CN115144695B - Method, device, equipment and medium for searching fault line of low-current grounding system - Google Patents
Method, device, equipment and medium for searching fault line of low-current grounding system Download PDFInfo
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- CN115144695B CN115144695B CN202210751502.2A CN202210751502A CN115144695B CN 115144695 B CN115144695 B CN 115144695B CN 202210751502 A CN202210751502 A CN 202210751502A CN 115144695 B CN115144695 B CN 115144695B
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Abstract
The application discloses a method, a device, equipment and a medium for searching a fault line of a small-current grounding system, which adopt a transient zero-sequence current true effective value as a characteristic parameter, have high sensitivity, are not influenced by arc suppression coils and unstable arcs, and have high reliability; the Fourier transform centrality of the line diagram is adopted as the basis of discrimination, the line selection accuracy is high, the anti-interference capability of the method is strong, the method is easy to realize, and the application range is wide; the original power system topology is converted into a line graph, node signals and edge weights are reasonably set, and a new line selection method is provided for single-phase grounding faults of the low-current grounding system by utilizing a graph frequency analysis means-graph Fourier transform.
Description
Technical Field
The application belongs to the technical field of power system fault line detection, and particularly relates to a method, a device, equipment and a medium for searching a fault line of a low-current grounding system.
Background
The medium-low voltage distribution network in China usually adopts a low-current grounding system, the distribution network has a complex topological structure and more load nodes, and a single-phase grounding fault is a common fault. After single-phase earth fault occurs, the capacitive fault current is smaller, and the continuous operation is allowed for 1-2 hours, but if the fault is not processed and removed in time, the fault can be further developed into a two-phase or three-phase short circuit, and the normal production life is directly influenced. If intermittent arc grounding occurs at the fault point, series resonance overvoltage can be generated, thereby threatening system insulation and even burning out equipment. Therefore, how to accurately and quickly find out the fault line and quickly cut off the fault has important engineering practice significance and research value for the power system.
The existing line selection algorithm can be divided into three types according to the characteristic types of the extracted signals. The first type is a steady-state component method, which includes: a group ratio amplitude-phase method, a zero sequence active power method, a fifth harmonic method and the like; the second category is transient component methods, which include: a first half-wave method, a characteristic frequency band method, a wavelet analysis method, etc.; the third category is a comprehensive line selection method. Because the distribution network is often interfered by various factors in actual operation, for example: the grounding resistance, the grounding moment voltage phase, the end load, the unbalanced line current, the length of each outgoing line and the like influence the accuracy of the line selection criterion, and erroneous judgment is easy to cause.
Disclosure of Invention
The application aims to provide a method, a device, equipment and a medium for searching a fault line of a low-current grounding system, which are used for solving the problem of misjudgment caused by the interference of various factors on a fault line selection method in the prior art.
In order to achieve the above purpose, the present application adopts the following technical scheme:
the application provides a fault line searching method of a low-current grounding system, which comprises the following steps:
when single-phase earth fault occurs, acquiring zero sequence current sampling data of one cycle of each outgoing line;
based on the zero sequence current sampling data, calculating the true effective value of transient zero sequence current of each outgoing line;
establishing a line graph based on the original topological structure of the power distribution network and the true effective value of the transient zero sequence current of each outgoing line;
based on the line graph definition line graph importance signals, obtaining graph Fourier transform coefficients of all nodes in the line graph by utilizing graph Fourier transform;
calculating the graph Fourier transform centrality of each node based on the graph Fourier transform coefficients of each node;
comparing the centrality of the graph Fourier transform of each node, and selecting the line with the maximum centrality of the graph Fourier transform as the fault line.
As an alternative scheme of the application, in the step of acquiring zero sequence current sampling data of one cycle of each outgoing line after a differential point when the single-phase grounding fault occurs, the method for judging the single-phase grounding fault comprises the following steps: and collecting the zero sequence voltage of the bus, and judging that a single-phase grounding fault occurs when the zero sequence voltage of the bus exceeds a preset threshold value.
