Rapid positioning method for grounding fault of cable branch box

Abstract

The invention discloses a cable branch box grounding fault rapid positioning method, which belongs to the technical field of electrical variable measurement or test, and comprises the following steps: taking each cable branch box in a power distribution system as a node, and establishing a physical connection topology containing a grounding reference point; defining a virtual fault channel for each fault current path between each node and a grounding reference point, and generating a virtual channel network; obtaining a zero-sequence current measurement value of each preset monitoring node, distributing the zero-sequence current measurement value to the virtual channel network, and calculating to obtain a virtual branch current of each virtual fault channel; and performing verification and screening by combining the obtained impedance parameters of each virtual fault channel to obtain a target virtual channel set, mapping the target virtual channel set to a physical connection topology, and determining and outputting a physical position of a fault point. A virtual channel network is adopted to simulate a fault current path and perform dual-mode verification screening, so that rapid, automatic and accurate positioning of a complex power distribution network grounding fault can be realized.

Description

Technical Field

[0001] This invention relates to the field of electrical variable measurement or testing technology, and in particular to a method for rapid location of grounding faults in cable branch boxes. Background Technology

[0002] Cable distribution boxes are key devices in power distribution networks for the branching and switching of cable lines. Rapid and accurate location of grounding faults in these boxes is crucial for ensuring power supply reliability and maintenance safety. Currently, the location of such faults largely relies on the analysis and calculation of electrical measurement signals.

[0003] Existing technical solutions typically involve installing monitoring devices at substation outlets or a few key nodes. These devices measure the zero-sequence current or voltage signals generated by the fault, and then perform single-end or double-end distance measurement in conjunction with line impedance parameters. Another common method is to rely on manual line inspection or injecting specific signals to conduct segment-by-segment checks to determine the specific section where the fault occurred.

[0004] However, existing technical solutions have significant drawbacks. Impedance-based fault location methods heavily rely on accurate line parameters for accuracy, and the uncertainty of these parameters and variations in the transition resistance at the fault point in real-world networks can introduce significant errors. Schemes relying on a single or limited number of monitoring points are ill-suited to the complex multi-branch structures of distribution networks and cannot uniquely determine the actual path of the fault current. Manual line inspection or signal injection methods are time-consuming and labor-intensive, failing to meet the demands for rapid power restoration. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a method for rapid location of grounding faults in cable branch boxes. This method employs a virtual channel network to simulate the fault current path and performs dual-modal verification and screening, enabling rapid, automatic, and accurate location of grounding faults in complex power distribution networks.

[0006] The above objectives can be achieved through the following approach: A method for rapid location of grounding faults in cable branch boxes includes: establishing a physical connection topology with each cable branch box in a power distribution system as a node, including a grounding reference point; defining virtual fault channels for each fault current path between each node and the grounding reference point based on the physical connection topology, generating a virtual channel network; acquiring the zero-sequence current measurement values ​​of each preset monitoring node; allocating the zero-sequence current measurement values ​​of each monitoring node to the virtual channel network, and calculating the virtual branch current of each virtual fault channel; acquiring the impedance parameters of each virtual fault channel, and performing verification and filtering based on the virtual channel network, the virtual branch current, and the zero-sequence current measurement values ​​to obtain a target virtual channel set; mapping the target virtual channel set to the physical connection topology, determining and outputting the physical location of the fault point.

[0007] Optionally, establishing a physical connection topology using each cable branch box in the power distribution system as a node includes: acquiring line connection relationship data and equipment ledger data in the power distribution system; identifying and verifying the electrical connection relationships between each cable branch box based on the line connection relationship data and the equipment ledger data, and generating a connection relationship matrix; determining the grounding reference point in the network according to the connection relationship matrix and preset grounding reference point configuration rules, thereby constructing a physical connection topology.

[0008] Optionally, the step of defining a virtual fault channel for each fault current path from each node to the ground reference point based on the physical connection topology, and generating a virtual channel network, includes: traversing the electrical path from each node to the ground reference point based on the physical connection topology; defining a virtual fault channel for each identified electrical path, and assigning a unique channel identifier to each virtual fault channel; and logically combining all the defined virtual fault channels according to the physical connection relationship to generate a virtual channel network representing all fault current flow paths.

[0009] Optionally, obtaining the zero-sequence current measurement value of each preset monitoring node includes: selecting a cable branch box node that meets preset conditions as a monitoring node; collecting zero-sequence current waveform data of the monitoring node within a preset time window after the fault occurs according to a unified synchronization time reference; and preprocessing the zero-sequence current waveform data of each monitoring point to obtain the zero-sequence current measurement value of each monitoring node.

[0010] Optionally, the step of allocating the zero-sequence current measurement values ​​of each monitoring node to the virtual channel network and calculating the virtual branch current of each virtual fault channel includes: obtaining the dependency relationship between each virtual fault channel and each monitoring node in the virtual channel network, and generating a monitoring node coverage relationship matrix; calculating the initial branch current vector of each virtual fault channel through a current allocation algorithm based on the monitoring node coverage relationship matrix and the zero-sequence current measurement values ​​of each monitoring node; performing topological constraint correction on the initial branch current vector according to the topological mapping relationship between the physical connection topology and the virtual channel network, and generating a correction coefficient vector; and using the correction coefficient vector to perform weighted calculation on the initial branch current vector to obtain and output the virtual branch current of each virtual fault channel.

[0011] Optionally, obtaining the impedance parameters of each virtual fault channel and verifying and filtering them in conjunction with the virtual channel network, the virtual branch current, and the zero-sequence current measurement to obtain the target virtual channel set includes: obtaining the impedance parameters of each virtual fault channel; calculating the fault distance corresponding to each virtual fault channel in conjunction with the virtual channel network and the virtual branch current to generate a fault distance set; performing time-frequency analysis on the transient components in the zero-sequence current measurement to extract transient energy features; mapping the transient energy features to the virtual channel network, analyzing the distribution differences of the same transient energy feature on different virtual fault channels, and generating a channel energy difference vector; and performing dual-mode verification on each virtual fault channel based on the calculation residuals of each fault distance in the fault distance set and the channel energy difference vector to filter out the target virtual channel set.

