Bubble initial temperature calculation method of oiled paper system and related device

Abstract

The invention discloses a bubble initial temperature calculation method of an oil paper system and a related device, and the method comprises the steps: collecting operation state parameters of an in-service transformer during operation, carrying out the molecular simulation calculation according to the operation state parameters, and obtaining the micro-water aggregation rate of water molecules on an oil paper interface of an insulating oil paper system; guiding the flow rate of liquid water in the oil-paper system finite element model entering the insulation paper finite element model through the micro-water aggregation rate, and calculating the bubble initial temperature of the oil-paper system through the oil-paper system finite element model. The technical problems of low measurement efficiency and large measurement result error in the prior art are solved.

Description

Technical Field

[0001] This application relates to the technical field of transformers, and particularly to a method for calculating the bubble initiation temperature of an oil-paper system and related devices. Background Art

[0002] As a core device in the power transmission network, the safety of power transformers is directly related to the stable operation of the power grid. The power system faces many challenges during long-term operation, and faults caused by transformer equipment are one of the most common accident causes. The oil-paper insulation system in transformers is widely used due to its high electrical insulation performance and economy. However, under the action of long-term electrical loads, the oil-paper materials will age, leading to the formation of internal bubbles.

[0003] The formation of bubbles is mainly due to the evaporation of moisture in the insulating paper and the accumulation of gases. As the temperature rises, gas molecules in the insulating oil aggregate to form bubbles, thereby reducing the dielectric performance of the insulating material and further causing partial discharge and electric field distortion. Research shows that in a high-temperature environment, water vapor is the main component of bubbles in the oil-paper insulation system. Especially when the temperature exceeds 120°C, the water vapor content in the bubbles can reach 91.2%. Once these bubbles accumulate excessively, it will seriously threaten the normal operation of the transformer and may ultimately lead to insulation breakdown or equipment failure.

[0004] Existing standards recommend that the hot spot temperature of transformers should be controlled within 140°C to reduce the generation of bubbles and ensure safe operation. However, with the changes in the working environment and operating conditions of transformers, traditional temperature control standards may not be able to fully cope with all operating conditions, and the critical temperature for bubble formation is affected by various factors and still requires further research and verification. Therefore, how to accurately predict the generation temperature of bubbles based on the real-time operating data of transformers and discover potential risks in advance during the operation of transformers through effective monitoring means is a key technical challenge to ensure the safe operation of power equipment.

[0005] The existing technology builds a small-scale transformer winding simulation test platform in the laboratory, prepares insulating paper samples with gradient water contents, and measures the bubble initiation temperatures with different water contents on the platform. However, the sample preparation process is complex, the acquisition of test data is cumbersome, the measurement efficiency is low, and the measurement results have large errors. Summary of the Invention

[0006] This application provides a method for calculating the bubble initiation temperature of an oil-paper system and related devices, which is used to improve the technical problems of low measurement efficiency and large measurement error results existing in the prior art.

[0007] In view of this, the first aspect of this application provides a method for calculating the bubble initiation temperature of an oil-paper system, including:

[0008] Collect the operating state parameters of an in-service transformer, and perform molecular simulation calculations based on the operating state parameters to obtain the micro-water aggregation rate at the oil-paper interface of the insulating oil-paper system;

[0009] Guide the flow rate of liquid water in the oil-paper system finite element model into the insulating paper finite element model through the micro-water aggregation rate, and calculate the bubble initiation temperature of the oil-paper system through the oil-paper system finite element model.

[0010] Optionally, the operating state parameters include the water content in the oil, the oil temperature, and the abnormal temperature rise time; the performing molecular simulation calculations based on the operating state parameters to obtain the micro-water aggregation rate at the oil-paper interface of the insulating oil-paper system includes:

[0011] Construct a molecular simulation model, and perform constant-temperature and constant-volume simulation tests and constant-temperature and constant-pressure simulation tests respectively using the molecular simulation model under a preset multi-coupled physical field to obtain the relationship between the number of hydrogen bonds and temperature changes;

[0012] Obtain the relationship between the number of water molecules and temperature changes based on the relationship between the number of hydrogen bonds and temperature changes, and further obtain the relationship between the mass of liquid water and temperature changes;

[0013] Obtain the micro-water aggregation rate relationship through the relationship between the mass of liquid water and temperature changes;

[0014] Substitute the oil temperature and the abnormal temperature rise time into the micro-water aggregation rate relationship to calculate the micro-water aggregation rate at the oil-paper interface of the insulating oil-paper system.

