Low-voltage short-circuit fault troubleshooting method based on access impedance

Abstract

The application discloses a low-voltage short-circuit fault troubleshooting method based on access impedance, relates to the technical field of low-voltage line fault detection, and the impedance is connected in series into a short-circuit fault line to limit a fault current and maintain a power-on state of the fault line, and comprises the following steps: acquiring a voltage characteristic of a low-voltage line and a tripping state of a superior circuit breaker, pre-judging a fault type and a corresponding fault probability according to the voltage characteristic and the tripping state; generating a fault disposal work ticket of the corresponding fault type according to the fault probability and a short-circuit fault disposal table; acquiring first current data at each preset detection node before impedance access and second current data at each preset detection node after impedance access according to a differential search path in the fault disposal work ticket; and determining a fault line section according to data differences between the first current data and the second current data. The application remarkably improves fault positioning accuracy and fault troubleshooting efficiency.

Description

Technical Field

[0001] This invention relates to the field of low-voltage line fault detection technology, specifically to a method for troubleshooting low-voltage short-circuit faults based on connection impedance. Background Technology

[0002] Low-voltage power distribution networks are dense and fault points are often hidden, with frequent faults such as phase-to-ground faults, neutral-to-ground faults, and phase-to-phase short circuits. Low-voltage lines are only equipped with basic protective devices such as air switches and residual current circuit breakers, making it impossible to record fault electrical characteristic data. Fault diagnosis heavily relies on the experience and analytical skills of maintenance personnel. Existing fault diagnosis techniques mostly involve disconnecting the line after power outage to test insulation resistance, or manually inspecting each section and measuring current under energized conditions to locate faults. The former is repetitive and inefficient, while the latter lacks effective fault current limiting measures, easily triggering circuit breaker tripping, and lacks a systematic fault type prediction mechanism. Furthermore, the troubleshooting path and testing parameters are not adapted for each other. These inherent shortcomings combine to result in low fault location accuracy and long processing times in practical applications. Troubleshooting complex, multi-loaded, or hidden lines is extremely difficult, increasing the workload and safety risks for maintenance personnel and failing to meet the actual needs of rapid and efficient low-voltage line maintenance, seriously affecting power supply reliability.

[0003] The information disclosed in the background section is only intended to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to address the problems of low accuracy and long time consumption in fault location due to the difficulty of troubleshooting complex multi-load lines or concealed lines in existing solutions. It proposes a low-voltage short-circuit fault location method based on impedance matching. By connecting an impedance matching in series with the faulty line to limit the fault current and maintain the energized state, the method reduces safety risks by eliminating the need for power outages. It combines voltage characteristics and tripping status to predict the fault type and probability, automatically generates a suitable fault handling work order, and dynamically determines the fault section by obtaining the difference in current data before and after impedance matching based on a differential search path. This significantly improves the accuracy of fault location and the efficiency of fault troubleshooting.

[0005] Based on this, one technical solution provided in this embodiment of the invention is: a low-voltage short-circuit fault investigation method based on access impedance, wherein the impedance is connected in series with the short-circuit fault line to limit the fault current and maintain the energized state of the fault line, including the following steps: Obtain the voltage characteristics of the low-voltage line and the tripping status of the upstream circuit breaker, and predict the fault type and its corresponding fault probability based on the voltage characteristics and tripping status. Based on the fault probability and the short-circuit fault handling table, generate a fault handling work order for the corresponding fault type. According to the differential search path in the fault handling work order, the first current data at each preset detection node before impedance connection and the second current data at each preset detection node after impedance connection are obtained respectively. The faulty line section is determined based on the difference between the first current data and the second current data.

[0006] Preferably, the steps of obtaining the voltage characteristics of the low-voltage line and the tripping status of the upstream circuit breaker, and predicting the fault type and its corresponding fault probability based on the voltage characteristics and tripping status are as follows: Measure the three-phase voltage and zero-sequence voltage of the faulty line and identify the tripping type of the upstream circuit breaker; the tripping type includes overcurrent tripping and residual current operated protection tripping; If any phase voltage is lower than the first set threshold and the voltages of the remaining phases are higher than the second set threshold, the fault type is determined to be a phase-to-ground fault, and the fault probability corresponding to the fault type is determined based on the current phase voltage drop and the magnitude of the zero-sequence current; otherwise, the fault probability corresponding to the fault type is determined based on the tripping type, which includes phase-to-ground fault, neutral-to-ground fault, phase-to-neutral short-circuit fault, and phase-to-phase short-circuit fault.

[0007] Preferably, the step of determining the fault probability corresponding to the fault type based on the current phase voltage drop and the zero-sequence current magnitude is as follows: Calculate the voltage drop of the faulty phase. and the zero-sequence current of the faulty circuit If zero-sequence current Greater than the zero-sequence current set threshold If so, it is determined that there is a phase-to-ground fault; according to and The magnitude of is determined by a preset probability mapping relationship to determine the fault probability corresponding to a phase-to-ground fault, where: like Then the failure probability is the first probability value. ; like Then the failure probability is the second probability value. ; like Then the failure probability is the third probability value. ; like Then the failure probability is the fourth probability value. ; in, This is the critical threshold for distinguishing the magnitude of voltage drop. .

[0008] Preferably, the step of determining the fault probability corresponding to the fault type based on the tripping type is as follows: If the residual current protection trips, and the zero-sequence current... Less than the typical value of phase-to-ground current I g1 If the fault type is determined to be a neutral ground fault, the corresponding fault probability is based on the zero-sequence current. Compared with the preset ground fault current reference value I ref The proportional relationship is determined; If the circuit breaker trips due to overcurrent and the insulation resistance between any two phases is measured to be lower than the insulation set threshold, the fault type is determined to be a phase-to-phase short circuit fault, and the corresponding fault probability is determined based on the degree to which the insulation resistance deviates from the normal value. If the trip is due to overcurrent, and only a single phase current exceeds the rated current threshold, accompanied by a synchronous increase in neutral current exceeding the current limit, then the fault type is determined to be a phase-neutral short-circuit fault, and the corresponding fault probability is determined based on the ratio of the current phase current to the rated load current.

