A rural low-voltage transformer area residual current pruning positioning and sectionalization protection method and system

Abstract

A rural low-voltage area residual current pruning positioning segmented protection method and system. The system configures collection terminals and segmented switches according to non-full quantity distribution, establishes an area topology table containing parent-child relationship, level, switch position and historical baseline residual current. Each terminal synchronously collects residual current waveform and voltage phasor, calculates effective value, fundamental amplitude, relative phase, harmonic content, mutation and upper and lower level correlation. The master control terminal forms a joint criterion with amplitude out-of-limit, continuous window number, phase consistency, correlation and mutation persistence, eliminates transient disturbance such as lightning stroke and inrush current; calculates the comprehensive score of candidate child nodes containing amplitude, duration, phase, correlation, parent-child differential contribution and level depth factor, prunes and locates the last level abnormal visible node according to the level threshold, maps it into an isolable fault section and outputs a segmented protection instruction. The present application realizes accurate positioning of the fault section under the condition of non-full quantity distribution, and reduces the power failure range.

Description

Technical Field

[0001] This invention belongs to the field of leakage protection technology for low-voltage distribution networks, and more specifically, relates to a method and system for residual current pruning and segmentation protection in rural low-voltage distribution areas. Background Technology

[0002] Rural low-voltage distribution areas typically exhibit characteristics such as long power supply radii, numerous branch levels, dispersed user access, and large seasonal load fluctuations. Installing residual current acquisition terminals on every user branch line would result in high equipment costs, communication maintenance, and subsequent verification workload. Conversely, deploying protectors only on the main line or a few branches would make it difficult to determine the isolated fault location due to insufficient end-point information. Residual current is also affected by factors such as aging line insulation, humid environments, the start-up and shutdown of agricultural equipment, capacitive leakage, and grid connection of distributed photovoltaic inverters. Simply relying on amplitude thresholds for operation can easily lead to false trips, failure to trip, or overly broad fault location.

[0003] Under the above methods, if the main protection trips first, it can easily cause a power outage in the entire area; if the branch protection settings are too high, it may fail to trip or have an excessively wide positioning range; if the settings are too low, it is easily affected by lightning strikes, inrush currents, single-phase heavy load starts and stops, high-order harmonics, and transient leakage currents from photovoltaic inverters, leading to false trips. After a fault occurs, maintenance personnel often need to test power on branch by branch, disconnect the circuit to troubleshoot, or go to the site to measure point by point.

[0004] In summary, there is an urgent need for a residual current fault location and segmented protection method applicable to rural low-voltage distribution areas with non-full-scale terminal points, which can still quickly determine candidate fault sections even when the number of visible acquisition nodes is limited. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method and system for residual current pruning and segmented protection in rural low-voltage distribution areas. The system does not require the installation of a data acquisition terminal on every user branch. Instead, it selectively installs data acquisition and protection terminals at the distribution transformer's low-voltage main box, key branch outgoing line boxes, and necessary meter boxes or on the user side. Residual current is collected via zero-sequence current transformers, and a phase reference is established using the fundamental phasor of the in-phase voltage. Node data is transmitted back via HPLC, RS485, or wireless communication. The distribution area's main control terminal, based on the topology diagram, joint criteria, parent-child differential contribution, and hierarchical gating scoring, locates the isolable fault section and outputs segmented switch tripping, blocking, reset, or alarm commands.

[0006] The present invention adopts the following technical solution. The first aspect of the present invention provides a method for residual current pruning and segmented protection of rural low-voltage distribution areas, comprising the following steps: Step 1: Construct a non-full-scale distribution network topology table for rural low-voltage distribution areas based on the necessity of network deployment and generate a network topology map; Step 2: Calculate the residual current RMS value, fundamental amplitude, relative voltage phase, third and above harmonic content, waveform abrupt change, and upper and lower level correlation of each node in the transformer area topology diagram; Step 3: Based on the data in Step 2, a joint criterion is formed according to amplitude exceeding the limit, duration, phase consistency, correlation between upper and lower levels, persistence of abrupt changes, and short-term impact interference characteristics. If the data corresponding to the node meets the joint criterion, it is determined that a persistent grounding leakage fault has occurred in the topology path where the node is located; otherwise, it is a transient disturbance. Step 4: Using the node on which the fault in the topology path determined in Step 3 is based as the parent node, extract all its child nodes and filter them according to the joint criterion. Child nodes that pass the criterion are recorded as candidate child nodes. Calculate the amplitude score, duration score, phase consistency score, upper-lower level correlation score, and parent-child differential contribution with the corresponding parent node for each candidate child node to obtain a comprehensive score for each candidate child node. The parent-child differential contribution is calculated based on the positive increment of the residual current before and after the fault of the candidate child node and the parent node. Filter according to the pruning threshold corresponding to the level of each candidate child node and retain candidate child nodes whose comprehensive score is not less than the pruning threshold. Based on the retained candidate child nodes, obtain the last-level abnormal node, and obtain the fault section location result based on the last-level abnormal node. Step 5: Based on the fault section location result, output the trip or lockout command. After the fault section is tripped, the non-fault section is kept powered. During reset, the remaining current is confirmed to be below the threshold before closing is allowed. If the closing attempt fails, the circuit is locked out.

[0007] Preferably, in step 1, the specific method for constructing a non-full-scale distribution area topology table based on the necessity of distribution points is as follows: taking the distribution area transformer as the main node, and the branch nodes of the power supply path between the main node and each end user node are sequentially from the first level to the second level. Level branch nodes, among which, Subtract 1 from the number of branches of the corresponding power supply path; designate the main node and first-level branch node of the transformer area as mandatory deployment locations; do not designate each end user node as a deployment location; designate the nodes other than the main node, first-level branch node and end user node as preferred deployment locations; The necessity of each optimal placement location is calculated using the following method: The system acquires the following flags: a humid environment flag indicating whether the candidate section is located in a humid environment; a seasonal power load flag indicating whether the candidate section is connected to seasonal power loads; and a distributed photovoltaic flag indicating whether the candidate section is connected to distributed photovoltaic or inverters. Each flag is a binary variable, and its value is 1 when the corresponding condition is met, and 0 otherwise. Calculate the ratio of the length of the candidate segment where the optimal placement location is located to the length of the longest candidate segment among all optimal placement locations to obtain a first ratio; calculate the ratio of the number of downstream users at the optimal placement location to the number of meter box users at all optimal placement locations to obtain a second ratio. The humid environment indicator, seasonal power load indicator, distributed photovoltaic indicator, first ratio and second ratio are weighted and summed to obtain the necessity of the selected location; when the necessity of the location is not less than a set threshold, the location is selected.

[0008] Preferably, in step 2, the method for calculating the correlation between the upper and lower levels is as follows: the Pearson correlation coefficient of the residual current waveform between the node and its upstream adjacent parent node is used as the correlation between the upper and lower levels.

[0009] Preferably, in step 3, the joint criterion includes: The effective value of the total residual current exceeds the total threshold for N consecutive judgment windows, and the fundamental amplitude of the total residual current also exceeds the total fundamental threshold; the effective value of the residual current of the sub-nodes on the same path exceeds the threshold of the corresponding node, and the fundamental amplitude of the residual current of the sub-node also exceeds the fundamental threshold of the corresponding node. The relative voltage phase difference between the child node and the parent node is less than the preset phase difference threshold; The third and higher harmonic content did not exhibit characteristics of lightning pulse or inrush current impact interference. The waveform abrupt change remains in the same direction or continuously exceeds the abrupt change threshold within at least N duration determination windows; The hierarchical correlation between the child node and its parent node is greater than the preset correlation threshold; When the above conditions are met simultaneously, it is determined that there is a persistent grounding leakage fault in the topology path where the node is located; otherwise, it is a transient disturbance.

[0010] Preferably, in step 4, the specific method for calculating the amplitude score is as follows: The difference between the effective value of the residual current of the candidate child node and the preset node threshold of the candidate child node is calculated as the first value; the difference between the preset node threshold of the candidate child node and the residual current of the historical baseline is calculated as the second value; the ratio of the first value to the second value is calculated, and the ratio is truncated to the interval between 0 and 1 to obtain the amplitude score. The specific calculation method for the duration score is as follows: The ratio of the number of consecutive out-of-limit windows of the candidate child node to the duration window number threshold specified in the joint criterion is calculated, and the minimum value of this ratio compared with 1 is taken to obtain the duration score; The specific calculation method for the relevant consistency score is as follows: Calculate the relative voltage phase difference between the candidate child node and its corresponding parent node, and map the phase difference to a preset range using a phase wrapping operator; take the square of the mapped value as the third value; calculate twice the square of the phase difference tolerance of the level where the candidate child node is located, and take it as the fourth value; calculate the ratio of the third value to the fourth value, and take the negative of the ratio as the exponent of the natural constant e; and obtain the correlation consistency score after calculation. The specific calculation method for the superior-subordinate relevance score is as follows: Calculate the hierarchical correlation of the residual current waveform between the candidate child node and its corresponding parent node. Calculate the difference between the hierarchical correlation and the preset correlation threshold in the level where the candidate child node is located, and use this difference as the fifth value. Calculate the difference between 1 and the correlation threshold, and use this difference as the sixth value. Calculate the ratio of the fifth value to the sixth value, and truncate the ratio to obtain the hierarchical correlation score. The specific calculation method for the parent-child differential contribution is as follows: Calculate the ratio of the differential imbalance of the candidate child node to the preset differential tolerance in the level where the candidate child node is located. Take the negative of this ratio and use it as the exponent of the natural constant e. The resulting value is the seventh value. Calculate the ratio of the positive increment of the residual current before and after the fault of the candidate child node to the positive increment of the residual current before and after the fault of the corresponding parent node. Truncate this ratio and use it as the eighth value. Multiply the seventh value and the eighth value to obtain the parent-child differential contribution. The specific calculation method for the comprehensive score is as follows: The magnitude score and duration score of the candidate child node are respectively exponentialized and then multiplied to obtain the ninth value; the phase consistency score, superior-inferior correlation score, and parent-child difference contribution of the candidate child node are weighted and calculated to obtain the tenth value; the ratio of the level depth of the candidate child node to the maximum level depth of the transformer area topology is recorded as the normalized level depth, and the product of the set level depth adjustment coefficient and the normalized level depth is incremented by 1 to obtain the eleventh value; the product of the ninth, tenth, and eleventh values ​​is calculated to obtain the comprehensive score of the candidate child node.

