Method and system for quantitative analysis of overheat failure gas of on-load tap changer contact

Abstract

The application discloses a kind of overheat fault gas quantitative analysis method and system of on-load tap-changer contact, the method of the present application includes constructing the multi-physics field coupling mathematical model of on-load tap-changer, define contact surface contact resistance;Solving multi-physics field coupling model obtains the time domain and spatial temperature distribution of on-load tap-changer contact surface, determine the highest temperature and the volume of overheated area;Calculate the local gas production rate of each fault characteristic gas;The local gas production rate of all fault characteristic gases in the volume of hot area is integrated to obtain the theoretical equilibrium concentration of each fault characteristic gas in oil, construct the mapping relationship between the overheating parameters of contact surface contact resistance and highest temperature and theoretical equilibrium concentration.The present application aims to solve the problem that the traditional oil dissolved gas analysis method relies on empirical criterion and has high hysteresis, break through the bottleneck that cannot simulate the whole process of "electric-thermal-flow-chemical" from mechanism level, realize the leap from qualitative diagnosis to quantitative prediction.

Description

Quantitative Analysis Method and System for Overheat Fault Gas of On-Load Tap Changer Contacts Technical Field

[0001] This invention relates to the field of fault detection technology for on-load tap changers, and specifically to a method and system for quantitative analysis of overheating fault gases in on-load tap changer contacts. Background Technology

[0002] On-load tap changers (OLTCs) are the core components of transformers for voltage regulation, and their operating status directly affects the stability and reliability of the entire power system. OLTCs change the number of turns in the transformer windings by switching contacts. During this process, the contact resistance between the contacts can abnormally increase due to mechanical wear, material aging, improper installation, or overload operation. This increased contact resistance leads to aggravated local Joule heating, causing a sharp rise in contact surface temperature and resulting in the typical fault of contact overheating. Contact overheating not only accelerates the erosion of the contacts themselves but also severely heats the surrounding insulating oil. When the temperature exceeds the thermal stability critical point of the insulating oil (usually above 300°C), the insulating oil undergoes violent chemical decomposition, producing characteristic gases such as hydrogen (H2), methane (CH4), ethane (C2H6), ethylene (C2H4), and acetylene (C2H2). The composition, concentration, and gas production rate of these gases have a clear correlation with the temperature of the overheated hotspot. Therefore, dissolved gas analysis (DGA) has long been regarded as the "gold standard" for diagnosing latent faults inside transformers and on-load tap changers.

[0003] However, existing fault diagnosis methods based on dissolved gas analysis in oil have several inherent limitations and technical bottlenecks when dealing with the specific problem of overheating of on-load tap changer contacts: First, traditional diagnostic methods rely on empirical criteria, which are subject to lag and uncertainty. Currently widely used methods, such as the Rogers ratio method, the David triangle method, and the IEC 60599 standard, are all based on statistical foundations of a large number of historical fault cases. These methods are effective for general faults (such as arcing and discharge), but cannot accurately reflect the physicochemical process of the specific fault of overheating of on-load tap changer contacts. Their criterion thresholds are fixed and cannot adapt to the diversity of different switch models, different oil types, and different load conditions. More importantly, an alarm is only triggered when the fault develops to a certain severity and the gas production accumulates to a level sufficient to be detected and exceeds the threshold; this is a "post-hoc" and delayed diagnosis, unable to achieve early warning. Second, existing technologies cannot establish a precise quantitative model from "overheating" to "gas production." Traditional dissolved gas analysis in oil can only tell you "what gases are present" and "what is the approximate fault type," but it cannot answer questions such as "what is the specific temperature of the overheating point," "how much has the contact resistance increased," or "what is the future gas production trend." There is a lack of precise, dynamic, and quantitative functional relationships between fault severity and gas concentration. This makes it difficult for maintenance personnel to judge the speed of fault development and the urgency of handling, easily leading to misjudgments (e.g., misjudging severe overheating as general overheating) or missed diagnoses (low gas concentration in the early stages of the fault, not reaching the threshold). Third, the complexity of the multi-physics coupling process is overlooked. Contact overheating and gas production is a strongly coupled process involving electromagnetic (current, resistance), temperature field (heating, conduction, convection), fluid field (oil flow diffusion), and chemical reaction field (oil molecule cracking). Most existing research or technologies only address a single perspective, such as experimentally measuring gas production data under a few conditions or performing simple thermal steady-state simulations. The lack of a sophisticated model that can fully reproduce the dynamic interaction process of the "electro-thermal-fluidic-chemical" multi-physics field means that the understanding of gas production patterns remains superficial, preventing accurate prediction at the mechanistic level. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a quantitative analysis method and system for overheating fault gases of on-load tap changer contacts, which addresses the above-mentioned problems of the existing technology. The present invention aims to solve the problems of traditional dissolved gas analysis (DGA) methods in oil relying on empirical criteria and having high lag, and to break through the bottleneck of not being able to simulate the entire process of "electro-thermal-fluidization" at the mechanistic level, so as to achieve a leap from qualitative diagnosis to quantitative prediction.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for quantitative analysis of overheated fault gas in on-load tap changer contacts, comprising the following steps:

[0007] S1, construct a multi-physics coupling mathematical model of an on-load tap changer;

[0008] S2, in the multiphysics coupling model, defines the contact resistance of the contact surface of the on-load tap changer. ;

[0009] S3. Solve the multiphysics coupling model to obtain the time-domain and spatial-domain temperature distributions on the surface of the on-load tap changer contacts. Determine the highest temperature and the volume of the overheated area ;

[0010] S4: Time-domain and spatial-domain temperature distribution based on the surface of on-load tap changer contacts The local gas generation rate of each fault characteristic gas was calculated using a thermal decomposition reaction kinetic model of insulating oil. ;

[0011] S5: Volume of the heated area Local gas production rate of all fault characteristic gases within By integrating and taking into account fluid transport effects, the theoretical equilibrium concentrations of each fault-specific gas in the oil are calculated. The contact resistance of the contact surface of the on-load tap changer contacts and highest temperature As the overheating parameters of the on-load tap changer contacts, the current overheating parameters of the on-load tap changer contacts and the theoretical equilibrium concentrations of various fault characteristic gases in the oil are obtained. The mapping relationship between them.

[0012] Optionally, the multiphysics coupling mathematical model constructed in step S1 includes a mathematical model coupling electromagnetic field, temperature field, and fluid field. The electromagnetic field is described by a simplified Ohm's law Joule heating model based on Maxwell's equations. The functional expression of the heat source term in the simplified Ohm's law Joule heating model is:

[0013] ;

[0014] in, The Joule heat source density is the heat source term. For the electrical conductivity of the material, The potential gradient is used; the temperature field is described by a heat conduction equation containing heat source and convection terms, and the functional expression of the heat conduction equation is:

[0015] ;

[0016] in, For density, For specific heat capacity, for about The partial derivatives, For temperature, For time, The fluid velocity field of the insulating oil. For temperature gradient, For gradient operators, The thermal conductivity is given; the fluid field is described by the Navier-Stokes equations and the continuity equation for incompressible flow, and is used to calculate the fluid velocity field of the insulating oil. The functional expressions for the Navier-Stokes equations and the continuity equation of the incompressible flow, and its cooling effect on the temperature field, are as follows:

[0017] ;

[0018] ;

[0019] in, for about The partial derivatives, For pressure, For unit tensors, It is a volume force.

[0020] Optionally, in step S4, the local gas generation rate of each fault characteristic gas is calculated using a thermal decomposition reaction kinetic model of insulating oil. At that time, the functional expression of the thermal decomposition reaction kinetic model of the insulating oil is:

[0021] ;

[0022] in, Pre-exponential factor, The activation energy of the reaction. Let be the ideal gas constant. For local absolute temperature, The local concentration of insulating oil, where the pre-exponential factor is... and activation energy of reaction This was obtained through prior calibration.

[0023] Optionally, in step S5, the volume of the hot region is... Local gas production rate of all fault characteristic gases within By integrating and taking into account fluid transport effects, the theoretical equilibrium concentrations of each fault-specific gas in the oil are calculated. The function expression is:

[0024] ,

[0025] in, This represents the total volume of insulating oil in the oil-filled conservator. This represents the volume of the thermal region.

[0026] Optionally, the fault characteristic gas includes some or all of acetylene, ethylene, methane, and hydrogen.

[0027] Optionally, it also includes the contact resistance of the contact surface of the on-load tap changer contacts. The overheating parameters of the on-load tap changer contacts and the theoretical equilibrium concentrations of various fault characteristic gases in the oil were obtained by sampling under various value conditions. A quantitative mapping table is constructed to establish the mapping relationships between various on-load tap changer contacts and the theoretical equilibrium concentrations of various fault characteristic gases in the oil. The mapping relationship between them.

[0028] Optionally, after step S5, the method further includes: based on the overheating parameters of various on-load tap changer contacts and the theoretical equilibrium concentration of each fault characteristic gas in the oil. A quantitative relationship mapping table is constructed based on the mapping relationships between them; the theoretical equilibrium concentrations of each fault characteristic gas detected by the sensor in the oil are obtained. Through theoretical equilibrium concentration The overheating parameters of the corresponding on-load tap changer contacts are obtained by looking up the quantitative relationship mapping table. The overheating parameters of the on-load tap changer contacts are then input into a pre-trained machine learning model to obtain the detection result of whether the on-load tap changer contacts are faulty. The machine learning model is pre-trained and has established a mapping relationship between the overheating parameters of the on-load tap changer contacts and whether the on-load tap changer contacts are faulty.

