A method for simulating the thermal aging of transformer insulating paper

Abstract

The invention proposes a method for simulating thermal aging of transformer insulating oil paper, which relates to the field of network detection technology, and comprises: using molecular dynamics simulation software to respectively establish an oil molecule box model and an insulating paper molecule box model of the transformer, then relaxing and balancing the models, and combining them into a layered structure model through layered arrangement, and then obtaining an oil-paper model through multiple relaxations and balancing optimizations, simulating the model using a molecular dynamics simulation method based on a ReaxFF force field to obtain trajectory molecules, and then monitoring and statistics are performed to obtain the system state at each moment of the pyrolysis process, and a change trend diagram is drawn to obtain the simulation result; the invention simulates a long-term aging process with the help of molecular simulation software, which can lay a judgment foundation for the diagnosis of the operating state of the transformer equipment and provide a reliable basis for the stable operation of the equipment, and at the same time provides the basic reaction mechanism for the staff, reduces the time cost, and realizes the guidance of the maintenance and repair of the transformer.

Description

Technical Field

[0001] The invention relates to the technical field of transformers, and in particular to a method for simulating thermal aging of transformer insulating oil paper. Background Art

[0002] Power transformers are an important part of the power system. They play an important role in connecting voltage levels, converting voltage and current, and realizing the transmission and distribution of electric energy. Their reliability directly affects the safe operation of the power system. In addition, during the operation of the transformer, the oil-paper insulation will gradually deteriorate under the combined effects of electrical, thermal, mechanical and environmental factors, causing the mechanical strength or insulation performance of the insulation system to decrease. As an important large-scale power supply equipment, the maintenance cost and difficulty of power transformers are quite large, and the social impact and economic losses caused by their failures are also immeasurable. Therefore, simulating the thermal aging process and overheating failure process during the operation of the transformer is of great guiding significance for the maintenance of the transformer. Summary of the invention

[0003] The purpose of the present invention is to provide a method for simulating thermal aging of transformer insulating oil-paper, which can reflect the basic mechanism and reduce the time cost by simulating the long-term aging process with the help of molecular simulation software, infer the decomposition path of thermal aging of oil-paper molecules, and guide the maintenance and repair of transformers.

[0004] The technical solution of the present invention is:

[0005] The present application provides a method for simulating thermal aging of transformer insulating oil paper, which comprises the following steps:

[0006] S1. Use molecular dynamics simulation software to establish oil molecular box models and insulating paper molecular box models of the transformer respectively;

[0007] S2, relax and balance the oil molecule box model and the insulating paper molecule box model respectively;

[0008] S3, combining the oil molecule box model and the insulating paper molecule box model after relaxation and equilibrium optimization into a layered structure model through layered arrangement;

[0009] S4, performing multiple relaxation and equilibrium optimization on the layered structure model to obtain the oil-paper model;

[0010] S5, using the molecular dynamics simulation method based on the ReaxFF force field to perform molecular dynamics simulation on the oil-paper model to obtain trajectory molecules;

[0011] S6. Monitor and count the obtained trajectory molecules, obtain the system state at each moment of the pyrolysis process, draw a change trend graph, and obtain the simulation results.

[0012] Among them, relaxation and equilibrium optimization can make the system density close to the real value.

[0013] Furthermore, step S1 includes: using molecular dynamics simulation software to draw the molecular configuration of the insulating oil component and the molecular configuration of the insulating paper component, and establishing a transformer oil molecular box model according to the molecular configuration of the insulating oil component, and establishing a transformer insulating paper molecular box model according to the molecular configuration of the insulating paper component.

[0014] Furthermore, in step S1, before establishing the oil molecule box model and the insulating paper molecule box model of the transformer, the step also includes: geometric optimization and energy minimization of the insulating oil molecule monomers.

[0015] Furthermore, the above relaxation and equilibrium optimization include annealing, pressure increase and pressure decrease, and energy minimization processing.

