A system and method for locating and identifying grounding leakage faults in low-voltage distribution networks

Abstract

This invention provides a system and method for locating and identifying grounding leakage faults in low-voltage distribution networks. The system includes: a first measuring unit installed on the low-voltage distribution trunk line for synchronously collecting the combined residual current of the three-phase phase lines and the neutral line; a second measuring unit installed on the neutral point grounding wire of the distribution transformer for collecting the grounding leakage current; a reference measuring unit for synchronously collecting three-phase voltage information; a data synchronization and communication module; and a central analysis terminal. Under synchronous conditions, the central analysis terminal compares the residual current and the grounding current to determine whether the leakage fault is located upstream or downstream of the measuring point, and identifies the faulty phase based on the phase or correlation relationship between the grounding current and the three-phase voltage. This invention can achieve rapid location, phase identification, and operational status judgment of grounding leakage faults.

Description

Technical Field

[0001] This invention relates to the field of power system safety monitoring and fault diagnosis technology, and in particular to a system and method for locating and identifying grounding leakage faults in low-voltage distribution networks. Background Technology

[0002] Currently, in low-voltage three-phase four-wire power distribution systems, the common method for detecting grounding leakage is the "four-wire clamping method," which involves simultaneously clamping three phase wires and one neutral wire with a clamp meter. This method is based on Kirchhoff's current law: when there is no leakage fault in the system, the vector sum of the current in each phase and the neutral wire should be zero; when a non-zero residual current is measured, a grounding leakage fault can be determined to exist in the system. This method is simple in structure and easy to operate, and therefore widely used in field testing.

[0003] However, the existing four-wire clamping method can only determine whether a grounding leakage fault "exists," which is insufficient to meet the needs of refined operation and maintenance and proactive safety protection. Specifically, it has the following technical limitations:

[0004] First, it is impossible to accurately locate the leakage fault point. When residual current is detected, maintenance personnel cannot determine whether the grounding leakage occurs on the upstream power supply side or the downstream load side of the measurement point, nor can they distinguish the specific location inside the distribution box, the main line, or the terminal branch. It is often necessary to locate the fault by shutting down power in stages, which is inefficient and seriously affects the reliability of power supply.

[0005] Secondly, it cannot identify the phase information of the grounding fault. The existing method only outputs a comprehensive residual current value, which cannot distinguish whether the grounding leakage is in phase A, phase B or phase C. In the case of unbalanced three-phase load or multiple branches in parallel, it is difficult to quickly locate the faulty circuit, and the maintenance lacks specificity.

[0006] Secondly, the fault information obtained is limited in scope. Traditional detection methods only focus on the residual current amplitude, lacking the collection and analysis of characteristic information such as current waveform and phase relationship. This makes it difficult to distinguish between different fault modes such as resistive leakage, capacitive leakage, or arc-type grounding, and thus cannot provide effective support for fault early warning, condition assessment, and intelligent operation and maintenance.

[0007] Therefore, there is an urgent need for a low-voltage distribution network grounding leakage fault location and identification system and method that can integrate multi-point and multi-source synchronous measurement information to achieve rapid location, phase identification and status judgment of grounding leakage faults without affecting normal power supply. Summary of the Invention

[0008] In view of the above-mentioned defects in the prior art, the purpose of this invention is to provide a system and method for locating and identifying ground leakage faults in low-voltage distribution networks, which aims to solve the technical problem that existing low-voltage distribution networks cannot accurately locate the fault location and identify the fault phase when ground leakage faults occur.

[0009] To achieve the above objectives, in a first aspect, the present invention provides a low-voltage distribution network grounding leakage fault location and identification system, comprising:

[0010] The first measurement unit is set at the measurement position of the low-voltage power distribution trunk line and is used to synchronously collect the combined residual current of the three-phase phase line and the neutral line to obtain the first residual current signal.

[0011] The second measurement unit is set on the neutral point grounding wire of the distribution transformer to collect the ground fault current returning through the earth loop and obtain the ground current signal;

[0012] Reference measurement unit, used to synchronously acquire amplitude and phase information of three-phase voltage in low-voltage distribution network;

[0013] The data synchronization and communication module is used to synchronize the first residual current signal, the ground current signal and the three-phase voltage signal in time, and send the synchronized data to the central analysis terminal.