[0015] Optionally, the micro-water aggregation rate relationship is:

[0016]

[0017] In the formula, V 水 is the micro-water aggregation rate; m 水 is the mass of water in the macroscopic unit volume; M is the molar mass of water; N A is the Avogadro constant; N is the number of hydrogen bonds in the microscopic unit volume; k and C are fitting coefficients; V is the multiple of the microscopic unit volume to the macroscopic unit volume; is the density of water; t is the abnormal temperature rise time of the transformer.

[0018] Optionally, the constructing the molecular simulation model includes:

[0019] Construct insulating paper models and insulating oil models with different water contents;

[0020] Combine the insulation paper model and the insulating oil model to obtain an oil-paper insulation composite medium model, and perform geometric optimization on the oil-paper insulation composite medium model;

[0021] Perform energy cycle annealing on the optimized oil-paper insulation composite medium model to obtain a molecular simulation model.

[0022] Optionally, guide the flow rate of liquid water in the oil-paper system finite element model into the insulation paper finite element model through the micro-water aggregation rate, and calculate the bubble inception temperature of the oil-paper system in the transformer in the current state through the oil-paper system finite element model, including:

[0023] Construct a geometric model in finite element software;

[0024] Perform mesh division on the geometric model, and set the left side as the velocity inlet and the right side as the pressure outlet; wherein, the left half of the geometric model is a porous medium region, and the insulating oil fills the entire region of the geometric model;

[0025] Select the VOF model for multiphase flow, turn on the energy equation, set the viscosity to laminar flow, set the phase change of water to water vapor as the evaporation-condensation model, and set the relevant physical property parameters of the material and the insulation paper;

[0026] Set the permeability, viscous resistance, and inertial resistance coefficient according to the actual permeability, viscous resistance, and inertial resistance coefficient of the insulation paper, set the porous medium region as a heat source, and make corresponding settings according to the temperature rise power of the transformer;

[0027] When setting the boundary conditions, set the inlet as the velocity inlet, set the temperature of the liquid water at the inlet as the preset temperature, and set the velocity as the micro-water aggregation rate at the preset temperature to obtain the oil-paper system finite element model;

[0028] Solve through the oil-paper system finite element model to obtain the bubble inception temperature of the oil-paper system in the transformer in the current state.

[0029] The second aspect of the present application provides a device for calculating the bubble inception temperature of an oil-paper system, including:

[0030] A data acquisition unit for acquiring the operating state parameters during the operation of an in-service transformer;

[0031] A molecular simulation unit for performing molecular simulation calculations according to the operating state parameters to obtain the micro-water aggregation rate of water molecules at the oil-paper interface of the oil-paper insulation system;

[0032] A calculation unit for guiding the flow rate of liquid water in the oil-paper system finite element model into the insulation paper finite element model through the micro-water aggregation rate, and calculating the bubble inception temperature of the oil-paper system through the oil-paper system finite element model.

[0033] Optionally, the operating state parameters include water content in oil, oil temperature, and abnormal temperature rise time;

[0034] The molecular simulation unit is specifically configured to construct a molecular simulation model, and perform constant-temperature and constant-volume simulation tests and constant-temperature and constant-pressure simulation tests respectively using the molecular simulation model under a preset multi-coupled physical field to obtain the relationship between the number of hydrogen bonds and temperature changes;

[0035] Obtain the relationship between the number of water molecules and temperature changes according to the relationship between the number of hydrogen bonds and temperature changes, and further obtain the relationship between the mass of liquid water and temperature changes;

[0036] Obtain the micro-water aggregation rate relationship formula through the relationship between the mass of liquid water and temperature changes;

[0037] Substitute the oil temperature and the abnormal temperature rise time into the micro-water aggregation rate relationship formula to calculate the micro-water aggregation rate at the oil-paper interface of the insulating oil-paper system.

[0038] Optionally, the micro-water aggregation rate relationship formula is:

[0039]

[0040] In the formula, V 水 is the micro-water aggregation rate; m 水 is the mass of water in the macroscopic unit volume; M is the molar mass of water; N A is the Avogadro constant; N is the number of hydrogen bonds in the microscopic unit volume; k and C are fitting coefficients; V is the multiple of the microscopic unit volume to the macroscopic unit volume; is the density of water; t is the abnormal temperature rise time of the transformer.