As an alternative scheme of the application, in the step of acquiring the zero sequence current sampling data of one cycle of each outgoing line after the abnormal point when the single-phase earth fault occurs, the zero sequence current sampling data of one cycle of each outgoing line after the abnormal point is acquired through the fault zero sequence current recording device.
As an optional scheme of the present application, in the step of calculating the true effective value of the transient zero sequence current of each outgoing line based on the zero sequence current sampling data, the calculation mode of the true effective value of the transient zero sequence current of the mth outgoing line is as follows:
wherein I is 0n Is the nth sampling data of zero sequence current in one cycle of fault, I 0M The true effective value of the transient zero-sequence current of the Mth outlet wire is obtained, and N is the total sampling number of the transient zero-sequence current signals.
As an optional scheme of the present application, the step of creating a line graph based on the original topology structure of the power distribution network and the true effective value of the transient zero sequence current of each outgoing line specifically includes:
the original topological structure of the power distribution network comprises a bus outlet, a turning tower of a circuit, a sectionalizing switch and a circuit tail end, wherein the bus outlet, the turning tower of the circuit, the sectionalizing switch and the circuit tail end are taken as edges, a transient zero-sequence current true effective value is taken as a node signal, transient zero-sequence current true effective value differences of all adjacent nodes are taken as weights of all the edges, and a line graph is built.
As an optional solution of the present application, in the step of defining the line graph importance signal based on the line graph and obtaining the line graph fourier transform coefficients of each node in the line graph by using the line graph fourier transform, an importance signal f of a line graph node n is defined n ＝[f n (1)，f n (2)，...，f n (N)] T Taking as its characteristic the inverse of the cost from a single node to a reference node, where f n (i) Is the inverse of the sum of the weights of the shortest paths from node i to node n.
As an optional aspect of the present application, in the step of calculating the graph fourier transform centrality of each node based on the graph fourier transform coefficient of each node, the graph fourier transform centrality of the node n is calculated by:
in the method, in the process of the application,importance signal corresponding to reference node n, w (lambda l ) Is assigned to the sum frequency lambda l The weights of the corresponding map fourier transform coefficients.
In a second aspect of the present application, there is provided a fault line finding apparatus for a low current grounding system, comprising:
the acquisition module is used for acquiring zero sequence current sampling data of one cycle of each outgoing line after the abnormal point when a single-phase earth fault occurs;
the first calculation module is used for calculating the true effective value of each outgoing line transient zero sequence current based on the zero sequence current sampling data;
the line graph construction module is used for building a line graph based on the original topological structure of the power distribution network and the true effective value of the transient zero sequence current of each outgoing line;
the transformation module is used for defining a line graph importance signal based on the line graph, and obtaining a graph Fourier transformation coefficient of each node in the line graph by utilizing graph Fourier transformation;
the second calculation module is used for calculating the graph Fourier transform centrality of each node based on the graph Fourier transform coefficients of each node;
and the comparison module is used for comparing the centrality of the graph Fourier transform of each node, and selecting the line with the largest centrality of the graph Fourier transform as the fault line.
In a third aspect of the present application, an electronic device is provided, including a processor and a memory, where the processor is configured to execute a computer program stored in the memory to implement the small current grounding system fault line finding method described above.
In a fourth aspect of the present application, a computer readable storage medium is provided, where at least one instruction is stored, where the at least one instruction, when executed by a processor, implements the small current grounding system fault line finding method described above.