[0016] Furthermore, in step S5, the calculation process of performing molecular dynamics simulation on the oil-paper model using the molecular dynamics simulation method based on the ReaxFF force field includes:

[0017] In the formula, is the total energy of the system, is the bond energy, For lone pair electrons, , is the over-coordination energy correction, is the bond angle energy, To punish energy, To reverse the energy, To connect energy, For hydrogen bonding, is the non-bonded van der Waals force, is the non-bonded Coulomb force, , is the corrected key order, is the key parameter, is the coordination number, is the equilibrium bond angle, is the interatomic bond angle, is a parameter used to describe the initial strength and stiffness of the bond, are parameters associated with the initial value of the key level, , , These are parameters used to adjust the shape of the key curve. It is a parameter used to indicate the slope or curvature of the interatomic interaction force at a specific bond length.

[0018] Compared with the prior art, the present invention has at least the following advantages or beneficial effects:

[0019] The invention discloses a method for simulating thermal aging of transformer insulating oil-paper. By establishing an oil-paper model and using a molecular dynamics simulation method based on a ReaxFF force field to perform molecular dynamics simulation on the oil-paper model, the cracking process of the oil-paper molecules can be accurately reflected. The small molecule product statistics of the cracking trajectory file obtained can be performed through a perl script, and the product generation situation in each time period can be drawn in detail. The cracking path of the oil-paper molecules can be inferred by combining with the observation of the cracking process, so as to obtain accurate aging test data, lay a judgment foundation for diagnosing the operating status of the transformer equipment, provide a reliable basis for the stable operation of the equipment, and provide the basic reaction mechanism for the staff, reduce the time cost, and guide the maintenance and repair of the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 This is a flow chart of a method for simulating thermal aging of transformer insulating oil paper according to Embodiment 1 of the present invention;

[0022] Figure 2 C of Example 2 of the present invention 20 H 42 Statistical graph of small gas molecules changing over time generated by the multi-molecule mixing model;

[0023] Figure 3 C of Example 2 of the present invention 20 H 34 Statistical graph of small gas molecules changing over time generated by the multi-molecule mixing model;

[0024] Figure 4 C of Example 2 of the present invention 20 H 42 Statistical graph of small gas molecules changing over time generated by the multi-molecule model;

[0025] Figure 5 This is a statistical graph of the change of small gas molecules over time generated by the PMIA multi-molecule mixing model with a polymerization degree of 2 according to Example 2 of the present invention;

[0026] Figure 6 A statistical graph showing the change of small gas molecules generated by the transformer insulating oil mixture model according to Example 2 of the present invention over time;

[0027] Figure 7 This is a statistical graph of the time-varying small gas molecules generated by the transformer insulating oil-paper layered mixing model of Example 2 of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0030] It should be noted that, in this article, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0031] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0032] Example 1

[0033] See also Figure 1 , Figure 1 Shown is a step diagram of a transformer insulating oil paper thermal aging simulation method provided in an embodiment of the present application.

[0034] The present application provides a method for simulating thermal aging of transformer insulation oil paper, which uses molecular dynamics simulation to study the entire process of thermal decomposition of transformer oil paper. The flow chart is as follows: Figure 1 As shown, the following steps are included:

[0035] S1. Use molecular dynamics simulation software to establish oil molecular box models and insulating paper molecular box models of the transformer respectively;

[0036] S2, relax and balance the oil molecule box model and the insulating paper molecule box model respectively;

[0037] S3, combining the oil molecule box model and the insulating paper molecule box model after relaxation and equilibrium optimization into a layered structure model through layered arrangement;

[0038] S4, performing multiple relaxation and equilibrium optimization on the layered structure model to obtain the oil-paper model;

[0039] S5, using the molecular dynamics simulation method based on the ReaxFF force field to perform molecular dynamics simulation on the oil-paper model to obtain trajectory molecules;

[0040] S6. Monitor and count the obtained trajectory molecules, obtain the system state at each moment of the pyrolysis process, draw a change trend graph, and obtain the simulation results.

[0041] It should be noted that the ReaxFF force field is the reaction force field; step S6 mainly uses the script software trajectory molecules to monitor and count, obtain the system state at each moment of the pyrolysis process, and then draw a trend chart of the reactants and products changing with the reaction time to obtain the final simulation result.