[0009] Preferably, the step of generating a fault handling work order for the corresponding fault type based on the fault probability and the short-circuit fault handling table is as follows: Receive the predicted fault type and its corresponding fault probability, query the preset short-circuit fault handling table according to the fault type, and obtain the benchmark troubleshooting strategy corresponding to the fault type. Based on the magnitude of the failure probability, at least one controllable parameter in the baseline troubleshooting strategy is adjusted to generate an adapted troubleshooting strategy. Based on the aforementioned fault diagnosis strategy, a fault handling work order is generated, which includes impedance element access points, impedance parameters, differential search paths, detection node sequences, and safety operation instructions.

[0010] Preferably, the step of adjusting at least one controllable parameter in the baseline troubleshooting strategy according to the magnitude of the fault probability to generate an adapted fault troubleshooting strategy is as follows: The received fault probability is compared with at least two preset probability thresholds to determine the corresponding strategy adjustment mode in order to adjust the impedance element parameters in the benchmark troubleshooting strategy and switch the differential search path in the benchmark troubleshooting strategy. The adapted troubleshooting strategy is generated based on the adjusted impedance element parameters and the differential search path.

[0011] As a preferred embodiment, the steps for determining the corresponding strategy adjustment mode to adjust the impedance element parameters in the benchmark troubleshooting strategy are as follows: If the strategy adjustment mode is the first mode, the impedance element parameters in the benchmark troubleshooting strategy are adjusted to a first capacitance value corresponding to the high short-circuit limiting capability; if the strategy adjustment mode is the second mode, the impedance element parameters are adjusted to a second capacitance value corresponding to the standard detection sensitivity.

[0012] As a preferred approach, the steps for determining the corresponding strategy adjustment mode to switch the differential search path in the baseline investigation strategy are as follows: If the strategy adjustment mode is the first mode, an optimized binary search sequence is used, and the starting detection node of the sequence is determined based on the total line length and a preset ratio; if the strategy adjustment mode is the second mode, a progressive search sequence from the power supply side to the load side is used.

[0013] Preferably, the steps for determining the strategy adjustment mode are as follows: A first probability threshold α and a second probability threshold β are preset, where α>β, and the failure probability Px is compared with α and β respectively; If Px≥α, then the policy adjustment mode is determined to be the first mode; If β≤Px<α, then the policy adjustment mode is determined to be the second mode; If Px < β, then the policy adjustment mode is determined to be the third mode.

[0014] Preferably, the step of determining the faulty line section based on the data difference between the first current data and the second current data is as follows: Based on the detection node sequence in the fault handling work order, before impedance connection, a first set of current data is measured and recorded at each preset detection node; after impedance connection, a second set of current data is measured and recorded at the same preset detection nodes. The current change characteristic values ​​at the corresponding detection node locations are determined based on the first current data set and the second current data set. Based on the detection node sequence, the node positions where the current change characteristic value changes abruptly are identified sequentially from the power flow direction. If the current at the preset detection node decreases by more than the current at the upstream preset detection node by a preset abrupt change threshold, the faulty line segment is determined to be located between the current preset detection node and the corresponding upstream preset detection node.

[0015] The present invention has at least the following substantial beneficial effects: (1) In view of the problems that low-voltage power distribution network faults are hidden, basic protection electrical appliances cannot record fault electrical characteristic data, and fault diagnosis relies heavily on human experience, resulting in low positioning accuracy and long time consumption, this application limits the fault current and maintains the energized state by connecting the fault line in series with the faulty line, and predicts the fault type and probability by combining voltage characteristics and tripping status. This realizes that fault diagnosis does not require power outage operation and reduces safety risks. At the same time, it establishes a systematic fault prediction mechanism, greatly reduces the reliance on the experience of operation and maintenance personnel, and significantly improves the accuracy of fault location and the efficiency of diagnosis.

[0016] (2) In view of the problem that the lack of adaptability adjustment between the investigation path and the detection parameters in the existing fault investigation technology makes it difficult to investigate complex multi-load lines or hidden lines, this application determines the strategy adjustment mode by comparing the fault probability with the preset probability threshold, and dynamically adjusts the impedance element parameters and differential search path, thereby realizing the adaptive optimization of the fault investigation strategy. This enables the investigation path and detection parameters to be automatically adapted according to the fault probability, effectively solving the problem of fault location in complex lines and greatly improving the investigation efficiency.

[0017] (3) In view of the problem of inaccurate current data difference analysis in traditional fault diagnosis technology, which leads to positioning deviation, this application obtains the difference in current data before and after impedance connection based on differential search path, dynamically determines the fault section, and realizes accurate positioning of the fault section. Specifically, by identifying the sudden change node of current change characteristic value, the fault location is accurately determined, which effectively solves the problem of inaccurate positioning caused by the inability to distinguish between normal fluctuations and fault characteristics, and significantly improves the accuracy and reliability of fault positioning.

[0018] The above description of the invention is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0019] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings. The drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0020] Figure 1 This is a flowchart of a low-voltage short-circuit fault diagnosis method based on access impedance according to an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only one preferred embodiment of this invention and are only used to explain this invention. They do not limit the scope of protection of this invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] Before discussing the exemplary embodiments in more detail, it should be mentioned that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations (or steps) as sequential processes, many of the operations (or steps) can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but it may also have additional steps not included in the figures; the process may correspond to a method, function, procedure, subroutine, subroutine, etc.