[0011] More preferably, the specific method for determining the number of duration windows in the duration score is as follows: Calculate the ratio of the preset duration threshold to the determination window duration. This ratio is used as the twelfth value. After rounding the twelfth value up, the range is limited to the set range. The resulting integer is the number of duration windows.

[0012] More preferably, the specific calculation method for the phase difference tolerance of the node level in the relevant consistency score is as follows: Set a basic phase tolerance; calculate the difference between the level number of the candidate child node and 1, and multiply the difference by a preset level increment coefficient as the thirteenth value; calculate the absolute value of the difference between the sampling timestamp of the candidate child node and the sampling timestamp of the corresponding parent node, and multiply the absolute value of the difference by a preset timestamp deviation compensation coefficient as the fourteenth value; add the thirteenth value, the fourteenth value and the basic phase tolerance to obtain the phase difference reference value, and compare the phase difference reference value with the set upper and lower limits of the phase difference tolerance to obtain the phase difference tolerance of the level of the candidate child node.

[0013] More preferably, the specific method for calculating the difference imbalance degree in the parent-child difference contribution is as follows: The positive increments of residual current before and after the fault of all child nodes under the parent node corresponding to the candidate child node that pass the joint criterion are summed to obtain a summed result; the absolute value of the difference between the positive increment of residual current before and after the fault of the parent node and the summed result is calculated as the fifteenth value; the larger value is taken between the positive increment of residual current before and after the fault of the parent node and the preset minimum effective increment; the ratio of the fifteenth value to the larger value is calculated, and this ratio is taken as the differential imbalance degree.

[0014] Preferably, in step 4, the method for determining the lowest-level abnormal node is as follows: If there are still visible child nodes downstream of the retained candidate child node that satisfy the joint criteria, then the candidate child node is used as the new parent node, and the steps of candidate child node extraction, filtering, scoring and pruning are repeated to continue searching downwards; if there are no visible child nodes downstream of the retained candidate child node that satisfy the joint criteria, then the candidate child node is used as the last-level abnormal node. The method for obtaining the fault section location result is as follows: Using the last-level abnormal node as the upstream boundary and the nearest downstream visible node, meter box outgoing line, or user access point as the downstream boundary, an isolable fault section is formed. If there are multiple fault sections, the priority is determined in the following order: first, the level depth; second, the parent-child differential contribution; and third, the comprehensive score.

[0015] Preferably, the method further includes step 6, generating a fault record file containing the fault location, action time and reset status based on the fault section location result and the execution result of the segment protection action, and uploading the fault record file to the cloud server.

[0016] A second aspect of the present invention provides a residual current pruning and positioning segmented protection system for rural low-voltage distribution transformer areas, comprising the following methods: The transformer area topology map construction module: constructs a non-full-scale transformer area topology table based on the necessity of transformer deployment and generates a transformer area topology map; Synchronous sampling and feature extraction module: Calculates the residual current RMS value, fundamental amplitude, relative voltage phase, third and above harmonic content, waveform abrupt change and upper and lower level correlation of each node in the transformer area topology map; Fault type joint criterion module: Based on the data calculated in the synchronous sampling and feature extraction module, a joint criterion is formed according to amplitude exceeding the limit, number of continuous windows, phase consistency, correlation between upper and lower levels, persistence of sudden change and short-term impact interference to determine whether a persistent grounding leakage fault has occurred in the topology path where the deployment node is located; The hierarchical pruning and localization mapping module uses the node on which the fault is determined in the joint fault type criterion module as the parent node and extracts all its candidate child nodes; calculates the comprehensive score of each candidate child node; filters according to the pruning threshold corresponding to the level of each candidate child node and retains the candidate child nodes whose comprehensive score is not less than the pruning threshold; based on the retained candidate child nodes, the last-level abnormal node is obtained, and the fault segment localization result is obtained based on the last-level abnormal node. Segmented protection and reset module: Based on the fault segment location result, output trip or lockout command, and maintain power supply to non-faulty segments after tripping the fault segment; during reset, allow closing after confirming that the residual current is below the threshold, and enter lockout if the closing attempt fails. Event logging and cloud upload module: Generates fault log files based on the execution results of the segmented protection and reversion module, and uploads them to the cloud.

[0017] A third aspect of the present invention provides a terminal, including a processor and a storage medium, the storage medium being used to store instructions; the processor being used to execute, according to the instructions, a method for residual current pruning and segmented protection in rural low-voltage distribution areas.

[0018] A fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the aforementioned method for residual current pruning and segmented protection in rural low-voltage distribution areas.

[0019] Compared with the prior art, the beneficial effects of the present invention include at least the following: (1) Under the condition of non-full deployment, the visible node data of the main road, key branches and necessary meter boxes are used to locate the fault section, thereby reducing the equipment cost and operation and maintenance complexity of full terminal deployment in rural transformer areas.

[0020] (2) The single-point amplitude limit judgment is extended to a judgment process constrained by amplitude, duration, phase consistency, upper and lower level correlation and waveform mutation duration relationship, which reduces the probability of false operation caused by lightning induction, switching impact and photovoltaic inverter harmonic disturbance.

[0021] (3) Use the transformer area topology map to perform hierarchical search and pruning to narrow the fault range from the main road or the entire transformer area to the isolated section downstream of the last level abnormal node.

[0022] (4) After the positioning result is formed, only the corresponding section switch is tripped or blocked, and the power supply of the non-faulty branch is retained. Attached Figure Description

[0023] Figure 1 This is a flowchart of a method for residual current pruning, positioning, and segmented protection in rural low-voltage distribution areas according to the present invention. Figure 2 This is a block diagram of the overall architecture of the rural low-voltage residual current location and segmented protection system provided by the present invention; Figure 3 This is a hardware structure diagram of the transformer area leakage current collaborative control terminal provided in accordance with the present invention; Figure 4 This is a block diagram illustrating the principle of synchronous sampling and feature extraction in the acquisition terminal provided by the present invention; Figure 5 This is a schematic diagram of the branch topology and fault location of the transformer area provided in accordance with the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this invention.

[0025] This invention proposes a method for residual current pruning and segmented protection in rural low-voltage distribution areas, such as... Figure 1 As shown, the specific steps include: Step 1: Construct a non-full-scale distribution network topology table for rural low-voltage distribution areas based on the necessity of network deployment and generate a network topology map; Preferably, the specific method for constructing a non-full-scale distribution area topology table based on the necessity of distribution points is as follows: taking the distribution area transformer as the main node, and the branch nodes of the power supply path between the main node and each end user node are sequentially numbered from the first level to the second level. Level branch nodes, among which, Subtract 1 from the number of branches of the corresponding power supply path; designate the main node and first-level branch node of the transformer area as mandatory deployment locations; do not designate each end user node as a deployment location; designate the nodes other than the main node, first-level branch node and end user node as preferred deployment locations; The necessity of each optimal placement location is calculated using the following method: The system acquires the following flags: a humid environment flag indicating whether the candidate section is located in a humid environment; a seasonal power load flag indicating whether the candidate section is connected to seasonal power loads; and a distributed photovoltaic flag indicating whether the candidate section is connected to distributed photovoltaic or inverters. Each flag is a binary variable, and its value is 1 when the corresponding condition is met, and 0 otherwise. Calculate the ratio of the length of the candidate segment where the optimal placement location is located to the length of the longest candidate segment among all optimal placement locations to obtain a first ratio; calculate the ratio of the number of downstream users at the optimal placement location to the number of meter box users at all optimal placement locations to obtain a second ratio. The humid environment indicator, seasonal power load indicator, distributed photovoltaic indicator, first ratio and second ratio are weighted and summed to obtain the necessity of the selected location; when the necessity of the location is not less than a set threshold, the location is selected.

[0026] Step 2: Calculate the residual current RMS value, fundamental amplitude, relative voltage phase, third and above harmonic content, waveform abrupt change, and upper and lower level correlation of each node in the transformer area topology diagram; Preferably, the method for calculating the upper-lower level correlation is as follows: the Pearson correlation coefficient of the residual current waveform between a node and its upstream adjacent parent node is used as the upper-lower level correlation.