The beneficial effects of the application are as follows:
according to the method for searching the fault line of the low-current grounding system, when a single-phase grounding fault occurs, zero-sequence current sampling data of one cycle of each outgoing line after a different action point is obtained; based on the zero sequence current sampling data, calculating the true effective value of transient zero sequence current of each outgoing line; establishing a line graph based on the original topological structure of the power distribution network and the true effective value of transient zero sequence current of each outgoing line; based on the line graph definition line graph importance signals, obtaining graph Fourier transformation coefficients of all nodes in the line graph by utilizing graph Fourier transformation; calculating the graph Fourier transform centrality of each node based on the graph Fourier transform coefficients of each node; comparing the centrality of the graph Fourier transform of each node, and selecting the line with the maximum centrality of the graph Fourier transform as the fault line. The transient zero sequence current true effective value is adopted as a characteristic parameter, so that the sensitivity is high, the transient zero sequence current true effective value is not influenced by an arc suppression coil and an unstable arc, and the reliability is high; the Fourier transform centrality of the line diagram is adopted as the basis of discrimination, the line selection accuracy is high, the anti-interference capability of the method is strong, the method is easy to realize, and the application range is wide; the original power system topology is converted into a line graph, node signals and edge weights are reasonably set, and a new line selection method is provided for single-phase grounding faults of the low-current grounding system by utilizing a graph frequency analysis means-graph Fourier transform.
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The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:
fig. 1 is a flowchart of a fault line searching method of a low-current grounding system according to the present application.
Fig. 2 is a block diagram of a fault line finding device for a low-current grounding system according to the present application.
Fig. 3 is a block diagram of an electronic device according to the present application.
Detailed Description
The application will be described in detail below with reference to the drawings in connection with embodiments. It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other.
The following detailed description is exemplary and is intended to provide further details of the application. Unless defined otherwise, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the application.
Example 1
The application provides a fault line searching method of a low-current grounding system, which is based on line diagram Fourier transform centrality comparison and can be applied to a power system with a plurality of distribution network lines.
As shown in fig. 1, a fault line searching method for a low-current grounding system includes the following steps:
step S1: and acquiring the zero sequence voltage of the bus, and starting fault line selection identification when the zero sequence voltage exceeds a preset threshold value. Specifically, in this step, a threshold value U is preset 0 Set to 0.3U N When the zero sequence voltage of the bus is greater than a preset threshold value, judging that a single-phase grounding fault occurs, and U N Is the line rated voltage.
Step S2: after the single-phase earth fault is judged, the fault zero-sequence current recording device and the like are used for acquiring cycle zero-sequence current sampling data of each outgoing line after the abnormal point.
Step S3: and (3) calculating the true effective value of the transient zero sequence current of each outgoing line based on the zero sequence current sampling data obtained in the step (S3). In the step, the true effective value I of transient zero-sequence current of the Mth outgoing line 0M The calculation method is as follows:
wherein I is 0n Is the nth sampling data of zero sequence current in one cycle of fault, I 0M The true effective value of the transient zero-sequence current of the Mth outlet wire is obtained, and N is the total sampling number of the transient zero-sequence current signals.
Step S4: and establishing a line graph model based on the original topological structure of the power distribution network. Specifically, the original topological structure of the power distribution network comprises a bus outlet, a turning tower of a line, a sectionalizing switch, a line tail end and the like, wherein the bus outlet, the turning tower of the line, the sectionalizing switch and the line tail end are taken as edges, transient zero-sequence current true effective values are taken as node signals, and transient zero-sequence current true effective value differences of all adjacent nodes are taken as weight of all the edges.
It should be noted that, an undirected weighted graph g= { V, E, W }, where V is a set of vertices; e is a collection of edges; w is the adjacency matrix. If two vertexes v i And v j With an edge e therebetween ij ＝(v i ，v j ) Connection is then W ij The weight of this edge is expressed, otherwise W ij ＝0。
Specifically, in the step, an original graph G is constructed according to the original topology of the power system, a bus outlet, a turning tower of a line, a sectionalized switch and a line end are taken as nodes, and a transient zero sequence current true effective value is taken as an edge weight. Line graph L (G) of graph G is a graph in which edges of the original graph G are transformed into vertices, and if there is a common vertex in the graph G for two edges, there is an edge between the transformed vertices in the graph. The line graph shows the interaction of the edges in the original graph, and can reflect the influence condition of the nodes in the original graph within a certain distance.
