Method for calculating heavy gas oil flow in turn-to-turn short circuit fault in transformer based on gas-liquid-solid coupling

Abstract

The invention discloses a transformer internal turn-to-turn short circuit fault heavy gas oil flow calculation method based on gas-liquid-solid coupling. The method comprises the following steps: step (1), establishing a 1: 1 equivalent power transformer three-dimensional simulation model; (2) solving an energy input condition of a turn-to-turn short circuit fault in the transformer by utilizing field-circuit coupling; step (3), importing the three-dimensional calculation model into ANSYS Fluent software, initializing and loading grid information, and selecting a proper turbulence model and a wall surface function; (4) setting a solid mechanical calculation model in ANSYS Fluent software, realizing fluid-solid coupling calculation, and calculating a heavy gas oil flow surging result in the transformer oil tank under the arc fault; according to the invention, the heavy gas oil flow distribution rule under the internal arc fault of the transformer can be revealed.

Description

Technical Field

[0001] The present invention relates to the technical field of non-electrical protection of power system transformers, and particularly relates to a calculation method for heavy gas oil flow in internal turn-to-turn short circuit faults of transformers based on gas-liquid-solid coupling. Background Art

[0002] Power transformers are key equipment in the power system, and their safe operation is of vital importance. The gas relay, as the core component of the transformer protection system, is mainly used to detect the gas and heavy gas oil flow generated during internal faults of the transformer. In recent years, the number of accidents where transformers equipped with gas protection explode and catch fire during internal faults has increased, but existing research has not fully revealed the spatio-temporal coupling law between bubble dynamics and oil flow characteristics. Due to the high cost and safety risks associated with directly conducting internal fault experiments on transformers, existing research mainly relies on theoretical modeling and numerical simulation. However, existing theoretical models fail to accurately describe the morphological evolution of gas bubbles in the gas relay and the dynamic characteristics of the oil flow they trigger. Therefore, studying the characteristics of heavy gas oil flow under internal fault conditions of transformers has important theoretical significance. This not only helps to reveal the generation and migration mechanism of fault gas, but also provides key theoretical support for optimizing transformer protection strategies and improving fault identification accuracy. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above deficiencies and provide a calculation method for heavy gas oil flow in internal turn-to-turn short circuit faults of transformers based on gas-liquid-solid coupling, which can reveal the distribution law of heavy gas oil flow under internal arc faults of transformers.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is: a calculation method for heavy gas oil flow in internal turn-to-turn short circuit faults of transformers based on gas-liquid-solid coupling, which includes the following steps: Step (1), establish a 1:1 equivalent three-dimensional simulation model of a power transformer; Step (2), use field-circuit coupling to solve the energy input conditions for internal turn-to-turn short circuit faults of the transformer; Step (3), import the three-dimensional calculation model into ANSYS Fluent software, initialize and load the grid information, and select an appropriate turbulence model and wall function; Step (4), set a solid mechanics calculation model in ANSYS Fluent software to achieve fluid-structure interaction calculation, and calculate the surging result of heavy gas oil flow inside the transformer tank under arc faults.

[0005] Preferably, in step (1), SolidWorks is used to establish a 1:1 equivalent three-dimensional simulation model of a power transformer.

[0006] Preferably, the power transformer in the step (1) is an oil-immersed power transformer, which is filled with insulating oil inside.

[0007] Preferably, the step (2) specifically includes the following contents: Step (2.1): Establish mathematical models for the external circuit topology of the turn-to-turn short circuit and the internal electromagnetic field of the transformer one by one. According to Maxwell's equations, the matrix form of the internal magnetic field control equation of the converter transformer is: ; In the formula, is the axial magnetic potential component, H , Q , D are all coefficient matrices, j is the exciting current flowing into the winding; in the external circuit, the induced voltage of the winding is described as: ; In the formula, k is the eddy current correction coefficient, R T and L T respectively represent the total resistance and total inductance in the solution loop, l is the axial equivalent length, N represents the number of turns of the winding coil, S c represents the cross-sectional area of the wire, A e represents the equivalent magnetic circuit cross-sectional area of the winding, is the integration region; Step (2.2): In the fault loop, use the Mayr model to calculate the arc current and arc voltage, and its differential equation is: ; In the formula, g arc is the arc conductance, u arc and i arc are the arc voltage and arc current respectively. The time constant of the Mayr arc , according to the assumption conditions of the Mayr model, its dissipated power P loss is a constant; The main influencing factors of the arc energy are the arc current, arc voltage and arc duration, and its calculation formula is: ; In the formula, is the time variable.

