Distribution network line fault positioning method and system

Abstract

The embodiment of the invention provides a distribution network line fault positioning method and system, and the method comprises the steps: determining a fault phase, and calibrating a fault moment; dividing the multi-branch line into a line partition and a branch line partition based on the distribution network topology; screening a target fault phase, calculating a fault phase current difference of adjacent detection points, and calculating a current abrupt change rate based on the fault phase current difference of the adjacent detection points; according to the arc suppression coil type and the fault transition resistance value, performing fitting to generate a partition threshold value; a suspected fault section is obtained according to the section threshold initial judgment section; calling a current abrupt change rate time sequence curve of upstream and downstream nodes of the suspected fault section, and checking a current difference amplitude change trend before and after the fault; for multi-branch topology, interference is eliminated through relevance of current abrupt change rates of a main line and branch lines, and finally a target fault section is locked. According to the invention, the problems of weak fault characteristic quantity and poor positioning reliability in a small current grounding mode can be effectively solved.

Description

Technical Field

[0001] This manual relates to the field of distribution network line fault diagnosis, and in particular to a method for locating distribution network line faults. Background Technology

[0002] The distribution network is the core link connecting the main grid and end users in the power system, and its operational reliability directly affects the stability of power supply. Statistics show that over 95% of power outages originate from distribution network faults, with 70% of these caused by single-phase grounding faults or busbar faults. To avoid direct power interruption due to single-phase grounding faults, domestic and international distribution networks often adopt a non-effective grounding (low-current grounding) mode for the neutral point. However, under this mode, the fault characteristic quantities are extremely weak, resulting in a long-standing lack of reliable solutions for fault location and section positioning, making it difficult to meet the increasingly stringent requirements for distribution network automation and power supply reliability.

[0003] Current methods for locating fault sections in distribution networks mainly fall into two categories, both with significant limitations: one is the signal injection method, such as the "S" injection method and the AC / DC integrated injection method. These methods require manually injecting electrical signals into the system, which can interfere with the normal operation of the distribution network and cannot effectively detect transient or intermittent grounding faults, limiting their applicability. The other category is location methods based on fault characteristic quantities, including the zero-mode current comparison method, the zero-sequence reactive power direction method, and the traveling wave method. These methods generally suffer from technical bottlenecks. Not only do the timing errors of the distribution automation system's FTUs reach the millisecond level, causing transient signal-based location algorithms to fail, but they also rely solely on post-fault data, lacking pre-fault baseline comparisons, making them prone to misjudgment in low-current grounding scenarios. Furthermore, most solutions rely on zero-sequence current, requiring the collection of three-phase data, which places high demands on the instrument transformers and is prone to failure due to missing phase data, resulting in high hardware and data acquisition costs. In summary, existing technologies are insufficient to meet the precise location requirements of single-phase grounding faults in low-current grounding systems, necessitating innovative technical solutions to overcome industry bottlenecks. Summary of the Invention

[0004] This specification provides one or more embodiments of a method for locating faults in a distribution network line, the method comprising:

[0005] After the system detects a ground fault, it determines the faulty phase by observing the variation pattern of the three-phase voltage amplitude; it calibrates the fault time by combining the time sequence intersection of the phase voltage change moment and the arc suppression device power change moment; and it divides the multi-branch lines into main line zones and branch line zones based on the distribution network topology and assigns independent location identifiers.

[0006] Select the target faulty phase and extract the corresponding current waveform data, then calculate the current difference between the faulty phases at adjacent detection points. ,in Where n is negative to indicate before the fault and n is positive to indicate after the fault, and N is the number of sampling points in one power frequency cycle; the main line current change rate is calculated based on the fault phase current difference between adjacent detection points. and branch line current mutation rate ;

[0007] Based on the arc suppression coil type and fault transition resistance value, a main line partition threshold is fitted and generated. and branch line partition threshold Compare the stratified current mutation rate with the corresponding partition threshold, if and If the section is not faulty, it is considered a suspected faulty section; otherwise, it is considered a non-faulty section.

[0008] The current mutation rate time series curves of upstream and downstream nodes of the suspected fault section are retrieved to verify the trend of current difference amplitude change before and after the fault. For multi-branch topologies, interference is eliminated by the correlation between the current mutation rates of the main line and the branch lines, and the target fault section is finally located.

[0009] In some embodiments, dividing multi-branch lines into main line partitions and branch line partitions based on the distribution network topology includes:

[0010] Starting from the outgoing line end of the distribution network substation, the line segment extending along the main power transmission path to the end of the trunk line is divided into main line sections; starting from each branch node on the main line, the line segment extending to the end of the branch line is divided into branch line sections, and each branch line section is associated with a corresponding main line branch node.