Step S5: and defining a line graph importance signal based on the constructed line graph, and obtaining a line graph Fourier transform coefficient of each node by utilizing the line graph Fourier transform.
Specifically, in this step, the importance signal f of the line graph node n n ＝[f n (1)，f n (2)，...，f n (N)] T Taking as its characteristic the inverse of the cost from a single node to a reference node, where f n (i) Is the inverse of the sum of the weights of the shortest paths from node i to node n. Normalizing the importance signal so that the sum of the signal values except the reference node n is 1, i.e. Σ i≠n f n (i) =1, in addition the signal value at the reference node n is regarded as a unit value f n (n)＝1。
The significance signal defined above, namely, the significance information is captured in the global smoothness (or change) of the signal, and then the graph Fourier transform coefficients of each node of the graph are calculated by utilizing the graph Fourier transform. The graph fourier transform is a signal processing transformation on the graph topology, analogous to the fourier transform in classical signal processing, providing a way to extract and make apparent in the transform domain the structural properties of the graph signal that are not visible in the vertex domain. In the graph fourier transform, the concept of frequency is derived from the eigen decomposition of the graph laplace matrix, which uses eigenvalues of the graph laplace matrix as the graph frequency, and eigenvectors of the graph laplace matrix are the graph fourier basis.
The graph fourier transform may be defined by an expansion of the graph laplace feature vector ul of the signal:
in the method, in the process of the application,is the Fourier transform of the graph relative to the eigenvalue lambda l Coefficient of->Is u l And (n) complex conjugate.<f 1 ，f 2 >Representing vector f 1 And f 2 Is a product of the inner product of (a).
Step S6: and (5) calculating the graph Fourier transform centrality of each node based on the graph Fourier transform coefficients of each node obtained in the step S5.
It should be noted that the graph fourier transform centrality mentioned in this embodiment is a spectral method for evaluating importance of each node in a complex network, and uses graph fourier transform coefficients of importance signals corresponding to reference nodes.
The graph fourier transform centrality of the nth node is a weighted sum of graph fourier transform coefficients of importance signals corresponding to the node n, and the importance signals of the reference node n are graph signals of individual views of the reference node i given by other nodes in the network according to the lowest cost to the node n, and the graph fourier transform is used for capturing global changes of the importance signals, and is used for defining the graph fourier transform centrality. The graph fourier transform centrality thus utilizes not only local properties, but also global properties of the network topology.
Let the graph Fourier transform centrality of the node n be I n Then:
in the method, in the process of the application,importance signal corresponding to reference node n, w (lambda l ) Is assigned to the sum frequency lambda l The weights of the corresponding map fourier transform coefficients. The weight is selected by a function exponentially increasing the eigenvalue of the Laplace matrix, i.e. ++>Where k > 0. The weights are chosen such that: a larger weight is assigned to the high frequency component of the importance spectrum, a smaller weight is assigned to the frequency component corresponding to the lower frequency, and a zero weight is assigned to the zero frequency component. In this embodiment, k=0.1 is set, and the effect is good.
Step 7: comparing the centrality of the Fourier transform of the graphs of the nodes, and judging the fault line. Specifically, the line having the greatest centrality of the fourier transform of the graph is determined as the faulty line.
