A numerical simulation method for the partial discharge decomposition mechanism of environmentally friendly insulating gas

Abstract

The present invention belongs to the field of high voltage and insulation technology, and in particular relates to a numerical simulation method for the decomposition mechanism of partial discharge of environmentally friendly insulating gases. First, the electron transport parameters and energy transfer coefficient parameters are solved; secondly, the plasma chemical reaction model is used to ionize and decompose the environmentally friendly insulating gas to obtain the electron source term, heavy ion source term, and ion energy term; finally, the fluid dynamics model is used to obtain the convective motion distribution of the particles based on the obtained electron source term, heavy ion source term, and ion energy term control terms. The technical solution proposed by the present invention can be used to study the decomposition mechanism of PD of various environmentally friendly insulating gases without the need for a large number of experiments. It can evaluate the microscopic change mechanism of the discharge components of PD of environmentally friendly insulating gases and has broad application prospects in this field.

Description

Technical Field

[0001] The present invention belongs to the field of high voltage and insulation technology, and in particular relates to a numerical simulation method for the partial discharge decomposition mechanism of environmentally friendly insulating gas. Background Art

[0002] To further reduce the power transmission and distribution equipment manufacturing industry's reliance on the potent greenhouse gas sulfur hexafluoride (SF6), the development and application of environmentally friendly insulating gases is crucial. When evaluating the comprehensive performance of gas insulating media, in addition to basic insulation and environmental characteristics, attention should also be paid to the gas's partial discharge stability and decomposition characteristics.

[0003] In reality, insulation defects inevitably arise within gas-insulated equipment during manufacturing, transportation, installation, operation, and maintenance. These defects can trigger partial discharge (PD) in strong electromagnetic environments. The impact ionization and electron adsorption processes generated by PD can cause the environmentally friendly insulating gas to decompose, producing a series of decomposition products. Because the molecular structure of environmentally friendly insulating gases is more complex and lacks symmetry compared to SF6, and some gases contain reactive functional groups such as ketone (C=O) and hydrogen (CN), existing methods for evaluating the stability and decomposition characteristics of environmentally friendly insulating gases rely primarily on experimental testing, lacking numerical simulation methods for the relevant decomposition mechanisms. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention proposes a numerical simulation method for the partial discharge decomposition mechanism of environmentally friendly insulating gas. The technical solution is as follows:

[0005] A numerical simulation method for the partial discharge decomposition mechanism of environmentally friendly insulating gas, characterized in that:

[0006] For the environmentally friendly insulating gas to be analyzed, the electron transport parameters and energy transfer coefficient parameters are first solved;

[0007] Secondly, the plasma chemical reaction model is used to ionize and decompose the environmentally friendly insulating gas to obtain the electron source term, heavy ion source term, and ion energy term;

[0008] Finally, based on the obtained electron source term, heavy ion source term and electric ion energy term control terms, the fluid dynamics model is used to obtain the convective motion distribution of the particles.

[0009] In the aforementioned numerical simulation method for the partial discharge decomposition mechanism of an environmentally friendly insulating gas, the electron transport parameters and energy transfer coefficients are obtained by solving the Boltzmann equation. Here, the electron distribution function f in the six-dimensional phase space (r, v) satisfies:

[0010]

[0011] Where v is the electron velocity, e is the electron charge, r is the position parameter, and m is the electron velocity. e is the electron mass, C[f] represents the collision term of f due to electron collision, are the gradient operators for space and velocity respectively

[0012] In the above-mentioned numerical simulation method for the partial discharge decomposition mechanism of an environmentally friendly insulating gas, the relevant reaction path parameters required by the plasma chemical reaction model are obtained by the following method:

[0013] Construct a molecular structure model of environmentally friendly insulating gas and use quantum chemistry density functional theory (DFT) to perform molecular structure relaxation calculations to obtain bond length and bond angle parameters;

[0014] Calculate the structural characteristics of relaxed gas molecules, and based on the calculation results, obtain the chemical bond breakage sites and reaction activity in the molecular structure, based on which the possible decomposition paths of environmentally friendly insulating gas molecules can be constructed;

[0015] Perform structural relaxation and energy and electronic property calculations on various reactant and product particles involved in the constructed reaction pathway;

[0016] The energy of the product particles in the decomposition path is subtracted from the energy of the reactant particles to obtain the enthalpy value and Gipps free energy of the reaction path; transition state and rate analysis is performed on the reactants and products involved in the decomposition path of gas molecules to obtain the transition state structure, reaction activation energy, reaction rate and equilibrium constant.

