A temperature analysis method for a power transformer winding turn-to-turn short circuit fault

Abstract

The present application belongs to the technical field of power transformer, and particularly relates to a temperature analysis method for winding inter-turn short circuit fault of power transformer, comprising the following steps: S1, establishing a winding inter-turn short circuit fault circuit model of power transformer; S2, constructing a multi-physical field analysis model of power transformer; S3, correcting the model of power transformer; S4, analyzing the temperature distribution characteristics of winding inter-turn short circuit fault of power transformer. Through the established winding inter-turn short circuit fault circuit model of power transformer, the winding inter-turn short circuit fault current and electromagnetic loss of power transformer can be obtained by using numerical solution method, the multi-physical field analysis model of power transformer is constructed based on the technical parameters of power transformer, and the model is corrected by using short circuit temperature rise test, and finally the temperature distribution characteristics of winding inter-turn short circuit fault of power transformer are analyzed, so that the temperature of power transformer during winding inter-turn short circuit fault is simulated and calculated, and the temperature change characteristics of winding inter-turn short circuit fault of power transformer are analyzed.

Description

Technical Field

[0001] This invention belongs to the field of power transformer technology, and specifically relates to a temperature analysis method for inter-turn short-circuit faults in power transformer windings. Background Technology

[0002] Currently, power transformers in practical engineering mostly adopt current differential protection and overcurrent protection measures. However, because the phase voltage and phase current of the main circuit change very little during inter-turn short circuits, they cannot trigger the differential protection and overcurrent protection devices of the power transformer. Under prolonged fault conditions, the temperature at the fault location of the power transformer can easily become too high, leading to insulation damage and even explosion or fire.

[0003] Due to the difficulty in effectively monitoring inter-turn short-circuit faults and the complex internal structure of power transformers, it is challenging to obtain and analyze the internal temperature distribution characteristics of power transformers during faults. A simple and effective method for analyzing the temperature of inter-turn short-circuit faults is lacking. Furthermore, the stringent requirements for the sealing of the transformer casing during actual operation make it difficult to use effective equipment to detect and analyze the temperature distribution characteristics of power transformers.

[0004] While voltage and current variations during inter-turn short circuits can be detected by artificially introducing short-circuit loops in power transformers during experiments, this method suffers from high testing costs, complex procedures, and significant errors. Furthermore, it cannot effectively detect temperature changes in various parts of the power transformer during the experiment. Given the long duration of inter-turn short-circuit faults in power transformers, analyzing their temperature variation characteristics during development is particularly important. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a temperature analysis method for inter-turn short-circuit faults in power transformer windings. This method can obtain the inter-turn short-circuit fault current and electromagnetic losses of the power transformer by solving an established model, and simulate and calculate the temperature during an inter-turn short-circuit fault, thereby enabling the analysis of the temperature variation characteristics of inter-turn short-circuit faults in power transformers.

[0006] To achieve the above objectives, this invention provides a method for temperature analysis of inter-turn short-circuit faults in power transformer windings, comprising the following steps:

[0007] S1. Establish a circuit model for inter-turn short-circuit faults in power transformers;

[0008] S2. Construct a multiphysics analysis model for power transformers;

[0009] S3. Perform power transformer model calibration;

[0010] S4. Analyze the temperature distribution characteristics of inter-turn short-circuit faults in power transformers.

[0011] In S1, by analyzing the equivalent circuit of the power transformer, a circuit model of the inter-turn short-circuit fault of the power transformer is established, including the voltage and current of the high and low voltage windings, the voltage and current of the short-circuit winding, the inductance between the high and low voltage windings, the inductance of the short-circuit winding, and the inductance between the normal winding and the short-circuit winding.

