A method for determining temperature rise of a gas insulated power transmission equipment

Abstract

The application provides a method for determining temperature rise of gas insulated power transmission equipment, which comprises the following steps: obtaining a two-dimensional multi-section model corresponding to the gas insulated power transmission equipment composed of multiple standard sections based on structural parameters of the gas insulated power transmission equipment; establishing a two-dimensional multi-section field-circuit coupling model based on the two-dimensional multi-section model through Kirchhoff voltage and current equations and electromagnetic field control equations; the eddy current field distribution and ohmic loss of the gas insulated power transmission equipment can be quickly determined through the two-dimensional multi-section field-circuit coupling model; the ohmic loss is used as a heat source excitation of a heat flow coupling field control equation, and the temperature rise along the radial direction inside the gas insulated power transmission equipment is obtained by solving through a finite volume method; the thermal stability of the gas insulated power transmission equipment is evaluated in combination with the temperature rise along the axial direction inside the gas insulated power transmission equipment under different working conditions; and the accuracy and efficiency of transient temperature rise analysis of the gas insulated power transmission equipment can be effectively improved according to the above technical scheme.

Description

Technical Field

[0001] This application relates to the field of power transmission equipment optimization technology, and in particular to a method for determining the temperature rise of gas-insulated power transmission equipment. Background Technology

[0002] Gas-Insulated Metal-Enclosed Transmission Line (GIL) is a key power transmission device that transmits high-voltage electrical energy within a sealed metal casing filled with insulating gas. GILs offer advantages such as large transmission capacity, low electromagnetic interference, high operational reliability, and strong environmental adaptability, and are widely used in urban power grids, hydropower stations, nuclear power plants, and power transmission in special environmental conditions such as tunnels and mountainous terrain.

[0003] However, under extreme conditions such as short-circuit faults or overload operation, the conductors and housing inside the GIL may experience significant temperature rise. Due to its enclosed structure and limited heat dissipation, excessively high localized temperature rise can lead to insulation aging, structural deformation, and even equipment failure. Therefore, how to quickly and accurately predict the temperature rise distribution of the GIL during the design and operation / maintenance phases, and accordingly assess its thermal stability, is a key technical issue for improving the efficiency of GIL optimization design and operational safety. Summary of the Invention

[0004] This application provides a method for determining the temperature rise of gas-insulated power transmission equipment, which solves the problems of low accuracy and low efficiency in determining the temperature rise of equipment in the prior art. It achieves high-precision prediction of the transient temperature rise of equipment under transient operating conditions, and further realizes accurate assessment of the thermal stability of equipment under transient operating conditions.

[0005] To achieve the above objectives, the technical solution of this application embodiment is as follows:

[0006] This application provides a method for determining the temperature rise of gas-insulated power transmission equipment, the method comprising:

[0007] Based on the structural parameters and material properties of the gas-insulated power transmission equipment, the geometric information of the equipment is extracted, and a two-dimensional multi-section model of multiple standard sections is constructed. The two-dimensional multi-section model is used to characterize the three-dimensional electromagnetic field distribution characteristics of each standard section of the gas-insulated power transmission equipment.

[0008] Based on the aforementioned two-dimensional multi-section model, and combining Kirchhoff's voltage and current equations with electromagnetic field control equations, a two-dimensional multi-section field-circuit coupling model is established to achieve the joint solution of circuit degrees of freedom and electromagnetic field degrees of freedom.

[0009] The eddy current field distribution and ohmic loss of the gas-insulated power transmission equipment are determined by the two-dimensional multi-section field-circuit coupling model, providing heat source data for subsequent temperature rise analysis.

[0010] The ohmic loss is used as a heat source term in the control equation of the heat-fluid coupling field. The radial temperature rise inside the gas-insulated power transmission equipment is obtained by solving the finite volume method.

[0011] Based on the radial temperature rise of the conductor under different operating conditions, and combined with the axial temperature field distribution inside the equipment, the overall thermal stability of the gas-insulated power transmission equipment is evaluated.

[0012] In one possible implementation, the phase conductors in the two-dimensional multi-section model are connected in series to the system power supply; the housings are connected in parallel through phase-to-phase shorting blocks and grounding wires to form a coupling relationship between the internal and external circuits; an air domain is established outside the housing, and Dirichlet boundary conditions are applied to the boundary of the air domain to reflect the real boundary conditions of the electromagnetic field around the equipment; for a three-phase housing structure, each housing is interconnected through phase-to-phase shorting blocks and grounding wires to reflect the real electrical connection characteristics.

[0013] The multiple standard sections are used to segment the gas-insulated power transmission equipment through external phase-to-phase shorting blocks. Each standard section is sealed at both ends with an insulator and filled with insulating gas. Each cross section in the two-dimensional multi-section model corresponds to a typical standard section of the gas-insulated power transmission equipment.