[0042] As a preferred implementation, step S1 includes: using molecular dynamics simulation software to draw the molecular configuration of the insulating oil component and the molecular configuration of the insulating paper component, and establishing a transformer oil molecular box model according to the molecular configuration of the insulating oil component, and establishing a transformer insulating paper molecular box model according to the molecular configuration of the insulating paper component.

[0043] As a preferred implementation, in step S1, before establishing the oil molecule box model and the insulating paper molecule box model of the transformer, the method further includes: geometrically optimizing and minimizing the energy of insulating oil molecule monomers.

[0044] As a preferred embodiment, the relaxation and equilibrium optimization include annealing, pressure increase and decrease, and energy minimization processing.

[0045] As a preferred embodiment, in step S5, the calculation process of performing molecular dynamics simulation on the oil-paper model using the molecular dynamics simulation method based on the ReaxFF force field includes:

[0046] In the formula, is the total energy of the system, is the bond energy, For lone pair electrons, , is the overcoordination energy correction, is the bond angle energy, To punish energy, To reverse the energy, To connect energy, For hydrogen bonding, is the non-bonded van der Waals force, is the non-bonded Coulomb force, , is the corrected key order, is the key parameter, is the coordination number, is the equilibrium bond angle, is the interatomic bond angle, is a parameter used to describe the initial strength and stiffness of the bond, are parameters associated with the initial value of the key level, , , These are parameters used to adjust the shape of the key curve. It is a parameter used to indicate the slope or curvature of the interatomic interaction force at a specific bond length.

[0047] It should be noted that the present invention relates to a simulation of thermal aging of transformer oil-paper insulation system, introduces a molecular scale simulation method of thermal aging of transformer oil-paper system under high temperature operation, establishes a microscopic model for describing transformer oil-paper structure, and aims to simulate the aging process of transformer in operation. First, a transformer oil molecule box model and an insulation paper molecule box model are respectively established by molecular dynamics simulation software, and after multiple energy minimization processes and pressure and pressure relaxation and temperature control processes, an appropriate model is finally obtained, and then the two box models are combined by layered arrangement, and multiple structural optimizations are also performed to obtain an oil-paper model. The simulation method based on the model is a molecular dynamics simulation based on the ReaxFF (reactive forcefield) force field, which is suitable for large systems and multi-atom structures. It is the mainstream force field of molecular chemical reactions and can well reflect the cracking process of oil-paper molecules. The ReaxFF force field is a reactive force field based on bond order (BO) proposed based on classical mechanics equations and drawing on other empirical force fields, and does not require pre-definition of the connectivity between atoms. One of the most basic assumptions of bond order definition is that there is a certain mathematical relationship between bond order and the distance between atoms, so the bond order of any two atoms can be directly obtained by the distance between atoms. In the ReaxFF force field, the concept of bond order is used to determine the connectivity between atoms to describe the breaking and formation of bonds; these functions can distinguish bonds, angles, dihedral angles, conjugation, Coulomb, van der Waals forces and adjustment terms, etc. The system potential function is described as the sum of each part, and the molecular dynamics simulation calculation of the oil paper model can be performed. Then, the script is used to perform small molecule product statistics on the calculated cleavage trajectory file, and the product generation situation in each time period is plotted, so as to infer the cleavage path of the oil paper molecule by combining the observation of the cleavage process.

[0048] Example 2

[0049] In Example 2 of the present invention, C 20 H 42 , C 20 H 34 , C 20 H 26 The three main types of molecules used as insulating oils are alkane molecules, cycloalkane molecules and aromatic hydrocarbon molecules. PMIA molecules with a degree of polymerization of 2 and a chemical formula of C 28 N4O4H 22 After drawing the molecular model, the geometric optimization and energy minimization were performed to obtain a stable monomer. After the monomer was used to build the system, a molecular dynamics simulation was performed. Finally, the molecular number statistics script was used in the secondary development program of the molecular dynamics simulation software to calculate the yield of the product over the simulation time.