[0012] In S1, the circuit model for inter-turn short-circuit faults in power transformers is represented by the inter-turn short-circuit fault equation for power transformers:

[0013]

[0014] In the formula, I A I B I C These are the phase currents of phases A, B, and C of the high-voltage winding during a fault, respectively; I a I b I c These are the phase currents of phases A, B, and C of the low-voltage winding, respectively; I s This is the short-circuit loop current; R a1 R a2 These are the resistances of the non-short-circuit turns of the low-voltage side winding of phase A; R as For short-circuit turns; L a1 L a2 These are the self-inductances of the non-short-circuit turns on the low-voltage side of phase A; L as For short-circuit turn self-inductance; M Aa1 M Aa2 M a1a2 Mutual inductance between non-short-circuit turns; M Aas M a1s M a2s For the mutual inductance between the short-circuit turn and other windings; R s Z is the contact resistance at the short-circuit point during a single-turn short circuit. a Z b Z c For low-voltage side three-phase load; M Bb L represents the equivalent inductance of phase B of the high-voltage winding. B Equivalent inductance L of low-voltage winding B b Mutual intuition between them; M Cc L represents the equivalent inductance of phase C of the high-voltage winding. C Equivalent inductance L of low-voltage winding C phase c Mutual intuition between them; R B R C These are the equivalent resistances of phases B and C of the high-voltage winding, respectively; u b u c These are the low-voltage winding voltages of phase B and phase C, respectively, u a1 u a2 For the non-short-circuit winding voltage, uza This is the load voltage.

[0015] In the process of constructing the multiphysics analysis model of the power transformer in S2, the high and low voltage windings, core, end insulation, structural components, transformer oil and transformer shell (including transformer tank shell and radiator shell) of the power transformer are considered, while the support bars and pads are ignored.

[0016] In S2, the steps for constructing a multiphysics analysis model of a power transformer are as follows:

[0017] S21, Introducing vector magnetic potential A and scalar potential Establish a mathematical model of the electromagnetic field of a power transformer:

[0018]

[0019]

[0020] In the formula, μ is the magnetic permeability; σ is the electrical conductivity; t is time; J s Source current density;

[0021] S22. Considering the influence of the skin effect, the skin depth is calculated using equation (4), and stray losses of the transformer casing and structural components are calculated using equation (5):

[0022]

[0023]

[0024] In the formula, P e δ represents the eddy current loss of the metallic conductor; δ is the skin depth; ω is the angular frequency; σ is the conductivity of the conductor; σ i J is the conductivity of unit i; ei J is the eddy current density vector of element i; ei * V is the conjugate eddy current density vector of element i; i is the volume of element i; n is the number of elements in the overall steel plate subdivision.

[0025] S23. The heat transfer process inside the transformer satisfies the conservation of mass, momentum, and energy, as shown in the following equation:

[0026]

[0027] In the formula, v is the fluid velocity vector; ρ is the fluid density, in kg / m³. 3 p is the fluid pressure, in Pa; f is the external force acting on a unit volume of fluid, in N / m³. 3η is the dynamic viscosity of the fluid, in kg / (m·s); T is the fluid temperature, in K; c p ρ is the specific heat capacity of the fluid, in J / (kg·K); k is the thermal conductivity of the fluid, in W / (m·K); Φ is the internal heat source of the fluid; S h This refers to the portion of fluid mechanical energy converted into heat energy under the action of fluid viscous forces.

[0028] S24. Using electromagnetic loss as a heat source, since transformer oil is viscous, the relative velocity between the solid wall and the nearby transformer oil is set to 0, and the wall temperature is set to be consistent with the temperature of the nearby fluid.

[0029] S25. Taking full account of the heat conduction and heat convection of each part inside the power transformer, the transformer tank shell and radiator shell are simplified to smooth planes. That is, the heat dissipation process of the transformer shell is considered to be longitudinal convection heat transfer across the flat plate. The heat transfer process between the power transformer and the outside world is equivalently expressed by the convection heat transfer coefficient. Therefore, under the condition of convection heat transfer, the heat transfer coefficient is solved by equation (7):

[0030]

[0031] In the formula h c The convective heat transfer coefficient is expressed in W / (m³). 2 ·K); L is the characteristic dimension, in meters; Nu is the Nusselt number;

[0032] S26. Nusselt number of a vertical wall under natural convection heat transfer conditions. v Nusselt number of horizontal wall h Represented as:

[0033] Nu h =0.27Ra 1 / 4 (8);

[0034]

[0035] Ra = Gr·Pr (10);

[0036]

[0037]

[0038] In the formula, Pr is Prandtl number; Gr is Grashof number; Ra is Rayleigh number; and g is gravitational acceleration in m / s². 2 β is the coefficient of thermal expansion of the corresponding fluid; θ is the temperature difference between the wall and the external fluid, in Kelvin; μ l The viscosity coefficient;

