Method for determining insulation resistance of three-winding transformer, measuring device and control equipment

Abstract

The invention provides a method for determining insulation resistance of a three-winding transformer, a measuring device and control equipment, and the method comprises the steps: respectively obtaining a first parallel resistance, a second parallel resistance, a third parallel resistance, a fourth parallel resistance, a fifth parallel resistance and a sixth parallel resistance through controlling and switching six switch combinations; wherein the measured value of each parallel resistor corresponds to the parallel theoretical values of different insulation resistors; and according to the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor and the sixth parallel resistor, the resistance values of the six insulation resistors R10, R20, R30, R12, R13 and R23 are determined. Through the design of the measuring device, six groups of switch combinations can be switched through single wiring, the resistance value of each parallel resistor is measured and solved to obtain the resistance value of each insulation resistor, and the method remarkably shortens the test time, improves the test efficiency, reduces the manual operation risk, and improves the accuracy rate of resistance test.

Description

Technical Field

[0001] This application relates to the field of power transformers, and in particular to a method, measuring device, and control equipment for determining the insulation resistance of a three-winding transformer. Background Technology

[0002] Three-winding transformers, as key voltage conversion devices in power systems, are widely used in multi-level power grids encompassing high-voltage transmission, medium-voltage distribution, and low-voltage consumption. Their core function is to achieve power conversion between high, medium, and low voltage levels through a single device, thereby optimizing the power grid structure and improving operational flexibility. Since the insulation structure of a three-winding transformer consists of multiple layers of insulating oil and paperboard, its insulation performance directly affects the transformer's operational safety and lifespan. Insulation resistance, as one of the core indicators for measuring insulation performance, can sensitively reflect defects such as penetrating damage to the insulation layer, insulating oil deterioration, overall moisture absorption, and surface contamination.

[0003] In actual operation and maintenance, power workers need to periodically measure the insulation resistance of multiple insulation parts of transformers (such as the high-voltage winding to the medium-voltage winding, and the high-voltage winding to ground) using a megohmmeter to assess their insulation condition. However, in existing technologies, each measurement requires separate wiring, discharging, and data reading, resulting in cumbersome and time-consuming operations, and posing a risk of electric shock during frequent wiring. Furthermore, slight deviations in multiple measurement results may mask actual insulation defects, affecting the accuracy of diagnosis.

[0004] Therefore, there is an urgent need for an efficient, safe, and accurate method to measure the insulation resistance of three-winding transformers, in order to meet the power system's requirements for rapid assessment and maintenance of transformer insulation status, and to ensure the stability and safety of power grid operation. Summary of the Invention

[0005] This application provides a method, measuring device, and control equipment for determining the insulation resistance of a three-winding transformer, so as to achieve simple, efficient, and accurate measurement of the insulation resistance of a three-winding transformer.

[0006] In a first aspect, this application provides a method for determining the insulation resistance of a three-winding transformer, applied to a measuring device, the measuring device including a control device, a high-voltage output terminal, a grounding terminal, a high-voltage connection terminal, a medium-voltage connection terminal, and a low-voltage connection terminal;

[0007] The high-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; the medium-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; the low-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; a switch is installed on each connection line, and the switch is connected to the control device.

[0008] The high-voltage terminal is connected to the high-voltage winding, the medium-voltage terminal is connected to the medium-voltage winding, and the low-voltage terminal is connected to the low-voltage winding.

[0009] The method includes:

[0010] Step 1: Control the switch to different preset closed states, and obtain the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor respectively; wherein, the first parallel resistor is the insulation resistance R between the high-voltage winding and the medium-voltage winding. 12 Insulation resistance R between the high-voltage winding and the low-voltage winding 13 Insulation resistance R between the high-voltage winding and ground 10 The first parallel resistor is R; the second parallel resistor is R. 12 Insulation resistance R between the medium-voltage winding and the low-voltage winding 23 Insulation resistance R of medium voltage winding to ground 20 The third parallel resistor is R. 13 R 23 Insulation resistance R between the low-voltage winding and ground 30 The fourth parallel resistor is R. 13 R 10 R 23 R 20 The fifth parallel resistor is R. 10 R 30 R 12 R 23 The sixth parallel resistor is R. 20 R 30 R 12 R 13 Parallel resistors;

[0011] Step 2: Determine R based on the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor. 10 R 20 R 30 R 12 R 13 R 23 The resistance value.

[0012] Furthermore, step 2 includes:

[0013] Based on the measured value and theoretical expression of each parallel resistor, six sets of mathematical equations are established; wherein, the theoretical expression includes the insulation resistance to be solved.

