Method and device for calculating temperature rise of transformer

Abstract

This application discloses a method and apparatus for calculating transformer temperature rise. The method includes: obtaining the ambient temperature of the area where the transformer is located and the load factor of the transformer at the current moment; determining the bottom oil temperature of the transformer based on the ambient temperature, load factor, and a first-layer model, wherein the bottom oil temperature is the oil temperature when the transformer oil flows through the bottom oil inlet of the transformer; inputting the bottom oil temperature into a second-layer model to obtain the hot oil temperature of the transformer output by the second-layer model, wherein the hot oil temperature is the oil temperature when the transformer oil flows through the winding area of ​​the transformer; inputting the hot oil temperature into a third-layer model to obtain the hot spot temperature of the transformer output by the third-layer model, wherein the first, second, and third-layer models are three mathematical models with different calculation logics, and the hot spot temperature is the temperature of the hottest spot inside the transformer. This application solves the technical problem of low efficiency in calculating the temperature rise of natural ester transformers in the prior art.

Description

Technical Field

[0001] This application relates to the field of transformer technology, and more specifically, to a method and apparatus for calculating transformer temperature rise. Background Technology

[0002] During transformer operation, excessively high hot spot temperatures can adversely affect the transformer's electrical performance. When the hot spot temperature exceeds the maximum withstand limit of the insulation material, the insulation will fail, thereby reducing the transformer's electrical reliability and lifespan. Therefore, accurately calculating the transformer's hot spot temperature is crucial for its proper use. Current technology typically correlates the temperature rise of the top oil layer and the temperature rise of the coil hot spot together to calculate the transformer's hot spot temperature.

[0003] However, in real-world scenarios, the relationship between the temperature rise of the top layer of oil and the temperature rise of the coil hotspots is highly complex, requiring the use of empirical coefficients such as the hotspot factor for auxiliary calculations. However, this method is only applicable to traditional mineral oil transformers. For natural ester transformers, which employ a novel cooling medium, it is impossible to quickly assess the temperature rise using analytical formulas based on mineral oil empirical coefficients; furthermore, there is a lack of experience and experimental data to correct the temperature rise calculations for natural ester transformers. Therefore, there is an urgent need for an algorithm based on the physical meaning of the natural ester oil circulation process to achieve rapid and accurate temperature rise assessment for natural ester transformers.

[0004] There is currently no effective solution to the above problems. Summary of the Invention

[0005] This application provides a method and apparatus for calculating the temperature rise of a transformer, which at least solves the technical problem of low efficiency in calculating the temperature rise of natural ester transformers in the prior art.

[0006] According to one aspect of the embodiments of this application, a method for calculating the temperature rise of a transformer is provided. The method includes: obtaining the ambient temperature of the area where the transformer is located and the load factor of the transformer at the current moment; determining the bottom oil temperature of the transformer based on the ambient temperature, the load factor, and a first-layer model, wherein the bottom oil temperature is the oil temperature when the transformer oil flows through the bottom oil inlet of the transformer; inputting the bottom oil temperature into a second-layer model to obtain the hot oil temperature of the transformer output by the second-layer model, wherein the hot oil temperature is the oil temperature when the transformer oil flows through the winding area of ​​the transformer; inputting the hot oil temperature into a third-layer model to obtain the hot spot temperature of the transformer output by the third-layer model, wherein the first-layer model, the second-layer model, and the third-layer model are three mathematical models with different calculation logics, and the hot spot temperature is the temperature of the hottest spot inside the transformer.

[0007] Furthermore, the aforementioned transformer is a natural ester transformer, and the aforementioned transformer oil is a natural ester oil.

[0008] Furthermore, the calculation method for the temperature rise of natural ester transformers also includes: before determining the bottom oil temperature of the transformer based on the ambient temperature, load factor, and first-layer model, determining the iron loss of the transformer and the stray losses of the transformer's metal structural components based on the electromagnetic parameters and structural parameters of the transformer. Here, the iron loss is the loss generated by the iron core in the transformer, and the metal structural components are the metal components in the transformer other than the iron core and transformer coils.

[0009] Furthermore, the calculation method for transformer temperature rise is as follows: Before determining the bottom oil temperature of the transformer based on the ambient temperature, load factor, and first-layer model, the DC resistance loss of the transformer coil is calculated using an analytical method based on the structural characteristics of the transformer coil when the rated conditions are met. The eddy current loss of the transformer coil when the rated conditions are met is calculated using a two-dimensional refined model. The rated conditions characterize the transformer operating at a preset temperature.

[0010] Furthermore, the method for calculating transformer temperature rise is as follows: Before determining the bottom oil temperature of the transformer based on the ambient temperature, load factor, and the first-layer model, multiple thermal characteristic parameters corresponding to the transformer oil are calculated. These multiple thermal characteristic parameters include at least viscosity, thermal conductivity, density, specific heat capacity, and coefficient of thermal expansion. The first-layer characteristic values ​​corresponding to the first-layer model are obtained. These first-layer characteristic values ​​are used to characterize the shape characteristics of the first-layer heat dissipation components, which are the heat dissipation components in the transformer corresponding to the first-layer model. The target thermal resistance of the transformer oil at the current moment is determined based on the multiple thermal characteristic parameters corresponding to the transformer oil and the first-layer characteristic values.

[0011] Furthermore, the method for calculating transformer temperature rise is as follows: After calculating multiple thermal characteristic parameters corresponding to the transformer oil, the second-layer characteristic values ​​corresponding to the second-layer model are obtained. These second-layer characteristic values ​​characterize the shape characteristics of the second-layer heat dissipation component, which is the heat dissipation component in the transformer corresponding to the second-layer model. Based on the multiple thermal characteristic parameters corresponding to the transformer oil and the second-layer characteristic values, the target thermal resistance of the winding region at the current moment is determined. The third-layer characteristic values ​​corresponding to the third-layer model are obtained. These third-layer characteristic values ​​characterize the shape characteristics of the third-layer heat dissipation component, which is the heat dissipation component in the transformer corresponding to the third-layer model. Based on the multiple thermal characteristic parameters corresponding to the transformer oil and the third-layer characteristic values, the target thermal resistance of the hot spot region at the current moment is determined.

[0012] Furthermore, the method for calculating transformer temperature rise also includes: before determining the bottom oil temperature of the transformer based on ambient temperature, load factor, and the first-layer model, constructing multiple functions based on stray losses of metal structural components, coil DC resistance losses, coil eddy current losses, and loss reference temperatures. These multiple functions include correction coefficients for the first-layer model losses changing with real-time temperature, correction coefficients for the second-layer model losses changing with real-time temperature, and correction coefficients for the third-layer model losses changing with real-time temperature. The correction coefficients for the first-layer model losses changing with real-time temperature characterize the correlation between the loss value of the first-layer heat source and the real-time temperature; the correction coefficients for the second-layer model losses changing with real-time temperature characterize the correlation between the loss value of the second-layer heat source and the real-time temperature; and the correction coefficients for the third-layer model losses changing with real-time temperature characterize the correlation between the loss value of the third-layer heat source and the real-time temperature.