[0039] S27. Under forced convection heat transfer conditions, the Nusselt number Nu1 for a horizontal wall and the Nusselt number Nu2 for a vertical wall can be expressed as:

[0040] Nu1 = 0.037Re 0.8 Pr 1 / 3 (13);

[0041] Nu2 = 0.228Re 0.731 Pr 1 / 3 (14);

[0042] In the formula, Re is the Reynolds number;

[0043] S28. Ignoring radiation from various parts inside the transformer, assuming the transformer only radiates energy to the surrounding environment through its outer casing, the heat transfer process is equivalently expressed using the radiation heat transfer coefficient, i.e.:

[0044]

[0045] In the formula, ε is the emissivity of the transformer casing surface; σ b T is the Stefan-Boltzmann constant; w T represents the transformer casing temperature. a The ambient temperature;

[0046] S29. The heat dissipation intensity h of the transformer casing can be expressed as the convective heat transfer coefficient h. c With the radiation heat transfer coefficient h r The sum is:

[0047] h = h c +h r (16).

[0048] In the aforementioned S2, within the multiphysics analysis model of the power transformer, due to the slow flow velocity of the transformer oil, calculations using the Rayleigh number Ra show that it is significantly less than 1 × 10⁻⁶. 9 Therefore, the transformer is considered to be a laminar flow model.

[0049] In S2, the influence of gravity is considered in the multiphysics analysis model of the power transformer, and the gravitational acceleration g is set to 9.8 m / s². 2 The direction is along the negative Z-axis.

[0050] In S3, the temperature rise test of the power transformer is carried out using the short-circuit method to correct the multi-physics model of the power transformer under rated operating conditions.

[0051] In S4, the temperature distribution characteristics of inter-turn short-circuit faults in power transformers include the temperatures of high and low voltage windings, the temperature at the location of the inter-turn short circuit, the temperature of the power transformer oil, and the temperature distribution of the power transformer casing.

[0052] The analysis process for the temperature distribution characteristics of inter-turn short-circuit faults in power transformers in S4 is as follows:

[0053] By numerically solving the equations for inter-turn short-circuit faults and the mathematical model of the electromagnetic field of a power transformer under rated operating conditions, the electromagnetic losses of the faulty winding and the normal winding are obtained. The electromagnetic losses are coupled into the fluid temperature field as an initial heat source using heterogeneous mesh mapping. The losses of each part are coupled to the corresponding parts of the transformer using weighted interpolation heterogeneous mesh mapping. Taking into account the heat dissipation intensity h of the transformer shell and the internal heat transfer characteristics, the mass, momentum and energy conservation equations of the power transformer are numerically solved to obtain the temperature distribution characteristics of inter-turn short-circuit faults in the power transformer.

[0054] The algorithm involved in this invention can be executed by an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor. The processor executes the software to implement the algorithm described above.

[0055] The beneficial effects of this invention are:

[0056] This invention establishes a circuit model of inter-turn short-circuit faults in power transformers. It can obtain the inter-turn short-circuit fault current and electromagnetic loss of power transformers using numerical solutions. Based on the technical parameters of power transformers, a multi-physics analysis model of power transformers is constructed, and the model is corrected using short-circuit temperature rise tests. Finally, the temperature distribution characteristics of inter-turn short-circuit faults in power transformers are analyzed, realizing the simulation calculation of the temperature during inter-turn short-circuit faults in power transformers, thereby achieving the analysis of the temperature change characteristics of inter-turn short-circuit faults in power transformers. Attached Figure Description

[0057] Figure 1 This is a flowchart illustrating the principle of this invention;

[0058] Figure 2 This is a schematic diagram of the geometric structure of the high and low voltage windings of the power transformer in an embodiment of the present invention;

[0059] Figure 3 This is an equivalent circuit diagram of an inter-turn short-circuit fault in a power transformer according to an embodiment of the present invention;

[0060] Figure 4 This is the wiring diagram for the short-circuit temperature rise test in an embodiment of the present invention. Detailed Implementation

[0061] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0062] like Figure 1 As shown, a method for temperature analysis of inter-turn short-circuit faults in power transformer windings includes the following steps:

[0063] S1. Establish a circuit model for inter-turn short-circuit faults in power transformers;

[0064] S2. Construct a multiphysics analysis model for power transformers;

[0065] S3. Perform power transformer model calibration;

[0066] S4. Analyze the temperature distribution characteristics of inter-turn short-circuit faults in power transformers.