[0017] In the above-mentioned numerical simulation method for the partial discharge decomposition mechanism of an environmentally friendly insulating gas, the plasma chemical reaction model includes impact ionization, adsorption reaction, composite reaction, chemical reaction, and surface reaction, wherein,

[0018] Impact ionization is the main cause of the generation of electrons and decomposition particles in partial discharge of environmentally friendly insulating gases. Its reaction equation is written based on the participation of environmentally friendly insulating gas molecules and electrons. The reactants are molecules and electrons, and the products are positive ions, electrons, free radicals, etc.

[0019] Adsorption reaction is the main cause of electron disappearance. Its reaction equation is written based on the participation of environmentally friendly insulating gas molecules and electrons. The reactants are molecules and electrons, and the products are negative ions, free radicals, etc.

[0020] The impact ionization and adsorption reactions are the two most important reactions that affect the development of partial discharge in environmentally friendly insulating gases.

[0021] The composite reaction is a process in which positive ions and negative ions react to produce neutral particles. It is listed according to the types of ions produced by the decomposition of environmentally friendly insulating gases.

[0022] Chemical reactions are reactions without considering the participation of electrons and are listed based on the free radicals produced by the decomposition of environmentally friendly insulating gases;

[0023] Surface reactions are reactions that occur between reactants and solid (non-metal, metal) surfaces without considering the participation of electrons. They are listed based on the interface structure between environmentally friendly insulating gas molecules / free radicals and solids.

[0024] In the above-mentioned numerical simulation method for the partial discharge decomposition mechanism of an environmentally friendly insulating gas, the fluid dynamics model includes:

[0025] Particle continuity equation: The continuity equation is used to describe the transfer behavior of conserved quantities of various particles during partial discharge of environmentally friendly insulating gases, including but not limited to charge and mass.

[0026] Electron average energy equation: used to describe the energy distribution characteristics of free electrons during partial discharge.

[0027] Poisson's equation: used to describe the potential distribution during the discharge process of environmentally friendly insulating gas.

[0028] In the above-mentioned numerical simulation method for the partial discharge decomposition mechanism of environmentally friendly insulating gas, the particle continuity equation in the fluid dynamics model includes the electron continuity equation, the anion and cation continuity equation, and the neutral particle continuity equation. Among them, the electron continuity equation is:

[0029]

[0030] Among them, S α is the environmentally friendly insulating gas impact ionization term, S η is the adsorption reaction term, S0 is the electron initial term, S det is the photoionization term.

[0031] The continuity equations for anions, cations and neutral particles are:

[0032]

[0033] Among them, R k is the heavy particle (cation and anion and neutral particle) source term, is the flux of heavy particles, divided into:

[0034]

[0035] Where D k is the diffusion tensor of heavy particles, μ k is the ion mobility tensor

[0036] In the above-mentioned numerical simulation method for the partial discharge decomposition mechanism of environmentally friendly insulating gas, the electron average energy equation in the fluid dynamics model is:

[0037]

[0038] Where, Γ ε is the average electron energy flux, S ε is the source term of the average electron energy, is the average energy of the electron.

[0039] In the above-mentioned numerical simulation method for the partial discharge decomposition mechanism of environmentally friendly insulating gas, the expression of the Poisson equation in the fluid dynamics model is:

[0040]

[0041] Where, ε r and ε0 are the relative permittivity and vacuum permittivity, respectively, is the electric potential, n p 、n n 、n e are the concentrations of cations, anions and electrons in environmentally friendly insulating gases, respectively.

[0042] In the above-mentioned numerical simulation method for the partial discharge decomposition mechanism of an environmentally friendly insulating gas, the solution area of the fluid dynamics model under the typical needle-plate electrode partial discharge model is abcde, where ab is the symmetry axis, ae is the needle electrode surface, bc is the plate electrode surface, and edc is the open boundary.

