A method and system for assessing the degree of transformer faults based on the gas content generated during arc faults.

Abstract

This invention relates to the field of power equipment testing and fault diagnosis technology, and discloses a method and system for assessing the degree of transformer fault based on the gas content generated by electric arc faults. This invention divides the electric arc channel into an edge temperature zone and a core temperature zone. It uses the enthalpy change relationship between arc energy and oil pyrolysis reaction to calculate the equivalent pyrolysis temperature T of hydrocarbons in the oil at the edge of the arc, thereby obtaining the edge equilibrium constant of the pyrolysis reaction in the edge zone. Combined with the core equilibrium constant of the core temperature zone, the fault gas content in the edge and core temperature zones at the time of the fault is accurately obtained, thus achieving a precise assessment of the degree of transformer fault.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power equipment detection and fault diagnosis, and particularly relates to a transformer fault degree evaluation method and system based on arc fault gas production content. BACKGROUND

[0002] With the expansion of the power grid scale and the growth of power demand, the application of large-capacity and high-voltage transformers is increasingly popular. However, the complexity of the device operating environment leads to a significant increase in the failure rate, which poses new challenges to traditional fault diagnosis methods. Although the dissolved gas analysis technology in oil has been widely used in transformer fault diagnosis, the diagnosis accuracy and prediction ability under complex working conditions still need to be improved.

[0003] In recent years, the rapid development of multi-physical field simulation technology and computer science has provided a new way to solve this problem. Especially in the context of digital design and intelligent operation and maintenance of power equipment, the demand for quantitative analysis of fault evolution process is increasingly urgent. Transformer internal faults usually go through two key stages of high-energy arc discharge and insulating oil cracking gas, and the volume of gas produced by the arc directly determines the strength of the pressure wave in the oil tank.

[0004] At present, due to the complexity of the internal structure of the transformer, when the arc fault occurs, the gas production process is affected by the interaction of multiple factors, and the existing detection technology has limitations. The amount of gas produced is difficult to accurately obtain when the fault occurs, and thus the transformer fault degree cannot be accurately evaluated. SUMMARY

[0005] The present application provides a transformer fault degree evaluation method and system based on arc fault gas production content, which solves the technical problem of how to improve the accuracy of transformer fault degree evaluation.

[0006] The first aspect of the present application provides a transformer fault degree evaluation method based on arc fault gas production content, comprising:

[0007] An arc channel model of a target transformer under arc fault is constructed, and arc partition is performed to determine an edge temperature zone and a core temperature zone;

[0008] Based on the alkane molecule thermal decomposition reaction set of the target transformer, a thermal decomposition gas content model of the target transformer is constructed;

[0009] Obtain the electrical parameter data and oil thermal characteristic data of the edge temperature zone, and the core equilibrium constant of the core temperature zone;

[0010] Based on the electrical parameter data and the oil thermal characteristic data, the edge equilibrium constant of the edge temperature zone is determined;

[0011] Input the core balance constant and the edge balance constant into the thermal decomposition gas content model for solving, and obtain gas content data associated with the edge temperature zone and the core temperature zone, respectively;

[0012] Based on the preset gas type condition, the gas content data associated with the edge temperature zone and the core temperature zone are used to determine the fault level of the target transformer.

[0013] Optionally, based on the set of thermal decomposition reactions of alkane molecules of the target transformer, the thermal decomposition gas content model of the target transformer is constructed, which includes:

[0014] According to the thermal decomposition theory of alkane, a set of thermal decomposition reactions of alkane molecules is established to build a thermal decomposition gas content model;

[0015] A competition factor for characterizing the reaction path is introduced to the set of thermal decomposition reactions of alkane molecules to build a mole fraction reaction model;

[0016] According to the gas partial pressure definition formula, the set of thermal decomposition reactions of alkane molecules is fitted to build an equilibrium constant expression model;

[0017] The equilibrium influence expression model with temperature change is constructed by applying the law of thermodynamics;

[0018] By coupling the mole fraction reaction model, the equilibrium constant expression model and the equilibrium influence expression model, the thermal decomposition gas content model is built.

[0019] Optionally, the electrical parameter data includes arc current, arc voltage drop, arc length and arc duration, and based on the electrical parameter data and the oil thermal characteristic data, the edge balance constant of the edge temperature zone is determined, which includes:

[0020] The arc energy is determined by using the arc current, the arc duration and the arc voltage drop;

[0021] The total reaction enthalpy change of thermal decomposition is determined by using the arc current, arc duration, arc energy, arc length and oil thermal characteristic data;

[0022] According to the total reaction enthalpy change of thermal decomposition, the reaction coefficient in the thermal decomposition reaction process is determined;

[0023] Based on the reaction coefficient and the preset thermal reaction enthalpy change function, a thermal decomposition equivalent temperature equation set is constructed;

[0024] The thermal decomposition equivalent temperature equation set is solved by using a numerical method to obtain an equivalent temperature;

[0025] The equivalent temperature is used as an input to the equilibrium influence expression model with temperature variation influence to obtain an edge equilibrium constant of the edge temperature zone.

[0026] Optionally, the oil thermal property data includes specific heat capacity of insulating oil, oil hydrocarbon operating temperature, oil hydrocarbon vaporization temperature, latent heat of hydrocarbon oil vapor phase, specific heat ratio of insulating oil vapor, specific internal energy ratio of insulating oil vapor, and atmospheric pressure, and the total reaction enthalpy change of thermal decomposition is determined by using the arc current, arc duration, the arc energy, the arc length, and the oil thermal property data, including:

[0027] A first constant coefficient is determined by using the arc length.

[0028] A second constant coefficient is determined by using a preset conversion coefficient, the specific heat ratio of insulating oil vapor, and the specific internal energy ratio of insulating oil vapor.

[0029] A third constant coefficient is determined by using the arc current and the arc duration.

[0030] Oil hydrocarbon liquid-gas enthalpy increase is determined by using the first constant coefficient, the second constant coefficient, the third constant coefficient, the atmospheric pressure, and the arc energy.

[0031] Oil hydrocarbon liquid enthalpy increase is determined by using the specific heat capacity of insulating oil, the oil hydrocarbon operating temperature, and the oil hydrocarbon vaporization temperature.

[0032] The total reaction enthalpy change of thermal decomposition is determined by using the latent heat of hydrocarbon oil vapor phase, the oil hydrocarbon liquid enthalpy increase, and the oil hydrocarbon liquid-gas enthalpy increase.

[0033] Optionally, the fault level of the target transformer is determined by using the gas content data of the edge temperature zone and the core temperature zone based on a preset gas type condition, including:

[0034] It is determined whether the gas type of the edge characteristic gas in the edge temperature zone meets a preset gas type condition.

[0035] If the gas type of the edge characteristic gas meets the preset gas type condition, fault judgment is performed based on a three-ratio method by using the gas content data of each edge characteristic gas to generate a first fault judgment result.

[0036] If the gas type of the edge characteristic gas does not meet the preset gas type condition, fault judgment is performed based on an interval judgment method by using the gas content data of each edge characteristic gas to generate a first fault judgment result.

[0037] It is determined whether the gas type of the core characteristic gas in the core temperature zone meets the preset gas type condition.

[0038] If the gas type of the core characteristic gas meets the set gas type condition, a fault is determined based on a three-ratio method using the gas content data of each core characteristic gas to generate a second fault determination result;

[0039] If the gas type of the core characteristic gas does not meet the set gas type condition, a fault is determined based on an interval judgment method using the gas content data of each core characteristic gas to generate a second fault determination result;

[0040] The first fault value associated with the first determination result and the second fault value associated with the second determination result are input into a preset target fault value function to output a target fault value;

[0041] The target fault value is used to retrieve a preset fault level key-value data table to determine the fault level of the target transformer.

[0042] Optionally, the three-ratio method is used to determine a fault based on the gas content data of each edge characteristic gas to generate a first fault determination result, including:

[0043] The gas content data of any two different edge characteristic gases is selected for ratio operation to generate a first edge determination value, a second edge determination value, and a third edge determination value;

[0044] When the first edge determination value is less than a preset first edge fault threshold, the second edge determination value is less than a preset second edge fault threshold, and the third edge determination value is less than the preset first edge fault threshold, it is determined as a mild fault level and serves as a first fault determination result;

[0045] When the first edge determination value is less than a preset third edge fault threshold, and the third edge determination value is less than the preset third edge fault threshold, it is determined as a moderate fault level and serves as a first fault determination result;

[0046] When the first edge determination value is greater than or equal to the preset third edge fault threshold, or the second edge determination value is greater than or equal to the preset first edge fault threshold and the third edge determination value is greater than or equal to the preset third edge fault threshold, it is determined as a severe fault level and serves as a first fault determination result.

[0047] Optionally, the interval judgment method is used to determine a fault based on the gas content data of each edge characteristic gas to generate a first fault determination result, including:

[0048] The fault interval in which the gas content data of each edge characteristic gas is respectively determined to generate a plurality of edge fault level determination results;

[0049] The edge fault level determination result is any one of a severe fault level, a moderate fault level and a light fault level.

[0050] The fault levels are in descending order of a severe fault level, a moderate fault level and a light fault level.

[0051] The highest fault level is selected from the plurality of edge fault level determination results as a first fault determination result.

[0052] Optionally, the three-ratio method is used to determine the fault based on the gas content data of each core characteristic gas to generate a second fault determination result, including:

[0053] The gas content data of any two different core characteristic gases are selected to generate a first core determination value, a second core determination value and a third core determination value.