[0014] By subtracting the theoretical values ​​from the measured values, the six sets of mathematical equations are transformed into functions, resulting in six sets of functions.

[0015] The sum of the six sets of functions is used as the objective function. The minimum value of the objective function is then calculated to determine the resistance value of each insulation resistance to be solved.

[0016] Furthermore, the step of finding the minimum value of the objective function and determining the resistance value of each insulation resistance to be solved includes: finding the minimum value of the objective function using a quasi-Newton method and determining the resistance value of each insulation resistance to be solved.

[0017] Furthermore, the minimum value of the objective function is obtained by using the quasi-Newton method to determine the resistance values ​​of each insulation resistance to be solved, including:

[0018] Based on R 13 With R 12 R 13 With R 23 The penalty term of the objective function is constructed by constraining the relationship between the theoretical resistance values;

[0019] The objective function and the penalty term are combined to construct the function to be solved.

[0020] The function to be solved is solved iteratively using the quasi-Newton method until the gradient norm tolerance meets the preset convergence threshold, thereby obtaining the resistance values ​​of each insulation resistance to be solved.

[0021] Furthermore, the function to be solved is:

[0022]

[0023] Where F is the function to be solved, F1 is the objective function, and a1, b1, a2, and b2 are preset penalty factors.

[0024] Furthermore, the method also includes:

[0025] Using extreme value analysis and genetic algorithm, the upper and lower limits of each insulation resistance value are expanded and searched until the six sets of mathematical equations are satisfied, and the range value of each insulation resistance is output.

[0026] Furthermore, the method utilizes extreme value analysis and genetic algorithms to expand the search within the upper and lower limits of each insulation resistance value until the six sets of mathematical equations are satisfied, outputting the interval values ​​of each insulation resistance, including:

[0027] Based on the resistance values ​​of each insulation resistance obtained by the solution, the range of initial insulation resistance values ​​is obtained by setting initialization factors and random initialization variables;

[0028] The fitness function based on extreme value analysis is used to measure whether the variables within the initial insulation resistance value range satisfy the minimum range and equality constraints. By iteratively calculating the fitness function value, the range value of insulation resistance that satisfies the preset fitness threshold is output.

[0029] Secondly, this application provides a control device, the control device comprising:

[0030] The control module is used to control the switch to different preset closed states, and to obtain the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor respectively; wherein, the first parallel resistor is the insulation resistance R between the high-voltage winding and the medium-voltage winding. 12 Insulation resistance R between the high-voltage winding and the low-voltage winding 13 Insulation resistance R between the high-voltage winding and ground 10 The first parallel resistor is R; the second parallel resistor is R. 12 Insulation resistance R between the medium-voltage winding and the low-voltage winding 23 Insulation resistance R of medium voltage winding to ground 20 The third parallel resistor is R. 13 R 23 Insulation resistance R between the low-voltage winding and ground 30 The fourth parallel resistor is R. 13 R 10 R 23 R 20 The fifth parallel resistor is R. 10 R 30 R 12 R 23 The sixth parallel resistor is R. 20 R 30 R 12 R 13 Parallel resistors;

[0031] The determining module is configured to determine R based on the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor. 10 R 20 R 30 R 12 R 13 R 23 The resistance value.

[0032] Thirdly, this application provides a measuring device, which includes a control device, a high-voltage output terminal, a grounding terminal, a high-voltage wiring terminal, a medium-voltage wiring terminal, and a low-voltage wiring terminal;

[0033] The high-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; the medium-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; the low-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; a switch is installed on each connection line, and the switch is connected to the control device.

[0034] The high-voltage terminal is connected to the high-voltage winding, the medium-voltage terminal is connected to the medium-voltage winding, and the low-voltage terminal is connected to the low-voltage winding.

[0035] The control device is used to implement the determination method described in any of the first aspects.

[0036] Fourthly, this application provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the method as described in any of the first aspects.

[0037] Fifthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the first aspect and / or various possible implementations of the first aspect.