[0014] In one possible implementation, the two-dimensional multi-section field-circuit coupling model treats the magnetic vector potential, loop current, and node voltage corresponding to the multiple standard segments as unknown variables, and introduces port voltage degrees of freedom at each conductor port. A discretized equation is constructed by combining the electromagnetic field control equation and the circuit balance equation; wherein the circuit balance equation is derived based on Kirchhoff's voltage law and Kirchhoff's current law; the discretized equation is expressed as:

[0015] ;

[0016] in, and Represents the stiffness matrix; A It is the magnetic vector potential matrix; I It is a loop current matrix; The load matrix represents the conduction current. This is the resistor matrix for the external circuit; For similar The matrix is ​​determined based on the conductor's geometry and material properties; For the inductance matrix of the external circuit; This is the external circuit port voltage matrix.

[0017] In one possible implementation, the electromagnetic field control equations are used to divide the two-dimensional multi-section model into multiple nodal elements using the finite element method, and combined with... The coupling equations of magnetic vector potential and electric scalar potential are established to solve the eddy current field distribution of each node element, thereby obtaining the magnetic field distribution in the two-dimensional multi-section model.

[0018] In one possible implementation, the electromagnetic field control equation is expressed in the frequency domain as:

[0019] ; ;

[0020] The electromagnetic field control equations are expressed in the time domain as follows:

[0021] ; ;

[0022] in, It is magnetic vector potential. It is the permeability. It is electrical conductivity. It is angular frequency. It is an electric scalar potential, and It is the source current density of the conductive rod. It is time. j It is the imaginary unit. I It is the loop current. S Let be the cross-sectional area of ​​the conductor.

[0023] In one possible implementation, the two-dimensional multi-section field-circuit coupling model further includes a potential balance equation established for each phase conductor; the potential balance equation is used to ensure the uniqueness of the equation set of the two-dimensional multi-section field-circuit coupling model; the potential balance equation is:

[0024] ;

[0025] in, , , They are respectively A , B , C External voltage source excitation in a three-phase circuit. , , and , , They represent A , B , C External resistance and inductance in a three-phase circuit; , , For load resistance, This is the effective value of the voltage source; I a , I b , I c They represent A , B , C Conduction current in a three-phase circuit; , , They represent A , B , C Phase conductor potential in gas-insulated power transmission equipment in a three-phase circuit; Angular frequency, t For time; This indicates a delayed phase.

[0026] In one possible implementation, the two-dimensional multi-section field-circuit coupling model includes a first circuit and a second circuit; wherein, the first circuit consists of a voltage source, transmission line impedance and load impedance, and is used to describe the power transmission process of the main circuit, realizing the coupling of magnetic field degree of freedom and circuit degree of freedom at the conductor port; the second circuit consists of a phase-to-phase shorting bar and a grounding wire, and is used to simulate the electromagnetic coupling effect of phase-to-phase and grounding loops, and its current distribution in the shell and connection structure forms induced current or eddy current.

[0027] In one possible implementation, the thermal flow field coupling control equations are based on the mass conservation equation, momentum conservation equation, and energy conservation equation, according to... direction, direction and The direction is expanded into partial differential form; the coupled control equations of the heat flow field are as follows:

[0028] ;

[0029] in, , , respectively fluid along , , The velocity component in the direction; It is the pressure of the fluid; It is the dynamic viscosity of the fluid; , , respectively fluid along , , The volume force vector in the direction; It is the coefficient of thermal expansion of the fluid; Indicates the temperature of the fluid; It is the reference temperature of the fluid; , , They represent the gravitational force along the direction of gravity. , , Component of direction; It is specific heat capacity. It is the thermal conductivity of the fluid. t It is time; It is the heat source term per unit mass of fluid.

[0030] In one possible implementation, the step of treating the ohmic loss as a heat source term in the heat-fluid coupling field control equation and solving it using the finite volume method to obtain the radial temperature rise inside the gas-insulated power transmission equipment includes:

[0031] The control equations of the thermal-fluid coupling field are discretized using the finite volume method and solved in combination with the thermal balance equations of the radial section to obtain the radial temperature distribution characteristics inside the conductor of the gas-insulated power transmission equipment.

[0032] Based on the temperature distribution characteristics, the radial temperature rise of the conductor is determined.

[0033] In one possible implementation, the evaluation of the overall thermal stability of the gas-insulated power transmission equipment, based on the radial temperature rise of the conductor under different operating conditions and combined with the axial temperature field distribution inside the equipment, includes:

[0034] Under different operating conditions, the conductor loss and shell loss of the gas-insulated power transmission equipment are determined based on the two-dimensional multi-section field-circuit coupling model.

[0035] Based on the conductor loss and the shell loss, calculate the temperature field distribution along the axial direction inside the conductor;

[0036] Based on the temperature field distribution along the radial and axial directions, the temperature rise along the radial direction and the temperature rise along the axial direction are obtained respectively.