[0041] The third aspect of the present application provides an electronic device, which includes a processor and a memory;

[0042] The memory is used to store program codes and transmit the program codes to the processor;

[0043] The processor is used to execute the bubble initiation temperature calculation method of any one of the oil-paper systems described in the first aspect according to the instructions in the program code.

[0044] The fourth aspect of the present application provides a computer-readable storage medium, which is characterized in that the computer-readable storage medium is used to store program codes, and when the program codes are executed by a processor, the bubble initiation temperature calculation method of any one of the oil-paper systems described in the first aspect is implemented.

[0045] It can be seen from the above technical solutions that the present application has the following advantages:

[0046] The method for calculating the bubble initiation temperature of the oil-paper system provided by this application uses a molecular simulation model to simulate the diffusion and aggregation behaviors of water molecules at the microscopic level under multiple fields, and extracts characteristic microscopic parameters, thereby guiding the establishment of a calculation model for the bubble escape of the oil-paper system in a related finite element simulation model, realizing the temperature prediction of the insulating oil-paper system with any water content, saving a large amount of costs, improving efficiency and accuracy, and contributing to promoting the digital transformation of the assessment and detection of the operating status of power equipment, replacing traditional tests with digital measurement methods. Description of the Drawings

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0048] Figure 1 A flowchart of a method for calculating the bubble initiation temperature of an oil-paper system provided by an embodiment of this application;

[0049] Figure 2 The moisture balance curve diagram provided by an embodiment of this application;

[0050] Figure 3 The basic composition components and proportions of the naphthenic oil provided by an embodiment of this application;

[0051] Figure 4 The basic structure diagram of cellulose provided by an embodiment of this application;

[0052] Figure 5 The schematic diagram of the change of hydrogen bonds per unit volume with temperature provided by an embodiment of this application;

[0053] Figure 6 The schematic diagram of the porous structure of cellulose provided by an embodiment of this application;

[0054] Figure 7 The schematic diagram of the multi-layer adsorption of water molecules on cellulose provided by an embodiment of this application;

[0055] Figure 8 The schematic diagram of the geometric model provided by an embodiment of this application;

[0056] Figure 9 The bubble initiation temperature diagram of the oil-paper interface provided by an embodiment of this application;

[0057] Figure 10It is a schematic structural diagram of a device for calculating the bubble initiation temperature of an oil-paper system provided by an embodiment of the present application. Detailed implementation manners

[0058] In order to enable those skilled in the art to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the 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 of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0059] For ease of understanding, please refer to Figure 1 , an embodiment of the present application provides a method for calculating the bubble initiation temperature of an oil-paper system, including:

[0060] Step 110: Collect the operating state parameters during the operation of an in-service transformer, and perform molecular simulation calculations based on the operating state parameters to obtain the micro-water aggregation rate of water molecules at the oil-paper interface of the insulating oil-paper system.

[0061] The operating state parameters of the in-service transformer can be monitored by an operating state parameter extractor installed inside the in-service power transformer. The operating state parameter extractor includes at least functions such as extracting the water content in the oil, the oil temperature, and the abnormal temperature rise time. The operating state parameters include the water content in the oil, the oil temperature, and the abnormal temperature rise time. Measuring the water content in the oil is used to obtain the water content in the insulating paper through the Norris curve (moisture equilibrium curve) as shown in Figure 2 to provide a basis for molecular modeling of insulating paper with different water contents.

[0062] Taking the extracted water content, oil temperature, abnormal temperature rise time and other information as the input of the molecular simulation model, and then obtaining the micro-water aggregation rate of water molecules at the oil-paper interface of the insulating oil-paper system through molecular simulation calculations. Specifically:

[0063] Construct a molecular simulation model, and perform constant temperature and constant volume simulation tests and constant temperature and constant pressure simulation tests respectively using the molecular simulation model under a preset multi-coupled physical field to obtain the relationship between the number of hydrogen bonds and temperature changes;

[0064] Obtain the relationship between the number of water molecules and temperature changes based on the relationship between the number of hydrogen bonds and temperature changes, and then obtain the relationship between the mass of liquid water and temperature changes;

[0065] Obtain the micro-water aggregation rate relationship formula through the relationship between the mass of liquid water and temperature changes;

[0066] Substitute the oil temperature and the abnormal temperature rise time into the micro-water aggregation rate relation formula to calculate the micro-water aggregation rate at the oil-paper interface of the insulating oil-paper system.