[0038] This application provides a method, measuring device, and control equipment for determining the insulation resistance of a three-winding transformer. The method involves controlling and switching six switch combinations after a single wiring step to obtain the first parallel resistance, second parallel resistance, third parallel resistance, fourth parallel resistance, fifth parallel resistance, and sixth parallel resistance, respectively; wherein the first parallel resistance is R. 12 R 13 and R 10 The first parallel resistor is R; the second parallel resistor is R. 12 R 23 and R 20 The first parallel resistor; the third parallel resistor is R. 13 R 23 and R 30 The first parallel resistor; the fourth parallel resistor is R. 13 R 10 R 23 R 20 The fifth parallel resistor is R. 10 R 30 R 12 R 23 The sixth parallel resistor is R. 20 R 30 R 12 R 13 The parallel resistors; based on the first, second, third, fourth, fifth, and sixth parallel resistors, determine R.10 R 20 R 30 R 12 R 13 R 23 The resistance value is determined by reducing the number of manual wiring operations through the design of the measuring device, thereby improving measurement efficiency. Six switch combinations can be switched with a single wiring operation, and the resistance value of each insulation resistance is obtained by measuring the resistance value of each parallel resistor. This method significantly shortens testing time, reduces the risk of manual operation, and improves the accuracy of resistance value testing. Attached Figure Description

[0039] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0040] Figure 1 A structural schematic diagram of the insulation resistance structure model of the three-winding transformer provided in this application;

[0041] Figure 2 A schematic diagram of the measuring device provided in this application.

[0042] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0043] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0044] Three-winding transformers achieve power conversion between high, medium, and low voltage levels using a single device, optimizing system structure and improving operational flexibility. The insulation structure of a three-winding transformer consists of multiple layers of insulating oil and paperboard. Its insulation resistance value is one of the important indicators for measuring insulation performance; a higher resistance value indicates a better insulation layer's ability to prevent leakage current.

[0045] Existing technology for measuring the insulation resistance of three-winding transformers involves applying a DC voltage of the appropriate level to the insulation component of the equipment under test using a megohmmeter. The leakage current flowing through the insulation component is then obtained, and the insulation resistance value can be calculated using Ohm's law. However, three-winding transformers have multiple insulation components, requiring testing of combinations such as "high-voltage winding to medium-voltage winding," "high-voltage winding to low-voltage winding," "medium-voltage winding to low-voltage winding," "high-voltage winding to ground," "medium-voltage winding to ground," and "low-voltage winding to ground." Each measurement requires a long reading time and necessitates rewiring and discharging the equipment. The measurement components are cumbersome, the insulation shielding operation is complex, and each measurement requires full charging and discharging of the equipment. The entire process is time-consuming and inefficient. Furthermore, during frequent rewiring, workers may accidentally touch undischarged components, leading to electric shock accidents.

[0046] In view of this, this application proposes a wiring mode for multi-channel insulation resistance testing by analyzing the insulation structure model (insulation resistance distribution relationship) of a three-winding transformer. Multiple sets of insulation resistance values ​​can be obtained by controlling the closing of different internal switches through a single wiring operation. Based on the obtained multiple sets of insulation resistance values ​​and the insulation resistance distribution relationship, a theoretical expression is constructed, and the resistance values ​​of all insulation resistances are calculated. Through this method, the insulation resistance can be automatically calculated with only one wiring operation, improving testing efficiency and accuracy.

[0047] This application applies to all applications using three-winding transformers, such as substations, distribution networks, and laboratories.

[0048] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0049] Figure 1 The structural schematic diagram of the insulation resistance structure model of the three-winding transformer provided in this application is as follows: Figure 1 As shown, R 12 R is the insulation resistance between the high-voltage winding and the medium-voltage winding. 13 R is the insulation resistance between the high-voltage winding and the low-voltage winding. 23 R is the insulation resistance between the medium-voltage winding and the low-voltage winding. 10 R is the insulation resistance of the high-voltage winding to ground. 20 R is the insulation resistance of the medium-voltage winding to ground. 30 This is the insulation resistance of the low-voltage winding to ground.

[0050] To efficiently complete the multi-point insulation performance evaluation of a three-winding transformer, a multi-channel insulation resistance test wiring mode is adopted. Figure 2 A schematic diagram of the measuring device provided in this application is shown below. Figure 2 As shown, the measuring device includes a control device (not shown), a high-voltage output terminal, a grounding terminal, a high-voltage connection terminal, a medium-voltage connection terminal, and a low-voltage connection terminal;

[0051] The high-voltage terminals are connected to the high-voltage output terminal and the grounding terminal respectively; the medium-voltage terminals are connected to the high-voltage output terminal and the grounding terminal respectively; the low-voltage terminals are connected to the high-voltage output terminal and the grounding terminal respectively; a switch is installed on each connection line, and the switch is connected to the control equipment.

[0052] The high-voltage terminal connects to the high-voltage winding, the medium-voltage terminal connects to the medium-voltage winding, and the low-voltage terminal connects to the low-voltage winding.

