A method and system for calculating hot spot temperature rise of transformer windings

Abstract

The present application relates to the technical field of winding temperature rise calculation, and specifically to a method and system for calculating the temperature rise of transformer winding hot spots, the method comprising: establishing a model of the transformer temperature field at each calculation time step; constructing each temperature distribution matrix, obtaining each mode and its energy ratio at each calculation time step; numbering each mode at each calculation time step in the order of arrangement, obtaining the energy change value of each mode at each calculation time step, combining the distribution of the energy ratio of each mode with the same number at each calculation time step and its preset neighboring calculation time step, obtaining the weighted energy ratio of each mode at each calculation time step; then extracting the main mode of each calculation time step; by analyzing the difference between the energy ratio of each main mode at each calculation time step and the weighted energy ratio, obtaining the duration of the next calculation time step of each calculation time step, and obtaining the temperature rise of the transformer winding hot spot. The present application aims to improve the calculation accuracy of the winding hot spot temperature rise while ensuring the calculation efficiency of the winding hot spot temperature rise.

Description

Technical Field

[0001] The present application relates to the technical field of winding temperature rise calculation, and in particular to a method and system for calculating hot spot temperature rise of transformer windings. Background Art

[0002] During the operation of the transformer, the temperature rise of the hot spot of the winding is an important evaluation indicator reflecting its working status. Due to the influence of the complex electromagnetic environment inside the transformer, it is difficult to accurately sense the winding temperature field through sensors. At present, the research on the distribution characteristics of the temperature field inside the transformer is mainly carried out through indirect calculation.

[0003] In the process of modeling the transformer model using simulation software based on the principles of heat transfer and fluid mechanics, when dynamic modal decomposition is used to reduce the model order, the selection of the mode lacks a priori knowledge of the hotspot temperature rise changes, resulting in a decrease in the reliability of the selected mode and a decrease in the calculation accuracy of the hotspot temperature rise of the winding. Summary of the invention

[0004] In view of the above, it is necessary to provide a transformer winding hot spot temperature rise calculation method and system, which can improve the calculation accuracy of the winding hot spot temperature rise while ensuring the calculation efficiency of the winding hot spot temperature rise compared with the traditional transformer winding hot spot temperature rise calculation method:

[0005] In a first aspect, an embodiment of the present application provides a method for calculating the hot spot temperature rise of a transformer winding, the method comprising the following steps:

[0006] Establishing a transformer temperature field model at each calculation time step, wherein the model is an eight-division turn winding model;

[0007] Through the temperature distribution in the transformer temperature field at each calculation time step, each temperature distribution matrix is ​​constructed, and each mode of each temperature distribution matrix is ​​obtained by dynamic mode decomposition, and the energy ratio of each mode at each calculation time step is calculated;

[0008] The modes at each calculation time step are numbered in order of arrangement, and the energy change value of each mode at each calculation time step is obtained by analyzing the change of the energy ratio of each mode with the same number at each calculation time step and its preset neighboring calculation time step;

[0009] By using the energy change value, combined with the distribution of energy ratios of modes with the same number at each calculation time step and its preset neighboring calculation time step, a weighted energy ratio of each mode at each calculation time step is obtained; and by using the weighted energy ratio, the main mode at each calculation time step is extracted;

[0010] By analyzing the difference between the energy ratio and the weighted energy ratio of each main mode at each calculation time step, the duration of the next calculation time step of each calculation time step is obtained, and the temperature rise of the hot spot of the transformer winding is obtained.

[0011] In one embodiment, the method for obtaining the temperature distribution matrix is:

[0012] The temperatures of all nodes in the transformer temperature field at each calculation time step are combined into a temperature distribution vector at each calculation time step;

[0013] The temperature distribution vector is taken as a column vector, and the temperature distribution vectors at each calculation time step and the temperature distribution vectors at the previous preset number of calculation time steps are combined into a temperature distribution matrix.

[0014] In one embodiment, the process of obtaining the energy change value is:

[0015] Arrange the energy ratios of the modes with the same number at each calculation time step and the preset number of calculation time steps before it in a time sequence to form a modal energy ratio sequence of each mode at each calculation time step;

[0016] Divide each modal energy ratio sequence into each modal energy ratio subsequence, obtain the discreteness of all data in each modal energy ratio subsequence, and obtain the slope of the fitted straight line of the discreteness of all modal energy ratio subsequences of each modality at each calculation time step;

[0017] The energy change value of each mode at each calculation time step is determined by the slope of each mode at each calculation time step and the dispersion of the last modal energy ratio subsequence of each mode at each calculation time step.