[0013] Furthermore, the method for calculating transformer temperature rise also includes: obtaining the rated thermal resistance of the transformer oil when the transformer meets the rated conditions, and the first time constant corresponding to the first-layer model; determining the bottom oil temperature based on the ambient temperature, the first time constant, the rated thermal resistance of the transformer oil, the target thermal resistance of the transformer oil, the correction coefficient of the first-layer model loss with real-time temperature change, the load factor, and the oil circulation-related constant corresponding to the transformer; obtaining the second time constant corresponding to the second-layer model, and the rated thermal resistance of the winding area when the transformer meets the rated conditions; determining the hot oil temperature based on the oil circulation-related constant, the second time constant, the rated thermal resistance of the winding area, the target thermal resistance of the winding area, the correction coefficient of the second-layer model loss with real-time temperature change, the load factor, and the bottom oil temperature; obtaining the third time constant corresponding to the third-layer model, and the rated thermal resistance of the hot spot area when the transformer meets the rated conditions; determining the hot spot temperature based on the oil circulation-related constant, the third time constant, the rated thermal resistance of the hot spot area, the target thermal resistance of the hot spot area, the correction coefficient of the third-layer model loss with real-time temperature change, the load factor, and the hot oil temperature.

[0014] According to another aspect of the embodiments of this application, a transformer temperature rise calculation device is also provided, comprising: an acquisition module for acquiring the ambient temperature of the area where the transformer is located and the load factor of the transformer at the current moment; a determination module for determining the bottom oil temperature of the natural ester transformer based on the ambient temperature, the load factor, and a first-layer model, wherein the bottom oil temperature is the oil temperature when the transformer oil flows through the bottom oil inlet of the transformer; a first input module for inputting the bottom oil temperature to a second-layer model to obtain the hot oil zone temperature of the transformer output by the second-layer model, wherein the hot oil zone temperature is the oil temperature when the transformer oil flows through the winding area of ​​the transformer; and a second input module for inputting the hot oil zone temperature to a third-layer model to obtain the hot spot temperature of the transformer output by the third-layer model, wherein the first-layer model, the second-layer model, and the third-layer model are three mathematical models with different calculation logics, and the hot spot temperature is the hottest temperature inside the transformer.

[0015] Furthermore, the aforementioned transformer is a natural ester transformer, and the aforementioned transformer oil is a natural ester oil.

[0016] In this application, the transformer temperature rise is determined by obtaining the ambient temperature and the current load factor of the transformer, combined with three mathematical models. First, the ambient temperature of the transformer's location and the current load factor are obtained. Based on the ambient temperature, load factor, and the first-layer model, the bottom oil temperature of the transformer is determined. Then, the bottom oil temperature is input to the second-layer model to obtain the hot oil zone temperature of the transformer, output by the second-layer model. Finally, the hot oil zone temperature is input to the third-layer model to obtain the hot spot temperature of the transformer, output by the third-layer model. The bottom oil temperature is the oil temperature at the bottom inlet of the transformer; the hot oil zone temperature is the oil temperature at the winding area of ​​the transformer; the first, second, and third-layer models are three mathematical models with different calculation logics; and the hot spot temperature is the temperature of the hottest point inside the transformer.

[0017] As described above, this application obtains the transformer's ambient temperature and current load factor in real time, and calculates the transformer's hot spot temperature using a three-layer model (i.e., the first, second, and third layer models). Even with frequent changes in the transformer's load factor, this application can still determine the temperature with high accuracy, thus solving the problem of the lack of a rapid and accurate method for assessing the temperature rise of natural ester transformers in the prior art. Furthermore, this application does not require any empirical coefficients; it only needs to use the three-layer model to determine the transformer's bottom oil temperature, hot oil zone temperature, and hot spot temperature. This avoids the need for extensive testing to obtain empirical coefficients, thereby reducing the cost of determining the hot spot temperature and improving its efficiency.

[0018] Therefore, the technical solution of this application achieves the goal of obtaining a high-accuracy temperature rise of natural ester transformers without the need for empirical coefficients to assist in the calculation, thereby realizing the technical effect of improving the calculation accuracy of the temperature rise of natural ester transformers and solving the technical problem of low calculation efficiency of the temperature rise of natural ester transformers in the prior art. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0020] Figure 1 This is a flowchart of an optional method for calculating the temperature rise of a natural ester transformer according to an embodiment of this application;

[0021] Figure 2 This is a schematic diagram of an optional three-layer thermal path calculation model according to an embodiment of this application;

[0022] Figure 3 This is a schematic diagram of an optional refined coil loss calculation model according to an embodiment of this application;

[0023] Figure 4 This is a schematic diagram of the calculation principle of an optional first-layer model according to an embodiment of this application;

[0024] Figure 5 This is a schematic diagram of the calculation principle of an optional second-layer model according to an embodiment of this application;

[0025] Figure 6 This is a schematic diagram of the calculation principle of an optional third-layer model according to an embodiment of this application;

[0026] Figure 7 This is a schematic diagram of an optional temperature rise test short-circuit method according to an embodiment of this application;

[0027] Figure 8 This is a flowchart of another optional method for calculating the temperature rise of a natural ester transformer according to an embodiment of this application;

[0028] Figure 9 This is a schematic diagram of the calculation principle of an optional three-layer thermal path model according to an embodiment of this application;

[0029] Figure 10 This is a schematic diagram of an optional transformer temperature determination device according to an embodiment of this application. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0032] Example 1

[0033] Environmental protection is a topic of great concern. With increasing emphasis on environmental protection both domestically and internationally, the implementation of the new development philosophy and the active cultivation of new manufacturing models such as intelligent manufacturing, green manufacturing, and service-oriented manufacturing, along with the new concept of serving green power development, have gained widespread acceptance. As a crucial piece of equipment in the power grid, the selection of raw materials for transformers should play a unique role in promoting positive change in today's society and environment. The use of environmentally friendly natural ester insulating oil (vegetable oil) as a cooling and insulating medium in transformers is gradually being promoted and adopted both domestically and internationally.

[0034] Among them, natural ester insulating oil, as the main cooling medium for transformers, has a much higher kinematic viscosity than ordinary mineral oil. Although it meets relevant standards for transformer oil, the excessively high kinematic viscosity reduces the transformer's heat transfer efficiency. Due to its poor heat dissipation capacity, temperature rise calculation and cooling structure design are challenging aspects of designing transformers using natural ester insulating oil. The kinematic viscosity, coefficient of thermal expansion, thermal conductivity, and specific heat capacity of transformer oil all affect the transformer's heat dissipation performance. The kinematic viscosity of natural ester is much higher than that of mineral oil; the kinematic viscosity of natural ester at 40℃ is approximately 35 mmHg. 2 / s, while mineral oil is only 7-9mm 2 Therefore, when designing the heat dissipation of natural ester transformers, the difference in kinematic viscosity between natural ester and mineral oil should be taken into account to prevent the transformer's temperature rise from exceeding the limit.

[0035] Furthermore, due to its excellent overall performance, natural ester insulating oil possesses characteristics such as low loss, low partial discharge, strong overload capacity, and environmental friendliness, exhibiting superior environmental, safety, electrical, and economic benefits. Therefore, by rationally utilizing the properties of natural ester insulating oil, its comprehensive cost over its normal operating life is lower than that of traditional mineral oil transformers, making it an ideal replacement for mineral oil. These characteristics bring broad application prospects to the development of natural ester insulating oil transformers. However, due to the disadvantages in the physicochemical properties of natural ester insulating oil, the temperature rise of natural ester insulating oil transformers is higher than that of mineral oil transformers. Excessive temperature will adversely affect the electrical performance of the transformer. When the temperature exceeds the maximum withstand limit of the insulating material, the insulation will fail, reducing the electrical reliability and lifespan of the transformer. Therefore, accurately calculating the temperature rise of natural ester insulating oil transformers is of great significance for promoting their development and protecting their normal operation.