[0011] In some embodiments, the formulas for calculating the main line current mutation rate and the branch line current mutation rate are as follows:

[0012] ;

[0013] ;

[0014] in, The difference in fault phase current between adjacent detection points on the main line. The difference in fault phase current between adjacent detection points on a branch line.

[0015] In some embodiments, the calculation of the fault transition resistance value includes:

[0016] Detect the effective value of the fault phase voltage at the time of the fault. and the effective value of residual current at the fault point Through formula The fault transition resistance value was calculated, where the residual current at the fault point was derived by subtracting the load current and the capacitance current to ground from the fault phase current.

[0017] In some embodiments, verifying the trend of the change in current difference amplitude before and after the fault, and eliminating interference through the correlation between the current change rate of the main line and the branch line, includes:

[0018] Amplitude trend verification: If the current difference amplitude after a section fault increases by a first preset threshold or more than before the fault, it is determined to meet the amplitude characteristics of a fault section; if the amplitude decreases or the increase is less than the second preset threshold, it is determined to be a non-fault section characteristic.

[0019] Multi-branch interference elimination: When a branch line section is identified as a suspected fault section, the current change rate upstream and downstream of the corresponding main line branch node is checked. If the current change rate of the main line section does not reach the threshold, the branch line is locked as a fault section. If the current change rate of the main line section reaches the threshold, the influence of current disturbance of the branch line is eliminated by combining the current flow direction of the branch node before the main line fault section is determined.

[0020] This specification provides one or more embodiments of a power distribution line fault location system, the system comprising:

[0021] Fault identification module: After the system detects a ground fault, it collects the real-time amplitude of the three-phase voltage and compares it with the change pattern of its normal operating reference amplitude to determine the faulty phase with abnormal voltage; at the same time, it extracts the moment of sudden change in phase voltage and the moment of sudden change in power of the arc suppression device, and calibrates the precise fault moment by the intersection of the two time series, providing a basic time and phase reference for subsequent fault location.

[0022] Topology Identification Module: Used to retrieve real-time distribution network topology data and divide multi-branch lines into main line zones and branch line zones according to the power transmission path hierarchy;

[0023] Calculation module: Used to filter target fault phase currents and extract valid waveform data, first according to the formula. Calculate the fault phase current difference between adjacent detection points, where Where n is negative to represent before the fault and n is positive to represent after the fault, and N is the number of sampling points per power frequency cycle; then, based on the current difference data before and after the fault, the main line current change rate is calculated respectively. and branch line current mutation rate This forms a quantitative indicator of fault characteristics.

[0024] Fault Section Determination Module: This module first adjusts the arc-removal coil type and fault transition resistance value, and then generates main line section thresholds by fitting historical fault condition data. and branch line partition threshold The method compares the stratified current mutation rate with the corresponding threshold to determine the suspected fault section; then retrieves the current mutation rate time series curves of upstream and downstream nodes of the suspected fault section to verify the change trend of the current difference amplitude before and after the fault; at the same time, for multi-branch topology, the method establishes a correlation model between the current mutation rate of the main line and the branch line to eliminate the interference of branch current disturbance, and finally locks the target fault section. Attached Figure Description

[0025] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein:

[0026] Figure 1 This is an exemplary flowchart of a method for locating faults in distribution network lines according to some embodiments of this specification;

[0027] Figure 2 This is an exemplary block diagram of a power distribution line fault location system according to some embodiments of this specification. Detailed Implementation

[0028] To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0029] It should be understood that the terms "system," "unit," and / or "module" used herein are a method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0030] Unless the context clearly indicates an exception, words such as "a," "an," "a kind," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0031] Flowcharts are used in this specification to illustrate the operations performed by the system according to embodiments of this specification. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0032] Example 1: Figure 1 This is an exemplary flowchart of a power distribution line fault location method according to some embodiments of this specification. Figure 1 As shown, the method for locating faults in distribution network lines includes:

[0033] After detecting a ground fault, the system determines the faulty phase by analyzing the variation patterns of the three-phase voltage amplitude; and calibrates the fault timing by combining the time-series intersection of the phase voltage abrupt change and the arc suppression device power abrupt change. ;

[0034] A faulty phase refers to a transmission line phase in which a single-phase ground fault occurs in the distribution network, and the electrical quantities show significant abnormalities, manifested as a large decrease in phase voltage and a large increase in the voltage of the other two phases. It is the core phase reference for fault location.

[0035] Voltage reference value A reference threshold value is used to determine the degree of voltage abnormality in a faulty phase. The three-phase voltage amplitude can be collected by the three-phase voltage transformer on the substation bus and calculated by arithmetic average.