[0054] When the first core determination value is less than a preset first core fault threshold, the second core determination value is less than a preset second core fault threshold, and the third core determination value is less than the preset first core fault threshold, it is determined as a light fault level and serves as a second fault determination result.

[0055] When the first core determination value is less than a preset third core fault threshold, and the third core determination value is less than the preset third core fault threshold, it is determined as a moderate fault level and serves as a second fault determination result.

[0056] When the first core determination value is greater than or equal to the preset third core fault threshold, or the second core determination value is greater than or equal to the preset first core fault threshold and the third core determination value is greater than or equal to the preset third core fault threshold, it is determined as a severe fault level and serves as a second fault determination result.

[0057] Optionally, the interval determination method is used to determine the fault based on the gas content data of each core characteristic gas to generate a second fault determination result, including:

[0058] The fault intervals of the gas content data of each core characteristic gas are determined respectively to generate a plurality of core fault level determination results.

[0059] The core fault level determination result is any one of a severe fault level, a moderate fault level and a light fault level.

[0060] The fault levels are in descending order of a severe fault level, a moderate fault level and a light fault level.

[0061] Select the highest fault level from the plurality of core fault level determination results as a second fault determination result.

[0062] The second aspect of the present application provides a transformer fault degree evaluation system based on arc fault gas content, comprising:

[0063] An arc partition module is configured to construct an arc channel model of the target transformer under arc fault and perform arc partition to determine an edge temperature zone and a core temperature zone.

[0064] A model construction module is configured to construct a thermal decomposition gas content model of the target transformer based on a set of thermal decomposition reactions of alkane molecules of the target transformer.

[0065] A data acquisition module is configured to acquire electrical parameter data and oil thermal characteristic data of the edge temperature zone and core equilibrium constant of the core temperature zone.

[0066] A data processing module is configured to determine an edge equilibrium constant of the edge temperature zone based on the electrical parameter data and the oil thermal characteristic data.

[0067] A model solving module is configured to input the core equilibrium constant and the edge equilibrium constant into the thermal decomposition gas content model to solve the model, and obtain gas content data associated with the edge temperature zone and the core temperature zone, respectively.

[0068] A fault level determination module is configured to determine a fault level of the target transformer based on the gas content data associated with the edge temperature zone and the core temperature zone under a preset gas type condition.

[0069] As can be seen from the above technical solutions, the present application has the following advantages:

[0070] By dividing the arc channel into an edge temperature zone and a core temperature zone, the present application solves the equivalent pyrolysis temperature T of thermal decomposition reactions of hydrocarbons in the oil in the edge temperature zone according to the relationship between arc energy and reaction enthalpy change of oil pyrolysis reactions, and further acquires the edge equilibrium constant of the edge temperature zone, and in combination with the core equilibrium constant of the core temperature zone, accurately acquires the fault gas content of the edge temperature zone and the core temperature zone when a fault occurs, and further realizes accurate evaluation of the fault degree of the transformer. BRIEF DESCRIPTION OF DRAWINGS

[0071] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0072] Figure 1 A step flow chart of a transformer fault degree evaluation method based on arc fault gas content provided for embodiment one of the present application is provided.

[0073] Figure 2 An algorithm flow diagram of oil thermal decomposition gas content under arc fault is provided.

[0074] Figure 3 A structural block diagram of a transformer fault degree evaluation system based on arc fault gas content provided for embodiment three of the present application is provided. DETAILED DESCRIPTION

[0075] The embodiment of the present application provides a transformer fault degree evaluation method and system based on arc fault gas content, and is used for solving the technical problem of how to improve the accuracy of transformer fault degree evaluation.

[0076] In order to make the application purpose, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the following described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0077] Because the gas production amount is difficult to accurately obtain when the fault occurs, the in-depth development of related research is restricted. At present, the research on insulating oil cracking gas is mainly carried out through two methods of experiment and theoretical analysis. However, because there is a complex coupling relationship between the gas production amount and the arc characteristic parameters (such as current, channel volume, duration, etc.), it is difficult to comprehensively reveal the characteristic law by relying only on experimental means. Therefore, from the calculation point of view, combining the quantitative relationship between energy and gas production amount based on the fault mechanism becomes an important research direction. This not only helps to clarify the corresponding relationship between latent fault and dissolved gas content, but also provides theoretical support for analyzing sudden high-energy discharge accidents and predicting the risk of transformer explosion. To realize the accurate description of the insulating oil gas production characteristics under high energy density conditions, the key lies in solving two core problems: one is to clarify the physical and chemical mechanism of insulating oil thermal cracking, including reaction path, equilibrium characteristics and the influence of temperature; the other is to study the decomposition reaction characteristics under the action of arc, focusing on analyzing the influence law of arc parameters on reaction equilibrium. These researches will lay an important foundation for the improvement of transformer fault diagnosis and prediction technology. The present application carries out regional research according to the characteristics of arc in different regions, converts the complex arc gas production problem into a solvable mathematical model, so as to obtain the gas content under arc fault.

[0078] Please refer to Figures 1-2 , Figure 1The flowchart illustrates the steps of a transformer fault severity assessment method based on arc fault gas content, as provided in Embodiment 1 of the present invention.

[0079] Figure 2 This is a schematic diagram of the algorithm for calculating the gas content of oil thermal decomposition under arc fault conditions.

[0080] This invention provides a method for assessing the degree of transformer fault based on the gas content generated during arc faults, comprising:

[0081] Step 101: Construct an arc channel model of the target transformer under arc fault conditions, and perform arc partitioning to determine the edge temperature zone and core temperature zone.

[0082] In this embodiment of the invention, the structural parameters of the target transformer are obtained, including the number of turns, wire diameter, and core dimensions. A finite element analysis software is used to construct an arc channel model of the target transformer under arc fault conditions. During the fault process, the arc channel exhibits a layered temperature distribution: the central plasma temperature exceeds 5000K, forming the main conductive channel, while the surrounding area has a lower temperature (300-2000K) and may exhibit secondary branch structures. This temperature distribution characteristic is influenced by various factors, including liquid molecular structure, impurity type, field strength perturbation, space charge, and mobility, resulting in a dynamic non-uniform discharge process. Based on this, the arc channel model can be simplified into two temperature region models: the edge temperature region (T<1500K): the secondary branch streamer region located around the main arc column; and the core temperature region (T>1500K): the central main arc column region.

[0083] Step 102: Based on the set of alkane molecule thermal decomposition reactions of the target transformer, construct a thermal decomposition gas content model of the target transformer.

[0084] Furthermore, step 102 may include the following sub-steps:

[0085] S11. Based on the theory of alkane thermal decomposition, establish a set of alkane molecule thermal decomposition reactions with a thermal decomposition gas content model.

[0086] The theory of alkane thermal decomposition refers to the theoretical system governing the principles, mechanisms, and related laws of alkanes undergoing decomposition reactions under thermal conditions. In chemical equilibrium analysis, the equilibrium constant K reflects the direction and extent of the reaction. When K > 10⁵, the reaction can be considered complete. For ease of calculation, this invention employs the equilibrium state method to solve for the equilibrium constant and the thermal decomposition equation. For any reaction:

[0087] (1)

[0088] In the formula, v1, v 11 v 12These are the stoichiometric coefficients of reactant D, product E, and product F, respectively. The ratio of the stoichiometric coefficients represents the ratio of the moles of the substances undergoing the reaction.

[0089] In this embodiment of the invention, based on the principle, mechanism, and related laws of the decomposition reaction of alkanes under thermal action, the thermal decomposition process of transformer oil alkane molecule D is set as n thermal decomposition reactions, and the thermal decomposition reaction formula is denoted as:

[0090]

[0091] S12. A competing factor for characterizing the reaction pathway is introduced into the set of thermal decomposition reactions of alkane molecules to construct a mole fraction reaction model.

[0092] Furthermore, the mole fraction reaction model includes a reactant mole fraction reaction model, a product mole fraction reaction model, and a total mole number reaction model. The reactant mole fraction reaction model characterizes the mole fraction of each reactant during the thermal decomposition reaction; the product mole fraction reaction model characterizes the mole fraction of each product during the thermal decomposition reaction; and the total mole number reaction model characterizes the total number of moles of reactants and products. In this embodiment of the invention, alkane molecule D is defined as 1 part by weight, the number of decomposition moles is x parts, and the reaction progress is based on ξ=|x / v1|. By sequentially introducing competition factors αi~αn for n thermal decomposition reactions, the number of moles of reactants and products in each thermal decomposition reaction is quantified. The mole fraction reaction model includes a reactant mole fraction reaction model and a product mole fraction reaction model, as shown in Equation I, and a total mole number reaction model, as shown in Equation II. The mole fraction of each reactant and each product during the thermal decomposition reaction is calculated by Equation I.

[0093] Formula I

[0094] The summation of r(B) in Equation I represents the sum of the products of the competition factor αi of a certain reaction, the stoichiometric coefficient of the substance, and the reaction extent ξ in all pyrolysis reactions containing a certain product.

[0095] It should be noted that the summation of r(B) in Equation I represents the competition factor α of the reaction among all chemical reactions involving substance B. i The sum of the products of the stoichiometric coefficients of substance B (reactant vi, product vij) and the reaction progress ξ ensures the accuracy of the reaction path sequence and prevents skipping of reaction orders.

[0096] The total number of moles of reactants and products is denoted by N and is calculated using Equation II;

[0097] Formula II

[0098] In the formula, j refers to the product.

[0099] S13. Fit the set of thermal decomposition reactions of alkane molecules according to the definition of gas partial pressure, and construct an equilibrium constant expression model.

