Method for acquiring diffusion coefficient of thermal cracking dissolved gas of insulating oil of current transformer

Abstract

The invention discloses a method and system for obtaining a diffusion coefficient of thermal cracking dissolved gas of insulating oil of a current transformer, and the method comprises the steps: constructing a molecular structure representing typical components of the insulating oil of an inverted oil-immersed current transformer, and carrying out the geometric optimization; constructing a first insulating oil model of the inverted current transformer; performing dynamic relaxation on the first insulating oil model to enable the first insulating oil model to reach a stable state; under different high-temperature conditions, reaction molecular dynamics simulation of insulating oil cracking is carried out, and a gas product of insulating oil thermal cracking is determined; constructing a second insulating oil model containing dissolved gas based on the gas product; performing dynamic relaxation on the second insulating oil model; performing dynamic simulation on the second insulating oil model, respectively applying different temperatures, and obtaining mean square displacement of any dissolved gas at different temperatures; and determining a diffusion coefficient curve of any dissolved gas in the insulating oil based on the mean square displacement of any dissolved gas at different temperatures.

Description

Technical Field

[0001] The present invention relates to the technical field of quantum chemical calculation and molecular dynamics simulation, and more specifically, to a method and system for obtaining the diffusion coefficient of dissolved gas in thermal decomposition of insulating oil of a current transformer. Background Art

[0002] In the stable operation of the power system, the inverted oil-immersed current transformer is a key device, and its status monitoring and fault diagnosis play a vital role. Especially during operation, the equipment is subjected to the combined effects of thermal, mechanical and electrical stresses, which cause thermal cracking of the insulating oil and the generation of dissolved gases. The accumulation of these gases not only accelerates the aging of the insulating material, but may also induce partial discharge or arc discharge. When the gas accumulates to a certain level, it may even cause the oil tank to explode. Therefore, accurate monitoring and prediction of the diffusion behavior of dissolved gases has become a key step in explosion protection and fault detection.

[0003] At present, the research on dissolved gas diffusion in inverted oil-immersed current transformers mainly focuses on empirical models and experimental methods. However, these traditional methods are often difficult to accurately predict the dynamic changes of gas diffusion under actual fault conditions. Therefore, a method is needed to obtain the diffusion coefficient of dissolved gas in thermal decomposition of current transformer insulating oil and establish a more accurate gas diffusion coefficient model. Summary of the invention

[0004] The present invention provides a method and system for obtaining the diffusion coefficient of dissolved gas by thermal decomposition of insulating oil of a current transformer, so as to solve the problem of how to efficiently obtain the diffusion coefficient of dissolved gas by thermal decomposition of insulating oil.

[0005] In order to solve the above problem, according to one aspect of the present invention, a method for obtaining the diffusion coefficient of thermal decomposition dissolved gas of current transformer insulating oil is provided, the method comprising:

[0006] Construct the molecular structure representing the typical components of the insulating oil of the inverted oil-immersed current transformer, and geometrically optimize the molecular structure of the typical components so that the molecular energy is in a stable state;

[0007] According to the composition ratio of insulating oil, the first insulating oil model of inverted current transformer is constructed by using periodic boundary conditions as constraints.

[0008] Performing dynamic relaxation on the first insulating oil model so that the first insulating oil model reaches a stable state;

[0009] Under different high temperature conditions, molecular dynamics simulation of the reaction of insulating oil cracking is performed based on the first insulating oil model to observe typical components of gas products of thermal cracking of insulating oil;

[0010] constructing a second insulating oil model containing dissolved gas based on the gas product;

[0011] Performing dynamic relaxation on the second insulating oil model so that the second insulating oil model reaches a stable state;

[0012] Performing dynamic simulation on the second insulating oil model, applying different temperatures respectively, and obtaining the mean square displacement of any dissolved gas at different temperatures;

[0013] For any dissolved gas, a diffusion coefficient curve of the any dissolved gas in the insulating oil is determined based on the mean square displacement of the any dissolved gas at different temperatures.

[0014] Preferably, the method uses a ReaxFF reaction force field to perform reaction molecular dynamics simulation, and the system energy contribution distribution of the ReaxFF reaction force field is:

[0015] E systeam =E bond +E tors +E over +E under +E lp +E val +E pen +E coa +E vdWaals +E coulomb +E specific ,

[0016] Among them, E bond is a function of the distance between atoms, representing the bond energy between atoms; E tors Represents the energy of dihedral angle torsion; E over and E under They represent the over-coordination energy correction and under-coordination energy correction based on the atomic valence rule respectively; E lp Represents the energy of lone pair electrons; E val , E pen and E coa They represent the energy of covalent bond angle bending, the penalty energy of one atom sharing two double bonds to destabilize the system, and the energy of three-point conjugation. vdWaals and E coulomb They represent the energy contributed by the van der Waals interaction and electrostatic interaction between all non-neighboring atoms without considering the bond order BO; E specific Represents the special energy contribution to a specific molecular system.

[0017] Preferably, the first insulating oil model comprises: 20 H 42 、Bicycloalkanes C 20 H 38, bicyclic aromatic hydrocarbons and heterocyclic compounds C3H4O; in the molecular dynamics simulation of the reaction of insulating oil cracking, the alkane C 20 H 42 The decomposition of the alkane C 20 H 42 The first decomposition path is:

[0018]

[0019] Among them, a0+a1+...+a n-2 =∑a i =1(i=0,1,...,n-2), a i is the coefficient of each type of product, indicating the relative amount of each product generated in the reaction; n is the total number of product types;

[0020] Alkanes C 20 H 42 The secondary thermal decomposition path above 300°C is:

[0021]

[0022] Among them, b1+2(b2+b3+b4)+3(b5+b6)=20,4b1+6b2+4b3=2b4+8b5+6b6+2b7=42, b1 to b7 are the coefficients of each type of product, indicating the relative amount of each product generated in the reaction;

[0023] For cycloalkanes and aromatic hydrocarbons, at low temperatures, the side chains react; at high temperatures, ring-opening reactions occur and they continue to crack, and the reaction pathway is consistent with the principle of chain alkanes.

[0024] For the heterocyclic compounds, O ions are generated during the pyrolysis process, and the O ions combine with C ions to generate CO and CO2.