[0043] In the above-mentioned numerical simulation method for the partial discharge decomposition mechanism of an environmentally friendly insulating gas, in the fluid dynamics model, the boundary conditions corresponding to the particle continuity equation, the electron average energy transfer equation, and the Poisson equation are as follows:

[0044] Open boundary conditions, open boundary edc adopts Farouk's voltage zero discharge boundary condition;

[0045] The condition of the electron average energy equation at the open boundary is:

[0046]

[0047] Boundary conditions at the electrodes: The boundary conditions satisfied by the average electron energy flux at the electrodes are:

[0048]

[0049] Here, a DC voltage of -V is applied to the needle electrode, and the potential on the plate electrode is set to zero.

[0050] The hybrid numerical model solution for the numerical simulation of the partial discharge decomposition mechanism of environmentally friendly insulating gas can reveal the generation and movement laws of particles such as electrons, cations, anions and neutral particles during the partial discharge process, as well as the influence of different external conditions (gas pressure, mixing ratio, temperature) on them.

[0051] Compared with the existing technology, the present invention has the following advantages and beneficial effects: 1. The present invention can reveal the partial discharge decomposition mechanism of environmentally friendly insulating gases from a theoretical level, especially the proposed chemical-fluid dynamics gas partial discharge microscopic characteristics hybrid model can reveal the generation law and spatiotemporal evolution distribution characteristics of electrons, anions, cations and neutral particles under the action of PD pulse current from a microscopic level. 2. The present invention can obtain the PD discharge decomposition mechanism of environmentally friendly insulating gases, including thermodynamic parameters such as decomposition path, reaction enthalpy, activation energy, reaction rate, and analyze the generation law of steady-state decomposition products. 3. The technical solution proposed in the present invention can be used to study the PD decomposition mechanism of various environmentally friendly insulating gases without conducting a large number of experiments. It can evaluate the microscopic change mechanism of PD discharge components of environmentally friendly insulating gases and has broad application prospects in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Attachment Figure 1 It is the relationship diagram of the hybrid numerical model of partial discharge;

[0053] Attachment Figure 2 It is the schematic diagram of the needle-plate electrode PD and the boundary condition diagram of the model;

[0054] Attachment Figure 3 This is the flow chart for solving the chemical-fluid dynamics PD hybrid numerical model;

[0055] Attachment Figure 4 is a schematic diagram of the electron energy distribution function;

[0056] Attachment Figure 5 It is a schematic diagram of the C6F12O relaxor molecular structure;

[0057] Attachment Figure 6 This is a schematic diagram of the distribution of C6F12O molecular orbital wave functions;

[0058] Attachment Figure 7 This is a schematic diagram of the decomposition path and reaction enthalpy of C6F12O;

[0059] Attachment Figure 8 This is a schematic diagram of the reaction rate of the decomposition path of C6F12O;

[0060] Attachment Figure 9 is a schematic diagram of the mesh division of the numerical model;

[0061] Attachment Figure 10 It is a schematic diagram of the change of average electron energy;

[0062] Attachment Figure 11 It is a schematic diagram of the changes in the number density of electrons and cations;

[0063] Attachment Figure 12 This is a schematic diagram of the change in particle generation with discharge energy. DETAILED DESCRIPTION

[0064] The present invention is further described below by way of examples.

[0065] 1. First, the principle of the method of the present invention is introduced.

[0066] 1. A computational simulation method for the decomposition mechanism of environmentally friendly insulating gas, the core of which is to use a gas partial discharge hybrid model based on chemical-fluid dynamics. This model can reveal the generation and movement laws of various particles under partial discharge through high-precision quantum chemistry and numerical solution. The main components of the hybrid model are shown in the attached figure. Figure 1 As shown in the figure, specifically, first, the parameters such as electron transport parameters and energy transfer coefficients are solved; secondly, the plasma chemical reaction model is used to study the ionization decomposition process of environmentally friendly insulating gas, providing control items such as electron source term, heavy ion source term and ion energy term for the fluid dynamics model; finally, the fluid dynamics model is used to study the convective motion distribution law of particles.