[0100] The definition of gas partial pressure refers to K, which is expressed as the partial pressure of the gas phase. p K expressed as a mole percentage x Definition of the relationship between them.

[0101] Specifically:

[0102] (2)

[0103] It should be noted that this relationship can serve as the basis for establishing a set of equations for the thermal decomposition of alkane molecules, used to describe the relationship between the equilibrium constant and the change in the mole fraction of the substance.

[0104] In this embodiment of the invention, based on Equations I and II, the equilibrium constant expression models for each reaction under standard atmospheric pressure are obtained:

[0105] Formula III

[0106] In Equation III, K p Θ p is the standard equilibrium constant under standard atmospheric pressure. Θ ρ is the standard atmospheric pressure, 101.325 kPa; p is the total pressure of the system, kPa; x1 and x2 are the mole percentages of the products of each pyrolysis reaction, in %; x3 is the mole percentage of the reactants of each pyrolysis reaction, in %; v1 and v2 are the stoichiometric coefficients of the products of each pyrolysis reaction; v3 is the stoichiometric coefficient of the reactants of each pyrolysis reaction; vB is the sum of the stoichiometric coefficients of a certain substance in the pyrolysis reaction.

[0107] S14. Construct an equilibrium influence expression model that incorporates the effects of temperature changes using the laws of thermodynamics.

[0108] Furthermore, S14 may include the following sub-steps:

[0109] S141. Based on the Vantoff law formula, construct an expression model for the effect of temperature on the chemical equilibrium constant.

[0110] In this embodiment of the invention, the effect of temperature on the equilibrium constant can be expressed by the Van't Hoff formula, and the model for expressing the effect of temperature on the chemical equilibrium constant is as follows:

[0111] (3)

[0112] In the formula, R is the molar gas constant, 8.314 J·K. -1 ·mol -1 ;

[0113] T is the thermodynamic temperature, Kelvins;

[0114] Δ r H m Θ It is the enthalpy change of the reaction when all substances are in their standard state and the chemical reaction progress is 1 mol, expressed in kJ / mol.

[0115] Formula (3) shows that K Θ The change with temperature depends on Δ r H m Θ The symbol Δ. For the endothermic reaction of alkane thermal decomposition, Δ r H m Θ >0, K Θ It increases with increasing temperature, promoting the reaction to proceed in the forward direction.

[0116] S142. Based on Kirchhoff's laws, construct a model to express the relationship between reaction enthalpy change and molar isobaric heat capacity.

[0117] In this embodiment of the invention, the enthalpy change Δ of the reaction can be obtained according to the integral formula of Kirchhoff's law. r Hm Θ With molar isobaric heat capacity C p，m Relational expression model:

[0118] (4)

[0119] In the formula, ΔH0 is a constant; ΔCp is:

[0120] (5)

[0121] It should be noted that in this invention, the stoichiometric coefficients representing products are positive, while the stoichiometric coefficients representing reactants are negative.

[0122] S143. By coupling the expression model of the effect of temperature on chemical equilibrium constant, the expression model of the relationship between reaction enthalpy change and molar isobaric heat capacity, and the expression model of the relationship between pre-set heat melting and temperature, an equilibrium effect expression model containing the influence of temperature change is constructed.

[0123] From formulas (3)-(5), it can be seen that the effect of temperature on chemical equilibrium originates from the effect of temperature on the heat capacity of each substance participating in the reaction. Considering Cp,m in the range of 298K~1500K as a function of temperature T, it satisfies the empirical formula shown in formula (6):

[0124] (6)

[0125] Substituting formulas (4)-(6) into (3) and integrating, we obtain the formula for the effect of temperature on chemical equilibrium:

[0126] (7)

[0127] By considering the temperature change characteristics of heat capacity and establishing equation (7) based on the thermodynamic isotherm, the temperature corresponding to T can be obtained more accurately. .

[0128] In this embodiment of the invention, the following models are used: a model expressing the effect of temperature on the chemical equilibrium constant, a model expressing the relationship between reaction enthalpy change and molar isobaric heat capacity, and a pre-defined model expressing the relationship between thermal melting and temperature.

[0129] Formula IV

[0130] In Equation IV, T represents the transformer oil temperature, which is the thermodynamic temperature, Kelvins.

[0131] △H0 is the enthalpy change of the reaction when all substances are in standard state and the chemical reaction progress is 1 mol, in kJ / mol;

[0132] R is the molar gas constant, 8.314 J·K. -1 ·mol -1 ;

[0133] Δa, Δb, and Δc are the sum of the products of the stoichiometric coefficients of each substance involved in each individual pyrolysis reaction and the coefficients of the constant, linear, and quadratic terms in the specific heat capacity.

[0134] I is a constant.

[0135] It should be noted that since the empirical function in Equation IV is fitted by different experiments, it may contain higher-order terms related to temperature. The coefficients of these higher-order terms are omitted, and the ellipsis can be removed here, resulting in:

[0136] Formula IV

[0137] For ease of understanding, the following is the derivation process of Equation IV:

[0138] Taking thermal decomposition reaction (1) as an example, thermal decomposition reaction (1):

[0139] (1)

[0140] In the thermal decomposition reaction formula (1), v1, v11, and v12 are the stoichiometric coefficients of reactant D, product E, and product F, respectively (the ratio of the stoichiometric coefficients represents the ratio of the number of moles of the substances undergoing the reaction).

[0141] The relationship between Kp, expressed as gas phase partial pressure, and Kx, expressed as mole percentage, can be derived from the definition of gas phase partial pressure, as shown in equation (2):

[0142] (2)

[0143] In equation (2), Kp Θ This is the standard equilibrium constant under standard atmospheric pressure (101.325 kPa);

[0144] p Θ Standard atmospheric pressure;

[0145] p is the total pressure of the system, in kPa; x D x E x F The mole percentages of reactant D, product E, and product F are respectively, and v B The value is determined by the stoichiometric coefficient of the substance.

[0146] The effect of temperature on the chemical equilibrium constant can be seen using Van't Hoff's formula:

[0147] (3)

[0148] According to the integral of Kirch-Hoff's law, the enthalpy change of the reaction Δ can be obtained. r Hm Θ With molar isobaric heat capacity C p，m Relationship:

[0149] (4)

[0150] In the formula, ΔH0 is a constant; taking (1) as an example, ΔCp is:

[0151] (5)

[0152] It should be noted that in this invention, the stoichiometric coefficients representing products are positive, while the stoichiometric coefficients representing reactants are negative.

[0153] The preset expression for the relationship between heat melt and temperature is:

[0154] (6)

[0155] In equation (6), the preferred value range for T is 298K~1500K.

[0156] Substituting equations (4)-(6) into (3) and integrating, we obtain the effect of temperature on chemical equilibrium, i.e., equation IV.

[0157] S15. By coupling the mole fraction reaction model, the equilibrium constant expression model, and the equilibrium influence expression model, a thermal decomposition gas content model is constructed.

[0158] In this embodiment of the invention, the mole fraction reaction model, the equilibrium constant expression model, and the equilibrium influence expression model are coupled to construct a thermal decomposition gas content model. The equilibrium constant expression model III serves as the core expression of the thermal decomposition gas content model. The parameters in the equilibrium constant expression model III are solved using equations I, II, and IV to obtain the mole fraction of each component. In this invention, to describe the phenomenon of different reaction progresses among reactions, a competition factor αi∈[0,1) is established. The strength of the competition between reactions describes the amount of reaction products generated, thereby quantifying the different amounts of generation and consumption of the same characteristic gas by different thermal decomposition reactions at a given temperature. When αi (i=1,...,n) is close to 1, it indicates that the reaction has a high reaction progress and a strong ability to obtain the enthalpy change value among multiple simultaneous reactions, indicating strong competition; conversely, the reaction competition is weak.

[0159] Step 103: Obtain electrical parameter data and oil thermal characteristic data of the edge temperature zone, as well as the core equilibrium constant of the core temperature zone.

[0160] In this embodiment of the invention, electrical parameter data and oil thermal characteristic data of the edge temperature zone are obtained, as well as the core equilibrium constant of the core temperature zone.

[0161] Step 104: Based on electrical parameter data and oil thermal characteristic data, determine the edge equilibrium constant of the edge temperature zone.

[0162] It should be noted that in calculating the edge equilibrium constant in the edge temperature zone, within the arc edge temperature zone (T<1500K), the amount of gas generated is mainly determined by the heat converted from the arc energy. Different temperatures correspond to different heat capacities and reaction enthalpy changes. Calculating the gas production requires first determining the heat absorbed by the oil thermal decomposition and the reaction enthalpy change.

[0163] Arc fault energy calculation:

[0164] (13)

[0165] In the formula, W arc I is the arc energy, J; t is the arc duration, s; I arc U is the arc current, A; arc Let V be the voltage drop across the arc.

[0166] The conversion of electric arc energy into insulating oil can be represented as αW. arcThe conversion coefficient α is generally taken as 15%~40%. The relationship between the arc energy and the enthalpy change of the oil thermal decomposition reaction is shown below:

[0167] (14)

[0168] In the formula ΔH oil The enthalpy increase of hydrocarbons in oil from liquid to gaseous state, J / (g·K); m gas Let be the mass of insulating oil vapor, in grams. In subsequent calculations of this invention, α is set to 0.4. The enthalpy increase equation for this process is as follows:

[0169] (15)

[0170] (16)

[0171] In the formula, ΔH1 is the liquid enthalpy increase of hydrocarbons in the oil;

[0172] C oil This refers to the specific heat capacity of the insulating oil.

