Insulation structure electrical performance calculation method, system, equipment and medium

Abstract

The embodiment of the invention provides an insulation structure electrical performance calculation method, system and device and a medium, and the method comprises the steps: building an oil paper insulation material relative dielectric constant test platform, and obtaining the relative dielectric constant data of an oil paper insulation sample under different electric field intensities and different temperature conditions; based on the relative dielectric constant data of the oil-paper insulation sample, establishing a dependency relationship model among the relative dielectric constant of the oil-paper insulation material, the electric field intensity and the temperature; and establishing an electric-thermal-flow multi-physics field coupling model in the converter transformer, and based on the dependency relationship model, solving electric field distribution considering the dynamic change of the oil-paper insulating material relative to the dielectric constant through iterative calculation. According to the technical scheme provided by the invention, the relative dielectric constant field intensity and temperature dependence of the oil paper are considered, and the accuracy of calculating the internal electric field intensity of the converter transformer can be improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of converter transformers, and particularly relates to a method and system for calculating electrical performance of an insulation structure. BACKGROUND

[0002] Converter transformers bear AC and DC superimposed voltage on the valve side winding, resulting in more complex electric field distribution in the insulation structure than in AC transformers, which makes the failure rate of the converter transformers high. In the converter transformers, the response characteristics of the electrical materials change due to the working condition of bearing multiple physical fields at the same time, such as the strong coupling effect between the electric field, the magnetic field and the stress field, and the large electromagnetic coupling coefficient between the electric field and the magnetic field, which often shows the characteristics of magnetic-electric-force coupling. The current mainstream insulation structure design method ignores the influence of electric field, temperature and the like on the electrical performance such as the relative permittivity of oil-paper insulation materials, and is not suitable for the valve side main insulation structure of the converter transformer containing a large amount of DC voltage. SUMMARY

[0003] The method and system for calculating electrical performance of an insulation structure provided by the embodiments of the application consider the field strength and temperature dependence of the relative permittivity of oil-paper, and can improve the accuracy of the calculation of the internal electric field strength of the converter transformer.

[0004] In a first aspect, the embodiments of the application provide a method for calculating electrical performance of an insulation structure, comprising:

[0005] An oil-paper insulation material relative permittivity test platform is built to obtain the relative permittivity data of the oil-paper insulation sample under different electric field strengths and different temperatures;

[0006] A dependence relationship model between the relative permittivity of the oil-paper insulation material and the electric field strength and the temperature is established based on the relative permittivity data of the oil-paper insulation sample;

[0007] An internal electric-thermal-flow multi-physical field coupling model of the converter transformer is established, and the electric field distribution considering the dynamic change of the relative permittivity of the oil-paper insulation material is solved by iterative calculation based on the dependence relationship model.

[0008] In an optional implementation, the oil-paper insulation material relative permittivity test platform comprises a permittivity test loop, a blowing thermostat and a direct current conductivity test loop, the permittivity test loop comprises an upper computer, an alternating current power supply, a current acquisition card and a voltage acquisition card, the blowing thermostat comprises a test electrode and a sample container, and the direct current conductivity test loop comprises an upper computer, a direct current power supply and an electrometer; the test platform applies a test voltage to the oil-paper insulation sample through the alternating current power supply, collects voltage signals and current signals through the current acquisition card and the voltage acquisition card, and calculates the relative permittivity of the oil-paper insulation sample.

[0009] In an alternative embodiment, the test electrode adopts a three-electrode structure, and the oil-paper insulation sample is placed in a sample container and arranged between the three-electrode structure.

[0010] In an alternative embodiment, the calculation of the relative dielectric constant of the oil-paper insulation sample adopts a capacitance ratio method, and the relative dielectric constant is obtained by the ratio of the capacitance between the electrodes with the sample to the capacitance between the electrodes without the sample.

[0011] In an alternative embodiment, before obtaining the relative dielectric constant data of the oil-paper insulation sample, the method further comprises a preparation step of the oil-paper insulation sample, and the preparation step comprises: vacuum degassing and drying the insulation paper and the insulation oil, and immersing the insulation paper in the insulation oil at a preset temperature.