[0053] pass Figure 1 The multi-channel insulation resistance test wiring mode allows for the determination of insulation resistance values ​​with a single wiring step. Using the aforementioned measuring device and with the control equipment as the executing entity, the method for determining each insulation resistance includes the following steps:

[0054] Step 1: Control the switch to different preset closed states, and obtain the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor respectively; wherein, the first parallel resistor is R. 12 R 13 and R 10 The first parallel resistor is R; the second parallel resistor is R. 12 R 23 and R 20 The first parallel resistor; the third parallel resistor is R. 13 R 23 and R 30 The first parallel resistor; the fourth parallel resistor is R. 13 R 10 R 23 R 20 The fifth parallel resistor is R. 10 R 30 R 12 R 23 The sixth parallel resistor is R. 20 R 30 R 12 R 13 Parallel resistors.

[0055] The control equipment controls the switch to six different closed states, resulting in different parallel resistances. Figure 2 The connection methods illustrated in the diagram include the following six closed states:

[0056] Combination 1: With K1, K4, and K6 closed and K2, K3, and K5 open, measure the insulation resistance between the high-voltage winding and the medium-voltage winding, the low-voltage winding, and ground, and output the test result A1 of the first parallel resistance. Figure 1 From the structural model, we can obtain:

[0057]

[0058] Combination 2: With K2, K3, and K6 closed and K1, K4, and K5 open, measure the insulation resistance between the medium-voltage winding and the high-voltage winding, the low-voltage winding, and ground, and output the second parallel resistance test result A2. Figure 1 From the structural model, we can obtain:

[0059]

[0060] Combination 3: With K2, K4, and K5 closed and K1, K3, and K6 open, measure the insulation resistance between the low-voltage winding and the high-voltage winding, the medium-voltage winding, and ground, and output the third parallel resistance test result A3. Figure 1 From the structural model, we can obtain:

[0061]

[0062] Combination 4: With K1, K3, and K6 closed and K2, K4, and K5 open, measure the insulation resistance of the high-voltage winding, medium-voltage winding to the low-voltage winding, and ground. Output the fourth parallel resistance test result A4. Figure 1 From the structural model, we can obtain:

[0063]

[0064] Combination 5: With K1, K4, and K5 closed and K2, K3, and K6 open, measure the insulation resistance of the high-voltage winding, low-voltage winding to the medium-voltage winding, and ground. Output the fifth parallel resistance test result A5. Figure 1 From the structural model, we can obtain:

[0065]

[0066] Combination 6: With K2, K3, and K5 closed and K1, K4, and K6 open, measure the insulation resistance of the medium-voltage winding, low-voltage winding to the high-voltage winding, and ground. Output the sixth parallel resistance test result A6. Figure 1 From the structural model, we can obtain:

[0067]

[0068] Step 2: Determine R based on the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor. 10R 20 R 30 R 12 R 13 R 23 The resistance value.

[0069] The above six measured values ​​and six unknowns can be solved by solving the system of equations to obtain R. 10 R 20 R 30 R 12 R 13 R 23 The resistance value. There are various ways to solve this group of methods, such as the quasi-Newton method, the secant method, and the fixed-point iteration method.

[0070] Using the method described in this application, it is only necessary to connect the high-voltage winding, medium-voltage winding, and low-voltage winding to their corresponding terminals. After one wiring, the rated voltage is applied to the high-voltage output terminal, and a control signal is output to cause the corresponding switch to be closed or open, thus allowing the R value to be measured. 10 R 20 R 30 R 12 R 13 R 23 The resistance value.

[0071] When measuring the insulation resistance of transformer windings, the positions of the voltage application clamp and signal acquisition clamp on the test object cannot be guaranteed to be completely consistent, and there is electromagnetic interference coupled from nearby live equipment, resulting in slight deviations in the test results for the same insulation part in multiple tests. That is, each insulation resistance measured is slightly different and not a fixed value. Specifically, the same variable in equations (1)-(6) may have different values ​​in different equations, with slight differences. Therefore, in order to accurately represent the insulation resistance value, it can be expressed in the form of a resistance value range. The following uses a combination of the quasi-Newton method and a genetic algorithm to obtain the resistance value range of each insulation resistance.

[0072] Therefore, in a given R 10 R 20 R 30 R 12 R 13 R 23 In this method of resistance estimation, a preliminary estimation of the resistance value of each insulation component is first performed using a coarse-grained positioning method. Specifically, this includes the following steps:

[0073] S21. Based on the measured value and theoretical expression of each parallel resistor, establish six sets of mathematical equations; among them, the theoretical expression includes the insulation resistance to be solved.

[0074] The measured value of each parallel resistor is A in the above formulas (1)-(6), and the theoretical expression is the left side of the equal sign in the above formulas (1)-(6). The theoretical part of the parallel resistance is calculated based on the resistance value of the insulation resistance to be solved.