[0008] Preferably, step (3) specifically includes the following contents: Step (3.1): Import the three-dimensional calculation model into ANSYS Fluent software; Step (3.2): Initialize and load the mesh information; Step (3.3): Select a suitable turbulence model; Step (3.4): Calculate the bubble-liquid boundary velocity under arc fault; Step (3.5): Update the instantaneous fluid field using dynamic mesh; Step (3.6): Solve the heavy gas oil flow velocity through the momentum equation and turbulence model.

[0009] Preferably, the calculation formula for calculating the bubble-liquid boundary velocity under arc fault in step (3.4) is: ; In the formula, R is the bubble radius, is the bubble velocity, is the bubble acceleration, c is the straight-line distance from the fluid boundary to the bubble wall boundary, P c is the pressure at the fluid boundary, ρ is the density, W arc is the arc energy, α is the energy conversion coefficient, μ is the liquid viscosity coefficient, γ is the specific heat ratio, t 0 is the initial time, t is the time, p c is the pressure at the fluid boundary, is the historical time variable.

[0010] Preferably, the calculation formula for updating the instantaneous fluid field using dynamic mesh in step (3.5) is: ; In the formula, u is the velocity vector, is the gradient of the transported physical quantity dA is the area differential vector, is the control volume boundary, V is the control volume, is the diffusion coefficient, represents the source term of, u g is the mesh velocity of the moving mesh.

[0011] Preferably, the calculation formula of the momentum equation in the step (3.6) is as follows: ; In the formula, μ represents the dynamic viscosity, f represents the gravity, P is the pressure, and ▽ P represents the pressure gradient, represents the velocity vector of the fluid, represents the convection term, represents the viscous term.

[0012] Preferably, setting the solid mechanics calculation model in the ANSYS Fluent software in the step (4) includes the following steps: Step (4.1): Consider the deformation of the transformer solid material under the action of the liquid pressure load by using the stress-strain relationship of elasticity: ; In the formula, σ xx , σ yy , σ zz is x , y , z the normal stress in the σ yz , σ xz , σ xy direction; y - z , x - z , x - y The shear stress on the plane; is x , y , z the linear strain in the direction; E is the engineering shear strain; v is the Young's modulus of the solid material, p Step (4.2): Use the fluid-structure interaction model to describe the mechanical coupling between the two. The force exerted by the fluid on the solid can be coupled with the displacement field on the solid surface through the fluid surface pressure to obtain the displacement and stress fields of the solid; Step (4.4): The convergence condition is that the error value of the calculation results for two consecutive iterations is lower than the preset value; Step (4.5): Save the results of the heavy gas oil flow surge inside the transformer tank under arc fault.

[0013] Preferably, in the said step (4.2), the force exerted by the fluid on the solid is expressed by the equation: ; In the formula, f s is the force exerted by the fluid on the solid; n is the surface normal vector, S is the solid surface, p is the pressure.

[0014] Advantages of the present invention: 1. The present invention proposes an improved field - circuit coupling technology considering the macroscopic electrical characteristics of short - circuit arcs, providing accurate energy input conditions for simulating the oil flow surge in transformer turn - to - turn short - circuit faults; 2. The present invention proposes a bubble dynamics model for continuous injection of arc energy inside the transformer, depicting the non - linear relationship between energy release, oil pressure increase, and the evolution of gas - bubble morphology during short - circuit faults.