[0025] Preferably, the method calculates the mean square displacement of any dissolved gas in the following manner, including:

[0026] MSD(t)=<|r(t)-r(0)| 2 >,

[0027] Where MSD is the mean square displacement; r(t) and r(0) are the displacement coordinates of the particle at time t and the initial time, respectively; <> means finding the average value.

[0028] Preferably, for any dissolved gas, determining the diffusion coefficient curve of any dissolved gas in the insulating oil based on the mean square displacement of any dissolved gas at different temperatures includes:

[0029] For any dissolved gas, a mean square displacement curve is drawn based on the mean square displacement of the any dissolved gas at different temperatures;

[0030] Obtaining diffusion coefficients at different temperatures based on the mean square displacement curve;

[0031] Fitting the diffusion coefficients at different temperatures to obtain a diffusion coefficient curve of any dissolved gas in the insulating oil;

[0032] Wherein, the diffusion coefficient is the linear slope K of the mean square displacement curve, MSD(t) is the mean square displacement curve, t is the time variable, which is used to describe the movement of particles within a certain period of time.

[0033] According to another aspect of the present invention, a system for obtaining the diffusion coefficient of thermal decomposition dissolved gas of current transformer insulating oil is provided, the system comprising:

[0034] A component construction unit, used for constructing a molecular structure representing a typical component of insulating oil of an inverted oil-immersed current transformer, and geometrically optimizing the molecular structure of the typical component so that the molecular energy is in a stable state;

[0035] A first insulating oil model determination unit, used to construct a first insulating oil model of the inverted current transformer according to the composition ratio of the insulating oil and using periodic boundary conditions as constraints;

[0036] a first dynamic relaxation unit, configured to perform dynamic relaxation on the first insulating oil model so that the first insulating oil model reaches a stable state;

[0037] A reaction molecular dynamics simulation unit, used for performing reaction molecular dynamics simulation of insulating oil cracking based on the first insulating oil model under different high temperature conditions, and observing typical components of gas products of thermal cracking of the insulating oil;

[0038] a second insulating oil model determining unit, configured to construct a second insulating oil model containing dissolved gas based on the gas product;

[0039] a second dynamic relaxation unit, used for performing dynamic relaxation on the second insulating oil model so that the second insulating oil model reaches a stable state;

[0040] A mean square displacement determination unit, used for performing dynamic simulation on the second insulating oil model, applying different temperatures respectively, and obtaining the mean square displacement of any dissolved gas at different temperatures;

[0041] The diffusion coefficient determination unit is used to determine the diffusion coefficient curve of any dissolved gas in the insulating oil based on the mean square displacement of the any dissolved gas at different temperatures.

[0042] Preferably, the reaction molecular dynamics simulation unit uses a ReaxFF reaction force field to perform reaction molecular dynamics simulation, and the system energy contribution distribution of the ReaxFF reaction force field is:

[0043] E systeam =E bond +E tors +E over +E under +E lp +E val +E pen +E coa +E vdWaals +E coulomb +E specific ,

[0044] Among them, E bond is a function of the distance between atoms, representing the bond energy between atoms; E tors Represents the energy of dihedral angle torsion; E over and E under They represent the over-coordination energy correction and under-coordination energy correction based on the atomic valence rule respectively; E lp Represents the energy of lone pair electrons; E val , E pen and E coa They represent the energy of covalent bond angle bending, the penalty energy of one atom sharing two double bonds to destabilize the system, and the energy of three-point conjugation. vdWaals and E coulomb They represent the energy contributed by the van der Waals interaction and electrostatic interaction between all non-neighboring atoms without considering the bond order BO; E specific Represents the special energy contribution to a specific molecular system.

[0045] Preferably, the first insulating oil model comprises: 20 H 42 、Bicycloalkanes C 20 H 38 , bicyclic aromatic hydrocarbons and heterocyclic compounds C3H4O; in the molecular dynamics simulation of the reaction of insulating oil cracking, the alkane C 20 H 42 The decomposition of the alkane C 20 H 42 The first decomposition path is:

[0046]

[0047] Among them, a0+a1+...+a n-2 =∑a i=1(i=0,1,...,n-2), a i is the coefficient of each type of product, indicating the relative amount of each product generated in the reaction; n is the total number of product types;

[0048] Alkanes C 20 H 42 The secondary thermal decomposition path above 300°C is:

[0049]

[0050] Among them, b1+2(b2+b3+b4)+3(b5+b6)=20,4b1+6b2+4b3=2b4+8b5+6b6+2b7=42, b1 to b7 are the coefficients of each type of product, indicating the relative amount of each product generated in the reaction;

[0051] For cycloalkanes and aromatic hydrocarbons, at low temperatures, the side chains react; at high temperatures, ring-opening reactions occur and they continue to crack, and the reaction pathway is consistent with the principle of chain alkanes.

[0052] For the heterocyclic compounds, O ions are generated during the pyrolysis process, and the O ions combine with C ions to generate CO and CO2.

[0053] Preferably, the mean square displacement determining unit calculates the mean square displacement of any dissolved gas in the following manner, including:

[0054] MSD(t)=<|r(t)-r(0)| 2 >,

[0055] Where MSD is the mean square displacement; r(t) and r(0) are the displacement coordinates of the particle at time t and the initial time, respectively; <> means finding the average value.

[0056] Preferably, the diffusion coefficient determining unit determines, for any dissolved gas, a diffusion coefficient curve of the any dissolved gas in the insulating oil based on the mean square displacement of the any dissolved gas at different temperatures, including:

[0057] For any dissolved gas, a mean square displacement curve is drawn based on the mean square displacement of the any dissolved gas at different temperatures;

[0058] Obtaining diffusion coefficients at different temperatures based on the mean square displacement curve;

[0059] Fitting the diffusion coefficients at different temperatures to obtain a diffusion coefficient curve of any dissolved gas in the insulating oil;

[0060] Wherein, the diffusion coefficient is the linear slope K of the mean square displacement curve, MSD(t) is the mean square displacement curve, t is the time variable, which is used to describe the movement of particles within a certain period of time.