[0023] Example 1: As Figure 1 As shown, one technical solution provided in this embodiment of the invention is: a low-voltage short-circuit fault diagnosis method based on access impedance, wherein the impedance is connected in series with the short-circuit fault line to limit the fault current and maintain the energized state of the fault line, including the following steps: S1. Obtain the voltage characteristics of the low-voltage line and the tripping status of the upstream circuit breaker, and predict the fault type and its corresponding fault probability based on the voltage characteristics and tripping status.

[0024] Understandably, current low-voltage short-circuit fault investigation methods lack systematic fault type and probability prediction methods based on electrical characteristics and tripping status. They rely solely on the experience of maintenance personnel, which can easily lead to misjudgments due to ambiguous fault characteristics. Furthermore, the probability of fault occurrence cannot be quantified, hindering the formulation of subsequent investigation strategies. A prediction mechanism is urgently needed to lay the foundation for accurate investigation.

[0025] As an optional embodiment, the steps of obtaining the voltage characteristics of the low-voltage line and the tripping status of the upstream circuit breaker, and predicting the fault type and its corresponding fault probability based on the voltage characteristics and tripping status are as follows: Measure the three-phase voltage and zero-sequence voltage of the faulty line and identify the tripping type of the upstream circuit breaker; the tripping type includes overcurrent tripping and residual current operated protection tripping.

[0026] If any phase voltage is lower than the first set threshold and the voltages of the remaining phases are higher than the second set threshold, the fault type is determined to be a phase-to-ground fault, and the fault probability corresponding to the fault type is determined based on the current phase voltage drop and the magnitude of the zero-sequence current; otherwise, the fault probability corresponding to the fault type is determined based on the tripping type, which includes phase-to-ground fault, neutral-to-ground fault, phase-to-neutral short-circuit fault, and phase-to-phase short-circuit fault.

[0027] Understandably, this step establishes a hierarchical fault judgment logic by integrating the core electrical parameters of the faulty line with the operating status of the protection device. It first identifies typical fault types through voltage characteristics, and then quantifies the fault probability by combining tripping type and key electrical quantities, thus realizing the transformation of fault prediction from experience-driven to data-driven.

[0028] Specifically, this embodiment first measures the three-phase voltage (e.g., the real-time operating voltage of phases A, B, and C under a rated voltage of 220V) and the zero-sequence voltage (i.e., the vector sum of the three-phase voltages, which is usually below 5V during normal operation and is used to reflect line imbalance and grounding fault characteristics) of the faulty line, and identifies the tripping type of the upstream circuit breaker. Overcurrent tripping is triggered when the line current exceeds the rated value; residual current protection tripping is triggered when the line leakage current exceeds a set value. By simultaneously capturing the abnormal electrical parameters caused by the fault and the response characteristics of the protection device, dual data support is provided for fault type determination, avoiding the one-sidedness of judging by a single parameter. If any phase voltage is lower than the first set threshold (e.g., set to 180V, below the reasonable operating range of rated 220V, indicating that the phase may have a voltage drop due to grounding) and the voltages of the other phases are higher than the second set threshold (e.g., set to 230V, due to load imbalance during single-phase grounding causing voltage increases in non-faulty phases), it is determined to be a phase-to-ground fault. Then, the voltage drop of the faulty phase and the zero-sequence current are calculated. (Measured by a zero-sequence current transformer), the probability is determined by combining a preset mapping relationship. This method achieves objectivity and accuracy in probability judgment by quantifying the correlation between fault characteristic parameters and fault probability. If the above voltage conditions are not met, the fault type is further distinguished according to the tripping type. This hierarchical judgment logic comprehensively covers the main short-circuit fault types of low-voltage lines, ensuring the completeness of fault type identification. At the same time, through the linkage analysis of key electrical quantities and tripping types, the risk of misjudgment from a single judgment dimension is effectively reduced. Ultimately, it achieves rapid and accurate identification of fault types and quantitative assessment of fault probability, providing a reliable basis for the formulation of subsequent adaptability investigation strategies.

[0029] As an optional embodiment, the step of determining the fault probability corresponding to the fault type based on the current phase voltage drop and the zero-sequence current magnitude is as follows: Calculate the voltage drop of the faulty phase. and the zero-sequence current of the faulty circuit If zero-sequence current Greater than the zero-sequence current set threshold If so, it is determined that there is a phase-to-ground fault; according to and The magnitude of is determined by a preset probability mapping relationship to determine the fault probability corresponding to a phase-to-ground fault, where: like Then the failure probability is the first probability value. ; like Then the failure probability is the second probability value. ; like Then the failure probability is the third probability value. ; like Then the failure probability is the fourth probability value. ; in, This is the critical threshold for distinguishing the magnitude of voltage drop. .

[0030] It is understandable that existing technologies lack quantitative basis for determining the probability of phase-to-ground faults. Relying solely on a single fault characteristic can easily lead to judgment bias and cannot provide accurate support for subsequent troubleshooting strategy adjustments. Therefore, this embodiment integrates two core fault characteristic parameters, namely the voltage drop amplitude of the faulty phase and the zero-sequence current, to establish a multi-dimensional quantitative mapping relationship. First, the existence of the fault is initially locked by the zero-sequence current threshold, and then the fault probability is determined by the combination of the two parameters, thereby achieving accurate quantitative determination of the probability of phase-to-ground faults.