[0015] 3. The present invention proposes a gas - liquid - solid multi - field coupling calculation method, realizing the simulation of the characteristics of heavy gas oil flow caused by internal short - circuit faults in transformers; based on the established numerical calculation model, it can analyze the oil flow response under different fault conditions, providing a theoretical basis and data support for improving the gas protection strategy of transformers; 4. The present invention can reveal the distribution law of heavy gas oil flow under internal arc faults in transformers. Brief Description of the Drawings

[0016] Figure 1 It is a grid model diagram of a transformer according to an embodiment of the present invention; Figure 2 It is a diagram of the short - circuit circulating current, arc voltage, arc power, arc energy, and oil flow velocity results of the turn - to - turn short - circuit fault inside the transformer according to an embodiment of the present invention; Figure 3 It is a diagram of the oil flow surge results of the turn - to - turn short - circuit fault inside the transformer according to an embodiment of the present invention. Detailed Embodiment

[0017] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0018] Embodiment 1: The technical solution in the present invention is based on an in-depth understanding of the complex coupling relationship between the oil flow surge and the evolution of gas bubble morphology during the inter-turn short-circuit fault of the transformer. This technical solution comprehensively considers multiple physical fields such as arc fault, insulating oil flow field, and solid mechanics of the transformer tank and their interactions, providing a solid foundation for accurately simulating the heavy gas oil flow characteristics under the inter-turn short-circuit fault inside the transformer. By establishing a numerical calculation model of gas-liquid-solid multi-field coupling, the dynamic response of oil flow during the short-circuit fault can be accurately reflected, including the following steps: Step (1), establish a 1:1 equivalent three-dimensional simulation model of the power transformer; Step (2), use field-circuit coupling to solve the energy input conditions for the inter-turn short-circuit fault inside the transformer; Step (3), import the three-dimensional calculation model into ANSYS Fluent software, initialize and load the grid information, and select a suitable turbulence model and wall function; Step (4), set the solid mechanics calculation model in ANSYS Fluent software to achieve fluid-structure interaction calculation, and calculate the heavy gas oil flow surge results inside the transformer tank under the arc fault.

[0019] Preferably, in step (1), SolidWorks is used to establish a 1:1 equivalent three-dimensional simulation model of the power transformer.

[0020] Preferably, the power transformer in step (1) is an oil-immersed power transformer filled with insulating oil.

[0021] Preferably, step (2) specifically includes the following content: Step (2.1), establish a mathematical model for the external circuit topology of the inter-turn short-circuit and the internal electromagnetic field of the transformer one by one. According to Maxwell's equations, the matrix form of the internal magnetic field control equation of the converter transformer is: ; In the formula, is the axial magnetic potential component, H , Q , D are all coefficient matrices, j is the exciting current flowing into the winding; in the external circuit, the induced voltage of the winding is described as: ; In the formula, k is the eddy current correction coefficient, R T and L T respectively represent the total resistance and total inductance in the solution loop, l is the axial equivalent length, Nrepresents the number of turns of the winding coil, S c represents the cross-sectional area of the wire, A e represents the equivalent magnetic circuit cross-sectional area of the winding, is the integration region; Step (2.2): In the fault loop, use the Mayr model to calculate the arc current and arc voltage, and its differential equation is: ; In the formula, g arc is the arc conductance, u arc and i arc are the arc voltage and arc current respectively. The time constant of the Mayr arc , according to the assumption conditions of the Mayr model, its dissipated power P loss is a constant; The main influencing factors of the arc energy are the arc current, arc voltage and arc duration, and its calculation formula is: ; In the formula, is the time variable.

[0022] Preferably, the step (3) specifically includes the following contents: Step (3.1): Import the three-dimensional calculation model into ANSYS Fluent software; Step (3.2): Initialize and load the grid information; Step (3.3): Select a suitable turbulence model; Step (3.4): Calculate the bubble-liquid boundary velocity under arc fault; Step (3.5): Update the instantaneous fluid field using dynamic mesh; Step (3.6): Solve the heavy gas oil flow velocity through the momentum equation and turbulence model.