It should be noted that, the transient current amplitude generated by the single-phase earth fault of the low-current grounding system is far greater than the steady-state current amplitude, and the main frequency of the transient signal is very high, so that the compensation effect of the arc suppression coil is negligible, the detection sensitivity of the transient signal is very high, and the method is simultaneously applicable to a neutral point ungrounded system and a neutral point through the arc suppression coil grounding system. In the initial stage of fault occurrence, the fault point and the response of the fault branch to the fault are stronger than those of a non-fault line, and the characteristic is shown in the Fourier transform centrality algorithm of the diagram: by calculating the graph Fourier transform centrality measure of each node of the line graph, the graph Fourier transform centrality of the node where the fault branch is located is far higher than that of other nodes in the line graph, and when the ground fault occurs, the node has a larger influence on the local node and also has an influence on the global node. The purpose of selecting the fault line is achieved by comparing and analyzing the central characteristic parameters of the Fourier transform of the graph.
According to the method for searching the fault line of the low-current grounding system, the original topological graph of the power system is utilized and converted into a line graph, the edge weight of the line graph is reasonably set, the importance signal of the line graph node is defined, and the fault line selection of the low-current grounding system is realized by analyzing and calculating the Fourier transform of the line graph and utilizing the centrality evaluation measure of the centrality of the Fourier transform of the line graph; firstly, a line selection diagram model is established, the weight of each side of the diagram is reasonably set, namely, the transient zero sequence current true effective value of each adjacent node is adopted, then the importance of each node corresponding to other nodes is calculated, then the diagram Fourier transform of each node is obtained through a diagram frequency analysis means, and finally the diagram Fourier transform centrality of each node in a diagram network is calculated and analyzed, so that a fault line is selected.
The application improves the single-phase grounding fault line selection condition of the low-current grounding system, and provides a novel fault line selection method, namely a line diagram Fourier transform-based centrality method is adopted. The application converts the original topological structure of the power system into a line graph by utilizing the characteristics that the transient zero-sequence current of the fault transient state is several times larger than the steady-state zero-sequence current, and the transient zero-sequence current flowing through the fault line at any frequency is the sum of transient zero-sequence currents of other non-fault lines, so that the influence condition of fault points on the power distribution network after the fault is more prominent, the importance of each node relative to other nodes is calculated by utilizing the true effective value difference of the transient zero-sequence current of each adjacent node, the transient zero-sequence current is converted into the field of 'graph frequency' through the means of graph Fourier transformation for analysis, and finally, the spectrum method of graph Fourier transformation centrality is introduced, and the method not only utilizes local attributes, but also utilizes the global attribute of network topology, so that the method can be used for evaluating the importance of each node in the fault network. The application is suitable for detection in complex scenes, has high line selection accuracy, strong anti-interference capability, high sensitivity, easy realization and wide application range.
Example 2
As shown in fig. 2, embodiment 2 of the present application provides a fault line finding device for a low-current grounding system, including:
and the acquisition module is used for acquiring zero sequence current sampling data of one cycle of each outgoing line after the abnormal point when the single-phase earth fault occurs.
And the first calculation module is used for calculating the true effective value of the transient zero sequence current of each outgoing line based on the zero sequence current sampling data. The true effective value calculation mode of the transient zero sequence current of the Mth outgoing line is as follows:
wherein I is 0n Is the nth sampling data of zero sequence current in one cycle of fault, I 0M The true effective value of the transient zero-sequence current of the Mth outlet wire is obtained, and N is the total sampling number of the transient zero-sequence current signals.
And the line graph construction module is used for constructing a line graph based on the original topological structure of the power distribution network and the true effective value of the transient zero sequence current of each outgoing line.
And the transformation module is used for defining a line graph importance signal based on the line graph, and obtaining a line graph Fourier transformation coefficient of each node in the line graph by utilizing the line graph Fourier transformation.
And the second calculation module is used for calculating the graph Fourier transform centrality of each node based on the graph Fourier transform coefficients of each node. The graph fourier transform centrality of node n is calculated by:
in the method, in the process of the application,importance signal corresponding to reference node n, w (lambda l ) Is assigned to the sum frequency lambda l The weights of the corresponding map fourier transform coefficients.
And the comparison module is used for comparing the centrality of the graph Fourier transform of each node, and selecting the line with the largest centrality of the graph Fourier transform as the fault line.