[0036] Current research on the thermal analysis of natural ester-insulated oil transformers reveals that using traditional mineral oil analytical formulas to calculate temperature rise distribution leads to significant errors, and no reliable analytical formula exists specifically for natural ester-insulated oil transformers. Numerical calculation models for temperature rise in natural ester-insulated oil transformers require substantial time for modeling, and fluid dynamics calculations also suffer from long computation times and convergence difficulties, making them unsuitable for electromagnetic design in engineering projects. Therefore, efficient and reliable temperature rise calculation methods are indispensable for advancing the development of natural ester-insulated oil transformers towards larger capacity and higher voltage applications.

[0037] The thermal circuit model method utilizes thermoelectric analogy theory to transform the thermal problem of a transformer into an equivalent circuit problem for solution. Compared to numerical calculation methods, the thermal circuit method offers advantages in terms of speed and efficiency, and is also more accurate and feasible than traditional analytical calculation methods. However, while traditional thermal circuit models have high accuracy in calculating transformer temperature rise under rated load conditions, they have significant errors in calculating temperature rise under non-rated load conditions. This is because traditional thermal circuit models use empirical coefficients such as hot spot factors to assist in the calculation of hot spot temperature rise, which has poor adaptability to special types of transformers and non-rated load conditions, and cannot directly calculate the temperature rise of natural ester insulating oil transformers. Natural ester insulating oil transformers, as liquid-immersed transformers, primarily operate under non-rated load conditions, and their temperature changes faster than traditional mineral oil transformers. Therefore, obtaining accurate empirical coefficients for natural ester insulating oil transformers is more difficult, resulting in significant errors in the calculated hot spot temperatures.

[0038] To address the aforementioned problems, this application provides an embodiment of a method for calculating the temperature rise of a natural ester transformer. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0039] Figure 1 This is a flowchart of an optional method for calculating the temperature rise of a natural ester transformer according to an embodiment of this application, as shown below. Figure 1 As shown, the method includes the following steps:

[0040] Step S101: Obtain the ambient temperature of the area where the transformer is located and the load factor of the transformer at the current moment.

[0041] In step S101, the transformer described above can be a natural ester transformer. Additionally, for ease of description, in this embodiment, the ambient temperature of the area where the transformer is located is represented by θ. a The load factor of the transformer at the current moment is represented by K.

[0042] Step S102: Determine the bottom oil temperature of the transformer based on the ambient temperature, load factor, and the first layer model.

[0043] In step S102, the bottom oil temperature is the oil temperature at the bottom oil inlet of the transformer. Specifically, when the transformer is a natural ester transformer, the transformer oil is natural ester oil.

[0044] Optionally, the first-level model described above is a mathematical model. Specifically, the first-level model can be represented by the following formula (1):

[0045]

[0046] Optionally, in the above formula, K is the load factor of the transformer at the current moment. α is a target coefficient determined based on the transformer's iron loss, the ohmic loss of the transformer's coils, and the stray losses of the transformer's metal structural components. θ b This refers to the bottom oil temperature of the transformer. Δθ b,r This refers to the bottom oil temperature rise of the transformer when it meets rated conditions, i.e., the bottom oil temperature θ under rated conditions. b and ambient temperature θ a The difference. R oil,r R represents the rated thermal resistance of the transformer oil when the transformer meets its rated conditions. oil τ represents the target thermal resistance of the transformer oil at the current moment. oil P represents the first time constant corresponding to the bottom oil temperature model. n is the transformer oil circulation-related constant.W,b This refers to the correction coefficient for the loss of the first-layer model corresponding to the bottom oil temperature model as a function of real-time temperature. Specifically, the correction coefficient for the loss of the first-layer model as a function of real-time temperature characterizes the relationship between the loss value of the first-layer heat source and temperature. The first-layer heat source is the heat source corresponding to the first-layer model, and the first-layer heat dissipation component is the heat dissipation component corresponding to the first-layer model in the transformer. Rated conditions characterize the transformer's operation at a preset temperature, for example, a preset temperature of 75 degrees Celsius. The bottom oil temperature model is the first-layer model.

[0047] Furthermore, the transformer temperature rise calculation method of this application can be applied not only to natural ester oil transformers but also to other types of transformers, such as mineral oil transformers. Preferably, since traditional mineral oil transformers require the use of empirical coefficients such as hot spot factors for auxiliary calculation when calculating temperature rise, and the relationship between the oil top layer temperature rise and the coil hot spot temperature rise in natural ester oil transformers is very complex, the transformer temperature rise calculation method of this application does not require the use of empirical coefficients such as hot spot factors for auxiliary calculation. Therefore, the technical solution of this application can achieve better technical results when applied to natural ester oil transformers than when applied to mineral oil transformers. Based on this, for ease of description, the following description will use a natural ester oil transformer as an example.

[0048] Step S103: Input the bottom oil temperature into the second layer model to obtain the transformer hot oil zone temperature output by the second layer model.

[0049] In step S103, the oil temperature in the hot oil zone is the oil temperature when the transformer oil flows through the winding area of ​​the transformer.

[0050] Optionally, the second-level model is also a mathematical model. Specifically, the second-level model can be represented by the following formula (2):

[0051]

[0052] In the above formula, P W,w Here, K is the correction factor for the loss of the second-level model as a function of real-time temperature, corresponding to the second-level model; K is the load factor of the transformer at the current moment; and θ is the coefficient of change. w R is the temperature of the hot oil zone of the transformer, n is the oil circulation constant of the transformer, and R is the temperature of the hot oil zone of the transformer. w Let τ be the target thermal resistance of the winding region at the current moment. w Δθ is the second time constant corresponding to the second-layer model. w,r To determine the hot oil temperature θ when the transformer meets its rated conditions. w and bottom oil temperature θ b The difference, R w,rThe rated thermal resistance of the winding region is defined as the value of the winding region when the transformer meets the rated conditions. The correction coefficient for the loss of the second-layer model as a function of real-time temperature is used to characterize the relationship between the loss value of the second-layer heat source and temperature. The second-layer heat source is the heat source corresponding to the second-layer model, and the second-layer heat dissipation component is the heat dissipation component corresponding to the second-layer model in the transformer.

[0053] Step S104: Input the hot oil temperature of the hot oil zone into the third layer model and obtain the hot spot temperature of the transformer output by the third layer model.

[0054] In step S104, the first-layer model, the second-layer model, and the third-layer model are three mathematical models with different calculation logics, and the hot spot temperature is the hottest temperature inside the transformer.

[0055] Optionally, the third-layer model is a mathematical model. Specifically, the third-layer model can be represented by the following formula (3):

[0056]

[0057] In the above formula, P W,h Here, K is the correction factor for the loss of the third-level model as a function of real-time temperature, corresponding to the third-level model; K is the load factor of the transformer at the current moment; and θ is the coefficient of change of the loss of the third-level model as a function of real-time temperature. h Let Δθ be the hot spot temperature of the transformer at the current moment. h,r To determine the hot spot temperature θ when the transformer meets its rated conditions. h and hot oil zone temperature θ w The difference, τ h R represents the third time constant corresponding to the third-level model, where n is the oil circulation-related constant of the transformer, and R is the time constant corresponding to the third-level model. h R is the target thermal resistance of the hotspot area at the current moment. h,r The rated thermal resistance of the hot spot area is defined as follows: when the transformer meets the rated conditions, the hot spot area is rated thermal resistance. The correction coefficient for the loss of the third-layer model as a function of real-time temperature is used to characterize the relationship between the loss value of the third-layer heat source and temperature. The third-layer heat source is the heat source corresponding to the third-layer model, and the third-layer heat dissipation component is the heat dissipation component corresponding to the third-layer model in the transformer.