[0012] Optionally, the step of performing bimodal verification on each virtual fault channel based on the fault distance and channel energy difference vector in the fault distance set to select a target virtual channel set includes: extracting the residual of the fault distance corresponding to each virtual fault channel from the fault distance set to generate a channel residual vector; normalizing the channel energy difference vector to obtain a channel energy difference index vector; weighting the channel residual vector and the channel energy difference index vector of the corresponding virtual fault channel to obtain a confidence score for the corresponding virtual fault channel; and selecting virtual fault channels with confidence scores greater than a preset score threshold to obtain a target virtual channel set.

[0013] Optionally, the step of weighting the channel residual vector and the channel energy difference index vector of the corresponding virtual fault channel to obtain the confidence score of the corresponding virtual fault channel further includes: identifying the current shunting characteristics of the virtual channel network, calculating the shunting interference compensation coefficient, and using the shunting interference compensation coefficient to compensate and adjust the confidence score.

[0014] Optionally, mapping the target virtual channel set to the physical connection topology and determining and outputting the physical location of the fault point includes: sorting the confidence scores in the target virtual channel set from largest to smallest, selecting the virtual fault channel corresponding to the highest confidence score as the primary decision channel; mapping the primary decision channel to the physical connection topology to obtain a line segment sequence; determining the physical location point in the line segment sequence based on the fault distance corresponding to the primary decision channel; cross-validating the physical location point with the virtual fault channels in the target virtual channel set, and outputting the physical location of the fault point based on the validation results.

[0015] Based on the same inventive concept, the present invention also provides a rapid location system for grounding faults in cable branch boxes, the system comprising: The topology building module is used to establish a physical connection topology, including grounding reference points, with each cable branch box in the power distribution system as a node. The channel network generation module is used to define a virtual fault channel for each fault current path between each node and the ground reference point based on the physical connection topology, and generate a virtual channel network. The zero-sequence current acquisition module is used to acquire the zero-sequence current measurement values ​​of each preset monitoring node; The virtual branch current calculation module is used to allocate the zero-sequence current measurement values ​​of each monitoring node to the virtual channel network and calculate the virtual branch current of each virtual fault channel. The target channel filtering module is used to obtain the impedance parameters of each virtual fault channel, and combine them with the virtual channel network, the virtual branch current, and the zero-sequence current measurement value to perform verification and filtering to obtain a set of target virtual channels; The fault location mapping module is used to map the target virtual channel set to the physical connection topology, determine and output the physical location of the fault point.

[0016] Compared with the prior art, the present invention has the following advantages: This invention establishes a virtual fault channel network covering the entire network and uses data from multiple monitoring nodes for collaborative calculation, thereby achieving refined simulation and probability allocation of fault current paths. This enhances the ability to identify grounding fault paths in complex distribution networks and reduces misjudgments caused by complex network structures or limited fault information in traditional methods.

[0017] This invention introduces a dual-mode verification method, combining distance calculation based on impedance parameters with time-frequency analysis based on transient energy, and integrates a shunt interference compensation mechanism. This overcomes the limitations of distance measurement based on a single electrical quantity, which is easily affected by inaccurate line parameters or transition resistance, thereby improving the reliability and accuracy of the positioning results.

[0018] This invention maps fault locations based on physical connection topology and confirms the final location result through cross-validation within the target channel set. It realizes automated conversion and verification from electrical quantity calculation to physical space coordinate output, reduces the workload and uncertainty of manual judgment, and improves the response speed and decision-making efficiency of fault emergency handling.

[0019] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart illustrating a method for rapid location of grounding faults in a cable branch box according to an embodiment of the present invention.

[0022] Figure 2 This is a structural schematic diagram of a cable branch box grounding fault rapid location system according to an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Reference Figure 1 One embodiment of the present invention proposes a method for rapid location of grounding faults in cable branch boxes. The method uses a virtual channel network to simulate the fault current path and performs dual-modal verification and screening, which can achieve rapid, automatic and accurate location of grounding faults in complex distribution networks.

[0025] The method described in this embodiment specifically includes: S1. Establish a physical connection topology that includes grounding reference points, with each cable branch box in the power distribution system as a node; Optionally, establishing a physical connection topology using each cable branch box in the power distribution system as a node includes: Obtain data on line connections and equipment ledgers in the power distribution system; Based on the line connection data and the equipment ledger data, the electrical connection relationships between each cable branch box are identified and verified, and a connection relationship matrix is ​​generated. Based on the connection relationship matrix and the preset grounding reference point configuration rules, the grounding reference points in the network are determined, thereby constructing the physical connection topology.

[0026] In one embodiment of the present invention, step S1 includes the following steps: Specifically, this process begins with acquiring two types of data from a power distribution automation system or a geographic information system. The first is line connection data, which records the starting and ending equipment numbers of primary equipment such as cables and overhead lines, forming physical connection links. The second is equipment ledger data, which includes the equipment number, physical coordinates, electrical parameters, and preset operating status indicators of cable branch boxes. Based on the established criteria integrated from no fewer than 200 sets of power distribution network design drawings and historical inspection reports, the line connection data and equipment ledger data together form the foundation of network modeling.

[0027] Using the equipment number as a unique key, the system associates and verifies the two types of data mentioned above. The system identifies the starting and ending equipment numbers of each line segment and searches for the corresponding equipment type in the equipment ledger. If both the starting and ending equipment are cable branch boxes, a direct electrical connection is determined between these two cable branch box nodes. The system traverses all line records, recording all identified direct electrical connections in a list, with each item containing a pair of connection nodes. To ensure topology accuracy, the system performs verification, such as checking for isolated nodes or unexpected closed loops. Based on this, a relationship matrix is ​​generated to characterize the connection status between cable branch boxes in the entire power distribution system; this matrix is ​​called the connection relationship matrix. It is The square array, in which This represents the total number of cable branch box nodes. Matrix elements. The definition is as follows: , in, Represents the connection matrix; Represents the first in the matrix Line number The elements of the column take the value of a Boolean value, where 1 represents a connection and 0 represents no connection. and They represent the first The and the first Each cable branch box node is set based on the unique equipment number in the equipment ledger.

