A power distribution network line selection method based on a principal component sample matrix of a fault line

Abstract

This invention discloses a distribution network line selection method based on a principal component sample matrix of faulted lines, comprising: collecting transient information of faulted lines under different fault conditions; performing principal component analysis on the transient information to construct a principal component sample matrix; calculating the zero-sequence voltage change gradient sum based on the collected zero-sequence voltage; determining whether to activate the line selection device based on the zero-sequence voltage change gradient sum, and activating the line selection device when the gradient sum is greater than a preset threshold; extracting the transient information after each line fault, performing correlation analysis between each line and the principal component sample matrix to form a line selection correlation matrix; calculating a comprehensive line selection matrix based on the line selection correlation matrix; determining a faulted line discrimination matrix based on the comprehensive line selection matrix; and determining the faulted line based on the faulted line discrimination matrix. This invention's distribution network line selection method based on a principal component sample matrix of faulted lines changes the activation criterion of the line selection device, utilizes rich fault transient information to select faulted lines, and improves the reliability of the line selection results.

Description

Technical Field

[0001] This invention relates to the field of power fault diagnosis technology, and in particular to a distribution network line selection method based on the principal component sample matrix of faulted lines. Background Technology

[0002] The power workshops of cigarette manufacturing enterprises are equipped with many low-current grounding systems. When a single-phase grounding fault occurs in a low-current grounding system, the line voltage remains symmetrical and the impact on the power supply to the load is minimal. Regulations stipulate that the system can still operate for 1 to 2 hours.

[0003] However, with the rapid development of urban power distribution networks in recent years, the proportion of cable lines has been increasing. When a single-phase ground fault occurs, the increased capacitance to ground will generate a large capacitive current. Over long-term operation, this can easily develop into a phase-to-phase fault or other progressive fault, causing the fault to escalate and compromising power supply stability. Furthermore, traditional fault location devices typically detect a single-phase ground fault when the neutral point voltage exceeds 15% of the phase voltage. However, this criterion is time-consuming and has poor sensitivity in cases of high-resistance ground faults.

[0004] Therefore, there is an urgent need for a distribution network line selection method based on the principal component sample matrix of faulted lines. Summary of the Invention

[0005] The purpose of this invention is to provide a distribution network line selection method based on the principal component sample matrix of faulted lines, so as to solve the problems in the prior art. It can change the start-up criteria of the line selection device, use rich fault transient information to select faulted lines, and improve the reliability of the line selection results.

[0006] This invention provides a distribution network line selection method based on the principal component sample matrix of faulted lines, comprising:

[0007] Collect transient information of faulty lines under different fault conditions to form fault samples;

[0008] Principal component analysis was performed on the transient information of faulted lines under different fault conditions to construct a principal component sample matrix;

[0009] Based on the collected zero-sequence voltage, calculate the zero-sequence voltage change gradient;

[0010] Based on the calculation results of the zero-sequence voltage change gradient, it is determined whether to activate the line selection device. When the gradient is greater than the preset threshold, a single-phase ground fault is determined to have occurred, and the line selection device is activated.

[0011] Extract transient information after each line fault, and perform correlation analysis on each line with the principal component sample matrix to form a line selection correlation matrix;

[0012] Calculate the comprehensive route selection matrix based on the route selection correlation matrix;

[0013] Determine the fault line discrimination matrix based on the comprehensive route selection matrix;

[0014] The faulty line is determined based on the faulty line discrimination matrix.

[0015] The distribution network line selection method based on the principal component sample matrix of faulted lines, as described above, preferably includes the following step: performing principal component analysis on the transient information of faulted lines under different fault conditions to construct the principal component sample matrix.

[0016] In the process of principal component analysis, the cumulative proportion of principal components is set as y, and the dimension of principal components is determined based on the cumulative proportion of principal components in order to construct the principal component sample matrix D.

[0017] The distribution network line selection method based on the principal component sample matrix of the faulted line, as described above, preferably includes the following step: calculating the zero-sequence voltage change gradient based on the principal component sample matrix.

[0018] The gradient c of the zero-sequence voltage change is calculated using the following formula, based on the sampling interval, the number of instantaneous sampling points, and the zero-sequence voltage difference between two adjacent sampling points. dif ,

[0019] c dif (k)=[u0(k)-u0(k-1)] / Δt (1)

[0020] u0() represents the zero-sequence voltage, k represents the number of instantaneous sampling points, and Δt represents the sampling interval in milliseconds;

[0021] Based on the calculation results of the zero-sequence voltage change gradient, the zero-sequence voltage change gradient and E(k) are calculated using the following formula:

[0022]

[0023] Where K represents the number of sampling points within a certain time window, and k≥K.