[0018] In one embodiment, the energy change value is calculated as follows:

[0019] Mapping the slope of each mode at each calculation time step to a positive number;

[0020] The energy change value is the product of the dispersion of the last modal energy ratio subsequence of each mode at each calculation time step and the positive number.

[0021] In one embodiment, the process of obtaining the weighted energy ratio is:

[0022] Calculate the mean of the product of all energy ratios and their weights in each modal energy ratio sequence, where the weight of each energy ratio is positively correlated with its order in the modal energy ratio sequence;

[0023] The weighted energy ratio is obtained by combining the mean value of each mode at each calculation time step with the energy change value.

[0024] In one embodiment, the weighted energy ratio is the product of the mean value of each mode at each calculation time step and the energy change value.

[0025] In one embodiment, the main mode is extracted by:

[0026] The sum of the weighted energy ratios of all modes at each calculation time step is recorded as the total weighted energy ratio of each calculation time step;

[0027] The weighted energy ratios of all modes at each calculation time step are accumulated from large to small. When the accumulated result is greater than the product of the total weighted energy ratio and the preset ratio, the mode involved in the accumulation process is recorded as the main mode at each calculation time step.

[0028] In one embodiment, obtaining the duration of the next calculation time step of each calculation time step includes:

[0029] Arrange the energy ratios and weighted energy ratios of all main modes at each calculation time step in the same order to form the main mode energy ratio vector and the main mode weighted energy ratio vector of each calculation time step respectively;

[0030] Calculate the similarity between the main mode energy ratio vector and the main mode weighted energy ratio vector at each calculation time step;

[0031] The initial value of the absolute error limit is preset, and the absolute error limit at the adjacent next calculation time step of each calculation time step is positively correlated with the absolute error limit at each calculation time step and the similarity;

[0032] The step length of the adjacent next calculation time step is calculated according to the absolute error limit at the adjacent next calculation time step.

[0033] In one embodiment, the method for obtaining the absolute error limit at the adjacent next calculation time step of each calculation time step is:

[0034] Mapping the similarity into a non-negative value;

[0035] The product of the absolute error limit at each calculation time step and the non-negative value is used as the absolute error limit at the next adjacent calculation time step of each calculation time step.

[0036] In a second aspect, an embodiment of the present application also provides a transformer winding hotspot temperature rise calculation system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, the steps of any one of the above-mentioned methods for calculating the hotspot temperature rise of a transformer winding are implemented.

[0037] This application has at least the following beneficial effects:

[0038] The present application obtains energy change values ​​by analyzing the changes in modal energy at each calculation time step and multiple adjacent calculation time steps, reflecting the amount of change information of the transformer temperature field contained in each mode and the contribution of each mode to the change information of the transformer temperature field, thereby providing a basis for the extraction of the mode; further, when obtaining the weighted energy ratio of each mode at each calculation time step, a higher weight is given to the mode with a later time, emphasizing the recent modal energy ratio, which can more accurately reflect the dynamic change characteristics of the transformer temperature field; and then the main mode is selected by weighted energy ratio, which improves the reliability of the main mode selection, and can reduce the influence of reduced-order calculation on the obtained winding hot spot temperature rise accuracy while ensuring calculation efficiency;

[0039] Furthermore, by adjusting the calculation step in real time through the selected main mode, the calculation step can be reduced in the stage of rapid temperature change to capture the details of rapid changes and ensure the calculation accuracy of the hot spot temperature rise of the winding. In the stage of slow temperature change, the calculation step can be increased to reduce the amount of calculation and improve the calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 A flowchart of a method for calculating the hot spot temperature rise of a transformer winding provided in one embodiment of the present application;

[0042] Figure 2 A schematic diagram of the acquisition process of the main mode;

[0043] Figure 3 Schematic diagram of the process of obtaining the absolute error limit. DETAILED DESCRIPTION

[0044] In the description of the embodiments of the present application, words such as "exemplary", "or", "for example" and the like are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "or", "for example" and the like is intended to present related concepts in a concrete manner.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the present application. The terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. It should be understood that, unless otherwise specified, " / " means or.