[0023] Preferably, the calculation formula for the bubble-liquid boundary velocity under arc fault in step (3.4) is: ; In the formula, R is the bubble radius, is the bubble velocity, is the bubble acceleration, c is the straight-line distance from the fluid boundary to the bubble wall boundary, P c is the pressure at the fluid boundary, ρ is the density,W arc is the arc energy, α is the energy conversion coefficient, μ is the liquid viscosity coefficient, γ is the specific heat ratio, t 0 is the initial time, t is the time, p c is the pressure at the fluid boundary, is the historical time variable.

[0024] Preferably, the calculation formula for updating the instantaneous fluid field using the dynamic mesh in step (3.5) is: ; In the formula, u is the velocity vector, is the physical quantity being transported gradient of, dA is the area differential vector, is the control volume boundary, V is the control volume, is the diffusion coefficient, represents source term of, u g is the mesh velocity of the moving mesh.

[0025] Preferably, the calculation formula for the momentum equation in step (3.6) is: ; In the formula, μ represents the dynamic viscosity, f represents the gravity, P is the pressure, ▽ P represents the pressure gradient, represents the velocity vector of the fluid, represents the convection term, represents the viscous term.

[0026] Preferably, setting the solid mechanics calculation model in ANSYS Fluent software in step (4) includes the following steps: Step (4.1), considering the deformation of the transformer solid material under the action of liquid pressure load using the stress-strain relationship of elasticity: ; In the formula, σ xx , σ yy , σ zz is x , y , zNormal stress in the direction; σ yz , σ xz , σ xy is y - z 、 x - z 、 x - y Shear stress in the plane; is x 、 y 、 z Linear strain in the direction; is the engineering shear strain; E is the Young's modulus of the solid material, v is the Poisson's ratio; Step (4.2), adopt a fluid-structure interaction model to describe the mechanical coupling between the two. The force exerted by the fluid on the solid can be coupled with the displacement field on the solid surface through the fluid surface pressure p to obtain the displacement and stress fields of the solid; Step (4.3), update the fluid field boundary conditions according to the solid mechanics calculation results and update the fluid field state until the convergence condition is satisfied; Step (4.4), the convergence condition is that the error value of the calculation results of two consecutive iterations is lower than the preset value; Step (4.5), save the results of the heavy gas oil flow surge inside the transformer tank under arc fault.

[0027] Preferably, in the step (4.2), the force exerted by the fluid on the solid is expressed by the equation: ; In the formula, f s is the force exerted by the fluid on the solid; n is the surface normal vector, S is the solid surface, p is the pressure.

[0028] Example 2: Refer to Figure 1 , taking the tank of a power transformer as the research object, for the 0.25% turn-to-turn short circuit fault occurring in the middle of the high-voltage side winding of the transformer, field-circuit coupling simulation calculation and arc fault gas-liquid-solid coupling calculation were carried out.

[0029] A method for calculating the heavy gas oil flow in the transformer internal turn-to-turn short circuit fault based on gas-liquid-solid coupling in this example includes the following steps: Step 1: Select SolidWorks to establish a 1:1 equivalent three-dimensional simulation model of the power transformer.

[0030] Step 2: Establish mathematical models for the external circuit topology of the turn-to-turn short circuit and the internal electromagnetic field of the transformer one by one. According to Maxwell's equations, the matrix form of the internal magnetic field control equation of the converter transformer is: ; In the formula, is the axial magnetic potential component, H , Q , D are all coefficient matrices, j is the exciting current flowing into the winding; in the external circuit, the induced voltage of the winding is described as: ; In the formula, k is the eddy current correction coefficient, R T and L T respectively represent the total resistance and total inductance in the solution loop, l is the axial equivalent length, N represents the number of turns of the winding coil, S c represents the cross-sectional area of the wire, A e represents the equivalent magnetic circuit cross-sectional area of the winding, is the integration region; represents the number of turns of the winding coil, a represents the cross-sectional area of the wire, and Sw represents the equivalent magnetic circuit cross-sectional area of the winding.

[0031] In the fault loop, the Mayr model is used to calculate the arc current and arc voltage, and its differential equation is: ; In the formula, g arc is the arc conductance, u arc and i arc are the arc voltage and arc current respectively. The time constant of the Mayr arc , according to the assumption conditions of the Mayr model, its dissipated power P loss is a constant; Step 3: Calculate the arc energy according to the results of the short-circuit circulating current and arc voltage calculated by the field-circuit coupling: ; In the formula, τ is the time variable.