Example 3
As shown in fig. 3, the present application also provides an electronic device 100 for implementing the method for finding a fault line of the low current grounding system of embodiment 1; the electronic device 100 comprises a memory 101, at least one processor 102, a computer program 103 stored in the memory 101 and executable on the at least one processor 102, and at least one communication bus 104. Memory 101 may be used to store computer program 103 and processor 102 implements the steps of the low current ground system fault line finding method of embodiment 1 by running or executing the computer program stored in memory 101 and invoking data stored in memory 101. The memory 101 may mainly include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program (such as a sound playing function, an image playing function, etc.) required for at least one function, and the like; the storage data area may store data (such as audio data) created according to the use of the electronic device 100, and the like. In addition, the memory 101 may include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash Card (Flash Card), at least one disk storage device, a Flash memory device, or other non-volatile solid state storage device.
The at least one processor 102 may be a central processing unit (Central Processing Unit, CPU), but may also be other general purpose processors, digital signal processors (Digital Signal Processor, DSP), application specific integrated circuits (Application Specific Integrated Circuit, ASIC), field-programmable gate arrays (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or the like. The processor 102 may be a microprocessor or the processor 102 may be any conventional processor or the like, the processor 102 being a control center of the electronic device 100, the various interfaces and lines being utilized to connect various portions of the overall electronic device 100.
The memory 101 in the electronic device 100 stores a plurality of instructions to implement a low current ground system fault line finding method, the processor 102 may execute the plurality of instructions to implement:
when single-phase earth fault occurs, acquiring zero sequence current sampling data of one cycle of each outgoing line after a differential point;
based on the zero sequence current sampling data, calculating the true effective value of transient zero sequence current of each outgoing line;
establishing a line graph based on the original topological structure of the power distribution network and the true effective value of the transient zero sequence current of each outgoing line;
based on the line graph definition line graph importance signals, obtaining graph Fourier transform coefficients of all nodes in the line graph by utilizing graph Fourier transform;
calculating the graph Fourier transform centrality of each node based on the graph Fourier transform coefficients of each node;
comparing the centrality of the graph Fourier transform of each node, and selecting the line with the maximum centrality of the graph Fourier transform as the fault line.
Example 4
The modules/units integrated with the electronic device 100 may be stored in a computer readable storage medium if implemented in the form of software functional units and sold or used as a stand alone product. Based on such understanding, the present application may implement all or part of the flow of the method of the above embodiment, or may be implemented by a computer program to instruct related hardware, where the computer program may be stored in a computer readable storage medium, and when the computer program is executed by a processor, the steps of each method embodiment described above may be implemented. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, executable files or in some intermediate form, etc. The computer readable medium may include: any entity or device capable of carrying computer program code, a recording medium, a U disk, a removable hard disk, a magnetic disk, an optical disk, a computer Memory, and a Read-Only Memory (ROM).
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present application and not for limiting the same, and although the present application has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the application without departing from the spirit and scope of the application, which is intended to be covered by the claims.
Claims (9)
1. The fault line searching method for the low-current grounding system is characterized by comprising the following steps of:
when single-phase earth fault occurs, acquiring zero sequence current sampling data of one cycle of each outgoing line;
based on the zero sequence current sampling data, calculating the true effective value of transient zero sequence current of each outgoing line;
establishing a line graph based on the original topological structure of the power distribution network and the true effective value of the transient zero sequence current of each outgoing line;
based on the line graph definition line graph importance signals, obtaining graph Fourier transform coefficients of all nodes in the line graph by utilizing graph Fourier transform;
calculating the graph Fourier transform centrality of each node based on the graph Fourier transform coefficients of each node;
the graph fourier transform centrality of node n is calculated by:
in the method, in the process of the application,importance signal corresponding to reference node n, w (lambda l ) Is assigned to the sum frequency lambda l Weights of corresponding graph fourier transform coefficients;
comparing the centrality of the graph Fourier transform of each node, and selecting the line with the maximum centrality of the graph Fourier transform as the fault line.