[0067] First, construct insulating paper models and insulating oil models with different water contents. The process of constructing the insulating oil model is as follows:

[0068] The construction of the insulating oil model is based on No. 25 Karamay transformer oil, and the basic composition components and proportions of naphthenic oil given Figure 3 are used to construct the insulating oil model. The amount of oil molecules should be large enough to dissolve a small amount of water molecules. Moreover, transformer oil is a complex colloidal stable system composed of various hydrocarbon and non-hydrocarbon compounds. In order to more comprehensively reflect its physical and chemical properties, it is necessary to expand the molecular scale of the oil model. For this purpose, an insulating oil model with an atomic scale of 105 is established in this application. First, establish chain hydrocarbon molecules, monocyclic alkane molecules, bicyclic alkane molecules, tricyclic alkane molecules, tetracyclic alkanes, and total monocyclic aromatic hydrocarbons respectively, and distribute them according to the Figure 3 proportions in 3 to construct the insulating oil model. The size of the insulating oil model is (11.5×11.5×7) nm

[0069] The process of constructing the insulating paper model is as follows:

[0070] Select cellulose chains with DP of 5, 6, and 7 as a basic unit. As shown in Figure 4 , select a certain number of water molecules according to the specific mass ratio of water molecules and cellulose in insulating paper with different water contents, so as to construct cellulose amorphous regions with different initial water contents. The mass ratio of the cellulose model to the insulating oil model is 1:10, which is close to the actual operating conditions of the transformer. Since the molecular weight scale of the insulating oil model has been determined, the molecular weight scale of the cellulose model can be determined through the mass ratio. It contains 30 basic units and forms a cubic amorphous polymer of (12.5×12.5×1.2) nm 3 , with a total of about 10,000 atoms.

[0071] After constructing insulating paper models and insulating oil models with different water contents, then optimize the energy and structure of the insulating paper model and the insulating oil model to make the molecular system reach equilibrium. Then combine the insulating paper model and the insulating oil model to establish an oil-paper insulation composite medium model. The scale of the oil-paper insulation composite medium model is (12×12×12) nm 3 , and finally optimize the model structure and energy several times to minimize the energy of the oil-paper insulation composite medium model and make the oil-paper insulation molecular system in a stable state. The specific optimization process is as follows:

[0072] The oil-paper insulation composite medium model is a large model of 12nm * 12nm * 12nm, with the number of atoms in the order of 105, which can more comprehensively reflect the physical and chemical properties. Combine the two-phase model and perform geometric optimization at medium precision to make the oil-paper insulation composite medium model stable and the energy reach the lowest. Then, perform energy cycle annealing treatment no less than 50 times in the temperature range of 300K to 900K to keep the model stable and obtain the molecular simulation model.

[0073] Under the action of multi-coupled physical fields, perform kinetic simulations of constant temperature and constant volume simulation tests and constant temperature and constant pressure simulation tests on the molecular simulation model. During the simulation, collect the full trajectories of the dynamic operations of all atoms in the system every 1ps. The temperature control adopts the Andersen method, and the initial velocities of each molecule are sampled according to the Maxwell distribution. The Velocity Verlet leapfrog method is used to solve the Newton equation. In the solution of the non-bond interaction equation, the Van der waals interaction adopts the Atom Based method, and the electrostatic interaction adopts the Ewald method. Periodic boundary conditions (periodic boundary condition) are used throughout the simulation. The simulation work is all completed with the help of the Meterials Studio 4.0 molecular simulation software package, and the extraction of some data is completed by a self-written program. Collect and analyze the movement trajectories of water molecules in cellulose with different water contents during the calculation process, and the change in the number of hydrogen bonds per unit volume at the oil-paper interface with the increase in temperature. As Figure 5 shown, the relationship between the number of hydrogen bonds and temperature can be obtained. The relationship between the number of hydrogen bonds and temperature changes is as follows:

[0074]

[0075] In the formula, N is the number of hydrogen bonds; k and C are fitting coefficients; is the function of the temperature T in the transformer changing with time, and this function is determined by the relationship between the measured oil temperature and the abnormal temperature rise time of the transformer.

