A method and system for monitoring the error of a current transformer

Abstract

The present invention discloses a method and system for monitoring the error of a current transformer, including: obtaining the total loop impedance of the current transformer measured by a heterodyne test signal; obtaining the equivalent loop impedance of the current transformer according to the equivalent circuit of the current transformer; constructing an optimization objective function with the goal of minimizing the difference between the total loop impedance and the equivalent loop impedance, and solving the optimization objective function to obtain the equivalent circuit parameters of the current transformer; obtaining the operating error of the current transformer according to the equivalent circuit parameters of the current transformer. By calculating the operating error of the current transformer based on the total loop impedance and the equivalent loop impedance of the current transformer, the problem of the theoretical uncertainty in determining the accuracy of the transformer through some measurement parameters on the secondary side is solved, thereby improving the accuracy of measuring the error of the transformer.

Description

Technical Field

[0001] The present invention relates to the technical field of current transformer metering, and particularly to a method and system for monitoring the error of a current transformer. Background Art

[0002] The statements in this part merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] The on-line monitoring technology of current transformers can avoid the economic losses caused by power outages, manpower requirements, etc. brought by off-line detection; at the same time, it can also realize the detection of current transformers under the actual on-site operating environment, which is more real than off-line detection, can better reflect the true accuracy of the current transformer, and the detection results are more reasonable.

[0004] However, there is no effective theoretical algorithm for on-line monitoring of current transformers. The on-line monitoring of current transformers can only be achieved through some measurements on the secondary side. There are theoretical uncertainty problems in judging the accuracy of current transformers only through some measurement parameters on the secondary side. Summary of the Invention

[0005] To solve the above problems, the present invention proposes a method and system for monitoring the error of a current transformer, which calculates the running error of the current transformer according to the total loop impedance and equivalent loop impedance of the current transformer, solves the theoretical uncertainty problems in judging the accuracy of the current transformer through some measurement parameters on the secondary side, and thus improves the accuracy of measuring the error of the current transformer.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for monitoring the error of a current transformer, including:

[0008] Obtaining the total loop impedance of the current transformer measured by a heterodyne test signal;

[0009] Obtaining the equivalent loop impedance of the current transformer according to the equivalent circuit of the current transformer;

[0010] Constructing an optimization objective function with the minimum difference between the total loop impedance and the equivalent loop impedance as the target, and solving the optimization objective function to obtain the equivalent circuit parameters of the current transformer;

[0011] Obtaining the running error of the current transformer according to the equivalent circuit parameters of the current transformer.

[0012] As an alternative embodiment, the equivalent circuit parameters of the current transformer include an equivalent excitation inductance, an equivalent excitation resistance, an equivalent excitation distributed capacitance, an equivalent secondary loop inductance, an equivalent secondary loop resistance, and an equivalent secondary loop distributed capacitance.

[0013] As an alternative embodiment, the equivalent circuit impedance Z of the current transformer 总 is:

[0014]

[0015] wherein, L m is the equivalent excitation inductance, R m is the equivalent excitation resistance, C1 is the equivalent distributed excitation capacitance, L2 is the equivalent secondary circuit inductance, R2 is the equivalent secondary circuit resistance, C2 is the equivalent distributed secondary circuit capacitance, and w is the frequency.

[0016] As an alternative embodiment, the operating error ε of the current transformer is:

[0017]

[0018]

[0019] Z2 = Z 总 -Z m

[0020] wherein, Z2 is the secondary circuit impedance of the current transformer, and Z , is the value of the magnetizing impedance converted to the secondary side.

[0021] As an alternative embodiment, the optimization objective function f is:

[0022]

[0023] wherein, α i is the weight coefficient; n is the number of different frequency data selected.

[0024] As an alternative embodiment, a genetic algorithm is used to solve the optimization objective function.

[0025] As an alternative embodiment, the frequency of the heterodyne test signal is selected to be 1000 Hz - 10000 Hz.

[0026] In a second aspect, the present invention provides a current transformer error monitoring system, including:

[0027] A measurement module configured to obtain the total loop impedance of the current transformer measured by the heterodyne test signal;

[0028] An equivalent module configured to obtain the equivalent loop impedance of the current transformer according to the equivalent circuit of the current transformer;

[0029] The target solving module is configured to construct an optimization objective function with the minimum difference between the total loop impedance and the equivalent loop impedance as the target, and solve the optimization objective function to obtain the equivalent circuit parameters of the current transformer;

[0030] The error solving module is configured to obtain the operating error of the current transformer according to the equivalent circuit parameters of the current transformer.