[0029] The present invention also provides a quantitative analysis system for overheating fault gas of on-load tap changer contacts, including a microprocessor and a memory interconnected thereto, wherein the microprocessor is programmed or configured to execute the quantitative analysis method for overheating fault gas of the on-load tap changer contacts.

[0030] The present invention also provides a computer-readable storage medium storing a computer program or instructions that are programmed or configured to execute, via a processor, the method for quantitative analysis of overheated fault gas of the on-load tap changer contacts.

[0031] The present invention also provides a computer program product, including a computer program or instructions, which are programmed or configured to execute, via a processor, the method for quantitative analysis of overheated fault gas of the on-load tap changer contacts.

[0032] Compared with existing technologies, this invention mainly achieves the following beneficial effects: 1. Clear mechanism, innovation from the source: This invention abandons the traditional "black box" diagnostic model based on statistical experience, and for the first time organically integrates multiple physicochemical processes such as Joule heating effect, heat conduction, fluid convection cooling, and chemical reaction kinetics into a unified simulation framework. Starting from the first principles of matter and energy transfer, it reveals the intrinsic mechanism of gas generation in contact overheating faults, achieving a fundamental breakthrough in methodology. 2. Precise quantification, significantly advanced early warning capability: By introducing the Arrhenius equation and multi-field coupling calculation, this invention can accurately calculate the real-time gas generation rate and theoretical equilibrium concentration of various characteristic gases under different degrees of overheating, and can accurately predict the actual temperature and historical contact resistance changes of the contact. This allows for accurate early warning at the very early stage of fault occurrence, i.e., when the gas generation concentration is far below the alarm threshold of traditional methods, greatly improving the sensitivity and reliability of condition monitoring. 3. Strong universality and good adaptability: All physical parameters of the model (such as material properties and reaction kinetic parameters) can be calibrated and modified according to the actual switch model and oil type. Therefore, this method can be flexibly applied to on-load tap changers of different types and operating conditions, overcoming the shortcomings of the traditional fixed ratio method in terms of poor adaptability, and providing a universal solution for the refined and intelligent operation and maintenance of power equipment. 4. Strong guidance, combining theoretical and engineering value: The quantitative relationship mapping table generated by this invention can not only serve as an advanced analysis kernel for online monitoring systems, but also has significant scientific research and engineering guidance value. It can be used to analyze the impact of different design parameters on overheating risk and optimize switch design; it can also be used to simulate extreme operating conditions and assess equipment safety margins, thereby taking intervention measures before a fault occurs, avoiding accidents, and generating significant economic and safety benefits. Attached Figure Description

[0033] Figure 1 is a schematic diagram of the basic process of the method according to an embodiment of the present invention.

[0034] Figure 2 is a simulation model of the key contacts of the on-load tap changer in an embodiment of the present invention.

[0035] Figure 3 is a schematic diagram of the electromagnetic field setting of the key contacts of the on-load tap changer in an embodiment of the present invention.

[0036] Figure 4 is a schematic diagram of the temperature field setting of the key contacts of the on-load tap changer in an embodiment of the present invention.

[0037] Figure 5 is a streamline diagram of some fault characteristic gases of the critical contacts of the on-load tap changer in an embodiment of the present invention. Detailed Implementation

[0038] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings in the embodiments of the present invention.

[0039] As shown in Figure 1, the quantitative analysis method for overheating fault gas of on-load tap changer contacts in this embodiment includes the following steps:

[0040] S1, construct a multi-physics coupling mathematical model of an on-load tap changer;

[0041] S2, in the multiphysics coupling model, defines the contact resistance of the contact surface of the on-load tap changer. ;

[0042] S3. Solve the multiphysics coupling model to obtain the time-domain and spatial-domain temperature distributions on the surface of the on-load tap changer contacts. Determine the highest temperature and the volume of the overheated area ;

[0043] S4: Time-domain and spatial-domain temperature distribution based on the surface of on-load tap changer contacts The local gas generation rate of each fault characteristic gas was calculated using a thermal decomposition reaction kinetic model of insulating oil. ;

[0044] S5: Volume of the heated area Local gas production rate of all fault characteristic gases within By integrating and taking into account fluid transport effects, the theoretical equilibrium concentrations of each fault-specific gas in the oil are calculated. The contact resistance of the contact surface of the on-load tap changer contacts and highest temperature As the overheating parameters of the on-load tap changer contacts, the current overheating parameters of the on-load tap changer contacts and the theoretical equilibrium concentrations of various fault characteristic gases in the oil are obtained. The mapping relationship between them.

[0045] The core of the quantitative analysis method for overheating fault gas of on-load tap changer contacts in this embodiment lies in constructing a digital twin model through computer simulation technology to accurately reproduce the entire process from abnormal contact heating to gas generation from the decomposition of insulating oil. Specifically, based on the actual geometric structure of the on-load tap changer, this embodiment establishes a comprehensive model of coupled electromagnetic field, temperature field and fluid field—a multiphysics coupled mathematical model—in a simulation platform (such as COMSOL Multiphysics).