[0076] Each water molecule in liquid water usually has 4 hydrogen bonds. From this, the number of corresponding water molecules per unit volume can be obtained, and then the law of the number of water molecules in the macroscopic unit volume changing with temperature can be obtained. The relationship between the number of water molecules and temperature changes is as follows:

[0077]

[0078] In the formula, N 水 is the number of water molecules in the macroscopic unit volume (cm 3 ); N is the number of hydrogen bonds in the microscopic unit volume (nm 3 ); V is the multiple of the microscopic unit volume to the macroscopic unit volume.

[0079] Based on the relationship between the number of water molecules and temperature change, the relationship between the mass of liquid water per unit volume and temperature change can be obtained:

[0080]

[0081] In the formula, m 水 is the mass of water in the macroscopic unit volume, N A is the Avogadro constant, and M is the molar mass of water.

[0082] Through the relationship between the mass of liquid water and temperature change, the micro water aggregation rate relationship formula can be obtained:

[0083]

[0084] In the formula, V 水 is the micro water aggregation rate; is the density of water; t is the abnormal temperature rise time.

[0085] Substitute the relationship f(t) between the oil temperature and the abnormal temperature rise time into the above micro water aggregation rate relationship formula, and then take the time derivative of this relationship formula to obtain the micro water aggregation rate at the oil-paper interface of the oil-paper system in the insulating oil-paper system, and thus obtain the rate of the corresponding liquid water entering the following finite element model of the oil-paper system.

[0086] Step 120: Guide the flow rate of liquid water entering the finite element model of insulating paper in the finite element model of the oil-paper system through the micro water aggregation rate, and calculate the bubble initiation temperature of the oil-paper system in the current state transformer through the finite element model of the oil-paper system;

[0087] The actual situation of bubble generation in the oil-paper system is as follows: Please refer to Figure 6 and Figure 7 , there are many holes between cellulose fibers. Water molecules are adsorbed on cellulose in insulating paper and separated from cellulose when heated. The water molecules separated from cellulose turn into water vapor when heated, diffuse in the holes of cellulose, aggregate to form bubbles, and finally break away from the insulating paper and enter the oil.

[0088] First, establish a geometric model in the finite element software according to the above actual situation. The geometric model can refer to Figure 8 , Figure 8 is a planar graph of 10mm * 10mm. The left half is the insulating paper area, and the insulating oil fills the entire area;

[0089] Secondly, mesh the geometric model: the mesh accuracy can be 0.05 mm, set the left side as the velocity inlet, the right side as the pressure outlet, the left side as the porous medium region, and the insulating oil fills the entire region; in this application, the insulating paper is equivalent to a porous medium to equivalent the influence of cellulose in the insulating paper on the flow of water and the generation of bubbles;

[0090] Then, set the solution conditions: select the VOF model for multiphase flow, turn on the energy equation, and set the viscosity to laminar flow; set the evaporation and condensation model for the water phase to become water vapor; set the default physical properties of liquid water, water vapor, and oil in fluent for the materials; and set the relevant physical properties of the insulating paper;

[0091] Set the permeability, viscous resistance, and inertial resistance coefficients of the porous medium model according to the actual permeability, viscous resistance, and inertial resistance coefficients of the insulating paper, set the porous medium region as the heat source, and make corresponding settings according to the temperature rise power of the transformer;

[0092] When setting the boundary conditions, set the inlet as the velocity inlet, the temperature of the liquid water at the inlet can be set to 373 K, and the velocity is set to the rate of water accumulation at a temperature of 373 K, that is ;

[0093] Construct a finite element model of the oil-paper system through the above process; when initializing the finite element model of the oil-paper system, fill the region of the porous medium and the oil domain with insulating oil, and the temperature is 373 K;

[0094] Finally, solve through the finite element model of the oil-paper system to obtain the bubble initiation temperature of the corresponding oil-paper interface, which can be referred to Figure 9 . This application simplifies the precipitation of moisture from the insulating paper into bubbles into three parts. The first part is to use molecular simulation to calculate the desorption and diffusion of water molecules from cellulose to form liquid water. The second part is to use finite element simulation to model cellulose as a porous medium, and the moisture enters the porous medium at a certain rate according to the desorption rate of water molecules obtained from molecular simulation. The third part is that the liquid water forms bubbles when heated during the process of passing through the porous medium. This application uses molecular simulation to guide the establishment of the finite element simulation model, and uses the desorption rate of water molecules calculated by molecular simulation to guide the rate of liquid water in the finite element model, saving a large amount of costs and improving efficiency. The bubble initiation temperature calculation method in this application is not only effective for traditional kraft insulating paper and mineral oil, but also effective for different types of insulating paper and insulating oil. The difference lies in the modeling of the initial oil and paper models and the correction of experimental data, but the overall idea is the same.