[0031] Specifically, first, the voltage drop amplitude ΔU of the faulty phase is calculated, and at the same time, the zero-sequence current of the faulty line is measured. By simultaneously capturing fault characteristics in both voltage and current dimensions, a dual quantitative basis is provided for probability determination, avoiding the one-sidedness of a single parameter; then, a zero-sequence current setting threshold is set. ,like If a phase-to-ground fault is confirmed from the current perspective, this threshold determination mechanism can effectively eliminate interference from minute leakage currents during normal operation, ensuring the accuracy of fault determination; subsequently, a pre-set probability mapping relationship is established. And divide into four groups of probability values, when This indicates a significant voltage drop and obvious grounding leakage, making the fault characteristics most prominent; therefore, it is assigned the highest probability. ,when At that time, the voltage drop was significant but the leakage current was weak, and the failure probability was set to second highest. ;when At that time, leakage was obvious but voltage impact was small, and the fault probability was set to... ;when When both features are not significant, the lowest probability of failure is set as... This hierarchical mapping mechanism is based on the logical correlation between the salience of fault features and the probability of fault occurrence, thereby achieving hierarchical and precise probability determination. It ensures that different fault severity levels correspond to differentiated probability assessment results, providing reliable quantitative support for the adaptive adjustment of subsequent troubleshooting strategies.

[0032] As an optional embodiment, the step of determining the fault probability corresponding to the fault type based on the tripping type is as follows: If the residual current protection trips, and the zero-sequence current... Less than the typical value of phase-to-ground current I g1 If the fault type is determined to be a neutral ground fault, the corresponding fault probability is based on the zero-sequence current. Compared with the preset ground fault current reference value I ref The proportional relationship is determined; If the circuit breaker trips due to overcurrent and the insulation resistance between any two phases is measured to be lower than the insulation set threshold, the fault type is determined to be a phase-to-phase short circuit fault, and the corresponding fault probability is determined based on the degree to which the insulation resistance deviates from the normal value. If the trip is due to overcurrent, and only a single phase current exceeds the rated current threshold, accompanied by a synchronous increase in neutral current exceeding the current limit, then the fault type is determined to be a phase-neutral short-circuit fault, and the corresponding fault probability is determined based on the ratio of the current phase current to the rated load current.

[0033] Understandably, existing technologies for low-voltage short-circuit faults that are not phase-to-ground faults lack precise judgment logic based on the linkage between tripping type and core electrical parameters. This can easily lead to type confusion due to overlapping fault characteristics, and the fault probability cannot be quantified, making it difficult to support the formulation of subsequent adaptive troubleshooting strategies. In this embodiment, the steps are classified according to tripping type (residual current operated protection tripping, overcurrent tripping), and fault type judgment and probability quantification rules are established in combination with specific electrical characteristic parameters to achieve accurate identification and probability assessment of three types of faults: neutral-to-ground faults, phase-to-phase short circuits, and phase-to-neutral short circuits.

[0034] Specifically, this embodiment first addresses the residual current protection tripping scenario (specifically, the line leakage current exceeds the set operating current of the residual current protection, which physically means that there is a risk of grounding leakage in the line), and sets a typical value I for the phase-line grounding current. g1 If the measured zero-sequence current Less than I g1 If the phase-to-ground fault is ruled out, the fault is determined to be a neutral-to-ground fault, and the ground fault current reference value I is preset. ref Through the proportional relationship P= ×k / I refThe fault probability is determined, where k is a correction coefficient (normalized value) to ensure the probability value is within a reasonable range. The fault type is identified by comparing the tripping type with the zero-sequence current threshold, and the probability is quantified using current ratios to achieve accurate determination and objective assessment of the probability of neutral grounding faults. Secondly, for overcurrent tripping scenarios (where the line current exceeds the rated value), if the insulation resistance between any two phases is measured to be lower than the set insulation threshold, it is determined to be a phase-to-phase short-circuit fault. A normal value for the insulation resistance between normal phases is set, and the degree of deviation is calculated. The system directly reflects the severity of short circuits between phases by using insulation resistance parameters, achieving a precise match between fault probability and fault level. Finally, also for overcurrent tripping scenarios, if only a single phase current exceeds the rated current threshold, and the neutral current simultaneously increases and exceeds the current limit, it is determined to be a phase-neutral short circuit fault. The fault probability is determined based on the ratio of the current phase current to the rated load current combined with a normalization coefficient. The fault type is locked by the current synergy characteristics of the phase and neutral lines, and the probability corresponding to the fault severity is quantified using the current ratio, ensuring that the judgment results closely match the actual fault scenario. Finally, through a categorized and parameterized judgment logic, the system achieves precise differentiation and probability quantification of three types of non-phase-to-ground faults, providing a precise basis for the generation of subsequent fault handling work orders.

[0035] S2. Generate a fault handling work order for the corresponding fault type based on the fault probability and the short-circuit fault handling table.

[0036] As an optional embodiment, the step of generating a fault handling work order corresponding to the fault type based on the fault probability and the short-circuit fault handling table is as follows: Receive the predicted fault type and its corresponding fault probability, query the preset short-circuit fault handling table according to the fault type, and obtain the benchmark troubleshooting strategy corresponding to the fault type. Based on the magnitude of the failure probability, at least one controllable parameter in the baseline troubleshooting strategy is adjusted to generate an adapted troubleshooting strategy. Based on the aforementioned fault diagnosis strategy, a fault handling work order is generated, which includes impedance element access points, impedance parameters, differential search paths, detection node sequences, and safety operation instructions.

[0037] Understandably, existing troubleshooting strategies are mostly fixed processes that are not dynamically adapted to the fault type and probability. This results in insufficient targeting of troubleshooting, lack of standardized operation guidance, and problems such as improper parameter selection and unreasonable path planning. Therefore, this embodiment first matches the baseline strategy according to the fault type, then dynamically adjusts the parameters based on the probability, and finally generates a fault handling work ticket containing full process operation information, so as to achieve standardization, adaptability and safety of fault troubleshooting.