[0028] Based on the connection matrix and preset grounding reference point configuration rules, grounding reference points in the network are determined. The grounding reference point configuration rules are set so that, in the topology described by the connection matrix, cable branch box nodes directly connected to the substation grounding busbar or directly grounded through a grounding electrode with negligible impedance are marked as grounding reference points. These rules are based on the power distribution system grounding design specifications. The system automatically determines and generates a set of grounding reference points by querying the electrical parameters and operating status identifiers of nodes in the equipment ledger data. Ultimately, this is achieved by integrating the node set. Connection matrix and grounding reference point set A complete physical connection topology is constructed, which is stored in a graph data structure, with nodes representing cable branch boxes, edges representing electrical connections, and grounding reference points clearly marked.

[0029] For example, suppose a power distribution system contains 5 cable branch boxes, with node numbers as follows: to The obtained line connection relationship data shows that the connection pairs are... , , , Equipment ledger data indicating nodes. Directly connect to the substation grounding busbar. After identification and verification, confirm that all connections are valid and there are no isolated nodes. Generate a connection relationship matrix. It is a 5th order square matrix, in which , , , All other elements are 0. According to the grounding reference point configuration rules, the node... It was determined to be the grounding reference point, therefore the set The resulting physical connection topology is a network based on... For the beginning, It is a chain network structure at the grounding end.

[0030] S2. Based on the physical connection topology, define a virtual fault channel for each fault current path between each node and the grounding reference point, and generate a virtual channel network. Optionally, the step of defining a virtual fault channel for each fault current path between each node and the ground reference point based on the physical connection topology, and generating a virtual channel network, includes: Based on the physical connection topology, traverse the electrical path from each node to the ground reference point; Define a virtual fault channel for each identified electrical path and assign a unique channel identifier to each virtual fault channel; All defined virtual fault channels are logically combined according to their physical connections to generate a virtual channel network that represents all fault current flow paths.

[0031] In one embodiment of the present invention, step S2 includes the following steps: Specifically, the input for this step is the physical connection topology constructed in step S1. This topology is in graph structure. It means that among them Represents the set of all cable branch box nodes. Represents a matrix based on connection relationships A defined set of edges between nodes. This represents the set of grounding reference points.

[0032] The implementation process begins with systematically accessing every node in the physical connection topology. For each non-grounded reference point node in the topology... The algorithm needs to find the path from this node to any ground reference point. All possible electrical paths. An electrical path is defined as a sequence of nodes that are directly connected by edges in sequence. Furthermore, the sequence contains no duplicate nodes, ensuring that the path is acyclic. The traversal process employs a depth-first search algorithm, starting with the node... Starting with a set Using any node in the matrix as the search endpoint, the connection matrix is ​​used. The connectivity between nodes is determined to guide the search direction. This traversal method is based on the classic algorithm in graph theory for finding all simple paths between two points, aiming to exhaustively list all physical channels through which fault current may flow.

[0033] Each identified slave node to ground reference point For each electrical path, a virtual fault path is defined. A virtual fault path is a logical abstraction and unique representation of that specific physical electrical path. The system assigns a unique path identifier to this newly defined virtual fault path. The generation rule for this identifier is based on the starting node number, the ending ground reference point number, and the path sequence number within the same pair of nodes, for example, in the format: .in It is the channel identifier, subscript Represents the starting node index. Represents the endpoint grounding reference point index. Represents the node to ground reference point The Each path. The allocation of unique identifiers is based on database index design principles to ensure that each logical path can be retrieved and referenced unambiguously in subsequent processing.

[0034] After traversing all nodes and defining and identifying all virtual fault channels, the logical combination phase begins. This phase organizes all defined virtual fault channels according to their corresponding physical electrical paths within the original physical connection topology. Specifically, if two virtual fault channels share some identical physical node sequences, they are recorded as intersecting at these nodes in the logical network. The final result is a logical network structure covering the entire network and representing all possible fault current flow paths, called the virtual channel network. This network can be formally represented as follows: ,in It is a collection of all virtual fault channels. It represents the set of logical relationships between channels based on shared nodes in the physical topology. The construction of the virtual channel network is based on network theory, transforming the physical topology into a logical view for fault analysis, with current paths as the basic units.

[0035] For example, the chain-like physical connection topology constructed in the example of step S1 is used, which includes nodes to ,in This is the grounding reference point. The system is connected to node... Begin the traversal to find the ground reference point. The electrical path. Due to the chain topology, from arrive There exists one and only one path. Define a virtual fault channel for this path and assign a unique channel identifier, for example... Then traverse the nodes. Found Da path Define channel Similarly, for nodes... Get the path and passage , for nodes Get the path and passage .node As a grounding reference point, it does not initiate traversal towards itself. Ultimately, the system will define four virtual fault channels. , , , Logical combination is performed. Since the physical paths of these channels are topologically connected and share intermediate nodes, they logically constitute a complete virtual channel network extending from the far end of the network to the grounding point.

[0036] S3. Obtain the zero-sequence current measurement value of each preset monitoring node; Optionally, obtaining the zero-sequence current measurement values ​​of each preset monitoring node includes: Select cable branch box nodes that meet the preset conditions as monitoring nodes; According to a unified synchronization time reference, zero-sequence current waveform data of the monitoring node is collected within a preset time window after the fault occurs. The zero-sequence current waveform data at each monitoring point are preprocessed to obtain the zero-sequence current measurement value at each monitoring node.