[0067] In S1, by analyzing the equivalent circuit of the power transformer, a circuit model of the inter-turn short-circuit fault of the power transformer is established, including the voltage and current of the high and low voltage windings, the voltage and current of the short-circuit winding, the inductance between the high and low voltage windings, the inductance of the short-circuit winding, and the inductance between the normal winding and the short-circuit winding.

[0068] In S1, the equivalent circuit diagram of the inter-turn short-circuit fault circuit model of the power transformer is as follows: Figure 3 As shown, the equation for an inter-turn short-circuit fault in a power transformer can be expressed as follows:

[0069]

[0070] In the formula, I A I B I C These are the phase currents of phases A, B, and C of the high-voltage winding during a fault, respectively; I a I b I c These are the phase currents of phases A, B, and C of the low-voltage winding, respectively; I s This is the short-circuit loop current; R a1 R a2 These are the resistances of the non-short-circuit turns of the low-voltage side winding of phase A; R as For short-circuit turns; L a1 L a2 These are the self-inductances of the non-short-circuit turns on the low-voltage side of phase A; L as For short-circuit turn self-inductance; M Aa1 M Aa2 M a1a2 Mutual inductance between non-short-circuit turns; M Aas M a1s M a2s For the mutual inductance between the short-circuit turn and other windings; R s Z is the contact resistance at the short-circuit point during a single-turn short circuit. a Z b Z c For low-voltage side three-phase load; M Bb L represents the equivalent inductance of phase B of the high-voltage winding. B Equivalent inductance L of low-voltage winding B bMutual intuition between them; M Cc L represents the equivalent inductance of phase C of the high-voltage winding. C Equivalent inductance L of low-voltage winding C phase c Mutual intuition between them; R A R B R C These are the equivalent resistances of phases A, B, and C of the high-voltage winding, respectively; u a u b u c These represent the low-voltage winding voltages of phases A, B, and C, respectively. a1 u a2 For the non-short-circuit winding voltage, u za This is the load voltage. L A L B L C It is the self-inductance of the three-phase high-voltage winding.

[0071] In S2, during the construction of the multiphysics analysis model of the power transformer, the high and low voltage windings, core, end insulation, structural components, transformer oil, and transformer casing (including the transformer tank casing and radiator casing) are considered, while support bars and pads are ignored. The simplified geometry is as follows: Figure 2 As shown.

[0072] In S2, the steps for constructing a multiphysics analysis model of a power transformer are as follows:

[0073] S21, Introducing vector magnetic potential A and scalar potential Establish a mathematical model of the electromagnetic field of a power transformer:

[0074]

[0075]

[0076] In the formula, μ is the magnetic permeability; σ is the electrical conductivity; t is time; J s Source current density;

[0077] It is a partial differential symbol. These are Hamiltonian operators, all of which are well-known symbols with clearly defined meanings.

[0078] S22. Considering the influence of the skin effect, the skin depth is calculated using equation (4), and stray losses of the transformer casing and structural components are calculated using equation (5):

[0079]

[0080]

[0081] In the formula, P eδ represents the eddy current loss of the metallic conductor; δ is the skin depth; ω is the angular frequency; σ is the conductivity of the conductor; σ i J is the conductivity of unit i; ei J is the eddy current density vector of element i; ei * V is the conjugate eddy current density vector of element i; i is the volume of element i; n is the number of elements in the overall steel plate subdivision.

[0082] In the multiphysics analysis model of power transformers, electromagnetic losses are treated as heat sources. A weighted interpolation method is used to map heterogeneous meshes, applying the loss values ​​from the electromagnetic field calculations to the corresponding mesh nodes in the power transformer's fluid temperature field.

[0083] S23. The heat transfer process inside the transformer satisfies the conservation of mass, momentum, and energy, as shown in the following equation:

[0084]

[0085] In the formula, v is the fluid velocity vector; ρ is the fluid density, in kg / m³. 3 p is the fluid pressure, in Pa; f is the external force acting on a unit volume of fluid, in N / m³. 3 η is the dynamic viscosity of the fluid, in kg / (m·s); T is the fluid temperature, in K; c p ρ is the specific heat capacity of the fluid, in J / (kg·K); k is the thermal conductivity of the fluid, in W / (m·K); Φ is the internal heat source of the fluid; S h This refers to the portion of fluid mechanical energy converted into heat energy under the action of fluid viscous forces.