[0031] As an alternative implementation, the equivalent circuit parameters of the current transformer include an equivalent excitation inductance, an equivalent excitation resistance, an equivalent excitation distributed capacitance, an equivalent secondary loop inductance, an equivalent secondary loop resistance, and an equivalent secondary loop distributed capacitance.

[0032] As an alternative implementation, the equivalent loop impedance Z 总 of the current transformer is:

[0033]

[0034] where L m is the equivalent excitation inductance, R m is the equivalent excitation resistance, C1 is the equivalent excitation distributed capacitance, L2 is the equivalent secondary loop inductance, R2 is the equivalent secondary loop resistance, C2 is the equivalent secondary loop distributed capacitance, and w is the frequency.

[0035] As an alternative implementation, the operating error ε of the current transformer is:

[0036]

[0037]

[0038] Z2 = Z 总 - Z m

[0039] where Z2 is the secondary loop impedance of the current transformer, and Z m is the value of the excitation impedance converted to the secondary side.

[0040] As an alternative implementation, the optimization objective function f is:

[0041]

[0042] where α i is the weight coefficient; n is the number of data at different selected frequencies.

[0043] As an alternative implementation, a genetic algorithm is used to solve the optimization objective function.

[0044] As an alternative implementation, the frequency of the heterodyne test signal is selected to be 1000 Hz - 10000 Hz.

[0045] In a third aspect, the present invention provides an electronic device, including a memory, a processor, and computer instructions stored on the memory and running on the processor. When the computer instructions are run by the processor, the method described in the first aspect is completed.

[0046] In a fourth aspect, the present invention provides a computer-readable storage medium for storing computer instructions. When the computer instructions are executed by a processor, the method described in the first aspect is completed.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0048] The present invention proposes a method and system for monitoring the error of a current transformer. The running error of the current transformer is calculated according to the total impedance of the circuit of the current transformer and the equivalent circuit impedance, solving the problem of the theoretical uncertainty in judging the accuracy of the transformer through some measurement parameters on the secondary side, thereby improving the accuracy of measuring the error of the transformer. At the same time, the calculation amount is small, the accuracy is high, and the real-time monitoring of the running error of the current transformer can be realized without complex structural equipment.

[0049] The advantages of the additional aspects of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0051] Figure 1 It is a flowchart of the method for monitoring the error of a current transformer provided in Embodiment 1 of the present invention;

[0052] Figure 2 It is an equivalent circuit of a current transformer provided in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0053] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0054] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0055] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0056] In the case of no conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0057] As shown in the background art, the on-line monitoring technology of current transformers can avoid the economic losses caused by power outages, manpower requirements, etc. brought by off-line detection; at the same time, it can also realize the detection of current transformers under the actual on-site operating environment, which is more real than off-line detection, can better reflect the true accuracy of current transformers, and the detection results are more reasonable.

[0058] However, there is no effective theoretical algorithm for on-line monitoring of current transformers. The on-line monitoring of current transformers can only be realized by some measurements on the secondary side. There are uncertain problems in theory for judging the accuracy of current transformers only through some measurement parameters on the secondary side.

[0059] Based on the above findings, the present application provides a method and system for monitoring the error of a current transformer, which calculates the operating error of the current transformer according to the total impedance of the current transformer circuit and the equivalent circuit impedance, solves the uncertain problems in theory for judging the accuracy of the current transformer through some measurement parameters on the secondary side, thereby improving the accuracy of measuring the error of the current transformer. At the same time, the calculation amount is small, the accuracy is high, and the real-time monitoring of the operating error of the current transformer can be realized without complex structural equipment.

[0060] The following elaborates on this in detail.

[0061] Embodiment 1

[0062] This embodiment provides a method for monitoring the error of a current transformer, including:

[0063] Obtain the total impedance of the current transformer circuit measured by the heterodyne test signal;

[0064] Obtain the equivalent circuit impedance of the current transformer according to the equivalent circuit of the current transformer;

[0065] An optimization objective function is constructed with the goal of minimizing the difference between the total loop impedance and the equivalent loop impedance, and the equivalent circuit parameters of the current transformer are obtained by solving the optimization objective function.

[0066] The operating error of the current transformer is obtained based on the equivalent circuit parameters of the current transformer.

[0067] Specifically, as Figure 1 shown;

[0068] In this embodiment, according to the heterodyne injection method, after injecting a heterodyne test signal into the current transformer, the total loop impedance Z of the current transformer is measured.

[0069] Since the frequency of the heterodyne test signal is much higher than that of the power frequency signal, the heterodyne test signal will not affect the normal operating state of the current transformer.

[0070] As an alternative embodiment, the frequency of the heterodyne test signal is selected to be 1000 Hz - 10000 Hz.