[0058] It is important to note that traditional thermal circuit models are two-layer models that correlate the temperature rise of the top layer of transformer oil with the temperature rise of hot spots. However, the actual relationship between the temperature rise of the top layer of oil and the temperature rise of the coil hot spots is quite complex. Traditional thermal circuit models use empirical coefficients such as hot spot factors to assist in the calculation of both hot spot and top layer temperature rises, resulting in poor adaptability to special types of transformers and non-rated load conditions. Furthermore, extensive experimental research has revealed significant deviations between the hot spot temperatures obtained by the traditional two-layer thermal circuit model and measured values ​​under varying loads or overloads, indicating poor accuracy in calculating non-rated loads.

[0059] Unlike traditional two-layer thermal circuit models, this application uses a three-layer thermal circuit model to calculate the hot spot temperature of the transformer, based on the transformer's own cooling structure and the thermal characteristics of natural ester oil. Specifically, Figure 2 A three-layer thermal path calculation model based on the physical processes of the thermal cycle is shown, such as... Figure 2 As shown, the input to the first-layer model is the ambient temperature θ. a The output is the bottom oil temperature θ. b The input to the second-layer model is the bottom oil temperature θ. b The output is the temperature θ of the hot oil zone. w The input to the third-layer model is the temperature θ of the hot oil zone. w The output is the hotspot temperature θ. h .

[0060] In addition, Figure 2 In this model, three models are dynamic calculation models, and the parameters of natural ester oil and the thermal resistance in the model are corrected in real time at each step of the calculation. Among them, q Fe q Cu q St These are the iron loss of the transformer, the ohmic loss of the coil, and the stray loss of the metal structural components, respectively; q Cu1 q is the heat source for the hot oil zone of the coil. Cu2 C is the heat source for the hotspot temperature rise region. h C w C oil These represent the heat capacity of the hot spot area, the heat capacity of the winding area, and the heat capacity of the transformer oil, respectively. A reference temperature θ is added to the hot spot temperature rise calculation model. t θ is used to assist in calculating hotspot temperatures. t Based on the loss distribution characteristics, θ b and θ wThe calculations yielded the results. The three models in this application consider the impact of stray losses in the metal structural components on the transformer temperature rise, and clearly identify the heat sources in the hot oil zone and the hot spot temperature rise. Traditional thermal circuit calculation models neglect the impact of stray losses in the metal structure on the transformer temperature rise, which can cause significant errors for large-capacity transformers. The models in this application correct this problem.

[0061] Based on the content of steps S101 to S104 above, it can be seen that in this application, the method of obtaining the ambient temperature of the natural ester transformer and the load factor at the current moment, combined with three mathematical models, is used to determine the transformer temperature rise. First, the ambient temperature of the area where the transformer is located and the load factor of the transformer at the current moment are obtained. Then, the bottom oil temperature of the transformer is determined according to the ambient temperature, load factor, and the first-layer model. Then, the bottom oil temperature is input to the second-layer model to obtain the hot oil zone temperature of the transformer output by the second-layer model. Finally, the hot oil zone temperature is input to the third-layer model to obtain the hot spot temperature of the transformer output by the third-layer model. Among them, the bottom oil temperature is the oil temperature when the natural ester oil flows through the bottom oil inlet of the transformer; the hot oil zone temperature is the oil temperature when the natural ester oil flows through the winding area of ​​the transformer; the first-layer model, the second-layer model, and the third-layer model are three mathematical models with different calculation logics; and the hot spot temperature is the hottest temperature inside the transformer.

[0062] As described above, this application obtains the transformer's ambient temperature and current load factor in real time, and calculates the transformer's hot spot temperature using a three-layer model (i.e., the first, second, and third layer models). Even with frequent changes in the transformer's load factor, this application can still determine the hot spot temperature with high accuracy, thus solving the problem of the lack of a rapid and accurate method for assessing the temperature rise of natural ester transformers in the prior art. Furthermore, this application does not require any empirical coefficients; it only needs to use the three-layer model to determine the transformer's bottom oil temperature, hot oil zone temperature, and hot spot temperature. This avoids the need for extensive testing to obtain empirical coefficients, thereby reducing the cost of determining the hot spot temperature and improving its efficiency.

[0063] Therefore, the technical solution of this application achieves the goal of obtaining a high-accuracy temperature rise of natural ester transformers without the need for empirical coefficients to assist in the calculation, thereby realizing the technical effect of improving the calculation accuracy of the temperature rise of natural ester transformers and solving the technical problem of low calculation efficiency of the temperature rise of natural ester transformers in the prior art.

[0064] In an optional embodiment, the first-layer model is also referred to as the bottom oil temperature-ambient temperature mathematical model. To facilitate understanding of the principle of the first-layer model, the following derivation can be performed:

[0065] First, based on the established thermal circuit model and the defined heat source, a mathematical model of the thermal circuit is established, and the equation for the bottom oil temperature versus ambient temperature is derived as follows:

[0066]

[0067] Then, the relationship between the final bottom oil temperature rise and the rated bottom oil temperature rise at any given time is defined as follows:

[0068]

[0069] Then, by substituting formula (5) into the bottom oil temperature-ambient temperature equation (4), we can obtain the following formula (6):

[0070]

[0071] By transforming formula (6), we can obtain the following formula (7):

[0072]

[0073] It should be noted that, in order to obtain the target coefficient α in formulas (6) and (7), the transformer temperature calculation device can determine the iron loss of the transformer and the stray loss of the metal structural components of the transformer based on the electromagnetic parameters and structural parameters of the transformer. Here, the iron loss is the loss generated by the iron core in the transformer, and the metal structural components are the metal components in the transformer other than the iron core and the transformer coil.

[0074] Furthermore, the transformer temperature calculation device also constructs multiple functions based on the stray losses of the metal structural components, the DC resistance losses of the coils, the eddy current losses of the coils, and the transformer's loss reference temperature. These multiple functions include correction coefficients for the first-layer model losses changing with real-time temperature, correction coefficients for the second-layer model losses changing with real-time temperature, and correction coefficients for the third-layer model losses changing with real-time temperature. The correction coefficients for the first-layer model losses changing with real-time temperature are used to characterize the correlation between the loss value of the first-layer heat source and the real-time temperature. The correction coefficients for the second-layer model losses changing with real-time temperature are used to characterize the correlation between the loss value of the second-layer heat source and the real-time temperature. The correction coefficients for the third-layer model losses changing with real-time temperature are used to characterize the correlation between the loss value of the third-layer heat source and the real-time temperature.

[0075] Specifically, the transformer temperature calculation device can use analytical methods to calculate the transformer's iron loss q. Fe The ohmic loss q of the coil is calculated using analytical methods and a two-dimensional refined model method. Cu The stray loss q of the metal structural components in the transformer was calculated using a three-dimensional model. St Then, the transformer temperature calculation device calculates the target coefficient α according to the following formula (8).

[0076] α=q Cu / (q Fe +q St (8)

[0077] In addition, q in formula (7) Cu+Fe+St,r This represents the total loss of the transformer under rated conditions.

[0078] Furthermore, in order to determine the first-level model, the transformer temperature calculation device also needs to determine the correction coefficient for the first-level model loss as a function of real-time temperature, which can be expressed by the following formula (9):

[0079]

[0080] In formula (9), θ k The reference temperature for transformer losses; q Cu,DC,pu This refers to the DC resistance loss of the transformer coil when it meets rated conditions. The DC resistance loss of the coil can be used... Figure 3 The refined model shown is used to calculate q. Cu,EL,pu This is the sum of stray losses of the metal structural components and coil eddy current losses of the transformer when it meets the rated conditions.