[0075] S22. By subtracting the theoretical values ​​from the measured values, the six sets of mathematical equations are transformed into functions, resulting in six sets of functions.

[0076] Equations (1)-(6) are converted into the following six sets of functions:

[0077]

[0078] S23. Take the sum of the six sets of functions as the objective function, solve for the minimum value of the objective function, and determine the resistance value of each insulation resistance to be solved.

[0079] Establish the objective function as minimizing the sum of all functions, as shown in equation (7):

[0080]

[0081] By finding the minimum value of the objective function described above, R can be determined. 10 R 20 R 30 R 12 R 13 R 23 The resistance value.

[0082] In one specific implementation, the resistance is solved by minimizing the objective function using a quasi-Newton method. The quasi-Newton method is an unconstrained optimization algorithm that accelerates convergence by approximating the Hessian matrix and is suitable for solving nonlinear equations.

[0083] Specifically, considering the structural characteristics of a three-winding transformer, this invention is designed based on a typical winding arrangement, where the high-voltage winding is located on the outermost side, the medium-voltage winding is in the middle, and the low-voltage winding is located on the innermost side. Therefore, the insulation resistance value R between the high-voltage winding and the low-voltage winding is... 13 Greater than the insulation resistance R between the high-voltage winding and the medium-voltage winding 12 The insulation resistance R between the medium-voltage winding and the low-voltage winding 23 As shown in equation (8).

[0084]

[0085] The constraint-based optimization problem is transformed into an unconstrained optimization problem by using the penalty function method in exponential form. That is, the optimization models (7) and (8) are transformed into equation (9), as shown in the following equation, where a1, b1, a2, and b2 are penalty factors.

[0086]

[0087] The function in equation (9) is the function to be solved. The last two terms are penalty terms. Equation (9) is optimized using the quasi-Newton method to minimize its function value. The steps are as follows.

[0088] First, initialize the variables. We take the identity matrix as a positive definite approximation matrix H0 and set the gradient norm tolerance. This is the convergence threshold.

[0089] Calculate the gradient of the objective function, i.e.

[0090]

[0091] In the formula, k represents the number of iterations. After each gradient calculation, the gradient norm tolerance is checked to see if it meets the convergence threshold. If it does, the iteration stops, and x is output. k This allows for coarse-grained positioning of the resistance values ​​at each insulation component. Otherwise, continued optimization and iteration are performed.

[0092] During the update and iteration process, it is necessary to determine the search direction p. k The calculation is shown in Equation (11), and the Armijo criterion is used to determine the line search step size. Update.

[0093]

[0094] H k Let be the positive definite approximation matrix after iteration. Update the iteration points and the approximation matrix. The iterative calculation process is shown in equations (12) and (13).

[0095]

[0096]

[0097] I is the identity matrix; S k The step size vector represents the change during iteration; y K This is the gradient change vector.

[0098] The insulation resistance values ​​x for six combinations of the three-winding transformer were obtained through optimization using the quasi-Newton method. k Because of x k Substituting the values ​​of the six resistors into equations (1)-(6) may not necessarily make the equations true. Therefore, the six resistor values ​​obtained by the quasi-Newton method optimization can be substituted into equations (1)-(6) for verification. If the equations are true, the resistance values ​​of each insulation resistor obtained by coarse-grained positioning can be output.

[0099] Based on the resistance values ​​of each insulation resistance obtained by the above coarse-grained positioning, extreme value analysis and genetic algorithm are used to expand the search within the upper and lower limits of each insulation resistance value until equations (1)-(6) are satisfied, and the range values ​​of each insulation resistance are obtained.

[0100] To overcome the problems of wasted computational resources and low solution accuracy caused by the excessively large search range of a single genetic algorithm, the search method in this application combines extreme value analysis and genetic algorithm.

[0101] Based on the resistance values ​​obtained from the coarse-grained positioning using the quasi-Newton method, we expand to their upper and lower limits to find values ​​within the upper and lower limit ranges that simultaneously satisfy equations (1)-(6). Let each resistance value have upper and lower limit characteristics, denoted as a. i b i (i is a positive integer and i ∈ [1, 6], a) i i ), i represents x k The i-th element.

[0102] Given the slight deviation characteristic of insulation resistance measurements, the combination of intervals with the minimum uncertainty is selected from all constrained intervals to avoid meaningless expansion of the intervals, making the obtained intervals more accurate and better assessing the condition of critical insulation components of the transformer. Therefore, a function is established with minimizing the total width of the intervals as the objective function, as shown in the following equation.