[0024] The distribution network line selection method based on the principal component sample matrix of faulted lines, as described above, preferably includes the following steps: extracting transient information after each line fault and performing a correlation analysis between each line and the principal component sample matrix to form a line selection correlation matrix.

[0025] Based on the correlation coefficients between the current route and each principal component, the route selection correlation matrix M is constructed as shown below.

[0026]

[0027] Where m represents the number of system routes, d represents the dimension of the principal component sample matrix, i = 1, 2, ..., m, j = 1, 2, ..., d, and in the route selection correlation matrix M, each row contains the correlation coefficient between the route and each principal component, ρ ij Let represent the correlation coefficient between the i-th line and the principal component j, where i = 1, 2, ..., m, j = 1, 2, ..., d.

[0028] The distribution network route selection method based on the principal component sample matrix of faulted lines, as described above, preferably includes the following step: calculating the comprehensive route selection matrix based on the route selection correlation matrix.

[0029] Based on the route selection correlation matrix, the elements ρ in the comprehensive route selection matrix ρ are calculated using the following formula. i ,

[0030]

[0031] Where i = 1, 2, ..., m, j = 1, 2, ..., d.

[0032] The distribution network line selection method based on the principal component sample matrix of faulted lines described above, preferably, involves determining the faulted line discrimination matrix based on the comprehensive line selection matrix, specifically including:

[0033] Based on the sign of each element in the comprehensive route selection matrix, the fault line discrimination matrix S is determined. The elements Sfault line discrimination matrix in S are calculated using the following formula. i ,

[0034] s i =sgn(ρ i (4)

[0035] Where i = 1, 2, ..., m.

[0036] The distribution network line selection method based on the principal component sample matrix of faulted lines described above, preferably, involves determining the faulted line according to the faulted line discrimination matrix, specifically including:

[0037] In the fault line discrimination matrix, if all elements are -1, the fault line is determined to be a bus fault; if an element is 1, the fault line is determined to be the feeder corresponding to element 1.

[0038] This invention provides a distribution network fault location method based on a principal component sample matrix of faulted lines. The method uses the zero-sequence voltage change gradient as a criterion for single-phase grounding fault occurrence. Utilizing abundant transient information at the onset of a fault, transient information samples of the faulted lines under different fault conditions are collected to establish a principal component sample matrix of the faulted lines. Correlation analysis is then used to form a final fault location discrimination matrix, thereby identifying the faulted line. When a single-phase grounding fault occurs, the transient information of each line is extracted and correlated with the principal component sample matrix to form a fault location correlation matrix. The average value of the correlation coefficients of each line is used as the comprehensive correlation matrix for fault location, and a symbolic algorithm is used to construct the fault location discrimination matrix to determine the faulted line. By adjusting the start-up threshold and the cumulative proportion setting of the principal components of the fault location device to adapt to distribution networks with different topologies, the method effectively improves the sensitivity of the fault location device's start-up, has a certain fault tolerance mechanism, and also improves the reliability of the fault location results. Attached Figure Description

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings, wherein:

[0040] Figure 1 A flowchart illustrating an embodiment of the distribution network line selection method based on the principal component sample matrix of faulted lines provided by the present invention;

[0041] Figure 2 A logic diagram illustrating the implementation process of the distribution network line selection method based on the principal component sample matrix of faulted lines provided by the present invention;

[0042] Figure 3 This is a schematic diagram of a power distribution network simulation model;

[0043] Figure 4 The zero-sequence voltage gradient and schematic diagram are shown when line L5 is faulted.

[0044] Figure 5 This is a diagram showing the zero-sequence voltage gradient during a fault in line L2. Detailed Implementation

[0045] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The descriptions of the exemplary embodiments are merely illustrative and are in no way intended to limit the present disclosure or its application or use. The present disclosure may be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided so that the present disclosure will be thorough and complete, and will fully express the scope of the disclosure to those skilled in the art. It should be noted that, unless specifically stated otherwise, the relative arrangement of components and steps, the composition of materials, numerical expressions, and values ​​set forth in these embodiments should be interpreted as exemplary only and not as limiting.

[0046] The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. Terms such as “including” or “contains” mean that the element preceding the term encompasses the element listed after it, and do not exclude the possibility of encompassing other elements as well. Terms such as “above” and “below” are used only to indicate relative positional relationships; when the absolute position of the described object changes, this relative positional relationship may also change accordingly.