[0046] It should also be noted that the terms "first" and "second" in the present application are used to distinguish similar objects rather than to describe a specific order or sequence.

[0047] The following is a detailed description of a method and system for calculating hot spot temperature rise of a transformer winding provided by the present application in conjunction with the accompanying drawings.

[0048] See also Figure 1 , which shows a flowchart of a method for calculating the hot spot temperature rise of a transformer winding provided by an embodiment of the present application, the method comprising the following steps:

[0049] Step 1: Establish a model of the transformer temperature field at each calculation time step.

[0050] This application takes a 110kV oil-immersed transformer as an example, uses Fluent software to establish an eight-division turn winding model, simulates the transformer temperature field through the eight-division turn winding model, and then obtains the hot spot temperature rise of the transformer winding. The specific process of using Fluent software to establish an eight-division turn winding model is well known to those skilled in the art, and this application will not be repeated.

[0051] The initial and boundary conditions of the simulation model of the transformer temperature field are set as follows: the initial oil flow rate is 0.05 m / s; the outer wall temperature of the transformer oil tank is 15 °C; the initial temperature of the transformer temperature field is 15 °C; the convection heat transfer coefficient is 10 W / (m 2 ·K); the transformer heat source adopts the method of volumetric heat source; the boundary type of the transformer temperature field simulation model adopts the non-slip wall. At the same time, the initial calculation time step of the transformer temperature field simulation model is 0.02s.

[0052] It should be noted that 0.02s is only an embodiment of the present application, and the implementer can set the specific value according to the actual situation, and the present application does not impose any special restrictions.

[0053] Step 2, construct each temperature distribution matrix through the temperature distribution in the transformer temperature field at each calculation step, use dynamic mode decomposition to obtain each mode of each temperature distribution matrix, and calculate the energy ratio of each mode at each calculation step; number each mode at each calculation step according to the arrangement order, and obtain the energy change value of each mode at each calculation step by analyzing the change of the energy ratio of each mode with the same number at each calculation step and its preset neighboring calculation step; obtain the weighted energy ratio of each mode at each calculation step through the energy change value, combined with the distribution of the energy ratio of each mode with the same number at each calculation step and its preset neighboring calculation step, and extract the main mode at each calculation step.

[0054] The temperatures of all nodes in the transformer temperature field at each calculation time step are combined to form a temperature distribution vector at each calculation time step, wherein the elements at the same position in all temperature distribution vectors correspond to the same node.

[0055] The temperature distribution vector is used as a column vector, and the temperature distribution vectors under each calculation time step and its adjacent first N-1 calculation time steps are arranged in time sequence to form a temperature distribution matrix under each calculation time step. Based on the temperature distribution matrix, dynamic mode decomposition is used to calculate the modal matrix and the original temperature field distribution coefficient matrix under modal characterization. The original temperature field distribution coefficient matrix contains the change information of each mode in the temperature field. Among them, different column vectors of the modal matrix represent different modes of temperature field change, and each mode is numbered according to the order of the column. The process of calculating the modal matrix and the original temperature field distribution coefficient matrix under modal characterization by dynamic mode decomposition is well known to those skilled in the art, and this application will not be repeated.

[0056] In this embodiment, the value of N is 100. The value of N is preset manually and can be set by the implementer. This application does not impose any special restrictions.

[0057] The row norm of each row of the original temperature field distribution coefficient matrix is ​​used as the energy ratio of the corresponding mode to characterize the importance of the corresponding mode in reflecting the temperature change characteristics of the winding under the current dynamic modal decomposition calculation. Since using all modes to predict the winding temperature will consume unnecessary time, the most important modes for the prediction of the winding temperature are selected from all modes. Among them, the calculation of the row norm is a well-known technology and will not be repeated in this application.

[0058] Since the oil-immersed transformer is disturbed by the on-site environment during actual operation, the temperature rise of the hot spots in the windings is not constant but is in dynamic change. When a short circuit or other fault occurs in some components in the winding, the temperature in the local area rises rapidly, and due to the lag of oil flow between winding turns, local overheating may occur. Therefore, the modal energy of different modes varies greatly.