[0095] The method for calculating the bubble initiation temperature of the oil-paper system provided by this application uses a molecular simulation model to simulate the diffusion and aggregation behaviors of water molecules at the microscopic level under multiple fields, and extracts characteristic microscopic parameters, thereby guiding the establishment of a calculation model for the bubble escape of the oil-paper system in a related finite element simulation model, realizing the temperature prediction of the insulating oil-paper system with any moisture content, saving a large amount of costs, improving efficiency and accuracy, and contributing to promoting the digital transformation of the assessment and detection of the operating status of power equipment, replacing traditional tests with digital measurement methods.

[0096] Please refer to Figure 10 , this application embodiment also provides a device for calculating the bubble initiation temperature of an oil-paper system, including:

[0097] A data acquisition unit 210, configured to acquire the operating status parameters during the operation of an in-service transformer;

[0098] A molecular simulation unit 220, configured to perform molecular simulation calculations based on the operating status parameters to obtain the micro-water aggregation rate at the oil-paper interface of the insulating oil-paper system;

[0099] A calculation unit 230, configured to guide the flow rate of liquid water in the finite element model of the oil-paper system into the finite element model of the insulating paper through the micro-water aggregation rate, and calculate the bubble initiation temperature of the oil-paper system through the finite element model of the oil-paper system.

[0100] Furthermore, the operating status parameters include the water content in the oil, the oil temperature, and the abnormal temperature rise time;

[0101] The molecular simulation unit 220 is specifically configured to construct a molecular simulation model, and perform constant-temperature and constant-volume simulation tests and constant-temperature and constant-pressure simulation tests respectively using the molecular simulation model under a preset multi-coupled physical field to obtain the relationship between the number of hydrogen bonds and the temperature change;

[0102] Obtain the relationship between the number of water molecules and the temperature change according to the relationship between the number of hydrogen bonds and the temperature change, and further obtain the relationship between the mass of liquid water and the temperature change;

[0103] Obtain the micro-water aggregation rate relationship formula through the relationship between the mass of liquid water and the temperature change;

[0104] Substitute the oil temperature and the abnormal temperature rise time into the micro-water aggregation rate relationship formula to calculate the micro-water aggregation rate at the oil-paper interface of the insulating oil-paper system.

[0105] Furthermore, the micro-water aggregation rate relationship formula is:

[0106]

[0107] In the formula, V 水 is the micro-water aggregation rate; m 水is the mass of water in the macroscopic unit volume; M is the molar mass of water; N A is the Avogadro constant; N is the number of hydrogen bonds in the microscopic unit volume; k, n, and C are fitting coefficients; V is the multiple of the microscopic unit volume to the macroscopic unit volume; is the density of water; t is the abnormal temperature rise time.

[0108] Furthermore, the calculation unit 230 is specifically used to construct a geometric model in finite element software;

[0109] mesh the geometric model, and set the left side as the velocity inlet and the right side as the pressure outlet; among them, the left side is the porous medium area and the left side is the insulating oil area;

[0110] For multiphase flow, select the VOF model, turn on the energy equation, set the viscosity to laminar flow, set the transformation of water phase into water vapor as the evaporation condensation model, and set the relevant physical property parameters of the material and insulating paper;

[0111] Set the permeability, viscous resistance, and inertial resistance coefficients according to the actual permeability, viscous resistance, and inertial resistance coefficients of the insulating paper, set the porous medium area as the heat source, and make corresponding settings according to the temperature rise power of the transformer;

[0112] When setting the boundary conditions, set the inlet as the velocity inlet, set the temperature of the liquid water at the inlet as the preset temperature, and set the velocity as the micro-water aggregation rate at the preset temperature to obtain the finite element model of the oil-paper system;

[0113] Solve through the finite element model of the oil-paper system to obtain the bubble initiation temperature of the oil-paper system in the transformer in the current state.

[0114] This application uses a molecular simulation model to simulate the diffusion and aggregation behavior of water molecules at the microscopic level under multiple fields, and extracts characteristic microscopic parameters, thereby guiding the establishment of a calculation model for the bubble escape of the oil-paper system in the relevant finite element simulation model, realizing the temperature prediction of the insulating oil-paper system with any water content, saving a large amount of costs, improving efficiency and accuracy, and contributing to promoting the digital transformation of the assessment and detection of the operating state of power equipment, replacing traditional tests with digital measurement methods.