[0047] In this disclosure, when a specific component is described as being located between a first component and a second component, an intermediary component may or may not be present between the specific component and the first or second component. When a specific component is described as connecting to other components, the specific component may be directly connected to the other components without having an intermediary component, or it may not be directly connected to the other components but may have an intermediary component.

[0048] All terms used in this disclosure (including technical or scientific terms) have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in a general dictionary, such as a dictionary, should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and not as having an idealized or highly formalized meaning, unless expressly defined herein.

[0049] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0050] Currently, there are three main categories of fault location methods for single-phase grounding faults in low-current grounding systems: steady-state method, first half-wave method, and signal injection method. The steady-state method compares the amplitudes of the zero-sequence current at the power frequency after the fault, identifying the line with the largest amplitude. Alternatively, it utilizes differences in the distribution network's parameters and the difference in zero-sequence admittance before and after the fault to construct a fault location criterion. The first half-wave method addresses this by concentrating the transient energy of the zero-sequence current primarily in the first half-wave after the fault, forming energy-based fault location criteria. The signal injection method offers greater versatility; for example, a resistor is connected in parallel with the arc suppression coil at the neutral point as a disturbance input, and the line is located based on the change in resistance before and after connection. Alternatively, additional signal sources can be added to identify the faulty line.

[0051] Existing technologies for selecting the fault location for single-phase grounding faults in low-current grounding systems have the following three shortcomings:

[0052] (1) Due to the compensation effect of the arc suppression coil, the zero-sequence current after steady state is small and easily disturbed, which affects the actual application effect. Moreover, when the topology of the distribution network changes, the zero-sequence admittance will also change. If an arc fault occurs, the steady-state zero-sequence current after the fault is not easy to obtain directly.

[0053] (2) With the development of urban power distribution networks, there are many mixed cable lines and cable lines. When an overhead line fails, the sudden change energy of the first half wave is not obvious, and there is a possibility of misselection.

[0054] (3) The injection method requires additional equipment, which will change the grounding method of the neutral point, leading to an increase in fault current and development into phase-to-phase fault, thus expanding the fault.

[0055] Therefore, adaptive optimizations and improvements are needed for single-phase grounding faults in low-current grounding systems.

[0056] like Figure 1 and Figure 2 As shown, the distribution network line selection method based on the principal component sample matrix of faulted lines provided in this embodiment includes the following steps in actual execution:

[0057] Step S1: Collect transient information of faulty lines under different fault conditions to form fault samples.

[0058] Step S2: Perform principal component analysis on the transient information of the faulted line under different fault conditions to construct the principal component sample matrix.

[0059] Specifically, in the principal component analysis process, the cumulative proportion of the principal components is set as y, and the dimension of the principal components is determined based on the cumulative proportion to construct the principal component sample matrix D. In this invention, the principal component sample matrix is ​​established based on the cumulative proportion through principal component analysis.

[0060] Step S3: Calculate the zero-sequence voltage change gradient based on the collected zero-sequence voltage.

[0061] In one embodiment of the distribution network line selection method based on the principal component sample matrix of faulted lines of the present invention, step S3 may specifically include:

[0062] Step S31: Based on the sampling interval, the number of instantaneous sampling points, and the zero-sequence voltage difference between two adjacent sampling points, calculate the zero-sequence voltage change gradient c using the following formula. dif ,

[0063] c dif (k)=[u0(k)-u0(k-1)] / Δt (1)

[0064] u0() represents the zero-sequence voltage, k represents the number of instantaneous sampling points, and Δt represents the sampling interval in milliseconds.

[0065] Step S32: Based on the calculation results of the zero-sequence voltage change gradient, calculate the zero-sequence voltage change gradient and E(k) using the following formula.

[0066]

[0067] Where K represents the number of sampling points within a certain time window, and k≥K.

[0068] Step S4: Based on the calculation results of the zero-sequence voltage change gradient, determine whether to activate the line selection device. When the gradient is greater than the preset threshold, it is determined that a single-phase ground fault has occurred, and the line selection device is activated.

[0069] The preset threshold can be, for example, w. It should be noted that the present invention does not specifically limit the preset threshold.

[0070] Step S5: Extract transient information after each line fault, and perform correlation analysis on each line with the principal component sample matrix to form a line selection correlation matrix.

[0071] Specifically, based on the correlation coefficients between the current route and each principal component, the route selection correlation matrix M is constructed as shown below.