[0086] S24. Using electromagnetic loss as a heat source, since transformer oil is viscous, the relative velocity between the solid wall and the nearby transformer oil is set to 0, and the wall temperature is set to be consistent with the temperature of the nearby fluid.

[0087] S25. Taking full account of the heat conduction and heat convection of each part inside the power transformer, the transformer tank shell and radiator shell are simplified to smooth planes. That is, the heat dissipation process of the transformer shell is considered to be longitudinal convection heat transfer across the flat plate. The heat transfer process between the power transformer and the outside world is equivalently expressed by the convection heat transfer coefficient. Therefore, under the condition of convection heat transfer, the heat transfer coefficient is solved by equation (7):

[0088]

[0089] In the formula h c The convective heat transfer coefficient is expressed in W / (m³). 2 ·K); L is the characteristic dimension, in meters; Nu is the Nusselt number;

[0090] S26. Nusselt number of a vertical wall under natural convection heat transfer conditions. v Nusselt number of horizontal wall h Represented as:

[0091] Nu h =0.27Ra 1 / 4 (8);

[0092]

[0093] Ra = Gr·Pr (10);

[0094]

[0095]

[0096] In the formula, Pr is Prandtl number; Gr is Grashof number; Ra is Rayleigh number; and g is gravitational acceleration in m / s². 2 β is the coefficient of thermal expansion of the corresponding fluid; θ is the temperature difference between the wall and the external fluid, in Kelvin; μ l The viscosity coefficient;

[0097] S27. Under forced convection heat transfer conditions, the Nusselt number Nu1 for a horizontal wall and the Nusselt number Nu2 for a vertical wall can be expressed as:

[0098] Nu1 = 0.037Re 0.8 Pr 1 / 3 (13);

[0099] Nu2 = 0.228Re 0.731 Pr 1 / 3 (14);

[0100] In the formula, Re is the Reynolds number;

[0101] S28. Ignoring radiation from various parts inside the transformer, assuming the transformer only radiates energy to the surrounding environment through its outer casing, the heat transfer process is equivalently expressed using the radiation heat transfer coefficient, i.e.:

[0102]

[0103] In the formula, ε is the emissivity of the transformer casing surface; σ b T is the Stefan-Boltzmann constant; w T represents the transformer casing temperature. a The ambient temperature;

[0104] S29. The heat dissipation intensity h of the transformer casing can be expressed as the convective heat transfer coefficient h. c With the radiation heat transfer coefficient h r The sum is:

[0105] h = h c +h r (16).

[0106] In S2, in the multiphysics analysis model of the power transformer, due to the slow flow velocity of the transformer oil, the Rayleigh number Ra is calculated to be much smaller than 1×10⁻⁶. 9 Therefore, the transformer is considered to be a laminar flow model.

[0107] In S2, in the multiphysics analysis model of the power transformer, the influence of gravity is considered, and the gravitational acceleration g is set to 9.8 m / s². 2 The direction is along the negative Z-axis.

[0108] In S3, the temperature rise test of the power transformer is carried out using the short-circuit method to correct the multi-physics model of the power transformer under rated operating conditions.

[0109] In this embodiment, the wiring diagram for the power transformer short-circuit temperature rise test is as follows: Figure 4 As shown, by recording test data such as the temperature rise of the high and low voltage windings and the temperature rise of the top oil, the multiphysics model of the power transformer under rated operating conditions is corrected to ensure that its calculation error is within a reasonable range.

[0110] In S4, the temperature distribution characteristics of inter-turn short-circuit faults in power transformers include the temperatures of high and low voltage windings, the temperature at the location of the inter-turn short circuit, the temperature of the power transformer oil, and the temperature distribution of the power transformer casing.