[0067] 2. The electron transport parameters and energy transfer coefficients can be obtained by solving the Boltzmann equation. Specifically, the electron distribution function f in the six-dimensional phase space (r, v) satisfies:

[0068]

[0069] Where v is the electron velocity, e is the electron charge, r is the position parameter, and m is the electron velocity. e is the electron mass, C[f] represents the collision term of f due to electron collision, are the gradient operators of space and velocity, respectively. Preferably, the calculation of formula (2.1) can be simplified by spherical coordinate transformation, and then the EEDF can be obtained.

[0070] 3. The plasma chemical reaction model includes chemical reaction processes such as collision ionization and adsorption reaction. The relevant reaction path parameters (enthalpy, reaction rate) required by the model can be obtained by the following method:

[0071] First, a molecular structure model of the environmentally friendly insulating gas is constructed and quantum chemical density functional theory (DFT) is used to perform molecular structure relaxation calculations to obtain parameters such as bond length and bond angle.

[0072] Secondly, the structural characteristics of the relaxed gas molecules are calculated, including but not limited to chemical bond order and frontier molecular orbitals. Based on the calculation results, the chemical bond breakage sites and reactivity in the molecular structure are evaluated, and the possible decomposition paths of the environmentally friendly insulating gas molecules are constructed based on these results.

[0073] Subsequently, structural relaxation, energy, and electronic properties calculations were performed on various reactant and product particles involved in the constructed reaction pathway.

[0074] Finally, the energy of the reactant particles in the decomposition path is subtracted from the energy of the product particles to obtain the enthalpy and Gibbs free energy of the reaction path. Transition state and rate analysis is performed on the reactants and products involved in the gas molecule decomposition path to obtain the transition state structure, reaction activation energy, reaction rate, equilibrium constant, etc. Through these calculations and analyses, various basic reaction parameters required for plasma chemical reaction model calculations can be obtained.

[0075] 4. The fluid dynamics model mainly includes the particle continuity equation, the electron average energy equation and the Poisson equation. Specifically,

[0076] 1) The particle continuity equation mainly includes the electron continuity equation, the anion and cation continuity equation, and the neutral particle continuity equation. Among them, the electron continuity equation is:

[0077]

[0078] Among them, S α is the impact ionization term, S η is the impact ionization term, S0 is the electron initial term, S det is the photoionization term.

[0079] The continuity equations for anions, cations and neutral particles are:

[0080]

[0081] Among them, R k is the heavy particle (cation and anion and neutral particle) source term, is the flux of heavy particles, divided into:

[0082]

[0083] Where D k is the diffusion tensor of heavy particles, μ k is the ion mobility tensor

[0084] 2) The electron average energy equation is:

[0085]

[0086] Where, Γ εis the average electron energy flux, S ε is the source term of the average electron energy, is the average energy of the electron.

[0087] 3) Poisson's equation is used to describe the potential distribution during the discharge process, and its expression is:

[0088]

[0089] Where, ε r and ε0 are the relative permittivity and vacuum permittivity, respectively, is the electric potential, n p 、n n 、n e are the concentrations of cations, anions, and electrons, respectively.

[0090] 4) In the fluid dynamics model, the boundary conditions corresponding to the particle continuity equation, the electron average energy transfer equation, and the Poisson equation are divided into open boundary conditions ( Figure 2 EDC) and the boundary conditions at the electrodes (see Figure 2 There are two types of electrodes (needle and plate electrodes). In this case, a DC voltage of -V is applied to the needle electrode, the potential on the plate electrode is set to zero, and the open boundary EDC adopts Farouk's zero voltage discharge boundary condition; the boundary condition satisfied by the average electron energy flux at the electrode is:

[0091]

[0092] The condition of the electron average energy equation at the open boundary is:

[0093]

[0094] 5. The chemical-fluid dynamics gas partial discharge microscopic characteristics hybrid model can be realized through the COMSOL Multiphysics platform. The solution flow chart is shown in the attached figure. Figure 3 Specifically, considering that the needle-plate electrode has good axial symmetry, a two-dimensional axisymmetric model can be used for solution. Preferably, the solution of the needle-plate electrode size and solution domain is as shown in the attached figure. Figure 2 As shown in abcde, ab is the symmetry axis, ae is the needle electrode surface, bc is the plate electrode surface, and edc is the open boundary.