[0173] T1 is the normal operating temperature of hydrocarbons in oil, 60~80 ℃;

[0174] T2 is the vaporization temperature of hydrocarbons, 400 °C;

[0175] ΔH2 is the latent heat of vaporization phase change of hydrocarbons in oil. Since the molecular weight of carbon atoms in oil is usually between 15 and 23, taking C16H42 as an example, its latent heat of vaporization phase change is 226.15 J / g.

[0176] Δ r H represents the enthalpy increase of insulating oil vapor, which is the total enthalpy change of the hydrocarbons in the oil undergoing thermal decomposition reactions.

[0177] According to the law of conservation of mass, equation (14) can be written as:

[0178] (17)

[0179] In the formula ρ gas This refers to the density of insulating oil vapor, expressed in g / m³. 3 V gas This refers to the volume of insulating oil vapor, expressed in cubic meters (m³). 3 .

[0180] According to the ideal gas law, we can obtain:

[0181] (18)

[0182] In the formula, P gasρ is the internal pressure of the insulating oil vapor bubble, Pa; μ is the specific internal energy of the insulating oil vapor, 5.68 × 10⁻⁶. 6 J / kg; γ is the specific heat ratio of insulating oil vapor, 1.352.

[0183] An approximate relationship between the energy of an internal arc fault and the amount of gas produced in a transformer was obtained through experiments:

[0184] (19)

[0185] To obtain the relationship between the enthalpy change of the oil thermal decomposition reaction and the electric arc energy, P also needs to be given. gas With ΔH oil W arc The relationship between them.

[0186] (20)

[0187] In the formula, l arc Arc length, cm; P, absolute pressure, P=P gas +P0, atm.

[0188] Using the arc energy and arc current as known quantities, substituting equations (12), (19), (20), and (17) into equation (15), we can obtain the enthalpy increase ΔH of the insulating oil under arc discharge. oil The calculation formula is as follows:

[0189] (twenty one)

[0190] In the formula, k1, k2, and k3 are constant coefficients, and the expression is as follows:

[0191] (twenty two)

[0192] (twenty three)

[0193] (twenty four)

[0194] Furthermore, according to equation (15), the arc energy W can be derived. arc As input, the total enthalpy change Δ of the thermal decomposition reaction of hydrocarbons in insulating oil is... r H is the output of the solution formula. The enthalpy change of a chemical reaction depends on the type and quantity of the participating substances and their changes in molar heat capacity. Combining the functional relationship between heat capacity and temperature in equation (6), the enthalpy change of the reaction can be expressed as:

[0195] (25)

[0196] Let βi be the coefficient of enthalpy change obtained by the i-th reaction (i=1,...,n) in the thermal decomposition of a certain alkane molecule, relative to the total enthalpy change. Then βiΔ r H represents the enthalpy change of the reaction. Based on this, a system of equations consisting of the coefficient βi and the temperature T can be established:

[0197] (26)

[0198] Solving equation (26) yields the equivalent temperature T of the thermal decomposition reaction of hydrocarbons in the oil in the edge region of the electric arc. Substituting this into equation IV, the edge equilibrium constant is obtained. Then, the equilibrium constant is substituted into the alkane molecule thermal decomposition equation set and solved using the Levenberg–Marquardt iterative algorithm. The fault gas content of the thermal decomposition reaction in the edge temperature region can be calculated.

[0199] Furthermore, the electrical parameter data includes arc current, voltage drop across the arc, arc length, and arc duration. Step 104 may include the following sub-steps:

[0200] S21. Determine the arc energy using the arc current, arc duration, and voltage drop across the arc.

[0201] In this embodiment of the invention, the electric arc energy is obtained by formula (13).

[0202] (13)

[0203] In the formula, W arc I is the arc energy, J; t is the arc duration, s; I arc U is the arc current, A; arc Let V be the voltage drop across the arc.

[0204] S22. Using data on arc current, arc duration, arc energy, arc length, and oil thermal properties, determine the total enthalpy change of thermal decomposition reaction.

[0205] Furthermore, S22 may include the following sub-steps:

[0206] S221. Use the arc length to determine the first constant coefficient.

[0207] In this embodiment of the invention, the first constant coefficient is obtained by formula (22).

[0208] (twenty two)

[0209] In the formula, Indicates the first constant coefficient. Indicates the length of the electric arc.

[0210] S222. The second constant coefficient is determined by using the preset conversion coefficient, the specific heat ratio of insulating oil vapor and the specific internal energy of insulating oil vapor.

[0211] In this embodiment of the invention, the second constant coefficient is obtained by formula (23).

[0212] (twenty three)

[0213] In the formula, Indicates the second constant coefficient. This indicates the preset conversion factor. Indicates the specific heat ratio of insulating oil vapor. This indicates the vapor energy of insulating oil.

[0214] S223, arc current and arc duration, determine the third constant coefficient.

[0215] In this embodiment of the invention, the third constant coefficient is obtained using formula (24).

[0216] (twenty four)

[0217] In the formula, Indicates the third constant coefficient. Represents arc current. Indicates the duration of the electric arc.

[0218] S224. Using the first constant coefficient, the second constant coefficient, the third constant coefficient, atmospheric pressure, and electric arc energy, determine the enthalpy increase of oil hydrocarbon liquid gas.

[0219] In this embodiment of the invention, the enthalpy increase of oil hydrocarbon liquid gas is obtained by formula (21).

[0220] Furthermore, the specific expression for the enthalpy increase of oil hydrocarbon liquid gas is as follows:

[0221]

[0222] In the formula, This indicates an increase in the enthalpy of oil hydrocarbons in liquid and gaseous forms. Indicates the energy of the electric arc. Indicates atmospheric pressure. Indicates the first constant coefficient. Indicates the second constant coefficient. This represents the third constant coefficient.

[0223] S225. The specific heat capacity of insulating oil, the operating temperature of oil hydrocarbon, and the vaporization temperature of oil hydrocarbon are used to determine the liquid enthalpy increase of oil hydrocarbon.

[0224] In this embodiment of the invention, the liquid enthalpy increase of oil hydrocarbon is obtained by formula (16).

[0225] (16)

[0226] In the formula, This indicates an increase in the liquid enthalpy of oil hydrocarbons. This indicates the specific heat capacity of insulating oil. Indicates the operating temperature of oil hydrocarbons. This indicates the vaporization temperature of oil hydrocarbons.

[0227] S226. The enthalpy change of the total thermal decomposition reaction is determined by using the latent heat of hydrocarbon vapor phase, the enthalpy increase of hydrocarbon liquid phase, and the enthalpy increase of hydrocarbon liquid-gas phase.

[0228] Furthermore, S226 may include the following sub-steps:

[0229] S2261. The difference between the enthalpy increase of oil hydrocarbon liquid gas and the latent heat of hydrocarbon oil vapor phase is calculated to obtain the first difference value.

[0230] S2262. The total enthalpy change of thermal decomposition reaction is obtained by performing difference calculations using the first difference and the liquid enthalpy increase of oil hydrocarbon.

[0231] In this embodiment of the invention, the total enthalpy change of the thermal decomposition reaction is calculated using formula (15). The above process is encapsulated in formula form:

[0232]

[0233] In the formula, This represents the enthalpy change of the overall thermal decomposition reaction.

[0234] S23. Determine the reaction coefficients in the thermal decomposition process based on the enthalpy change of the overall thermal decomposition reaction.

[0235] In this embodiment of the invention, let βi be the reaction coefficient of the enthalpy change obtained by the i-th reaction (i=1,···,n) in the thermal decomposition of a certain alkane molecule, which accounts for the enthalpy change of the total thermal decomposition reaction.

[0236] S24. Based on the reaction coefficient and the preset thermal reaction enthalpy change function, construct a set of equivalent temperature equations for thermal decomposition.

[0237] In this embodiment of the invention, βiΔ r H represents the enthalpy change of the reaction. Based on this, a set of equations consisting of the reaction coefficient βi and the equivalent temperature T can be established according to formula (25):

[0238] (26)

[0239] S25. Solve the equivalent temperature equations for thermal decomposition using numerical methods to obtain the equivalent temperature.

[0240] In this embodiment of the invention, numerical methods, such as the Newton-Raphson iterative method, are used to solve the thermal decomposition equivalent temperature equations to obtain the equivalent temperature.

[0241] S26. The edge equilibrium constant of the edge temperature zone is obtained by solving the equivalent temperature input temperature effect expression model on the chemical equilibrium constant.

[0242] In this embodiment of the invention, the equivalent temperature input formula IV is used to solve for the edge equilibrium constant of the edge temperature zone.

[0243] It is worth mentioning that, in this invention, the temperature used to input the alkane molecule thermal decomposition equations when determining the edge equilibrium constant is the equivalent temperature obtained by the arc energy method, rather than directly obtained data.

[0244] Step 105: Use the core equilibrium constant and the edge equilibrium constant as inputs to the thermal decomposition gas content model for solution, and obtain the gas content data associated with the edge temperature zone and the core temperature zone respectively.

[0245] Furthermore, step 105 may include the following sub-steps:

[0246] S31. The gas content data of each edge characteristic gas in the edge temperature zone are obtained by solving the thermal decomposition gas content model using the core equilibrium constant input.