[0111] In S4, the analysis process of the temperature distribution characteristics of inter-turn short-circuit faults in power transformers is as follows:

[0112] By numerically solving the equations for inter-turn short-circuit faults and the mathematical model of the electromagnetic field of a power transformer under rated operating conditions, the electromagnetic losses of the faulty winding and the normal winding are obtained. The electromagnetic losses are coupled into the fluid temperature field as an initial heat source using heterogeneous mesh mapping. The losses of each part are coupled to the corresponding parts of the transformer using weighted interpolation heterogeneous mesh mapping. Taking into account the heat dissipation intensity h of the transformer shell and the internal heat transfer characteristics, the mass, momentum and energy conservation equations of the power transformer are numerically solved to obtain the temperature distribution characteristics of inter-turn short-circuit faults in the power transformer.

[0113] Electromagnetic losses consist of high and low voltage winding resistance losses, high and low voltage winding eddy current losses, core losses, and stray losses from the transformer casing and structural components. These losses can be calculated by combining the power transformer inter-turn short-circuit fault equation, the power transformer electromagnetic field mathematical model, the power transformer multi-physics field analysis model, and known technologies.

Claims

1. A method for temperature analysis of inter-turn short-circuit faults in power transformer windings, characterized in that... Includes the following steps: S1. Establish a circuit model for inter-turn short-circuit faults in power transformers; S2. Construct a multiphysics analysis model for power transformers; S3. Perform power transformer model calibration; S4. Analyze the temperature distribution characteristics of inter-turn short-circuit faults in power transformers; In S1, by analyzing the equivalent circuit of the power transformer, a circuit model of the inter-turn short-circuit fault of the power transformer is established, including the voltage and current of the high and low voltage windings, the voltage and current of the short-circuit winding, the inductance between the high and low voltage windings, the inductance of the short-circuit winding, and the inductance between the normal winding and the short-circuit winding. The circuit model of inter-turn short-circuit fault in a power transformer is represented by the inter-turn short-circuit fault equation of the power transformer: （1）； In the formula, I A I B I C These are the phase currents of phases A, B, and C of the high-voltage winding during a fault, respectively; I a I b I c These are the phase currents of phases A, B, and C of the low-voltage winding, respectively; I s This is the short-circuit loop current; R a1 R a2 These are the resistances of the non-short-circuit turns of the low-voltage side winding of phase A; R as For short-circuit turns; L a1 L a2 These are the self-inductances of the non-short-circuit turns on the low-voltage side of phase A; L as For short-circuit turn self-inductance; M Aa1 M Aa2 M a1a2 Mutual inductance between non-short-circuit turns; M Aas M a1s M a2s For the mutual inductance between the short-circuit turn and other windings; R s Z is the contact resistance at the short-circuit point during a single-turn short circuit. a Z b Z c For low-voltage side three-phase load; M Bb L represents the equivalent inductance of phase B of the high-voltage winding. B Equivalent inductance L of low-voltage winding B b Mutual intuition between them; M Cc L represents the equivalent inductance of phase C of the high-voltage winding. C Equivalent inductance L of low-voltage winding C phase c Mutual intuition between them; R B R C These are the equivalent resistances of phases B and C of the high-voltage winding, respectively; u b u c These are the low-voltage winding voltages of phase B and phase C, respectively, u a1 u a2 For the non-short-circuit winding voltage, u za This is the load voltage; In S2, during the construction of the multiphysics analysis model of the power transformer, the high and low voltage windings, core, end insulation, structural components, transformer oil and transformer shell of the power transformer are considered, while the support bars and pads are ignored. The steps for constructing a multiphysics analysis model of a power transformer are as follows: S21, Introducing vector magnetic potential A and scalar potential Establish a mathematical model of the electromagnetic field of a power transformer: （2）； （3）； In the formula, Permeability; t is the conductivity; t is time; J s Source current density; S22. Considering the influence of the skin effect, the skin depth is calculated using equation (4), and stray losses of the transformer casing and structural components are calculated using equation (5): （4）； （5）； In the formula, P e Eddy current loss in metallic conductors; For skin depth; Angular frequency; It is the electrical conductivity of the conductor; J is the conductivity of unit i; ei It is the eddy current density vector of element i; V is the conjugate eddy current density vector of element i; i is the volume of element i; n is the number of elements in the overall steel plate subdivision. S23. The heat transfer process inside the transformer satisfies the conservation of