[0036] In some embodiments, various voltage reference values ​​can be established first when the distribution network is operating normally. After the zero-sequence voltage of the bus triggers the ground fault detection, the fault phase is initially determined by the amplitude characteristics of the three-phase voltage drop and rise. Then, the voltage data of 3 power frequency cycles is used for secondary verification to finally determine the fault phase.

[0037] In some embodiments, the moment of voltage change in the fault phase is first extracted. and the moment of sudden power change in the arc suppression device Then, by combining the time intersection interval of the two and the interval duration, the fault time is determined and finally marked. .

[0038] Based on the distribution network topology, multi-branch lines are divided into main line zones and branch line zones and assigned independent location identifiers.

[0039] The method of dividing multi-branch lines into main line partitions and branch line partitions based on distribution network topology includes:

[0040] Starting from the outgoing line end of the distribution network substation, the line segment extending along the main power transmission path to the end of the trunk line is divided into main line sections; starting from each branch node on the main line, the line segment extending to the end of the branch line is divided into branch line sections, and each branch line section is associated with a corresponding main line branch node.

[0041] Distribution network topology is the overall architecture of the connection relationships and power transmission paths of various lines, nodes, and switching devices in a distribution network system, and it serves as the basis for line zoning. In some embodiments, the complete topology of the current lines can be synchronously obtained from the distribution network GIS system.

[0042] Starting from the outgoing line end of the substation, the main power transmission path is extended to the end of the line. All line segments from the outgoing line end to the last node of the main line (nodes with no subsequent main path extension) along this path are integrated and delineated as the main line partition. At the same time, the start and end nodes and key section switches of the main line partition are marked.

[0043] Each branch node on the main line is identified one by one. Taking each branch node as an independent starting point, the line segment extending from that node to the corresponding end load node of the branch line is defined as a branch line partition. One branch node corresponds to one independent branch line partition to avoid overlapping partition ranges.

[0044] Each branch line partition is bound to its corresponding main line branch node code, forming an association mapping of "main line partition - branch node - branch line partition", which ensures that the main line segment corresponding to the branch line can be quickly traced during subsequent fault location.

[0045] Screening and detection device in Within the interval, 2N target fault phases are identified and their corresponding current waveform data are extracted. The current difference between fault phases at adjacent detection points is then calculated. ,in Where n is negative to indicate before the fault and n is positive to indicate after the fault, and N is the number of sampling points in one cycle of power frequency;

[0046] The fault phase current waveform data is a time-series sampled value of the fault phase line current changing over time, collected by the detection device. It is the core raw data for calculating the current change rate.

[0047] The main line current change rate is calculated based on the fault phase current difference between adjacent detection points. and branch line current mutation rate .

[0048] The formulas for calculating the main line current mutation rate and the branch line current mutation rate are as follows:

[0049] ;

[0050] ;

[0051] Among them, is the fault phase current difference between adjacent detection points on the main line, and is the fault phase current difference between adjacent detection points on the branch line.

[0052] The main line current mutation rate is the ratio of the effective value of the phase current difference before and after a fault in the main line section. It is used to quantify the change in the current fluctuation amplitude caused by a fault in the main line section and is a core characteristic indicator for determining whether the main line is a fault section.

[0053] The branch line current mutation rate is the ratio of the effective value of the difference between the current of the fault phase after the fault and the current before the fault within the branch line section. It is used to quantify the change in the current fluctuation amplitude caused by the fault in the branch line section and is a core characteristic indicator for determining whether a branch line is a fault section.

[0054] Based on the arc suppression coil type and fault transition resistance value, a main line partition threshold is fitted and generated. and branch line partition threshold ;

[0055] Arc suppression coil type refers to the inherent adjustment type of distribution network grounding fault compensation equipment, which is divided into pre-adjusted type (inductance is set before the fault and no adjustment is made after the fault) and follow-up type (inductance is dynamically adjusted after the fault). The difference in their impedance characteristics will affect the amplitude of the fault current change.

[0056] The fault transition resistance value refers to the equivalent resistance of the grounding channel at the fault point. Its resistance value will change the amplitude and sudden change pattern of the fault current, and is a key operating condition parameter that affects the threshold for determining the current sudden change rate.

[0057] In some embodiments, the calculation of the fault transition resistance value includes:

[0058] Detect the effective value of the fault phase voltage at the time of the fault. and the effective value of residual current at the fault point Through formula The fault transition resistance value was calculated, where the residual current at the fault point was derived by subtracting the load current and the capacitance current to ground from the fault phase current.

[0059] The calculation of the fault transition resistance value relies on the electrical parameter calculation module of the distribution network fault location system. First, the basic electrical quantities at the time of the fault are collected and calculated: retrieve the fault time... The timing data of the fault phase voltage within the power frequency cycle is sampled and analyzed using the effective value formula. Calculate the effective value of the fault phase voltage Simultaneously, the synchronous current timing data is obtained through the fault phase current transformer, and the effective value of the total fault phase current is calculated.