[0037] The thermal stability of the gas-insulated power transmission equipment is comprehensively evaluated based on the radial and axial temperature rises.

[0038] The technical solution provided in this application embodiment has at least the following technical effects or advantages:

[0039] This application employs a two-dimensional multi-section field-circuit coupling method to quickly, accurately, and comprehensively analyze the electromagnetic field distribution characteristics of gas-insulated power transmission equipment. Furthermore, by introducing ohmic losses into the heat-fluid coupling field as a heat source for temperature rise calculation, the accuracy and reliability of temperature rise prediction are greatly improved, thereby achieving an accurate assessment of the equipment's thermal stability. Moreover, the technical solution of this application is particularly suitable for transient temperature rise analysis of gas-insulated power transmission equipment under transient conditions such as short circuits, lightning impulse voltages, and switching overvoltages, effectively compensating for the shortcomings of traditional finite element methods in handling the transient electromagnetic fields and temperature rise coupling calculations of long-distance equipment. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 A flowchart illustrating a method for determining the temperature rise of gas-insulated power transmission equipment, provided as an embodiment of this application;

[0042] Figure 2 A schematic diagram of a two-dimensional multi-section electromagnetic field-circuit coupling model provided for an embodiment of this application;

[0043] Figure 3 A schematic diagram of the heat transfer process in the radial section of a gas-insulated power transmission equipment provided in this application embodiment;

[0044] Figure 4 This application provides a flowchart for determining the eddy current field distribution and temperature rise of gas-insulated power transmission equipment based on a two-dimensional multi-section field-circuit coupling model. Detailed Implementation

[0045] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0046] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0047] In related technologies, there are two methods for analyzing the electromagnetic field distribution and loss distribution of gas-insulated power transmission equipment: the equivalent circuit method and the finite element method (FEM). The equivalent circuit method has high computational efficiency but cannot account for the skin effect, which affects the accuracy of loss calculations, nor can it accurately determine the electromagnetic field distribution. The finite element method has high computational accuracy, but when applied to transient analysis, it requires consideration of long-distance three-dimensional structures. Directly applying the finite element method to power transmission systems hundreds of kilometers long introduces a large number of mesh elements, causing the computational load to exceed the processing capacity of conventional computing resources.

[0048] The current method used to calculate the transient temperature rise of long-distance gas-insulated power transmission equipment is generally the finite difference method. However, this method cannot take into account the actual external structure of the gas-insulated power transmission equipment. Furthermore, when calculating the ohmic losses required for the temperature rise, traditional magnetic field models use a given current excitation. In reality, the current under transient conditions depends on the system voltage source excitation and the system circuit structure; therefore, this method cannot accurately reflect the actual situation.

[0049] To address the aforementioned issues, this application provides a method for determining the temperature rise of gas-insulated power transmission equipment. This method can be applied to scenarios where gas-insulated power transmission equipment is under transient operating conditions such as short circuits, lightning impulse voltages, and switching overvoltages. Using the method provided in this application, transient temperature rises under these scenarios can be analyzed, effectively compensating for the shortcomings of traditional finite element methods in handling the transient electromagnetic fields and temperature rise coupling calculations of long-distance equipment. The above method includes: extracting the geometric information of the gas-insulated power transmission equipment based on its structural parameters and material properties, and constructing a two-dimensional multi-section model of multiple standard sections; this two-dimensional multi-section model is used to characterize the three-dimensional electromagnetic field distribution characteristics of each standard section of the gas-insulated power transmission equipment; based on this two-dimensional multi-section model, a two-dimensional multi-section field-circuit coupling model is established through Kirchhoff's voltage and current equations and electromagnetic field control equations to achieve joint solution of circuit degrees of freedom and electromagnetic field degrees of freedom; through this two-dimensional multi-section field-circuit coupling model, the eddy current field distribution and ohmic loss of the gas-insulated power transmission equipment are determined, providing heat source data for subsequent temperature rise analysis; the ohmic loss is used as a heat source term in the heat-fluid coupling field control equation, and solved using the finite volume method to obtain the radial temperature rise inside the gas-insulated power transmission equipment; based on the radial temperature rise of the conductor under different operating conditions, combined with the axial temperature field distribution inside the equipment, the overall thermal stability of the gas-insulated power transmission equipment is evaluated. By employing the above technical solution and a two-dimensional multi-section field-circuit coupling method, the electromagnetic field distribution characteristics of gas-insulated power transmission equipment can be analyzed quickly, accurately, and comprehensively. Furthermore, by introducing ohmic losses into the heat flow coupling field as a heat source for temperature rise calculation, the accuracy and reliability of temperature rise prediction are greatly improved, thereby achieving an accurate assessment of the equipment's thermal stability.

[0050] Figure 1 A flowchart illustrating a method for determining the temperature rise of gas-insulated power transmission equipment, provided as an embodiment of this application. Figure 1 As shown, the method may include the following steps.