[0032] Step 4: Taking the arc energy as the input, calculate the bubble-liquid boundary velocity under the arc fault according to the bubble dynamics equation. The bubble dynamics calculation formula is as follows: ; In the formula, R is the bubble radius, is the bubble velocity, is the bubble acceleration, c is the straight-line distance from the fluid boundary to the bubble wall boundary, P c is the pressure at the fluid boundary, ρ is the density, W arc is the arc energy, α is the energy conversion coefficient, μ is the liquid viscosity coefficient, γ is the specific heat ratio, t 0 is the initial time, t is the time.

[0033] Step 5: Update the boundary conditions of the internal insulating oil flow field of the transformer according to the bubble-liquid boundary velocity, and use the dynamic mesh technology to update and solve the instantaneous fluid field. The calculation formula is as follows:

[0034] In the formula, u is the flow velocity vector, is the physical quantity being transported is the gradient of, dA is the area differential vector, is the control volume boundary, V is the control volume, is the diffusion coefficient, represents the source term of, u g is the mesh velocity of the moving mesh.

[0035] Step 6: Solve the updated insulating oil flow field through the momentum equation and the turbulence model to obtain the heavy gas oil flow velocity and pressure. The calculation formula of the momentum equation is as follows:

[0036] In the formula, μ represents the dynamic viscosity, f represents the gravity, P is the pressure, ▽ P represents the pressure gradient, represents the velocity vector of the fluid, represents the convection term, represents the viscous term.

[0037] The turbulence model adopts A model, whose transport equation is:

[0038]

[0039] where is the turbulent kinetic energy, is the energy dissipation rate, and are the turbulent Prandtl numbers respectively, is the fluid mixture density, is the fluid molecular viscosity, is the fluid flow velocity, is the correction term.

[0040] The specific expression of

[0041] where , , .

[0042] Step 7: Import the pressure load of the insulating oil flow field into the solid mechanics calculation model. The fluid-structure interaction (FSI) model is used to describe the mechanical coupling between the two. The force exerted by the fluid on the solid can be coupled with the displacement field on the solid surface through the fluid surface pressure p to obtain the displacement and stress fields of the solid. The equation is:

[0043] In the formula, f s is the force exerted by the fluid on the solid; n is the surface normal vector, S is the solid surface, p is the pressure.

[0044] Step 8: Consider the deformation of the transformer solid material under the liquid pressure load by using the stress-strain relationship of elasticity: ; In the formula, σ xx , σ yy , σ zz is x , y , z the normal stress in the σ yz , σ xz, σ xy For y - z 、 x - z 、 x - y the shear stress in the plane; is x 、 y 、 z the linear strain in the direction; is the engineering shear strain; E is the Young's modulus of the solid material, v is the Poisson's ratio; Step 9: Update the fluid field boundary conditions according to the calculation results of solid mechanics, and update the state of the fluid field until the convergence condition is met. The convergence condition is that the error value of the calculation results of two consecutive iterations is lower than the preset value. If the convergence condition is not met, repeat steps 4 to 8.

[0045] Step 10: Record the calculation results and conduct an analysis of the simulation results.

[0046] To explore the oil flow surge mechanism and flow characteristics under the internal short-circuit fault of the transformer, the present invention proposes an internal short-circuit fault model of the transformer, aiming to simulate the energy release of the short-circuit fault, the pulsation of gas bubbles, and the resulting dynamic changes in oil flow. At the same time, it breaks through the multi-field coupling calculation method of gas-liquid-solid, and successfully solves the problem that previous simulations are difficult to accurately depict the pulsation of gas bubbles and the resulting oil flow characteristics under the internal short-circuit fault of the transformer.