[0059] When the main mode is selected by the energy ratio method, the mode is selected only according to the currently acquired modal energy, which lacks a priori knowledge of the hot spot temperature rise changes, resulting in a decrease in the accuracy of the mode selection, and then a decrease in the calculation accuracy of the hot spot temperature rise of the winding.

[0060] By analyzing the overall change of the modal energy ratio in each calculation time step and its adjacent N-1 calculation time steps, the main mode is selected to improve the calculation accuracy of the hot spot temperature rise of the winding.

[0061] The energy ratios of the modes with the same number at each calculation time step and its adjacent N-1 calculation time steps are arranged in time sequence to form a modal energy ratio sequence of each mode at each calculation time step; each modal energy ratio sequence is equally divided into M modal energy ratio subsequences.

[0062] In this embodiment, the value of M is 10. The value of M is preset manually and can be set by the implementer. This application does not impose any special restrictions.

[0063] Obtain the discreteness of all data in each modal energy ratio subsequence, and obtain the fitted straight line slope of the discreteness of all modal energy ratio subsequences of each mode at each calculation time step. The larger the slope of the fitted straight line, the greater the trend of the change degree of each modal energy, the more change information of the transformer temperature field contained in each mode, and the greater the probability of local high temperature in each mode. The calculation of the slope is a well-known technology and will not be repeated in this application.

[0064] In this embodiment, the discreteness is the standard deviation. As other implementation methods, on the basis of being able to measure the uneven distribution of all data in the modal energy ratio subsequence, the implementer may adopt other existing technologies for measurement, such as variance, coefficient of variation, etc., and this application does not impose any special restrictions.

[0065] In this embodiment, the least squares method is used to obtain the fitting straight line. The least squares method is a well-known technology and will not be described in detail in this application. As other implementation methods, on the basis of being able to obtain the fitting straight line, the implementer may use other existing technologies to obtain the fitting straight line, such as linear regression analysis, weighted least squares method, etc., and this application does not make any special restrictions.

[0066] When the modal energy ratio subsequence of any mode at any calculation time step is closer to the starting time of any calculation time step, the discreteness thereof reflects the accuracy of the change degree of the energy of any mode more accurately.

[0067] Based on the above analysis, the energy change value of each mode at each calculation time step is determined by the slope of each mode at each calculation time step and the discreteness of the last modal energy ratio subsequence of each mode at each calculation time step. The specific method is:

[0068] The slope of each mode at each calculation time step is mapped to a positive number; the energy change value is the product of the dispersion of the last modal energy ratio subsequence of each mode at each calculation time step and the positive number.

[0069] In this embodiment, the purpose of mapping the slope to a positive number is achieved by taking the slope as the exponent of an exponential function with a natural constant as the base. There are many methods for mapping data to positive numbers, and this application does not impose any special restrictions on this. The implementer can select other feasible methods at will. In this embodiment, the expression of the energy change value of each mode at each calculation time step is:

[0070] ; In the formula, represents the energy change value of the jth mode at the tth calculation time step; exp( ) represents an exponential function with a natural constant as the base, which is used to convert Mapped to positive numbers; represents the slope of the j-th mode at the t-th calculation time step; Represents the discreteness of the last modal energy ratio subsequence of the j-th mode at the t-th calculation step.

[0071] It should be noted that: Energy change value The larger it is, the more information about the change of transformer temperature field contained in the jth mode, and the greater the effect of the jth mode on improving the calculation accuracy of local temperature rise.

[0072] Furthermore, the weighted energy ratio of each mode at each calculation time step is obtained by combining the energy change value of each mode at each calculation time step with the distribution of the energy ratio in the modal energy ratio sequence of each mode at each calculation time step. The specific process is:

[0073] The mean of the products of all energy ratios and their weights in each modal energy ratio sequence is calculated, wherein the weight of each energy ratio is positively correlated with its order in the modal energy ratio sequence, and the product of the mean and the energy change value of each mode at each calculation time step is used as the weighted energy ratio of each mode at each calculation time step.

[0074] In this embodiment, the expression of the weight of each energy ratio is: ; In the formula, represents the weight of the i-th energy ratio in the modal energy ratio sequence; ln() represents a logarithmic function with a natural constant as the base, the purpose of which is to set a larger weight for the energy ratio that is later in time, so as to improve the reliability of the main mode selection; i represents the order of the energy ratio in the modal energy ratio sequence; C represents a preset value greater than 0, the purpose of which is to avoid the weight of the first energy ratio being 0. The value of C is preset manually and can be set by the implementer. In this embodiment, the value of C is 2.