[0046] For example, in this embodiment, a three-dimensional geometric model is constructed in COMSOL Multiphysics 6.3 based on the CAD drawings of the on-load tap changer, as shown in Figure 2. The key components of the three-dimensional geometric model include: the moving contact (upper contact), the stationary contact (lower contact), the transition resistance, and the sealed oil chamber structure. To balance computational efficiency and accuracy, a simplified 3D model is adopted, while retaining the geometric details of key physical areas (such as the contact surface and oil gap channels). Local mesh refinement is applied to the contact area, with the smallest element size reaching 0.1 mm, to ensure accurate capture of the Joule heat source and temperature gradient. The material properties in the three-dimensional geometric model are defined as follows: Contact (copper-tungsten alloy Cu-W80): Electrical conductivity σ = 2.5e7 S / m; Density ρ = 14200 kg / m³; Thermal conductivity k = 180 W / (m·K); Constant pressure heat capacity... =210 J / (kg·K); Insulating oil (mineral oil, model KI50X): Density ρ = 860 kg / m³; Dynamic viscosity μ = 8.5e-3 Pa·s; Thermal conductivity k = 0.13 W / (m·K); Constant pressure heat capacity Cp = 1950 J / (kg·K); Volume expansion coefficient β = 7.8e-41 / K. Oil-gas mixture parameters: Considering the influence of gas evolution on fluid properties, a mixture model is used to correct for density and viscosity.

[0047] The multiphysics coupled mathematical model constructed in step S1 of this embodiment includes a mathematical model coupling electromagnetic field, temperature field, and fluid field, implemented through electromagnetic field module, fluid field module, and temperature field module, respectively. Fluid field module: Enables the "laminar flow" interface and activates the "Bussinesk approximation" to simulate the natural convection of oil. Sets the oil chamber wall as an isothermal boundary. =343.15 K. Temperature field module: Using the "Solid and Fluid Heat Transfer" interface, the electromagnetic heat source is coupled with the fluid convection term to set the initial oil temperature. = 333.15 K. Chemical reaction module: The Arrhenius reaction kinetic model is embedded through the "coefficient type partial differential equation" interface to define the generation rates of five characteristic gases (H2, CH4, C2H6, C2H4, C2H2).

[0048] The electromagnetic field module is used to calculate the current distribution and the Joule heat source. In this embodiment, the electromagnetic field is described by a simplified Ohm's law Joule heating model based on Maxwell's equations. The functional expression of the heat source term in the simplified Ohm's law Joule heating model is:

[0049] ;

[0050] in, denoted as Joule heat source density (W / m³) for the heat source term. The electrical conductivity of the material (S / m). The potential gradient is (V / m); Figure 3 is a schematic diagram of the electromagnetic field setting of the key contacts of the on-load tap changer in this embodiment.

[0051] The electromagnetic field module is used to calculate the current distribution and Joule heat source. In this embodiment, the temperature field is used to calculate the temperature distribution of the contacts and the surrounding oil area. In this embodiment, the temperature field is described by a heat conduction equation that includes heat source terms and convection terms. The functional expression of the heat conduction equation is:

[0052] ;

[0053] in, Density (kg / m³) Specific heat capacity (J / (kg·K)) for about The partial derivatives, Temperature (K) For time (s), The fluid velocity field (m / s) of the insulating oil. For temperature gradient, For gradient operators, The value is the thermal conductivity (W / (m·K)). Figure 4 is a schematic diagram of the temperature field setting of the key contacts of the on-load tap changer in the embodiment.

[0054] The fluid field module is used to calculate the flow and cooling effects of insulating oil. In this embodiment, the fluid field is described by the Navier-Stokes equations and the continuity equation for incompressible flow, and is used to calculate the fluid velocity field of the insulating oil. The functional expressions for the Navier-Stokes equations (NS equations) and the continuity equation of the incompressible flow, and their cooling effect on the temperature field, are as follows:

[0055] ;

[0056] ;

[0057] in, for about The partial derivatives, Pressure (Pa). For unit tensors, It is a volume force (N / m³).

[0058] In step S2 of this embodiment, the contact resistance of the contact surface of the on-load tap changer is defined in the multiphysics coupling model. In the multiphysics coupling model, the contact resistance of the contact surface is set. To simulate overheating faults of different degrees. The value range is set to 1.5 to 50 times the normal value to cover various actual operating conditions, from slight oxidation to severe ablation. The core of this embodiment lies in simulating and covering various overheating faults that may occur in on-load tap changer contacts during actual operation by purposefully setting different simulation conditions. The strategy is to parameterize the equivalent contact resistance of the contacts. In addition to other key operating parameters, it can efficiently and accurately reproduce different fault severity levels, from slight aging to severe ablation.