[0061] The present invention provides a method and system for obtaining the diffusion coefficient of dissolved gas in thermal cracking of insulating oil of a current transformer, comprising: constructing a molecular structure representing a typical component of insulating oil of an inverted oil-immersed current transformer, and geometrically optimizing the molecular structure of the typical component so that the molecular energy is in a stable state; constructing a first insulating oil model of an inverted current transformer according to the component ratio of the insulating oil and using periodic boundary conditions as constraints; performing dynamic relaxation on the first insulating oil model so that the first insulating oil model reaches a stable state; performing molecular dynamics simulation of the reaction of insulating oil cracking based on the first insulating oil model under different high temperature conditions, observing and determining the gas products of thermal cracking of the typical component; constructing a second insulating oil model containing dissolved gas based on the gas products; performing dynamic relaxation on the second insulating oil model so that the second insulating oil model reaches a stable state; performing dynamic simulation on the second insulating oil model, applying different temperatures respectively, and obtaining the mean square displacement of any dissolved gas at different temperatures; for any dissolved gas, determining the diffusion coefficient curve of any dissolved gas in the insulating oil based on the mean square displacement of the any dissolved gas at different temperatures. The present invention can not only accurately simulate the diffusion dynamics of thermal cracking products and dissolved gases in the insulating oil in the transformer, providing a scientific basis for equipment status monitoring and operation and maintenance, but also reveal the diffusion law of gas under different fault types by analyzing the microscopic mechanism of dissolved gas diffusion. The method of the present invention has unique advantages in predicting high-risk areas for gas accumulation, and can provide an accurate basis for early identification of early faults such as local overheating and local discharge; it can also help improve the design of the transformer, improve its withstand voltage capability and insulation performance, reduce the accumulation of gas in high electric field areas, and reduce the risk of discharge or explosion caused by gas accumulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0063] Figure 1 It is a flow chart of a method 100 for obtaining a diffusion coefficient of a dissolved gas in thermal decomposition of insulating oil of a current transformer according to an embodiment of the present invention;

[0064] Figure 2 A schematic diagram of a molecular model of a system of chain alkanes, bicycloalkanes, bicyclic aromatic hydrocarbons, heterocyclic compounds and insulating oil of an inverted oil-immersed current transformer according to an embodiment of the present invention;

[0065] Figure 3 A schematic diagram of a pyrolysis reaction path of insulating oil according to an embodiment of the present invention;

[0066] Figure 4 Schematic diagram of the relative content distribution of the final characteristic products of the pyrolysis reaction at 1800K-3200K according to an embodiment of the present invention;

[0067] Figure 5 is a schematic diagram of a hydrogen mean square displacement (MSD) curve of an insulating oil model containing 5 hydrogen molecules according to an embodiment of the present invention;

[0068] Figure 6 A schematic diagram of a diffusion coefficient fitting curve of hydrogen at 298K-343K according to an embodiment of the present invention;

[0069] Figure 7 Schematic diagram of the structure of a system 700 for obtaining the diffusion coefficient of dissolved gas in thermal decomposition of current transformer insulating oil according to an embodiment of the present invention. DETAILED DESCRIPTION

[0070] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0071] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0072] Figure 1 FIG. 1 is a flow chart of a method 100 for obtaining a diffusion coefficient of a dissolved gas in thermal decomposition of insulating oil of a current transformer according to an embodiment of the present invention. Figure 1As shown, the method for obtaining the diffusion coefficient of dissolved gas by thermal decomposition of insulating oil of current transformer provided by the embodiment of the present invention can not only accurately simulate the diffusion dynamics of thermal decomposition products and dissolved gas in the insulating oil in the transformer, and provide a scientific basis for equipment status monitoring and operation and maintenance, but also can reveal the diffusion law of gas under different fault types by analyzing the microscopic mechanism of dissolved gas diffusion. The method of the present invention has unique advantages in predicting high-risk areas of gas accumulation, and can provide accurate basis for early identification of early faults such as local overheating and local discharge; it can also help improve the design of the transformer, improve its withstand voltage and insulation performance, reduce the accumulation of gas in high electric field areas, and reduce the risk of discharge or explosion caused by gas accumulation. The method 100 for obtaining the diffusion coefficient of dissolved gas by thermal decomposition of insulating oil of current transformer provided by the embodiment of the present invention starts from step 101. In step 101, a molecular structure representing a typical component of insulating oil of an inverted oil-immersed current transformer is constructed, and the molecular structure of the typical component is geometrically optimized so that the molecular energy is in a stable state.

[0073] In step 102, according to the composition ratio of the insulating oil, a first insulating oil model of the inverted current transformer is constructed using periodic boundary conditions as constraints.

[0074] In step 103, dynamic relaxation is performed on the first insulating oil model so that the first insulating oil model reaches a stable state.

[0075] In the present invention, the alkane (C n H 2n+2 , mass fraction about 60%), cycloalkanes (C n H 2n , mass fraction of about 10%-40%) and aromatic hydrocarbons (C n H 2n-6 , mass fraction is about 5%-15%). Three typical components of insulating oil are selected, namely, paraffin, C 20 H 42 、Bicycloalkanes C 20 H 38 , bicyclic aromatic hydrocarbons C 20 H 26and heterocyclic compound C3H4O. The constructed molecular structure is geometrically optimized using the Forcite module, so that the molecular energy of each typical component is in the most stable state. Then a molecular model of the inverted current transformer insulating oil system composed of alkane, cycloalkane and aromatic hydrocarbon molecules is constructed, that is, the first insulating oil model. Specifically, through the construction module of Materials Studio software, based on the principles of classical Newtonian mechanics, the molecular dynamics method is used according to the component ratio of mineral insulating oil, and periodic boundary conditions are used as constraints to construct the Amorphous Cell model of the inverted current transformer insulating oil; and the constructed inverted current transformer insulating oil model box is dynamically relaxed to make the system reach a stable state.

[0076] In step 104, a molecular dynamics simulation of the cracking reaction of insulating oil is performed based on the first insulating oil model under different high temperature conditions to observe typical components of gas products of thermal cracking of the insulating oil.

[0077] Preferably, the method uses a ReaxFF reaction force field to perform reaction molecular dynamics simulation, and the system energy contribution distribution of the ReaxFF reaction force field is:

[0078] E systeam =E bond +E tors +E over +E under +E lp +E val +E pen +E coa +E vdWaals +E coulomb +E specific ,

[0079] Among them, E bond is a function of the distance between atoms, representing the bond energy between atoms; E tors Represents the energy of dihedral angle torsion; E over and E under They represent the over-coordination energy correction and under-coordination energy correction based on the atomic valence rule respectively; E lp Represents the energy of lone pair electrons; E val , E pen and E coa They represent the energy of covalent bond angle bending, the penalty energy of one atom sharing two double bonds to destabilize the system, and the energy of three-point conjugation. vdWaals and E coulomb They represent the energy contributed by the van der Waals interaction and electrostatic interaction between all non-neighboring atoms without considering the bond order BO; E specific Represents the special energy contribution to a specific molecular system.