[0051] S101. Based on the structural parameters and material properties of the gas-insulated power transmission equipment, extract the geometric information of the equipment and construct a two-dimensional multi-section model of multiple standard sections; the two-dimensional multi-section model is used to characterize the three-dimensional electromagnetic field distribution characteristics of each standard section of the gas-insulated power transmission equipment.

[0052] For example, due to the long and straight structural characteristics of the standard segment, the electromagnetic field distribution along the axial direction within the standard segment is uniform. Utilizing this characteristic, the two-dimensional multi-section model can characterize the three-dimensional electromagnetic field distribution of the multiple standard segments, thereby achieving a dimensionality reduction solution to the three-dimensional field problem, greatly reducing the computational resource requirements of the traditional three-dimensional finite element method, and improving analysis efficiency.

[0053] For example, a standard section is part of the gas-insulated power transmission equipment, and its length is limited by manufacturing, transportation, installation, operation, and maintenance conditions. For instance, the standard section can be a straight module, corner module, compensator module, or isolation module of the gas-insulated power transmission equipment, etc., and is not limited here.

[0054] For example, since the axial dimension of gas-insulated power transmission equipment is much larger than its radial dimension, and the magnetic field distribution within a standard section has a small gradient along the axial direction and the gradient change is negligible, the electromagnetic field of a two-dimensional radial cross-section can be used to characterize the three-dimensional electromagnetic field distribution within the entire standard section. Multiple two-dimensional cross-sectional models of standard sections can be combined to obtain this two-dimensional multi-section model.

[0055] In one possible implementation, the phase conductors in the two-dimensional multi-section model are connected in series to the system power supply; the housings are connected in parallel through phase-to-phase shorting blocks and grounding wires to form a coupling relationship between the internal and external circuits; an air domain is established outside the housing, and Dirichlet boundary conditions are applied to the boundary of the air domain to reflect the real boundary conditions of the electromagnetic field around the equipment; for a three-phase housing structure, each housing is interconnected through phase-to-phase shorting blocks and grounding wires to reflect the real electrical connection characteristics.

[0056] The gas-insulated power transmission equipment is divided into multiple standard sections by external phase-to-phase shorting blocks. Each standard section is sealed at both ends with an insulator and filled with insulating gas. Each cross-section in the two-dimensional multi-section model corresponds to a typical standard section of the gas-insulated power transmission equipment. Therefore, heat transfer occurs through natural convection within a closed cavity without inlets or outlets. Except for the electrical connections at the ends of the standard sections, the axial temperature gradient is close to zero, simplifying the study of the heat transfer process.

[0057] S102. Based on this two-dimensional multi-section model, and combining Kirchhoff's voltage and current equations with the electromagnetic field control equations, a two-dimensional multi-section field-circuit coupling model is established to achieve the joint solution of the circuit degree of freedom and the electromagnetic field degree of freedom.

[0058] S103. Using this two-dimensional multi-section field-circuit coupling model, the eddy current field distribution and ohmic loss of the gas-insulated power transmission equipment are determined, providing heat source data for subsequent temperature rise analysis.

[0059] S104. The ohmic loss is taken as the heat source term in the control equation of the heat-fluid coupling field. The radial temperature rise inside the gas-insulated power transmission equipment is obtained by solving the finite volume method.

[0060] S105. Based on the radial temperature rise of the conductor under different operating conditions, and combined with the axial temperature field distribution inside the equipment, the overall thermal stability of the gas-insulated power transmission equipment is evaluated.

[0061] For example, based on the radial temperature rise inside the conductor under different operating conditions, and further combined with the axial temperature rise distribution law of the conductor, the thermal stability of the gas-insulated power transmission equipment under various operating conditions, especially transient conditions, is quantitatively evaluated to determine its operational safety margin and adaptability to extreme conditions.

[0062] This application employs a two-dimensional multi-section field-circuit coupling method to quickly, accurately, and comprehensively analyze the electromagnetic field distribution characteristics of gas-insulated power transmission equipment. Furthermore, by introducing ohmic losses into the heat-fluid coupling field as a heat source for temperature rise calculation, the accuracy and reliability of temperature rise prediction are greatly improved, thereby achieving an accurate assessment of the equipment's thermal stability. Moreover, the technical solution of this application is particularly suitable for transient temperature rise analysis of gas-insulated power transmission equipment under transient conditions such as short circuits, lightning impulse voltages, and switching overvoltages, effectively compensating for the shortcomings of traditional finite element methods in handling the transient electromagnetic fields and temperature rise coupling calculations of long-distance equipment.

[0063] Furthermore, the calculated ohmic loss distribution is introduced into the heat flow field coupling control equation as a heat source term for temperature rise calculation. This can effectively reflect the real heating characteristics of the conductor, shell, connecting parts and their adjacent media, thereby improving the accuracy and reliability of temperature rise calculation.