[0047] Figure 2 and Figure 3 are the simulation calculation results of the specific embodiments. Figure 2 are the diagrams of the short-circuit circulating current, arc voltage, arc power, arc energy, and oil flow velocity for the 0.25% turn-to-turn short-circuit fault inside the transformer. Figure 3 is the diagram of the oil flow surge result for the 0.25% turn-to-turn short-circuit fault inside the transformer. From Figure 2 it can be seen that the arc voltage shows a typical saddle shape, and the average voltage during stable arcing is 58.46 V, and the peak value of the turn-to-turn short-circuit current reaches 1100.43 kA. From the second sub-diagram, it can be observed that the arc energy increases in an approximately linear manner after the fault occurs, and within 80 ms after the fault, the released arc energy reaches 3.121 MJ. The oil flow velocity shows a sharp upward trend at the initial stage of the fault, and then reaches a peak value, indicating that the oil flow in the connecting pipe of the transformer conservator is very sensitive to the internal short-circuit fault with a small number of turns. After the oil flow velocity reaches the peak value, it then shows a certain degree of decline, and this change is closely related to the process of bubble expansion inside the transformer.

[0048] Figure 3Revealed the dynamic behavior of oil flow surging during the short-circuit fault process and its spatial distribution law. For the calculation results of the oil flow field of the 0.25% turn-to-turn short-circuit fault of the transformer, numerical simulation shows the evolution characteristics of the oil flow field at different time points. In the initial stage of the fault, under the action of arc energy, gas bubbles are rapidly generated, resulting in a sharp rise in the oil flow velocity near the fault point, forming a radial flow path and strong local vortices. As the fault energy is released, the gas bubbles expand, and the oil flow diffuses outward, forming an obvious flow path through the transformer body, and the surging range expands.

[0049] The above embodiments are only the preferred technical solutions of the present invention and should not be regarded as limitations to the present invention. The protection scope of the present invention should be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, the equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for calculating heavy gas oil flow in transformer internal turn-to-turn short-circuit fault based on gas-liquid-solid coupling, characterized in that: It includes the following steps: Step (1), establishing a 1:1 equivalent power transformer three-dimensional simulation model; Step (2), using field-circuit coupling to solve the energy input conditions of the internal turn-to-turn short-circuit fault of the transformer; Step (3), import the three-dimensional calculation model into ANSYS Fluent software, initialize and load the grid information, and select the appropriate turbulence model and wall function; Step (4): Set up a solid mechanics calculation model in ANSYS Fluent software to implement fluid-solid coupling calculation and calculate the heavy gas oil flow surge results inside the transformer tank under arc fault.

2. The method for calculating heavy gas oil flow in transformer internal turn-to-turn short-circuit fault based on gas-liquid-solid coupling according to claim 1 is characterized in that: In the step (1), SolidWorks is used to establish a 1:1 equivalent power transformer three-dimensional simulation model.

3. The method for calculating heavy gas oil flow in transformer internal turn-to-turn short-circuit fault based on gas-liquid-solid coupling according to claim 1 is characterized in that: The power transformer in step (1) is an oil-immersed power transformer filled with insulating oil.

4. The method for calculating heavy gas oil flow in transformer internal turn-to-turn short-circuit fault based on gas-liquid-solid coupling according to claim 1 is characterized in that: The step (2) specifically includes the following contents: Step (2.1), mathematical models are established for the involved turn-to-turn short-circuit external circuit topology and the internal electromagnetic field of the transformer. According to Maxwell's equations, the matrix form of the internal magnetic field control equation of the converter transformer is: ； In the formula, is the axial magnetic potential component, [ H ]、[ Q ]、[ D ] are coefficient matrices, j is the excitation current flowing into the winding; in the external circuit, the induced voltage of the winding is described as: ； In the formula, k is the eddy current correction factor, R T and L T Respectively represent the total resistance and total inductance in the solution loop, l is the equivalent axial length, N Indicates the number of turns of the winding coil. S c represents the cross-sectional area of ​​the conductor, A e Represents the equivalent magnetic circuit cross-sectional area of ​​the winding, is the integration area; Step (2.2), in the fault loop, the arc current and arc voltage are calculated using the Mayr model, and its differential equation is: ； In the formula, g arc is the arc conductance, u arc and i arc They are the arc voltage and arc current, and the time constant of the Mayr arc , according to the assumptions of the Mayr model, the power dissipation P loss is a constant; The main factors affecting arc energy are arc current, arc voltage and arc duration, and the calculation formula is: ； In the formula, is a time variable.