[0095] 6. The core concept of the numerical simulation method for the partial discharge decomposition mechanism of environmentally friendly insulating gases is to solve parameters such as electron transport parameters and energy transfer coefficients using the Boltzmann equation. A plasma chemical reaction model is used to study the ionization and decomposition process of environmentally friendly insulating gases and provide electron and heavy particle source terms. A fluid dynamics model is used to study the motion and distribution patterns of electrons, anions, cations, and neutral particles during the PD process. The following is a specific gas analysis example using this method.

[0096] Example 1: Environmentally friendly insulating gas C6F 12 O partial discharge decomposition mechanism

[0097] 1. Solve the electron transport parameters and energy transfer coefficient. These parameters can be obtained by solving the Boltzmann equation. Consider that the electron distribution function f in the six-dimensional phase space (r, v) satisfies:

[0098]

[0099] Where v is the electron velocity, e is the electron charge, r is the position parameter, and m is the electron velocity. e is the electron mass, C[f] represents the collision term of f due to electron collision, are the gradient operators of space and velocity respectively. By calculating the simplified formula (S1) of spherical coordinate transformation, we can get:

[0100]

[0101] Where z is the direction of the electric field intensity, and θ is the angle between the electric field intensity and the electron velocity.

[0102] The EEDF is expanded in spherical coordinates as follows:

[0103] f≈f0+f1cosθ (S3) Where f0 is the isotropic part of the EEDF and f1 is the anisotropic part of the EEDF. By multiplying by the Legendre polynomial coefficients and integrating the angle θ between the electric field intensity and the electron velocity, we can obtain:

[0104]

[0105]

[0106] Where C0 is the change in EEDF caused by electron collision, and N is the molecular number density.

[0107] The EEDF obtained is as follows Figure 4 As shown in Figure 2, it can be seen that when the average electron energy is constant, the higher the energy carried by the electron, the smaller its proportion.

[0108] 2. Construction of a plasma chemical reaction model. This model includes chemical reaction processes such as collision ionization and adsorption reactions. The relevant reaction path parameters (enthalpy, reaction rate) required by the model are obtained by density functional theory (DFT) calculations.

[0109] First, a molecular structure model of the environmentally friendly insulating gas to be analyzed was constructed, and DFT was used to perform molecular structure optimization calculations. The convergence parameters of the structural relaxation optimization were: energy, 1.0×10 -5 Ha, displacement, gradient DNP numerical basis set; B3LYP is selected as the exchange-correlation functional, and the obtained relaxed molecular structure is shown in the attached figure. Figure 5 Secondly, the structural characteristics of the gas molecules after geometry optimization, namely the frontier molecular orbitals (see Figure 6 As shown), we can see that the HOMO and LUMO wave functions are mainly distributed in C6F 12 The carbon atom near the center of the O molecule indicates that the reaction activity near the central carbon atom is higher.

[0110] Subsequently, C6F was constructed 12 The O decomposition reaction path was modeled and various reactants and product particles involved in the path were modeled. DFT was used to perform structural relaxation optimization and obtain energy and electronic properties. The convergence parameters for structural optimization were energy, 1.0×10 -5 Ha, displacement, gradient The DNP numerical basis set is selected as the basis set, and the exchange-correlation functional is selected as B3LYP. Then, the enthalpy of the gas decomposition path is solved based on the results of the particle-related thermodynamics and electronic properties calculations, as shown in the attached figure. Figure 7 As shown in the figure; conduct transition state analysis on the decomposition path of gas molecules to obtain activation energy, reaction rate and equilibrium constant, as shown in the figure. Figure 8 Through the above calculation and analysis, various basic parameters required for plasma chemical reaction calculation can be obtained.

[0111] 3. Fluid dynamics model solution:

[0112] Fluid dynamics solutions mainly include particle continuity equations, electron average energy equations, and Poisson equations. Specifically,

[0113] 1) The particle continuity equation mainly includes the electron continuity equation, the anion and cation continuity equation, and the neutral particle continuity equation. Among them, the electron continuity equation is:

[0114]

[0115] Among them, S α is the impact ionization term, S ηis the impact ionization term, S0 is the electron initial term, S det is the photoionization term.