[0064] Therefore, this invention enables efficient and accurate assessment of the thermal stability of gas-insulated power transmission equipment, providing quantifiable multi-physics analysis basis for equipment design optimization and safe operation.

[0065] In one possible implementation, the two-dimensional multi-section field-circuit coupling model treats the magnetic vector potential, loop current, and node voltage corresponding to the multiple standard segments as unknown variables, and introduces port voltage degrees of freedom at each conductor port. A discretized equation is constructed by combining the electromagnetic field control equation and the circuit balance equation. The circuit balance equation is derived based on Kirchhoff's voltage law and current law. The discretized equation is expressed as follows:

[0066] ;

[0067] in, and Represents the stiffness matrix; A It is the magnetic vector potential matrix; I It is a loop current matrix; The load matrix represents the conduction current. This is the resistor matrix for the external circuit; For similar The matrix is ​​determined based on the conductor's geometry and material properties; For the inductance matrix of the external circuit; This is the external circuit port voltage matrix.

[0068] The above method can determine the loop current in gas-insulated power transmission equipment under transient voltage excitation. Therefore, the multi-section field-circuit coupling model helps to perform electromagnetic calculations on a wide range of gas-insulated power transmission equipment networks and ensures practicality and computational efficiency.

[0069] In some embodiments, the above equations and Discretizing in the time domain yields: ; Therefore, the transient loss per unit length of the conductive area in gas-insulated power transmission equipment for: ; ;in, It is the first Ohmic losses within each component and It refers to the current density inside the component and its conjugate; It is the total number of components in the conductive region. C The absolute temperature is conductivity at that time It is an element The area; σ 20 This refers to the electrical conductivity of aluminum alloy at 20°C. α It is the temperature coefficient of resistivity, typically taken as 0.0042; This is the effective value of the loss within the power frequency cycle. Thus, the transient loss of the conductor can be accurately calculated based on this two-dimensional multi-section field-circuit coupling model.

[0070] In one possible implementation, the electromagnetic field control equation is derived by dividing the two-dimensional multi-section model into multiple nodal elements using the finite element method, and combining... The coupling equations of magnetic vector potential and electric scalar potential are established to solve for the eddy current field distribution of each node element, thereby obtaining the magnetic field distribution in this two-dimensional multi-section model. Since there is no high-permeability iron material in this gas-insulated power transmission equipment, the magnetic field distribution can be obtained through the node elements. The eddy current field distribution is solved by a method to establish transient electromagnetic control equations.

[0071] In one possible implementation, the electromagnetic field governing equation is expressed in the frequency domain as follows:

[0072] ; ;

[0073] The electromagnetic field control equation is expressed in the time domain as follows:

[0074] ; ;

[0075] in, It is magnetic vector potential. It is the permeability. It is electrical conductivity. It is angular frequency. It is an electric scalar potential, and It is the source current density of the conductive rod. It is time. j It is the imaginary unit. I It is the loop current. S Let be the cross-sectional area of ​​the conductor.

[0076] For example, when calculating the temperature rise under single-phase short-circuit conditions, the equation can be expressed in the frequency domain using the electromagnetic field control equation; when dealing with short-circuit conditions of phase conductors with transient voltage waveforms, the equation can be expressed in the time domain using the electromagnetic field control equation.

[0077] In one possible implementation, the two-dimensional multi-section field-circuit coupling model further includes a potential balance equation established for each phase conductor; this potential balance equation is used to ensure the uniqueness of the equation set of the two-dimensional multi-section field-circuit coupling model; the potential balance equation is:

[0078] ;

[0079] in, , , They are respectively A , B , C External voltage source excitation in a three-phase circuit. , , and , , They represent A , B , C External resistance and inductance in a three-phase circuit; , , For load resistance, This is the effective value of the voltage source; I a , I b , I c They represent A , B , C Conduction current in a three-phase circuit; , , They representA , B , C Phase conductor potential in gas-insulated power transmission equipment in a three-phase circuit; Angular frequency, t For time; This indicates a delayed phase.

[0080] For example, since the number of cross sections in the two-dimensional multi-section field-circuit coupling model matches the number of standard segments, each standard segment has a corresponding cross section. Under the excitation of the external circuit, the voltage degree of freedom of the solid conductor represents the DC component of the total current; therefore, in the two-dimensional simulation, each phase conductor of the solid conductor requires an introduced voltage degree of freedom.

[0081] In one possible implementation, the two-dimensional multi-section field-circuit coupling model includes a first circuit and a second circuit. The first circuit consists of a voltage source, transmission line impedance, and load impedance, and is used to describe the power transmission process of the main circuit, realizing the coupling of magnetic field degree of freedom and circuit degree of freedom at the conductor port. The second circuit consists of a phase-to-phase shorting bar and a grounding wire, and is used to simulate the electromagnetic coupling effect of the phase-to-phase and grounding loops. Its current distribution in the shell and connection structure forms induced current or eddy current.