[0080] Preferably, the first insulating oil model comprises: 20 H 42 、Bicycloalkanes C 20 H 38 , bicyclic aromatic hydrocarbons and heterocyclic compounds C3H4O; in the molecular dynamics simulation of the reaction of insulating oil cracking, the alkane C 20 H 42 The decomposition of the alkane C 20 H 42 The first decomposition path is:

[0081]

[0082] Among them, a0+a1+...+a n-2 =∑a i =1(i=0,1,...,n-2), a i is the coefficient of each type of product, indicating the relative amount of each product generated in the reaction; n is the total number of product types;

[0083] Alkanes C 20 H 42 The secondary thermal decomposition path above 300°C is:

[0084]

[0085] Among them, b1+2(b2+b3+b4)+3(b5+b6)=20,4b1+6b2+4b3=2b4+8b5+6b6+2b7=42, b1 to b7 are the coefficients of each type of product, indicating the relative amount of each product generated in the reaction;

[0086] For cycloalkanes and aromatic hydrocarbons, at low temperatures, the side chains react; at high temperatures, ring-opening reactions occur and they continue to crack, and the reaction pathway is consistent with the principle of chain alkanes.

[0087] For the heterocyclic compounds, O ions are generated during the pyrolysis process, and the O ions combine with C ions to generate CO and CO2.

[0088] In the present invention, under different high temperature conditions, the reaction molecular dynamics simulation of insulating oil cracking is carried out based on the ReaxFF force field to summarize the main gas products of thermal cracking of the first insulating oil; based on the products generated by thermal cracking, a second insulating oil model containing dissolved gas is constructed.

[0089] Specifically, in the present invention, the molecular model of the adjusted insulating oil system and the models of each alkane, cycloalkane and aromatic hydrocarbon are respectively subjected to reaction molecular dynamics calculations using the ReaxFF force field to obtain the main reaction paths of characteristic gas products of thermal cracking of insulating oil at a temperature of 1800K-3200K.

[0090] When the ReaxFF reaction force field is used for reaction molecular dynamics calculation, the system energy contribution of the ReaxFF reaction force field is distributed as follows:

[0091] E systeam =E bond +E tors +E over +E under +E lp +E val +E pen +E coa +E vdWaals +E coulomb +E specific ,

[0092] Among them, E bond is a function of the distance between atoms, representing the bond energy between atoms; E tors Represents the energy of dihedral angle torsion; E over and E under They represent the over-coordination energy correction and under-coordination energy correction based on the atomic valence rule respectively; E lp Represents the energy of lone pair electrons; E val , E pen and E coa They represent the energy of covalent bond angle bending, the penalty energy of one atom sharing two double bonds to destabilize the system, and the energy of three-point conjugation. vdWaals and E coulomb They represent the energy contributed by the van der Waals interaction and electrostatic interaction between all non-neighboring atoms without considering the bond order BO; E specific It represents the special energy contribution to a specific molecular system, such as the energy part affected by four-point conjugation, hydrogen bonding and C2 correction.

[0093] For alkanes C 20 H 42 , which is thermally unstable, and its decomposition is usually divided into primary decomposition and secondary decomposition. 20 H 42 The first decomposition path is:

[0094]

[0095] Among them, a0+a1+...+a n-2 =∑a i=1(i=0,1,...,n-2).

[0096] For alkanes C 20 H 42 , its secondary thermal decomposition path above 300℃ is:

[0097]

[0098] Among them, b1+2(b2+b3+b4)+3(b5+b6)=20, 4b1+6b2+4b3=2b4+8b5+6b6+2b7=42.

[0099] At low temperatures, cycloalkanes and aromatic hydrocarbons mainly react at the side chains; at high temperatures, ring-opening reactions occur, followed by continuous cracking. The reaction pathway is similar to that of chain alkanes and will not be repeated here.

[0100] For heterocyclic compounds, O ions are generated during the pyrolysis process, and O ions quickly combine with C ions to generate CO and CO2.

[0101] In step 105, a second insulating oil model containing dissolved gas is constructed based on the gas product.

[0102] In step 106, dynamic relaxation is performed on the second insulating oil model so that the second insulating oil model reaches a stable state.

[0103] In the present invention, a second insulating oil model containing dissolved gas small molecules is constructed, and the above steps are repeated to complete the dynamic relaxation of the second insulating oil model, so that the second insulating oil model reaches a stable state.

[0104] In step 107, dynamic simulation is performed on the second insulating oil model, and different temperatures are applied respectively to obtain the mean square displacement of any dissolved gas at different temperatures.

[0105] Preferably, the method calculates the mean square displacement of any dissolved gas in the following manner, including:

[0106] MSD(t)=<|r(t)-r(0)| 2 >,

[0107] Where MSD is the mean square displacement; r(t) and r(0) are the displacement coordinates of the particle at time t and the initial time, respectively; <> means finding the average value.

[0108] In step 108, for any dissolved gas, a diffusion coefficient curve of the any dissolved gas in the insulating oil is determined based on the mean square displacement of the any dissolved gas at different temperatures.

[0109] Preferably, for any dissolved gas, determining the diffusion coefficient curve of any dissolved gas in the insulating oil based on the mean square displacement of any dissolved gas at different temperatures includes:

[0110] For any dissolved gas, a mean square displacement curve is drawn based on the mean square displacement of the any dissolved gas at different temperatures;

[0111] Obtaining diffusion coefficients at different temperatures based on the mean square displacement curve;

[0112] Fitting the diffusion coefficients at different temperatures to obtain a diffusion coefficient curve of any dissolved gas in the insulating oil;

[0113] Wherein, the diffusion coefficient is the linear slope K of the mean square displacement curve, MSD(t) is the mean square displacement curve, t is the time variable, which is used to describe the movement of particles within a certain period of time.