[0027] Step 3: Based on the data in Step 2, a joint criterion is formed according to amplitude exceeding the limit, duration, phase consistency, correlation between upper and lower levels, persistence of abrupt changes, and short-term impact interference characteristics. If the data corresponding to the node meets the joint criterion, it is determined that a persistent grounding leakage fault has occurred in the topology path where the node is located; otherwise, it is a transient disturbance. Preferably, the joint criterion includes: The effective value of the total residual current exceeds the total threshold for N consecutive judgment windows, and the fundamental amplitude of the total residual current also exceeds the total fundamental threshold; the effective value of the residual current of the sub-nodes on the same path exceeds the threshold of the corresponding node, and the fundamental amplitude of the residual current of the sub-node also exceeds the fundamental threshold of the corresponding node. The relative voltage phase difference between the child node and the parent node is less than the preset phase difference threshold; The third and higher harmonic content did not exhibit characteristics of lightning pulse or inrush current impact interference. The waveform abrupt change remains in the same direction or continuously exceeds the abrupt change threshold within at least N duration determination windows; The hierarchical correlation between the child node and its parent node is greater than the preset correlation threshold; When the above conditions are met simultaneously, it is determined that there is a persistent grounding leakage fault in the topology path where the node is located; otherwise, it is a transient disturbance.

[0028] Step 4: Using the node on which the fault in the topology path determined in Step 3 is based as the parent node, extract all its child nodes and filter them according to the joint criterion. Child nodes that pass the criterion are recorded as candidate child nodes. Calculate the amplitude score, duration score, phase consistency score, upper-lower level correlation score, and parent-child differential contribution with the corresponding parent node for each candidate child node to obtain a comprehensive score for each candidate child node. The parent-child differential contribution is calculated based on the positive increment of the residual current before and after the fault of the candidate child node and the parent node. Filter according to the pruning threshold corresponding to the level of each candidate child node and retain candidate child nodes whose comprehensive score is not less than the pruning threshold. Based on the retained candidate child nodes, obtain the last-level abnormal node, and obtain the fault section location result based on the last-level abnormal node. Preferably, the specific method for calculating the amplitude score is as follows: The difference between the effective value of the residual current of the candidate child node and the preset node threshold of the candidate child node is calculated as the first value; the difference between the preset node threshold of the candidate child node and the residual current of the historical baseline is calculated as the second value; the ratio of the first value to the second value is calculated, and the ratio is truncated to the interval between 0 and 1 to obtain the amplitude score. The specific calculation method for the duration score is as follows: The ratio of the number of consecutive out-of-limit windows of the candidate child node to the duration window number threshold specified in the joint criterion is calculated, and the minimum value of this ratio compared with 1 is taken to obtain the duration score; The specific calculation method for the relevant consistency score is as follows: Calculate the relative voltage phase difference between the candidate child node and its corresponding parent node, and map the phase difference to a preset range using a phase wrapping operator; take the square of the mapped value as the third value; calculate twice the square of the phase difference tolerance of the level where the candidate child node is located, and take it as the fourth value; calculate the ratio of the third value to the fourth value, and take the negative of the ratio as the exponent of the natural constant e; and obtain the correlation consistency score after calculation. The specific calculation method for the superior-subordinate relevance score is as follows: Calculate the hierarchical correlation of the residual current waveform between the candidate child node and its corresponding parent node. Calculate the difference between the hierarchical correlation and the preset correlation threshold in the level where the candidate child node is located, and use this difference as the fifth value. Calculate the difference between 1 and the correlation threshold, and use this difference as the sixth value. Calculate the ratio of the fifth value to the sixth value, and truncate the ratio to obtain the hierarchical correlation score. The specific calculation method for the parent-child differential contribution is as follows: Calculate the ratio of the differential imbalance of the candidate child node to the preset differential tolerance in the level where the candidate child node is located. Take the negative of this ratio and use it as the exponent of the natural constant e. The resulting value is the seventh value. Calculate the ratio of the positive increment of the residual current before and after the fault of the candidate child node to the positive increment of the residual current before and after the fault of the corresponding parent node. Truncate this ratio and use it as the eighth value. Multiply the seventh value and the eighth value to obtain the parent-child differential contribution. The specific calculation method for the comprehensive score is as follows: The magnitude score and duration score of the candidate child node are respectively exponentialized and then multiplied to obtain the ninth value; the phase consistency score, superior-inferior correlation score, and parent-child difference contribution of the candidate child node are weighted and calculated to obtain the tenth value; the ratio of the level depth of the candidate child node to the maximum level depth of the transformer area topology is recorded as the normalized level depth, and the product of the set level depth adjustment coefficient and the normalized level depth is incremented by 1 to obtain the eleventh value; the product of the ninth, tenth, and eleventh values ​​is calculated to obtain the comprehensive score of the candidate child node.

[0029] More preferably, the specific method for determining the number of duration windows in the duration score is as follows: Calculate the ratio of the preset duration threshold to the determination window duration. This ratio is used as the twelfth value. After rounding the twelfth value up, the range is limited to the set range. The resulting integer is the number of duration windows.

[0030] More preferably, the specific calculation method for the phase difference tolerance of the node level in the relevant consistency score is as follows: Set a basic phase tolerance; calculate the difference between the level number of the candidate child node and 1, and multiply the difference by a preset level increment coefficient as the thirteenth value; calculate the absolute value of the difference between the sampling timestamp of the candidate child node and the sampling timestamp of the corresponding parent node, and multiply the absolute value of the difference by a preset timestamp deviation compensation coefficient as the fourteenth value; add the thirteenth value, the fourteenth value and the basic phase tolerance to obtain the phase difference reference value, and compare the phase difference reference value with the set upper and lower limits of the phase difference tolerance to obtain the phase difference tolerance of the level of the candidate child node.

[0031] More preferably, the specific method for calculating the difference imbalance degree in the parent-child difference contribution is as follows: The positive increments of residual current before and after the fault of all child nodes under the parent node corresponding to the candidate child node that pass the joint criterion are summed to obtain a summed result; the absolute value of the difference between the positive increment of residual current before and after the fault of the parent node and the summed result is calculated as the fifteenth value; the larger value is taken between the positive increment of residual current before and after the fault of the parent node and the preset minimum effective increment; the ratio of the fifteenth value to the larger value is calculated, and this ratio is taken as the differential imbalance degree.

[0032] Preferably, the method for determining the lowest-level abnormal node is as follows: If there are still visible child nodes downstream of the retained candidate child node that satisfy the joint criteria, then the candidate child node is used as the new parent node, and the steps of candidate child node extraction, filtering, scoring and pruning are repeated to continue searching downwards; if there are no visible child nodes downstream of the retained candidate child node that satisfy the joint criteria, then the candidate child node is used as the last-level abnormal node. The method for obtaining the fault section location result is as follows: Using the last-level abnormal node as the upstream boundary and the nearest downstream visible node, meter box outgoing line, or user access point as the downstream boundary, an isolable fault section is formed. If there are multiple fault sections, the priority is determined in the following order: first, the level depth; second, the parent-child differential contribution; and third, the comprehensive score.

[0033] Step 5: Based on the fault section location result, output the trip or lockout command. After the fault section is tripped, the non-fault section is kept powered. During reset, the remaining current is confirmed to be below the threshold before closing is allowed. If the closing attempt fails, the circuit is locked. Preferably, the method further includes step 6, generating a fault record file containing the fault location, action time and reset status based on the fault section location result and the execution result of the segment protection action, and uploading the fault record file to the cloud server.

[0034] This invention also proposes a residual current pruning and segmented protection system for rural low-voltage transformer areas, including a transformer area topology map construction module, a synchronous sampling and feature extraction module, a fault type joint criterion module, a hierarchical pruning and positioning mapping module, a segmented protection and reset module, and an event recording and cloud upload module. The transformer area topology map construction module: constructs a non-full-scale transformer area topology table based on the necessity of transformer deployment and generates a transformer area topology map; Synchronous sampling and feature extraction module: Calculates the residual current RMS value, fundamental amplitude, relative voltage phase, third and above harmonic content, waveform abrupt change and upper and lower level correlation of each node in the transformer area topology map; Fault type joint criterion module: Based on the data calculated in the synchronous sampling and feature extraction module, a joint criterion is formed according to amplitude exceeding the limit, number of continuous windows, phase consistency, correlation between upper and lower levels, persistence of sudden change and short-term impact interference to determine whether a persistent grounding leakage fault has occurred in the topology path where the deployment node is located; The hierarchical pruning and localization mapping module uses the node on which the fault is determined in the joint fault type criterion module as the parent node and extracts all its candidate child nodes; calculates the comprehensive score of each candidate child node; filters according to the pruning threshold corresponding to the level of each candidate child node and retains the candidate child nodes whose comprehensive score is not less than the pruning threshold; based on the retained candidate child nodes, the last-level abnormal node is obtained, and the fault segment localization result is obtained based on the last-level abnormal node. Segmented protection and reset module: Based on the fault segment location result, output trip or lockout command, and maintain power supply to non-faulty segments after tripping the fault segment; during reset, allow closing after confirming that the residual current is below the threshold, and enter lockout if the closing attempt fails. Event logging and cloud upload module: Generates fault log files based on the execution results of the segmented protection and reversion module, and uploads them to the cloud.

[0035] The present invention also proposes a terminal, including a processor and a storage medium; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps according to the method described above.

[0036] The present invention also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0037] Example 1 like Figure 2-5 As shown, Embodiment 1 of the present invention provides a method for residual current pruning and segmented protection of rural low-voltage distribution areas, comprising the following steps: Step 1: Enter the transformer area topology table when the system is put into operation, and assign a unique number to each acquisition terminal and sectionalizing switch.