[0012] In an alternative embodiment, the conditions of the vacuum degassing and drying are: a temperature of 90°C, a vacuum degree of 90 Pa, and a duration of 48 hours.

[0013] In an alternative embodiment, the ratio of the insulation paper to the insulation oil is 20:1, and the immersion temperature is 40°C.

[0014] In an alternative embodiment, the method for establishing the dependence relationship model among the relative dielectric constant, the electric field strength, and the temperature of the oil-paper insulation material comprises:

[0015] Obtaining the relative dielectric constant data of the oil-paper insulation sample measured at a plurality of different temperature points and a plurality of different electric field strengths;

[0016] Performing curve fitting on the relative dielectric constant data of the oil-paper insulation sample to obtain a fitting function relationship of the relative dielectric constant of the oil-paper insulation material with respect to the electric field strength and the temperature.

[0017] In an alternative embodiment, the method for establishing the internal electro-thermal-flow multi-physical field coupling model of the converter transformer comprises:

[0018] Establishing a thermal-flow coupling model to calculate the temperature field distribution in the main insulation structure of the converter transformer;

[0019] Establishing an electro-thermal coupling model to calculate the electric field distribution in the main insulation structure of the converter transformer; wherein, the temperature field distribution is taken as an input of the electro-thermal coupling model.

[0020] In an alternative embodiment, the thermal-flow coupling model is established based on an energy conservation equation, and the energy conservation equation contains a convection heat transfer term caused by fluid flow and an internal heat source term generated by winding loss.

[0021] In an alternative embodiment, the winding loss includes direct current resistance loss and eddy current loss.

[0022] In an alternative embodiment, the calculation of the electric field distribution employs a two-dimensional DC electric field model based on Laplace equation, and the boundary conditions include high potential boundary, zero potential boundary and dielectric interface boundary.

[0023] In an alternative embodiment, the iterative calculation employs Newton-Raphson method to solve the partial differential equations of the electric field distribution and the dependency model.

[0024] In a second aspect, the embodiments of the present application provide a method for calculating electrical performance of an insulation structure, comprising:

[0025] An oil-paper insulation material relative permittivity test platform is configured to obtain relative permittivity data of an oil-paper insulation sample under different electric field intensities and different temperatures.

[0026] A dependency construction module is configured to establish a dependency model between the relative permittivity of the oil-paper insulation material and the electric field intensity and the temperature based on the relative permittivity data of the oil-paper insulation sample.

[0027] An electric field distribution calculation module is configured to establish an internal electric-thermal-flow multi-physical field coupling model of the converter transformer, and solve the electric field distribution considering the dynamic change of the relative permittivity of the oil-paper insulation material through iterative calculation based on the dependency model.

[0028] In a third aspect, the embodiments of the present application provide an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the method provided by the embodiments of the present application.

[0029] In a fourth aspect, the embodiments of the present application provide a computer readable storage medium, characterized in that a computer program is stored thereon, and when the computer program is executed in a computer, the computer is caused to execute the method provided by the embodiments of the present application.

[0030] The technical solutions provided by the embodiments of the present application have the following beneficial effects:

[0031] This invention establishes a test platform capable of precisely controlling electric field strength and temperature to measure the relative permittivity of oil-paper insulation materials under actual operating conditions. Based on experimental data, a model is constructed to demonstrate the dependence of the relative permittivity on electric field strength and temperature, transforming material parameters from fixed constants into dynamic functions that vary with the physical field. In electric field calculations, a non-uniform temperature field is obtained through electro-thermal-fluid coupling analysis. The Newton-Raphson iterative algorithm is then used to solve the dynamic material model and the electric field control equations (such as the Laplace equation), enabling the calculation results to more realistically simulate the complex insulation state of converter transformers under DC operating conditions, providing a more reliable basis for insulation design. This method reveals the interaction mechanism between temperature field and electric field distribution, especially the regulatory effect of the opposite trends in the dielectric constants of insulating oil and insulating paper with temperature on the electric field distribution, which can guide designers to more accurately assess insulation weaknesses. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating a method for calculating the electrical performance of an insulation structure according to an embodiment of this application;

[0033] Figure 2 This is a circuit diagram of an electrical performance testing platform for oil-paper insulation materials provided in an embodiment of this application;