[0247] To facilitate understanding, the following is an application example:

[0248] For any alkane molecule D, assume its thermal decomposition process consists of n thermal decomposition reactions. The thermal decomposition process is as follows:

[0249]

[0250] Based on the above thermal decomposition process, taking the thermal decomposition reaction of propane as an example: For the alkane molecule C3H8, the C-C bond breaking reaction and the dehydrogenation reaction are selected as thermal decomposition reactions, and its thermal decomposition process can be composed of 5 thermal decomposition reactions (denoted as Equation (8)):

[0251] (8)

[0252] The total number of moles of reactants and products is denoted by N and is calculated using Equation II;

[0253] Formula II

[0254] Let the initial number of C3H8 moles be 1 mol, ξ=x, and convert it to the total number of moles of reactants and products according to Equation II (9):

[0255] N=1-x+2α1x+2α2x+α3x+α4x (9);

[0256] In the specific implementation, taking i=1 in equation (8) as an example, x mol of C3H8 is reacted to generate a1*x mol of CH4 and C2H4;

[0257] When reaction i=2, x mol of C3H8 is reacted and a2*x mol of C3H6 and H2 are generated;

[0258] When reaction i=3, the amount of C3H6 is a2*x mol. After a3*x mol reacts, a2*x - a3*x of C3H6 remains, and a3*x mol of CH4 and C2H2 are generated at the same time.

[0259] This process continues until the molar number of all products is obtained. They are all produced by x mol of C3H8, and there are 1-x mol of them remaining. Adding them all together gives the value of N.

[0260] Taking the reaction in equation (8) as an example, the mole fractions of each substance can be converted according to equation I as shown in equation (10):

[0261] Formula I

[0262] The mole fraction of a substance is shown in equation (10):

[0263] (10)

[0264]

[0265] The relationship between KpΘ, expressed as gas phase partial pressure, and Kx, expressed as mole percentage, is as follows:

[0266] Formula III

[0267] Formula IV

[0268] Based on equations I, II, III, and IV, by simultaneously applying the equilibrium constant expressions for all thermal decomposition reactions to the atomic conservation equations, we can obtain the following set of equations for the thermal decomposition of alkane molecules, taking temperature T as input and the mole fractions of various gases produced during the thermal decomposition process as output:

[0269] (11)

[0270] Taking the thermal decomposition reaction of propane as an example: the last reaction in equation (8) is not independent, so the reaction path consists of reactions 1-4, and the competition factors are α1-α4 respectively. In summary, according to equation (11), it can be converted into a thermal decomposition equation as follows: equation (12):

[0271] (12)

[0272] The solution process is as follows:

[0273] Regarding (12), based on the equilibrium constant expression model III for each reaction under standard atmospheric pressure and the equilibrium influence expression model IV including the effect of temperature change, the competition factor α for each thermal decomposition reaction under the equivalent temperature T is obtained by using the Levenberg–Marquardt iterative algorithm. i ~α n The mole fraction of each component in the pyrolysis reaction. Specifically, the competition factor can be calculated using equation (12) in this invention. The equilibrium constant expression model III for different chemical reactions is composed of equation (12). First, the equivalent temperature T is used as input and substituted into equation IV to calculate the equilibrium constant K. Then, the equilibrium constant K is substituted into equation (12) to obtain the competition factor and the reaction progress x. Finally, the mole fraction of each edge characteristic gas is obtained through equation (10), that is, equation I.

[0274] S32. The gas content data of each core characteristic gas in the core temperature zone are obtained by solving the thermal decomposition gas content model using the edge equilibrium constant input.

[0275] In this embodiment of the invention, since the core temperature zone of the electric arc channel can reach above 5000K, it is not suitable to use the arc energy method in step 104 to calculate the chemical equilibrium constant. When K p Θ >10 5 At this point, the reaction can be considered a "complete reaction." Within the core temperature zone, the instantaneous high temperature causes the insulating oil alkane molecules to rapidly reach a state of complete thermal decomposition. Therefore, the equilibrium constant K for the thermal decomposition reaction in this region can be assumed. p Θ =10 5 This aligns with the characteristics of complete thermal decomposition of molecules, while avoiding the technical challenges of measuring and calculating the equilibrium constant under transient high temperatures.

[0276] Solving for the gas content data of each core characteristic gas within the core temperature region is consistent with the application example in S31, since the core temperature region directly determines the core equilibrium constant K. p Θ =10 5 Therefore, the core equilibrium constant is directly substituted into the solution equation (12), that is, in equation (12) The competition factor and reaction progress x are obtained by solving the equation (10), that is, equation I. The mole fraction of each core characteristic gas is then obtained by equation (10), that is, equation I.

[0277] Step 106: Based on the preset gas type conditions, determine the fault level of the target transformer using the gas content data associated with the edge temperature zone and the core temperature zone.

[0278] Furthermore, step 106 may include the following sub-steps:

[0279] S41. Determine whether the gas type of the edge characteristic gas meets the preset gas type conditions. Based on the determination result, perform fault judgment on the gas content data of each edge characteristic gas in the edge temperature zone and determine the first judgment result.

[0280] The preset gas type conditions specifically include methane (CH4), ethylene (C2H4), ethane (C2H6), acetylene (C2H2), and hydrogen (H2).

[0281] Furthermore, S41 may include the following sub-steps:

[0282] S411. Determine whether the gas type of the edge feature gas meets the preset gas type conditions.

[0283] In this embodiment of the invention, it is determined whether the gas types of the edge characteristic gases generated in the edge temperature zone all include the five gases: methane (CH4), ethylene (C2H4), ethane (C2H6), acetylene (C2H2), and hydrogen (H2).

[0284] S412. If the gas type of the edge characteristic gas meets the gas type condition, then based on the three ratio method, the gas content data of each edge characteristic gas is used to determine the fault and generate the first fault determination result.

[0285] Furthermore, S412 may include the following sub-steps:

[0286] S4121. Randomly select two different edge feature gas content data and perform a ratio operation to generate a first edge judgment value, a second edge judgment value, and a third edge judgment value.

[0287] In this embodiment of the invention, when the gas type of the edge characteristic gas meets the gas type setting condition, a first edge judgment value (C2H2 / C2H4), a second edge judgment value (CH4 / H2), and a third edge judgment value (C2H4 / C2H6) are calculated. It should be noted that the preset first edge fault threshold is preferably 1, the preset second edge fault threshold is preferably 0.1, and the preset third edge fault threshold is preferably 3.

[0288] S4122. When the first edge judgment value is less than the preset first edge fault threshold, the second edge judgment value is less than the preset second edge fault threshold, and the third edge judgment value is less than the preset first edge fault threshold, it is judged as a minor fault level and is used as the first fault judgment result.

[0289] In this embodiment of the invention, when C2H2 / C2H4<1, CH4 / H2<0.1 and C2H4 / C2H6<1, it indicates a mild arc fault, with slight partial discharge or initial arcing inside the transformer. The impact on the overall operation of the transformer is relatively small. For example, it may be due to some tiny defects in the insulation material that have started to cause local ionization, but have not yet caused serious damage to the insulation structure.

[0290] S4123. When the first edge judgment value is less than the preset third edge fault threshold and the third edge judgment value is less than the preset third edge fault threshold, it is judged as a medium fault level and used as the first fault judgment result.

[0291] In this embodiment of the invention, when C2H2 / C2H4<3 and C2H4 / C2H6<3, it indicates a moderate arc fault. The arc fault has developed to a certain extent and may have caused some damage to the insulation structure of the transformer. For example, the insulating paper has begun to show local carbonization, which leads to an increase in the amount of gas generated. Further inspection and maintenance of the transformer are required, such as insulation resistance testing.

[0292] S4124. When the first edge judgment value is greater than or equal to the preset third edge fault threshold, or the second edge judgment value is greater than or equal to the preset first edge fault threshold and the third edge judgment value is greater than or equal to the preset third edge fault threshold, it is judged as a severe fault level and is used as the first fault judgment result.

[0293] In this embodiment of the invention, when C2H2 / C2H4⩾3, or CH4 / H2⩾1 and C2H4 / C2H6⩾3, it indicates a severe arc fault. There may be a serious arc discharge inside the transformer, and the insulation structure may have been severely damaged, such as a large area of ​​the insulation layer being broken down, which may lead to serious problems such as transformer short circuit and a sharp rise in oil temperature.

[0294] S413. If the gas type of the edge characteristic gas does not meet the gas type condition, then based on the interval judgment method, the gas content data of each edge characteristic gas is used to determine the fault and generate the first fault determination result.

[0295] Furthermore, S413 may include the following sub-steps:

[0296] S4131. Determine the fault range where the gas content data of each edge characteristic gas is located, and generate multiple edge fault level determination results.

[0297] Among them, the edge fault level determination result is any one of the severe fault level, moderate fault level, and mild fault level;

[0298] The fault levels, from highest to lowest, are severe fault level, moderate fault level, and minor fault level.

[0299] In this embodiment of the invention, when the gas type of the edge characteristic gas does not meet the set gas type condition, for example, the edge characteristic gas generated under an arc fault only includes methane (CH4) and hydrogen (H2), since the mole fraction of each edge characteristic gas obtained by solving the thermal decomposition equation set is the mole fraction, the following are specific examples: when the mole fraction of hydrogen (H2) is in the range of 50-150 μL / L (microliters per liter, converted to mole fraction), it is determined to be a mild fault level; when the mole fraction of hydrogen (H2) is in the range of 150-300 μL / L, it is determined to be a moderate fault level; when the mole fraction of hydrogen (H2) exceeds 300 μL / L, it is determined to be a severe fault level. When the molar fraction of methane (CH4) is in the range of 20-50 μL / L, it is judged as a mild fault level; when the molar fraction of methane (CH4) is in the range of 50-100 μL / L, it is judged as a moderate fault level; when the molar fraction of methane (CH4) exceeds 100 μL / L, it is judged as a severe fault level.

