High-voltage current transformer error approximation evaluation method and system based on initial error

Abstract

The application discloses a high-voltage current transformer error approximation evaluation method and system based on initial error, relates to the technical field of power systems and electrical engineering, and comprises the following steps: monitoring data and performing data preprocessing; inputting current transformer basic parameters collected by each channel; collecting real-time data of operating current transformer measurement windings at a high frequency by using a current transformer online monitoring device; inversely deducing a real primary signal of the current transformer according to a current transformer error calculation formula; establishing a KCL loop composed of no less than one current transformer to be monitored, and constructing a matrix equation of the primary signal of the group current transformer; and adopting an approximation method to adjust error values of each current transformer and output the error of each operating current transformer. The modeling of the patent does not rely on accurate parameters of operating equipment, so that the accuracy of the model is not affected when parameters of transformers and current transformers change with operating conditions, and defects existing in current transformer error evaluation based on physical modeling are avoided.

Description

Technical Field

[0001] This invention relates to the fields of power systems and electrical engineering technology, specifically to a method and system for approximating and evaluating the error of high-voltage current transformers based on initial error. Background Technology

[0002] High-voltage current transformers are used to convert large primary currents into smaller currents according to a set ratio for use in metering, measurement, and protection equipment. The signal from the metering winding of a high-voltage current transformer is connected to a gate meter, and the accuracy of this signal directly affects the fairness of electricity trade settlement, making it extremely important. After long-term operation, a small number of current transformers may experience errors exceeding the error limit in their metering windings. These transformers require further manual fault assessment. Traditionally, the method for assessing anomalies in the metering windings of current transformers involves comparing the secondary signals of a standard current transformer with those of a current transformer with the same rated transformation ratio under offline conditions during a power outage. However, this offline error detection method deviates from the actual operating environment of the current transformers, resulting in some current transformers exhibiting errors exceeding the limit during operation, making it impossible to detect out-of-tolerance events in a timely manner. To accurately and promptly detect the metering status of operating current transformers and obtain accurate information on their operational errors, online monitoring technology for current transformer errors has become a hot topic and a challenge in the development of electricity metering devices.

[0003] Research on current transformer error assessment technology mainly focuses on simulating actual operating conditions offline and analyzing the influence of multi-dimensional factors on current transformer errors. In terms of online current transformer error assessment, the research mainly targets electronic current transformers, using traditional current transformers as reference standards to compare the relative changes in errors of electronic current transformers with the same voltage level, phase sequence, and transformation ratio.

[0004] Currently, error assessment methods for operating high-voltage current transformers are mainly divided into two categories: online monitoring technology based on physical modeling and online monitoring technology based on signal processing. The approach of online monitoring technology based on physical modeling is to use analytical modeling to abstract the physical model of the transformer into a mathematical model containing multiple parameters. Precise values ​​of each parameter are obtained by consulting design documents or historical operating data, and the operating error of the transformer is monitored online using the idea of ​​solving equations. This method is theoretically feasible, but the modeling requires precise parameters of multiple devices, including the transformer and the transformer itself, during operation. However, the output signals of these devices are easily affected by the operating environment, making the physical modeling method insufficient to support the error assessment requirements of 0.2-level current transformers. The approach of online monitoring technology based on signal processing is to use relevant signal processing methods to sample and analyze the high-frequency instantaneous values ​​of the output signal of a single transformer, performing signal transformation, separation, and extraction to find feature vectors characterizing abnormal operating states of the transformer. Based on the physical relationship between the abnormal operating state of the system and the obtained feature vectors, the system operating state is analyzed and detected, thereby determining the operating error of the voltage transformer. This method does not require the establishment of an accurate model and is effective in detecting abrupt anomalies, but it cannot detect the gradual changes in current transformer errors during long-term operation. Summary of the Invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the technical problem solved by this invention is: how to improve the ability to capture gradual signals by adopting a relative deviation test method, solve the defect that current transformer error assessment based on signal processing modeling cannot detect gradual error changes, and realize the transformation from qualitative metrological status assessment to quantitative error data analysis.