[0075] In another embodiment, the weight of each energy ratio is its order in the modal energy ratio sequence.

[0076] The sum of the weighted energy ratios of all modes at each calculation time step is recorded as the total weighted energy ratio of each calculation time step; the weighted energy ratios of all modes at each calculation time step are accumulated from large to small. When the accumulated result is greater than the product of the total weighted energy ratio and the preset ratio, the mode involved in the accumulation process is recorded as the main mode of each calculation time step. The schematic diagram of the main mode acquisition process is shown in Figure 2 shown.

[0077] In this embodiment, the value of the preset ratio is 95%. The value of the preset ratio is preset manually and can be set by the implementer. This application does not impose any special restrictions.

[0078] Step 3, by analyzing the difference between the energy ratio of each main mode and the weighted energy ratio at each calculation step, the duration of the next calculation step of each calculation step is obtained, and the temperature rise of the hot spot of the transformer winding is obtained.

[0079] The calculation step size of the transformer temperature field simulation model directly affects the calculation accuracy and efficiency of the hot spot temperature rise of the winding. The adaptive variable step size method is used to reduce the step size when the truncation error is large, and to increase the step size when the truncation error is small, so as to ensure the calculation accuracy and efficiency of the transformer temperature field simulation model.

[0080] The absolute error limit is an important indicator for adjusting the calculation step size in the adaptive variable step size method. The larger the absolute error limit is set, the smaller the calculation step size is, and the higher the calculation accuracy of the transformer temperature field simulation model is.

[0081] Since the calculation accuracy of the fixed absolute error limit is insufficient when the transformer has an abnormal increase in local temperature and the transformer working state changes, it cannot meet the accurate calculation of the hot spot temperature rise of the transformer winding. Therefore, by analyzing the difference between the energy ratio and the weighted energy ratio of each main mode at each calculation time step, the absolute error limit at each calculation time step is updated. The specific process is as follows:

[0082] The energy ratios and weighted energy ratios of all main modes in each calculation time step are arranged in the same order to form the main mode energy ratio vector and the main mode weighted energy ratio vector of each calculation time step. Among them, the main mode energy ratio vector is used to reflect the modal energy change of the main mode in a single calculation time step when the neighboring calculation time step of each calculation time step is not considered, and the main mode weighted energy ratio vector is used to reflect the modal energy change of the main mode in the neighboring calculation time step when the neighboring calculation time step of each calculation time step is considered.

[0083] The greater the change in modal energy, the greater the difference between the main modal energy ratio vector and the main modal weighted energy ratio vector, and the greater the probability of local temperature rise in the transformer. At this time, the calculation time step should be set more densely, the smaller the absolute error limit should be set, the calculation step size should be reduced, and the calculation accuracy should be improved. The smaller the difference between the main modal energy ratio vector and the main modal weighted energy ratio vector, the larger the absolute error limit should be set, the larger the step size should be, and the calculation efficiency should be improved.

[0084] The absolute error limit at each calculation time step is updated by the difference between the main mode energy ratio vector and the main mode weighted energy ratio vector at each calculation time step. The specific process is:

[0085] The similarity between the main modal energy ratio vector and the main modal weighted energy ratio vector of each calculation time step is calculated, and the similarity is mapped to a non-negative value; the absolute error limit of the adjacent next calculation time step of each calculation time step is the product of the absolute error limit of each calculation time step and the non-negative value.

[0086] In this embodiment, the similarity is mapped to a non-negative value by adding a preset value δ greater than or equal to 1 to the similarity, wherein the value of δ is preset manually and can be set by the implementer. In this embodiment, the value of δ is 1. The expression for updating the absolute error limit at each calculation time step is:

[0087] ; In the formula, , Respectively represent the absolute error limits at the t+1th and tth calculation time steps; δ represents a preset value greater than or equal to 1; sim() represents the similarity function; , Respectively represent the main modal energy ratio vector and the main modal weighted energy ratio vector of the t-th calculation time step. Among them, the similarity between the main modal energy ratio vector and the main modal weighted energy ratio vector is cosine similarity. As other implementation methods, on the basis of being able to measure the similarity between the main modal energy ratio vector and the main modal weighted energy ratio vector, the implementer can use other existing technologies for measurement, such as the inverse of the Euclidean distance, etc., and this application does not impose any special restrictions. The schematic diagram of the process of obtaining the absolute error limit is shown in Figure 3 shown.