[0300] S4132. Select the highest fault level from multiple edge fault level determination results as the first fault determination result.

[0301] In an embodiment of the present invention, for example, when hydrogen (H2) is used for judgment, it is determined to be a minor fault level, and when methane (CH4) is used for judgment, it is determined to be a moderate fault level. Therefore, the final first fault judgment result is a moderate fault level.

[0302] S42. Determine whether the gas type of the core characteristic gas meets the preset gas type conditions. Based on the judgment result, determine the fault of the gas content data of each core characteristic gas in the core temperature zone and determine the second judgment result.

[0303] Furthermore, S42 may include the following sub-steps:

[0304] S421. Determine whether the gas type of the core characteristic gas meets the preset gas type conditions.

[0305] In this embodiment of the invention, it is determined whether the core characteristic gases generated in the core temperature zone all contain the five gases: methane (CH4), ethylene (C2H4), ethane (C2H6), acetylene (C2H2), and hydrogen (H2).

[0306] S422. If the gas type of the core characteristic gas meets the gas type condition, then based on the three ratio method, the gas content data of each core characteristic gas is used to determine the fault and generate a second fault determination result.

[0307] Furthermore, S422 may include the following sub-steps:

[0308] S4221. Randomly select the gas content data of two different core characteristic gases and perform a ratio operation to generate the first core judgment value, the second core judgment value, and the third core judgment value.

[0309] In this embodiment of the invention, when the gas type of the core characteristic gas meets the set gas type condition, a first core judgment value (C2H2 / C2H4), a second core judgment value (CH4 / H2), and a third core judgment value (C2H4 / C2H6) are calculated. It should be noted that the preset first core fault threshold is preferably 1, the preset second core fault threshold is preferably 0.1, and the preset third core fault threshold is preferably 3.

[0310] S4222. When the first core judgment value is less than the preset first core fault threshold, the second core judgment value is less than the preset second core fault threshold, and the third core judgment value is less than the preset first core fault threshold, it is judged as a minor fault level and used as the second fault judgment result.

[0311] In this embodiment of the invention, when C2H2 / C2H4<1, CH4 / H2<0.1, and C2H4 / C2H6<1, it indicates a mild arc fault, where there is slight partial discharge or initial arcing inside the transformer. The impact on the overall operation of the transformer is relatively small. For example, it may be due to some minor defects in the insulation material that have begun to trigger local ionization, but have not yet caused serious damage to the insulation structure.

[0312] S4223. When the first core judgment value is less than the preset third core fault threshold, and the third core judgment value is less than the preset third core fault threshold, it is judged as a medium fault level and used as the second fault judgment result.

[0313] In this embodiment of the invention, when C2H2 / C2H4<3 and C2H4 / C2H6<3, it indicates a moderate arc fault. The arc fault has developed to a certain extent and may have caused some damage to the insulation structure of the transformer. For example, the insulating paper has begun to show local carbonization, which leads to an increase in the amount of gas generated. Further inspection and maintenance of the transformer are required, such as insulation resistance testing.

[0314] S4224. When the first core judgment value is greater than or equal to the preset third core fault threshold, or the second core judgment value is greater than or equal to the preset first core fault threshold and the third core judgment value is greater than or equal to the preset third core fault threshold, it is judged as a severe fault level and is used as the second fault judgment result.

[0315] In this embodiment of the invention, when C2H2 / C2H4⩾3, or CH4 / H2⩾1 and C2H4 / C2H6⩾3, it indicates a severe arc fault. There may be a serious arc discharge inside the transformer, and the insulation structure may have been severely damaged, such as a large area of ​​the insulation layer being broken down, which may lead to serious problems such as transformer short circuit and a sharp rise in oil temperature.

[0316] S423. If the gas type of the core characteristic gas does not meet the gas type condition, then based on the interval judgment method, the gas content data of each core characteristic gas is used to determine the fault and generate a second fault determination result.

[0317] Furthermore, S423 may include the following sub-steps:

[0318] S4231. Determine the fault range in which the gas content data of each core characteristic gas is located, and generate multiple core fault level determination results. Among them, the core fault level determination result is any one of severe fault level, moderate fault level, and mild fault level; the fault level from high to low is severe fault level, moderate fault level, and mild fault level.

[0319] In this embodiment of the invention, when the gas type of the core characteristic gas does not meet the set gas type condition, for example, the core characteristic gas generated under an arc fault only includes methane (CH4) and hydrogen (H2), since the mole fraction of each core characteristic gas obtained by solving the thermal decomposition equations is the mole fraction, the following are specific examples: when the mole fraction of hydrogen (H2) is in the range of 50-150 μL / L (microliters per liter, converted to mole fraction), it is determined to be a mild fault level; when the mole fraction of hydrogen (H2) is in the range of 150-300 μL / L, it is determined to be a moderate fault level; when the mole fraction of hydrogen (H2) exceeds 300 μL / L, it is determined to be a severe fault level. When the molar fraction of methane (CH4) is in the range of 20-50 μL / L, it is judged as a mild fault level; when the molar fraction of methane (CH4) is in the range of 50-100 μL / L, it is judged as a moderate fault level; when the molar fraction of methane (CH4) exceeds 100 μL / L, it is judged as a severe fault level.

[0320] S4232. Select the highest fault level from multiple core fault level determination results as the second fault determination result.

[0321] In an embodiment of the present invention, for example, when hydrogen (H2) is used for judgment, it is determined to be a minor fault level; when methane (CH4) is used for judgment, it is determined to be a moderate fault level. Therefore, the final second fault judgment result is a moderate fault level.

[0322] S43. Using the first judgment result and the second judgment result, determine the fault level of the target transformer.

[0323] Furthermore, S43 may include the following sub-steps:

[0324] S431. Input the first fault value associated with the first judgment result and the second fault value associated with the second judgment result into the preset target fault value function, and output the target fault value.

[0325] In this embodiment of the invention, the fault value is determined based on the fault level included in the judgment result. In this invention, the fault value is defined as 3 for severe fault level, 2 for moderate fault level, and 1 for mild fault level.

[0326] The preset target fault value function is as follows:

[0327]

[0328] In the formula, Indicates the target fault value. Indicates the edge weight coefficient. Indicates the first fault value. Indicates the core weight coefficient. This indicates the second fault value.

[0329] It is worth noting that the core temperature zone of a transformer contains critical components such as the core and windings. The core is the core part of the transformer that enables electromagnetic conversion, while the windings are the critical path for current transmission. In these regions, even small temperature changes can indicate serious faults. Therefore, the core weighting coefficient is greater than the edge weighting coefficient. In this invention, the core weighting coefficient is preferably 0.6, and the edge weighting coefficient is preferably 0.4.

[0330] S432. Use the target fault value to retrieve the preset fault level key-value pair data table to determine the fault level of the target transformer.

[0331] The preset fault level key-value pair data table refers to a key-value pair data table established based on the relationship between the target fault value and the fault level. The target fault value serves as the key, and the fault level serves as the value.

[0332] The preset fault level key-value pair data table is shown in the table below:

[0333] Table 1 is a key-value pair table for preset fault levels.

[0334]

[0335] In this embodiment of the invention, the target fault value output by the preset target fault value function can more accurately assess the fault level of the target transformer.

[0336] This proposal presents a thermodynamic algorithm for oil thermal decomposition gas production under arc fault conditions. The invention divides the arc channel into two regions: a core region where the oil thermal decomposition reaction occurs violently, and an edge region where the equivalent pyrolysis temperature is below 1500 K. In the core region, the equilibrium constant of the oil thermal decomposition reaction is extremely large, representing a complete reaction on a macroscopic scale. For the edge region, the equilibrium constant of the oil thermal decomposition reaction depends on the magnitude of the arc energy.

[0337] The thermodynamic calculation method of oil pyrolysis is applied to calculate the gas production of oil decomposition in the core area. Based on this, according to the relationship between the electric arc energy and the reaction enthalpy change of the oil pyrolysis reaction, the equivalent pyrolysis temperature T of hydrocarbons in the oil in the edge area of ​​the electric arc is solved, and then the equilibrium constant and fault gas content of the thermal decomposition reaction in the edge area are calculated.

[0338] Please see Figure 3 , Figure 3 This is a structural block diagram of a transformer fault severity assessment system based on the gas content generated by an electric arc fault, provided in Embodiment 3 of the present invention.