[0103]

[0104] At the same time, the following constraints need to be met:

[0105]

[0106] In the formula, j represents the j-th equation in equations (1)-(6). S represents the elements in the coefficient matrix T of the six sets of functions. j Let x be the value on the right side of the j-th equation in the group of six methods. i,j Substituting it into the equation gives the value on the right.

[0107] The following is a genetic algorithm design based on the optimization of insulation resistance value range:

[0108] (1) Initialize the insulation resistance value range:

[0109] With x k Based on the insulation resistance values ​​of each part, an initialization factor λ is set, and variable a is randomly initialized. i b i a i b i The calculation is shown in equation (16), and it must satisfy a. i <b​i And form chromosomes [a1, b1, a2, b2, ..., a6, b6].

[0110]

[0111] rand represents a random number in (0,1).

[0112] (2) Fitness function calculation based on extreme value analysis:

[0113] By establishing a fitness function based on extreme value analysis, we can measure whether the interval variable can satisfy the minimization of the interval and meet the constraints in equation (15). The fitness function value is shown in the following equation.

[0114]

[0115] In the formula, To determine whether the values ​​in a specified interval satisfy constraint (13) through extreme value analysis, For numbers much greater than 0 (e.g., 10000), if the constraint is satisfied, assign...

[0116] The value is 0, otherwise, the value is assigned as 0. . , where is the weighting coefficient, balancing the error and the interval width.

[0117] (3) Selection, crossover, and mutation:

[0118] Selection: Using the tournament selection algorithm, the fitness function value of each chromosome is calculated in each iteration. Individuals with high fitness are preferentially retained, that is, those that meet the constraints in equation (15) with small total width of the interval of each insulation resistance part, and are allowed to enter the next stage.

[0119] Crossover: For the selected individuals, a certain probability is used to determine whether to perform a crossover operation. If the decision is successful, an interval is randomly selected from the six interval variables of the individual, and the selected interval parameter structure of the parent and mother generations is swapped to form two new individuals; if the decision is unsuccessful, no crossover operation is performed, and the process proceeds directly to the next stage.

[0120] Mutation: For the individuals retained after crossover, a mutation operation is performed on the individuals in the population with a certain probability. A certain interval is randomly selected from the mutated individuals, and the boundary of the interval is randomly expanded or contracted to realize the local perturbation of the interval, so as to ensure that the interval optimization process does not get trapped in the local optimum, as shown in Equation (18).

[0121]

[0122] In the formula, , All are random numbers; if mutated... Swap the values ​​of the two to form a new interval.

[0123] (4) Population update and judgment: After selection, crossover, and mutation, the remaining individuals are updated. A maximum number of iterations and a fitness threshold are set. If either condition is met, the optimization iteration stops and the best individual is output; otherwise, optimization continues.

[0124] In summary, to address the minute deviation characteristics in repeated insulation resistance measurements, an interval-based insulation resistance calculation algorithm is proposed. Based on the aforementioned genetic algorithm, accurate interval positioning of each insulation resistance value can be achieved. Algorithm optimization can eliminate measurement errors and improve accuracy. A quasi-Newton method is used to solve multiple combination equations for coarse-grained insulation resistance positioning. Then, minimizing the total interval width is used as the objective function, considering the constraint of the sum of combined insulation resistances, to achieve precise interval positioning. The two-stage optimization combining the quasi-Newton method and the genetic algorithm improves the accuracy and speed of the solution at the algorithmic level. This method can simultaneously evaluate the condition of all critical insulation components of a transformer with a single connection, significantly improving testing efficiency and accuracy, and providing reliable data support for transformer insulation condition diagnosis.

[0125] The following is a summary of the methods for calculating various insulation resistances using genetic algorithms, including the following steps:

[0126] Step 1: Based on the structural and functional characteristics of the three-winding transformer, model the insulation structure of the three-winding transformer.

[0127] Step 2: Based on the designed multi-channel insulation resistance test wiring mode, simultaneously measure the insulation resistance values ​​of multiple insulation combination parts of the three-winding transformer, analyze the basic composition of each insulation combination part, and express it in equation form.

[0128] Step 3: Convert the measured insulation resistance combination equation into a function form, establish the objective function of minimizing the sum of all functions, and use the quasi-Newton method to solve the problem, considering the special characteristics of the insulation resistance between the high voltage winding and the low voltage winding and the insulation resistance between the medium voltage winding and ground, to obtain the coarse-grained positioning of the resistance value of each insulation part, that is, the estimated insulation resistance value of each insulation part.