[0038] In a preferred but non-limiting embodiment of the present invention, step 1 specifically includes: The system pre-establishes a non-full-scale distribution area topology table, using the distribution area transformer as the main node, and the branch nodes of the power supply path from the main node to each end user node are sequentially designated as primary to secondary nodes. Level branch nodes, among which, The number of branches in the corresponding power supply path is reduced by 1. The secondary branch and the terminal branch are the meter box branch. The non-full-scale deployment is not a random reduction in the number of points, but rather a mandatory deployment location is set for the main road node and the first-level branch node. No data acquisition terminal is deployed for the terminal user branch, but its upstream visible node, downstream user range and associated sectionalizing switch are registered in the topology table. Each data acquisition terminal records the node number, upstream node, downstream node, corresponding switch number, installation location and deployment reason. Special nodes in the meter box branch nodes are selected as the optimal deployment locations. Specifically, meter box nodes with line lengths exceeding 1.2 times the average branch length of this area, wet fish ponds or agricultural irrigation power loads, distributed photovoltaic access, centralized user access, and frequent historical leakage events are selected as the optimal deployment locations.

[0039] Necessity of site selection Calculated using the following weighted formula:

[0040] in, Candidate segment Length, The longest candidate segment length among all optimal point locations, in meters; The value is 1 when the candidate section is located near a wet fishpond, pump house, well or agricultural irrigation ditch, and 0 otherwise. This is a seasonal power load indicator. When seasonal power loads such as agricultural irrigation pumps, livestock fans, or grain dryers are connected to the candidate section, the value is 1; otherwise, the value is 0. This is a distributed photovoltaic (PV) indicator. It takes a value of 1 when there is distributed PV or inverter connected to the candidate section, and a value of 0 otherwise. For candidate watch boxes Number of downstream users The maximum number of meter box users among all the optimal placement locations, in units of households. Points with a value of 0.55 or higher are prioritized for deployment; points with a value between 0.35 and 0.55 are reserved or used for inspection; points with a value below 0.35 are not deployed but are registered as undeployed downstream sections. The weights of each item in the formula for calculating the necessity of point deployment are preferred values ​​of this invention and can be redefined according to the actual application.

[0041] The above formula uses candidate section length, humid environment indicator, seasonal power load indicator, distributed photovoltaic indicator and number of downstream users as core calculation factors because they together cover the two essential aspects of technical feasibility and socio-economic benefits in non-full-scale deployment decision-making.

[0042] The length of the candidate section directly determines the line-to-ground capacitance and signal attenuation. The longer the length, the greater the background leakage current and the more difficult it is for the upstream node to capture the characteristics of the fault at the far end. Therefore, it is necessary to add observation points in the middle of the long line to make up for the information gap. The damp environment markers address the problem of continuous moisture in the insulation of rural fish ponds, wells, and other areas. If these markers are not placed, the system will be unable to distinguish between normal background leakage and dangerous faults, resulting in baseline inaccuracy. Seasonal power load indicators correspond to the violent surges and transient impacts generated when equipment such as agricultural irrigation pumps and dryers start and stop. If these indicators are not placed at this location, the system is very likely to misjudge such normal disturbances as permanent grounding faults. The distributed photovoltaic indicator corresponds to the high-frequency harmonics and reverse residual current components injected by the inverter. If the indicator is not placed here, the phase consistency and waveform correlation criteria of the upper and lower level nodes will be severely interfered with, leading to confusion of fault paths. The number of downstream users of the candidate meter boxes reflects the social cost of power outages. The more users there are, the more necessary it is to reduce the isolation range and the number of households affected by power outages through the deployment of meter boxes. This is the only factor that can be considered from the perspective of power outage losses.

[0043] All five factors mentioned above are indispensable and work together to ensure that, with limited equipment investment, signals in high-risk areas can be effectively observed, transient impacts can be accurately identified, harmonic interference can be effectively distinguished, and power outage losses can be controlled to a minimum.

[0044] Based on the different influence mechanisms of the above five factors on the success or failure of positioning, their weight allocation should follow the principle of matching contribution, and correspond to the actual constraint degree of each factor in non-full-scale deployment in descending order.

[0045] Candidate segment length and seasonal power load have the highest weights. The former is because the longer the line, the more severe the signal attenuation and the larger the information blind spot under non-full deployment. The latter is because the surge and transient impact it causes are the most severe, and are the primary source of false operation and missed detection in rural transformer areas. The two have the most direct and critical impact on positioning reliability. Humid environments have the second highest weight because they mainly and continuously raise the background baseline and increase fluctuations. Although they do not directly cause abrupt failures, they significantly interfere with threshold setting and baseline estimation accuracy. Distributed photovoltaics account for the second lowest weight because the harmonics and reverse components they introduce have a relatively indirect impact on the fundamental frequency amplitude. They are more of an additional interference at the fault path identification level than a direct obstacle to leakage detection. Downstream users have the lowest weight because they only reflect the social impact of power outages and are not directly related to the electrical characteristics of residual current and fault identification. Too high a weight will cause the deployment to deviate from the sections with the highest physical risk and the worst observation conditions. The aforementioned weighting system ensures that limited equipment is prioritized for deployment in sections where electrical information is scarcest and fault characteristics are most complex, thereby achieving efficient allocation of monitoring resources.

[0046] Specifically, the transformer area topology table is based on the transformer area topology map. and retrieval in the form of , where This represents a set of nodes including the main protector, branch protectors, meter box data acquisition units, user access points, and sectionalizing switches. This indicates the electrical connection relationship between higher and lower levels. For any node... Record its parent node child node set Level Associated switches Branch rated current Historical baseline residual current Whether to deploy data collection terminals and the necessity of deployment points. And the corresponding phase or user range. Among them, For nodes The rated current (in A) of the branch is a hardware parameter of the line or equipment, determined by the conductor cross-section and switch capacity. For nodes The historical baseline residual current (in mA) is obtained from the statistical analysis of the normal operation data of the past 30 days and is the average background leakage current of the corresponding node.

[0047] When locating faults, the MCU / edge control unit searches for the abnormal propagation path layer by layer from the root node to the leaf node according to the topology map, and maps the search results to the isolable sections between adjacent switches.

[0048] Step 2: Based on the non-full-scale deployment area topology map constructed in Step 1, the main control terminal determines the node affiliation, parent-child relationship and deployment attributes of each deployment terminal, and sends a synchronous sampling command to the visible deployment nodes in the topology map; the main line, branch and meter box terminals respond to the command and collect the remaining current, voltage phase and waveform characteristics according to the same power frequency window.

[0049] In a preferred but non-limiting embodiment of the present invention, step 2 specifically includes: Each terminal at each deployment point acquires the residual current waveform at a sampling frequency of no less than 2kHz, using the power frequency zero-crossing point or the synchronization message sent by the main control terminal as the starting point of the sampling window. Each calculation window takes 5 to 10 power frequency cycles, and the following characteristic quantities are calculated: RMS value of residual current. Fundamental amplitude Relative voltage phase Third and higher harmonic content Waveform abrupt change Relevance between superiors and subordinates Each acquisition terminal sends the aforementioned feature values ​​and the compressed waveforms of the most recent windows to the main control terminal, which retains at least 30 days of event records.

[0050] Specifically, let the first The residual current sampling sequence of each node within a decision window is as follows: , The effective value of the residual current It can be calculated using the following formula:

[0051] In the formula, For the first The effective value of the residual current at the node, in mA. For the first Node number The instantaneous residual current at each sampling point, in mA. The total number of sampling points within a sampling window. , Sampling frequency, This is the window duration.

[0052] For the sampled sequence Perform a Discrete Fourier Transform to extract the fundamental phasor of the 50Hz residual current, and use the magnitude of this fundamental phasor as the fundamental amplitude. :

[0053] Relative voltage phase Determined based on the phase angle difference between the fundamental phasor of the residual current and the fundamental phasor of the in-phase voltage:

[0054] In the formula, The fundamental phasor of in-phase voltage is the voltage phase reference quantity. The argument is a complex number; the fundamental amplitude is used for amplitude exceeding the limit criterion, and the relative voltage phase is used for phase consistency criterion between upstream and downstream nodes.

[0055] Third and higher harmonic content It can be calculated using the following formula:

[0056] In the formula, For the first Node number Second harmonic current components The highest harmonic order analyzed is determined by the sampling frequency:

[0057] Waveform abrupt change The difference between the effective values ​​of adjacent windows can be used for calculation:

[0058] In the formula, This represents the effective value of the remaining current in the current window. The residual current RMS value of the previous window; waveform abrupt change is used to determine whether the abnormality is developing continuously, and together with the harmonic content, it is used to eliminate short-term impulsive interference.

[0059] Superior-subordinate correlation It can be calculated using the following formula:

[0060] In the formula, For nodes The residual current sampling sequence, The sampling sequence of the residual current of its upstream adjacent parent node. and These are the mean values ​​of the two.

[0061] The feature calculation window in the above formula is preferably 5 to 10 power frequency cycles; the sliding comparison window for rapid impact identification can be 1 to 5 decision windows; the harmonic order can be selected according to the sampling frequency up to an effective order not higher than the Nyquist frequency.

[0062] More preferably, the sampling frequency is 2kHz to 10kHz to ensure that the fundamental, harmonic and transient characteristics of the residual current can be identified.

[0063] Step 3: Based on the original data from Step 2, make the first decision by forming a joint criterion based on amplitude exceeding the limit, duration, phase consistency, correlation between upper and lower levels, persistence of sudden changes, and short-term impact interference characteristics. If the data corresponding to the node meets the joint criterion, it is determined that a persistent grounding leakage fault has occurred in the topology path where the node is located; otherwise, it is a transient disturbance.