[0339] This invention provides a transformer fault severity assessment system based on arc fault gas content, comprising: an arc partitioning module 301, used to construct an arc channel model of a target transformer under arc fault conditions and partition the arc to determine the edge temperature zone and the core temperature zone; a model construction module 302, used to construct a thermal decomposition gas content model of the target transformer based on the alkane molecule thermal decomposition reaction set of the target transformer; a data acquisition module 303, used to acquire electrical parameter data and oil thermal characteristic data of the edge temperature zone, and the core equilibrium constant of the core temperature zone; a data processing module 304, used to determine the edge equilibrium constant of the edge temperature zone based on the electrical parameter data and oil thermal characteristic data; a model solving module 305, used to solve the thermal decomposition gas content model using the core equilibrium constant and the edge equilibrium constant as inputs, and obtain the gas content data associated with the edge temperature zone and the core temperature zone respectively; and a fault level determination module 306, used to determine the fault level of the target transformer based on preset gas type conditions and the gas content data associated with the edge temperature zone and the core temperature zone. Furthermore, the model construction module 302 includes: an alkane molecule thermal decomposition reaction set submodule, used to establish an alkane molecule thermal decomposition reaction set with a thermal decomposition gas content model based on the alkane thermal decomposition theory; a mole fraction reaction model submodule, used to introduce competing factors to characterize the reaction pathways into the alkane molecule thermal decomposition reaction set and construct a mole fraction reaction model; an equilibrium constant expression model submodule, used to fit the alkane molecule thermal decomposition reaction set according to the definition of gas partial pressure and construct an equilibrium constant expression model; an equilibrium influence expression model submodule, used to construct an equilibrium influence expression model containing the influence of temperature changes using thermodynamic laws; and a thermal decomposition gas content model submodule, used to build a thermal decomposition gas content model by coupling the mole fraction reaction model, the equilibrium constant expression model, and the equilibrium influence expression model. Further, the mole fraction reaction model includes a reactant mole fraction reaction model, a product mole fraction reaction model, and a total mole number reaction model; the reactant mole fraction reaction model characterizes the mole fraction of each reactant during the thermal decomposition reaction; the product mole fraction reaction model characterizes the mole fraction of each product during the thermal decomposition reaction; and the total mole number reaction model characterizes the total number of moles of reactants and products. Furthermore, the equilibrium influence expression model submodule includes: a temperature-to-chemical equilibrium constant expression model unit, used to construct an expression model of the temperature-to-chemical equilibrium constant based on the van der Rohe law formula; a reaction enthalpy change and molar isobaric heat capacity relationship expression model unit, used to construct an expression model of the reaction enthalpy change and molar isobaric heat capacity relationship based on the Kirchhoff law formula; and a coupling unit, used to construct an equilibrium influence expression model containing the effect of temperature change by coupling the temperature-to-chemical equilibrium constant expression model, the reaction enthalpy change and molar isobaric heat capacity relationship expression model, and the preset heat melting and temperature relationship expression model.Furthermore, the electrical parameter data includes arc current, voltage drop across the arc, arc length, and arc duration. The data processing module 304 includes: an arc energy submodule, used to determine the arc energy using arc current, arc duration, and voltage drop across the arc; a total enthalpy change submodule for thermal decomposition, used to determine the total enthalpy change for thermal decomposition using arc current, arc duration, arc energy, arc length, and oil thermal properties data; a reaction coefficient submodule, used to determine the reaction coefficients in the thermal decomposition reaction process based on the total enthalpy change for thermal decomposition; a thermal decomposition equivalent temperature equation set submodule, used to construct a thermal decomposition equivalent temperature equation set based on the reaction coefficients and a preset thermal reaction enthalpy change function; an equivalent temperature submodule, used to solve the thermal decomposition equivalent temperature equation set using numerical methods to obtain the equivalent temperature; and an edge equilibrium constant submodule, used to solve the edge equilibrium constant of the edge temperature zone using an expression model of the influence of the equivalent temperature input temperature on the chemical equilibrium constant. Furthermore, the thermal property data of the oil includes the specific heat capacity of insulating oil, operating temperature of oil hydrocarbons, vaporization temperature of oil hydrocarbons, latent heat of hydrocarbon vapor phase, specific heat ratio of insulating oil vapor, specific internal energy of insulating oil vapor, and atmospheric pressure. The total enthalpy change submodule for thermal decomposition includes: a first constant coefficient unit, used to determine the first constant coefficient using the arc length; a second constant coefficient unit, used to determine the second constant coefficient using a preset conversion coefficient, specific heat ratio of insulating oil vapor, and specific internal energy of insulating oil vapor; and a third constant coefficient unit. The model solver module 305 includes: a first solver submodule, used to determine the third constant coefficient based on the arc current and arc duration; an oil-hydrocarbon liquid-gas enthalpy increase unit, used to determine the oil-hydrocarbon liquid-gas enthalpy increase using the first, second, and third constant coefficients, atmospheric pressure, and arc energy; an oil-hydrocarbon liquid enthalpy increase unit, used to determine the oil-hydrocarbon liquid enthalpy increase using the specific heat capacity of insulating oil, oil-hydrocarbon operating temperature, and oil-hydrocarbon vaporization temperature; and a calculation unit, used to determine the total enthalpy change of thermal decomposition reaction using the latent heat of hydrocarbon vapor phase, oil-hydrocarbon liquid enthalpy increase, and oil-hydrocarbon liquid-gas enthalpy increase. Further, the model solver module 305 includes: a first solver submodule, used to solve the thermal decomposition gas content model using the core equilibrium constant as input, to obtain the gas content data of each edge characteristic gas within the edge temperature zone; and a second solver submodule, used to solve the thermal decomposition gas content model using the edge equilibrium constant as input, to obtain the gas content data of each core characteristic gas within the core temperature zone. Furthermore, the fault level determination module 306 includes: a first judgment result submodule, used to determine whether the gas type of the edge characteristic gas meets the preset gas type conditions, and to perform fault determination on the gas content data of each edge characteristic gas in the edge temperature zone based on the judgment result, and determine the first judgment result; a second judgment result submodule, used to determine whether the gas type of the core characteristic gas meets the preset gas type conditions, and to perform fault determination on the gas content data of each core characteristic gas in the core temperature zone based on the judgment result, and determine the second judgment result; and a target transformer fault level determination submodule, used to determine the fault level of the target transformer using the first judgment result and the second judgment result.Furthermore, the first judgment result submodule includes: a first processing unit, used to determine whether the gas type of the edge characteristic gas meets the preset gas type conditions; a second processing unit, used to, if the gas type of the edge characteristic gas meets the preset gas type conditions, perform fault judgment based on the three-ratio method using the gas content data of each edge characteristic gas, and generate a first fault judgment result; and a third processing unit, used to, if the gas type of the edge characteristic gas does not meet the preset gas type conditions, perform fault judgment based on the interval judgment method using the gas content data of each edge characteristic gas, and generate a first fault judgment result. Further, the second processing unit includes: an edge determination value subunit, used to arbitrarily select gas content data of two different edge characteristic gases and perform a ratio operation to generate a first edge determination value, a second edge determination value, and a third edge determination value; a first determination subunit, used to determine a minor fault level and use it as the first fault determination result when the first edge determination value is less than a preset first edge fault threshold, the second edge determination value is less than a preset second edge fault threshold, and the third edge determination value is less than a preset first edge fault threshold; a second determination subunit, used to determine a moderate fault level and use it as the first fault determination result when the first edge determination value is less than a preset third edge fault threshold and the third edge determination value is less than a preset third edge fault threshold; and a third determination subunit, used to determine a severe fault level and use it as the first fault determination result when the first edge determination value is greater than or equal to a preset third edge fault threshold, or the second edge determination value is greater than or equal to a preset first edge fault threshold and the third edge determination value is greater than or equal to a preset third edge fault threshold. Further, the third processing unit includes: an edge fault level determination result subunit, used to determine the fault interval where the gas content data of each edge characteristic gas is located, and generate multiple edge fault level determination results; wherein, the edge fault level determination result is any one of severe fault level, moderate fault level, and mild fault level; the fault levels are arranged from high to low as severe fault level, moderate fault level, and mild fault level; a first selection subunit, used to select the highest fault level from the multiple edge fault level determination results as the first fault determination result. Further, the second determination result submodule includes: a fourth processing unit, used to determine whether the gas type of the core characteristic gas meets the preset gas type conditions; a fifth processing unit, used to, if the gas type of the core characteristic gas meets the preset gas type conditions, then based on the three-ratio method, use the gas content data of each core characteristic gas to perform fault determination and generate a second fault determination result; a sixth processing unit, used to, if the gas type of the core characteristic gas does not meet the preset gas type conditions, then based on the interval judgment method, use the gas content data of each core characteristic gas to perform fault determination and generate a second fault determination result.Furthermore, the fifth processing unit includes: a core judgment value subunit, used to arbitrarily select the gas content data of two different core characteristic gases and perform a ratio operation to generate a first core judgment value, a second core judgment value, and a third core judgment value; a fourth judgment subunit, used to determine a minor fault level and use it as the second fault judgment result when the first core judgment value is less than a preset first core fault threshold, the second core judgment value is less than a preset second core fault threshold, and the third core judgment value is less than a preset first core fault threshold; a fifth judgment subunit, used to determine a moderate fault level and use it as the second fault judgment result when the first core judgment value is less than a preset third core fault threshold and the third core judgment value is less than a preset third core fault threshold; and a sixth judgment subunit, used to determine a severe fault level and use it as the second fault judgment result when the first core judgment value is greater than or equal to a preset third core fault threshold, or when the second core judgment value is greater than or equal to a preset first core fault threshold and the third core judgment value is greater than or equal to a preset third core fault threshold. Furthermore, the sixth processing unit includes: a core fault level determination result subunit, used to determine the fault range in which the gas content data of each core characteristic gas is located, and generate multiple core fault level determination results; wherein, the core fault level determination result is any one of severe fault level, moderate fault level, and mild fault level; the fault levels are arranged from high to low as severe fault level, moderate fault level, and mild fault level; a second selection subunit, used to select the highest fault level from the multiple core fault level determination results as the second fault determination result. Furthermore, the target transformer fault level determination submodule includes: a target fault value unit, used to input a preset target fault value function using the first fault value associated with the first determination result and the second fault value associated with the second determination result, and output the target fault value; a data output unit, used to retrieve a preset fault level key-value pair data table using the target fault value to determine the fault level of the target transformer.