[0037] In one embodiment of the present invention, step S3 includes the following steps: Specifically, this step aims to acquire current data for fault analysis, with the physical connection topology established in step S1 as input. The implementation process begins with the selection of monitoring nodes. Monitoring nodes refer to cable branch boxes equipped with zero-sequence current transformers and capable of data uploading. The selection criteria are based on the physical connection topology and equipment importance, typically prioritizing cable branch boxes located at the intersection of network backbone lines, far from the grounding reference point, or historically prone to faults. A quantitative selection formula based on network topology centrality can be expressed as: , when At that time, node Selected as monitoring nodes. Represents a node Monitoring priority score; Represents a node The degree in the physical connection topology, that is, the number of nodes directly connected to it; This represents the maximum degree of all nodes, used for normalization. Represents a node To the nearest ground reference point set The shortest path hop count; This represents the maximum number of hops along the shortest path from all nodes to the nearest ground reference point, used for normalization. and For the weighting coefficients, satisfying The settings are based on the emphasis placed on network connectivity and electrical distance; This is a preset selected threshold. The formula is based on the common principle of optimizing the layout of monitoring points in power distribution automation systems, aiming to cover the maximum fault information flow with the fewest monitoring points.

[0038] After selecting monitoring nodes, the system enters the data acquisition phase. To ensure time comparability of current data acquired by different monitoring nodes, a unified synchronization time reference must be used. This is achieved by configuring a clock synchronization module based on a satellite navigation system or IRIG-B code for each monitoring node's data acquisition unit. When a ground fault occurs in the power distribution system, a fault recording start signal or an overcurrent start signal triggers each monitoring node to begin acquisition. The system acquires data for a preset time window after the fault occurs. Zero-sequence current waveform data within the time window. The setting is based on the typical duration of the transient process of a ground fault, usually covering 1 to 5 power frequency cycles after the fault occurs. For example, setting... Sampling frequency Based on the Nyquist sampling theorem and the highest harmonic frequency that needs to be considered in zero-sequence current, for example, setting... Therefore, each monitoring node What was collected was a discrete sequence of instantaneous zero-sequence current values. ,in , This represents the total number of sampling points.

[0039] Finally, the raw waveform data is preprocessed to obtain the zero-sequence current measurement value that can be used for calculation. The preprocessing includes two main operations: first, digital filtering to eliminate DC offset and suppress high-frequency noise, implemented using a fourth-order Butterworth low-pass filter with a cutoff frequency of 500Hz; second, extracting characteristic quantities representing the magnitude of the fault current from the filtered waveform. Zero-sequence current measurement value. The root mean square value of the filtered waveform over a complete power frequency cycle is obtained by calculating the root mean square value of the filtered waveform. The calculation formula is as follows: , in, Indicates monitoring node The zero-sequence current measurement, in amperes; This represents the zero-sequence current discrete sequence after filtering. This represents the number of sampling points within one power frequency cycle. , The system power frequency is used. This calculation method is based on the standard definition of AC current in electrical engineering, ensuring that the measured values ​​stably reflect the effective level of zero-sequence current during a fault. After preprocessing, the set of zero-sequence current measurements corresponding to all monitoring nodes is output. ,in This represents the total number of monitoring nodes.

[0040] For example, using the aforementioned physical connection topology, including nodes to And it is known This is the grounding reference point. Based on the selected rules, and set... , , The calculated nodes (High connectivity) and nodes (Farthest from the grounding point) The value exceeds the threshold, therefore selected. and For monitoring nodes, denoted as and The system uses GPS clock synchronization and sets a time window after a fault. sampling frequency When a fault occurs, the monitoring node and Synchronous startup resulted in the acquisition of 1000 raw zero-sequence current waveform sequences from each sample. Both sequences were then low-pass filtered to remove noise above 500Hz. The first complete 20ms period of data from the filtered sequence was then selected (corresponding to...). (Points), each substituted into the root mean square formula. Assume the calculated values ​​are... , The final set of zero-sequence current measurements output is then: Unit ampere.

[0041] S4. Allocate the zero-sequence current measurement values ​​of each monitoring node to the virtual channel network, and calculate the virtual branch current of each virtual fault channel; Optionally, the step of allocating the zero-sequence current measurement values ​​of each monitoring node to the virtual channel network and calculating the virtual branch current of each virtual fault channel includes: Obtain the hierarchical relationship between each virtual fault channel and each monitoring node in the virtual channel network, and generate a monitoring node coverage relationship matrix; Based on the monitoring node coverage relationship matrix and the zero-sequence current measurement value of each monitoring node, the initial branch current vector of each virtual fault channel is calculated by the current allocation algorithm. Based on the topology mapping relationship between the physical connection topology and the virtual channel network, the initial branch current vector is corrected by topology constraints to generate a correction coefficient vector; The initial branch current vector is weighted using the correction coefficient vector to obtain and output the virtual branch current of each virtual fault channel.

[0042] In one embodiment of the present invention, step S4 includes the following steps: Specifically, the inputs to this step include the virtual channel network generated in step S2 and the zero-sequence current measurement values ​​of each monitoring node obtained in step S3. Its core task is to reasonably decompose the measured total zero-sequence current of the node into the potential fault paths that constitute the current source of that node, i.e., the virtual fault channels.

[0043] The implementation process begins with analyzing the dependency relationships between each virtual fault channel and each monitoring node in the virtual channel network. Here, dependency means that if a monitoring node is located on the physical path of a virtual fault channel, then that monitoring node covers that channel, implying that the fault current of that channel will flow through this monitoring node and be measured. Based on the node path sequence of each channel recorded in the virtual channel network, the system traverses all channels and all monitoring nodes, generating a binary matrix called the monitoring node coverage matrix. The matrix has dimensions of ,in This represents the total number of virtual fault channels. Total number of monitoring nodes. Matrix elements. The definition is as follows: , in, This represents the coverage relationship matrix of monitoring nodes; Represents the first in the matrix Line number Column elements; Indicates the first One virtual fault channel; Indicates the first There are 10 monitoring nodes. This matrix is ​​based on a logical model of the relationship between the fault current flow path and the measurement point location.