[0082] For example, you can refer to Figure 2 , Figure 2 This is a schematic diagram of a two-dimensional multi-section electromagnetic field-circuit coupling model provided in an embodiment of this application. The first circuit in this two-dimensional multi-section electromagnetic field-circuit coupling model is... u a , u b , u c , R ta , R tb , R tc , L ta , L tb , L tc ,as well as R la , R lb , R lc The circuit formed; the second circuit is R s11 ... R gn+1 , L s11 ... L gn+1, and the circuit formed by the grounding wire; and These represent the equivalent resistance and inductance values ​​of the phase-to-phase shorting busbar, respectively. =1,2; = 1,2,..., n+ 1. In this way, the magnetic and electric fields of gas-insulated power transmission equipment can be analyzed quickly, accurately, and comprehensively using this two-dimensional multi-section field-circuit coupling model. Furthermore, the ohmic loss can be used as the heat source for the heat-fluid coupling field equation to perform more accurate temperature rise calculations.

[0083] In one possible implementation, the thermal flow field coupling control equation is based on the mass conservation equation, momentum conservation equation, and energy conservation equation, according to... direction, direction and The direction is expanded into partial differential form; the governing equation for the coupled thermal-fluid field is as follows:

[0084] ;

[0085] in, , , respectively fluid along , , The velocity component in the direction; It is the pressure of the fluid; It is the dynamic viscosity of the fluid; , , respectively fluid along , , The volume force vector in the direction; It is the coefficient of thermal expansion of the fluid; Indicates the temperature of the fluid; It is the reference temperature of the fluid; , , They represent the gravitational force along the direction of gravity. , , Component of direction; It is specific heat capacity. It is the thermal conductivity of the fluid. t It is time; It is the heat source term per unit mass of fluid.

[0086] For example, the mass conservation equation, also known as the continuity equation, states that the mass in a fluid does not change with time, and its expression is: The momentum conservation equation, also known as the Navier-Stokes equation, shows that the momentum in a fluid is affected by the pressure gradient and viscous forces. Its expression is: The energy conservation equation, also known as the heat conduction equation, shows that the energy in a fluid is affected by convection, heat conduction, and heat sources. Its expression is: The heat flow field coupling equation is derived from this equation according to direction, direction and The direction is expanded into partial differential form.

[0087] in, It is the velocity vector of the fluid, measured in meters per second, and it is determined by the velocity vector along the direction of the fluid. , , directional velocity components , , composition. It is the pressure of a fluid, measured in Pascals. It is the dynamic viscosity of a fluid, measured in Pascals per second. It is the volume force vector of the fluid, with units of N / m. 3 It consists of three components , , The components represent the external forces acting on a unit volume of fluid. It is the coefficient of thermal expansion of a fluid, with units of K. -1 It represents the relative rate of change of fluid density with temperature. This indicates the temperature of the fluid, measured in Kelvin (K). It is the reference temperature of the fluid, measured in K, and is usually taken as the initial temperature of the fluid or the ambient temperature. It is the gravitational acceleration vector, with units of m / s². 2 It consists of three parts , , The components represent the direction and magnitude of gravity, typically taken as -9.8 m / s². 2 . It is specific heat capacity, measured in joules per kilogram (Kelvin). It is the thermal conductivity of a fluid, measured in watts per meter Kelvin (W / (m·K)), representing the fluid's ability to conduct heat. It is the heat source term per unit mass of fluid, with the unit being watts per kilogram (W / kg), representing the heat inside the fluid.

[0088] In one possible implementation, S104 may include: discretizing the control equation of the thermal-fluid coupling field using the finite volume method and solving it in conjunction with the thermal balance equation of the radial section to obtain the radial temperature distribution characteristics inside the conductor of the gas-insulated power transmission equipment; and determining the radial temperature rise of the conductor based on the temperature distribution characteristics.

[0089] For example, you can refer to Figure 3 This is a schematic diagram of the heat transfer process of a radial section of a gas-insulated power transmission equipment according to an embodiment of this application. Heat is transferred inside the conductor through convection and radiation.

[0090] The heat balance equation for this radial section can describe the natural convection heat transfer process, and the equation is as follows: ;in, and These represent the ohmic losses of the conductor and the casing, respectively. and These represent the heat transferred by the conductor through convection and radiation, respectively. and These represent the heat transferred by the casing through these two methods, respectively. Thus, by using ohmic losses as the heat source in the heat-fluid coupled field model, the transient temperature rise under short-circuit conditions can be calculated in the heat-fluid coupled field equations.

[0091] In one possible implementation, S105 may include: determining the conductor loss and housing loss of the gas-insulated power transmission equipment based on the two-dimensional multi-section field-circuit coupling model under different operating conditions; calculating the axial temperature field distribution inside the conductor based on the conductor loss and housing loss; obtaining the radial temperature rise and axial temperature rise based on the radial and axial temperature field distributions, respectively; and comprehensively evaluating the thermal stability of the gas-insulated power transmission equipment based on the radial and axial temperature rises.