[0038] Specifically, this embodiment first receives the fault type and its corresponding fault probability predicted in the aforementioned steps. The pre-set short-circuit fault handling table is a standardized strategy database pre-stored in the system, which records the basic operation framework corresponding to various fault types. By querying this table by fault type, a benchmark troubleshooting strategy can be quickly obtained. This technique avoids repetitive design of troubleshooting processes by pre-storing standardized benchmark templates, significantly improving strategy generation efficiency. Then, at least one controllable parameter in the benchmark troubleshooting strategy is adjusted according to the magnitude of the fault probability (controllable parameters include the capacitance value of impedance components, the type of search path, the density of detection nodes, etc. For example, the higher the fault probability, the more significant the fault characteristics, requiring stronger fault current limiting capabilities and more efficient search paths). For instance, if the fault probability is high, P1, the impedance parameter in the benchmark strategy can be adjusted to a value corresponding to high short-circuit limiting capabilities, and the search path can be switched to an optimized binary search. The fault probability quantification reflects the significance of the fault characteristics and the troubleshooting priority. Parameter adjustment enables the strategy to accurately match the actual fault scenario, achieving optimized allocation of troubleshooting resources and improving the targeting of troubleshooting. Based on the adjusted adaptation and troubleshooting strategy, a fault handling work order containing multi-dimensional key information is generated. The impedance element access point refers to the specific location of the series impedance in the faulty line; the impedance parameter refers to the specific value of the impedance element adapted to the fault scenario (e.g., a first capacitance of 0.47μF, corresponding to high short-circuit limiting capability); the differential search path refers to the node investigation sequence adapted to the fault probability (e.g., the starting detection node of the binary search path is at 50% of the total line length); the detection node sequence refers to the pre-set specific detection points, such as 10 detection points set every 100 meters on a 1000-meter line, physically meaning to clarify the specific location for current data collection and ensure data integrity; and the safety operation instructions refer to the mandatory requirements to ensure the safety of maintenance personnel (e.g., disconnecting the load power supply and wearing insulating protective equipment before connecting the impedance). This embodiment, by integrating the adapted parameters and operating specifications, forms a standardized and directly executable operation document, avoiding reliance on the experience of maintenance personnel and effectively mitigating operational risks. Ultimately, it provides clear, accurate, and safe full-process operation guidance for subsequent fault current data collection and fault segment location.

[0039] As an optional embodiment, the step of adjusting at least one controllable parameter in the baseline troubleshooting strategy according to the magnitude of the fault probability to generate an adapted fault troubleshooting strategy is as follows: The received fault probability is compared with at least two preset probability thresholds to determine the corresponding strategy adjustment mode in order to adjust the impedance element parameters in the benchmark troubleshooting strategy and switch the differential search path in the benchmark troubleshooting strategy. The adapted troubleshooting strategy is generated based on the adjusted impedance element parameters and the differential search path.

[0040] It is understandable that in existing technologies, the controllable parameters and differential search paths of the baseline troubleshooting strategy are mostly fixed and are not dynamically adjusted in conjunction with the fault probability. This may lead to insufficient current limitation or low search efficiency affecting the troubleshooting effect in high-probability fault scenarios, while in low-probability fault scenarios, fault features may be missed due to insufficient detection sensitivity. Therefore, this embodiment establishes a linkage adjustment mechanism between fault probability and strategy parameters and search paths. First, the adjustment mode is determined by the probability threshold, and then the impedance element parameters and search paths are optimized simultaneously to generate a troubleshooting strategy that adapts to the fault probability, thereby achieving precise allocation of troubleshooting resources.

[0041] Specifically, at least two probability thresholds are preset, such as a first probability threshold α=90% and a second probability threshold β=60%. Higher probabilities indicate more significant fault characteristics and higher investigation priority. The received fault probability Px is compared with the thresholds to determine the corresponding strategy adjustment mode. Precise determination of the adjustment mode is achieved through probability grading, providing a clear basis for parameter and path optimization. Simultaneously, the strategy adjustment mode is directly related to the impedance element parameters and differential search path in the baseline investigation strategy. The impedance element parameters characterize the ability to limit fault current (e.g., a larger capacitance value indicates higher equivalent impedance and stronger current limiting effect). For example, in the first mode, the first capacitance value corresponds to high short-circuit limiting capability, while in the second mode, it corresponds to the second capacitance value corresponding to standard detection sensitivity. The differential search path includes the investigation order and starting position of the fault detection nodes. For example, in the first mode, an optimized binary search sequence is used (e.g., ...). The initial detection node for a 1000-meter-long line is located at 50% of the total line length, i.e., at 500 meters, which can quickly narrow down the fault range. In the second mode, a progressive search sequence is adopted from the power supply side to the load side (e.g., setting a detection node every 100 meters starting from the power supply side to ensure that no fault characteristics are missed). This linkage adjustment mechanism is based on the significance of fault characteristics reflected by the fault probability, realizing targeted optimization of parameters and paths, avoiding the problem of insufficient adaptability caused by fixed settings. Subsequently, based on the adjusted impedance element parameters and differential search path, an adapted fault investigation strategy is generated, forming a dedicated investigation plan that accurately matches the fault probability. This makes the investigation strategy no longer a general template, but a personalized solution that fits the specific fault probability scenario. It ensures both rapid and efficient investigation of high-probability faults and takes into account the detection sensitivity of low-probability faults, providing reliable strategy support for subsequent accurate acquisition of current data and rapid location of fault sections.

[0042] As an optional embodiment, the steps for determining the corresponding strategy adjustment mode to adjust the impedance element parameters in the baseline troubleshooting strategy are as follows: If the strategy adjustment mode is the first mode, the impedance element parameters in the benchmark troubleshooting strategy are adjusted to a first capacitance value corresponding to the high short-circuit limiting capability; if the strategy adjustment mode is the second mode, the impedance element parameters are adjusted to a second capacitance value corresponding to the standard detection sensitivity.