[0059] To simulate poor contact, this embodiment does not employ a complex dynamic model, but instead uses a direct and efficient parameterization method: in the simulation, an equivalent contact resistance greater than its normal value is set for the contact surface. The resistance value It is a configurable core simulation parameter used to characterize the overall contact state deterioration of the contact. Different settings can be used to... Numerical values ​​can directly simulate different degrees of faults: (1) Slight overheating (early fault): Set It is 1.5 to 5 times the normal value. This range is used to simulate the initial aging state of slight oxidation of the contact surface or slight decrease in contact pressure. (2) Severe overheating (developmental failure): set It is 5 to 20 times the normal value. This range is used to simulate faults where there is obvious ablation, thickening of oxide film, or significant insufficient spring pressure on the contact surface. (3) Critical overheating (critical fault): set This range is 20 to 50 times or even higher than the normal value. This range is used to simulate extreme conditions where the contacts are about to fuse or have already experienced severe arc erosion. Contact resistance. It is not a fixed value, but is closely related to the contact pressure, the degree of surface oxidation, and the temperature at the contact point.

[0060] This embodiment uses the following empirical-physical model for dynamic simulation: Based on the above principles, this embodiment demonstrates its effectiveness by setting the following two typical operating conditions: (1) Long-term operation aging condition: Objective: To simulate the gradual performance degradation caused by long-term operation. Parameter settings: In the simulation, a parameter that increases slowly over time is set. Functions, for example, linearly increase from the normal value to 10 times. At the same time, set the load current to the rated value. (2) Sudden severe fault condition: Objective: Simulate sudden severe overheating caused by mechanical jamming or foreign object intrusion. Parameter settings: At a certain moment in the simulation, the load current will be set to the rated value. The value is set to a relatively high fixed value (e.g., 30 times the normal value) to simulate a sudden deterioration of the contact condition. Simultaneously, a relatively high load current (e.g., 1.5 times the rated current) can be set to simulate overload conditions. To achieve the above settings, the solution strategy in this embodiment is as follows: Boundary condition setting: In the electromagnetic field module of the simulation software, the boundary condition of the contact surface is set to "contact resistance boundary," and a defined value is assigned to it. Value. Solver settings: A transient solver is used to simulate the dynamic process of fault occurrence and development. By setting a reasonable total simulation time and initial time step, it is ensured that the calculation can effectively capture the entire process of contact temperature rise and gas generation. In summary, the core of this section is to clarify: by setting the "equivalent contact resistance" with evidence. "This key parameter allows for the concise and effective construction of various simulation scenarios for quantitative analysis of fault gases, avoiding the unreliability of complex models and ensuring the efficiency and practicality of the method."

[0061] In this embodiment, solving the multiphysics coupling model in step S3 is a basic function of the simulation platform (such as COMSOL Multiphysics). The solution can obtain the time-domain and spatial-domain temperature distribution of the on-load tap changer contact surface. Determine the highest temperature and the volume of the overheated area The volume of the overheated region This represents the volume of the region where the temperature exceeds a preset threshold. Specifically, in this embodiment, a fully coupled transient solver is used to solve the model that includes dynamic resistance and possible arcing. The total simulation time covers a single switching cycle and the subsequent heat diffusion process (e.g., 10 seconds). After solving, the four-dimensional temperature field data T(x,y,z,t) is extracted. Through post-processing, not only the highest temperature on the contact surface is obtained... The dynamic curves also utilize isosurface extraction and volume integration to quantify the volume of the overheated region where the temperature exceeds the insulating oil's decomposition initiation temperature (e.g., 300°C). . and It is a key topological parameter that determines the total amount and rate of gas production.

[0062] The core of the characteristic gas generation path simulation based on series reaction kinetics is to quantify the complex chemical reaction of thermal decomposition of insulating oil using a defined kinetic path. Insulating oil (characterized by typical alkane C...) 16 H 34 The thermal decomposition of a gas (e.g., ) is a series reaction process. This embodiment simplifies it into two key stages, corresponding to specific characteristic gases:

[0063] (1) Primary cleavage (long chain breakage):

[0064] ;

[0065] This stage is dominated by moderate superheating temperatures (approximately 300-500°C), primarily producing methane (CH4), ethane (C2H6), ethylene (C2H4), and hydrogen (H2).

[0066] (2) Secondary cracking (deep dehydrogenation of ethylene):

[0067] ;

[0068] This stage occurs significantly at high temperatures or in locally extremely hot regions (>700°C) where electric arcs are present, and is the main pathway for the formation of the characteristic gas acetylene (C2H2), accompanied by the production of additional hydrogen (H2). In COMSOL, the unique Arrhenius equation parameters (pre-factors) can be set for each of the above reactions through the "Chemical Reaction Engineering Module" interface. ,activation energy For example, the activation energy of acetylene formation. The highest value (set at 260 kJ / mol) reflects the higher energy required for its formation. The obtained spatial temperature field T(x,y,z,t) is used as input, coupled with the above reaction kinetic equations. The software will calculate the local gas production rates of acetylene (C2H2), ethylene (C2H4), methane (CH4), and hydrogen (H2) in real time at each grid cell and each time step. Therefore, a spatial distribution cloud map of the gas generation rate for each gas can be obtained, clearly showing that the contact hotspot and arc channel are the core gas generation sources. In step S4 of this embodiment, the local gas generation rate of each fault characteristic gas is calculated using an insulation decomposition reaction kinetic model. Specifically, the thermal decomposition reaction kinetic model of insulating oil adopts the Arrhenius equation, and the functional expression of the thermal decomposition reaction kinetic model of insulating oil is as follows:

[0069] ;

[0070] in, Let be the local gas production rate of fault characteristic gas i (mol / (m³·s)). is the pre-exponential factor (1 / s). The activation energy of the reaction is expressed in J / mol. It is the ideal gas constant (8.314 J / (mol·K)). The local absolute temperature (K) is given. The local concentration of insulating oil (mol / m³), where the pre-exponential factor is... and activation energy of reaction This is obtained through pre-calibration, for example, via thermogravimetric analysis or authoritative literature data. Here, i represents the serial number of the fault characteristic gas. In this embodiment, the fault characteristic gases include acetylene (C2H2), ethylene (C2H4), methane (CH4), and hydrogen (H2); wherein, the activation energy of the reaction of acetylene (C2H4) is... The highest value is between 200-280 kJ / mol. Figure 5 is a streamline diagram of some fault characteristic gases of the critical contacts of the on-load tap changer in this embodiment.

[0071] For the entire overheated area The volume fraction of all gases generated by the internal micro-elements is calculated, taking into account their dissolution and transport in the oil, to determine the theoretical equilibrium concentration of each gas in the oil. Considering that the generated dissolved gases do not remain stationary but flow with the insulating oil and diffuse, this embodiment introduces a more accurate convection-diffusion equation to correct the simple volume fraction. The governing equation is as follows:

[0072] ;

[0073] in, Let i be the local molar concentration of gas i. Let be the diffusion coefficient of the gas in the oil, and u be the velocity vector field obtained from the fluid field solution. This equation is implemented in COMSOL through the "Dilution Species Transfer" interface and bidirectionally coupled with the "Laminar Flow" and "Heat Transfer" interfaces, thus completely simulating the dynamic process of gas generation, flow transport, and homogenization in the oil. By solving the above convection-diffusion equation, the gas concentration distribution at any location and time in the oil during the simulation period can be obtained. The theoretical equilibrium concentrations of each fault-specific gas in the oil are also shown. Defined as the total volume of the oil conservator at the end of the simulation. The average internal gas concentration is calculated by volume average integration. In step S5 of this embodiment, the volume of the thermal region... Local gas production rate of all fault characteristic gases within By integrating and taking into account fluid transport effects, the theoretical equilibrium concentrations of each fault-specific gas in the oil are calculated. The function expression is:

[0074] ,

[0075] in, This represents the total volume of insulating oil in the oil-filled conservator. This represents the volume of the thermal region.

[0076] To verify the accuracy of the model, the theoretical equilibrium concentrations of each fault-specific gas in the oil can be calculated. The results were compared with laboratory oil chromatography (DGA) data under the same operating conditions. In the verification case of this embodiment, the relative error between the simulated value and the measured value was small, proving that the calculation method has good engineering accuracy and reliability.

[0077] Repeat steps S2 to S5 to simulate a series of overheating faults of varying severity (i.e., different...). The database establishes a quantitative relationship mapping table in the form of a multidimensional database, enabling the systematic simulation of dozens to hundreds of fault scenarios covering different dynamic resistance trajectories, arc energies, and load currents. This mapping library uses contact overheating parameters (…) , ( ) is used as input, with the theoretical equilibrium concentration of each fault characteristic gas in the oil. ( ) is the output.

[0078] This embodiment also includes the contact resistance of the contact surface of the on-load tap changer contact. The overheating parameters of the on-load tap changer contacts and the theoretical equilibrium concentrations of various fault characteristic gases in the oil were obtained by sampling under various value conditions. A quantitative mapping table is constructed to establish the mapping relationships between various on-load tap changer contacts and the theoretical equilibrium concentrations of various fault characteristic gases in the oil. The mapping relationship between them. A quantitative mapping table can exist in the form of a multidimensional database. It can be established through interpolation based on the theoretical equilibrium concentrations of each fault characteristic gas in the oil. The reverse mapping query yields the predicted maximum temperature on the contact surface. And contact resistance estimation Furthermore, through an interpolation algorithm, this quantitative relationship mapping table can be used to reverse-map a set of measured gas concentrations to find the best-matching contact surface for predicting the highest temperature. And contact resistance estimation This enables accurate quantification and early warning of faults.