[0044] Based on the monitoring node coverage matrix and the zero-sequence current measurements of each monitoring node, an initial branch current vector is calculated using a current allocation algorithm. This algorithm treats the total zero-sequence current measured by each monitoring node as the sum of the currents flowing through all virtual fault channels covered by that node. This constitutes a system of linear equations: .in, It is pending. The initial branch current vector, whose elements Corresponding channel The initial distribution current; yes A vector of zero-sequence current measurements, with elements of . ; This is the transpose of the monitoring node coverage relationship matrix. Because the number of channels is typically... Greater than the number of monitoring nodes The system of equations is underdetermined. The current distribution algorithm uses the least squares method to find the solution that minimizes the overall fitting error with the measured values. The calculation expression is: , in, This represents the initial branch current vector, in amperes; This represents the vector of zero-sequence current measurements, in amperes. It is defined based on linear least squares estimation in optimization theory, aiming to obtain the best-fit solution for the measurement data without additional constraints.

[0045] Next, based on the topology mapping relationship between the physical connection topology and the virtual channel network, the initial branch current vector is corrected according to topology constraints. The physical connection topology describes the actual connections between nodes, while virtual fault channels may share path segments. The goal of the correction is to make the current distribution ratio between adjacent channels or channels with a common upstream node more consistent with the impedance-based current distribution law in the actual power grid. The system first calculates a weight matrix reflecting the electrical proximity relationship between channels based on the physical topology and channel paths. Then, a correction coefficient vector is calculated using this matrix and the initial solution. One method for calculating the correction coefficient based on the neighborhood current smoothing assumption is as follows: , in, Indicates channel The correction factor is a dimensionless number; This is a preset small positive correction strength coefficient, typically set between 0.05 and 0.2 based on typical mesh simulation results; Indicates the relationship between channels in physical topology The set of other channels with the highest correlation; It is a weight matrix Middle characterization channel With channel The element representing the association strength is calculated based on the path overlap length; This is the average value of the initial branch current vector. This correction makes the current distribution smoother.

[0046] Finally, the initial branch current vector is weighted element-wise using the correction coefficient vector to obtain and output the virtual branch current of each virtual fault channel. The calculation formula is as follows: , in, Indicates virtual fault channel The final virtual branch current is expressed in amperes. This step ensures that the current distribution conforms to both the measured data and the fundamental constraints derived from the physical topology.

[0047] For example, continuing with the previous example, there are four virtual channels. (correspond ), ( ), ( ), ( ); Monitoring nodes are ( )and ( ), its measured value , Based on the path, monitor the nodes. Located only in the passage superior, Located in the passage and Above. Therefore, the monitoring node coverage relationship matrix for: , The row order corresponds to the channel. The column order corresponds to the monitoring node. Zero-sequence current measurement vector Substitute the values ​​into the least squares formula to calculate the initial branch current vector. Matrix operations can be used to obtain... , , , . Notice Negative values ​​may physically correspond to the direction of current, but topological constraint corrections are required. Based on the chain topology, the channel... and The correlation is close. Let the modified strength coefficient be... Calculate the correction factor , , The virtual branch current is finally obtained: , , , .

[0048] S5. Obtain the impedance parameters of each virtual fault channel, and combine them with the virtual channel network, the virtual branch current, and the zero-sequence current measurement value to perform verification and screening to obtain the target virtual channel set; Optionally, the step of obtaining the impedance parameters of each virtual fault channel, and combining them with the virtual channel network, the virtual branch current, and the zero-sequence current measurement value to perform verification and filtering to obtain the target virtual channel set includes: Obtain the impedance parameters of each virtual fault channel, and combine them with the virtual channel network and the virtual branch current to calculate the fault distance corresponding to each virtual fault channel and generate a fault distance set. Specifically, the inputs to this step include the virtual channel network generated in step S2, the virtual branch currents of each virtual fault channel calculated in step S4, and the raw waveform data from the zero-sequence current measurements obtained in step S3. Its core task is to verify and filter the virtual fault channels using two independent fault characteristic modes to form a highly reliable target set.

[0049] The implementation process first requires obtaining the impedance parameters of each virtual fault channel. These impedance parameters include the zero-sequence resistance per unit length of the channel. and zero-sequence reactance These parameters are derived from cable model manuals or line parameter libraries fitted based on historical fault data. The impedance parameter of each channel is obtained by weighted summation based on the line type and length it traverses. This is combined with the starting position of each channel in the virtual channel network and the virtual branch current. and zero-sequence current measurement vector It can calculate the distance to the fault. For each virtual fault channel... Assuming the fault point is located on this channel, and the measurement point is the starting node of this channel, then the fault distance... It can be obtained by solving the voltage balance equation. The calculation formula can be: , in, The zero-sequence voltage of the system, calculated at the instant of the fault, can be measured by the voltage transformer at the monitoring point or estimated based on system parameters. This represents the virtual branch current of the channel, in amperes. This is the zero-sequence impedance modulus per unit length of the channel, in ohms per kilometer. This is the calculated fault distance, expressed in kilometers. Calculating the fault distance for all channels generates a set of fault distances. .

[0050] Time-frequency analysis is performed on the transient component in the zero-sequence current measurement to extract transient energy characteristics; Specifically, the system performs time-frequency analysis on the transient components in the zero-sequence current measurement in parallel to extract transient energy characteristics. This process begins with the raw zero-sequence current waveform data acquired in step S3. In the process, a high-pass digital filter is used to separate the transient component. Subsequently, regarding Perform wavelet transform to select a specific frequency band (e.g., 5kHz to 10kHz) that reflects the high-frequency characteristics of the initial stage of the fault. Transient energy characteristics. It is obtained by calculating the sum of squares of the wavelet coefficients in that frequency band within the first 1-millisecond time window after the fault: , in, Indicates monitoring node The transient energy characteristics are expressed in square amperes. Indicates monitoring nodes The transient current obtained by wavelet transform at frequency and time The coefficient at the location; Indicates the selected set of high-frequency bands; Indicates the sampling point corresponding to the fault initiation time; This represents the number of sampling points within a 1-millisecond time window. The calculation method is based on the correlation between the high-frequency signal energy and the distance to the fault point during the fault transient process.