[0007] To address the aforementioned technical problems, this invention provides the following technical solution: a high-voltage current transformer error approximation evaluation method based on initial error, comprising the following steps: real-time monitoring and data preprocessing; inputting the basic parameters of the current transformer collected from each channel; using an online current transformer monitoring device to collect real-time data of the metering windings of the operating current transformer at high frequency; back-calculating the true primary signal of the current transformer according to the current transformer error calculation formula; establishing at least one KCL loop composed of the monitored current transformers, and constructing the matrix equation of the primary signal of the group of current transformers; and using an approximation method to adjust the error value of each current transformer and outputting the error of each operating current transformer.

[0008] As a preferred embodiment of the high-voltage current transformer error approximation evaluation method based on initial error described in this invention, the basic parameters of the current transformer collected by each input channel include the transformation ratio, the basic ratio difference under different rated currents, and the basic phase difference.

[0009] The data preprocessing involves denoising the collected state data, removing missing values, outliers, and invalid data with incorrect formats, converting the original format data into the format required for requirements analysis, and normalizing the data to complete the data preprocessing.

[0010] As a preferred embodiment of the high-voltage current transformer error approximation evaluation method based on initial error described in this invention, the real-time data of the metering winding of the operating current transformer collected includes the effective value of current, the effective value of phase, and the frequency.

[0011] As a preferred embodiment of the high-voltage current transformer error approximation evaluation method based on initial error described in this invention, the method for inversely estimating the true primary signal of the current transformer is based on the current transformer error calculation formula, establishing an equation between the primary current and the secondary current, expressed as:

[0012]

[0013] δ=δ 标 -δ 检

[0014]

[0015] Among them, I 标 I represents the effective value of the amplitude of the standard current signal. 检 δ is the effective value of the amplitude of the detected current signal. 标 δ is the initial phase angle of the standard current signal. 检 The initial phase angle of the detected current signal is denoted as . The primary current of the first current transformer. δ1 is the secondary current of the first current transformer, k is the rated current ratio, f1 is the ratio difference of the first current transformer, and δ1 is the phase difference of the first current transformer.

[0016] As a preferred embodiment of the high-voltage current transformer error approximation evaluation method based on initial error described in this invention, the real part and imaginary part of the current transformer are calculated.

[0017] The expression for calculating the real part of the current transformer is:

[0018] I=(1+f)βk

[0019] Where I is the real part of the current transformer, f is the ratio difference, β is the effective value of the amplitude, and k is the rated current ratio.

[0020] J = COS[(α+B) / 60 / 180PI]βk

[0021] Where J is the imaginary part of the current transformer, α is the effective value of the phase, B is the initial phase difference, and the unit of (α+B) is ′. Divide by 60 to convert ′ to °, then divide by 180PI to convert ° to radians. Perform trigonometric function calculations and multiply the effective value of the amplitude and the ratio of the rated current to output the imaginary part of the current transformer.

[0022] As a preferred embodiment of the high-voltage current transformer error approximation evaluation method based on initial error described in this invention, the following steps are taken: according to the KCL matrix equation, the algebraic sum of the currents flowing out of any node is equal to zero; the real parts of all inflow nodes of the substation are added together and the real parts of all outflow nodes of the substation are subtracted; then the imaginary parts of all inflow nodes of the substation are added together and the imaginary parts of all outflow nodes of the substation are subtracted; and the error of the current transformer is determined to be zero.

[0023] If the error of the current transformer cannot satisfy the KCL vector sum to be zero, an approximation method is used to adjust the error of several current transformers.

[0024] As a preferred embodiment of the high-voltage current transformer error approximation evaluation method based on initial error described in this invention, the approximation method first adjusts the error value of only a single current transformer, including the ratio difference and phase difference, in the order from the 1st to the nth transformer; if an error occurs during the adjustment that satisfies the condition that the sum of the KCL vectors is zero, the error value of each current transformer after adjustment is recorded, and the adjusted error is the operating error of each current transformer; if the sum of the KCL vectors cannot be equal to zero after the adjustment cycle, the number of current transformers participating in the adjustment is increased. The number of current transformers is adjusted simultaneously using a round-robin method. First, the first and second current transformers are adjusted; if this is not achieved, the first and third are adjusted, and so on, until the first, nth, or nth and (n+1th)th current transformers achieve a KCL vector sum of zero. If adjusting either current transformer fails to achieve a KCL vector sum of zero, the number of current transformers involved in error adjustment is increased: nth, (n+1th), (n+2th) until the KCL vector sum is zero. The errors of all adjusted current transformers are recorded, i.e., the operating error value of each current transformer.