[0034] Figure 3 This is a schematic diagram of the structure of a sample container provided in an embodiment of this application;

[0035] Figure 4 This is a schematic diagram of the field strength and temperature dependence test results of the relative permittivity of oil-paper insulation provided in an embodiment of this application; Figure 4 (a) is the relative permittivity of oil-electric field strength; Figure 4 (b) is the relative permittivity of paper - electric field strength;

[0036] Figure 5 This is a schematic diagram of a two-dimensional model structure of a sleeve provided in an embodiment of this application;

[0037] Figure 6 This is a schematic diagram of the temperature distribution of a bushing without considering nonlinearity, provided in an embodiment of this application.

[0038] Figure 7 This is a schematic diagram of the temperature distribution of a bushing considering nonlinearity, provided in an embodiment of this application. Detailed Implementation

[0039] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] This application provides a method for calculating the electrical performance of an insulation structure. Figure 1is a flowchart of a method for calculating electrical performance of an insulation structure, which can be executed by a system for calculating electrical performance of an insulation structure, which can be implemented by software and / or hardware, and can be configured in a computer or other electronic device.

[0041] As shown in Figure 1 , the technical solution provided by the embodiments of the present application includes the following steps:

[0042] S110, a test platform for relative dielectric constant of oil paper insulation material under different electric field strengths and temperatures is built, and relative dielectric constant data of the oil paper insulation sample under different electric field strengths and temperatures is obtained.

[0043] First, a test platform for testing relative dielectric constant of oil paper insulation material under different electric field strengths and temperatures is built, as shown in Figure 2 . The basic principle of material conductivity and relative dielectric constant test is to place the upper and lower surfaces of the sample between the test electrodes, apply a test voltage to the measured medium to charge the sample, and according to different test parameters (such as electric field strength, temperature, etc.), within the corresponding charging time, the conductivity and relative dielectric constant of the oil paper insulation sample are calculated according to the recorded current signal and voltage signal. As shown in Figure 2 , the test platform: the module in the left dashed box is a material dielectric constant test module, including an alternating current power supply, a current acquisition card, a voltage acquisition card, and a corresponding sample test circuit. The alternating current power supply is controlled by the host computer and can generate alternating voltage in a specific frequency range, and the current and voltage acquisition cards are used to collect the current flowing through the sample and the voltage applied to the sample, including the amplitude and phase information of the voltage and current. The voltage and current acquisition cards are connected to a computer to process the collected signals, and finally the relative dielectric constant of the material is calculated. The sample is connected to the test circuit through the electrodes, and the test electrodes adopt a flat three-electrode structure and are assembled with the sample in a sample container, as shown in Figure 3 , the structure of the sample container can reduce edge effects and ensure measurement accuracy. The air-blowing constant-temperature box is used to control the temperature during the test to simulate the performance test under different temperature conditions. The direct current conductivity test circuit includes a host computer, a direct current power supply, and an electrometer, which is used to test the conductivity.

[0044] Further, before obtaining the relative dielectric constant data of the oil paper insulation sample, the oil paper insulation sample is prepared, and the steps are as follows:

[0045] The KI-50X type insulating oil and the Wedman T4 type insulating paper board are selected as the test objects. The oil-paper insulation material is preprocessed by cutting the insulating paper sample into a length-width of 160*160 mm and a thickness of 2 mm, placing the insulating paper sample into a stainless steel tank, and drying the sample in a vacuum impregnation device at a temperature of 90 DEG C / 90 Pa for 48 h. The insulating oil sample is prepared and dried in the vacuum impregnation device at a temperature of 90 DEG C / 90 Pa for 48 h. After the insulating paper and the insulating oil are dried, the two are immersed in a drying oven at a preset temperature, the temperature of the drying oven is set to 40 DEG C, the dried insulating oil is added to the stainless steel tank at a temperature of 40 DEG C, the oil-paper ratio is 20:1, and then an appropriate amount of copper strip is added to simulate the internal condition of the transformer. Then, the stainless steel tank containing the oil-paper insulation sample is placed in the vacuum drying and impregnation oven, and the environment is kept at 90 DEG C / 90 Pa. After impregnation for 48 h, the sample is cooled to room temperature. The oil-paper insulation sample is taken out at room temperature and transferred to a sealed container for storage, and finally the oil-paper insulation sample to be tested is prepared.