[0079] The quantitative relationship mapping table, as the core of intelligent diagnosis, can use an efficient query algorithm to determine the theoretical equilibrium concentration of each fault characteristic gas in the oil based on real-time monitoring. This allows for rapid and accurate reverse deduction of the most likely overheating temperature, contact state, and fault development stage within the on-load tap changer contacts, enabling proactive early warning and precise maintenance. For example, as an optional implementation, this embodiment further includes the following after step S5: ① Based on the overheating parameters of various on-load tap changer contacts and the theoretical equilibrium concentration of each fault characteristic gas in the oil... ① Construct a quantitative relationship mapping table based on the mapping relationship between them; ② Obtain the theoretical equilibrium concentration of each fault characteristic gas in the oil detected by the sensor. ③ Through theoretical equilibrium concentration The overheating parameters of the corresponding on-load tap changer contacts are obtained by looking up a quantitative relationship mapping table. These parameters are then input into a pre-trained machine learning model to obtain a detection result indicating whether a fault exists in the on-load tap changer contacts. The machine learning model has been pre-trained and has established a mapping relationship between the overheating parameters of the on-load tap changer contacts and the presence of a fault. Among these, the overheating parameters of the on-load tap changer contacts include, in addition to, the contact resistance of the contact surface. and highest temperature In addition, the volume of the thermal zone can be further increased. These features serve as input to improve the prediction accuracy of machine learning models. Machine learning models can be implemented using multilayer perceptrons (MLPs) or other neural network models.

[0080] In summary, this embodiment introduces modeling and simulation based on multiphysics simulation platforms such as COMSOL Multiphysics. Starting from first principles, it constructs a quantitative model that can accurately describe the entire process from abnormal contact heating to gas production from insulating oil decomposition. This fills the gap between existing technologies in terms of judgment and quantitative analysis, and has the following advantages: 1. This embodiment solves the problem of traditional dissolved gas analysis (DGA) methods relying on empirical criteria and having high lag. Existing methods such as Rogers ratio and David's triangle cannot establish an accurate and dynamic quantitative relationship between contact overheating and gas concentration in the early stages of a fault, leading to delayed warnings and false alarms. This embodiment, by constructing a multiphysics coupled mathematical model for solving on-load tap changers, overcomes the problems of relying on empirical criteria and high lag. 2. This embodiment overcomes the bottleneck of being unable to simulate the entire "electro-thermal-fluidization" process at the mechanistic level. Existing technologies lack a comprehensive model that can fully describe the complex coupled process of Joule heating from current, oil heating, oil decomposition and gas production, and gas diffusion and transport. This embodiment, however, constructs a multi-physics coupled mathematical model for solving on-load tap changers, which can fully describe this complex coupled process. 3. This embodiment achieves a leap from qualitative diagnosis to quantitative prediction. This embodiment can not only determine whether overheating exists, but also accurately calculate the temperature of the overheated spot, the gas production rate, and future gas concentration changes using a high-precision method, providing a solid data foundation for predictive maintenance. The method in this embodiment solves the key problem that traditional methods cannot accurately quantify the dynamic relationship between contact overheating and dissolved gas generation in the oil in the early stages of a fault, providing accurate theoretical basis and data support for predictive maintenance of on-load tap changers.

[0081] Furthermore, this embodiment also provides a quantitative analysis system for overheated fault gases of on-load tap changer contacts, including a microprocessor and a memory interconnected, wherein the microprocessor is programmed or configured to execute the quantitative analysis method for overheated fault gases of the on-load tap changer contacts. This embodiment also provides a computer-readable storage medium storing a computer program or instructions programmed or configured to execute the quantitative analysis method for overheated fault gases of the on-load tap changer contacts via a processor. This embodiment also provides a computer program product including a computer program or instructions programmed or configured to execute the quantitative analysis method for overheated fault gases of the on-load tap changer contacts via a processor.

[0082] Those skilled in the art will understand that the technical solutions provided by this invention may take the form of a method, system, or computer program product. Therefore, this invention may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this invention may take the form of a computer program product embodied on one or more computer-readable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in one or more blocks of the flowchart illustrations and / or one or more blocks of the block diagrams. These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement the functions specified in one or more flowcharts and / or one or more block diagrams. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more block diagrams.

[0083] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for quantitative analysis of overheated fault gas in on-load tap changer contacts, characterized in that, The process includes the following steps: S1, constructing a multi-physics coupling mathematical model of the on-load tap changer; S2, defining the contact resistance of the on-load tap changer contacts within the multi-physics coupling model. S3, Solve the multiphysics coupling model to obtain the time-domain and spatial-domain temperature distributions on the surface of the on-load tap changer contacts. Determine the highest temperature and the volume of the overheated area S4: Time-domain and spatial-domain temperature distribution of on-load tap changer contact surface The local gas generation rate of each fault characteristic gas was calculated using a thermal decomposition reaction kinetic model of insulating oil. S5: Volume of the thermal region Local gas production rate of all fault characteristic gases within By integrating and taking into account fluid transport effects, the theoretical equilibrium concentrations of each fault-specific gas in the oil are obtained. The contact resistance of the contact surface of the on-load tap changer contacts and highest temperature As the overheating parameters of the on-load tap changer contacts, the current overheating parameters of the on-load tap changer contacts and the theoretical equilibrium concentrations of various fault characteristic gases in the oil are obtained. The mapping relationship between them.