[0092] For example, the process of determining the shell loss and conductor loss based on this two-dimensional multi-section field-circuit coupling model can be obtained by solving the relevant equations for the transient loss per unit length of the conductive region of the insulated power transmission equipment, which will not be elaborated here. Thus, by using the field-circuit coupling model to calculate the conductor loss and shell loss of the entire gas-insulated power transmission equipment, the transient temperature rise distributed along the axial space can be determined. Furthermore, the influence of the three-phase proximity effect on the loss and temperature rise can be considered, thereby enabling a comprehensive analysis of the transient temperature field in both the axial and radial spaces.

[0093] Figure 4 This application provides a flowchart of a process for determining the eddy current field distribution and temperature rise of gas-insulated power transmission equipment based on a two-dimensional multi-section field-circuit coupling model.

[0094] First, current excitation and boundary conditions are applied to the two-dimensional multi-section field-circuit coupling model to update the temperature. The conductivity at a given value is used to solve a two-dimensional multi-section field-path coupling model using the FEM (Finite Volume Method) to obtain the eddy current field distribution, and then the ohmic loss is obtained based on this eddy current field distribution. The fluid conductivity at this value is then updated based on this ohmic loss. The thermal property parameters are taken as follows, that is, the ohmic loss is used as the heat source of the heat-fluid coupling field equation, and the temperature rise is obtained by solving the heat-fluid coupling field equation through FVM. ; Determine the temperature rise T i+1 Does it satisfy the formula? ,in, The preset difference threshold is set by the user. (Regarding temperature rise...) If the formula is satisfied, output the temperature and flow rate field distribution and terminate the process; during temperature rise... If the formula is not satisfied, continue to update the temperature as described above. The conductivity step is adjusted until the temperature rises. The process ends once the formula is satisfied.

[0095] This application employs a two-dimensional multi-section field-circuit coupling method to quickly, accurately, and comprehensively analyze the electromagnetic field distribution characteristics of gas-insulated power transmission equipment. Furthermore, by introducing ohmic losses into the heat-fluid coupling field as a heat source for temperature rise calculation, the accuracy and reliability of temperature rise prediction are greatly improved, thereby achieving an accurate assessment of the equipment's thermal stability. Moreover, the technical solution of this application is particularly suitable for transient temperature rise analysis of gas-insulated power transmission equipment under transient conditions such as short circuits, lightning impulse voltages, and switching overvoltages, effectively compensating for the shortcomings of traditional finite element methods in handling the transient electromagnetic fields and temperature rise coupling calculations of long-distance equipment.

[0096] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0097] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A method for determining the temperature rise of gas-insulated power transmission equipment, characterized in that, The method includes: Based on the structural parameters and material properties of the gas-insulated power transmission equipment, the geometric information of the equipment is extracted, and a two-dimensional multi-section model of multiple standard sections is constructed. The two-dimensional multi-section model is used to characterize the three-dimensional electromagnetic field distribution characteristics of each standard section of the gas-insulated power transmission equipment. Based on the aforementioned two-dimensional multi-section model, a two-dimensional multi-section field-circuit coupling model is established through Kirchhoff's voltage and current equations and electromagnetic field control equations, thereby realizing the joint solution of circuit degrees of freedom and electromagnetic field degrees of freedom. The eddy current field distribution and ohmic loss of the gas-insulated power transmission equipment are determined by the two-dimensional multi-section field-circuit coupling model, providing heat source data for subsequent temperature rise analysis. The ohmic loss is used as a heat source term in the control equation of the heat-fluid coupling field. The radial temperature rise inside the gas-insulated power transmission equipment is obtained by solving the finite volume method. Based on the radial temperature rise of the conductor under different operating conditions, and combined with the axial temperature field distribution inside the equipment, the overall thermal stability of the gas-insulated power transmission equipment is evaluated.

2. The method according to claim 1, characterized in that, In the two-dimensional multi-section model, the phase conductors are connected in series to the system power supply; the shells are connected in series and parallel through phase-to-phase shorting blocks and grounding wires, forming a coupling relationship between the internal circuit and the external circuit; an air domain is established outside the shell, and Dirichlet boundary conditions are applied to the boundary of the air domain to reflect the real boundary conditions of the electromagnetic field around the equipment; for three-phase shells, the shells are interconnected through phase-to-phase shorting blocks and grounding wires to reflect the real electrical connection characteristics. The multiple standard sections are used to segment the gas-insulated power transmission equipment through external phase-to-phase shorting blocks. Each standard section is sealed at both ends with an insulator and filled with insulating gas. Each cross section in the two-dimensional multi-section model corresponds to a typical standard section of the gas-insulated power transmission equipment.