[0046] In some embodiments, the oil-paper insulation relative dielectric constant test method is as follows:

[0047] The oil-paper insulation material relative dielectric constant test method is calculated by the oil-paper insulation sample's external working frequency alternating voltage and response current according to IEC60247-2007 and GB / T21216-2007 "Test method for determining dielectric loss factor of insulating liquid by measuring conductivity and capacitance". The test method recommended by the reference standard is that the relative dielectric constant of the material is the ratio of the capacitance between the electrodes with the sample to the capacitance between the electrodes filled with air without the sample. The working frequency alternating voltage is applied to the oil-paper insulation sample, and the voltage and current curves of the sample are obtained by the voltage and current acquisition card. The relative dielectric constant calculation formula is as follows:

[0048] ;

[0049] ;

[0050] In the formula, ε r is the relative dielectric constant of the material, C x is the capacitance of the sample, C a is the capacitance between the electrodes filled with air; ω is the voltage angular frequency at the working frequency, unit rad / s; U m is the maximum value of the applied voltage, unit V; I m is the maximum value of the response current of the sample, unit A; φ is the phase difference between the applied voltage and the response current.

[0051] The conductivity can be calculated by the following formula:

[0052] σ = i(t) / (E x A);

[0053] where i(t) represents the current, E is the electric field strength, and A is the electrode area.

[0054] In S120, a dependency model between the relative dielectric constant of the oil-paper insulation material and the electric field strength and temperature is established based on the relative dielectric constant data of the oil-paper insulation sample.

[0055] In some embodiments, the relative dielectric constant of the insulation oil and insulation paper sample is tested at different temperatures and electric field strengths. The test temperatures include 30°C, 60°C, and 90°C. The test electric field strength ranges from 0.1 kV / mm to 8 kV / mm. The test method refers to the relative dielectric constant test method in S110, and the results are shown in FIGS. 11A and 11B, respectively. Figure 4 (a), Figure 4 (b). Through the arrangement and analysis of a large amount of test data, a clear regularity is found. Specifically, the relationship between the relative dielectric constant and the electric field strength is as follows:

[0056] With the increase of the electric field strength, the relative dielectric constant of both the insulation oil and the insulation paper only shows a small range of irregular fluctuations. Based on this, an important conclusion can be drawn: the relative dielectric constant of the oil-paper insulation material is independent of the electric field strength in the electric field strength range concerned in this scheme. This discovery can significantly simplify the subsequent dependency model.

[0057] The relationship between the relative dielectric constant and the temperature is as follows: the change of the temperature has a significant and regular influence on the relative dielectric constant of the insulation oil and the insulation paper. With the increase of the temperature, the relative dielectric constant of the insulation oil shows a downward trend, with a maximum decrease of about 3.2%. The relative dielectric constant of the insulation paper increases slightly, with a maximum increase of about 4.3%. The temperature field affects the dielectric constant ε of the insulation oil and paper and paperboard, and this opposite change trend is crucial for accurately calculating the electric field distribution in the composite insulation system.

[0058] Since the relative dielectric constant ε r is independent of the electric field strength E, the dependency model can be simplified as a function only related to the temperature T. Therefore, the core task of the model is to find the mathematical expression of the change of the relative dielectric constant ε r of the insulation oil and the insulation paper with T, respectively. The mathematical method of curve fitting can be used. The experimental data of the relative dielectric constant at different temperatures obtained in step S120 are taken as known data points, and the least square method or other algorithms are used to find one or more continuous curves (such as linear, polynomial, and exponential) that best fit the change trend of these data points.

[0059] S130, an internal electric-thermal-flow multi-physical field coupling model of the converter transformer is established, and an electric field distribution considering dynamic changes of relative permittivity of oil-paper insulation materials is solved by iterative calculation based on a dependency model.

[0060] In some embodiments, the converter transformer insulation structure is in a complex environment jointly acted on by electric field, temperature field, fluid field (insulating oil flow), etc. in actual operation. It is necessary to clarify the interaction relationship between these physical fields, which is the basis for constructing an accurate calculation model.