[0129] Step 4: Based on the insulation resistance values ​​of each insulation part output in Step 3, use a genetic algorithm to optimize and expand the search of each insulation resistance value to its upper and lower limits until all equality conditions are met and the sum of the intervals is minimized. Finally, output the insulation resistance interval values ​​of each insulation part.

[0130] This application also provides a control device, which includes:

[0131] The control module is used to control the switch to different preset closed states, and to obtain the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor respectively; wherein, the first parallel resistor is the insulation resistance R between the high-voltage winding and the medium-voltage winding. 12 Insulation resistance R between the high-voltage winding and the low-voltage winding 13 Insulation resistance R between the high-voltage winding and ground 10 The first parallel resistor is R; the second parallel resistor is R. 12 Insulation resistance R between the medium-voltage winding and the low-voltage winding 23 Insulation resistance R of medium voltage winding to ground 20 The first parallel resistor; the third parallel resistor is R. 13 R 23 Insulation resistance R between the low-voltage winding and ground 30 The first parallel resistor; the fourth parallel resistor is R. 13 R 10 R 23 R 20 The fifth parallel resistor is R. 10 R 30 R 12 R 23 The sixth parallel resistor is R. 20 R 30 R 12 R 13 Parallel resistors;

[0132] The determining module is used to determine R based on the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor. 10 R 20 R 30 R 12 R 13 R 23 The resistance value.

[0133] Furthermore, the module is defined to include a theory establishment unit, a function establishment unit, and a function solution unit;

[0134] The theoretical establishment unit is used to establish six sets of mathematical equations based on the measured value and theoretical expression of each parallel resistor; among them, the theoretical expression includes the insulation resistance to be solved.

[0135] The function establishment unit is used to transform six sets of mathematical equations into functions by subtracting theoretical values ​​from measured values, thus obtaining six sets of functions.

[0136] The function solving unit is used to sum the six sets of functions as the objective function, solve for the minimum value of the objective function, and determine the resistance value of each insulation resistance to be solved.

[0137] Furthermore, the function solving unit is used to find the minimum value of the objective function using the quasi-Newton method, and to determine the resistance value of each insulation resistance to be solved.

[0138] Furthermore, the function solving unit is specifically used for:

[0139] Based on R 13 With R 12 R 13 With R 23 Constraints on the theoretical resistance values ​​are used to construct a penalty term for the objective function;

[0140] By combining the objective function and the penalty term, we obtain the function to be solved.

[0141] The function to be solved is solved iteratively using the quasi-Newton method until the gradient norm tolerance meets the preset convergence threshold, thus obtaining the resistance values ​​of each insulation resistance to be solved.

[0142] Furthermore, the function solving unit is also used for:

[0143] Using extreme value analysis and genetic algorithm, the search is expanded within the upper and lower limits of each insulation resistance value until six sets of mathematical equations are satisfied, and the range value of each insulation resistance is output.

[0144] The control device provided in this embodiment can execute the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0145] The control device can be a controller, computer, or similar device with processing capabilities, and includes at least one processor and memory. Optionally, the controller device also includes a communication component. The processor, memory, and communication component are connected via a bus.

[0146] In a specific implementation, at least one processor executes computer execution instructions stored in memory, causing at least one processor to perform the above-described method.

[0147] The specific implementation process of the processor can be found in the above method embodiments, and its implementation principle and technical effect are similar, so it will not be repeated here.

[0148] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0149] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0150] The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0151] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0152] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0153] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0154] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0155] The division of units is merely a logical functional division; 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 coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0156] 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 network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0157] In addition, the functional units in the various embodiments of the present invention 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.

[0158] If a function 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 invention, or the part that contributes to the prior art, or a 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 invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0159] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0160] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for determining the insulation resistance of a three-winding transformer, characterized in that, It is applied to a measuring device, which includes a control device, a high-voltage output terminal, a grounding terminal, a high-voltage wiring terminal, a medium-voltage wiring terminal, and a low-voltage wiring terminal; The high-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; the medium-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; the low-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; a switch is installed on each connection line, and the switch is connected to the control device. The high-voltage terminal is connected to the high-voltage winding, the medium-voltage terminal is connected to the medium-voltage winding, and the low-voltage terminal is connected to the low-voltage winding. The method includes: Step 1: Control the switch to different preset closed states, and obtain the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor respectively; wherein, the first parallel resistor is the insulation resistance R between the high-voltage winding and the medium-voltage winding. 12 Insulation resistance R between the high-voltage winding and the low-voltage winding 13 Insulation resistance R between the high-voltage winding and ground 10 The first parallel resistor is R; the second parallel resistor is R. 12 Insulation resistance R between the medium-voltage winding and the low-voltage winding 23 Insulation resistance R of medium voltage winding to ground 20 The third parallel resistor is R. 13 R 23 Insulation resistance R between the low-voltage winding and ground 30 The fourth parallel resistor is R. 13 R 10 R 23 R 20 The fifth parallel resistor is R. 10 R 30 R 12 R 23 The sixth parallel resistor is R. 20 R 30 R 12 R 13 Parallel resistors; Step 2: Determine R based on the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor. 10 R 20 R 30 R 12 R 13 R 23 The resistance value.