[0050] Step 1: Construct the minimum monomer stability model of insulating oil and Nomex T410 (an aromatic polyamide high temperature resistant insulating paper product developed and produced by DuPont, USA);

[0051] First, according to the actual molecular structure, the amorphous unit cell drawing module in the molecular simulation software was used to draw the C 20 H 42 , C 20 H 34 , C 20 H 26 , C 28 N4O4H 22 monomer molecules; then use the smart algorithm (a stacking method that combines the steepest descent method and the conjugate gradient method, which can quickly approach the lowest energy point in the early stage of calculation and more accurately find the minimum value in the later stage) to minimize the energy and optimize the geometry of each monomer molecule to obtain the most stable molecular configuration.

[0052] Step 2: Construct stable amorphous structure periodic models of insulating oil single molecules, mixed molecules, Nomex T410 molecules, and oil-paper mixed molecules;

[0053] Using molecular simulation software, 30 molecular chains were packaged into a system to obtain a system containing 30 C 20 H 42 Amorphous periodic model of molecular chain, containing 30 C 20 H 34 Amorphous periodic model of molecular chain, containing 30 C 20 H 26 Amorphous periodic model of molecular chain, containing 30 C 28 N4O4H 22 Amorphous periodic model of molecular chain and 18 C 20 H 42 Molecule, 9 C 20 H 34 Molecule, 3 C 20 H 26 The insulating oil amorphous periodic model of the molecule. Then the insulating oil mixed molecular model and the Nomex T410 molecular model were layered to build the oil-paper mixed amorphous periodic model.

[0054] Step 3: Perform relaxation optimization and structural stabilization on the stable amorphous structure periodic models of the constructed insulating oil single molecule, mixed molecule, Nomex T410 molecule, and oil-paper mixed molecule; the specific steps are as follows:

[0055] First, each model was annealed: the canonical ensemble with constant N (number of particles) V (volume) T (temperature) and the Nose-Hoover heat bath method (introducing virtual heat bath particles to couple with the system to adjust the temperature of the system) were selected, and the model was heated and cooled 5 times, with the temperature controlled at 300k-800k and the temperature interval of 100k. Then, the model was pressurized and depressurized by 0.01GPa and 0.1MPa respectively using the N (number of particles) P (pressure) T (temperature) ensemble and the Berendsen pressure bath method (a method of adjusting the system volume through a virtual external pressure bath to maintain the target pressure) to make the density of the simulation system tend to normal. Finally, the model was minimized again to reduce its internal stress and keep it in a stable state. The final model density was stabilized at 0.81g / cm 3 , 0.88g / cm 3 , 0.95g / cm 3 , 1.17g / cm 3 , 0.83g / cm 3 , 1.00g / cm 3 .

[0056] Step 4: Perform dynamic molecular dynamics simulation on the irregular periodic model after relaxation to obtain a fragmentation trajectory file;

[0057] The irregular periodic models after relaxation were subjected to molecular dynamics simulation respectively. The force field selected was ReaxFF6.0 (a bond-level reaction force field that can simulate the changes in physical and chemical reactions). The charge option was selected to be distributed by the reaction force field. The N (number of particles) V (volume) T (temperature) canonical ensemble was selected. The temperature control method was the Nose-Hoover heat bath method. The temperature control parameters and thermodynamic equilibrium time were the default parameters. The temperature was set to 2400K, the step size was set to 0.25fs, and one frame was output every 1000 steps, for a total of 320 frames.

[0058] Step 5: Count the generation of small molecule products in the trajectory file;

[0059] Using the Perl language, program and analyze the trajectory file obtained in step 4, determine the bond length to be set to a minimum of 0.75 and a maximum of 1.15, analyze the product frame by frame, and output a table. Draw a curve of the product changing with the pyrolysis time, such as Figure 2-6 , infer the cracking paths of the reactants and the sources of the products.

[0060] Step 6: The decomposition path of transformer oil paper can be inferred by observing the cracking trajectory and product change curve;

[0061] Alkane molecules tend to first split the molecular chain in half, and then gradually decompose into various alkane and alkene gas molecules; when cycloalkane molecules are cracked, they tend to break the carbon chain first and then remove the benzene ring, gradually generating small molecule gases; aromatic hydrocarbon molecules tend to first crack the benzene ring, and then crack the carbon chain, gradually generating various alkane and alkene gas molecules. The main gas small molecules obtained after the decomposition of each substance are obtained according to the product change curve. PMIA molecules tend to first split the carbon chain in half, and then gradually crack into small molecule gases. It can be seen that hydrogen, methane, ethane, and ethylene are produced in a single insulating oil system, a single insulating paper system, and an insulating oil-paper composite system. In particular, a single insulating paper will produce a large amount of ammonia and a small amount of water, while an oil-paper composite system will produce a large amount of ammonia and water.