[0014] The central analysis terminal is used to calculate the distribution relationship of leakage current upstream and downstream of the measurement point based on the synchronously acquired first residual current signal and grounding current signal, so as to determine the location of the grounding leakage fault, and to identify the phase in which the grounding leakage fault occurred based on the phase or correlation relationship between the grounding current signal and the three-phase voltage signal.

[0015] As a further improvement to the above solution, the first measuring unit is a clamp-on current sensing device, whose jaws simultaneously surround the three phase lines and the neutral line, used to obtain the residual current information of the low-voltage distribution trunk line.

[0016] In a preferred embodiment, the second measuring unit is a zero-sequence current sensor installed on the neutral point grounding lead of the distribution transformer.

[0017] As a further improvement to the above solution, the data synchronization and communication module uses a unified clock reference to timestamp multiple measurement data to ensure that data from different measurement points are analyzed under the same time reference.

[0018] As a further improvement to the above scheme, the central analysis terminal compares the grounding current signal with the first residual current signal through vector operation to obtain the leakage current component upstream of the measurement point and the leakage current component downstream of the measurement point.

[0019] As a further improvement to the above scheme, the central analysis terminal determines the phase with the highest correlation to the ground current signal as the ground leakage fault phase by calculating the phase difference or waveform correlation between the ground current signal and the three-phase voltage signal.

[0020] Secondly, the present invention also provides a method for locating and identifying grounding leakage faults in a low-voltage distribution network based on the system provided in the first aspect, comprising the following steps:

[0021] Under a unified time reference, the first residual current signal of the low-voltage distribution trunk line, the grounding current signal of the distribution transformer grounding wire, and the three-phase voltage signal are collected synchronously.

[0022] Based on the amplitude and vector relationship between the first residual current signal and the grounding current signal, it is determined whether the grounding leakage fault is located upstream or downstream of the measurement point;

[0023] Based on the phase relationship or correlation between the grounding current signal and the three-phase voltage signal, the phase in which the grounding leakage fault occurs can be identified.

[0024] Output the location of the grounding leakage fault and the corresponding fault phase information.

[0025] As a further improvement to the above scheme, when the amplitude of the first residual current signal is less than the first preset threshold and the amplitude of the grounding current signal is greater than the second preset threshold, it is determined that the grounding leakage fault is located upstream of the measurement point.

[0026] When the amplitude of the leakage current component upstream of the measurement point is less than the first preset threshold, and the amplitude and phase of the first residual current signal are consistent with those of the grounding current signal, it is determined that the grounding leakage fault is located downstream of the measurement point.

[0027] When the amplitude of the leakage current component upstream of the measurement point and the amplitude of the first residual current signal are both significantly greater than the first preset threshold, it is determined to be a mixed leakage state, and the upstream leakage ratio and the downstream leakage ratio are further calculated.

[0028] As a further improvement to the above scheme, by comparing the phase difference between the ground current signal and the three-phase voltage signal, the phase with the smallest phase difference and less than the set threshold is selected as the ground leakage fault phase.

[0029] Alternatively, calculate the cross-correlation coefficient between the ground current waveform and the voltage waveform of each phase within one cycle, and determine the phase with the highest correlation as the ground leakage fault phase.

[0030] As a further improvement to the above scheme, after completing the location and identification of ground leakage faults, the insulation status of the low-voltage distribution network is assessed or warned based on the changing trend or harmonic characteristics of the ground current signal.

[0031] Because the present invention adopts the above technical solutions, the beneficial effects of this application are as follows:

[0032] This invention provides a system for locating and identifying grounding leakage faults in low-voltage power distribution networks. The system first collects the synthetic residual current using a first measuring unit on the low-voltage distribution trunk line, and then collects the grounding leakage current using a second measuring unit on the neutral grounding line of the distribution transformer. Under a unified time reference of the data synchronization and communication modules, the current information from different measuring points is compared and analyzed. This allows for the differentiation of the leakage current distribution upstream and downstream of the measuring point, enabling rapid determination of the grounding leakage fault location without power outages, thus avoiding the need for segment-by-segment inspection in existing technologies.

[0033] Secondly, by setting up a reference measurement unit to synchronously collect the amplitude and phase information of the three-phase voltage, and then using a central analysis terminal to analyze the phase or correlation between the grounding current signal and the three-phase voltage, this technical feature can determine the phase with the most significant correlation to the grounding leakage current, thereby enabling the identification of the grounding leakage fault phase, making maintenance more targeted, and improving fault handling efficiency.