5. The method for calculating heavy gas oil flow in transformer internal turn-to-turn short-circuit fault based on gas-liquid-solid coupling according to claim 1 is characterized in that: The step (3) specifically includes the following contents: Step (3.1), import the three-dimensional calculation model into ANSYS Fluent software; Step (3.2), initialize and load grid information; Step (3.3), select a suitable turbulence model; Step (3.4), calculate the bubble-liquid boundary velocity under arc fault; Step (3.5), using the dynamic grid to update the instantaneous fluid field; Step (3.6), the flow velocity of the heavy gas oil flow is solved by the momentum equation and turbulence model.

6. The method for calculating heavy gas oil flow in transformer internal turn-to-turn short-circuit fault based on gas-liquid-solid coupling according to claim 5 is characterized in that: The calculation formula for the bubble-liquid boundary velocity under arc fault in step (3.4) is: ； In the formula, R is the bubble radius, is the bubble velocity, is the bubble acceleration, c is the straight-line distance from the fluid boundary to the bubble wall boundary, P c is the pressure at the fluid boundary, ρ is the density, W arc is the arc energy, α is the energy conversion coefficient, μ is the viscosity coefficient of the liquid, γ is the specific heat ratio, t 0 is the initial time, t It's time. p c is the pressure at the fluid boundary, is a historical time variable.

7. The method for calculating heavy gas oil flow in transformer internal turn-to-turn short-circuit fault based on gas-liquid-solid coupling according to claim 5, characterized in that: The calculation formula for updating the instantaneous fluid field using the moving grid in step (3.5) is: ； In the formula, u is the velocity vector, is the physical quantity transported The gradient of , dA is the area element vector, is the control volume boundary, V is the control volume volume, is the diffusion coefficient, express The source term of u g is the mesh speed of the moving mesh.

8. The method for calculating heavy gas oil flow in transformer internal turn-to-turn short-circuit fault based on gas-liquid-solid coupling according to claim 5 is characterized in that: The momentum equation in step (3.6) is calculated as: ； In the formula, μ is the dynamic viscosity, f represents gravity, P It's pressure. P represents the pressure gradient, represents the velocity vector of the fluid, represents the convection term, Represents a sticky item.

9. The method for calculating heavy gas oil flow in transformer internal turn-to-turn short circuit fault based on gas-liquid-solid coupling according to claim 1, characterized in that: In step (4), setting up the solid mechanics calculation model in the ANSYS Fluent software includes the following steps: Step (4.1), using the stress-strain relationship of elastic mechanics to consider the deformation of the transformer solid material under the action of liquid pressure load: ； In the formula, σ xx , σ yy , σ zz yes x , y , z Normal stress in the direction; σ yz , σ xz , σ xy for y - z , x - z , x - y Shear stress in a plane; yes x , y , z Linear strain in the direction; is the engineering shear strain; E is the Young's modulus of the solid material, v is Poisson's ratio; Step (4.2) uses the fluid-structure interaction model to describe the mechanical coupling between the two. The force exerted by the fluid on the solid can be expressed by the surface pressure of the fluid. p Coupled with the displacement field on the solid surface, the displacement and stress fields of the solid are obtained; Step (4.3), update the fluid field boundary conditions according to the solid mechanics calculation results, and update the fluid field state until the convergence conditions are met; Step (4.4), the convergence condition is that the error value of the calculation result of two consecutive iterations is lower than the preset value; Step (4.5), save the result of heavy gas oil flow surge inside the transformer tank under arc fault.

10. The method for calculating heavy gas oil flow in transformer internal turn-to-turn short-circuit fault based on gas-liquid-solid coupling according to claim 9, characterized in that: In step (4.2), the force exerted by the fluid on the solid is expressed by the equation: ； In the formula, f s is the force exerted by the fluid on the solid; n is the surface normal vector, S is a solid surface, p It's pressure.

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