2. The method according to claim 1, characterized in that, Step 2 includes: Based on the measured value and theoretical expression of each parallel resistor, six sets of mathematical equations are established; wherein, the theoretical expression includes the insulation resistance to be solved. By subtracting the theoretical values ​​from the measured values, the six sets of mathematical equations are transformed into functions, resulting in six sets of functions. The sum of the six sets of functions is used as the objective function. The minimum value of the objective function is then calculated to determine the resistance value of each insulation resistance to be solved.

3. The method according to claim 2, characterized in that, The process of finding the minimum value of the objective function and determining the resistance value of each insulation resistance to be solved includes: finding the minimum value of the objective function using the quasi-Newton method and determining the resistance value of each insulation resistance to be solved.

4. The method according to claim 3, characterized in that, The minimum value of the objective function is obtained by using the quasi-Newton method to determine the resistance values ​​of each insulation resistance to be solved, including: Based on R 13 With R 12 R 13 With R 23 The penalty term of the objective function is constructed by constraining the relationship between the theoretical resistance values; The objective function and the penalty term are combined to construct the function to be solved. The function to be solved is solved iteratively using the quasi-Newton method until the gradient norm tolerance meets the preset convergence threshold, thereby obtaining the resistance values ​​of each insulation resistance to be solved.

5. The method according to claim 4, characterized in that, The function to be solved is: Where F is the function to be solved, F1 is the objective function, and a1, b1, a2, and b2 are preset penalty factors.

6. The method according to claim 4 or 5, characterized in that, The method further includes: Using extreme value analysis and genetic algorithm, the upper and lower limits of each insulation resistance value are expanded and searched until the six sets of mathematical equations are satisfied, and the range value of each insulation resistance is output.

7. The method according to claim 6, characterized in that, The method utilizes extreme value analysis and genetic algorithms to expand the search within the upper and lower limits of each insulation resistance value until the six sets of mathematical equations are satisfied, outputting the interval values ​​of each insulation resistance, including: Based on the resistance values ​​of each insulation resistance obtained by the solution, the range of initial insulation resistance values ​​is obtained by setting initialization factors and random initialization variables; The fitness function based on extreme value analysis is used to measure whether the variables within the initial insulation resistance value range satisfy the minimum range and equality constraints. By iteratively calculating the fitness function value, the range value of insulation resistance that satisfies the preset fitness threshold is output.

8. A control device, characterized in that, The control device includes: The control module is used to control the switch to different preset closed states, and to obtain the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor respectively; wherein, the first parallel resistor is the insulation resistance R between the high-voltage winding and the medium-voltage winding. 12 Insulation resistance R between the high-voltage winding and the low-voltage winding 13 Insulation resistance R between the high-voltage winding and ground 10 The first parallel resistor is R; the second parallel resistor is R. 12 Insulation resistance R between the medium-voltage winding and the low-voltage winding 23 Insulation resistance R of medium voltage winding to ground 20 The third parallel resistor is R. 13 R 23 Insulation resistance R between the low-voltage winding and ground 30 The fourth parallel resistor is R. 13 R 10 R 23 R 20 The fifth parallel resistor is R. 10 R 30 R 12 R 23 The sixth parallel resistor is R. 20 R 30 R 12 R 13 Parallel resistors; The determining module is configured to determine R based on the first parallel resistor, the second parallel resistor, the third parallel resistor, the fourth parallel resistor, the fifth parallel resistor, and the sixth parallel resistor. 10 R 20 R 30 R 12 R 13 R 23 The resistance value.

9. A measuring device, characterized in that, The measuring device includes a control device, a high-voltage output terminal, a grounding terminal, a high-voltage connection terminal, a medium-voltage connection terminal, and a low-voltage connection terminal; The high-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; the medium-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; the low-voltage terminal is connected to the high-voltage output terminal and the grounding terminal respectively; a switch is installed on each connection line, and the switch is connected to the control device. The high-voltage terminal is connected to the high-voltage winding, the medium-voltage terminal is connected to the medium-voltage winding, and the low-voltage terminal is connected to the low-voltage winding. The control device is used to implement the determination method according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the method as described in any one of claims 1-7.

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