[0071] In this embodiment, according to the equivalent circuit of the current transformer as Figure 2 shown, the equivalent loop impedance Z of the current transformer is determined. 总 ; Z 总 is expressed as:

[0072]

[0073] where L m is the equivalent exciting inductance, R m is the equivalent exciting resistance, C1 is the equivalent exciting distributed capacitance, L2 is the equivalent secondary loop inductance, R2 is the equivalent secondary loop resistance, C2 is the equivalent secondary loop distributed capacitance, and w is the frequency.

[0074] In this embodiment, an optimization objective function is constructed with the goal of minimizing the difference between the total loop impedance Z and the equivalent loop impedance Z 总 ; the optimization objective function f is:

[0075]

[0076] where α i is the weight coefficient, which is used to represent the accuracy of the measurement result. If the measurement result is considered to be completely accurate, then α i takes 1; n is the number of data with different frequencies selected.

[0077] Then, the optimization objective function is solved by the genetic algorithm to determine the equivalent exciting inductance L m and the equivalent exciting resistance R m, equivalent excitation distributed capacitance C1, equivalent secondary circuit inductance L2, equivalent secondary circuit resistance R2 and equivalent secondary circuit distributed capacitance C2.

[0078] The genetic algorithm is used to solve the parameters of each equivalent circuit. In essence, it transforms the problem of solving the optimization objective function into finding parameters that make ZZ 总 The problem of minimizing the value of is solved by using the “root trial” method to find the optimal solution. The specific steps include:

[0079] Initialization: Set the decision variables of the genetic algorithm (the decision variables are L m , R m , C1, L2, R2 and C2) range, population size and maximum number of iterations, determine the optimization objective function and fitness function (the fitness function is the inverse of the objective function);

[0080] Initialize the population: Randomly select L within the set range m , R m , C1, L2, R2 and C2, and calculate the value of the objective function to form the initial population;

[0081] Inheritance, crossover, and mutation: Perform inheritance, crossover, and mutation operations on the previous generation population to form a descendant population;

[0082] Survival of the fittest: After merging the parent generation and the offspring, a new batch of offspring with a larger fitness function is selected (the number of new offspring is equal to the initial set population size).

[0083] The above steps of inheritance, crossover, mutation and natural selection are repeated. When the objective function value of an individual in the population is less than a preset threshold, the calculation is stopped; the genotype of the individual (the values of all decision variables) is the equivalent circuit parameter required.

[0084] In this embodiment, the operating error ε of the current transformer is determined according to the obtained current transformer equivalent circuit parameters; the operating error ε of the current transformer is expressed as:

[0085]

[0086]

[0087] Z2=Z 总 -Z m

[0088] Among them, Z2 is the secondary circuit impedance of the current transformer, Z m It is the value of the excitation impedance converted to the secondary side.

[0089] Example 2

[0090] This embodiment provides a current transformer error monitoring system, including:

[0091] A measurement module configured to obtain the total loop impedance of the current transformer measured by a heterodyne test signal;

[0092] An equivalent module configured to obtain the equivalent loop impedance of the current transformer according to the equivalent circuit of the current transformer;

[0093] A target solving module configured to construct an optimization objective function with the minimum difference between the total loop impedance and the equivalent loop impedance as the target, and solve the optimization objective function to obtain the equivalent circuit parameters of the current transformer;

[0094] An error solving module configured to obtain the operating error of the current transformer according to the equivalent circuit parameters of the current transformer.

[0095] Furthermore, the equivalent circuit parameters of the current transformer include equivalent excitation inductance, equivalent excitation resistance, equivalent excitation distributed capacitance, equivalent secondary loop inductance, equivalent secondary loop resistance, and equivalent secondary loop distributed capacitance.

[0096] The equivalent loop impedance Z of the current transformer 总 is:

[0097]

[0098] where L m is the equivalent excitation inductance, R m is the equivalent excitation resistance, C1 is the equivalent excitation distributed capacitance, L2 is the equivalent secondary loop inductance, R2 is the equivalent secondary loop resistance, C2 is the equivalent secondary loop distributed capacitance, and w is the frequency.

[0099] The operating error ε of the current transformer is:

[0100]

[0101]

[0102] Z2 = Z 总 - Z m

[0103] where Z2 is the secondary loop impedance of the current transformer, and Z m is the value of the excitation impedance converted to the secondary side.

[0104] The optimization objective function f is:

[0105]

[0106] where α i is the weight coefficient; n is the number of data with different frequencies selected.

[0107] The genetic algorithm is used to solve the optimization objective function, and the frequency of the off-frequency test signal is selected as

[0108] 1000 Hz - 10000 Hz.