[0115] This application embodiment also provides an electronic device, characterized in that the device includes a processor and a memory;

[0116] The memory is used to store program code and transmit the program code to the processor;

[0117] The processor is used to execute the method for calculating the bubble initiation temperature of the oil-paper system in the foregoing method embodiment according to the instructions in the program code.

[0118] The embodiment of the present application also provides a computer-readable storage medium, which is characterized in that the computer-readable storage medium is used to store program codes, and when the program codes are executed by a processor, the method for calculating the bubble initiation temperature of the oil-paper system in the foregoing method embodiment is implemented.

[0119] Those skilled in the art can clearly understand that for the convenience and conciseness of description, the specific working processes of the above-described devices and units can refer to the corresponding processes in the foregoing method embodiments, and will not be described herein again.

[0120] The terms "first", "second", "third", "fourth", etc. (if any) in the specification of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that comprises a series of steps or units does not have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0121] It should be understood that in the present application, "at least one (item)" means one or more, and "a plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: only A exists, only B exists, and both A and B exist at the same time. Among them, A and B can be singular or plural. The character " / " generally means that the associated objects before and after are in an "or" relationship. "At least one of the following (one)" or a similar expression means any combination of these items, including any combination of single item (one) or plural items (one). For example, at least one of a, b, or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a, b, and c", where a, b, and c can be single or multiple.

[0122] In several embodiments provided by the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of the units is only a logical function division, and there may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection to each other can be through some interfaces, and the indirect coupling or communication connection of the devices or units can be in an electrical, mechanical or other form.

[0123] The unit described as a separation component may or may not be physically separated. The component shown as a unit may or may not be a physical unit, that is, it may be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0124] In addition, each functional unit in various embodiments of the present application may be integrated in a processing unit, or each unit may exist physically alone, or two or more units may be integrated in one unit. The above integrated unit may be implemented in the form of hardware or in the form of a software functional unit.

[0125] If the above integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present application. The aforementioned storage medium includes: USB flash drives, mobile hard disks, read-only memories (English full name: Read-Only Memory, English abbreviation: ROM), random access memories (English full name: Random Access Memory, English abbreviation: RAM), magnetic disks or optical discs and other media that can store program codes.

[0126] As described above, the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of various embodiments of the present application.

Claims

1. A method for calculating the bubble starting temperature of an oil-paper system, characterized in that: include: Collecting the operating state parameters of the in-service transformer during operation, performing molecular simulation calculations based on the operating state parameters, and obtaining the micro-water aggregation rate of water molecules at the oil-paper interface of the insulating oil-paper system; The flow rate of liquid water in the oil-paper system finite element model entering the insulation paper finite element model is guided by the micro-water aggregation rate, and the bubble starting temperature of the oil-paper system is calculated by the oil-paper system finite element model.

2. The method for calculating the bubble starting temperature of the oil-paper system according to claim 1, characterized in that: The operating state parameters include water content in the oil, oil temperature and abnormal temperature rise time; the molecular simulation calculation based on the operating state parameters to obtain the micro-water aggregation rate of water molecules at the oil-paper interface of the insulating oil-paper system includes: Constructing a molecular simulation model, and using the molecular simulation model to perform a constant temperature and constant volume simulation test and a constant temperature and constant pressure simulation test under a preset multi-coupled physical field to obtain the relationship between the number of hydrogen bonds and the temperature change; Obtaining the relationship between the number of water molecules and the temperature change according to the relationship between the number of hydrogen bonds and the temperature change, and then obtaining the relationship between the mass of liquid water and the temperature change; The relationship between the mass of liquid water and the temperature change is used to obtain the relationship between the rate of micro-water aggregation; The oil temperature and the abnormal temperature rise time are substituted into the micro-water aggregation rate relationship to calculate the micro-water aggregation rate of water molecules at the oil-paper interface of the insulating oil-paper system.

3. The method for calculating the bubble initiation temperature of the oil-paper system according to claim 2, characterized in that: The micro-water aggregation rate relationship is: Where V 水 is the micro-water aggregation rate; m 水 is the mass of water in a macroscopic unit volume; M is the molar mass of water; N A is Avogadro's constant; N is the number of hydrogen bonds in a microscopic unit volume; k and C are fitting coefficients; V is the multiple of the microscopic unit volume to the macroscopic unit volume; is the density of water; t is the time when the transformer abnormal temperature rises.