2. The method for quantitative analysis of overheated fault gas in on-load tap changer contacts according to claim 1, characterized in that, The multiphysics coupling mathematical model constructed in step S1 includes a mathematical model coupling electromagnetic field, temperature field, and fluid field. The electromagnetic field is described by a simplified Ohm's law Joule heating model based on Maxwell's equations. The functional expression of the heat source term in the simplified Ohm's law Joule heating model is as follows: ;in, The Joule heat source density is the heat source term. For the electrical conductivity of the material, The potential gradient is used; the temperature field is described by a heat conduction equation containing heat source and convection terms, and the functional expression of the heat conduction equation is: ;in, For density, For specific heat capacity, for about The partial derivatives, For temperature, For time, The fluid velocity field of the insulating oil. For temperature gradient, For gradient operators, The thermal conductivity is given; the fluid field is described by the Navier-Stokes equations and the continuity equation for incompressible flow, and is used to calculate the fluid velocity field of the insulating oil. The functional expressions for the Navier-Stokes equations and the continuity equation of the incompressible flow, and its cooling effect on the temperature field, are as follows: ； ;in, for about The partial derivatives, For pressure, For unit tensors, It is a volume force.

3. The method for quantitative analysis of overheated fault gas in on-load tap changer contacts according to claim 1, characterized in that, In step S4, the local gas generation rate of each fault characteristic gas is calculated using the thermal decomposition reaction kinetic model of insulating oil. At that time, the functional expression of the thermal decomposition reaction kinetic model of the insulating oil is: ;in, Pre-exponential factor, The activation energy of the reaction. Let be the ideal gas constant. For local absolute temperature, The local concentration of insulating oil, where the pre-exponential factor is... and activation energy of reaction This was obtained through prior calibration.

4. The method for quantitative analysis of overheated fault gas in on-load tap changer contacts according to claim 1, characterized in that, In step S5, the volume of the hot zone is... Local gas production rate of all fault characteristic gases within By integrating and taking into account fluid transport effects, the theoretical equilibrium concentrations of each fault-specific gas in the oil are obtained. The function expression is: ,in, This represents the total volume of insulating oil in the oil-filled conservator. Let be the volume of the thermal region.

5. The method for quantitative analysis of overheated fault gas in on-load tap changer contacts according to claim 1, characterized in that, The fault-specific gases include some or all of acetylene, ethylene, methane, and hydrogen.

6. The method for quantitative analysis of overheated fault gas in on-load tap changer contacts according to claim 1, characterized in that, This also includes the contact resistance of the contact surface of the on-load tap changer contacts. The overheating parameters of the on-load tap changer contacts and the theoretical equilibrium concentrations of various fault characteristic gases in the oil were obtained by sampling under various value conditions. A quantitative mapping table is constructed to establish the mapping relationships between various on-load tap changer contacts and the theoretical equilibrium concentrations of various fault characteristic gases in the oil. The mapping relationship between them.

7. The method for quantitative analysis of overheated fault gas in on-load tap changer contacts according to claim 6, characterized in that, Step S5 is followed by: based on the overheating parameters of various on-load tap changer contacts and the theoretical equilibrium concentration of each fault characteristic gas in the oil. A quantitative relationship mapping table is constructed based on the mapping relationships between them; the theoretical equilibrium concentrations of each fault characteristic gas detected by the sensor in the oil are obtained. Through theoretical equilibrium concentration The overheating parameters of the corresponding on-load tap changer contacts are obtained by looking up the quantitative relationship mapping table. The overheating parameters of the on-load tap changer contacts are then input into a pre-trained machine learning model to obtain the detection result of whether the on-load tap changer contacts are faulty. The machine learning model is pre-trained and has established a mapping relationship between the overheating parameters of the on-load tap changer contacts and whether the on-load tap changer contacts are faulty.

8. A quantitative analysis system for overheated fault gases of on-load tap changer contacts, comprising a microprocessor and a memory interconnected, characterized in that, The microprocessor is programmed or configured to execute the quantitative analysis method for overheated fault gas of on-load tap changer contacts according to any one of claims 1 to 7.

9. A computer-readable storage medium storing a computer program or instructions, characterized in that, The computer program or instructions are programmed or configured to execute, via a processor, the quantitative analysis method for overheating fault gas of on-load tap changer contacts as described in any one of claims 1 to 7.

10. A computer program product, comprising a computer program or instructions, characterized in that, The computer program or instructions are programmed or configured to execute, via a processor, the quantitative analysis method for overheating fault gas of on-load tap changer contacts as described in any one of claims 1 to 7.

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