[0043] Understandably, in existing technologies, impedance element parameters are mostly fixed and cannot be dynamically adapted according to the risk level corresponding to the fault probability. This results in insufficient short-circuit current limitation in high fault probability scenarios, which easily triggers circuit breaker tripping, and insufficient detection sensitivity in medium fault probability scenarios, making it difficult to capture weak fault characteristics. Therefore, this embodiment establishes a precise matching mechanism between strategy adjustment mode and impedance element parameters, and adjusts the capacitance value according to the mode to balance short-circuit limiting capability and detection sensitivity, ensuring that the impedance element is adapted to different fault scenarios.

[0044] Specifically, when the strategy adjustment mode is the first mode, the impedance element parameters in the baseline strategy are adjusted to the first capacitance value, and then substituted into the AC circuit capacitive reactance formula. The calculated capacitive reactance is increased to enhance the current limiting effect, preventing excessive short-circuit current from triggering circuit breaker tripping in high-risk scenarios and ensuring the continuity of live-line inspections. When the strategy adjustment mode is the second mode, the value is adjusted to the second capacitance value, which is then substituted into the AC circuit capacitive reactance formula. The capacitive reactance is calculated, and by appropriately reducing the capacitive reactance, the fault current signal is placed within the sensitive response range of the detection equipment (such as a milliampere clamp meter). This ensures that the current is limited within the circuit breaker's non-tripping threshold while accurately capturing the fault current characteristics. Ultimately, this achieves dynamic adaptation of impedance component parameters under different fault risk levels, ensuring both the safety of troubleshooting and providing reliable signal support for subsequent current data acquisition.

[0045] As an optional embodiment, the steps for determining the corresponding strategy adjustment mode to switch the differential search path in the baseline investigation strategy are as follows: If the strategy adjustment mode is the first mode, an optimized binary search sequence is used, and the starting detection node of the sequence is determined based on the total line length and a preset ratio; if the strategy adjustment mode is the second mode, a progressive search sequence from the power supply side to the load side is used.

[0046] Understandably, existing fault diagnosis search paths are mostly single, fixed patterns that are not dynamically adjusted based on the salience of fault features corresponding to the fault probability. This results in long search times due to redundancy in high-probability fault scenarios, and incomplete coverage that easily misses weak fault features in medium-probability fault scenarios. Therefore, this embodiment establishes an adaptation mechanism between the strategy adjustment mode and the differential search path, switching the search sequence according to the mode to balance the troubleshooting efficiency and coverage completeness, ensuring the relevance of the search path under different fault scenarios.

[0047] Specifically, when the strategy adjustment mode is in the first mode, an optimized binary search sequence is used, with a preset ratio typically set at 50%. The starting detection node is determined by the formula S=L×k (where L is the total line length, e.g., 1000 meters, and k is the preset ratio of 0.5, then S=500 meters). Utilizing the divide-and-conquer approach, the detection results from the starting node quickly determine whether the fault is located in the first or second half of the line. The binary search is then repeated on the target section. For example, a 1000-meter line can be located after a maximum of 10 searches, significantly reducing the number of detection nodes, achieving rapid convergence of the fault range, and significantly improving the efficiency of troubleshooting high-probability faults. When the strategy adjustment mode is in the second mode, a progressive search from the power supply side to the load side is adopted. The detection sequence, for example, with a total line length of 800 meters, starts from the power supply side (0 meters) and sets a detection node every 100 meters (0 meters, 100 meters, 200 meters...800 meters), and advances towards the load side to cover all sections of the line segment by segment. This avoids missing weak fault features due to skipped detection. This embodiment ensures that the current change signal of medium probability faults (with inconspicuous features) can be completely captured through continuous and progressive detection logic, effectively reducing the risk of missed fault detection. Ultimately, it realizes dynamic adaptation of search paths under different fault probability scenarios, ensuring both rapid location of high probability faults and comprehensive coverage of medium probability faults, providing efficient and reliable path support for subsequent current data acquisition and accurate fault segment determination.

[0048] As an optional embodiment, the steps for determining the strategy adjustment mode are as follows: A first probability threshold α and a second probability threshold β are preset, where α>β, and the failure probability Px is compared with α and β respectively; If Px≥α, then the policy adjustment mode is determined to be the first mode; If β≤Px<α, then the policy adjustment mode is determined to be the second mode; If Px < β, then the policy adjustment mode is determined to be the third mode.

[0049] Understandably, existing technologies lack a strategy adjustment mode determination mechanism based on fault probability grading. This results in troubleshooting strategies failing to accurately adapt to the severity of fault characteristics and troubleshooting priorities corresponding to fault probabilities. High-probability faults may suffer from inadequate adjustment, impacting efficiency, while low-probability faults may lead to resource waste due to over-adjustment. Therefore, this embodiment constructs a three-level grading judgment logic by pre-setting dual probability thresholds, mapping fault probabilities to corresponding strategy adjustment modes. This achieves standardization and precision in troubleshooting strategy adjustments, ensuring that faults of different priorities can obtain appropriate troubleshooting strategy adjustment criteria. This provides clear directional guidance for subsequent impedance parameter optimization and search path switching, guaranteeing the pertinence and rationality of the troubleshooting strategy.

[0050] S3. Based on the differential search path in the fault handling work order, obtain the first current data at each preset detection node before impedance connection and the second current data at each preset detection node after impedance connection.