[0025] Another objective of this invention is to provide a high-voltage current transformer error approximation evaluation system based on initial error. This system can accurately evaluate the error of each operating current transformer by real-time monitoring of its operating data, processing and analyzing this data, and then adjusting the error value of the current transformer using an approximation method. This solves the problem of power system instability caused by inaccurate evaluation of current transformer errors in existing technologies, thereby improving the stability and reliability of the power system.

[0026] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high-voltage current transformer error approximation evaluation system based on initial error, comprising: a data acquisition module, a data preprocessing module, a parameter input module, an error calculation module, and an error approximation module.

[0027] The data acquisition module monitors the operating data of the current transformer in real time, including the effective value of the current, the effective value of the phase, and the frequency, and transmits the acquired raw data to the data preprocessing module.

[0028] The data preprocessing module processes the raw data received from the data acquisition module, including denoising, removing missing values, outliers, and invalid data with incorrect formats, converting the raw format data into the format required for requirements analysis, and performing data normalization. The processed data is then transmitted to the error calculation module.

[0029] The parameter input module receives the basic parameters of the current transformer input by the user, including the transformation ratio, the basic ratio difference under different rated currents, and the basic phase difference, and transmits the received basic parameters of the current transformer to the error calculation module.

[0030] The error calculation module reverse-engineers the true primary signal of the current transformer based on the current transformer error calculation formula, calculates the real and imaginary parts of the current transformer, and finally determines whether the current transformer error is zero based on the KCL matrix equation, and transmits the calculated error value to the error approximation module.

[0031] The error approximation module uses an approximation method to adjust the error value of each current transformer until the KCL vector sum is zero. Finally, it outputs the error of each operating current transformer and transmits the approximated error value to the data preprocessing module.

[0032] A computer device includes a memory and a processor, the memory storing a computer program, characterized in that the processor executes the computer program to implement the steps of the high-voltage current transformer error approximation evaluation method based on initial error as described above.

[0033] A computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements the steps of the high-voltage current transformer error approximation evaluation method based on initial error as described above.

[0034] The beneficial effects of this invention are as follows: The modeling in this patent does not rely on the precise parameters of the operating equipment. Therefore, changes in the parameters of transformers and instrument transformers due to operating conditions will not affect the accuracy of the model. This technology avoids the shortcomings of current transformer error assessment based on physical modeling, and the model has strong engineering applicability. Based on the characteristics of the monitored object, this invention proposes an error-stepping method based on initial error to achieve quantitative analysis of errors in high-voltage current transformers during operation. It is not limited by parameter changes caused by operating conditions, can accurately detect gradual error changes, has strong engineering applicability, and possesses broad market potential. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0036] Figure 1 The overall flowchart of the high-voltage current transformer error approximation evaluation method based on initial error provided in the first embodiment of the present invention;

[0037] Figure 2 This is a structural diagram of a high-voltage current transformer error approximation evaluation system based on initial error provided in the second embodiment of the present invention;

[0038] Figure 3 The topology diagram of the 220kV to 110kV line of a 220kV substation is provided for the high-voltage current transformer error approximation evaluation method based on initial error, which is the second embodiment of the present invention. Detailed Implementation

[0039] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0040] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0041] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0042] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0043] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0044] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] Example 1

[0046] Reference Figure 1 As an embodiment of the present invention, a method for approximating and evaluating the error of a high-voltage current transformer based on initial error is provided, characterized in that:

[0047] Real-time monitoring and data preprocessing are performed; basic parameters of the current transformers collected from each channel are input; real-time data of the metering windings of the operating current transformers are collected at high frequency using an online monitoring device for current transformers; the true primary signal of the current transformer is inversely calculated based on the current transformer error calculation formula; at least one KCL loop is established for the monitored current transformers, and the matrix equation of the primary signal of the group of current transformers is constructed; the error value of each current transformer is adjusted using an approximation method, and the error of each operating current transformer is output.

[0048] The basic parameters of the current transformer collected by each input channel include the turns ratio, the basic ratio difference under different rated currents, and the basic phase difference.

[0049] The data preprocessing involves denoising the collected state data, removing missing values, outliers, and invalid data with incorrect formats, converting the original format data into the format required for requirements analysis, and normalizing the data to complete the data preprocessing.