[0051] The transient energy feature is mapped to the virtual channel network, and the distribution differences of the same transient energy feature on different virtual fault channels are analyzed to generate a channel energy difference vector. Specifically, the extracted transient energy features are mapped to a virtual channel network. Because transient energy features attenuate as they propagate through the network, the same feature will have different observed values ​​at monitoring nodes at different locations. The system analyzes the distribution differences of transient energy features generated by the same fault event across different virtual fault channels. For each virtual fault channel... Calculate a value representing the difference between the energy observations of each monitoring node along the channel path and the theoretical attenuation model. Generate channel energy difference vector One calculation method is based on the path loss model: , in, It is a monitoring node Actual observed transient energy characteristics; Based on the assumption that the fault point is located in the channel upper distance from the starting point At the node, the result is calculated based on the high-frequency signal attenuation model. The theoretical energy value. The smaller the value, the better the channel matches the actual transient energy distribution.

[0052] Based on the calculated residuals of each fault distance in the fault distance set and the channel energy difference vector, a dual-modal verification is performed on each virtual fault channel to filter out the target virtual channel set.

[0053] Optionally, the step of performing dual-modal verification on each virtual fault channel based on the difference vector between each fault distance in the fault distance set and the channel energy, and filtering out the target virtual channel set, includes: Extract the residuals of the fault distances corresponding to each virtual fault channel from the fault distance set, and generate a channel residual vector; The channel energy difference vector is normalized to obtain the channel energy difference index vector. The confidence score of the corresponding virtual fault channel is obtained by weighting the channel residual vector and the channel energy difference index vector. The set of target virtual channels is obtained by filtering out virtual fault channels whose confidence scores are greater than a preset score threshold.

[0054] Optionally, the step of weighting the channel residual vector and the channel energy difference index vector of the corresponding virtual fault channel to obtain the confidence score of the corresponding virtual fault channel further includes: Identify the current shunting characteristics of the virtual channel network and calculate the shunting interference compensation coefficient; The confidence score is adjusted by using the shunt interference compensation coefficient.

[0055] Specifically, bimodal verification is performed on each virtual fault channel based on the calculated residuals of each fault distance in the fault distance set and the channel energy difference vector. This includes extracting residuals from the fault distance set. Since the actual fault distance should be within the channel length range, the channel residual is defined. To calculate the distance to the fault Relative to channel length Normalized absolute bias: , in, Indicates channel The residual is a dimensionless number; Indicates channel The total length. The residuals of all channels are combined into a channel residual vector. Simultaneously, the channel energy difference vector... After normalization, the channel energy difference index vector is obtained. Its elements .

[0056] The core of dual-modal verification is to fuse the channel residual and channel energy difference index of the corresponding virtual fault channel to obtain a confidence score. For this purpose, a shunt interference compensation coefficient is introduced. This coefficient is used to compensate for verification errors caused by current shunting in the virtual channel network, and is calculated by identifying the current shunting characteristics of the virtual channel network. Specifically, for the channel... Its shunt interference compensation coefficient Defined as the virtual branch current of this channel The ratio of this ratio to the sum of the zero-sequence current measurements at all monitoring nodes along its path, after being processed by a saturation function, makes... Between 0 and 1: , in, This is a hyperbolic tangent function used to map the ratio to the (0,1) interval. The rationale behind this setting is that the larger the shunting ratio, the higher the likelihood that the channel will become the primary fault path, and its verification result should receive a higher compensation weight.

[0057] Finally, confidence score The weighted calculation yielded the following: , in, Indicates virtual fault channel The confidence score is a dimensionless number ranging from 0 to 1; The preset weighting coefficient is used to balance the contributions of the distance residual mode and the energy difference mode, and is usually set between 0.5 and 0.7 based on a large number of simulation experiments; This is the shunt interference compensation coefficient. The formula has consistent dimensions; all terms are dimensionless numbers. After calculating the confidence scores for all channels, those with scores greater than a preset score threshold are selected. The virtual fault channels constitute the target virtual channel set. Threshold The setting is based on the score distribution of the correct and incorrect channels in historical failure cases, and can be set to 0.6 for example.

[0058] For example, continuing with the previous example, there are four virtual fault channels. Their virtual branch currents are respectively , , , The lengths of each channel are known. , , , Zero-sequence impedance per unit length Estimate zero-sequence voltage Substitute the values ​​into the fault distance formula to calculate: This value far exceeds the channel length, residual The distance is significant; similar calculations are used for other channel distances. In practice, since the example current values ​​are derived from the assignment rather than actual faults, the distance calculation is only for demonstration purposes. It is assumed that the channel residual vector is obtained through calculation and transient energy analysis. Channel energy difference index vector Let the weights be... Calculate the shunt interference compensation coefficient: For the channel Its path covers monitoring nodes and The sum of currents is ,but Similarly, calculate the coefficients for other channels. Substitute them into the confidence score formula, for example, for channel... : Assuming that the score is obtained after calculating all channels. Set a threshold Then only the channel Selected to enter the target virtual channel set .

[0059] S6. Map the target virtual channel set to the physical connection topology, determine and output the physical location of the fault point.

[0060] Optionally, mapping the target virtual channel set to the physical connection topology and determining and outputting the physical location of the fault point includes: Sort the confidence scores in the target virtual channel set from largest to smallest, and select the virtual fault channel corresponding to the first confidence score as the main judgment channel; The main decision channel is mapped to the physical connection topology to obtain the line segment sequence; Based on the fault distance corresponding to the main determination channel, determine the physical location point in the line segment sequence; The physical location point is cross-validated with the virtual fault channels in the target virtual channel set, and the physical location of the fault point is output based on the validation results.

[0061] In one embodiment of the present invention, step S6 includes the following steps: Specifically, the inputs to this step are the target virtual channel set output from step S5 and the physical connection topology constructed in step S1. The ultimate goal is to output a definite, physically locatable fault location.