[0051] Understandably, current data acquisition in existing technologies lacks coordination with adaptive search paths, and the acquisition timing is singular with no clear planning for detection nodes, resulting in data lacking specificity and comparability, and failing to provide effective support for fault segment determination. Therefore, this step, following the differential search path adapted to the fault type and probability in the fault handling work order, collects current data from the same preset detection node twice to establish a data comparison benchmark, ensuring the relevance and effectiveness of the collected data. Specifically, the differential search path in the fault handling work order is an optimized node inspection sequence, and the preset detection nodes are fixed acquisition points pre-set on the faulty line. First, before impedance connection, following the sequence of the differential search path, the first set of current data is measured and recorded at each preset detection node using a milliampere clamp meter. Raw data is collected according to the planned path to avoid data correspondence errors caused by chaotic collection order, ensuring the integrity and orderliness of the first data set. Subsequently, after connecting the appropriate impedance element in series to the faulty line, the detection equipment and detection nodes remain unchanged, and the second current data set at each preset detection node is measured and recorded again along the same differential search path. Since the impedance connection will change the equivalent impedance of the faulty circuit, the current change pattern before and after the faulty section is fundamentally different from that of the normal section. By collecting data twice along the same path and at the same node, a precise dual data comparison dimension is constructed, providing paired and effective data support for the subsequent calculation of current change characteristic values. Ultimately, targeted and orderly collection of fault current data is achieved, ensuring strong correlation and comparability between the two data sets, and laying a solid data foundation for the accurate determination of the faulty section.

[0052] S4. Determine the faulty line section based on the data difference between the first current data and the second current data.

[0053] As an optional embodiment, the step of determining the faulty line section based on the data difference between the first current data and the second current data is as follows: Based on the detection node sequence in the fault handling work order, before impedance connection, a first set of current data is measured and recorded at each preset detection node; after impedance connection, a second set of current data is measured and recorded at the same preset detection nodes. The current change characteristic values ​​at the corresponding detection node locations are determined based on the first current data set and the second current data set. Based on the detection node sequence, the node positions where the current change characteristic value changes abruptly are identified sequentially from the power flow direction. If the current at the preset detection node decreases by more than the current at the upstream preset detection node by a preset abrupt change threshold, the faulty line segment is determined to be located between the current preset detection node and the corresponding upstream preset detection node.

[0054] Understandably, existing technologies lack a quantitative analysis mechanism based on comparing data before and after impedance connection for fault segment determination. Relying solely on single current data or manual experience can easily lead to misjudgments due to insignificant current change characteristics. This is especially true in complex multi-load lines where it is difficult to accurately pinpoint the fault range. Therefore, this step quantifies the fault characteristics based on the difference in current data before and after impedance connection, enabling precise location of the faulty line segment. It transforms fault location from experience-based judgment to quantitative judgment, significantly improving the accuracy of fault segment location, effectively narrowing the investigation scope, and reducing the difficulty of fault location in complex lines.

[0055] Specifically, based on the detection node sequence in the fault handling work order, before impedance connection, a milliampere-level clamp meter is used to measure and record the first current data set I at each preset detection node (e.g., 10 fixed points set at 100-meter intervals on a 1000-meter long line, the physical meaning of which is to provide a unified data acquisition benchmark and ensure data comparability). 11 ,I 12 ,...,I 1n After impedance connection, keeping the detection equipment, detection nodes, and environmental conditions unchanged, measure and record the second current data set I again along the same sequence. 21 ,I 22 ,...,I 2n By collecting data from the same node, along the same path, but at different times, a dual-data comparison dimension is constructed to avoid the bias of a single data source and provide a reliable data foundation for difference analysis. Then, based on the two sets of data, the characteristic values ​​of current changes at each detection node are determined. These characteristic values ​​can be expressed as the current change ΔI. i =∣I 1i - I 2i | or rate of change ηi = |I 1i - I 2i | / I 1iAfter impedance connection, the faulty section experiences drastic changes in the equivalent impedance of the fault circuit, resulting in a significantly larger current change characteristic value compared to the normal section. Quantitative calculations transform this current difference into a identifiable characteristic indicator, making the fault characteristics explicit. Finally, based on the detection node sequence, nodes exhibiting abrupt changes in current change characteristic values ​​are identified sequentially along the power flow direction. A preset abrupt change threshold γ is used. If the decrease in current change characteristic value of the current preset detection node relative to the upstream preset detection node exceeds γ, the faulty line section is determined to be located between the current node and the upstream node. By tracing abrupt change points along the power flow direction and utilizing the difference in current change patterns between the faulty and normal sections, the fault range is pinpointed, overcoming the blindness of traditional segment-by-segment troubleshooting.

[0056] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0057] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0058] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0059] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0060] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0061] The specific embodiments described above are preferred embodiments of the low-voltage short-circuit fault investigation method based on access impedance of the present invention, and are not intended to limit the specific scope of the present invention. The scope of the present invention includes but is not limited to the specific embodiments described above. All equivalent changes made in accordance with the shape and structure of the present invention are within the protection scope of the present invention.

Claims

1. A method for troubleshooting low-voltage short-circuit faults based on connection impedance, wherein the impedance is connected in series with the short-circuit faulted line to limit the fault current and maintain the energized state of the faulted line, characterized in that: Includes the following steps: Obtain the voltage characteristics of the low-voltage line and the tripping status of the upstream circuit breaker, and predict the fault type and its corresponding fault probability based on the voltage characteristics and tripping status. Based on the fault probability and the short-circuit fault handling table, generate a fault handling work order for the corresponding fault type. According to the differential search path in the fault handling work order, the first current data at each preset detection node before impedance connection and the second current data at each preset detection node after impedance connection are obtained respectively. The faulty line section is determined based on the difference between the first current data and the second current data.

2. The low-voltage short-circuit fault diagnosis method based on access impedance according to claim 1, characterized in that: The steps for obtaining the voltage characteristics of the low-voltage line and the tripping status of the upstream circuit breaker, and predicting the fault type and its corresponding fault probability based on the voltage characteristics and tripping status, are as follows: Measure the three-phase voltage and zero-sequence voltage of the faulty line and identify the tripping type of the upstream circuit breaker; the tripping type includes overcurrent tripping and residual current operated protection tripping; If any phase voltage is lower than the first set threshold and the voltages of the remaining phases are higher than the second set threshold, the fault type is determined to be a phase-to-ground fault, and the fault probability corresponding to the fault type is determined based on the current phase voltage drop and the magnitude of the zero-sequence current; otherwise, the fault probability corresponding to the fault type is determined based on the tripping type, which includes phase-to-ground fault, neutral-to-ground fault, phase-to-neutral short-circuit fault, and phase-to-phase short-circuit fault.