[0064] In a preferred but non-limiting embodiment of the present invention, step 3 specifically includes: The main control terminal does not solely rely on a single amplitude exceeding the limit for tripping, but rather uses a combined judgment based on amplitude exceeding the limit, duration, relative voltage phase consistency, correlation between upper and lower levels, and the persistence of waveform abrupt changes. An example criterion is: Duration and amplitude exceeding limits: Effective value of total residual current If N consecutive decision windows exceed the total path threshold Furthermore, the fundamental amplitude of the total residual current synchronously exceeds the total fundamental threshold; the effective value of the residual current of the sub-nodes on the same path Exceeding the corresponding node threshold Furthermore, the fundamental amplitude of the residual current in the sub-node synchronously exceeds the fundamental threshold of the corresponding node; Relative voltage phase consistency: relative voltage phase of child nodes Relative voltage phase with its upstream adjacent parent node The difference is less than the preset phase difference threshold; Hierarchical correlation: The correlation between the waveform of a child node and the waveform of its upstream adjacent parent node. Greater than the preset relevance threshold; Waveform abrupt change persistence: The waveform abrupt change remains in the same direction within no less than N judgment windows, or its absolute value is continuously higher than the abrupt change threshold; The third and higher harmonic content did not exhibit short-term impulse interference characteristics such as lightning pulses or inrush currents. Impulse interference refers to residual current or waveform abrupt changes exceeding the corresponding threshold, but the anomaly only lasts for a short period of time. Transient processes within a decision window. Preferably, values ​​of 1 to 3 are selected; if the amplitude anomaly, relative voltage phase consistency, and waveform abrupt change on the same topology path remain continuously for more than One decision window, If the optimal value is 3 to 5, then the single-impact rejection will no longer be used, but the process will proceed to the joint criterion and segmented location process. This allows for the differentiation between short-term switching impacts, lightning-induced spikes, and continuous grounding leakage currents.

[0065] When the above conditions are met simultaneously, the main control terminal determines that a continuous grounding leakage fault has occurred in the topology path where the node is located; otherwise, it is a transient disturbance.

[0066] More preferably, the total path threshold The range is 100mA to 500mA, set according to the on-site main protection setting, used to determine whether the total circuit meets the amplitude over-limit condition. When the on-site main protection device is not in operation, the main protection device setting value is unreadable, or historical setting values ​​are missing, the total circuit threshold is determined by selecting the optimal value between the default protection threshold and the capacity conversion threshold.

[0067] In the formula, The maximum value among all branch thresholds. and All units are mA. The lower limit of 100mA is to ensure sensitivity, and the upper limit of 500mA is to align with the maximum allowable value of the main circuit protection. When the transformer area has nearly 30 days of normal operating data, the main circuit threshold is adjusted based on the historical background residual current. In the formula, This represents the average residual current in the background of the total circuit. Standard deviation Ideally, 3 to 5 should be chosen. If... Greater than the current The threshold is then raised to prevent false triggering caused by normal background leakage. Through this default rule, even if the status of the field protector is unknown, the system can obtain an executable initial judgment threshold and can be corrected based on operational data after commissioning.

[0068] More preferably, the node threshold The current range is 30mA to 300mA, adjusted according to the branch capacity.

[0069] Node threshold With branch rated current In the conversion, all thresholds are expressed in mA, and the following formula is preferred for calculation: In the formula, For the first Branch rated current (unit: A). The conversion factor is 0.8 to 1.5 mA / A, with a default value of 1.0 mA / A; for example, a branch with a rated current of 100A. The default value is 100mA. The lower limit of 30mA ensures the sensitivity of the branch leakage protection, and the upper limit of 300mA prevents the branch protection setting value from being too high and thus losing its protective significance.

[0070] For branches with high background leakage during humid seasons, node threshold Correction based on residual current in historical context: In the formula, This represents the historical baseline residual current of this branch. Standard deviation The preferred values ​​are 3 to 5, after correction. The amplitude must not exceed the selective coordination limit allowed by the superior protection. The above formula allows the amplitude exceeding the limit criterion to be matched with the line rated current, historical background leakage, and the selectivity of the superior and inferior protection systems.

[0071] More preferably, the preset correlation threshold is selected from 0.70 to 0.90; wherein, the first-level branch layer is selected from 0.70 to 0.80 to accommodate waveform mixing caused by multiple load superposition; the meter box layer is selected from 0.75 to 0.85; and the end visible node layer is selected from 0.80 to 0.90 to reduce the probability of adjacent background leakage branches mistakenly entering the candidate path. The phase difference threshold is selected from 15 degrees to 45 degrees; the mutation threshold is determined by the engineering setting table written into the main control terminal, and is not based on the first... The standard deviation of the residual current waveform abrupt change at each level is used as a necessary calculation condition. The engineering setting table is set according to the node level, and the selection range of the abrupt change threshold is between 30mA and 100mA; among which, the threshold is 50mA to 80mA for first-level branch nodes, 30mA to 60mA for meter box nodes, and 30mA to 50mA for end visible nodes.

[0072] More preferably, the harmonic content The threshold for determining a significant level It can be determined by the following formula:

[0073] In the formula, This represents the historical background harmonic level of the transformer area (obtained from statistics of normal operation data over the past 30 days).

[0074] Step 4: Based on the topology map from Step 1 and the persistent grounding leakage fault signal confirmed in Step 3, a second decision is made to determine the faulty section.

[0075] In a preferred but non-limiting embodiment of the present invention, step 4 specifically includes: When a fault occurs, the main control terminal searches the topology tree from top to bottom for the lowest visible node that meets the joint criteria and comprehensive score. If a branch node is abnormal and none of its downstream visible meter box nodes meet the joint criteria, the line between the associated switch of that branch node and the downstream visible meter box or end user access point is identified as the faulty section. If a meter box node is abnormal and there are no visible nodes downstream, the fault is located to the downstream user branch of that meter box. If multiple child nodes are abnormal at the same time, they are sorted according to node level depth, parent-child differential contribution, and comprehensive score, and multiple candidate sections and priorities are output if necessary.

[0076] To achieve the above search and location process, the "top-down search" is further decomposed at the execution level into four progressive actions: joint criterion filtering, dimensionless scoring, hierarchical pruning, and segment mapping.

[0077] Using the node on which the fault in the topology path determined in step 3 is based as the parent node, extract all its child nodes and filter them according to the joint criteria. Child nodes that pass the criteria are recorded as candidate child nodes. If the amplitude, duration, relative voltage phase consistency or upper and lower level correlation of the child node does not meet the joint criteria conditions, then the child node and its downstream subtree will no longer participate in this round of search. This is the triggering condition for the pruning action.

[0078] Among them, the joint criterion factor satisfies the joint criterion. Then proceed to the comprehensive scoring stage; if any condition is not met... The node and its downstream subtrees are pruned as a whole.

[0079] Furthermore, a comparable quantitative evaluation is performed on the candidate child nodes, defining the following dimensionless scoring index: (1) Amplitude values

[0080] The amplitude score reflects the degree to which the effective value of the residual current at the node exceeds its operating threshold.

[0081] in, Candidate child nodes The effective value of the residual current, Candidate child nodes The node threshold, Candidate child nodes Historical baseline residual current To prevent extremely small positive numbers with a denominator of zero, This indicates that the independent variable is truncated to the interval [0,1]. A score greater than 0 indicates that the current residual current of the candidate child node has exceeded its background level, and the closer it is to 1, the higher the degree of limitation.

[0082] (2) Duration score

[0083] The duration score reflects the persistence of continuous overshooting of the node's residual current:

[0084] in, Candidate child nodes The number of consecutive out-of-limit windows, where N is the duration window threshold specified in the joint criterion. N is determined by the following formula:

[0085] in, For the amplitude limiting function, when Time to take ,when Time to take Otherwise take itself; It is a rounding function; The duration of the window is determined in seconds; The duration threshold is preferably between 0.30s and 0.60s. This applies when the number of consecutive windows exceeds the limit... Reaching or exceeding When the duration is 1, the score is 1; otherwise, it is 0. This value eliminates single-transfer impacts while ensuring that the positioning judgment is completed within the allowable range of total road coordination delay.

[0086] (3) Relevance Consistency Score

[0087] The relevant consistency score reflects the node with its parent node The degree of relative voltage phase difference between them:

[0088] in, and Candidate child nodes and corresponding parent node The relative voltage phase, As a phase winding operator, it maps the phase difference to Within the range; The candidate child node is located at the th The phase difference tolerance of each level is calculated using the following formula:

[0089] In the formula, Based on phase tolerance, preferred to ; The hierarchical increment coefficient is preferred. to ; The level number of the current candidate child node. ; Candidate child nodes The sampling timestamp; For the corresponding parent node Sampling timestamp; This is a timestamp offset compensation coefficient used to compensate for communication or synchronization errors, preferably 0.05 to 0.15 (° / ms). For the amplitude limiting function, when Time to take ,when Time to take Otherwise take It itself; upper limit value This represents the absolute upper limit of the phase difference tolerance. In this formula, the base tolerance... With each level Increasing and linearly relaxing, the increment is from Characterization; simultaneously, timestamp deviation pass This is converted into additional tolerance. The deeper the hierarchy, the longer the route, or the greater the timestamp deviation, the more lenient the tolerance should be, but it should not exceed [a certain limit]. By adopting this hierarchical adaptive mechanism, the near-end node maintains a high sensitivity for synchronization discrimination, while the far-end node is allowed a larger range of phase difference changes, avoiding misjudgment at the far end due to the accumulation of line impedance.