[0061] Among them, the electric-thermal-flow coupling relationship: this is the most complete coupling relationship, which is used to accurately calculate the temperature field distribution in the insulation structure. In the calculation process, the electric charge is the source of the electric field, and the electric charge is affected by the electric field, the temperature field and the flow field. The joule heat loss of the electric field is the source of the temperature field. The temperature field affects the permittivity ε of the insulating oil and paper and paperboard. Secondly, the temperature field also causes the change of the viscosity coefficient η, which affects the flow field. Of course, the existence of the flow field will also cause the change of the convection coefficient h, which further affects the temperature field.

[0062] The existence of electric field, temperature field and flow field will also affect the electric charge. The temperature field and the electric field will change the ion mobility μ of the electric charge, and the existence of the flow field will change the movement speed v of the electric charge. In this way, a coupling relationship is formed with the electric charge as the field source, the temperature field as the core, and the electric field-temperature field-flow field affecting each other. The coupling logic is as follows:

[0063] Heat source: the joule loss (including direct current resistance loss and eddy current loss) of the electric field in the winding is the main heat source of the temperature field.

[0064] Thermal-flow interaction: the temperature field affects the viscosity of the insulating oil, thereby changing the flow field (oil flow rate U); the existence of the flow field affects the distribution of the temperature field through convective heat transfer.

[0065] Field and electric charge: electric field, temperature field and flow field jointly affect the migration and distribution of space charge, and electric charge is the source of electric field.

[0066] Among them, the electric-thermal coupling relationship: in this scheme, in order to balance the calculation accuracy and complexity, a simplified coupling strategy is adopted, that is, only the one-way coupling of temperature on material properties (relative permittivity) is considered. When analyzing the influence of temperature on electric field, an electric-thermal coupled field needs to be used. In the electric-thermal coupling relationship, the electric charge is the source of the electric field, and the energy flows to the electric field; the electric field energy also transfers to the temperature field, affecting the temperature field; the existence of the temperature field will change the permittivity ε of the electric field, affecting the electric field. Temperature field and electric field simultaneously affect the ion mobility μ of the electric charge, forming a coupling relationship between electric field-temperature field-charge. The relationship is:

[0067] Temperature field → Material property: The change of temperature field T will directly lead to the change of relative permittivity ε of oil-paper pair by the dependency model of step S120 r Changes.

[0068] Material property → Electric field: The change of ε r Will directly affect the distribution of electric field.

[0069] This solution ignores the reverse influence of the change of electric field distribution on heat source (loss), and the direct influence of the change of permittivity on temperature distribution. This simplification is reasonable and efficient in engineering.

[0070] In some embodiments, the temperature field distribution is calculated by thermal-fluid coupling. Under the guidance of explicit coupling relationship, the first step is to calculate the stable (steady-state) temperature field distribution in the insulation structure.

[0071] The heat source in the temperature distribution calculation mainly considers the load loss from the winding, mainly including: DC resistance loss in the winding, eddy current loss.

[0072] ;

[0073] ;

[0074] In the formula, represents the load loss, is the resistance loss, is the eddy current loss, is the rated current of the network side winding, is the rated current of the valve side winding, unit A, and are the equivalent resistances of the network side and valve side windings, respectively, unit Ω.

[0075] The coefficient of eddy current loss in the winding accounts for the DC loss of the winding, which can be estimated by the following formula:

[0076] ;

[0077] In the formula, represents the eddy current loss coefficient, which is used to estimate the eddy current loss, c is the thickness of the conductor, unit mm, represents the current density in the winding conductor, unit , represents the maximum leakage magnetic density in the main leakage magnetic channel, unit T, is a parameter related to resistivity.

[0078] The energy conservation equation of the steady-state temperature distribution can be shown by the following formula:

[0079] ;

[0080] where U is the velocity field vector of the fluid, which is a vector field containing the magnitude and direction of the velocity, with the unit m / s, is the fluid density, with the unit kg / m3, is the heat generation rate per unit volume, with the unit , is the constant pressure specific heat capacity, with the unit J / (kg·K), and T represents the temperature, is the convection term, which represents the heat taken away due to the flow of the fluid (oil flow), is the internal heat source, which represents the heat generated per unit volume (heat generation rate), and the difference between the two gives:

[0081] The heat entering through heat conduction = the heat taken away by fluid motion + the heat generated by the internal heat source;

[0082] This means that in any small volume: since it is a steady state, the temperature field does not change with time, so the heat reaches equilibrium.