[0072]

[0073] Where m represents the number of system routes, d represents the dimension of the principal component sample matrix, i = 1, 2, ..., m, j = 1, 2, ..., d, and in the route selection correlation matrix M, each row contains the correlation coefficient between the route and each principal component, ρ ij Let represent the correlation coefficient between the i-th line and the principal component j, where i = 1, 2, ..., m, j = 1, 2, ..., d.

[0074] Step S6: Calculate the comprehensive route selection matrix based on the route selection correlation matrix.

[0075] Specifically, based on the route selection correlation matrix, each element ρ in the comprehensive route selection matrix ρ is calculated using the following formula. i ,

[0076]

[0077] Where i = 1, 2, ..., m, j = 1, 2, ..., d. That is, the average value of the correlation coefficients of each route is used as the comprehensive correlation matrix for route selection.

[0078] Step S7: Determine the fault line discrimination matrix based on the comprehensive line selection matrix.

[0079] Specifically, based on the sign of each element in the comprehensive route selection matrix, the fault line discrimination matrix S is determined, and the elements Sfault line discrimination matrix in S are calculated using the following formula. i ,

[0080] s i =sgn(ρi (4)

[0081] Where i = 1, 2, ..., m.

[0082] Step S8: Determine the faulty line based on the faulty line discrimination matrix.

[0083] Specifically, in the fault line discrimination matrix, if all elements are -1, the fault line is determined to be a bus fault; if an element is 1, the fault line is determined to be the feeder corresponding to element 1.

[0084] In one embodiment of the present invention, such as Figure 3 The figure shows a simulation model of a single-phase grounding fault in a 110kV / 10kV distribution network, which contains 6 distribution feeders and a Z-shaped transformer neutral point grounded through an arc suppression coil connected in series with a resistor.

[0085] Using a power distribution network simulation model, single-phase grounding faults with different fault angles, fault resistances, and power distribution lines are set up. Transient information of the faulted lines is collected and principal component analysis is performed. The cumulative proportion y of the principal components in the model is set to 90%, the principal component sample matrix D is determined, the dimension d is 3, and the start threshold w of the line selection device is set to 0.5.

[0086] In one embodiment of the present invention, a single-phase ground fault is set to occur on feeder L5 at a distance of 7 km from the busbar, with a fault angle of 90° and a fault resistance of 200Ω. The zero-sequence voltage gradient and E(k) are calculated according to equations (1) and (2), as follows: Figure 4 As shown, if E(k) is greater than the set value of 0.5, a single-phase ground fault is determined to have occurred, and the line selection device is activated. Transient information after the fault is extracted from each line, and correlation analysis is performed on each line with the principal component sample matrix D to form a correlation matrix M.

[0087]

[0088] The comprehensive line selection matrix ρ = [-0.5251 -0.5263 -0.4978 -0.5420 0.5546 -0.5288] is calculated based on the line selection correlation matrix. The fault line discrimination matrix s = [-1 -1 -1 -1 1 -1] is calculated using the symbolic algorithm. The feeder L5 corresponding to "1" is the faulty feeder.

[0089] In another embodiment of the present invention, a single-phase ground fault is set to occur on feeder L2 at a distance of 5 km from the busbar, with a fault angle of 0° and a fault resistance of 50Ω. The zero-sequence voltage change gradient and E(k) are calculated according to equations (1) and (2), as follows: Figure 5As shown, if E(k) is greater than the set value of 0.5, a single-phase ground fault is determined to have occurred, and the line selection device is activated. Transient information after the fault is extracted from each line, and correlation analysis is performed on each line with the principal component sample matrix D to form a correlation matrix M.

[0090]

[0091] The comprehensive line selection matrix ρ = [-0.5020 0.5585 -5067 -0.4582-0.5002 -0.4948] is calculated based on the line selection correlation matrix. The fault line discrimination matrix s = [-1 1 -1-1 -1-1] is calculated using the symbolic algorithm. The feeder L2 corresponding to "1" is the faulty feeder.

[0092] The distribution network line selection method based on the principal component sample matrix of the faulted line of the present invention is mainly used for the judgment of single-phase grounding fault line selection in low current grounding system. It can also be extended to neutral point ungrounded system and neutral point grounded system through arc suppression coil. The present invention does not make specific limitations on the application scenario.