[0090] (4) Relevance score between superiors and subordinates

[0091] The score of the correlation between superiors and subordinates reflects the node with its parent node The degree of similarity between the residual current waveforms

[0092] in, Candidate child nodes With the corresponding parent node The correlation between the residual current between upper and lower levels The candidate child node is located at the th The relevance threshold for each level is set as follows: 0.70 to 0.80 for the first-level branch layer, 0.75 to 0.85 for the meter box layer, and 0.80 to 0.90 for the terminal visible node layer. For shallow branches with more load superposition, a lower threshold is used to avoid missed detections; for terminal nodes with fewer background branches, a higher threshold is used to avoid misselection of adjacent branches. This indicates that the independent variable is truncated to the interval [0,1]. The closer the score is to 1, the higher the correlation between the superior and subordinate levels.

[0093] The four scores described above characterize the abnormal features of candidate child nodes from four dimensions: anomaly intensity, persistence, phase source, and waveform similarity.

[0094] However, in scenarios with multiple branches running side-by-side, relying solely on the above scoring may still misclassify adjacent background leakage branches as faulty paths, as background leakage branches may also exhibit some correlation. Therefore, a parent-child differential contribution is introduced. This is used to determine whether the abnormal increment of the parent node is mainly explained by the candidate child nodes and their visible sibling nodes, avoiding the misselection of adjacent background leakage branches as faulty branches based solely on the correlation coefficient:

[0095] in, and Candidate child nodes with its parent node The residual current increases positively before and after the fault. For the first The hierarchical differential tolerance is preferably between 0.10 and 0.30. The differential imbalance is calculated using the following formula:

[0096] in, parent node The set of all candidate child nodes that pass the joint criterion; For set Any candidate child node The residual current increases positively before and after the fault. Candidate child nodes The corresponding positive increment, when belong hour, That is, the above. One of them; parent node The positive increment, For the minimum effective increment, 5mA to 20mA is preferred; ε is a very small positive number to prevent the denominator from being zero. The smaller the value, the more significant the contribution of the candidate child node to the abnormal increment of the parent node. / The larger the value, the more likely it is to be a candidate node. The higher the contribution to the abnormal increment of the parent node.

[0097] The positive increment of residual current before and after a fault, as described in this application, refers to the non-negative difference between the average effective value of residual current within the post-fault confirmation window and the average effective value of residual current within the pre-fault baseline window. Specifically, the average effective value of residual current within the pre-fault baseline window of a node is preferably the average effective value of residual current within 3 to 10 normal judgment windows before fault confirmation, and the average effective value of residual current within the post-fault confirmation window of a node is preferably the average effective value of residual current within N consecutive judgment windows after fault confirmation. When the pre-fault baseline window is missing, the average effective value of residual current within the pre-fault baseline window of a node can be the historical baseline residual current of that node. If the difference between the average effective value of residual current within the post-fault confirmation window and the average effective value of residual current within the pre-fault baseline window of a node is less than 0, then the positive increment of residual current before and after the fault is 0.

[0098] For example, parent node If the post-fault confirmation window average is 320mA and the pre-fault baseline is 80mA, then... =240mA; Candidate child node If the current increases from 35mA to 220mA, then... =185mA; another sibling child node If the current increases from 20mA to 30mA, then... =10mA. At this time... =195mA, The difference between the positive increment of the parent node and the positive increment of the downstream visible child nodes can be used to determine whether the anomaly of the parent node is mainly contributed by the candidate child nodes.

[0099] After obtaining scores across various dimensions and parent-child differential contributions, a unified decision metric is needed to comprehensively assess the degree of fault suspicion at each node. Therefore, a comprehensive scoring system is introduced. The calculation formula is as follows:

[0100] in, As a joint criterion factor, when the topological path determined in step 3 has a fault, the child nodes of the node on which the fault is based. The value is 0 when the amplitude exceeding the limit condition, duration condition, phase consistency condition, upper and lower level correlation condition, or waveform abrupt change duration condition are not met simultaneously; the value is 1 when all conditions are met simultaneously. Candidate child nodes The depth of the hierarchy This represents the maximum hierarchical depth of the transformer area topology. , , , , and All parameters are dimensionless and can be preset or adaptively updated based on the operating data of the transformer area. (Default) , , , , , . This scoring method is not a simple weighted summation. Instead, after persistence and amplitude gating are established, it incorporates phase consistency, hierarchical correlation, parent-child differential contribution, and hierarchy depth into the location ranking, thus taking into account both the electrical characteristics and topological location of the fault path.

[0101] Overall score The continuous quantitative evaluation results of candidate child nodes are given, and they still need to be compared with the preset hierarchical pruning threshold. The comparison is used to make a pruning or retention decision. Since different levels have different requirements for the granularity of fault detection, a uniform threshold is not suitable: a shallow threshold that is too low will result in retaining too many irrelevant branches, increasing the burden of subsequent traversal; a deep threshold that is too high may miss weak fault characteristic nodes at the end. Therefore, the hierarchical pruning threshold is preferably set hierarchically: the threshold for the first-level branch layer is 0.35 to 0.50, used to quickly eliminate large irrelevant branches with small amplitude contributions and low correlation between upper and lower levels. An irrelevant large branch refers to one whose residual current does not exceed the corresponding threshold, or whose relative voltage phase difference, upper and lower level correlation, or parent-child differential contribution do not reach the hierarchical pruning threshold. The first-level branch; the threshold for the meter box layer is set to 0.50 to 0.65 to filter key meter boxes; the threshold for the user access point or end-visible node layer is set to 0.60 to 0.75 to avoid misjudgment caused by end-background leakage. When Remove the candidate child node and its downstream subtree when the time is right; If the candidate child node is not found, continue searching downwards or identify it as the lowest level abnormal node.

[0102] After the joint criterion screening, scoring calculation, and hierarchical pruning described above, the search space has been converged to at least a few candidate paths. Finally, when determining the faulty segment, if there are still visible child nodes downstream of the retained candidate child node that satisfy the joint criterion, then the candidate child node is used as the new parent node, and the steps of candidate child node extraction, screening, scoring, and pruning are repeated to continue the search downwards; if there are no visible child nodes downstream of the retained candidate child node that satisfy the joint criterion, then the candidate child node is used as the last-level abnormal node, the last-level abnormal node is used as the upstream boundary, and the nearest downstream visible node, meter box outgoing line, or user access point is used as the downstream boundary to form an isolable faulty segment; if there are multiple faulty segments, the priority is determined in the order of hierarchical depth first, parent-child differential contribution second, and comprehensive score third.

[0103] Step 5: Based on the fault section location results determined in Step 4, execute the segmented protection action and feed back the execution results to the system.

[0104] In a preferred but non-limiting embodiment of the present invention, step 5 specifically includes: After the location result is generated, the main control terminal outputs a tripping command to the corresponding intelligent sectionalizing switch. The sectionalizing switch trips and feeds back the tripping status to the main control terminal. To prevent overstepping of the main protection, the preferred action delay for lower-level sectionalizing protection is 80ms to 200ms, and the preferred total coordination delay window is 300ms to 800ms. Furthermore, the total coordination delay should not be less than the sum of the maximum action delay of the lower level, the communication confirmation time, the mechanical tripping time of the switch, and the safety margin; among which, the preferred communication confirmation time is 20ms to 100ms, the preferred mechanical tripping time of the switch is 30ms to 80ms, and the preferred safety margin is 50ms to 150ms. If communication is interrupted or the lower-level status is not returned, the main protection maintains its original protection function and performs backup actions according to the field settings. After the faulty section trips, the non-faulty branches remain closed and powered. During reset, the system first confirms that the residual current of the faulty section is lower than the reset threshold and remains so for at least the preset reset waiting time before allowing manual or remote closing; if two consecutive attempts to close fail, the system enters a locked state.

[0105] More preferably, the reversion waiting time ranges from 30 seconds to 180 seconds; the reversion threshold is 40% to 70% of the fault node action threshold, and the correlation between the upper and lower levels of the same path during the reversion period is lower than the fault correlation threshold, so as to avoid repeated attempts to reconnect when the fault has not been eliminated.

[0106] Step 6: Based on the execution results of Step 5, generate the archive.

[0107] In a preferred but non-limiting embodiment of the present invention, step 6 specifically includes: The system uploads fault records to the cloud, including node number, Peak value, duration, action time, and return state.

[0108] To more clearly illustrate the technical solution and implementation process of the present invention, the technical concept of the present invention will be introduced below with reference to a specific application example.

[0109] A method for residual current pruning and segmented protection in rural low-voltage distribution areas includes the following steps: Taking a 200kVA rural low-voltage distribution area as an example, the low-voltage side has four main branches: A, B, C, and D. Branch A has three meter boxes A1 to A3, branch B has two meter boxes B1 to B2, branch C has four meter boxes C1 to C4, and branch D has five meter boxes D1 to D5. The main distribution box is equipped with one distribution area leakage current collaborative control terminal and one main circuit zero-sequence current transformer. Each branch switch is equipped with a branch acquisition and protection terminal and a smart sectionalizing switch. Meter boxes for wet fishpond pumping stations, seasonal agricultural irrigation loads, and centralized user access are equipped with meter box acquisition terminals. Branch lines of users without access points are registered as invisible downstream sections in the distribution area topology table.