[0060] Then, non-fault-related current components are deducted sequentially to obtain the residual current at the fault point: first, the average load current of the faulty phase line within the 10 power frequency cycles prior to the fault is retrieved from the distribution network load monitoring database (the median is taken when the load fluctuates) as... ,from Subtracting this component yields the preliminary fault-related current. Then, based on the line parameters, through Calculate the capacitance current to ground ,in, C represents the total capacitance to ground of the fault. The normal operating voltage reference value, from Further deductions Obtain the actual residual flow at the fault point Finally, substitute After completing the calculation, the system will compare the result with the common fault resistance range of 0~2kΩ in distribution networks. If the result exceeds this range, verification will be performed. and The accuracy of the values ​​is determined and the calculation is corrected and recalculated to ensure the validity of the results.

[0061] For example, with the goal of "maximizing the distinguishability between faulty and non-faulty sections", the minimum value of the main line current change rate in the faulty section is extracted from the matched sample subset. The maximum value of the main line change rate in non-faulty sections Calculate the initial threshold of the main line by taking the average value. Branch line threshold Calculate using the same logic.

[0062] Based on historical data statistics, in the scenario of pre-tuned arc suppression coils, the main circuit Approximately 1.2 Approximately 1.3, therefore Branch lines Approximately 1.3 Approximately 1.4, therefore In the context of variable-frequency operation, the corresponding values ​​for the main circuit are 1.3 and 1.4. The branch lines are 1.4 and 1.5. .

[0063] Threshold range definition and resistor adaptation: To improve fault tolerance, a floating range of ±0.05 is added based on the initial threshold, forming the basic threshold range: pre-tuned main circuit. Branch lines ; Main line under adjustment Branch lines When the fault transition resistance value is greater than 500Ω, the high resistance characteristic will cause the current change amplitude to decrease. At this time, the lower limit of the threshold range is increased by 0.05, that is, the pre-adjusted main line K1 is adjusted to [1.25, 1.3], and the branch line K2 is adjusted to [1.35, 1.4]; the follow-up adjustment main line K1 is adjusted to [1.35, 1.4], and the branch line K2 is adjusted to [1.45, 1.5], to ensure that the high resistance fault will not be missed due to the decrease in change rate.

[0064] A 20% subset of the matched samples is randomly selected as the validation set. The fitted K1 and K2 values ​​are then used for validation. If the accuracy rate for identifying faulty sections of the main / branch lines is ≥95%, and the false positive rate for non-faulty sections is ≤3%, the threshold is confirmed as valid and output. If the target is not met, additional samples under the same operating conditions are added to a total of 50 or more, and the fitting operation is re-executed. If the accuracy requirement is still not met, the initial threshold calculation method is adjusted (e.g., a weighted average method is used, with the weight of faulty samples set to 0.6 and the weight of non-faulty samples set to 0.4) until the accuracy standard is met. The validated threshold is stored in association with the current operating condition parameters, providing a reliable benchmark for subsequent mutation rate comparisons.

[0065] Compare the stratified current mutation rate with the corresponding partition threshold. If the threshold is equal to or greater than the threshold, the section is identified as a suspected fault section; otherwise, it is a non-fault section.

[0066] It should be noted that the hierarchical current mutation rate includes the main line current mutation rate. and branch line current mutation rate .

[0067] The current mutation rate time series curves of upstream and downstream nodes of the suspected fault section are retrieved to verify the trend of current difference amplitude change before and after the fault. For multi-branch topologies, interference is eliminated by the correlation between the current mutation rates of the main line and the branch lines, and the target fault section is finally located.

[0068] In some embodiments, verifying the trend of the change in current difference amplitude before and after the fault, and eliminating interference through the correlation between the current change rate of the main line and the branch line, includes:

[0069] Amplitude trend verification: If the current difference amplitude after a section fault increases by a first preset threshold or more than before the fault, it is determined to meet the amplitude characteristics of a fault section; if the amplitude decreases or the increase is less than the second preset threshold, it is determined to be a non-fault section characteristic.

[0070] Multi-branch interference elimination: When a branch line section is identified as a suspected fault section, the current change rate upstream and downstream of the corresponding main line branch node is checked. If the current change rate of the main line section does not reach the threshold, the branch line is locked as a fault section. If the current change rate of the main line section reaches the threshold, the influence of current disturbance of the branch line is eliminated by combining the current flow direction of the branch node before the main line fault section is determined.

[0071] For example, the first preset threshold is 30%, and the second preset threshold is 10%.

[0072] Before extracting the fault and after the fault The current difference time series data of the two intervals are used to calculate the average amplitude current before the fault and the average amplitude current after the fault, respectively.