[0114] In the present invention, firstly, a sub-dynamic simulation is performed on the constructed second insulating oil model, different temperatures are applied respectively, and the mean square displacement of all gas molecules is calculated according to the following formula:

[0115] MSD(t)=<|r(t)-r(0)| 2 >,

[0116] Where MSD is the mean square displacement; r(t) and r(0) are the displacement coordinates of the particle at time t and the initial time, respectively; <> means finding the average value.

[0117] Then, the mean square displacement obtained by simulation calculation is plotted into a curve. The slope K of the fitted straight line is the diffusion coefficient of the gas molecules. The formula for the slope of the fitting curve is as follows:

[0118]

[0119] Where K is the slope of the fitted straight line. In actual simulation, it is impossible to calculate for an infinite time. Therefore, in actual calculation, a finite time simulation is performed to calculate the slope in an area where the MSD is relatively flat and the statistical error is small.

[0120] The method for obtaining the diffusion coefficient of dissolved gas by thermal decomposition of insulating oil of an inverted current transformer proposed by the present invention can calculate the actual operating state, the calculation result is accurate, and can reflect the typical diffusion coefficient of dissolved gas inside the inverted oil-immersed current transformer.

[0121] The following specifically illustrates the embodiments of the present invention.

[0122] In an embodiment of the present invention, the process of determining the gas diffusion coefficient includes the following steps:

[0123] (1) First, construct an alkane (C n H 2n+2 , mass fraction about 60%), cycloalkanes (C n H 2n , mass fraction of about 10%-40%) and aromatic hydrocarbons (C n H 2n-6 , mass fraction of about 5%-15%). The model of the present invention selects three typical components of insulating oil, namely, paraffin, C 20 H 42 、Bicycloalkanes C 20 H 38 , bicyclic aromatic hydrocarbons C 20 H 26 And the heterocyclic compound C3H4O was simulated.

[0124] Among them, the structures of the molecular models of chain alkanes, bicyclic alkanes, bicyclic aromatic hydrocarbons, heterocyclic compounds and inverted oil-immersed current transformer insulating oil systems are as follows: Figure 2 As shown, wherein (a) is a chain alkane C 20 H 42 , (b) is a bicycloalkane C 20 H 38 , (c) is a bicyclic aromatic hydrocarbon C 20 H 26 , (d) is the heterocyclic compound C3H4O, and (e) is the insulating oil balance system model.

[0125] (2) Then, the Forcite module is used to geometrically optimize the constructed molecular structure so that the molecular energy optimized in step (1) is in the most stable state. The CompassⅡ force field is selected during the optimization process, and the charge of the molecular structure is calculated through Forcefieldassigned. Then, a molecular model of an inverted current transformer insulating oil system composed of alkane, cycloalkane and aromatic hydrocarbon molecules is constructed, and the structure is optimized to obtain the minimum energy system conformation, and the density and initial temperature of the insulating oil molecular system are set and adjusted according to the actual density and temperature.

[0126] (3) Secondly, the insulating oil system was established using the Amorphous Cell module of MS, and the liquid density was set to 0.9 g / cm 3 , the side length of the box is The liquid system contains 33 molecules in total. According to the composition ratio of mineral insulating oil, the chain alkane C 20 H 42 、Bicycloalkanes C 20 H 38 , bicyclic aromatic hydrocarbons C 20 H 26and heterocyclic compound C3H4O in a ratio of 6:3:1:1, the numbers are 18, 9, 3, and 3 respectively. Periodic boundary conditions are used as constraints to avoid unnecessary overlap. The constructed liquid model is then dynamically relaxed to make the system reach a stable state. The Smant algorithm is used, and the electrostatic and van der Waals options are selected as: Group based; for annealing of the insulating oil system, a regular system with constant N (number of particles), V (volume), and T (temperature) is selected, and the model is subjected to 5 cycles of heating and then cooling annealing. After treatment, the internal stress of the model is reduced and it is in a stable state. The density of the liquid system is about 0.83gcm 3 , which is close to the actual density of mineral oil, which also shows that the dynamic relaxation process is effective. In the stable state, the side length of the box is

[0127] (4) In order to study the effect of temperature on the decomposition of macromolecules of insulating oil in inverted current transformers, the dynamics function of the Gulp module was used to observe the dynamic changes of thermal decomposition of the liquid system at different temperatures. The force field selected was the ReaxFF6.0 force field, the system was set to the NVT (constant number of particles, volume and temperature) regular system, the step size was 0.02, the simulation time was 100ps, one frame was output every 1000 steps, and the charge was set to Forcefield assigned. The simulation temperature was between 1800-3200K, with an interval of 200K. The system energy contribution distribution of the ReaxFF reaction force field is as follows:

[0128] E systeam =E bond +E tors +E over +E under +E lp +E val +E pen +E coa +E vdWaals +E coulomb +E specific ,

[0129] Among them, E bond A function representing the distance between atoms, reflecting the bond energy between atoms; E tors Represents the energy of dihedral angle torsion; E over and E under are the over-coordination energy correction and under-coordination energy correction of the atomic valence rule; E lp Represents the energy of lone pair electrons; E val , E pen and E coa E are the covalent bond angle bending energy, the penalty energy when atoms share two double bonds, and the three-point conjugation energy.vdWaals and E coulomb They represent the energy contributed by the van der Waals force and electrostatic force between non-neighboring atoms without considering the bond order BO; E specific It represents the special energy contribution in a specific molecular system, such as the energy part of four-point conjugation, hydrogen bonding and C2 correction.

[0130] Observe the free radical chain reaction at different temperatures and the distribution of statistical characteristic products. Figure 3 is the reaction path of the pyrolysis of insulating oil and the generation path of each product, with C 20 H 42 For example, chain alkane C 20 H 42 Thermally unstable, decomposition is usually divided into primary decomposition and secondary decomposition. 20 H 42 The first decomposition path is:

[0131]

[0132] Among them, a0+a1+...+a n-2 =∑a i =1(i-0,1,...,n-2), a i is the coefficient of each type of product, indicating the relative amount of each product generated in the reaction; n is the total number of product types, that is, C 20 H 42 The number of different product groups that will be produced after decomposition.

[0133] Alkanes C 20 H 42 The secondary thermal decomposition path above 300°C is:

[0134]

[0135] Among them, b1+2(b2+b3+b4)+3(b5+b6)=20, 4b1+6b2+4b3=2b4+8b5+6b6+2b7=42.