[0083] In some embodiments, the electric field distribution calculation under the electric-thermal coupling is based on the basic equation in the differential form of the electrostatic field, uses the Laplace equation and the boundary conditions, and establishes a two-dimensional direct current electric field distribution solving equation:

[0084] ;

[0085] where ε r (E,T) is a function of the relative permittivity of oil-paper insulation with respect to the electric field intensity and temperature, (x,y) represents the spatial coordinates in the two-dimensional model, U0 represents a known high potential value, E represents the electric field intensity, T represents the temperature, and is mainly obtained through experiments and fitting, is the entire solving domain, is the known high potential boundary (usually set as the valve side, network side winding, etc. in the transformer); is the zero potential boundary (usually the transformer oil tank wall, core and yoke, etc.); is the normal direction of the boundary; represents the boundary of the two media. The electric field analysis and calculation problem in the above formula can be reduced to a boundary value problem with the potential function as the quantity to be solved.

[0086] In some embodiments, the electric field calculation process considers the electro-thermal coupling characteristics of the relative permittivity. Since there is a significant nonlinear relationship between the relative permittivity of the oil-paper insulation material and the electric field strength and temperature, the electric field and temperature in the main insulation structure affect the relative permittivity of the oil-paper insulation. Changes in the material's relative permittivity affect the electric field distribution within the insulation structure. To account for the influence of non-uniformly distributed temperature on the electric field distribution during the calculation process, a thermo-fluid coupling calculation is first performed to obtain the steady-state temperature distribution in the main insulation structure. Using the Newton-Raphson iterative method, the partial differential equations for solving the electric field are combined with the nonlinear relative permittivity equation of the oil-paper, thus incorporating the dynamically changing relative permittivity of the oil-paper under the influence of field strength and temperature during the electric field calculation. In the electro-thermal coupling calculation process, only the unidirectional coupling of temperature to the material's relative permittivity is considered; the influence of changes in the material's relative permittivity on the temperature distribution is not considered.

[0087] Solve using the Newton-Raphson iterative method:

[0088] Electric field equations:

[0089] ;

[0090] Where, ε r The relative permittivity is a key variable. Its biggest difference from the traditional formula is that it is not a fixed constant, but a function of the electric field strength E and the temperature T.

[0091] Dielectric constant equation: ε r =f(E,T)

[0092] This is a dependency model obtained by fitting experimental data.

[0093] Based on the nonlinear coupling relationship between the two formulas above, the Newton-Raphson iterative method is used until the potential field is reached. The convergence yields the electric field distribution in the main insulation structure of the converter transformer, considering the field strength and temperature dependence of the dielectric constant of the oil paper.

[0094] In one embodiment, taking a casing as an example, calculations and comparisons are performed. The two-dimensional model of the casing is as follows: Figure 5 As shown:

[0095] To maintain the safe and stable operation of transformers, the bushing failure rate must be controlled at an extremely low level. The centrally symmetric steady-state heat control equation can be expressed as follows:

[0096] ;

[0097] In the formula, T(r) represents the radial temperature distribution inside the insulating medium of the bushing cylinder, r represents the radial coordinate, i.e., the radius of the bushing cylinder, and k i Let g(r) be the thermal conductivity of the medium, and g(r) be the heat generation rate inside the insulating medium, with the following formula:

[0098] ;

[0099] In the formula: ε(r) is the conductivity of the insulating medium, E(r) is the radial electric field strength, and I is the leakage current inside the insulating junction. The formula for the conductivity of the insulating medium is defined as follows:

[0100] ;

[0101] In the formula, A is a constant related to the inherent properties of the insulating medium, a is a coefficient related to the electric field strength, and b is the Boltzmann constant, which is generally taken as . .