[0093] The distribution network fault selection method based on the principal component sample matrix of faulted lines provided in this invention uses the zero-sequence voltage change gradient as a criterion for the occurrence of single-phase grounding faults. It utilizes abundant transient information at the onset of a fault to collect transient information samples of faulted lines under different fault conditions, establishing a principal component sample matrix of faulted lines. Through correlation analysis, a final fault selection discrimination matrix is ​​formed to determine the faulted line. When a single-phase grounding fault occurs, the transient information of each line is extracted and correlated with the principal component sample matrix to form a fault selection correlation matrix. The average value of the correlation coefficients of each line is used as the comprehensive correlation matrix for fault selection, and a symbolic algorithm is used to construct the fault selection discrimination matrix to determine the faulted line. By adjusting the start-up threshold and the cumulative proportion setting of the principal components of the fault selection device to adapt to distribution networks with different topologies, the sensitivity of the fault selection device can be effectively improved, exhibiting a certain fault tolerance mechanism and enhancing the reliability of the fault selection results.

[0094] The embodiments of this disclosure have now been described in detail. To avoid obscuring the concept of this disclosure, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0095] While specific embodiments of this disclosure have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this disclosure. The scope of this disclosure is defined by the appended claims.

Claims

1. A fault line-based principal component sample matrix-based method for line selection of a power distribution network, characterized by, include: Collect transient information of faulty lines under different fault conditions to form fault samples; Principal component analysis was performed on the transient information of faulted lines under different fault conditions to construct a principal component sample matrix; Based on the collected zero-sequence voltage, calculate the zero-sequence voltage change gradient; Based on the calculation results of the zero-sequence voltage change gradient, it is determined whether to activate the line selection device. When the gradient is greater than the preset threshold, a single-phase ground fault is determined to have occurred, and the line selection device is activated. Extract transient information after each line fault, and perform correlation analysis on each line with the principal component sample matrix to form a line selection correlation matrix; Calculate the comprehensive route selection matrix based on the route selection correlation matrix; Determine the fault line discrimination matrix based on the comprehensive route selection matrix; The faulty line is determined based on the faulty line discrimination matrix. The process involves extracting transient information after each line fault, performing correlation analysis on each line with the principal component sample matrix, and forming a line selection correlation matrix. Specifically, this includes: Based on the correlation coefficients between the current route and each principal component, the route selection correlation matrix M is constructed as shown below. ; Wherein, m represents the number of system lines, d represents the dimension of principal component sample matrix, i=1, 2, …, m, j=1, 2, …, d, in the selected line correlation matrix M, each row is the correlation coefficient of the line with each principal component, The correlation coefficient of the i-th line with the principal component j, i=1, 2, …, m, j=1, 2, …, d.

2. The fault line based principal component sample matrix based feeder line selection method of claim 1, wherein, The process of performing principal component analysis on transient information of faulted lines under different fault conditions to construct a principal component sample matrix specifically includes: In the process of principal component analysis, the cumulative proportion of principal components is set as y, and the dimension of principal components is determined based on the cumulative proportion of principal components in order to construct the principal component sample matrix D.

3. The fault line based principal component sample matrix based feeder line selection method of claim 1, wherein, The step of calculating the zero-sequence voltage change gradient based on the collected zero-sequence voltage specifically includes: According to the sampling interval, the instantaneous sampling point number and the zero sequence voltage difference between two adjacent sampling points, the zero sequence voltage change gradient is calculated by the following formula , （1） denotes the zero sequence voltage, k denotes the instantaneous sample point number, denotes the sampling interval in ms; Based on the calculation results of the zero-sequence voltage change gradient, the zero-sequence voltage gradient and E(k) are calculated using the following formulas. （2） Where K represents the number of sampling points within a certain time window, and k≥K.

4. The distribution network line selection method based on the principal component sample matrix of faulted lines according to claim 1, characterized in that, The calculation of the comprehensive route selection matrix based on the route selection correlation matrix specifically includes: Based on the route selection correlation matrix, the elements in the comprehensive route selection matrix ρ are calculated using the following formula. , (3)， Where i = 1, 2, ..., m, j = 1, 2, ..., d.

5. The distribution network line selection method based on the principal component sample matrix of faulted lines according to claim 4, characterized in that, The step of determining the fault line discrimination matrix based on the comprehensive route selection matrix specifically includes: Based on the sign of each element in the comprehensive route selection matrix, the fault line discrimination matrix S is determined, and the elements in the fault line discrimination matrix S are calculated using the following formula. , (4) Where i = 1, 2, ..., m.

6. The distribution network line selection method based on the principal component sample matrix of faulted lines according to claim 5, characterized in that, The step of determining the faulty line based on the faulty line discrimination matrix specifically includes: In the fault line discrimination matrix, if all elements are -1, the fault line is determined to be a bus fault; if an element is 1, the fault line is determined to be the feeder corresponding to element 1.

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