[0110] by Figure 5 Taking the transformer substation shown as an example, the implementation steps are as follows: (1) The control unit reads the topology map of the transformer area and confirms the parent-child relationship of the main node R, primary branches A / B / C / D, meter boxes A1 to A3, B1 to B2, C1 to C4, D1 to D5 and the corresponding sectional switches; (2) The main acquisition unit and each branch acquisition unit acquire the remaining current, voltage phase and switch status using a unified time reference; (3) When the effective value of the residual current of the total circuit R exceeds T0, the system calculates the effective value of the residual current, the fundamental amplitude, the relative voltage phase, the waveform abrupt change, the correlation between the upper and lower levels and the differential contribution between the parent and child branches A / B / C / D respectively, and determines whether the joint criterion is met. (4) If branch A satisfies the joint criterion but branches B, C, and D do not, then prune the subtrees of B, C, and D and continue the search only under branch A; (5) If meter box A1 meets the joint criteria while meter boxes A2 and A3 do not, then A1 is determined as the last-level abnormal node, and the downstream user branch of A1 or the line after the corresponding sectionalizing switch of A1 to the next visible boundary is determined as the fault section. (6) The control unit first sends a trip or lockout command to the corresponding section switch of A1, and then checks after a delay whether the residual current of the main circuit has fallen back below T0; (7) If the fallback is normal, maintain power supply to the non-faulty branch and upload the fault location, waveform characteristics and action record; if the fallback is not normal, continue to search for other visible nodes of branch A according to the topology diagram or upgrade to the upper-level section protection. (8) After the fault is handled, the system will release the lockout and perform power restoration verification by manual confirmation or insulation test qualified signal.

[0111] When insulation failure occurs in the downstream user branch of meter box A1 in branch A, the exemplary sampling results are as follows: the effective value of the residual current of the total circuit R increases from the background value of 80mA to 320mA within 6 consecutive judgment windows; branch A increases from 35mA to 220mA; branches B, C, and D are all below their respective thresholds; meter box A1 increases from 18mA to 155mA; and meter boxes A2 and A3 do not exceed their thresholds. The difference between the relative voltage phase of A1 and branch A is 12 degrees, the correlation between A1 and branch A is 0.88, the parent-child differential contribution is 0.82, and the comprehensive score is higher than the threshold of the same level; the main control terminal outputs the location result of "branch A - downstream section of meter box A1" and drives the downstream sectionalizing switch of A1 to trip, while other branches maintain power supply.

[0112] Under the above-mentioned 200kVA transformer area example parameters, offline playback comparisons were performed on the same fault sequence for the main protection direct action scheme, branch independent protection, and the method of the present invention: the main protection direct action scheme can only provide the fault range at the transformer area level, and the power outage ratio of non-faulty branches is 100%; the branch independent protection scheme can locate the first-level branch, and the power outage ratio of non-faulty branches is about 25% to 50%; the method of the present invention locates the isolable section downstream of the meter box in the fault scenario downstream of A1, and the non-faulty branches maintain power supply. The location calculation is completed in the edge master control terminal, and the feature calculation and pruning search of a single fault event takes less than a decision window.

[0113] The example data above is used to illustrate the coordination relationship between the various criteria of this invention. In actual submission or implementation, the area capacity, number of branches, number of tables, threshold, and playback results can be replaced with on-site ledgers and test records, but this will not affect the technical path of this invention for positioning based on visible nodes, parent-child differential contribution, and hierarchical gating scores.

[0114] The following is a comparison of the accuracy of leakage fault location between the present invention and the prior art.

[0115] (1) Compared with the scheme that relies solely on the operation of the total residual current protection device, the present invention continues to use the synchronous waveform characteristics of the branch and meter box nodes to locate the fault after the main circuit is abnormal, thus avoiding the direct tripping of the main protection device and causing a power outage in the entire area.

[0116] (2) Compared with the scheme of installing independent protectors only in each branch, the present invention can selectively coordinate by using the correlation between upper and lower levels and the differential relationship between parents and children, which can reduce the simultaneous operation or over-level operation of upper and lower level protectors.

[0117] (3) Compared with the manual branch-by-branch test method, the present invention uses topology graphs and hierarchical adaptive pruning to directly provide candidate fault sections, reducing the number of on-site inspections. Since the joint criteria simultaneously constrain the anomaly intensity, persistence, phase source and topology transmission relationship, the system maintains high sensitivity to real grounding leakage, and has stronger suppression capabilities for lightning induction, switching impact, harmonic disturbances and background leakage fluctuations.

[0118] Example 2 Embodiment 2 of the present invention provides a residual current pruning and positioning segmented protection system for rural low-voltage distribution transformer areas. The system, which operates the aforementioned residual current pruning and positioning segmented protection method for rural low-voltage distribution transformer areas, includes: The transformer area topology map construction module: constructs a non-full-scale transformer area topology table based on the necessity of transformer deployment and generates a transformer area topology map; Synchronous sampling and feature extraction module: Calculates the residual current RMS value, fundamental amplitude, relative voltage phase, third and above harmonic content, waveform abrupt change and upper and lower level correlation of each node in the transformer area topology map; Fault type joint criterion module: Based on the data calculated in the synchronous sampling and feature extraction module, a joint criterion is formed according to amplitude exceeding the limit, number of continuous windows, phase consistency, correlation between upper and lower levels, persistence of sudden change and short-term impact interference to determine whether a persistent grounding leakage fault has occurred in the topology path where the deployment node is located; The hierarchical pruning and localization mapping module uses the node on which the fault is determined in the joint fault type criterion module as the parent node and extracts all its candidate child nodes; calculates the comprehensive score of each candidate child node; filters according to the pruning threshold corresponding to the level of each candidate child node and retains the candidate child nodes whose comprehensive score is not less than the pruning threshold; based on the retained candidate child nodes, the last-level abnormal node is obtained, and the fault segment localization result is obtained based on the last-level abnormal node. Segmented protection and reset module: Based on the fault segment location result, output trip or lockout command, and maintain power supply to non-faulty segments after tripping the fault segment; during reset, allow closing after confirming that the residual current is below the threshold, and enter lockout if the closing attempt fails. Event logging and cloud upload module: Generates fault log files based on the execution results of the segmented protection and reversion module, and uploads them to the cloud.

[0119] Example 3 Embodiment 3 of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, it implements the above-mentioned method for residual current pruning and segmented protection in rural low-voltage distribution areas.

[0120] Example 4 Embodiment 4 of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for residual current pruning and segmented protection in rural low-voltage distribution areas.

[0121] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for residual current pruning, positioning, and segmented protection in rural low-voltage distribution areas, characterized in that, Includes the following steps: Step 1: Construct a non-full-scale distribution network topology table for rural low-voltage distribution areas based on the necessity of network deployment and generate a network topology map; Step 2: Calculate the residual current RMS value, fundamental amplitude, relative voltage phase, third and above harmonic content, waveform abrupt change, and upper and lower level correlation of each node in the transformer area topology diagram; Step 3: Based on the data in Step 2, a joint criterion is formed according to amplitude exceeding the limit, duration, phase consistency, correlation between upper and lower levels, persistence of abrupt changes, and short-term impact interference characteristics. If the data corresponding to the node meets the joint criterion, it is determined that a persistent grounding leakage fault has occurred in the topology path where the node is located; otherwise, it is a transient disturbance. Step 4: Using the node on which the fault in the topology path determined in Step 3 is based as the parent node, extract all its child nodes and filter them according to the joint criterion. Child nodes that pass the criterion are recorded as candidate child nodes. Calculate the amplitude score, duration score, phase consistency score, hierarchical correlation score, and parent-child differential contribution with the corresponding parent node for each candidate child node to obtain a comprehensive score for each candidate child node. The parent-child differential contribution is calculated based on the positive increment of the residual current before and after the fault of the candidate child node and the parent node. Filter according to the pruning threshold corresponding to the level of each candidate child node and retain candidate child nodes whose comprehensive score is not less than the pruning threshold. Based on the retained candidate child nodes, the last-level abnormal node is obtained, and the fault section location result is obtained based on the last-level abnormal node. Step 5: Based on the fault section location result, output the trip or lockout command. After the fault section is tripped, the non-fault section is kept powered. During reset, the remaining current is confirmed to be below the threshold before closing is allowed. If the closing attempt fails, the circuit is locked out.

2. The method for residual current pruning, positioning, and segmented protection in rural low-voltage distribution areas according to claim 1, characterized in that: In step 1, the specific method for constructing a non-full-scale distribution area topology table based on the necessity of distribution points is as follows: taking the distribution area transformer as the main node, and the branch nodes of the power supply path between the main node and each end user node are sequentially the first-level to the second-level nodes. Level branch nodes, among which, Subtract 1 from the number of branches of the corresponding power supply path; designate the main node and first-level branch node of the transformer area as mandatory deployment locations; do not designate each end user node as a deployment location; designate the nodes other than the main node, first-level branch node and end user node as preferred deployment locations; The necessity of each optimal placement location is calculated using the following method: The system acquires the following flags: a humid environment flag indicating whether the candidate section is located in a humid environment; a seasonal power load flag indicating whether the candidate section is connected to seasonal power loads; and a distributed photovoltaic flag indicating whether the candidate section is connected to distributed photovoltaic or inverters. Each flag is a binary variable, and its value is 1 when the corresponding condition is met, and 0 otherwise. Calculate the ratio of the length of the candidate segment where the optimal placement location is located to the length of the longest candidate segment among all optimal placement locations to obtain a first ratio; calculate the ratio of the number of downstream users at the optimal placement location to the number of meter box users at all optimal placement locations to obtain a second ratio. The humid environment indicator, seasonal power load indicator, distributed photovoltaic indicator, first ratio and second ratio are weighted and summed to obtain the necessity of the selected location; when the necessity of the location is not less than a set threshold, the location is selected.