[0081] Specifically, the transformer temperature calculation device, based on the structural characteristics of the transformer coil, uses an analytical method to calculate the DC resistance loss of the coil under rated conditions, and employs a two-dimensional refined model to calculate the eddy current loss of the coil under rated conditions. Here, rated conditions characterize the transformer operating at a preset temperature. Then, the transformer temperature calculation device sums the stray losses and eddy current losses to obtain the target loss value q. Cu,EL,pu .

[0082] In addition to constructing the correction coefficients for the first-layer model loss as a function of real-time temperature based on the target loss value, loss reference temperature, and coil DC resistance loss, the transformer temperature calculation device also constructs correction coefficients for the second-layer model loss as a function of real-time temperature and correction coefficients for the third-layer model loss as a function of real-time temperature based on the target loss value, loss reference temperature, and coil DC resistance loss. The correction coefficients for the first-layer model loss as a function of real-time temperature are used to characterize the correlation between the loss value of the first-layer heat dissipation component and the temperature. The correction coefficients for the second-layer model loss as a function of real-time temperature are used to characterize the correlation between the loss value of the second-layer heat dissipation component and the temperature. The correction coefficients for the third-layer model loss as a function of real-time temperature are used to characterize the correlation between the loss value of the third-layer heat dissipation component and the temperature.

[0083] In this embodiment, the correction factor for the loss of the second-layer model as a function of real-time temperature is P. W,w The correction factor for the loss of the third-layer model as a function of real-time temperature is represented by P. W,h express.

[0084] In one optional embodiment, since the thermal resistance calculation in the traditional thermal circuit model does not fully consider the thermal characteristics of transformer oil, the calculated temperature cannot fully reflect the nonlinear thermal characteristics of transformer oil as temperature changes. Therefore, in order to calculate the transient hot spot temperature under dynamic load, this application calculates the target thermal resistance R of the transformer oil at the current moment based on the principles of heat transfer. oil The target thermal resistance R of the winding region at the current moment. w The target thermal resistance R of the hotspot area at the current moment. h .

[0085] Specifically, since the nonlinear thermal group is mainly related to the viscosity, thermal conductivity, density, specific heat capacity, and coefficient of thermal expansion of the transformer oil, the transformer temperature calculation device also calculates multiple thermal characteristic parameters corresponding to the transformer oil. These multiple thermal characteristic parameters include at least viscosity, thermal conductivity, density, specific heat capacity, and coefficient of thermal expansion. Simultaneously, the transformer temperature calculation device also obtains the first-layer characteristic values ​​corresponding to the first-layer model and determines the target thermal resistance of the transformer oil at the current moment based on the multiple thermal characteristic parameters and the first-layer characteristic values. The first-layer characteristic values ​​characterize the shape characteristics of the first-layer heat dissipation component, which is the heat dissipation component in the transformer corresponding to the first-layer model.

[0086] Similarly, the transformer temperature calculation device also acquires the second-layer feature values ​​corresponding to the second-layer model, and determines the target thermal resistance of the winding region at the current moment based on multiple thermal characteristic parameters and the second-layer feature values; it acquires the third-layer feature values ​​corresponding to the third-layer model, and determines the target thermal resistance of the hot spot region at the current moment based on multiple thermal characteristic parameters and the third-layer feature values. The second-layer feature values ​​characterize the shape characteristics of the second-layer heat dissipation component, which is the heat dissipation component in the transformer corresponding to the second-layer model; the third-layer feature values ​​characterize the shape characteristics of the third-layer heat dissipation component, which is the heat dissipation component in the transformer corresponding to the third-layer model.

[0087] Specifically, the viscosity μ, thermal conductivity k, and specific heat capacity C of transformer oil are... p Density ρ can be defined by formulas (10) to (13):

[0088] μ = 5.9 - 0.05T + 0.00014T 2 -1.25×10-07 T 3 (10)

[0089] k = 0.64 - 0.0034T + 7.96 × 10 -06 T 2 -6.34×10 -09 T 3 (11)

[0090] C p =988.33-3.96T(12)

[0091] ρ=1176-0.73T(13)

[0092] In the thermal circuit model, the heat transfer process mainly takes place through the convection of transformer oil, and the thermal resistance of convection heat transfer is defined by formula (14):

[0093]

[0094] In formula (14), h is the heat transfer coefficient.

[0095] The relationship between the heat transfer coefficient h and the corresponding eigenvalue L of the model can be derived using the following formulas (15) to (19):

[0096]

[0097] Nu = C·[Gr·Pr] n (16)

[0098] In formula (16): Nu is the Nusselt number; C and n are the convective heat transfer correlation coefficients; Gr is the Grashof number; Pr is the Prandtl number.

[0099]

[0100]

[0101] Substituting formulas (16) to (17) into formula (18) yields formula (19):

[0102]

[0103] It should be noted that in formula (19), L represents the eigenvalue corresponding to the model. When the model is a first-level model, L represents the first-level eigenvalue corresponding to the first-level model. The target thermal resistance of the transformer oil at the current moment can be calculated according to formulas (19) and (14). When the model is a second-level model, L represents the second-level eigenvalue corresponding to the second-level model. The target thermal resistance of the winding region at the current moment can be calculated according to formulas (19) and (14). When the model is a third-level model, L represents the third-level eigenvalue corresponding to the third-level model. The target thermal resistance of the hot spot region at the current moment can be calculated according to formulas (19) and (14).

[0104] In an optional embodiment, the transformer temperature calculation device also obtains the rated thermal resistance of the transformer oil when the transformer meets the rated conditions, as well as the first time constant corresponding to the first layer model. Then, the transformer temperature calculation device determines the bottom layer oil temperature based on the ambient temperature, the first time constant, the rated thermal resistance of the transformer oil, the correction coefficient of the first layer model loss changing with real-time temperature, the load factor, and the oil circulation-related constant corresponding to the transformer.

[0105] Specifically, such as Figure 4 As shown, combining formulas (9) and (7), the transformer temperature calculation device can determine the first-layer model as formula (1):

[0106]

[0107] In addition, it should be noted that when calculating the bottom oil temperature, the influence of the rated temperature loss of the first layer model should also be considered. That is, based on the above formula (1), the transformer temperature calculation device can determine the bottom oil temperature according to the ambient temperature, the first time constant, the rated thermal resistance of the transformer oil, the target thermal resistance of the transformer oil, the rated temperature loss of the first layer model, the correction coefficient of the loss of the first layer model with the real-time temperature change, the load factor, and the oil circulation related constant of the transformer.

[0108] In an optional embodiment, similar to the derivation process of the formula for the first-layer model, the transformer temperature calculation device obtains the second time constant corresponding to the second-layer model and the rated thermal resistance of the winding region when the transformer meets the rated conditions. Then, it determines the hot oil temperature based on the oil circulation related constant, the second time constant, the rated thermal resistance of the winding region, the target thermal resistance of the winding region, the correction coefficient of the second-layer model loss with real-time temperature change, the load factor, and the bottom oil temperature.

[0109] Specifically, the defining equation for the second-level model is formula (20).

[0110]

[0111] like Figure 5 As shown, the derived second-layer model is:

[0112]

[0113] In addition, it should be noted that when calculating the oil temperature in the hot oil zone, the influence of the rated temperature loss of the second layer model should also be considered. That is, based on the above formula (2), the transformer temperature calculation device can determine the oil temperature in the hot oil zone according to the oil circulation related constant, the second time constant, the rated thermal resistance of the winding area, the target thermal resistance of the winding area, the rated temperature loss of the second layer model, the correction coefficient of the loss of the second layer model with the real-time temperature change, the load factor, and the bottom oil temperature.