[0116] The continuity equations for anions, cations and neutral particles are:

[0117]

[0118] Among them, R k is the heavy particle (cation and anion and neutral particle) source term, is the flux of heavy particles, divided into:

[0119]

[0120] Where D k is the diffusion tensor of heavy particles, μ k is the ion mobility tensor.

[0121] 2) The electron average energy equation is:

[0122]

[0123] Where, Γ ε is the average electron energy flux, S ε is the source term of the average electron energy, is the average energy of the electron.

[0124] The average electron energy flux is:

[0125]

[0126] Wherein, the electron average energy diffusion coefficient and mobility are:

[0127]

[0128]

[0129] 3) Poisson's equation is used to describe the potential distribution during the discharge process, and its expression is:

[0130]

[0131] Where ε and ε0 are the relative dielectric constant and the vacuum dielectric constant, respectively. is the electric potential, n p 、n n 、n e are the concentrations of cations, anions, and electrons, respectively.

[0132] 4) In the fluid dynamics model, the boundary conditions corresponding to the particle continuity equation, the electron average energy transfer equation, and the Poisson equation are divided into open boundary conditions ( Figure 2 EDC) and the boundary conditions at the electrodes (see Figure 2 There are two types of electrodes (needle and plate electrodes). In this case, a DC voltage of -V is applied to the needle electrode, the potential on the plate electrode is set to zero, and the open boundary EDC adopts Farouk's zero voltage discharge boundary condition; the boundary condition satisfied by the average electron energy flux at the electrode is:

[0133]

[0134] The condition of the electron average energy equation at the open boundary is:

[0135]

[0136] 4. The chemical-fluid dynamics hybrid model of gas partial discharge microscopic characteristics is implemented using the COMSOL Multiphysics platform. Considering that the needle-plate electrode has good axisymmetry, this example uses a two-dimensional axisymmetric model to solve (the flowchart is attached). Figure 3 ). Figure 2 The solution region abcde is given, where ab is the symmetry axis, ae is the needle electrode surface, bc is the plate electrode surface, and edc is the open boundary. Since the discharge in the PD process mainly develops along the symmetrical direction toward the plate electrode, and the anions and cations react on the plate electrode, the particle number density changes along the symmetry axis and the electrode surface area with a large gradient. In the meshing, a larger meshing density is selected for the above region, as shown in the attached figure. Figure 9 In addition, during the model solution process, the time step is automatically determined by the COMSOL platform based on the error tolerance and tolerance factor.

[0137] 6. The main results obtained by using this model include the average electron energy and electron density distribution (see Appendix Figure 10 ), the number density distribution of electrons, anions and cations (attached Figure 11 ), the characteristics of particle generation amount changing with discharge energy, etc. (Appendix Figure 12 The average electron energy and electron density distributions show a decreasing trend with increasing distance from the needle electrode surface, indicating that the region of extremely high average electron energy is located near the needle tip. The electron number density increases during the PD development phase, while decreasing during the PD pulse current decline phase, gradually moving away from the symmetry axis. Furthermore, cations and anions migrate along the symmetry axis toward the plate electrode as the PD develops. The amount of primary particles generated also increases with increasing discharge energy.

[0138] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A numerical simulation method for the partial discharge decomposition mechanism of environmentally friendly insulating gas, characterized in that: For the environmentally friendly insulating gas to be analyzed, the electron transport parameters and energy transfer coefficient parameters are first solved; Secondly, the plasma chemical reaction model is used to ionize and decompose the environmentally friendly insulating gas to obtain the electron source term, heavy ion source term, and ion energy term; Finally, based on the obtained electron source term, heavy ion source term and ion energy term control terms, the convective motion distribution of particles is obtained using the fluid dynamics model; The particle continuity equations in the fluid dynamics model include the electron continuity equation, the anion and cation continuity equations, and the neutral particle continuity equations. The electron continuity equation is: in, It is the environmentally friendly insulating gas collision ionization item, is the adsorption reaction term, is the electron initial term, is the photoionization term; The continuity equations for anions, cations and neutral particles are: in, is the heavy particle (cation and anion and neutral particle) source term, is the flux of heavy particles, divided into: Where, D k is the diffusion tensor of heavy particles, is the ion mobility tensor; The electron average energy equation in the fluid dynamics model is: Where, is the average electron energy flux, is the source term of the average electron energy, is the average electron energy; The expression of Poisson's equation in the fluid dynamics model is: Where, and are the relative permittivity and the vacuum permittivity, is the electric potential, 、 、 are the concentrations of cations, anions and electrons in environmentally friendly insulating gases, respectively.