2. The method for searching fault line of small current grounding system according to claim 1, wherein in the step of obtaining zero sequence current sampling data of one cycle of each outgoing line after a differential point when a single-phase grounding fault occurs, the method for judging the single-phase grounding fault is as follows: and collecting the zero sequence voltage of the bus, and judging that a single-phase grounding fault occurs when the zero sequence voltage of the bus exceeds a preset threshold value.
3. The method for searching the fault line of the low-current grounding system according to claim 1, wherein in the step of acquiring the zero-sequence current sampling data of one cycle of each outgoing line when the single-phase grounding fault occurs, the zero-sequence current sampling data of one cycle of each outgoing line is acquired through a fault zero-sequence current recording device.
4. The method for searching the fault line of the low-current grounding system according to claim 1, wherein in the step of calculating the true effective value of the transient zero-sequence current of each outgoing line based on the zero-sequence current sampling data, the true effective value of the transient zero-sequence current of the mth outgoing line is calculated as follows:
wherein I is 0n Is the nth sampling data of zero sequence current in one cycle of fault, I 0M The true effective value of the transient zero-sequence current of the Mth outlet wire is obtained, and N is the total sampling number of the transient zero-sequence current signals.
5. The method for searching the fault line of the low-current grounding system according to claim 1, wherein the step of creating a line graph based on the original topology structure of the power distribution network and the true effective value of the transient zero-sequence current of each outgoing line specifically comprises the following steps:
the original topological structure of the power distribution network comprises a bus outlet, a turning tower of a circuit, a sectionalizing switch and a circuit tail end, wherein the bus outlet, the turning tower of the circuit, the sectionalizing switch and the circuit tail end are taken as edges, a transient zero-sequence current true effective value is taken as a node signal, transient zero-sequence current true effective value differences of all adjacent nodes are taken as weights of all the edges, and a line graph is built.
6. The method according to claim 1, wherein the step of obtaining the map fourier transform coefficients of each node in the map by using the map fourier transform defines an importance signal f of a map node n based on the map definition map importance signal n ＝[f n (1),f n (2),…,f n (N)] T Characterizing the inverse of the cost from a single node to a reference node, where f n (i) Is the inverse of the sum of the weights of the shortest paths from node i to node n.
7. A low current grounding system fault line finding apparatus, comprising:
the acquisition module is used for acquiring zero sequence current sampling data of one cycle of each outgoing line after the abnormal point when a single-phase earth fault occurs;
the first calculation module is used for calculating the true effective value of each outgoing line transient zero sequence current based on the zero sequence current sampling data;
the line graph construction module is used for building a line graph based on the original topological structure of the power distribution network and the true effective value of the transient zero sequence current of each outgoing line;
the transformation module is used for defining a line graph importance signal based on the line graph, and obtaining a graph Fourier transformation coefficient of each node in the line graph by utilizing graph Fourier transformation;
the second calculation module is used for calculating the graph Fourier transform centrality of each node based on the graph Fourier transform coefficients of each node;
the graph fourier transform centrality of node n is calculated by:
in the method, in the process of the application,importance signal corresponding to reference node n, w (lambda l ) Is assigned to the sum frequency lambda l Weights of corresponding graph fourier transform coefficients;
and the comparison module is used for comparing the centrality of the graph Fourier transform of each node, and selecting the line with the largest centrality of the graph Fourier transform as the fault line.
8. An electronic device comprising a processor and a memory, the processor configured to execute a computer program stored in the memory to implement the low current ground system fault line finding method of any one of claims 1 to 6.
9. A computer readable storage medium storing at least one instruction that when executed by a processor implements the low current ground system fault line finding method of any one of claims 1 to 6.
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