[0114] Similarly, the transformer temperature calculation device obtains the third time constant corresponding to the third-layer model, as well as the rated thermal resistance of the hot spot area when the transformer meets the rated conditions. Then, it determines the hot spot temperature based on the oil circulation related constant, the third time constant, the rated thermal resistance of the hot spot area, the target thermal resistance of the hot spot area, the correction coefficient of the loss of the third-layer model with real-time temperature change, the load factor, and the oil temperature of the hot oil zone.

[0115] Specifically, the defining equation for the third-layer model is formula (21).

[0116]

[0117] like Figure 6 As shown, the derived third-layer model is:

[0118]

[0119] In addition, it should be noted that when calculating the hot spot temperature, the influence of the rated temperature loss of the third-layer model also needs to be considered. That is, based on the above formula (3), the transformer temperature calculation device can determine the hot spot temperature according to the oil circulation related constant, the third time constant, the rated thermal resistance of the hot spot area, the target thermal resistance of the hot spot area, the rated temperature loss of the third-layer model, the correction coefficient of the third-layer model loss with real-time temperature change, the load factor, and the oil temperature of the hot oil area. In addition, in Figure 6 The diagram also shows θ defined by the coil loss distribution characteristics. tThe reference temperature is used for calculating the temperature rise of the transformer. Specifically, in traditional thermal circuit models, the heat capacity and thermal resistance in the model are adjusted to fit the experimental results and adjust the accuracy of the calculation. However, this method is not universally applicable, which is one of the reasons for calculation errors in thermal circuit models. Therefore, identifying the heat source is key to accurately calculating the transformer temperature rise using the thermal circuit method. According to the oil circulation process inside the transformer, the transformer oil is heated by the core, coils, and metal structural components in the tank, then enters the radiator through the radiator pipes. After heat exchange with the outside air through the radiator fins, it enters the transformer tank again through the radiator pipes. The oil temperature at this point is the bottom oil temperature, and the heat source causing the bottom oil temperature to rise is the total transformer loss. The transformer oil at the bottom of the transformer enters the coil through the gaps between the pads, and is heated by the coil losses to form a hot oil zone in the coil. The heat source q in the hot oil zone model is... Cu1 This represents the total ohmic loss of a single coil. The selection of the heat source in the hot spot temperature rise model is crucial. Based on the calculated coil loss density, the ohmic loss density of the transformer coil is not uniformly distributed. The loss density at the ends is much higher than in the middle of the coil, while the loss density in the middle region remains relatively constant. This causes the hot spot temperature rise to generally occur in the upper part of the coil. Simultaneously, the loss density of the low-voltage coil is much higher than that of the high-voltage coil; therefore, the hot spot temperature rise generally occurs in the upper part of the low-voltage coil. Extensive experimental data shows that the hot spot temperature rise occurs within the upper 20% range of the low-voltage coil. Therefore, the hot spot temperature rise model in this application defines the loss in the upper 20% axial height region of the low-voltage coil as the equivalent heat source for the hot spot temperature rise. The hot spot temperature rise calculation model uses θ, defined by the coil loss distribution characteristics. t This temperature serves as a reference for calculating the temperature rise of hot spots.

[0120] θ t The calculation process is shown in formula (22).

[0121] θ t =(θ w -θ b )×0.8+θ w (twenty two)

[0122] In an optional embodiment, since the natural ester transformer in this application is a liquid-immersed transformer, a short-circuit method is used for temperature rise testing according to IEC 60076.1. The schematic diagram of the short-circuit test method is shown below. Figure 7 As shown, the real-time hotspot temperature of the transformer is measured using a fiber optic temperature measuring device. This device has 8 channels, and the fiber optic cables are embedded at the following locations: two points on the first disc of the high-voltage coil, separated by a support bar; two points on the third disc of the high-voltage coil, separated by a support bar; two points on the first disc of the low-voltage coil, separated by a support bar; and two points on the third disc of the low-voltage coil, separated by a support bar. Specifically, in... Figure 7In the diagram, T1 is the transformer under test, T2 is the auxiliary transformer, and C1 and C2 are compensation capacitors.

[0123] It should be noted that, based on the experimental results above, under a load factor of 1.0, when the transformer reaches a thermally stable state, the final temperature error of the thermal circuit model in this application is 2.2%, while the final temperature error of the traditional thermal circuit model is 4%. Under a load factor of 1.15, when the transformer reaches a thermally stable state, the calculation error of the thermal circuit model in this application is 3.1%, while the calculation error of the traditional thermal circuit model is 9.1%. Therefore, compared to the calculation results under rated load, the error of the traditional thermal circuit model is significantly increased, while the error of the thermal circuit model in this application does not change significantly and can still predict the hot spot temperature value relatively accurately.

[0124] In one alternative embodiment, Figure 8 A flowchart illustrating another method for calculating the temperature rise of a natural ester transformer according to an embodiment of this application is shown, such as... Figure 8 As shown, it includes the following steps:

[0125] Step S801: Calculate the heat source distribution;

[0126] Step S802: Based on the thermal cycle process of the natural ester insulating oil transformer, a three-layer thermal circuit calculation model is established, and there is a coupling relationship between each layer of the model.

[0127] Step S803: Derive the control equations for each layer of the model;

[0128] Step S804: Calculate the heat source, equivalent thermal resistance, and heat capacity parameters of each layer model according to the control equations.

[0129] Step S805: Calculate the transient thermal circuit model to obtain the temperature value of the natural ester insulating oil transformer.

[0130] The transformer heat source distribution calculated in step S801 includes coil losses, core losses, and stray losses of metal structural components. The coil losses are precisely calculated down to the DC resistance loss and eddy current loss of each individual conductor. This refined loss calculation model differs from traditional integrated loss calculation models, resulting in a more accurate heat source distribution.

[0131] In addition, the three-layer thermal path calculation models established in step S802 are the bottom oil temperature-ambient temperature thermal path model, the winding hot oil zone oil temperature-bottom oil temperature thermal path model, and the hot spot oil temperature-winding hot oil zone oil temperature thermal path model. For example... Figure 9 As shown, the model is a three-layer coupled computational model, the first layer model (i.e. Figure 9 The input to the transformer oil bottom layer temperature rise model is the current ambient temperature θ.a And the load factor K(t), the output is the bottom oil temperature θ b The second-level model (i.e.) Figure 9 The input to the transformer coil hot oil zone temperature rise model is the bottom oil temperature θ. b The output is the temperature θ of the hot oil zone. w The third-level model (i.e.) Figure 9 The input to the transformer winding hot spot temperature rise model is the hot oil zone temperature θ. h The output is the hotspot temperature θ. h Traditional thermal circuit calculation models neglect the impact of stray losses on transformer temperature rise, which can cause significant errors for large-capacity transformers. The model in this application corrects this problem.

[0132] Finally, the relevant parameters of the thermal circuit model calculated in step S804 include the heat source, heat capacity, and thermal resistance of each layer of the model. Since the thermal parameters of natural ester insulating oil, including specific heat capacity, density, viscosity, and thermal conductivity, all change with temperature, the heat source, heat capacity, and thermal resistance in the model defined in this application are not constants and need to be updated in real time during each iteration of the algorithm. That is, the model in this application is a dynamic calculation model, which can better track the temperature changes of the transformer, even under varying load conditions, and can accurately track the transformer temperature.

[0133] Therefore, the thermal circuit model in this application is based on the transformer's own cooling structure and the thermal characteristics of the transformer oil, and has strong adaptability to various types of transformers and various load conditions.