[0109] It should be noted here that the above modules correspond to the steps described in Embodiment 1. The examples and application scenarios implemented by the above modules and the corresponding steps are the same, but are not limited to the content disclosed in the above Embodiment 1. It should be noted that the above modules, as a part of the system, can be executed in a computer system such as a set of computer-executable instructions.

[0110] In more embodiments, there is also provided:

[0111] An electronic device includes a memory, a processor, and computer instructions stored on the memory and running on the processor. When the computer instructions are run by the processor, the method described in Embodiment 1 is completed. For the sake of brevity, it will not be elaborated here.

[0112] It should be understood that in this embodiment, the processor may be a central processing unit CPU, and the processor may also be other general-purpose processors, digital signal processors DSP, application-specific integrated circuits ASIC, off-the-shelf programmable gate arrays FPGA, or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0113] The memory may include a read-only memory and a random access memory, and provide instructions and data to the processor. A part of the memory may also include a non-volatile random access memory. For example, the memory may also store information about the device type.

[0114] A computer-readable storage medium is used to store computer instructions. When the computer instructions are executed by the processor, the method described in Embodiment 1 is completed.

[0115] The method in Embodiment 1 can be directly embodied as being executed by a hardware processor, or by a combination of hardware and software modules in the processor. The software modules may be located in mature storage media in the art such as random access memory, flash memory, read-only memory, programmable read-only memory, or electrically erasable programmable memory, registers, etc. This storage medium is located in the memory, and the processor reads the information in the memory and combines its hardware to complete the steps of the above method. To avoid repetition, it will not be described in detail here.

[0116] Those of ordinary skill in the art can realize that the units and algorithm steps of the examples described in conjunction with this embodiment can be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0117] Although the specific implementation manners of the present invention have been described above in conjunction with the accompanying drawings, they are not limitations on the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A method for monitoring the error of a current transformer, characterized in that, Including: Obtain the total impedance of the current transformer loop measured by the off-frequency test signal; Obtain the equivalent loop impedance of the current transformer according to the equivalent circuit of the current transformer; Construct an optimization objective function with the goal of minimizing the difference between the total loop impedance and the equivalent loop impedance, and solve the optimization objective function to obtain the equivalent circuit parameters of the current transformer; Obtain the operating error of the current transformer according to the equivalent circuit parameters of the current transformer; Equivalent circuit impedance of current transformer is as follows: Among them, is the equivalent excitation inductance, is the equivalent excitation resistance, is the equivalent excitation distributed capacitance, is the equivalent secondary circuit inductance, is the equivalent secondary circuit resistance, is the equivalent secondary circuit distributed capacitance, is the frequency; Operation error of current transformer is as follows: Among them, is the secondary circuit impedance of the current transformer, is the value of the magnetizing impedance referred to the secondary side.

2. The method for monitoring the error of a current transformer according to claim 1, wherein The equivalent circuit parameters of the current transformer include equivalent excitation inductance, equivalent excitation resistance, equivalent excitation distributed capacitance, equivalent secondary loop inductance, equivalent secondary loop resistance, and equivalent secondary loop distributed capacitance.

3. The error monitoring method of a current transformer as claimed in claim 1, characterized in that, Optimization objective function f is as follows: Among them, is the weight coefficient; n is the number of different frequency data selected; is the total loop impedance of the current transformer.

4. The current transformer error monitoring method according to claim 1, characterized in that, Use the genetic algorithm to solve the optimization objective function.

5. The method for monitoring the error of a current transformer according to claim 1, characterized in that, The frequency of the off-frequency test signal is selected to be 1000Hz - 10000Hz.

6. A current transformer error monitoring system, characterized in that, Using the current transformer error monitoring method according to any one of claims 1-5, including: A measurement module configured to obtain the total impedance of the current transformer loop measured by the off-frequency test signal; An equivalent module configured to obtain the equivalent loop impedance of the current transformer according to the equivalent circuit of the current transformer; A target solving module configured to construct an optimization objective function with the goal of minimizing the difference between the total loop impedance and the equivalent loop impedance, and solve the optimization objective function to obtain the equivalent circuit parameters of the current transformer; An error solving module configured to obtain the operating error of the current transformer according to the equivalent circuit parameters of the current transformer.

7. An electronic device, characterized in that, Including a memory, a processor, and computer instructions stored on the memory and running on the processor. When the computer instructions are run by the processor, the method according to any one of claims 1-5 is completed.

8. A computer-readable storage medium, characterized in that, For storing computer instructions, when the computer instructions are executed by the processor, the method according to any one of claims 1-5 is completed.

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