[0102] The conductivity of the insulating medium is a function of electric field strength and temperature. Combining the two formulas above, we can obtain:

[0103] ;

[0104] The formula for calculating the Joule heat P1 of a current-carrying conductor is as follows:

[0105] ;

[0106] Where ρ l This refers to the resistivity of the current-carrying conductor. The length of the current-carrying conductor is represented by l. The conductor rod is a hollow cylinder with an inner diameter of r1 and an outer diameter of r2.

[0107] In the electrothermal coupling field, the electric field distribution is obtained by combining electric field finite element calculations (using finite element software such as COMSOL). The loss density distribution is then further obtained by combining the intrinsic loss parameters of the insulating material. Considering the nonlinear variation of capacitor core dielectric loss with temperature, the nonlinear function is fitted according to actual conditions, and the final formula for calculating dielectric loss per unit volume is as follows:

[0108] ;

[0109] Among them, p1=3.165e-08, p2=-5.928e-06, p3=0.0004009, p4=-0.01291, and p5=0.4484. The fitted R-squared value reached 0.9939, indicating a good fit.

[0110] Let be the dielectric constant of the material at a point in the field, and E be the electric field strength at that point. The loss factor and relative permittivity of the insulating dielectric are shown in Table 1.

[0111] Table 1 Relative permittivity of insulating materials

[0112]

[0113] The simulation yielded temperature distribution cloud maps with and without considering the nonlinearity of the capacitor core insulating paper, as shown below. Figure 6 and Figure 7 As shown.

[0114] By comparing the overall temperature field distribution of the capacitor core insulating oil paper without considering nonlinearity, a significant decrease in overall temperature is observed when considering the nonlinearity of the oil paper, primarily in the oil conservator and the insulating oil inside the porcelain bushing. This demonstrates that the proposed scheme can more accurately reflect the actual electric field distribution in the insulation structure, especially in areas with significant temperature gradients, where the calculation accuracy is significantly improved, thus providing a more reliable basis for insulation design.

[0115] This application also provides a system for calculating the electrical performance of insulation structures, the system comprising:

[0116] A testing platform for the relative permittivity of oil-paper insulation materials is used to obtain relative permittivity data of oil-paper insulation samples under different electric field strengths and temperature conditions.

[0117] The dependency construction module is used to establish a dependency model between the relative permittivity of oil-paper insulation material and electric field strength and temperature based on the relative permittivity data of oil-paper insulation samples.

[0118] The electric field distribution calculation module is used to establish a multi-physics coupling model of electric-thermal-fluid fields inside the converter transformer. Based on the dependency model, it solves the electric field distribution considering the dynamic change of the relative permittivity of the oil-paper insulation material through iterative calculation.

[0119] The execution process of the system part of this application embodiment is the same as that of the method part of the embodiment described above, and will not be repeated here.

[0120] This application also provides an electronic device, including: at least one processor; a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to execute any of the new energy-based power grid multi-resource coordinated control methods.

[0121] This application also proposes a computer storage medium storing a computer program, which, when executed by a processor, implements any one of the new energy-based power grid multi-resource coordinated control methods.

[0122] Computer storage media may be simply referred to as media. Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Dual Data SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), Rambus Direct RAM (RDRAM), Direct Memory Bus Dynamic RAM (DRDRAM), and Memory Bus Dynamic RAM (RDRAM). The various embodiments described in this specification are presented in a progressive manner, and similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, for embodiments of apparatus, devices, and non-volatile computer storage media, since they are substantially similar to the method embodiments, the description is relatively simple, and relevant parts can be referred to the description of the method embodiments.

[0123] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A method of calculating electrical properties of an insulation structure, characterized by, The method comprises the following steps: A test platform for relative dielectric constant of oil-paper insulation material is built, and relative dielectric constant data of oil-paper insulation samples under different electric field intensities and different temperatures are obtained; A dependence relationship model between the relative dielectric constant of oil-paper insulation material and the electric field intensity and temperature is established based on the relative dielectric constant data of the oil-paper insulation samples; An internal electric-thermal-flow multi-physical field coupling model of the converter transformer is established, and the electric field distribution considering the dynamic change of the relative dielectric constant of the oil-paper insulation material is solved by iterative calculation based on the dependence relationship model.