[0136] Under low temperature conditions, cycloalkanes and aromatic hydrocarbons mainly undergo side chain reactions; at high temperatures, these compounds undergo ring-opening reactions and then continue to crack. The reaction pathway is similar to that of alkanes, so it will not be described in detail. Heterocyclic compounds will generate O ions during pyrolysis, and O ions will quickly combine with C ions to generate CO and CO2. Figure 4 It can be seen that in the temperature range of 1800-3200K, the main products of the pyrolysis of insulating oil are clearly reflected.

[0137] (5) Construct an insulating oil model containing dissolved gas molecules and repeat steps (1)-(3) to complete the dynamic relaxation of the model. Next, use the NVT ensemble (keep the number of particles N, volume V and temperature T unchanged) to calculate the molecular dynamics behavior of the optimized model at different temperatures in the range of 298K to 343K on a time scale of 300ps at intervals of 5K. During the simulation, the integration step is set to 1fs, and dynamic data is collected every 5000 steps with a cutoff radius of The Nose algorithm is used for temperature control, the Berendsen method is used for pressure control, the initial velocity of the particles is randomly assigned according to the Boltzmann distribution, the velocity Verlet method is used for integration, the van der Waals interaction is estimated by an atom-based method, and the electrostatic interaction is calculated by the Ewald method.

[0138] (6) Finally, the MSD curves at 10 temperature points in the range of 298 K to 343 K were analyzed. In the Forcite analysis module, the “Mean Square Displacement” function was used to set appropriate initial frame, step size, and end frame to calculate the hydrogen diffusion behavior at each temperature point.

[0139] Taking hydrogen as an example, the mean square displacement (MSD) curve fitting results of hydrogen in the insulating oil of an inverted oil-immersed current transformer at different temperatures are shown in the figure below: Figure 5 As shown in (a) to (k). Then, the diffusion coefficient K of hydrogen in insulating oil at different temperatures is calculated from the existing MSD curve. The calculation formula of the diffusion coefficient is as follows:

[0140]

[0141] It is impossible to calculate for an infinite time in actual simulation. Therefore, in actual calculation, a finite time simulation is performed to take the area where the MSD is relatively flat and the statistical error is small to calculate the slope, that is, the diffusion coefficient K.

[0142] Specifically, the diffusion coefficient of hydrogen as it changes with temperature is calculated, such as Figure 6 As shown, fitting is performed again to obtain the fitted hydrogen diffusion coefficient curve:

[0143] V=5.84247×10 -8 -0.00222*0.9645 T ,

[0144] Where T is temperature.

[0145] As can be seen from the above, with the increase of temperature, the MSD curve rises significantly, indicating that the diffusion rate of hydrogen at higher temperatures is significantly accelerated. This is consistent with the classical molecular diffusion theory, that is, the increase in temperature will enhance the thermal motion of molecules, thereby accelerating the diffusion process. All curves show a high diffusion rate in the initial stage, and then gradually flatten out, reflecting the trend of the diffusion rate slowing down over time. The above results show that the diffusion coefficient of hydrogen in insulating oil changes significantly with temperature, which further verifies the necessity of studying gas diffusion behavior in oil-immersed electrical equipment and its potential application value in equipment status monitoring.

[0146] Figure 7 FIG. 7 is a schematic diagram of a system 700 for obtaining a diffusion coefficient of a dissolved gas in thermal decomposition of insulating oil of a current transformer according to an embodiment of the present invention. Figure 7 As shown, a system 700 for obtaining the diffusion coefficient of dissolved gas during thermal decomposition of insulating oil of a current transformer provided in an embodiment of the present invention includes: a component construction unit 701, a first insulating oil model determination unit 702, a first kinetic relaxation unit 703, a reaction molecular dynamics simulation unit 704, a second insulating oil model determination unit 705, a second kinetic relaxation unit 706, a mean square displacement determination unit 707 and a diffusion coefficient determination unit 708.

[0147] Preferably, the component construction unit 701 is used to construct a molecular structure representing a typical component of the insulating oil of an inverted oil-immersed current transformer, and geometrically optimize the molecular structure of the typical component so that the molecular energy is in a stable state.

[0148] Preferably, the first insulating oil model determining unit 702 is used to construct a first insulating oil model of the inverted current transformer according to the composition ratio of the insulating oil and using periodic boundary conditions as constraints.

[0149] Preferably, the first dynamic relaxation unit 703 is used to perform dynamic relaxation on the first insulating oil model so that the first insulating oil model reaches a stable state.

[0150] Preferably, the reaction molecular dynamics simulation unit 704 is used to perform reaction molecular dynamics simulation of insulating oil cracking based on the first insulating oil model under different high temperature conditions, and observe typical components to determine the gas products of thermal cracking of the insulating oil.

[0151] Preferably, the reaction molecular dynamics simulation unit 704 uses a ReaxFF reaction force field to perform reaction molecular dynamics simulation, and the system energy contribution distribution of the ReaxFF reaction force field is:

[0152] E systeam =E bond +E tors +Eover +E under +E lp +E val +E pen +E coa +E vdWaals +E coulomb +E specific ,

[0153] Among them, E bond is a function of the distance between atoms, representing the bond energy between atoms; E tors Represents the energy of dihedral angle torsion; E over and E under They represent the over-coordination energy correction and under-coordination energy correction based on the atomic valence rule respectively; E lp Represents the energy of lone pair electrons; E val , E pen and E coa They represent the energy of covalent bond angle bending, the penalty energy of one atom sharing two double bonds to destabilize the system, and the energy of three-point conjugation. vdWaals and E coulomb They represent the energy contributed by the van der Waals interaction and electrostatic interaction between all non-neighboring atoms without considering the bond order BO; E specific Represents the special energy contribution to a specific molecular system.