[0050] The real-time data collected from the metering windings of the current transformer includes the effective value of the current, the effective value of the phase, and the frequency.

[0051] The method for calculating the true primary signal of the current transformer is based on the current transformer error calculation formula, establishing an equation between the primary and secondary currents, expressed as follows:

[0052]

[0053] δ=δ 标 -δ 检

[0054]

[0055] Among them, I 标 I represents the effective value of the amplitude of a standard current signal. 检 δ is the effective value of the amplitude of the detected current signal. 标 δ is the initial phase angle of the standard current signal. 检 The initial phase angle of the detected current signal is denoted as . The primary current of the first current transformer. δ1 is the secondary current of the first current transformer, k is the rated current ratio, f1 is the ratio difference of the first current transformer, and δ1 is the phase difference of the first current transformer.

[0056] Calculate the real and imaginary parts of a current transformer;

[0057] The expression for calculating the real part of the current transformer is:

[0058] I=(1+f)βk

[0059] Where I is the real part of the current transformer, f is the ratio difference, β is the effective value of the amplitude, and k is the rated current ratio.

[0060] J = COS[(α+B) / 60 / 180PI]βk

[0061] Where J is the imaginary part of the current transformer, α is the effective value of the phase, B is the initial phase difference, and the unit of (α+B) is ′. Divide by 60 to convert ′ to °, then divide by 180PI to convert ° to radians. Perform trigonometric function calculations and multiply the effective value of the amplitude and the ratio of the rated current to output the imaginary part of the current transformer.

[0062] According to the KCL matrix equation, the algebraic sum of the currents flowing out of any node is equal to zero. Calculate the sum of the real parts of all the currents flowing into the substation and subtract the real parts of all the currents flowing out of the substation. Then calculate the sum of the imaginary parts of all the currents flowing into the substation and subtract the imaginary parts of all the currents flowing out of the substation. Determine whether the error of the current transformer is zero.

[0063] If the error of the current transformer cannot satisfy the KCL vector sum to be zero, an approximation method is used to adjust the error of several current transformers.

[0064] The approximation method first adjusts the error value of a single current transformer, including the ratio difference and phase difference, in the order from the 1st to the nth transformer. If an error occurs during the adjustment that satisfies the condition that the KCL vector sum is zero, the error value of each current transformer after adjustment is recorded, and the adjusted error is the operating error of each current transformer. If the KCL vector sum cannot be equal to zero after the adjustment cycle, the number of current transformers involved in the adjustment is increased, and the error values ​​of two current transformers are adjusted simultaneously, using a round-robin method, starting with the first and second transformers, and if the condition is not met, adjusting the first and third transformers, and so on, until the KCL vector sum of the first, nth, or nth and n+1th transformers is zero. If adjusting two current transformers cannot make the KCL vector sum zero, the number of current transformers involved in the error adjustment continues to increase, from the nth transformer, the n+1th transformer, the n+2th transformer until the KCL vector sum is zero, and the error of all adjusted current transformers is recorded, which is the operating error value of each current transformer.

[0065] Example 2

[0066] Reference Figure 2 As an embodiment of the present invention, a system for evaluating the error approximation of a high-voltage current transformer based on initial error is provided, characterized in that it includes a data acquisition module, a data preprocessing module, a parameter input module, an error calculation module, and an error approximation module.

[0067] The data acquisition module monitors the operating data of the current transformer in real time, including the effective value of the current, the effective value of the phase, and the frequency, and transmits the acquired raw data to the data preprocessing module.

[0068] The data preprocessing module processes the raw data received from the data acquisition module, including denoising, removing missing values, outliers, and invalid data with incorrect formats. It converts the raw data into the format required for requirements analysis, performs data normalization, and transmits the processed data to the error calculation module.

[0069] The parameter input module receives the basic parameters of the current transformer input by the user, including the transformation ratio, the basic ratio difference under different rated currents, and the basic phase difference, and transmits the received basic parameters of the current transformer to the error calculation module.

[0070] The error calculation module reverse-engineers the true primary signal of the current transformer based on the current transformer error calculation formula, calculates the real and imaginary parts of the current transformer, and finally determines whether the current transformer error is zero based on the KCL matrix equation, and transmits the calculated error value to the error approximation module.