2. The method of claim 1, wherein, The test platform for relative dielectric constant of oil-paper insulation material comprises a dielectric constant test loop, a blast constant-temperature oven and a direct current conductivity test loop. The dielectric constant test loop comprises an upper computer, an alternating current power supply, a current acquisition card and a voltage acquisition card. The blast constant-temperature oven comprises test electrodes and a sample container. The direct current conductivity test loop comprises an upper computer, a direct current power supply and an electrometer. The test platform applies a test voltage to the oil-paper insulation sample through the alternating current power supply, acquires voltage signals and current signals through the current acquisition card and the voltage acquisition card, and calculates the relative dielectric constant of the oil-paper insulation sample.

3. The method of claim 2, wherein, The test electrodes adopt a three-electrode structure, and the oil-paper insulation sample is placed in the sample container and arranged between the three-electrode structure.

4. The method of claim 2, wherein, The calculation of the relative dielectric constant of the oil-paper insulation sample adopts a capacitance ratio method, and is obtained by the ratio of the capacitance between the electrodes with the sample to the capacitance between the electrodes without the sample.

5. The method of claim 1, wherein, Before the relative dielectric constant data of the oil-paper insulation sample are obtained, a preparation step of the oil-paper insulation sample is further included, which comprises: vacuum degassing and drying the insulation paper and the insulation oil, and immersing the insulation paper in oil at a preset temperature.

6. The method of claim 5, wherein, The conditions of the vacuum degassing and drying are: a temperature of 90℃, a vacuum degree of 90Pa and a duration of 48 hours.

7. The method of claim 5, wherein, The ratio of the insulation paper to the insulation oil is 20:1, and the immersion temperature is 40℃.

8. The method of claim 1, wherein, The dependence relationship model between the relative dielectric constant of the oil-paper insulation material and the electric field intensity and temperature is established, which comprises: The relative dielectric constant data of the oil-paper insulation sample measured at multiple different temperature points and multiple different electric field intensities are obtained; The relative dielectric constant data of the oil-paper insulation sample are curve-fitted to obtain a fitting function relationship of the relative dielectric constant of the oil-paper insulation material with respect to the electric field intensity and the temperature.

9. The method of claim 1, wherein, The internal electric-thermal-flow multi-physical field coupling model of the converter transformer is established, which comprises: A thermal-flow coupling model is established to calculate the temperature field distribution in the main insulation structure of the converter transformer; An electric-thermal coupling model is established to calculate the electric field distribution in the main insulation structure of the converter transformer, wherein the temperature field distribution is taken as the input of the electric-thermal coupling model.

10. The method of claim 9, wherein, The thermal-flow coupling model is established based on an energy conservation equation, and the energy conservation equation contains a convection heat transfer term caused by fluid flow and an internal heat source term generated by winding loss.

11. The method of claim 10, wherein, The winding loss comprises direct current resistance loss and eddy current loss.

12. The method of claim 9, wherein, The calculation of the electric field distribution adopts a two-dimensional direct current electric field model based on Laplace equation, and the boundary conditions comprise a high potential boundary, a zero potential boundary and a medium boundary.

13. The method of claim 9, wherein, The iterative calculation adopts a Newton-Raphson method to simultaneously solve partial differential equations of an electric field distribution and the dependency model.

14. A method of calculating electrical performance of an insulation structure, characterized by, Comprise: An oil-paper insulation material relative dielectric constant test platform is used to obtain oil-paper insulation sample relative dielectric constant data under different electric field intensities and different temperature conditions. A dependency construction module is used to establish a dependency model of oil-paper insulation material relative dielectric constant and electric field intensity and temperature based on the oil-paper insulation sample relative dielectric constant data. An electric field distribution calculation module is used to establish an electric-thermal-flow multi-physical field coupling model inside a converter transformer, and to solve an electric field distribution considering dynamic changes of oil-paper insulation material relative dielectric constant through iterative calculation based on the dependency model. 15.An electronic device comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the method of any one of claims 1-13.

16. A computer-readable storage medium, characterized in that, A computer program is stored thereon, and when the computer program is executed in a computer, the computer program causes the computer to execute the method of any one of claims 1-13.

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