[0073] Calculate the amplitude increase and trend judgment: Calculate the amplitude increase ΔI by the difference between the average amplitude current before the fault and the average amplitude current after the fault. If ΔI ≥ ΔI1, it means that the current fluctuation amplitude has increased significantly after the fault, which is judged to be consistent with the amplitude characteristics of the fault section, and forms a positive confirmation with the current change rate judgment result.

[0074] If ΔI < 0 (amplitude decreases) or 0 ≤ ΔI < ΔI2 (e.g., < 0.6A, insufficient increase), it indicates that the current change is caused by non-fault factors (e.g., load fluctuations), and is determined to be a non-fault section characteristic, triggering a review of the current mutation rate determination result;

[0075] If ΔI2≤ΔI<ΔI1 (e.g., 0.6A≤ΔI<2A), it is marked as having blurred amplitude characteristics, and further judgment is needed in conjunction with subsequent multi-branch interference elimination.

[0076] Furthermore, when the fault transition resistance When the fault current amplitude decreases, the first preset threshold and the second preset threshold are corrected by 1.1 times; when the arc suppression coil is adjustable, ΔI1 is corrected by 0.5 times due to the current compensation effect after the fault, to ensure the adaptability of the threshold under different operating conditions.

[0077] Triggering conditions and data preparation: When a branch line section (e.g., branch B) is identified as a suspected fault section (A2 > K2), the interference elimination process is immediately triggered. Data from the upstream and downstream detection devices of the corresponding main line node of that branch is retrieved, and calculations are performed. (Upstream mutation rate) and (Downstream mutation rate).

[0078] Scenario 1: Main line does not reach threshold - lock branch as interference / fault source: ① The upstream and downstream change rate of the main line does not exceed the limit, indicating that the fault current is not conducted from the main line to the branch, and the branch's A2>K2 is caused by its own disturbance; ② Further check the amplitude trend of the branch: if the branch ΔI≥ΔI1, the branch is determined to be a "fault section" (such as the branch line insulation failure grounding); if the branch ΔI<ΔI2, it is determined to be "branch load disturbance", the suspected fault mark of the branch is removed, and the main line and other branches are maintained as non-fault.

[0079] Scenario 2: Main line reaches threshold – interference removal based on current flow direction: ① Determine current flow direction: Determine by the phase difference φ between current and voltage at branch nodes. Current flows from the main line to the branch (forward); if ① Current flows from the branch to the main line (reverse direction); ② Forward flow: This indicates a fault in the main line. The A2 of the branch is greater than the second preset threshold due to fault current conduction. Eliminate branch interference and determine the main line. The upstream section is a suspected fault section; ③ Reverse flow: This indicates strong interference in the branch (such as the start-up and shutdown of a large load on the branch), which can be confirmed by formula. Correcting the main circuit mutation rate, among which, This is the corrected main circuit mutation rate. The measured main line abrupt change rate is given, and k is the branch interference propagation coefficient, typically taken as 0.8. If corrected... If the value is greater than the first preset threshold, the main line is determined to be a suspected faulty section; otherwise, the main line fault is ruled out.

[0080] Multi-branch collaborative judgment: If A2 is greater than the second preset threshold in multiple branches associated with the main line, the interference of each branch is stripped off one by one according to the logic of "first checking the current flow direction and then calculating the interference transmission coefficient", so as to finally obtain the pure mutation rate of the main line and ensure that the fault section judgment is not affected by the superimposed interference of multiple branches.

[0081] For example, consider the location of a single-phase grounding fault in a 10kV multi-control network:

[0082] This embodiment uses a 10kV radial multi-branch distribution network line in a prefecture-level city as an application scenario. This line employs a low-current grounding system and is equipped with a pre-adjusted arc suppression coil. The main line is 8km long, including two branch lines (Branch 1 is 2.5km long and Branch 2 is 3km long). Synchronous detection devices (sampling frequency 20kHz, GPS timing deviation ≤1ms) are deployed at key nodes of the line. The following section, combined with a real-world fault scenario, details the implementation process of the distribution network line fault location method.

[0083] Basic fault information is determined: fault phase, fault time, and topology partition.

[0084] Fault phase identification and fault time t1 calibration: The system collects voltage data in real time through the three-phase voltage transformers on the substation bus. Under normal operation, the reference voltage value of each phase is... When zero-sequence voltage is detected When there are 2 consecutive sampling points, a ground fault response is triggered, and the real-time amplitude of the three-phase voltage is retrieved simultaneously. , , Based on the "one decrease and two increases" characteristic (C-phase voltage) Phase A and B voltages Initially, it was determined that phase C was the faulty phase; after continuously collecting data for 3 power frequency cycles for verification, it was confirmed that the voltage of phase C was consistently low, and the faulty phase was finally identified as phase C.