[0071] The error approximation module uses an approximation method to adjust the error value of each current transformer until the KCL vector sum is zero. Finally, it outputs the error of each operating current transformer and transmits the approximated error value to the data preprocessing module.

[0072] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion 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 described in 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.

[0073] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0074] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0075] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0076] Example 3

[0077] Figure 3 As one embodiment of the present invention, in order to verify the beneficial effects of the present invention, scientific demonstration was carried out through economic benefit calculations and simulation experiments. This embodiment conducted experiments on both existing conventional methods and the method of this embodiment.

[0078] The metering windings of high-voltage current transformers are generally of the 0.2 or 0.2S class, so the calculated error of the current transformer only needs to meet an accuracy of 0.2%. This invention controls the calculation accuracy to 0.1%, that is, the real part of KCL is considered to be within ±0.001 and the imaginary part is within ±0.003, which is considered to be 0.

[0079] The topology of the 220kV to 110kV line of a certain 220kV substation is as follows: Figure 3 As shown, the station has two 220kV incoming lines and four 110kV outgoing lines. The bus tie is closed. The four sets of current transformers CT1, CT2, CT3, and CT4 on the outgoing lines, together with the two sets of current transformers CT4 and CT5 on the incoming lines, form a KCL loop. Taking phase A of each set of current transformers as an example, calculate the operating error value of each current transformer. First, assume that the basic parameters of all current transformers are as shown in Table 1.

[0080] Table 1 Basic parameters of phase A of six sets of current transformers

[0081]

[0082] Assume that the actual data of each current transformer at a certain moment is as shown in Table 2.

[0083] Table 2. Data collected from phase A of six current transformers at a certain moment.

[0084]

[0085] The calculation steps are as follows:

[0086] 1) Based on the current transformer error calculation formula, substitute the basic parameters and collected data to obtain the actual primary current value of each current transformer.

[0087] The primary current of current transformer CT1 can be expressed as: The secondary current of current transformer CT1 can be expressed as: The rated current ratio is denoted as k, the ratio difference as f1, and the phase difference as δ1. Based on the current transformer error calculation formula, the equation between the primary and secondary currents is established: By analogy, the primary current vectors of phase A of the six current transformers were obtained, and the results are shown in Table 3.

[0088] Table 3 shows the primary current data of phase A of the six current transformers at a certain moment.

[0089]

[0090] 2) Establish the KCL matrix equation and calculate whether the vector sum of this equation is zero when the initial error is used for each current transformer. If it is equal to zero, the operating error of the current transformer is the same as the initial error. If it is not equal to zero, the approximation method is used to adjust the error of the current transformer.

[0091] The real part of the current transformer is calculated by multiplying the effective value of the amplitude by (1 + ratio difference) by the rated current ratio.

[0092] The real and imaginary parts of the current transformer are calculated using cos[(effective phase value + initial phase difference) / 60 / 180×PI]×effective amplitude value×rated current ratio.

[0093] Taking the first data point as an example, let's refine the solution process:

[0094] CT1 has a k of 1000, a ratio difference of +0.15%, and a second data acquisition of 0.2321A.

[0095] The real part is calculated as follows: 0.2321 × (1 + 0.15%) × 1000 = 232.448.

[0096] The imaginary part is calculated as: cos[(6177.18+5.0) / 60 / 180×PI]×0.2321×1000=-51.687. Here, (-6177.18+5.0) is in degrees (°). Dividing by 60 converts the degrees to degrees (°), then dividing by 180×PI converts the degrees to radians. A trigonometric function calculation is performed, and finally multiplied by ki1, resulting in 0.2321×1000, which gives the imaginary part. PI=3.1415926. Following this method, the real and imaginary parts of all current transformers are calculated. Finally, using the formula I′1+I′2+I′3+I′4+I′5+I′6≈0, and substituting the real and imaginary parts obtained in step 1, we get:

[0097] For the real part: 232.448 + 227.441 + 243.440 + 240.136 + (-468.268) + (-473.673) = 1.524 ≠ 0

[0098] For the imaginary part: -51.687 -40.819 -32.662 -52.272 -(-93.011) -(-83.855) = -0.584 ≠ 0

[0099] The initial error cannot satisfy the KCL vector sum to be zero, so the error of the current transformer changes during operation, and an approximation method is needed to adjust the error of several current transformers.