2. The numerical simulation method for partial discharge decomposition mechanism of environmentally friendly insulating gas according to claim 1 is characterized in that: The electron transport parameters and energy transfer coefficients are obtained by solving the Boltzmann equation; where the electron distribution function in the six-dimensional phase space (r, v) is f satisfy: Where, v is the electron speed, e is the electron charge, r is a positional parameter, m e is the mass of the electron, C[ f ] indicates the electron collision f The collision term, 、 are the spatial and velocity gradient operators respectively.

3. The numerical simulation method for partial discharge decomposition mechanism of environmentally friendly insulating gas according to claim 1 is characterized in that: The relevant reaction path parameters required for the plasma chemical reaction model are obtained by the following method: Construct a molecular structure model of environmentally friendly insulating gas and use quantum chemistry density functional theory (DFT) to perform molecular structure relaxation calculations to obtain bond length and bond angle parameters; Calculate the structural characteristics of relaxed gas molecules, and based on the calculation results, obtain the chemical bond breakage sites and reaction activity in the molecular structure, based on which the possible decomposition paths of environmentally friendly insulating gas molecules can be constructed; Perform structural relaxation and energy and electronic property calculations on various reactant and product particles involved in the constructed reaction pathway; The energy of the product particles in the decomposition path is subtracted from the energy of the reactant particles to obtain the enthalpy value and Gipps free energy of the reaction path; transition state and rate analysis is performed on the reactants and products involved in the decomposition path of gas molecules to obtain the transition state structure, reaction activation energy, reaction rate and equilibrium constant.

4. The numerical simulation method for partial discharge decomposition mechanism of environmentally friendly insulating gas according to claim 1 is characterized in that: The plasma chemical reaction model includes impact ionization, adsorption reaction, composite reaction, chemical reaction, and surface reaction, wherein: The impact ionization reaction equation is written based on the participation of environmentally friendly insulating gas molecules and electrons. The reactants are molecules and electrons, and the products are positive ions, electrons, and free radicals. The reaction equation of the adsorption reaction is written based on the participation of environmentally friendly insulating gas molecules and electrons. The reactants are molecules and electrons, and the products are negative ions and free radicals. The composite reaction is a process in which positive ions and negative ions react to produce neutral particles. It is listed according to the types of ions produced by the decomposition of environmentally friendly insulating gases. Chemical reactions are reactions without considering the participation of electrons and are listed based on the free radicals produced by the decomposition of environmentally friendly insulating gases; Surface reactions are reaction processes that occur between reactants and the surfaces of non-metallic solids or metallic solids without considering the participation of electrons. They are listed based on the interface structure between environmentally friendly insulating gas molecules / free radicals and solids.

5. The method for numerical simulation of partial discharge decomposition mechanism of environmentally friendly insulating gas according to claim 1, characterized in that: The solution region of the fluid dynamics model in the typical needle-plate electrode partial discharge model is abcde, where ab is the symmetry axis, ae is the needle electrode surface, bc is the plate electrode surface, and edc is the open boundary.

6. The numerical simulation method for partial discharge decomposition mechanism of environmentally friendly insulating gas according to claim 1 is characterized in that: In the fluid dynamics model, the boundary conditions corresponding to the particle continuity equation, the electron average energy transfer equation, and the Poisson equation are as follows: Open boundary conditions, open boundary edc adopts Farouk's voltage zero discharge boundary condition; The condition of the electron average energy equation at the open boundary is: Boundary conditions at the electrodes: The boundary conditions satisfied by the average electron energy flux at the electrodes are: Wherein, the potential is applied on the needle electrode- V The DC voltage is set to zero on the plate electrodes; The hybrid numerical model solution for numerical simulation of partial discharge decomposition mechanism of environmentally friendly insulating gas can obtain the particle generation and motion laws of electrons, cations, anions and neutral particles in the partial discharge process, as well as the influence of different external conditions on them.

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