[0154] Preferably, the first insulating oil model comprises: 20 H 42 、Bicycloalkanes C 20 H 38 , bicyclic aromatic hydrocarbons and heterocyclic compounds C3H4O; in the molecular dynamics simulation of the reaction of insulating oil cracking, the alkane C 20 H 42 The decomposition of the alkane C 20 H 42 The first decomposition path is:

[0155]

[0156] Among them, a0+a1+...+a n-2 =∑a i =1(i=0,1,...,n-2), a i is the coefficient of each type of product, indicating the relative amount of each product generated in the reaction; n is the total number of product types;

[0157] Alkanes C 20 H 42 The secondary thermal decomposition path above 300°C is:

[0158]

[0159] Among them, b1+2(b2+b3+b4)+3(b5+b6)=20,4b1+6b2+4b3=2b4+8b5+6b6+2b7=42, b1 to b7 are the coefficients of each type of product, indicating the relative amount of each product generated in the reaction;

[0160] For cycloalkanes and aromatic hydrocarbons, at low temperatures, the side chains react; at high temperatures, ring-opening reactions occur and they continue to crack, and the reaction pathway is consistent with the principle of chain alkanes.

[0161] For the heterocyclic compounds, O ions are generated during the pyrolysis process, and the O ions combine with C ions to generate CO and CO2.

[0162] Preferably, the second insulating oil model determining unit 705 is used to construct a second insulating oil model containing dissolved gas based on the gas product.

[0163] Preferably, the second dynamic relaxation unit 706 is used to perform dynamic relaxation on the second insulating oil model so that the second insulating oil model reaches a stable state.

[0164] Preferably, the mean square displacement determining unit 707 is used to perform dynamic simulation on the second insulating oil model, apply different temperatures respectively, and obtain the mean square displacement of any dissolved gas at different temperatures.

[0165] Preferably, the mean square displacement determining unit 707 calculates the mean square displacement of any dissolved gas in the following manner, including:

[0166] MSD(t)=<|r(t)-r(0)| 2 >,

[0167] Where MSD is the mean square displacement; r(t) and r(0) are the displacement coordinates of the particle at time t and the initial time, respectively; <> means finding the average value.

[0168] Preferably, the diffusion coefficient determining unit 708 is used to determine, for any dissolved gas, a diffusion coefficient curve of the any dissolved gas in the insulating oil based on the mean square displacement of the any dissolved gas at different temperatures.

[0169] Preferably, the diffusion coefficient determining unit 708 determines, for any dissolved gas, a diffusion coefficient curve of the any dissolved gas in the insulating oil based on the mean square displacement of the any dissolved gas at different temperatures, including:

[0170] For any dissolved gas, a mean square displacement curve is drawn based on the mean square displacement of the any dissolved gas at different temperatures;

[0171] Obtaining diffusion coefficients at different temperatures based on the mean square displacement curve;

[0172] Fitting the diffusion coefficients at different temperatures to obtain a diffusion coefficient curve of any dissolved gas in the insulating oil;

[0173] Wherein, the diffusion coefficient is the linear slope K of the mean square displacement curve, MSD(t) is the mean square displacement curve, t is the time variable, which is used to describe the movement of particles within a certain period of time.

[0174] The system 700 for obtaining the diffusion coefficient of dissolved gas by thermal decomposition of current transformer insulating oil in an embodiment of the present invention corresponds to the method 100 for obtaining the diffusion coefficient of dissolved gas by thermal decomposition of current transformer insulating oil in another embodiment of the present invention, and will not be described in detail here.

[0175] The invention has been described above with reference to a few embodiments. However, it is readily apparent to a person skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the invention, as defined by the appended patent claims.

[0176] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise therein. All references to "a / said / the [means, components, etc.]" are to be openly interpreted as at least one instance of said means, components, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily have to be performed in the exact order disclosed, unless explicitly stated otherwise.

[0177] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0178] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0179] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0180] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0181] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for obtaining the diffusion coefficient of dissolved gas by thermal decomposition of current transformer insulating oil, characterized in that: The method comprises: Construct the molecular structure representing the typical components of the insulating oil of the inverted oil-immersed current transformer, and geometrically optimize the molecular structure of the typical components so that the molecular energy is in a stable state; According to the composition ratio of insulating oil, the first insulating oil model of inverted current transformer is constructed by using periodic boundary conditions as constraints. Performing dynamic relaxation on the first insulating oil model so that the first insulating oil model reaches a stable state; Under different high temperature conditions, molecular dynamics simulation of the cracking reaction of insulating oil is performed based on the first insulating oil model to observe the typical components of the gas products of thermal cracking of the insulating oil; constructing a second insulating oil model containing dissolved gas based on the gas product; Performing dynamic relaxation on the second insulating oil model so that the second insulating oil model reaches a stable state; Performing dynamic simulation on the second insulating oil model, applying different temperatures respectively, and obtaining the mean square displacement of any dissolved gas at different temperatures; For any dissolved gas, a diffusion coefficient curve of the any dissolved gas in the insulating oil is determined based on the mean square displacement of the any dissolved gas at different temperatures.

2. The method according to claim 1, characterized in that The method uses the ReaxFF reaction force field to perform reaction molecular dynamics simulation, and the system energy contribution distribution of the ReaxFF reaction force field is: AND systeam =And bond +E tors +E over +E under +E lp +E val +E pen +E coa +E vdWaals +E coulomb +E specific , Among them, E bond is a function of the distance between atoms, representing the bond energy between atoms; E tors Represents the energy of dihedral angle torsion; E over and E under They represent the over-coordination energy correction and under-coordination energy correction based on the atomic valence rule respectively; E lp Represents the energy of lone pair electrons; E val , E pen and E coa They represent the energy of covalent bond angle bending, the penalty energy of one atom sharing two double bonds to destabilize the system, and the energy of three-point conjugation. vdWaals and E coulomb They represent the energy contributed by the van der Waals interaction and electrostatic interaction between all non-neighboring atoms without considering the bond order BO; E specific Represents the special energy contribution to a specific molecular system.

3. The method according to claim 1, characterized in that The first insulating oil model comprises: chain alkane C 20 H 42 、Bicycloalkanes C 20 H 38 , bicyclic aromatic hydrocarbons and heterocyclic compounds C3H4O; in the molecular dynamics simulation of the reaction of insulating oil cracking, the alkane C 20 H 42 The decomposition of chain alkane C 20 H 42 The first decomposition path is: Among them, a0+a1+...+a n-2 =Σa i =1(i=0,1,...,n-2), a i is the coefficient of each type of product, indicating the relative amount of each product generated in the reaction; n is the total number of product types; Alkanes C 20 H 42 The secondary thermal decomposition path above 300°C is: Among them, b1+2(b2+b3+b4)+3(b5+b6)=20,4b1+6b2+4b3=2b4+8b5+6b6+2b7=42, b1 to b7 are the coefficients of each type of product, indicating the relative amount of each product generated in the reaction; For cycloalkanes and aromatic hydrocarbons, at low temperatures, the side chains react; at high temperatures, ring-opening reactions occur and they continue to crack, and the reaction pathway is consistent with the principle of chain alkanes; For the heterocyclic compounds, O ions are generated during the pyrolysis process, and the O ions combine with C ions to generate CO and CO2.