3. The low-voltage short-circuit fault diagnosis method based on access impedance according to claim 2, characterized in that: The steps for determining the fault probability corresponding to the fault type based on the current phase voltage drop and the zero-sequence current magnitude are as follows: Calculate the voltage drop of the faulty phase. and the zero-sequence current of the faulty circuit If zero-sequence current Greater than the zero-sequence current set threshold If so, it is determined that there is a phase-to-ground fault; according to and The magnitude of is determined by a preset probability mapping relationship to determine the fault probability corresponding to a phase-to-ground fault, where: like Then the failure probability is the first probability value. ; like Then the failure probability is the second probability value. ; like Then the failure probability is the third probability value. ; like Then the failure probability is the fourth probability value. ; in, This is the critical threshold for distinguishing the magnitude of voltage drop. .

4. The low-voltage short-circuit fault diagnosis method based on access impedance according to claim 2, characterized in that: The steps for determining the fault probability corresponding to the fault type based on the tripping type are as follows: If the residual current protection trips, and the zero-sequence current... Less than the typical value of phase-to-ground current I g1 If the fault type is determined to be a neutral ground fault, the corresponding fault probability is based on the zero-sequence current. Compared with the preset ground fault current reference value I ref The proportional relationship is determined; If the circuit breaker trips due to overcurrent and the insulation resistance between any two phases is measured to be lower than the insulation set threshold, the fault type is determined to be a phase-to-phase short circuit fault, and the corresponding fault probability is determined based on the degree to which the insulation resistance deviates from the normal value. If the trip is due to overcurrent, and only a single phase current exceeds the rated current threshold, accompanied by a synchronous increase in neutral current exceeding the current limit, then the fault type is determined to be a phase-neutral short-circuit fault, and the corresponding fault probability is determined based on the ratio of the current phase current to the rated load current.

5. The low-voltage short-circuit fault diagnosis method based on access impedance according to claim 1, characterized in that: The steps for generating a fault handling work order for the corresponding fault type based on the fault probability and the short-circuit fault handling table are as follows: Receive the predicted fault type and its corresponding fault probability, query the preset short-circuit fault handling table according to the fault type, and obtain the benchmark troubleshooting strategy corresponding to the fault type; Based on the magnitude of the failure probability, at least one controllable parameter in the baseline troubleshooting strategy is adjusted to generate an adapted troubleshooting strategy. Based on the aforementioned fault diagnosis strategy, a fault handling work order is generated, which includes impedance element access points, impedance parameters, differential search paths, detection node sequences, and safety operation instructions.

6. The low-voltage short-circuit fault diagnosis method based on access impedance according to claim 5, characterized in that: The steps for adjusting at least one controllable parameter in the baseline troubleshooting strategy according to the magnitude of the fault probability to generate an adapted fault troubleshooting strategy are as follows: The received fault probability is compared with at least two preset probability thresholds to determine the corresponding strategy adjustment mode in order to adjust the impedance element parameters in the benchmark troubleshooting strategy and switch the differential search path in the benchmark troubleshooting strategy. The adapted troubleshooting strategy is generated based on the adjusted impedance element parameters and the differential search path.

7. The low-voltage short-circuit fault diagnosis method based on access impedance according to claim 6, characterized in that: The steps for determining the corresponding strategy adjustment mode to adjust the impedance component parameters in the baseline troubleshooting strategy are as follows: If the strategy adjustment mode is the first mode, the impedance element parameters in the benchmark troubleshooting strategy are adjusted to a first capacitance value corresponding to the high short-circuit limiting capability; if the strategy adjustment mode is the second mode, the impedance element parameters are adjusted to a second capacitance value corresponding to the standard detection sensitivity.

8. The low-voltage short-circuit fault diagnosis method based on access impedance according to claim 6, characterized in that: The steps to determine the appropriate strategy adjustment mode to switch the differential search path in the baseline investigation strategy are as follows: If the strategy adjustment mode is the first mode, an optimized binary search sequence is used, and the starting detection node of the sequence is determined based on the total line length and a preset ratio; if the strategy adjustment mode is the second mode, a progressive search sequence from the power supply side to the load side is used.

9. The low-voltage short-circuit fault diagnosis method based on access impedance according to claim 6, characterized in that: The steps for determining the strategy adjustment mode are as follows: A first probability threshold α and a second probability threshold β are preset, where α>β, and the failure probability Px is compared with α and β respectively; If Px≥α, then the policy adjustment mode is determined to be the first mode; If β≤Px<α, then the policy adjustment mode is determined to be the second mode; If Px < β, then the policy adjustment mode is determined to be the third mode.

10. The low-voltage short-circuit fault diagnosis method based on access impedance according to claim 1, characterized in that: The steps for determining the faulty line section based on the difference between the first current data and the second current data are as follows: Based on the detection node sequence in the fault handling work order, before impedance connection, a first set of current data is measured and recorded at each preset detection node; after impedance connection, a second set of current data is measured and recorded at the same preset detection nodes. The current change characteristic values ​​at the corresponding detection node positions are determined based on the first current data set and the second current data set. Based on the detection node sequence, the node positions where the current change characteristic value changes abruptly are identified sequentially from the power flow direction. If the current at the preset detection node decreases by more than the current at the upstream preset detection node by a preset abrupt change threshold, the faulty line segment is determined to be located between the current preset detection node and the corresponding upstream preset detection node.

Images