[0062] It is understood that the structure shown in the figure is only for illustration, and a method for simulating thermal aging of transformer insulating oil paper may also include more or fewer components than those shown in the figure, or have a different configuration than those shown in the figure. Each component shown in the figure may be implemented by hardware, software or a combination thereof.

[0063] In the embodiments provided in the present application, it should be understood that the disclosed method can also be implemented in other ways. The embodiments described above are merely schematic, for example, the flowchart or block diagram in the accompanying drawings shows the possible implementation architecture, functions and operations of the method and computer program product according to multiple embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or the flowchart, and the combination of the boxes in the block diagram and / or the flowchart can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0064] In addition, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0065] If the function is implemented in the form of a software function module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, and other media that can store program codes.

[0066] In summary, the embodiment of the present application provides a method for simulating thermal aging of transformer insulating oil-paper. By establishing an oil molecule box model and an insulating paper molecule box model of the transformer, and obtaining the oil-paper model through relaxation and equilibrium optimization, the molecular dynamics simulation method based on the ReaxFF force field is used to perform molecular dynamics simulation on the oil-paper model to obtain trajectory molecules. The product generation process during the aging process can be displayed through molecular simulation. Through product statistics, the decomposition path of thermal aging of oil-paper molecules can be inferred, and the source of small molecule gas can be obtained. The basic mechanism can be reflected and the time cost can be reduced. The decomposition path of thermal aging of oil-paper molecules can be inferred, thereby guiding the maintenance and repair of the transformer.

[0067] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0068] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential features of the present application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present application. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for simulating thermal aging of transformer insulating oil paper, characterized in that: The following steps are involved: S1. Use molecular dynamics simulation software to establish oil molecular box models and insulating paper molecular box models of the transformer respectively; S2, relax and balance the oil molecule box model and the insulating paper molecule box model respectively; S3, combining the oil molecule box model and the insulating paper molecule box model after relaxation and equilibrium optimization into a layered structure model through layered arrangement; S4, performing multiple relaxation and equilibrium optimization on the layered structure model to obtain the oil-paper model; S5. Perform molecular dynamics simulation on the oil-paper model using a molecular dynamics simulation method based on the ReaxFF force field to obtain trajectory molecules; wherein the calculation process of the molecular dynamics simulation includes: In the formula, is the total energy of the system, is the bond energy, is the energy of the lone pair electron, , is the over-coordination energy correction, is the bond angle energy, To punish energy, To reverse the energy, To connect energy, For hydrogen bonding, is the non-bonded van der Waals force, is the non-bonded Coulomb force, is the corrected key order, , , , , , , All are key parameters. is the coordination number, is the equilibrium bond angle, is the bond angle between atoms; S6. Monitor and count the obtained trajectory molecules, obtain the system state at each moment of the pyrolysis process, draw a change trend graph, and obtain the simulation results.

2. A transformer insulation oil paper thermal aging simulation method according to claim 1, characterized in that: Step S1 includes: using molecular dynamics simulation software to draw the molecular configuration of the insulating oil component and the molecular configuration of the insulating paper component, and establishing a transformer oil molecular box model according to the molecular configuration of the insulating oil component, and establishing a transformer insulating paper molecular box model according to the molecular configuration of the insulating paper component.

3. A transformer insulation oil paper thermal aging simulation method as claimed in claim 2, characterized in that: In step S1, before establishing the oil molecule box model and the insulating paper molecule box model of the transformer, the method further includes: geometric optimization and energy minimization of the insulating oil molecule monomers.

4. A transformer insulation oil paper thermal aging simulation method as claimed in claim 1, characterized in that: The relaxation and equilibrium optimization include annealing, pressure increase and pressure decrease, and energy minimization processing.

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