[0062] The implementation process begins by sorting the virtual fault channels in the target virtual channel set. The system reads the confidence score calculated in step S5 for each virtual fault channel in the set and sorts them in descending order of score value. The virtual fault channel that ranks first after sorting is selected as the primary decision channel. The primary decision channel represents the potential fault path with the highest overall confidence in the dual-modal verification.

[0063] The mapping operation is based on the node path sequence recorded when the virtual fault channel is defined. The system reads the unique channel identifier of the main decision channel and parses the sequence of all cable branch box nodes traversed from the starting node to the grounding reference point from its stored information. This node sequence directly corresponds to a series of continuously connected line segments in the physical connection topology, thus obtaining the line segment sequence. For example, the node sequence of a channel is... Then its corresponding line segment sequence is the connection. , , The set consisting of three physical segments in sequence.

[0064] Based on the fault distance corresponding to the main judgment channel, the specific physical location point is determined in the above line segment sequence. Fault distance Calculated in step S5. The system first obtains the actual length of each segment in the line segment sequence. Starting from the beginning of the first segment of the sequence, accumulate the segment lengths. When the sum of the accumulated lengths reaches... First time greater than or equal to the fault distance At that time, it can be determined that the fault point is located at the first... On a segment. Precise location within that segment. It can be determined by linear interpolation: , in, Indicates the final determined physical location coordinates of the fault point; and They represent the first The physical coordinates of the start and end points of each line section can be obtained from the equipment ledger data; This represents the sum of the lengths of all segments preceding the segment where the fault point is located; Indicates the location of the fault point. The length of each segment. This formula is essentially a proportional scaling, with consistent dimensions; both the numerator and denominator are units of length. The final result... It has the same dimensions as the coordinate system.

[0065] The system will use the above-mentioned initially determined physical location points Verification is performed against other virtual fault channels in the target virtual channel set, excluding the primary decision channel. The verification logic is: if a fault actually occurs, the fault location indicated by other high-confidence channels should be spatially consistent with or close to the location indicated by the primary decision channel. For each other channel in the target set... The system calculates the indicated fault location. (Utilizing its own fault distance and path mapping) and Euclidean distance between Confidence scores based on these distances and corresponding channels. Calculate the overall consistency verification factor. : , in, The consensus factor for cross-validation is a dimensionless number ranging from 0 to 1. It is a distance attenuation coefficient used to control the degree of influence of distance difference on consistency. It is usually set according to the average length of the power distribution network line, for example, 1 kilometer. This represents the natural exponential function. This formula assigns greater weight to channels with higher confidence scores, and their contribution increases the closer they are to the principal decision position. If... Below the preset verification threshold (For example, 0.3), then an alarm will be triggered, indicating that the location result may be ambiguous or requires manual review; if If the value is above the threshold, the verification passes.

[0066] The system outputs the physical location of the fault point based on the results of cross-validation. When validation passes, the location is output directly. This indicates the physical location of the identified fault point. When verification fails, the output is... At the same time, a low-confidence flag is attached, and the possible location ranges mapped from all channels in the target virtual channel set can be output together for operation and maintenance personnel to refer to.

[0067] For example, following the example result from step S5, the target virtual channel set Includes only one virtual fault channel The system directly identifies it as the primary decision channel. (Assuming channel...) The node path sequence is The resulting sequence of line segments obtained by mapping is: , , Three physical segments. Assume step S5 calculates the channel... Fault distance The lengths of the three segments are given as follows: , , Cumulative calculation: The first section adds 1.2km, which is less than 1.8km; adding the second section, the cumulative distance is 2.2km, which is greater than 1.8km. Therefore, the fault point is determined to be in the second section. Up. The starting point of this section. coordinate ,end coordinate Substitute into the positioning formula to calculate: Since there are no other channels in the target set for cross-validation, the system can be configured to default to successful validation in this case, or output a single-channel judgment prompt. Finally, the system outputs the physical location coordinates of the fault point. .

[0068] Based on the same inventive concept, such as Figure 2 As shown, the present invention also provides a rapid location system for grounding faults in cable branch boxes, the system comprising: The topology building module is used to establish a physical connection topology, including grounding reference points, with each cable branch box in the power distribution system as a node. The channel network generation module is used to define a virtual fault channel for each fault current path between each node and the ground reference point based on the physical connection topology, and generate a virtual channel network. The zero-sequence current acquisition module is used to acquire the zero-sequence current measurement values ​​of each preset monitoring node; The virtual branch current calculation module is used to allocate the zero-sequence current measurement values ​​of each monitoring node to the virtual channel network and calculate the virtual branch current of each virtual fault channel. The target channel filtering module is used to obtain the impedance parameters of each virtual fault channel, and combine them with the virtual channel network, the virtual branch current, and the zero-sequence current measurement value to perform verification and filtering to obtain a set of target virtual channels; The fault location mapping module is used to map the target virtual channel set to the physical connection topology, determine and output the physical location of the fault point.

[0069] It should be noted that the electrical connections between the various units described above do not necessarily represent direct or indirect connections. Any method of indirect connection is applicable to the embodiments of the present invention as long as it achieves the purpose of the present invention. The above descriptions are merely exemplary embodiments of the present invention and should not be construed as limiting the scope of the present invention.

[0070] All equivalent changes and modifications made in accordance with the teachings of this invention are still within the scope of this invention. Those skilled in the art will readily conceive of other embodiments of this invention upon considering the specification and the disclosure of practical truth. This application is intended to cover any variations, uses, or adaptations of this invention that follow the general principles of this invention and include common knowledge or conventional techniques in the art not described herein.

Claims

1. A method for rapid location of grounding faults in cable branch boxes, characterized in that, The method includes: A physical connection topology, including grounding reference points, is established using each cable branch box in the power distribution system as a node. Based on the physical connection topology, a virtual fault channel is defined for each fault current path between each node and the grounding reference point, generating a virtual channel network. Obtain the zero-sequence current measurement values ​​of each preset monitoring node; The zero-sequence current measurement values ​​of each monitoring node are allocated to the virtual channel network, and the virtual branch current of each virtual fault channel is calculated. The impedance parameters of each virtual fault channel are obtained, and the target virtual channel set is obtained by combining the virtual channel network, the virtual branch current, and the zero-sequence current measurement value. The target virtual channel set is mapped to the physical connection topology to determine and output the physical location of the fault point.