[0088] In another embodiment, the similarity is mapped to a non-negative value by taking the similarity as the exponent of an exponential function with a natural constant as the base. There are many methods for mapping the similarity to a non-negative value, and the implementer can select other feasible methods at will, and this application does not impose any special restrictions.

[0089] It should be noted that: in the first N calculation time steps for simulating the transformer temperature field, the step size of the calculation time step is not adjusted, the step size of the first N calculation time steps is 0.02s, and the absolute error limit under the N+1th calculation time step is the maximum value of the truncation distances of the first N calculation time steps. Among them, the truncation error of each calculation time step can be calculated from the temperature distribution vector of the adjacent previous calculation time step, and its specific calculation process is well known to those skilled in the art, and this application will not repeat it.

[0090] Furthermore, the step length of the next adjacent calculation step of each calculation step is calculated according to the absolute error limit of the next adjacent calculation step of each calculation step. For each calculation step, the corresponding columns of the selected main mode in the modal matrix form the main mode matrix; the corresponding rows of the selected main mode in the original temperature field distribution coefficient matrix form the main mode distribution coefficient matrix.

[0091] The temperature distribution vector of the adjacent next calculation step is calculated by combining the main mode matrix and the main mode distribution coefficient matrix of each calculation step through the step length of the adjacent next calculation step, and the temperature rise of the hot spot of the transformer winding is obtained according to the size of each element in the temperature distribution vector. Among them, according to the absolute error limit under the adjacent next calculation step of each calculation step, the specific process of calculating the step length of the adjacent next calculation step of each calculation step is well known to those skilled in the art, and this application will not repeat it. The process of calculating the temperature distribution vector of the adjacent next calculation step by combining the main mode matrix and the main mode distribution coefficient matrix of each calculation step through the step length of the adjacent next calculation step of each calculation step is well known to those skilled in the art, and this application will not repeat it.

[0092] Based on the same inventive concept as the above method, an embodiment of the present application also provides a transformer winding hotspot temperature rise calculation system, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of any one of the above-mentioned transformer winding hotspot temperature rise calculation methods are implemented.

[0093] In summary, the present application obtains energy change values ​​by analyzing the changes in modal energy at each calculation time step and multiple adjacent calculation time steps, reflecting the amount of change information of the transformer temperature field contained in each mode and the contribution of each mode to the change information of the transformer temperature field, thereby providing a basis for the extraction of the mode; further, when obtaining the weighted energy ratio of each mode at each calculation time step, a higher weight is given to the mode with a later time, emphasizing the recent modal energy ratio, which can more accurately reflect the dynamic change characteristics of the transformer temperature field; and then the main mode is selected by weighted energy ratio, which improves the reliability of the main mode selection, and can reduce the influence of reduced-order calculation on the obtained winding hot spot temperature rise accuracy while ensuring calculation efficiency;

[0094] Furthermore, by adjusting the calculation step in real time through the selected main mode, the calculation step can be reduced in the stage of rapid temperature change to capture the details of rapid changes and ensure the calculation accuracy of the hot spot temperature rise of the winding. In the stage of slow temperature change, the calculation step can be increased to reduce the amount of calculation and improve the calculation efficiency.

[0095] The flowchart and block diagram in the accompanying drawings show the possible architecture, function and operation of the system, method and computer program product according to the embodiment of the present disclosure. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of the code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. In some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. In the description corresponding to the flowchart and the block diagram in the accompanying drawings, the operations or steps corresponding to different boxes can also occur in a different order from the order disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two consecutive operations or steps can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. Each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by a dedicated hardware-based system that performs the specified functions or actions, or may be implemented by a combination of dedicated hardware and computer instructions.

[0096] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the basic features of the present application. Therefore, no matter from which point of view, the above embodiments of the present application should be regarded as exemplary and non-restrictive.