3. The method according to claim 1, characterized in that, The two-dimensional multi-section field-circuit coupling model uses the magnetic vector potential, loop current, and node voltage of the multiple standard segments as unknown variables, and introduces port voltage degrees of freedom at each conductor port. It constructs discretized equations by combining the electromagnetic field control equations and the circuit balance equations. The circuit balance equations are derived based on Kirchhoff's voltage law and current law. The discretized equations are expressed as follows: ； in, and Represents the stiffness matrix; A It is the magnetic vector potential matrix; I It is a loop current matrix; The load matrix represents the conduction current. This is the resistor matrix for the external circuit; For similar The matrix is ​​determined based on the conductor's geometry and material properties; For the inductance matrix of the external circuit; This is the external circuit port voltage matrix.

4. The method according to claim 1, characterized in that, The electromagnetic field control equations are used to divide the two-dimensional multi-section model into multiple nodal elements using the finite element method, and combined with... The coupling equations of magnetic vector potential and electric scalar potential are established to solve the eddy current field distribution of each node element, thereby obtaining the magnetic field distribution in the two-dimensional multi-section model.

5. The method according to claim 1, characterized in that, The electromagnetic field control equations are expressed in the frequency domain as follows: ； ； The electromagnetic field control equations are expressed in the time domain as follows: ； ； in, It is magnetic vector potential. It is the permeability. It is electrical conductivity. It is angular frequency. It is an electric scalar potential, and It is the source current density of the conductive rod. It is time. j It is the imaginary unit. I It is the loop current. S Let be the cross-sectional area of ​​the conductor.

6. The method according to claim 1, characterized in that, The two-dimensional multi-section field-circuit coupling model also includes a potential balance equation established for each phase conductor; the potential balance equation is used to ensure the uniqueness of the equation set of the two-dimensional multi-section field-circuit coupling model; the potential balance equation is: ； in, , , They are respectively A , B , C External voltage source excitation in a three-phase circuit. , , and , , They represent A , B , C External resistance and inductance in a three-phase circuit; , , They are respectively A , B , C Load resistance in a three-phase circuit This is the effective value of the voltage source. I a , I b , I c They represent A , B , C Conduction current in a three-phase circuit; , , They represent A , B , C Phase conductor potential in gas-insulated power transmission equipment in a three-phase circuit; Angular frequency, t For time; This indicates a delayed phase.

7. The method according to claim 1, characterized in that, The two-dimensional multi-section field-circuit coupling model includes a first circuit and a second circuit. The first circuit consists of a voltage source, transmission line impedance, and load impedance, and is used to describe the power transmission process of the main circuit, realizing the coupling of magnetic field degree of freedom and circuit degree of freedom at the conductor port. The second circuit consists of a phase-to-phase shorting bar and a grounding wire, and is used to simulate the electromagnetic coupling effect of phase-to-phase and grounding loops. Its current distribution in the shell and connection structure forms induced current or eddy current.

8. The method according to claim 1, characterized in that, The coupled control equations of the thermal flow field are based on the mass conservation equation, momentum conservation equation, and energy conservation equation, and are arranged according to... direction, direction and The direction is expanded into partial differential form; the coupled control equations of the heat flow field are as follows: ； in, , , respectively fluid along , , The velocity component in the direction; It is the pressure of the fluid; It is the dynamic viscosity of the fluid; , , respectively fluid along , , The volume force vector in the direction; It is the coefficient of thermal expansion of the fluid; Indicates the temperature of the fluid; It is the reference temperature of the fluid; , , They represent the gravitational force along the direction of gravity. , , Component of direction; It is specific heat capacity. It is the thermal conductivity of the fluid. t It is time; It is the heat source term per unit mass of fluid.

9. The method according to claim 1, characterized in that, The step of treating the ohmic loss as a heat source term in the heat-fluid coupling field control equation and solving it using the finite volume method to obtain the radial temperature rise inside the gas-insulated power transmission equipment includes: The control equations of the thermal-fluid coupling field are discretized using the finite volume method and solved in combination with the thermal balance equations of the radial section to obtain the radial temperature distribution characteristics inside the conductor of the gas-insulated power transmission equipment. Based on the temperature distribution characteristics, the radial temperature rise of the conductor is determined.

10. The method according to claim 9, characterized in that, The assessment of the overall thermal stability of gas-insulated power transmission equipment, based on the radial temperature rise of the conductor under different operating conditions and the axial temperature field distribution inside the equipment, includes: Under different operating conditions, the conductor loss and shell loss of the gas-insulated power transmission equipment are determined based on the two-dimensional multi-section field-circuit coupling model. Based on the conductor loss and the shell loss, calculate the temperature field distribution along the axial direction inside the conductor; Based on the temperature field distribution along the radial and axial directions, the temperature rise along the radial direction and the temperature rise along the axial direction are obtained respectively. The thermal stability of the gas-insulated power transmission equipment is comprehensively evaluated based on the radial and axial temperature rises.

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