2. The method for rapid location of grounding faults in a cable branch box according to claim 1, characterized in that, The establishment of a physical connection topology using each cable branch box in the power distribution system as a node includes: Obtain data on line connections and equipment ledgers in the power distribution system; Based on the line connection data and the equipment ledger data, the electrical connection relationships between each cable branch box are identified and verified, and a connection relationship matrix is ​​generated. Based on the connection relationship matrix and the preset grounding reference point configuration rules, the grounding reference points in the network are determined, thereby constructing the physical connection topology.

3. The method for rapid location of grounding faults in a cable branch box according to claim 2, characterized in that, Based on the physical connection topology, defining a virtual fault channel for each fault current path between each node and the ground reference point, and generating a virtual channel network includes: Based on the physical connection topology, traverse the electrical path from each node to the ground reference point; Define a virtual fault channel for each identified electrical path and assign a unique channel identifier to each virtual fault channel; All defined virtual fault channels are logically combined according to their physical connections to generate a virtual channel network that represents all fault current flow paths.

4. The method for rapid location of grounding faults in a cable branch box according to claim 3, characterized in that, The acquisition of the zero-sequence current measurement values ​​of each preset monitoring node includes: Select cable branch box nodes that meet the preset conditions as monitoring nodes; According to a unified synchronization time reference, zero-sequence current waveform data of the monitoring node is collected within a preset time window after the fault occurs. The zero-sequence current waveform data at each monitoring point are preprocessed to obtain the zero-sequence current measurement value at each monitoring node.

5. The method for rapid location of grounding faults in a cable branch box according to claim 4, characterized in that, The process of allocating the zero-sequence current measurement values ​​of each monitoring node to the virtual channel network and calculating the virtual branch current of each virtual fault channel includes: Obtain the hierarchical relationship between each virtual fault channel and each monitoring node in the virtual channel network, and generate a monitoring node coverage relationship matrix; Based on the monitoring node coverage relationship matrix and the zero-sequence current measurement value of each monitoring node, the initial branch current vector of each virtual fault channel is calculated by the current allocation algorithm. Based on the topology mapping relationship between the physical connection topology and the virtual channel network, the initial branch current vector is corrected by topology constraints to generate a correction coefficient vector; The initial branch current vector is weighted using the correction coefficient vector to obtain and output the virtual branch current of each virtual fault channel.

6. The method for rapid location of grounding faults in a cable branch box according to claim 5, characterized in that, The process of obtaining the impedance parameters of each virtual fault channel, and then verifying and filtering them in conjunction with the virtual channel network, the virtual branch current, and the zero-sequence current measurement to obtain the target virtual channel set includes: Obtain the impedance parameters of each virtual fault channel, and combine them with the virtual channel network and the virtual branch current to calculate the fault distance corresponding to each virtual fault channel and generate a fault distance set. Time-frequency analysis is performed on the transient component in the zero-sequence current measurement to extract transient energy characteristics; The transient energy feature is mapped to the virtual channel network, and the distribution differences of the same transient energy feature on different virtual fault channels are analyzed to generate a channel energy difference vector. Based on the calculated residuals of each fault distance in the fault distance set and the channel energy difference vector, a dual-modal verification is performed on each virtual fault channel to filter out the target virtual channel set.

7. The method for rapid location of grounding faults in a cable branch box according to claim 6, characterized in that, The step of performing dual-modal verification on each virtual fault channel based on the difference vector between each fault distance in the fault distance set and the channel energy, and filtering out the target virtual channel set includes: Extract the residuals of the fault distances corresponding to each virtual fault channel from the fault distance set, and generate a channel residual vector; The channel energy difference vector is normalized to obtain the channel energy difference index vector. The confidence score of the corresponding virtual fault channel is obtained by weighting the channel residual vector and the channel energy difference index vector. The set of target virtual channels is obtained by filtering out virtual fault channels whose confidence scores are greater than a preset score threshold.

8. The method for rapid location of grounding faults in a cable branch box according to claim 7, characterized in that, The step of weighting the channel residual vector and channel energy difference index vector of the corresponding virtual fault channel to obtain the confidence score of the corresponding virtual fault channel also includes: Identify the current shunting characteristics of the virtual channel network and calculate the shunting interference compensation coefficient; The confidence score is adjusted by using the shunt interference compensation coefficient.

9. The method for rapid location of grounding faults in a cable branch box according to claim 7, characterized in that, The step of mapping the target virtual channel set to the physical connection topology, determining and outputting the physical location of the fault point includes: Sort the confidence scores in the target virtual channel set from largest to smallest, and select the virtual fault channel corresponding to the first confidence score as the main judgment channel; The main decision channel is mapped to the physical connection topology to obtain the line segment sequence; Based on the fault distance corresponding to the main determination channel, determine the physical location point in the line segment sequence; The physical location point is cross-validated with the virtual fault channels in the target virtual channel set, and the physical location of the fault point is output based on the validation results.

10. A rapid location system for grounding faults in cable branch boxes, characterized in that, The system includes: The topology building module is used to establish a physical connection topology, including grounding reference points, with each cable branch box in the power distribution system as a node. The channel network generation module is used to define a virtual fault channel for each fault current path between each node and the ground reference point based on the physical connection topology, and generate a virtual channel network. The zero-sequence current acquisition module is used to acquire the zero-sequence current measurement values ​​of each preset monitoring node; The virtual branch current calculation module is used to allocate the zero-sequence current measurement values ​​of each monitoring node to the virtual channel network and calculate the virtual branch current of each virtual fault channel. The target channel filtering module is used to obtain the impedance parameters of each virtual fault channel, and combine them with the virtual channel network, the virtual branch current, and the zero-sequence current measurement value to perform verification and filtering to obtain a set of target virtual channels; The fault location mapping module is used to map the target virtual channel set to the physical connection topology, determine and output the physical location of the fault point.

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