4. The method according to claim 1, characterized in that: The method calculates the mean square displacement of any dissolved gas in the following manner, including: MSD(t)=<|r(t)-r(0)| 2 >, Where MSD is the mean square displacement; r(t) and r(0) are the displacement coordinates of the particle at time t and the initial time, respectively; <> means finding the average value.

5. The method according to claim 1, characterized in that For any dissolved gas, determining a diffusion coefficient curve of the any dissolved gas in the insulating oil based on the mean square displacement of the any dissolved gas at different temperatures includes: For any dissolved gas, a mean square displacement curve is drawn based on the mean square displacement of the any dissolved gas at different temperatures; Obtaining diffusion coefficients at different temperatures based on the mean square displacement curve; Fitting the diffusion coefficients at different temperatures to obtain a diffusion coefficient curve of any dissolved gas in the insulating oil; Wherein, the diffusion coefficient is the linear slope K of the mean square displacement curve, MSD(t) is the mean square displacement curve, t is the time variable, which is used to describe the movement of particles within a certain period of time.

6. A system for obtaining the diffusion coefficient of dissolved gas from thermal decomposition of current transformer insulating oil, characterized in that: The system comprises: A component construction unit, used for constructing a molecular structure representing a typical component of insulating oil of an inverted oil-immersed current transformer, and geometrically optimizing the molecular structure of the typical component so that the molecular energy is in a stable state; A first insulating oil model determination unit, used to construct a first insulating oil model of the inverted current transformer according to the composition ratio of the insulating oil and using periodic boundary conditions as constraints; a first dynamic relaxation unit, configured to perform dynamic relaxation on the first insulating oil model so that the first insulating oil model reaches a stable state; A reaction molecular dynamics simulation unit, used for performing reaction molecular dynamics simulation of insulating oil cracking based on the first insulating oil model under different high temperature conditions, and observing typical components of gas products of thermal cracking of the insulating oil; a second insulating oil model determining unit, configured to construct a second insulating oil model containing dissolved gas based on the gas product; a second dynamic relaxation unit, used for performing dynamic relaxation on the second insulating oil model so that the second insulating oil model reaches a stable state; A mean square displacement determination unit, used for performing dynamic simulation on the second insulating oil model, applying different temperatures respectively, and obtaining the mean square displacement of any dissolved gas at different temperatures; The diffusion coefficient determination unit is used to determine the diffusion coefficient curve of any dissolved gas in the insulating oil based on the mean square displacement of the any dissolved gas at different temperatures.

7. The system according to claim 6, characterized in that The reaction molecular dynamics simulation unit uses the ReaxFF reaction force field to perform reaction molecular dynamics simulation. The system energy contribution distribution of the ReaxFF reaction force field is: AND systeam =And bond +E tors +E over +E under +E lp +E val +E pen +E coa +E vdWaals +E coulomb +E specific , Among them, E bond is a function of the distance between atoms, representing the bond energy between atoms; E tors Represents the energy of dihedral angle torsion; E over and E under They represent the over-coordination energy correction and under-coordination energy correction based on the atomic valence rule respectively; E lp Represents the energy of lone pair electrons; E val , E pen and E coa They represent the energy of covalent bond angle bending, the penalty energy of one atom sharing two double bonds to destabilize the system, and the energy of three-point conjugation. vdWaals and E coulomb They represent the energy contributed by the van der Waals interaction and electrostatic interaction between all non-neighboring atoms without considering the bond order BO; E specific Represents the special energy contribution to a specific molecular system.

8. The system according to claim 6, characterized in that The first insulating oil model comprises: chain alkane C 20 H 42 、Bicycloalkanes C 20 H 38 , bicyclic aromatic hydrocarbons and heterocyclic compounds C3H4O; in the molecular dynamics simulation of the reaction of insulating oil cracking, the alkane C 20 H 42 The decomposition of chain alkane C 20 H 42 The first decomposition path is: Among them, a0+a1+...+a n-2 =∑a i =1(i=0,1,...,n-2), a i is the coefficient of each type of product, indicating the relative amount of each product generated in the reaction; n is the total number of product types; Alkanes C 20 H 42 The secondary thermal decomposition path above 300°C is: Among them, b1+2(b2+b3+b4)+3(b5+b6)=20,4b1+6b2+4b3=2b4+8b5+6b6+2b7=42, b1 to b7 are the coefficients of each type of product, indicating the relative amount of each product generated in the reaction; For cycloalkanes and aromatic hydrocarbons, at low temperatures, the side chains react; at high temperatures, ring-opening reactions occur and they continue to crack, and the reaction pathway is consistent with the principle of chain alkanes; For the heterocyclic compounds, O ions are generated during the pyrolysis process, and the O ions combine with C ions to generate CO and CO2.

9. The system according to claim 6, characterized in that The mean square displacement determination unit calculates the mean square displacement of any dissolved gas in the following manner, including: MSD(t)=<|r(t)-r(0)| 2 >, Where MSD is the mean square displacement; r(t) and r(0) are the displacement coordinates of the particle at time t and the initial time, respectively; <> means finding the average value.

10. The system according to claim 6, characterized in that The diffusion coefficient determination unit determines, for any dissolved gas, a diffusion coefficient curve of the any dissolved gas in the insulating oil based on the mean square displacement of the any dissolved gas at different temperatures, including: For any dissolved gas, a mean square displacement curve is drawn based on the mean square displacement of the any dissolved gas at different temperatures; Obtaining diffusion coefficients at different temperatures based on the mean square displacement curve; Fitting the diffusion coefficients at different temperatures to obtain a diffusion coefficient curve of any dissolved gas in the insulating oil; Wherein, the diffusion coefficient is the linear slope K of the mean square displacement curve, MSD(t) is the mean square displacement curve, t is the time variable, which is used to describe the movement of particles within a certain period of time.

Images