[0134] Example 2

[0135] According to an embodiment of this application, an embodiment of a transformer temperature determination device is also provided, such as... Figure 10 As shown, the device includes: an acquisition module 1001, used to acquire the ambient temperature of the area where the transformer is located and the load factor of the transformer at the current moment; a determination module 1002, used to determine the bottom oil temperature of the transformer based on the ambient temperature, load factor, and the first-layer model, wherein the bottom oil temperature is the oil temperature when the transformer oil flows through the bottom oil inlet of the transformer; a first input module 1003, used to input the bottom oil temperature to the second-layer model to obtain the hot oil zone temperature of the transformer output by the second-layer model, wherein the hot oil zone temperature is the oil temperature when the transformer oil flows through the winding area of ​​the transformer; and a second input module 1004, used to input the hot oil zone temperature to the third-layer model to obtain the hot spot temperature of the transformer output by the third-layer model, wherein the first-layer model, the second-layer model, and the third-layer model are three mathematical models with different calculation logics, and the hot spot temperature is the hottest temperature inside the transformer.

[0136] Optionally, the above-mentioned transformer is a natural ester transformer, and the above-mentioned transformer oil is a natural ester oil.

[0137] Optionally, the transformer temperature rise calculation device further includes: a first determining module, used to determine the iron loss of the transformer and the stray loss of the transformer's metal structural components based on the transformer's electromagnetic parameters and structural parameters, wherein the iron loss is the loss generated by the iron core in the transformer, and the metal structural components are the metal components in the transformer other than the iron core and transformer coils.

[0138] Optionally, the transformer temperature rise calculation device further includes: a first calculation module, used to calculate the DC resistance loss of the transformer coil under rated conditions using an analytical method based on the structural characteristics of the transformer coil, and to calculate the eddy current loss of the transformer coil under rated conditions using a two-dimensional refined model. Here, rated conditions characterize the transformer operating at a preset temperature.

[0139] Optionally, the transformer temperature rise calculation device further includes: a second calculation module, a first acquisition module, and a second determination module. The second calculation module is used to calculate multiple thermal characteristic parameters corresponding to the transformer oil, wherein the multiple thermal characteristic parameters include at least viscosity, thermal conductivity, density, specific heat capacity, and coefficient of thermal expansion; the first acquisition module is used to acquire the first layer feature values ​​corresponding to the first layer model, wherein the first layer feature values ​​are used to characterize the shape feature values ​​of the first layer heat dissipation component, and the first layer heat dissipation component is the heat dissipation component in the transformer corresponding to the first layer model; the second determination module is used to determine the target thermal resistance of the transformer oil at the current moment based on the multiple thermal characteristic parameters corresponding to the transformer oil and the first layer feature values.

[0140] Optionally, the transformer temperature rise calculation device further includes: a second acquisition module, a third determination module, and a fourth determination module. The second acquisition module is used to acquire the second-layer feature values ​​corresponding to the second-layer model, wherein the second-layer feature values ​​characterize the shape features of the second-layer heat dissipation component, which is the heat dissipation component in the transformer corresponding to the second-layer model. The third determination module is used to determine the target thermal resistance of the winding region at the current moment based on multiple thermal characteristic parameters corresponding to the transformer oil and the second-layer feature values. The third acquisition module is used to acquire the third-layer feature values ​​corresponding to the third-layer model, wherein the third-layer feature values ​​characterize the shape features of the third-layer heat dissipation component, which is the heat dissipation component in the transformer corresponding to the third-layer model. The fourth determination module is used to determine the target thermal resistance of the hot spot region at the current moment based on multiple thermal characteristic parameters corresponding to the transformer oil and the third-layer feature values.

[0141] Optionally, the transformer temperature rise calculation device further includes: a function construction module, used to construct multiple functions based on the stray losses of the metal structural components, the DC resistance loss of the coil, the eddy current loss of the coil, and the loss reference temperature of the transformer. Among these functions, the multiple functions include correction coefficients for the loss of the first-layer model changing with real-time temperature, correction coefficients for the loss of the second-layer model changing with real-time temperature, and correction coefficients for the loss of the third-layer model changing with real-time temperature. The correction coefficients for the loss of the first-layer model changing with real-time temperature are used to characterize the correlation between the loss value of the first-layer heat source and the real-time temperature. The correction coefficients for the loss of the second-layer model changing with real-time temperature are used to characterize the correlation between the loss value of the second-layer heat source and the real-time temperature. The correction coefficients for the loss of the third-layer model changing with real-time temperature are used to characterize the correlation between the loss value of the third-layer heat source and the real-time temperature.

[0142] Optionally, the transformer temperature rise calculation device further includes: a fourth acquisition module, a fifth determination module, a sixth determination module, a sixth acquisition module, and a seventh determination module. Specifically, the fourth acquisition module is used to acquire the rated thermal resistance of the transformer oil when the transformer meets rated conditions, and the first time constant corresponding to the first-layer model; the fifth determination module is used to determine the bottom oil temperature based on the ambient temperature, the first time constant, the rated thermal resistance of the transformer oil, the target thermal resistance of the transformer oil, the correction coefficient for the loss of the first-layer model changing with real-time temperature, the load factor, and the oil circulation-related constant corresponding to the transformer; the fifth acquisition module is used to acquire the second time constant corresponding to the second-layer model, and the rated thermal resistance of the winding region when the transformer meets rated conditions; the sixth determination module is used to determine the hot oil temperature based on the oil circulation-related constant, the second time constant, the rated thermal resistance of the winding region, the target thermal resistance of the winding region, the correction coefficient for the loss of the second-layer model changing with real-time temperature, the load factor, and the bottom oil temperature. The sixth acquisition module is used to acquire the third time constant corresponding to the third-layer model, and the rated thermal resistance of the hot spot area when the transformer meets the rated conditions; the seventh determination module is used to determine the hot spot temperature based on the oil circulation related constant, the third time constant, the rated thermal resistance of the hot spot area, the target thermal resistance of the hot spot area, the correction coefficient of the loss of the third-layer model with real-time temperature change, the load factor, and the oil temperature of the hot oil area.

[0143] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0144] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0145] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between units or modules may be electrical or other forms.

[0146] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0147] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0148] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, read-only memory (ROM), random access memory (RAM), portable hard drive, magnetic disk, or optical disk.

[0149] The above are merely preferred embodiments of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method of calculating temperature rise of a transformer, characterized by, The method comprises the following steps: obtaining a plurality of thermal characteristic parameters corresponding to transformer oil, wherein the plurality of thermal characteristic parameters at least include viscosity, thermal conductivity, density, specific heat capacity and thermal expansion coefficient; obtaining a first layer characteristic value corresponding to a first layer model, wherein the first layer characteristic value is used to represent a shape characteristic value of a first layer heat dissipation component, and the first layer heat dissipation component is a heat dissipation component corresponding to the first layer model in the transformer; determining a transformer oil target thermal resistance of the transformer oil at a current time according to the plurality of thermal characteristic parameters corresponding to the transformer oil and the first layer characteristic value; obtaining a second layer characteristic value corresponding to a second layer model, wherein the second layer characteristic value is used to represent a shape characteristic value of a second layer heat dissipation component, and the second layer heat dissipation component is a heat dissipation component corresponding to the second layer model in the transformer; determining a winding area target thermal resistance of a winding area at a current time according to the plurality of thermal characteristic parameters corresponding to the transformer oil and the second layer characteristic value; obtaining a third layer characteristic value corresponding to a third layer model, wherein the third layer characteristic value is used to represent a shape characteristic value of a third layer heat dissipation component, and the third layer heat dissipation component is a heat dissipation component corresponding to the third layer model in the transformer; determining a hotspot area target thermal resistance of a hotspot area at a current time according to the plurality of thermal characteristic parameters corresponding to the transformer oil and the third layer characteristic value; obtaining an ambient temperature of an area where the transformer is located and a load coefficient of the transformer at a current time; determining a bottom layer oil temperature of the transformer according to the ambient temperature, the load coefficient, the transformer oil target thermal resistance and the first layer model, wherein the first layer model refers to a bottom layer oil temperature-ambient temperature thermal circuit model, and the bottom layer oil temperature is an oil temperature when the transformer oil flows through a bottom oil inlet of the transformer; inputting the bottom layer oil temperature into the second layer model, and obtaining a hot oil area oil temperature of the transformer output by the second layer model according to the winding area target thermal resistance, wherein the second layer model refers to a winding hot oil area oil temperature-bottom layer oil temperature thermal circuit model, and the hot oil area oil temperature is an oil temperature when the transformer oil flows through a winding area of the transformer; inputting the hot oil area oil temperature into the third layer model, and obtaining a hotspot temperature of the transformer output by the third layer model according to the hotspot area target thermal resistance, wherein the third layer model refers to a hotspot oil temperature-winding hot oil area oil temperature thermal circuit model, the first layer model, the second layer model and the third layer model are three mathematical models with different calculation logics, and the hotspot temperature is the hottest point temperature inside the transformer.