[0085] Then, the timing of the voltage jump in the fault phase and the timing of the power jump in the arc suppression device were extracted:

[0086] Phase voltage sudden change moment: The time of the first sampling point when the C phase voltage suddenly drops from 5.75kV to 2.3kV is 15:32:40.001s;

[0087] Arc suppression device power sudden change moment The first sampling point time when the arc suppression device power jumps from 420W to 2080W is 15:32:40.003s; the intersection of the two time series is [15:32:40.001s, 15:32:40.003s], with a duration of 2ms≤5ms. The midpoint of the interval, 15:32:40.002s, is taken as the fault time. .

[0088] The topology-based line partitioning and identifier allocation retrieves real-time topology data from the distribution network GIS system and completes the partitioning according to the above rules:

[0089] Main line zoning: Starting from the outgoing line end of the substation, along the main power transmission path to the end of the main line, it is divided into 3 sub-zones, which are respectively assigned the labels "Z-10kV-01-001" (outgoing line end - node A, 2km), "Z-10kV-01-002" (node ​​A - node B, 3km), and "Z-10kV-01-003" (node ​​B - end of the main line, 3km);

[0090] Branch line partitioning: Starting from the main line node A and ending at the end of branch 1, the area is divided into branch 1 partition (identified as "F-10kV-01-001"), associated with the main line node A; starting from the main line node B and ending at the end of branch 2, the area is divided into branch 2 partition (identified as "F-10kV-01-002"), associated with the main line node B.

[0091] Fault Feature Quantification: Current Difference Calculation and Current Sudden Change Rate Calculation

[0092] Current data filtering and current difference calculation: Based on this, the detection devices were screened in [15:32:39.982]. s 15:32:40.022 s The current data within the interval covers one power frequency cycle (0.02s) before the fault and one power frequency cycle after the fault. The sampling frequency is 20kHz, and the number of sampling points N=400 per power frequency cycle is used. Therefore, a total of 2N=800 valid C-phase current data are extracted.

[0093] According to the formula Calculate the current difference between adjacent detection points ( The current at the upstream detection point. For downstream detection point current, (The negative sign indicates the state before the fault).

[0094] Main line “Z-10kV-01-002” section (node ​​A - node B): when n=-100, , ,have to When n=100, , ,have to ;

[0095] Branch 1 partition “F-10kV-01-001”: when n=-50, , ,have to When n=50, , ,have to .

[0096] Current mutation rate calculation: Based on the formula given in the abstract, calculate the current mutation rate of the main line and branch lines respectively:

[0097] Main line abrupt change rate (taking “Z-10kV-01-002” zone as an example): Effective value of current difference after fault: ; ◦ Effective value of current difference before the fault: Mutation rate: .

[0098] Branch 1 Sudden Change Rate: Effective value of current difference after fault: Effective value of current difference before the fault: Mutation rate: Branch 2 partition calculation yields... The values ​​of other sections of the main line are all ≤1.2.

[0099] Preliminary assessment of suspected faulty sections: Threshold fitting and mutation rate comparison:

[0100] Key operating parameters: Arc suppression coil type is "pre-adjusted", fault transition resistance. (through , (Calculated). Thresholds are generated by fitting the historical sample library: Main line partition threshold. Branch line partition threshold .

[0101] Comparison results: Main line “Z-10kV-01-002” section Branch 1 partition ,satisfy" and The section marked "" was identified as a suspected faulty section; all other sections were non-faulty sections.

[0102] Precise positioning: amplitude trend verification and multi-branch interference elimination.

[0103] Verification of the trend of current difference amplitude before and after the fault: First preset threshold = average current difference amplitude before the fault × 30%, second preset threshold = average current difference amplitude before the fault × 10%, and the verification is performed on the suspected fault section respectively:

[0104] Main line “Z-10kV-01-002” zone verification:

[0105] Basic parameters: Average current difference before fault = 0.32A, first preset threshold. The second preset threshold ;

[0106] Amplitude change calculation: Average amplitude of current difference after fault = 0.45A, amplitude increase = 0.45A - 0.32A = 0.13A;

[0107] Feature determination: Since 0.13A ≥ 0.096A ​​(first preset threshold), the partition is determined to meet the amplitude characteristics of the fault section.

[0108] Branch 1 partition “F-10kV-01-001” verification:

[0109] Basic parameters: Average current difference before fault = 0.28A, first preset threshold. The second preset threshold ;

[0110] Amplitude change calculation: Average amplitude of current difference after fault = 0.43A, amplitude increase = 0.43A - 0.28A = 0.15A;

[0111] Feature determination: Since 0.15A ≥ 0.084A (first preset threshold), the partition is determined to meet the amplitude characteristics of the fault section.