4. The method for calculating the bubble starting temperature of the oil-paper system according to claim 2, characterized in that: The molecular simulation model is constructed, comprising: Construct insulation paper models and insulation oil models with different moisture contents; Combining the insulating paper model and the insulating oil model to obtain an oil-paper insulation composite medium model, and performing geometric optimization on the oil-paper insulation composite medium model; The optimized oil-paper insulation composite dielectric model was subjected to energy cycle annealing to obtain a molecular simulation model.

5. The method for calculating the bubble initiation temperature of the oil-paper system according to claim 1, characterized in that: The flow rate of liquid water in the oil-paper system finite element model entering the insulation paper finite element model is guided by the micro-water aggregation rate, and the bubble starting temperature of the oil-paper system in the transformer in the current state is calculated by the oil-paper system finite element model, including: Construct geometric models in finite element software; The geometric model is meshed, and the left side is set as the velocity inlet and the right side is set as the pressure outlet; wherein the left half of the geometric model is the porous medium area, and the insulating oil fills the entire area of ​​the geometric model; Select the VOF model for multiphase flow, open the energy equation, set the viscosity to laminar flow, set the water phase to water vapor as the evaporation-condensation model, and set the relevant physical properties of the material and insulation paper; The permeability, viscous resistance and inertial resistance coefficient are set according to the actual permeability, viscous resistance and inertial resistance coefficient of the insulating paper, the porous medium area is set as a heating source, and the temperature rise power of the transformer is set accordingly; When setting boundary conditions, the inlet is set as the velocity inlet, the liquid water temperature at the inlet is set as the preset temperature, and the velocity is set as the micro-water aggregation rate at the preset temperature, and the finite element model of the oil-paper system is obtained; The bubble initiation temperature of the oil-paper system in the transformer in the current state is obtained by solving the oil-paper system finite element model.

6. A bubble starting temperature calculation device for an oil-paper system, characterized in that: include: A data acquisition unit, used to collect operating status parameters of the in-service transformer during operation; A molecular simulation unit, used for performing molecular simulation calculation according to the operating state parameters to obtain a micro-water aggregation rate of water molecules at the oil-paper interface of the insulating oil-paper system; The calculation unit is used to guide the flow rate of liquid water in the oil-paper system finite element model into the insulation paper finite element model through the micro-water aggregation rate, and calculate the bubble starting temperature of the oil-paper system through the oil-paper system finite element model.

7. The bubble initiation temperature calculation device for the oil-paper system according to claim 6, characterized in that: The operating status parameters include water content in the oil, oil temperature, and abnormal temperature rise time; The molecular simulation unit is specifically used to construct a molecular simulation model, and use the molecular simulation model to perform a constant temperature and constant volume simulation test and a constant temperature and constant pressure simulation test under a preset multi-coupled physical field to obtain the relationship between the number of hydrogen bonds and the temperature change; Obtaining the relationship between the number of water molecules and the temperature change according to the relationship between the number of hydrogen bonds and the temperature change, and then obtaining the relationship between the mass of liquid water and the temperature change; The relationship between the mass of liquid water and the temperature change is used to obtain the relationship between the rate of micro-water aggregation; The oil temperature and the abnormal temperature rise time are substituted into the micro-water aggregation rate relationship to calculate the micro-water aggregation rate of water molecules at the oil-paper interface of the insulating oil-paper system.

8. The bubble initiation temperature calculation device for the oil-paper system according to claim 7, characterized in that: The micro-water aggregation rate relationship is: Where V 水 is the micro-water aggregation rate; m 水 is the mass of water in a macroscopic unit volume; M is the molar mass of water; N A is Avogadro's constant; N is the number of hydrogen bonds in a microscopic unit volume; k and C are fitting coefficients; V is the multiple of the microscopic unit volume to the macroscopic unit volume; is the density of water; t is the time when the transformer abnormal temperature rises.

9. An electronic device, characterized in that: The device comprises a processor and a memory; The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the bubble starting temperature calculation method of the oil-paper system according to any one of claims 1-5 according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store program codes, and when the program codes are executed by a processor, the method for calculating the bubble starting temperature of the oil-paper system according to any one of claims 1 to 5 is implemented.

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