3. The method for residual current pruning, positioning, and segmented protection in rural low-voltage distribution areas according to claim 1, characterized in that: In step 2, the method for calculating the correlation between the upper and lower levels is as follows: the Pearson correlation coefficient of the residual current waveform between the node and its upstream adjacent parent node is used as the correlation between the upper and lower levels.

4. The method for residual current pruning, positioning, and segmented protection in rural low-voltage distribution areas according to claim 1, characterized in that: In step 3, the joint criterion includes: The effective value of the total residual current exceeds the total threshold for N consecutive judgment windows, and the fundamental amplitude of the total residual current also exceeds the total fundamental threshold; the effective value of the residual current of the sub-nodes on the same path exceeds the threshold of the corresponding node, and the fundamental amplitude of the residual current of the sub-node also exceeds the fundamental threshold of the corresponding node. The relative voltage phase difference between the child node and the parent node is less than the preset phase difference threshold; The third and higher harmonic content did not exhibit characteristics of lightning pulse or inrush current impact interference. The waveform abrupt change remains in the same direction or continuously exceeds the abrupt change threshold within at least N duration determination windows; The hierarchical correlation between the child node and its parent node is greater than the preset correlation threshold; When the above conditions are met simultaneously, it is determined that there is a persistent grounding leakage fault in the topology path where the node is located; otherwise, it is a transient disturbance.

5. The method for residual current pruning, positioning, and segmented protection in rural low-voltage distribution areas according to claim 1, characterized in that: In step 4, the specific calculation method for the amplitude score is as follows: The difference between the effective value of the residual current of the candidate child node and the preset node threshold of the candidate child node is calculated as the first value; the difference between the preset node threshold of the candidate child node and the residual current of the historical baseline is calculated as the second value; the ratio of the first value to the second value is calculated, and the ratio is truncated to the interval between 0 and 1 to obtain the amplitude score. The specific method for calculating the duration score is as follows: The ratio of the number of consecutive out-of-limit windows of the candidate child node to the duration window number threshold specified in the joint criterion is calculated, and the minimum value of this ratio compared with 1 is taken to obtain the duration score; The specific calculation method for the relevant consistency score is as follows: Calculate the relative voltage phase difference between the candidate child node and its corresponding parent node, and map the phase difference to a preset range using a phase wrapping operator; take the square of the mapped value as the third value; calculate twice the square of the phase difference tolerance of the level where the candidate child node is located, and take it as the fourth value; calculate the ratio of the third value to the fourth value, and take the negative of the ratio as the exponent of the natural constant e; and obtain the correlation consistency score after calculation. The specific calculation method for the superior-subordinate relevance score is as follows: Calculate the hierarchical correlation of the residual current waveform between the candidate child node and its corresponding parent node, and calculate the difference between the hierarchical correlation and the preset correlation threshold in the level where the candidate child node is located, as the fifth value; Calculate the difference between 1 and the aforementioned correlation threshold, and use it as the sixth value; Calculate the ratio of the fifth value to the sixth value, and truncate the ratio to obtain the correlation score between the upper and lower levels; The specific calculation method for the parent-child differential contribution is as follows: Calculate the ratio of the differential imbalance of the candidate child node to the preset differential tolerance in the level where the candidate child node is located. Take the negative of this ratio and use it as the exponent of the natural constant e. The resulting value is the seventh value. Calculate the ratio of the positive increment of the residual current before and after the fault of the candidate child node to the positive increment of the residual current before and after the fault of the corresponding parent node. Truncate this ratio and use it as the eighth value. Multiply the seventh value and the eighth value to obtain the parent-child differential contribution. The specific calculation method for the comprehensive score is as follows: The magnitude score and duration score of the candidate child node are respectively exponentialized and then multiplied to obtain the ninth value; the phase consistency score, superior-inferior correlation score, and parent-child difference contribution of the candidate child node are weighted and calculated to obtain the tenth value; the ratio of the level depth of the candidate child node to the maximum level depth of the transformer area topology is recorded as the normalized level depth, and the product of the set level depth adjustment coefficient and the normalized level depth is incremented by 1 to obtain the eleventh value; the product of the ninth, tenth, and eleventh values ​​is calculated to obtain the comprehensive score of the candidate child node.

6. A method for residual current pruning, positioning, and segmented protection in rural low-voltage distribution areas according to claim 5, characterized in that: The specific method for determining the duration window number in the duration score is as follows: Calculate the ratio of the preset duration threshold to the determination window duration. This ratio is used as the twelfth value. After rounding the twelfth value up, the range is limited to the set range. The resulting integer is the number of duration windows.

7. A method for residual current pruning, positioning, and segmented protection in rural low-voltage distribution areas according to claim 5, characterized in that: The specific calculation method for the phase difference tolerance of the node's level in the relevant consistency score is as follows: Set a basic phase tolerance; calculate the difference between the level number of the candidate child node and 1, and multiply the difference by a preset level increment coefficient as the thirteenth value; calculate the absolute value of the difference between the sampling timestamp of the candidate child node and the sampling timestamp of the corresponding parent node, and multiply the absolute value of the difference by a preset timestamp deviation compensation coefficient as the fourteenth value; add the thirteenth value, the fourteenth value and the basic phase tolerance to obtain the phase difference reference value, and compare the phase difference reference value with the set upper and lower limits of the phase difference tolerance to obtain the phase difference tolerance of the level of the candidate child node.

8. A method for residual current pruning, positioning, and segmented protection in rural low-voltage distribution areas according to claim 5, characterized in that: The specific calculation method for the difference imbalance in the parent-child difference contribution is as follows: The positive increments of residual current before and after the fault of all child nodes under the parent node corresponding to the candidate child node that pass the joint criterion are summed to obtain the summed result; the absolute value of the difference between the positive increment of residual current before and after the fault of the parent node and the summed result is calculated as the fifteenth value. The larger of the positive increment of the residual current before and after the fault of the parent node and the preset minimum effective increment is taken. Calculate the ratio of the fifteenth value to the larger value, and use this ratio as the difference imbalance.

9. A method for residual current pruning, positioning, and segmented protection in rural low-voltage distribution areas according to claim 1, characterized in that: In step 4, the method for determining the lowest-level abnormal node is as follows: If there are still visible child nodes downstream of the retained candidate child node that satisfy the joint criteria, then the candidate child node is used as the new parent node, and the steps of candidate child node extraction, filtering, scoring and pruning are repeated to continue searching downwards; if there are no visible child nodes downstream of the retained candidate child node that satisfy the joint criteria, then the candidate child node is used as the last-level abnormal node. The method for obtaining the fault section location result is as follows: Using the last-level abnormal node as the upstream boundary and the nearest downstream visible node, meter box outgoing line, or user access point as the downstream boundary, an isolable fault section is formed. If there are multiple fault sections, the priority is determined in the following order: first, the level depth; second, the parent-child differential contribution; and third, the comprehensive score.

10. A method for residual current pruning, positioning, and segmented protection in rural low-voltage distribution areas according to claim 1, characterized in that: The segmented protection method further includes step 6, which generates a fault record file containing the fault location, action time and reset status based on the fault segment location result and the execution result of the segmented protection action, and uploads the fault record file to the cloud server.

11. A residual current pruning and positioning segmented protection system for rural low-voltage distribution areas, operating the residual current pruning and positioning segmented protection method for rural low-voltage distribution areas as described in any one of claims 1 to 10, characterized in that, include: The transformer area topology map construction module: constructs a non-full-scale transformer area topology table based on the necessity of transformer deployment and generates a transformer area topology map; Synchronous sampling and feature extraction module: Calculates the residual current RMS value, fundamental amplitude, relative voltage phase, third and above harmonic content, waveform abrupt change and upper and lower level correlation of each node in the transformer area topology map; Fault type joint criterion module: Based on the data calculated in the synchronous sampling and feature extraction module, a joint criterion is formed according to amplitude exceeding the limit, number of continuous windows, phase consistency, correlation between upper and lower levels, persistence of sudden change and short-term impact interference to determine whether a persistent grounding leakage fault has occurred in the topology path where the deployment node is located; Hierarchical pruning and localization mapping module: Using the node on which the fault is determined in the joint fault type judgment module is based as the parent node, extract all its candidate child nodes; calculate the comprehensive score of each candidate child node; filter according to the pruning threshold corresponding to the level of each candidate child node, and retain candidate child nodes whose comprehensive score is not less than the pruning threshold. Based on the retained candidate child nodes, the last-level abnormal node is obtained, and the fault section location result is obtained based on the last-level abnormal node. Segmented protection and reset module: Based on the fault segment location result, output trip or lockout command, and maintain power supply to non-faulty segments after tripping the fault segment; during reset, allow closing after confirming that the residual current is below the threshold, and enter lockout if the closing attempt fails. Event logging and cloud upload module: Generates fault log files based on the execution results of the segmented protection and reversion module, and uploads them to the cloud.

12. A terminal, comprising a processor and a storage medium, characterized in that: The storage medium is used to store instructions; the processor is used to execute the method according to any one of claims 1 to 10 according to the instructions.

13. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by the processor, it implements the method described in any one of claims 1 to 10.

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