mass, momentum, and energy, as shown in the following equation: （6）； In the formula, For fluid velocity vector; Fluid density, unit: kg / m³ 3 p is the fluid pressure, in Pa; f is the external force acting on a unit volume of fluid, in N / m³. 3 ; The fluid's dynamic viscosity is expressed in kg / (m·s); T is the fluid temperature in Kelvin; c p ρ is the specific heat capacity of the fluid, in J / (kg·K); k is the thermal conductivity of the fluid, in W / (m·K); For internal heat source of fluid; S h This refers to the portion of fluid mechanical energy converted into heat energy under the action of fluid viscous forces. S24. Using electromagnetic loss as a heat source, since transformer oil is viscous, the relative velocity between the solid wall and the nearby transformer oil is set to 0, and the wall temperature is set to be consistent with the temperature of the nearby fluid. S25. Taking full account of the heat conduction and heat convection of each part inside the power transformer, the transformer tank shell and radiator shell are simplified to smooth planes. That is, the heat dissipation process of the transformer shell is considered to be longitudinal convection heat transfer across the flat plate. The heat transfer process between the power transformer and the outside world is equivalently expressed by the convection heat transfer coefficient. Therefore, under the condition of convection heat transfer, the heat transfer coefficient is solved by equation (7): （7）； In the formula h c The convective heat transfer coefficient is expressed in W / (m³). 2 ·K); L is the characteristic dimension, in meters; Nu is the Nusselt number; S26. Nusselt number of a vertical wall under natural convection heat transfer conditions. v Nusselt number of horizontal wall h Represented as: （8）； （9）； （10）； （11）； （12）； In the formula, Pr is Prandtl number; Gr is Grashof number; Ra is Rayleigh number; and g is gravitational acceleration in m / s². 2 ; It is the coefficient of thermal expansion of the corresponding fluid; It is the temperature difference between the wall surface and the external fluid, measured in K. The viscosity coefficient; S27. Under forced convection heat transfer conditions, the Nusselt number Nu1 for a horizontal wall and the Nusselt number Nu2 for a vertical wall can be expressed as: （13）； （14）； In the formula, Re is the Reynolds number; S28. Ignoring radiation from various parts inside the transformer, assuming the transformer only radiates energy to the surrounding environment through its outer casing, the heat transfer process is equivalently expressed using the radiation heat transfer coefficient, i.e.: （15）； In the formula Emissivity of the transformer casing surface; T is the Stefan-Boltzmann constant; w T represents the transformer casing temperature. a Ambient temperature; S29. The heat dissipation intensity h of the transformer casing can be expressed as the convective heat transfer coefficient h. c With the radiation heat transfer coefficient h r The sum is: （16）； In S3, the temperature rise test of the power transformer is carried out using the short-circuit method, and the multi-physics field model of the power transformer under rated operating conditions is corrected. In S4, the temperature distribution characteristics of inter-turn short-circuit faults in power transformers include the temperature distribution of high and low voltage windings, the temperature at the location of the inter-turn short circuit, the temperature of the power transformer oil, and the temperature distribution of the power transformer casing. The analysis process for the temperature distribution characteristics of inter-turn short-circuit faults in power transformers is as follows: By numerically solving the equations for inter-turn short-circuit faults and the mathematical model of the electromagnetic field of a power transformer under rated operating conditions, the electromagnetic losses of the faulty winding and the normal winding are obtained. The electromagnetic losses are coupled into the fluid temperature field as an initial heat source using heterogeneous mesh mapping. The losses of each part are coupled to the corresponding parts of the transformer using weighted interpolation heterogeneous mesh mapping. Taking into account the heat dissipation intensity h of the transformer shell and the internal heat transfer characteristics, the mass, momentum and energy conservation equations of the power transformer are numerically solved to obtain the temperature distribution characteristics of inter-turn short-circuit faults in the power transformer.

2. The temperature analysis method for inter-turn short-circuit faults in power transformer windings according to claim 1, characterized in that: In the aforementioned S2, within the multiphysics analysis model of the power transformer, due to the slow flow velocity of the transformer oil, calculations using the Rayleigh number Ra show that it is significantly less than 1 × 10⁻⁶. 9 Therefore, the transformer is considered to be a laminar flow model.

3. The temperature analysis method for inter-turn short-circuit faults in power transformer windings according to claim 1, characterized in that: In S2, the influence of gravity is considered in the multiphysics analysis model of the power transformer, and the gravitational acceleration g is set to 9.8 m / s². 2 The direction is along the negative Z-axis.

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