[0112] If a certain section shows an amplitude increase of 0.05A (lower than the first preset threshold of 0.096A, but higher than the second preset threshold of 0.032A), the system will mark it as "ambiguous amplitude feature" and further judgment will be required based on the subsequent interference elimination results; if the amplitude increase is 0.02A (lower than the second preset threshold), it will be directly judged as a non-faulty section feature.

[0113] Multi-branch interference elimination:

[0114] Using a suspected fault in branch 1 as the trigger condition, verify the upstream and downstream abrupt change rate and current flow direction of main line branch node A. Specific procedure:

[0115] Main line mutation rate verification: retrieve the "Z-10kV-01-001" partition upstream of node A ( (Not reached) ), downstream “Z-10kV-01-002” section ( (Da) This indicates that there are fault-related characteristics downstream of the main line.

[0116] Current flow direction determination: Based on the phase difference between the current and voltage at node A, determine that the current flows from the main line to branch 1 (forward flow direction).

[0117] Interference elimination and judgment: Based on the amplitude trend verification results (both the main line and the branch line meet the fault characteristics) and the positive flow direction, it is determined that the excessive change rate of branch 1 is caused by the conduction of the fault current of the main line and there is no independent interference. After eliminating the influence of branch interference, the "Z-10kV-01-002" section of the main line is identified as the core fault-related section.

[0118] If a branch line is suspected of having a fault but the main line has not reached the threshold (e.g., branch 2 partition), However, the upstream and downstream of the corresponding main line node B ( If the amplitude characteristics of branch 2 are checked separately: if the amplitude of branch 2 is 0.07A (≥ the first preset threshold 0.06A), branch 2 is locked as a fault section; if the amplitude is 0.01A (< the second preset threshold 0.02A), it is determined to be a branch load disturbance and the suspected marker is removed.

[0119] Location result output and verification:

[0120] The fault section was ultimately identified as the "Z-10kV-01-002" section (node ​​A to node B, within a 3km range) of the main line. On-site inspection by maintenance personnel revealed that the C-phase line insulator was damaged and grounded 1.2km from node A within this section, perfectly matching the location finding. This location accuracy reached 1.2km, with a response time of 85ms. Furthermore, the 30% / 10% threshold settings effectively avoided the problem of "small-amplitude disturbances being misjudged as faults," improving the accuracy rate to 98%.

[0121] Example 2: Figure 2 These are exemplary block diagrams of a distribution network line fault location system according to some embodiments of this specification. Figure 2 As shown, the system includes:

[0122] Fault identification module: After the system detects a ground fault, it collects the real-time amplitude of the three-phase voltage and compares it with the change pattern of its normal operating reference amplitude to determine the faulty phase with abnormal voltage; at the same time, it extracts the moment of sudden change in phase voltage and the moment of sudden change in power of the arc suppression device, and calibrates the precise fault moment by the intersection of the two time series, providing a basic time and phase reference for subsequent fault location.

[0123] Topology Identification Module: Used to retrieve real-time distribution network topology data and divide multi-branch lines into main line zones and branch line zones according to the power transmission path hierarchy;

[0124] Calculation module: used to screen the various detection devices in The effective data of the current waveforms of the 2N target fault phases within the interval are first processed according to the formula. Calculate the fault phase current difference between adjacent detection points, where Where n is negative to represent before the fault and n is positive to represent after the fault, and N is the number of sampling points per power frequency cycle; then, based on the current difference data before and after the fault, the main line current change rate is calculated respectively. and branch line current mutation rate This forms quantitative indicators of fault characteristics;

[0125] Fault Section Determination Module: This module first adjusts the arc-removal coil type and fault transition resistance value, and then generates main line section thresholds by fitting historical fault condition data. and branch line partition threshold The method compares the stratified current mutation rate with the corresponding threshold to determine the suspected fault section; then retrieves the current mutation rate time series curves of upstream and downstream nodes of the suspected fault section to verify the change trend of the current difference amplitude before and after the fault; at the same time, for multi-branch topology, the method establishes a correlation model between the current mutation rate of the main line and the branch line to eliminate the interference of branch current disturbance, and finally locks the target fault section.

[0126] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

[0127] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this specification are not intended to limit the order of the processes and steps in this specification. Although various examples have been discussed in the foregoing disclosure of some embodiments of the invention that are currently considered useful, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. Rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments in this specification. For example, while the system components described above can be implemented using hardware devices, they can also be implemented solely using software solutions, such as installing the described system on existing servers or mobile devices.

[0128] Similarly, it should be noted that, in order to simplify the description disclosed herein and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of embodiments in this specification may sometimes combine multiple features into a single embodiment, drawing, or description thereof. However, this method of disclosure does not imply that the subject matter of this specification requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of a single embodiment disclosed above.

[0129] Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein.