Claims

1. A method for calculating the hot spot temperature rise of a transformer winding, characterized in that: The method comprises the following steps: Establishing a transformer temperature field model at each calculation time step, wherein the model is an eight-division turn winding model; Through the temperature distribution in the transformer temperature field at each calculation time step, each temperature distribution matrix is ​​constructed, and each mode of each temperature distribution matrix is ​​obtained by dynamic mode decomposition, and the energy ratio of each mode at each calculation time step is calculated; The modes at each calculation time step are numbered in order of arrangement, and the energy change value of each mode at each calculation time step is obtained by analyzing the change of the energy ratio of each mode with the same number at each calculation time step and its preset neighboring calculation time step; the energy ratios of each mode with the same number at each calculation time step and its preset number of adjacent calculation time steps are arranged in time sequence to form a modal energy ratio sequence of each mode at each calculation time step; the weighted energy ratio is calculated, specifically including: calculating the mean of the product of all energy ratios and their weights in each modal energy ratio sequence, wherein the weight of each energy ratio is positively correlated with its order in the modal energy ratio sequence; the weighted energy ratio is obtained by combining the mean of each mode at each calculation time step with the energy change value; the main mode at each calculation time step is extracted through the weighted energy ratio; The energy ratios and weighted energy ratios of all main modes in each calculation time step are arranged in the same order to form the main mode energy ratio vector and the main mode weighted energy ratio vector of each calculation time step respectively; the similarity between the main mode energy ratio vector and the main mode weighted energy ratio vector of each calculation time step is calculated; the initial value of the absolute error limit is preset, and the absolute error limit in the adjacent next calculation time step of each calculation time step is positively correlated with the absolute error limit in each calculation time step and the similarity; according to the absolute error limit in the adjacent next calculation time step, the step length of the adjacent next calculation time step is calculated; and the temperature rise of the hot spot of the transformer winding is obtained.

2. A method for calculating the hot spot temperature rise of a transformer winding according to claim 1, characterized in that: The method for obtaining the temperature distribution matrix is: The temperatures of all nodes in the transformer temperature field at each calculation time step are combined into a temperature distribution vector at each calculation time step; The temperature distribution vector is taken as a column vector, and the temperature distribution vectors at each calculation time step and the temperature distribution vectors at the previous preset number of calculation time steps are combined into a temperature distribution matrix.

3. A method for calculating the hot spot temperature rise of a transformer winding according to claim 1, characterized in that: The process of obtaining the energy change value is as follows: Divide each modal energy ratio sequence into each modal energy ratio subsequence, obtain the discreteness of all data in each modal energy ratio subsequence, and obtain the slope of the fitted straight line of the discreteness of all modal energy ratio subsequences of each modality at each calculation time step; The energy change value of each mode at each calculation time step is determined by the slope of each mode at each calculation time step and the dispersion of the last modal energy ratio subsequence of each mode at each calculation time step.

4. A method for calculating the hot spot temperature rise of a transformer winding according to claim 3, characterized in that: The calculation method of the energy change value is: Mapping the slope of each mode at each calculation time step to a positive number; The energy change value is the product of the dispersion of the last modal energy ratio subsequence of each mode at each calculation time step and the positive number.

5. A method for calculating the hot spot temperature rise of a transformer winding according to claim 1, characterized in that: The weighted energy ratio is the product of the mean value of each mode at each calculation time step and the energy change value.

6. A method for calculating the hot spot temperature rise of a transformer winding according to claim 1, characterized in that: The main mode extraction method is: The sum of the weighted energy ratios of all modes at each calculation time step is recorded as the total weighted energy ratio of each calculation time step; The weighted energy ratios of all modes at each calculation time step are accumulated from large to small. When the accumulated result is greater than the product of the total weighted energy ratio and the preset ratio, the mode involved in the accumulation process is recorded as the main mode at each calculation time step.

7. A method for calculating the hot spot temperature rise of a transformer winding according to claim 1, characterized in that: The method for obtaining the absolute error limit at the adjacent next calculation time step of each calculation time step is: Mapping the similarity into a non-negative value; The product of the absolute error limit at each calculation time step and the non-negative value is used as the absolute error limit at the next adjacent calculation time step of each calculation time step.

8. A transformer winding hot spot temperature rise calculation system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method for calculating the hot spot temperature rise of a transformer winding as described in any one of claims 1 to 7 are implemented.

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