[0100] 3) First, adjust the error of a single current transformer. If the matrix cannot be adjusted to zero according to the boundary requirements, increase the number of current transformers with adjusted errors. Adjust the matrix parameters by gradually approximating the matrix to obtain the error of each current transformer that satisfies the relationship.

[0101] Adjust the ratio difference f1 and phase difference δ1 of CT1 in steps of ±0.01% and ±0.1′, respectively. When CT1 is adjusted to the positive boundary values, i.e., +0.20% and 10′, the minimum solutions to the KCL equation are 1.640 and -0.25, which still cannot make the KCL vector sum zero. Therefore, it is necessary to adjust the error values ​​of multiple current transformers. The programming software automatically finds the optimal solution, obtaining the error values ​​of phase A of 6 sets of current transformers that satisfy the KCL vector sum of 0, as shown in Table 4.

[0102] Table 4. Adjustment errors of phase A of six groups of current transformers

[0103]

[0104] The real and imaginary data of each current transformer after error adjustment are shown in Table 5.

[0105] Table 5. Data for Phase A of the six current transformers after error adjustment.

[0106]

[0107] After adjustment, the real and imaginary parts are calculated according to I1′+I2′+I3′+I4′+I5′+I6′≈0, resulting in:

[0108] Real part: 232.170 + 227.191 + 243.270 + 239.968 + (-468.595) + (-474.004) = -0.001 ≈ 0

[0109] For the imaginary part: -51.512 -40.676 -32.508 -52.306 -(-93.144) -(-83.855) = -0.002 ≈ 0

[0110] 4) Obtain the error value of each current transformer during operation.

[0111] By using approximation error adjustment, the vector sum of the primary currents of multiple sets of current transformers in the plant is made zero. The adjusted error values ​​for each current transformer are shown in Table 4. This completes the calculation of the operating error value for each current transformer.

[0112] The approximation-based error adjustment method of this patent invention is based on the fact that 80% of the current transformers involved in monitoring have a ratio difference within ±0.20% and a phase difference within ±10.0′. Therefore, when adjusting the ratio difference and phase difference based on the initial error, the superimposed ratio difference and error will have an 80% probability that the ratio difference is within ±0.20% and the phase difference is within ±10.0′. This 80% is derived from a large amount of empirical error detection in the field, meaning that 80% of the current transformers meet the requirement of a ratio difference within ±0.20% and a phase difference within ±10.0′. This value serves as the boundary for approximation error adjustment in this patent. When adjusting the error of a single current transformer, if the KCL does not satisfy the vector sum being zero after adjustment of the current transformer with an 80% probability, then proceed to the next stage, which is to increase the number of current transformers for error adjustment. Similarly, the ratio difference of the current transformers with an 80% probability is controlled within ±0.20%, and the phase difference is controlled within ±10.0′ for error adjustment. Otherwise, proceed to the next stage and continue to increase the number of current transformers for adjustment.

[0113] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for approximating and evaluating the error of a high-voltage current transformer based on initial error, characterized in that, include: Real-time data monitoring and data preprocessing; Input the basic parameters of the current transformer collected for each channel; The online monitoring device for current transformers is used to collect real-time data of the metering windings of the operating current transformers at high frequency. The true primary signal of the current transformer can be deduced by using the current transformer error calculation formula. Establish at least one KCL loop composed of the monitored current transformers, and construct the matrix equation of the primary signal of the group of current transformers; An approximation method is used to adjust the error value of each current transformer and output the error of each operating current transformer. The approximation method first adjusts the error value of a single current transformer, including the ratio difference and phase difference, in the order from the 1st to the nth transformer. If an error occurs during the adjustment that satisfies the condition that the KCL vector sum is zero, the error value of each current transformer after adjustment is recorded, and the adjusted error is the operating error of each current transformer. If the KCL vector sum cannot be equal to zero after the adjustment cycle, the number of current transformers involved in the adjustment is increased, and the error values ​​of two current transformers are adjusted simultaneously, using a round-robin method, starting with the first and second transformers, and if the condition is not met, adjusting the first and third transformers, and so on, until the KCL vector sum of the first, nth, or nth and n+1th transformers is zero. If adjusting two current transformers cannot make the KCL vector sum zero, the number of current transformers involved in the error adjustment continues to increase, from the nth transformer, the n+1th transformer, the n+2th transformer until the KCL vector sum is zero, and the error of all adjusted current transformers is recorded, which is the operating error value of each current transformer.