Claims

1. A method for locating faults in a distribution network line, characterized in that, Includes the following steps: After the system detects a ground fault, it determines the faulty phase by observing the variation pattern of the three-phase voltage amplitude; and calibrates the fault time by combining the time sequence intersection of the phase voltage change moment and the arc suppression device power change moment. Based on the distribution network topology, multi-branch lines are divided into main line zones and branch line zones and assigned independent location identifiers. Select the target faulty phase and extract the corresponding current waveform data, then calculate the current difference between the faulty phases at adjacent detection points. ,in Where n is negative to indicate before the fault and n is positive to indicate after the fault, and N is the number of sampling points in one power frequency cycle; the main line current change rate is calculated based on the fault phase current difference between adjacent detection points. and branch line current mutation rate ; Based on the arc suppression coil type and fault transition resistance value, a main line partition threshold is fitted and generated. and branch line partition threshold Compare the stratified current mutation rate with the corresponding partition threshold, if and If the section is not faulty, it is considered a suspected faulty section; otherwise, it is considered a non-faulty section. Retrieve the current mutation rate time series curves of upstream and downstream nodes of the suspected fault section to verify the trend of current difference amplitude change before and after the fault. For multi-branch topologies, interference is eliminated by the correlation between the current change rates of the main line and the branch lines, and the target fault section is finally located.

2. The method according to claim 1, characterized in that, The method of dividing multi-branch lines into main line partitions and branch line partitions based on distribution network topology includes: Starting from the outgoing line end of the distribution network substation, the line segment extending along the main power transmission path to the end of the trunk line is divided into main line sections; starting from each branch node on the main line, the line segment extending to the end of the branch line is divided into branch line sections, and each branch line section is associated with a corresponding main line branch node.

3. The method according to claim 1, characterized in that, The formulas for calculating the main line current mutation rate and the branch line current mutation rate are as follows: ； ； in, The difference in fault phase current between adjacent detection points on the main line. The difference in fault phase current between adjacent detection points on a branch line.

4. The method according to claim 1, characterized in that, The calculation of the fault transition resistance value includes: Detect the effective value of the fault phase voltage at the time of the fault. and the effective value of residual current at the fault point Through formula The fault transition resistance value was calculated, where the residual current at the fault point was derived by subtracting the load current and the capacitance current to ground from the fault phase current.

5. The method according to claim 1, characterized in that, The verification of the current difference amplitude change trend before and after the fault, and the elimination of interference through the correlation of current change rate between the main line and the branch line, include: Amplitude trend verification: If the current difference amplitude after a section fault increases by a first preset threshold or more than before the fault, it is determined to meet the amplitude characteristics of a fault section; if the amplitude decreases or the increase is less than the second preset threshold, it is determined to be a non-fault section characteristic. Multi-branch interference elimination: When a branch line section is identified as a suspected fault section, the current change rate upstream and downstream of the corresponding main line branch node is checked. If the current change rate of the main line section does not reach the threshold, the branch line is locked as a fault section. If the current change rate of the main line section reaches the threshold, the influence of current disturbance of the branch line is eliminated by combining the current flow direction of the branch node before the main line fault section is determined.

6. A fault location system for distribution network lines, characterized in that, The system includes: Fault identification module: After the system detects a ground fault, it collects the real-time amplitude of the three-phase voltage and compares it with the change pattern of its normal operating reference amplitude to determine the faulty phase with abnormal voltage; at the same time, it extracts the moment of sudden change in phase voltage and the moment of sudden change in power of the arc suppression device, and calibrates the precise fault moment by the intersection of the two time series, providing a basic time and phase reference for subsequent fault location. Topology Identification Module: Used to retrieve real-time distribution network topology data and divide multi-branch lines into main line zones and branch line zones according to the power transmission path hierarchy; Calculation module: Used to filter target fault phase currents and extract valid waveform data, first according to the formula. Calculate the fault phase current difference between adjacent detection points, where Where n is negative to represent before the fault and n is positive to represent after the fault, and N is the number of sampling points per power frequency cycle; then, based on the current difference data before and after the fault, the main line current change rate is calculated respectively. and branch line current mutation rate This forms quantitative indicators of fault characteristics; Fault Section Determination Module: This module first adjusts the arc-removal coil type and fault transition resistance value, and then generates main line section thresholds by fitting historical fault condition data. and branch line partition threshold The method compares the stratified current mutation rate with the corresponding threshold to determine the suspected fault section; then retrieves the current mutation rate time series curves of upstream and downstream nodes of the suspected fault section to verify the change trend of the current difference amplitude before and after the fault; at the same time, for multi-branch topology, the method establishes a correlation model between the current mutation rate of the main line and the branch line to eliminate the interference of branch current disturbance, and finally locks the target fault section.

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