2. The method of claim 1, wherein, The transformer is a natural ester transformer, and the transformer oil is a natural ester oil.

3. The method of calculating temperature rise of a transformer according to claim 1 or 2, characterized in that, Before determining the bottom layer oil temperature of the transformer according to the ambient temperature, the load coefficient and the first layer model, the method further comprises: Determine the iron loss of the transformer and the stray loss of a metal structural member of the transformer according to electromagnetic parameters and structural parameters of the transformer, wherein the iron loss is a loss generated by an iron core in the transformer, and the metal structural member is a metal member in the transformer other than the iron core and a transformer coil.

4. The method of claim 3, wherein, Before determining the bottom oil temperature of the transformer according to the ambient temperature, the load coefficient and a first layer model, the method further comprises: According to the structural characteristics of the transformer coil, the coil DC resistance loss of the transformer coil when meeting a rated condition is calculated by using an analytical method, and the coil eddy current loss of the transformer coil when meeting the rated condition is calculated by using a two-dimensional refined model, wherein the rated condition represents that the transformer works at a preset temperature.

5. The method of claim 4, wherein, Before determining the bottom oil temperature of the transformer according to the ambient temperature, the load coefficient and a first layer model, the method further comprises: According to the stray loss of the metal structural member, the coil DC resistance loss, the coil eddy current loss and a loss reference temperature of the transformer, a plurality of functions are constructed, wherein the plurality of functions include a correction coefficient of a first layer model loss varying with a real-time temperature, a correction coefficient of a second layer model loss varying with the real-time temperature and a correction coefficient of a third layer model loss varying with the real-time temperature, the correction coefficient of the first layer model loss varying with the real-time temperature is used to represent an association relationship between a loss value of a first layer heat source and the real-time temperature, the correction coefficient of the second layer model loss varying with the real-time temperature is used to represent an association relationship between a loss value of a second layer heat source and the real-time temperature, and the correction coefficient of the third layer model loss varying with the real-time temperature is used to represent an association relationship between a loss value of a third layer heat source and the real-time temperature.

6. The method of calculating temperature rise in a transformer according to claim 5, wherein, The method further comprises: Obtain a transformer oil rated thermal resistance of the transformer oil of the transformer when the transformer meets the rated condition, and a first time constant corresponding to the first layer model; Determine the bottom oil temperature according to the ambient temperature, the first time constant, the transformer oil rated thermal resistance, a transformer oil target thermal resistance, the correction coefficient of the first layer model loss varying with the real-time temperature, the load coefficient and an oil circulation related constant corresponding to the transformer; Obtain a second time constant corresponding to the second layer model, and a winding area rated thermal resistance of the winding area of the transformer when the transformer meets the rated condition; Determine the hot oil zone oil temperature according to the oil circulation related constant, the second time constant, the winding area rated thermal resistance, a winding area target thermal resistance, the correction coefficient of the second layer model loss varying with the real-time temperature, the load coefficient and the bottom oil temperature; Obtain a third time constant corresponding to the third layer model, and a hot spot area rated thermal resistance of the hot spot area of the transformer when the transformer meets the rated condition; Determine the hot spot temperature according to the oil circulation related constant, the third time constant, the hot spot area rated thermal resistance, a hot spot area target thermal resistance, the correction coefficient of the third layer model loss varying with the real-time temperature, the load coefficient and the hot oil zone oil temperature. The hot spot temperature is determined according to the oil circulation related constant, the third time constant, the hot spot area rated thermal resistance, the hot spot area target thermal resistance, the third layer model loss correction coefficient changing with real-time temperature, the load coefficient and the hot oil area oil temperature.

7. A device for calculating temperature rise of a transformer, characterized by comprising: Comprise: The second computing module is used for calculating a plurality of thermal characteristic parameters corresponding to transformer oil, wherein the plurality of thermal characteristic parameters at least include viscosity, thermal conductivity, density, specific heat capacity and thermal expansion coefficient; the first obtaining module is used for obtaining a first layer feature value corresponding to a first layer model, wherein the first layer feature value is used for representing shape feature value of a first layer heat dissipation component, and the first layer heat dissipation component is a heat dissipation component corresponding to the first layer model in the transformer; the second determining module is used for determining transformer oil target thermal resistance of the transformer oil at a current time according to the plurality of thermal characteristic parameters corresponding to the transformer oil and the first layer feature value; The second obtaining module is used for obtaining a second layer feature value corresponding to a second layer model, wherein the second layer feature value is used for representing shape feature value of a second layer heat dissipation component, and the second layer heat dissipation component is a heat dissipation component corresponding to the second layer model in the transformer; the third determining module is used for determining winding area target thermal resistance of a winding area at a current time according to the plurality of thermal characteristic parameters corresponding to the transformer oil and the second layer feature value; The third obtaining module is used for obtaining a third layer feature value corresponding to a third layer model, wherein the third layer feature value is used for representing shape feature value of a third layer heat dissipation component, and the third layer heat dissipation component is a heat dissipation component corresponding to the third layer model in the transformer; the fourth determining module is used for determining hot spot area target thermal resistance of a hot spot area at a current time according to the plurality of thermal characteristic parameters corresponding to the transformer oil and the third layer feature value; The obtaining module is used for obtaining ambient temperature of an area where the transformer is located and load coefficient of the transformer at a current time; The determining module is used for determining bottom layer oil temperature of the transformer according to the ambient temperature, the load coefficient, the transformer oil target thermal resistance and the first layer model, wherein the first layer model refers to bottom layer oil temperature-ambient temperature thermal circuit model, and the bottom layer oil temperature is oil temperature when the transformer oil flows through a bottom oil inlet of the transformer; The first input module is used for inputting the bottom layer oil temperature to the second layer model, and obtaining hot oil area temperature of the transformer output by the second layer model according to the winding area target thermal resistance, wherein the second layer model refers to winding hot oil area oil temperature-bottom layer oil temperature thermal circuit model, and the hot oil area oil temperature is oil temperature when the transformer oil flows through a winding area of the transformer; The second input module is configured to input the hot oil area oil temperature to the third layer model, and obtain the hot spot temperature of the transformer output by the third layer model according to the target thermal resistance of the hot spot area, wherein the third layer model refers to a hot spot oil temperature-winding hot oil area oil temperature thermal circuit model, the first layer model, the second layer model and the third layer model are three mathematical models with different calculation logics, and the hot spot temperature is the hottest spot temperature inside the transformer.

8. The apparatus for calculating temperature rise of a transformer according to claim 7, wherein The transformer is a natural ester transformer, and the transformer oil is natural ester oil.

Images