2. The high-voltage current transformer error approximation evaluation method based on initial error as described in claim 1, characterized in that: The basic parameters of the current transformer collected by each input channel include the turns ratio, the basic ratio difference under different rated currents, and the basic phase difference. The data preprocessing involves denoising the collected state data, removing missing values, outliers, and invalid data with incorrect formats, converting the original format data into the format required for requirements analysis, and normalizing the data to complete the data preprocessing.

3. The high-voltage current transformer error approximation evaluation method based on initial error as described in claim 2, characterized in that: The real-time data collected from the metering windings of the current transformer includes the effective value of the current, the effective value of the phase, and the frequency.

4. The high-voltage current transformer error approximation evaluation method based on initial error as described in claim 3, characterized in that: The method for calculating the true primary signal of the current transformer is based on the current transformer error calculation formula, establishing an equation between the primary and secondary currents, expressed as follows: ， ， ， in, This represents the effective value of the amplitude of the standard current signal. The effective value of the amplitude of the detected current signal. The initial phase angle of the standard current signal. The initial phase angle of the detected current signal is denoted as . The primary current of the first current transformer. This is the secondary current of the first current transformer. Rated current ratio The ratio difference of the first current transformer. The phase difference is the phase difference of the first current transformer.

5. The high-voltage current transformer error approximation evaluation method based on initial error as described in claim 4, characterized in that: Calculate the real and imaginary parts of a current transformer; The expression for calculating the real part of the current transformer is: ， in, Let be the real part of the current transformer. The difference in ratios, This is the effective value of the amplitude. Rated current ratio ， in, This represents the imaginary part of the current transformer. This is the effective value of the phase. The initial phase difference, The unit is ´. Divide by 60 to convert ´ to °, then divide by 180PI to convert ° to radians. Perform trigonometric function calculations and multiply the effective value of the amplitude and the ratio of the rated current to output the imaginary part of the current transformer.

6. The high-voltage current transformer error approximation evaluation method based on initial error as described in claim 5, characterized in that: According to the KCL matrix equation, the algebraic sum of the currents flowing out of any node is equal to zero. Calculate the sum of the real parts of all the currents flowing into the substation and subtract the real parts of all the currents flowing out of the substation. Then calculate the sum of the imaginary parts of all the currents flowing into the substation and subtract the imaginary parts of all the currents flowing out of the substation. Determine whether the error of the current transformer is zero. If the error of the current transformer cannot satisfy the KCL vector sum to be zero, an approximation method is used to adjust the error of several current transformers.

7. A system employing the high-voltage current transformer error approximation evaluation method based on initial error as described in any one of claims 1 to 6, characterized in that: It includes a data acquisition module, a data preprocessing module, a parameter input module, an error calculation module, and an error approximation module; The data acquisition module monitors the operating data of the current transformer in real time, including the effective value of the current, the effective value of the phase, and the frequency, and transmits the acquired raw data to the data preprocessing module. The data preprocessing module processes the raw data received from the data acquisition module, including denoising, removing missing values, outliers, and invalid data with incorrect formats, converting the raw format data into the format for requirements analysis, normalizing the data, and transmitting the processed data to the error calculation module. The parameter input module receives the basic parameters of the current transformer input by the user, including the transformation ratio, the basic ratio difference under different rated currents, and the basic phase difference, and transmits the received basic parameters of the current transformer to the error calculation module. The error calculation module reverse-engineers the true primary signal of the current transformer based on the current transformer error calculation formula, calculates the real and imaginary parts of the current transformer, and finally determines whether the current transformer error is zero based on the KCL matrix equation, and transmits the calculated error value to the error approximation module. The error approximation module uses an approximation method to adjust the error value of each current transformer until the KCL vector sum is zero. Finally, it outputs the error of each operating current transformer and transmits the approximated error value to the data preprocessing module.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the high-voltage current transformer error approximation evaluation method based on initial error as described in any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the high-voltage current transformer error approximation evaluation method based on initial error as described in any one of claims 1 to 6.

Images