[0340] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. In the several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for example, the division of units is merely a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed between each other can be through some interfaces, indirect coupling or communication connection between devices or units, and can be electrical, mechanical, or other forms. The above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for assessing the degree of transformer fault based on arc fault gas content, characterized by, The method comprises the following steps: An arc channel model of a target transformer under arc fault is constructed, and arc partition is performed to determine an edge temperature zone and a core temperature zone; A thermal decomposition gas content model of the target transformer is constructed based on a set of thermal decomposition reactions of alkane molecules of the target transformer; The construction of the thermal decomposition gas content model based on the set of thermal decomposition reactions of alkane molecules of the target transformer comprises: According to the theory of alkane thermal decomposition, a set of thermal decomposition reactions of alkane molecules of the thermal decomposition gas content model is established; A mole fraction reaction model is constructed by introducing a competition factor for characterizing a reaction path into the set of thermal decomposition reactions of alkane molecules; An equilibrium constant expression model is constructed by fitting the set of thermal decomposition reactions of alkane molecules according to a gas partial pressure definition formula; A balance influence expression model with temperature change is constructed by applying the law of thermodynamics; The thermal decomposition gas content model is built by coupling the mole fraction reaction model, the equilibrium constant expression model and the balance influence expression model; Electric parameter data and oil thermal characteristic data of the edge temperature zone and core equilibrium constant of the core temperature zone are obtained; Edge equilibrium constant of the edge temperature zone is determined based on the electric parameter data and the oil thermal characteristic data; The electric parameter data comprises arc current, arc voltage drop, arc length and arc duration, and the edge equilibrium constant of the edge temperature zone is determined based on the electric parameter data and the oil thermal characteristic data, which comprises: Arc energy is determined by using the arc current, the arc duration and the arc voltage drop; Total thermal decomposition reaction enthalpy change is determined by using the arc current, arc duration, the arc energy, the arc length and the oil thermal characteristic data; Reaction coefficient in the thermal decomposition reaction process is determined according to the total thermal decomposition reaction enthalpy change; A thermal decomposition equivalent temperature equation set is constructed based on the reaction coefficient and a preset thermal reaction enthalpy change function; The thermal decomposition equivalent temperature equation set is solved by using a numerical method to obtain an equivalent temperature; The edge equilibrium constant of the edge temperature zone is obtained by inputting the equivalent temperature into the balance influence expression model with temperature change for solving; The oil thermal characteristic data comprises specific heat capacity of insulating oil, oil hydrocarbon operating temperature, oil hydrocarbon vaporization temperature, latent heat of hydrocarbon oil vapor phase, specific heat ratio of insulating oil vapor, specific internal energy ratio of insulating oil vapor and atmospheric pressure, and the total thermal decomposition reaction enthalpy change is determined by using the arc current, arc duration, the arc energy, the arc length and the oil thermal characteristic data, which comprises: A first constant coefficient is determined by using the arc length; A second constant coefficient is determined by using a preset conversion coefficient, the specific heat ratio of insulating oil vapor and the specific internal energy ratio of insulating oil vapor; A third constant coefficient is determined by using the arc current and the arc duration; Oil hydrocarbon liquid-gas enthalpy increase is determined by using the first constant coefficient, the second constant coefficient, the third constant coefficient, the atmospheric pressure and the arc energy; Oil hydrocarbon liquid enthalpy increase is determined by using the specific heat capacity of insulating oil, the oil hydrocarbon operating temperature and the oil hydrocarbon vaporization temperature. Determine the total reaction enthalpy change of thermal decomposition by using the latent heat of the hydrocarbon oil in vapor phase, the liquid enthalpy increase of the oil hydrocarbon, and the liquid-gas enthalpy increase of the oil hydrocarbon; Input the core balance constant and the edge balance constant into the thermal decomposition gas content model to solve, and obtain the gas content data associated with the edge temperature zone and the core temperature zone, respectively; Determine the fault level of the target transformer based on the gas type condition and the gas content data associated with the edge temperature zone and the core temperature zone.

2. The method for evaluating the degree of transformer fault based on arc fault gas content according to claim 1, characterized in that, The method for determining the fault level of the target transformer based on the gas type condition and the gas content data associated with the edge temperature zone and the core temperature zone comprises: Determine whether the gas type of the edge characteristic gas in the edge temperature zone meets the preset gas type condition; If the gas type of the edge characteristic gas meets the preset gas type condition, determine the fault based on the three-ratio method and the gas content data of each edge characteristic gas to generate a first fault determination result; If the gas type of the edge characteristic gas does not meet the preset gas type condition, determine the fault based on the interval judgment method and the gas content data of each edge characteristic gas to generate a first fault determination result; Determine whether the gas type of the core characteristic gas in the core temperature zone meets the preset gas type condition; If the gas type of the core characteristic gas meets the preset gas type condition, determine the fault based on the three-ratio method and the gas content data of each core characteristic gas to generate a second fault determination result; If the gas type of the core characteristic gas does not meet the preset gas type condition, determine the fault based on the interval judgment method and the gas content data of each core characteristic gas to generate a second fault determination result; Input the first fault value associated with the first determination result and the second fault value associated with the second determination result into a preset target fault value function to output a target fault value; Retrieve the target fault value from a preset fault level key-value data table to determine the fault level of the target transformer.

3. The method for evaluating the degree of transformer fault based on arc fault gas content according to claim 2, characterized in that, The method for determining the fault based on the three-ratio method and the gas content data of each edge characteristic gas to generate a first fault determination result comprises: Arbitrarily select two different gas content data of the edge characteristic gas to generate a first edge determination value, a second edge determination value, and a third edge determination value; When the first edge determination value is less than a preset first edge fault threshold, the second edge determination value is less than a preset second edge fault threshold, and the third edge determination value is less than the preset first edge fault threshold, determine a light fault level as the first fault determination result; When the first edge determination value is less than a preset third edge fault threshold, and the third edge determination value is less than the preset third edge fault threshold, determine a moderate fault level as the first fault determination result; When the first edge determination value is greater than or equal to the preset third edge fault threshold value, or the second edge determination value is greater than or equal to the preset first edge fault threshold value and the third edge determination value is greater than or equal to the preset third edge fault threshold value, it is determined as a severe fault level, and is taken as a first fault determination result.

4. The method for evaluating the degree of transformer fault based on arc fault gas content according to claim 2, characterized in that, The interval-based determination method uses the gas content data of each edge characteristic gas to determine the fault, and generates a first fault determination result, including: Respectively determining the fault interval of the gas content data of each edge characteristic gas, and generating a plurality of edge fault level determination results; The edge fault level determination result is any one of a severe fault level, a moderate fault level and a mild fault level; The fault levels are in descending order of severe fault level, moderate fault level and mild fault level; The highest fault level is selected from the plurality of edge fault level determination results as the first fault determination result.

5. The method for evaluating the degree of transformer fault based on arc fault gas content according to claim 2, characterized in that, The three-ratio method uses the gas content data of each core characteristic gas to determine the fault, and generates a second fault determination result, including: Arbitrarily selecting the gas content data of two different core characteristic gases to perform ratio operation, generating a first core determination value, a second core determination value and a third core determination value; When the first core determination value is less than the preset first core fault threshold value, the second core determination value is less than the preset second core fault threshold value, and the third core determination value is less than the preset first core fault threshold value, it is determined as a mild fault level, and is taken as a second fault determination result; When the first core determination value is less than the preset third core fault threshold value, and the third core determination value is less than the preset third core fault threshold value, it is determined as a moderate fault level, and is taken as a second fault determination result; When the first core determination value is greater than or equal to the preset third core fault threshold value, or the second core determination value is greater than or equal to the preset first core fault threshold value and the third core determination value is greater than or equal to the preset third core fault threshold value, it is determined as a severe fault level, and is taken as a second fault determination result.

6. The method for evaluating the degree of transformer fault based on arc fault gas content according to claim 2, characterized in that, The interval-based determination method uses the gas content data of each core characteristic gas to determine the fault, and generates a second fault determination result, including: Respectively determining the fault interval of the gas content data of each core characteristic gas, and generating a plurality of core fault level determination results; The core fault level determination result is any one of a severe fault level, a moderate fault level and a mild fault level; The fault levels are in descending order of severe fault level, moderate fault level and mild fault level; The highest fault level is selected from the plurality of core fault level determination results as the second fault determination result.

7. A transformer fault degree assessment system based on arc fault gas content, characterized by, The transformer fault degree evaluation system based on arc fault gas content is used to implement the transformer fault degree evaluation method based on arc fault gas content as claimed in any one of claims 1-6, and the transformer fault degree evaluation system based on arc fault gas content includes: An arc partitioning module is configured to construct an arc channel model of a target transformer under arc fault and to perform arc partitioning to determine an edge temperature zone and a core temperature zone; A model constructing module is configured to construct a thermal decomposition gas content model of the target transformer based on a set of thermal decomposition reactions of alkane molecules of the target transformer; A data obtaining module is configured to obtain electrical parameter data and oil thermal characteristic data of the edge temperature zone and core equilibrium constant data of the core temperature zone; A data processing module is configured to determine edge equilibrium constant data of the edge temperature zone based on the electrical parameter data and the oil thermal characteristic data; A model solving module is configured to input the core equilibrium constant data and the edge equilibrium constant data into the thermal decomposition gas content model to solve the model and obtain gas content data associated with the edge temperature zone and the core temperature zone, respectively; A fault level determining module is configured to determine a fault level of the target transformer based on preset gas type conditions and the gas content data associated with the edge temperature zone and the core temperature zone.

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