in different capacitors at different temperatures, and with the goal of minimizing the Gibbs free energy, the content ratio of hydrocarbon free radicals and the sublimation temperature of carbon in the capacitors at different temperatures are calculated. The mass of carbon in the capacitor at different temperatures is calculated using the carbon-hydrogen free radical content ratio and the total mass of the capacitor; the theoretical mass of solid carbon is obtained by subtracting the mass of carbon in the capacitor below the sublimation temperature from the mass of carbon in the capacitor above the sublimation temperature. S3 compares the theoretical mass of solid carbon in capacitors with different sheet resistances and carbon-hydrogen ratios with their actual mass. Capacitors with a theoretical mass greater than their actual mass fail; otherwise, they do not fail. In step S2, the formula for calculating the Gibbs free energy is as follows: in, n i The number of moles of component i μ i Let N be the chemical potential of component i, and N be the total number of components. The formula for calculating the chemical potential is as follows: in, μ i 0 Let i be the chemical potential of component i under standard conditions. R Let be the ideal gas constant. T For the system temperature, a i Let i be the activity of component i.

2. The method for identifying capacitor faults based on the self-healing characteristic gas of capacitors as described in claim 1, characterized in that, In step S1, the calculation steps for the actual mass of the solid carbon are as follows: All gases released from the thin film in the capacitor were obtained using a withstand voltage test. Obtain the total mass of carbon-containing gases and the total mass of hydrogen-containing gases in all gases; The total mass of the thin film resulting from the decomposition of the hydrogen-containing gas is calculated using the total mass of the hydrogen-containing gas. The total mass of the thin film minus the total mass of the carbon-containing gas is the actual mass of the solid carbon.

3. The method for identifying capacitor faults based on the self-healing characteristic gas of capacitors as described in claim 2, characterized in that, The total mass of carbon-containing gases and the total mass of hydrogen-containing gases in all gases were obtained by gas chromatography analysis.

4. A method for identifying capacitor faults based on the self-healing characteristic gas of a capacitor as described in claim 1 or 2, characterized in that, In step S2, the sublimation temperature of carbon is obtained by plotting a thermodynamic curve of temperature and carbon-hydrogen free radical ratio using the ratio of hydrocarbon free radical content in the capacitor at different temperatures. The temperature corresponding to the maximum C2H2 content in the hydrocarbon free radicals in the thermodynamic curve is the sublimation temperature of carbon.

5. A system for fault identification using the method for identifying capacitor faults based on the self-healing characteristic gas of capacitors as described in any one of claims 1-4, characterized in that, The system includes a solid carbon actual mass calculation module, a solid carbon theoretical mass calculation module, and a fault prediction module, wherein: The solid carbon actual mass calculation module is used to calculate the actual mass of solid carbon when capacitors with different sheet resistances and carbon-hydrogen ratios fail. The solid carbon theoretical mass calculation module is used to calculate the theoretical mass of solid carbon in capacitors with different sheet resistances and carbon-hydrogen ratios. The fault prediction module is used to predict whether the capacitor will fail by utilizing the actual and theoretical mass of the solid carbon.

6. A system for identifying capacitor faults based on the self-healing characteristics of capacitors using gas, characterized in that, The system includes an actuator for performing a method for identifying capacitor faults based on the self-healing characteristic gas of a capacitor, as described in any one of claims 1-4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, The computer program is used to implement the method for identifying capacitor faults based on the self-healing characteristic gas of capacitors as described in any one of claims 1-4.

8. A computer program product, characterized in that, The method includes a computer program that, when executed by a processor, implements a method for identifying capacitor faults based on the self-healing characteristic gas of a capacitor as described in any one of claims 1-4.

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