[0034] Furthermore, this invention does not rely solely on a single current detection signal, but rather achieves a multi-dimensional assessment of the grounding leakage status by simultaneously acquiring and comprehensively analyzing residual current, grounding leakage current, and three-phase voltage information. This multi-source information fusion helps reduce the impact of single measurement errors on the assessment results, improving the stability and reliability of fault location and identification.

[0035] In addition, the system of the present invention only adds current and voltage measurement units and data analysis modules to the existing low-voltage distribution network. It can realize the location and identification of ground leakage faults without changing the original power supply structure and operation mode. It is easy to implement and suitable for promotion and application in different types of low-voltage distribution network scenarios.

[0036] This invention helps improve the operational safety of low-voltage distribution networks. By rapidly identifying the location and phase of grounding leakage faults, it provides maintenance personnel with clear repair guidelines, helps shorten fault handling time, reduces the potential risks of grounding leakage to personal safety and equipment operation, and thus improves the overall operational safety of low-voltage distribution networks. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the structure of a low-voltage power distribution network grounding leakage fault location and identification system disclosed in this invention;

[0039] Figure 2 This is a schematic diagram of the core data processing and fault analysis process executed by the central analysis terminal disclosed in this invention.

[0040] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] It should be noted that the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0043] Example 1

[0044] This invention provides a low-voltage power distribution network grounding leakage fault location and identification system, which achieves accurate fault assessment through multi-point synchronous measurement. See also... Figure 1 The specific deployment of the system is as follows:

[0045] The first measuring unit is located at a measurement point on the low-voltage power distribution trunk line, such as the outgoing terminal of the low-voltage main distribution box. This first measuring unit is used to simultaneously collect current information from the three phase lines and the neutral line, and to synthesize the collected currents to obtain a first residual current signal reflecting the residual current status of the line. By obtaining the synthesized residual current at this location, the current imbalance between upstream and downstream of the line at the measurement point can be reflected, providing a basis for subsequent leakage current distribution judgment.

[0046] The second measurement unit is located on the neutral point grounding line of the distribution transformer and is used to collect the ground fault current signal returned through the earth loop. Since the ground leakage current in the low-voltage distribution network ultimately returns to the power supply side through the transformer neutral point grounding loop, by measuring at this location, the actual ground leakage current information in the system can be obtained, thus avoiding the uncertainty of judgment caused by relying on only a single measurement point.

[0047] A reference measurement unit is connected in parallel to the three-phase voltage side of the low-voltage distribution network to synchronously acquire the amplitude and phase information of the three-phase voltage. Specifically, in this embodiment, the reference measurement unit is connected in parallel between the A, B, and C three-phase busbars and the neutral line of the main distribution box to obtain the three-phase voltage U. a U b U c The amplitude and phase of the voltage provide a phase reference for identifying the faulty phase. By obtaining the three-phase voltage as a reference, the necessary basis can be provided for subsequent analysis of the correspondence between the grounding current and the voltage of each phase, thereby supporting the identification of the grounding leakage fault phase.

[0048] The data synchronization and communication module is connected to the first measurement unit, the second measurement unit, and the reference measurement unit, respectively. It performs synchronization processing on the aforementioned multi-source measurement signals under a unified time reference and sends the synchronized data to the central analysis terminal. Specifically, in this embodiment, an industrial gateway supporting the IEEE 1588 protocol is used to assign a unified timestamp to each of the original signals, ensuring that the phase analysis of the multi-source data has physical synchronicity. By introducing a time synchronization mechanism, the comparability of data acquired from different measurement locations is guaranteed, avoiding the impact of inconsistent sampling timing on the accuracy of leak fault location determination.

[0049] The central analysis terminal can be a cloud server or an industrial computer deployed in a local monitoring center. Its software platform can be developed using languages ​​such as Python, C++, or LabVIEW, integrating vector computing libraries and data analysis algorithms. It receives synchronization data from the data synchronization and communication module and compares and analyzes the first residual current signal and the grounding current signal. By analyzing the relationship between the amplitude and changing trends of the two types of currents, it can determine whether the grounding leakage current is mainly distributed upstream or downstream of the measurement point, thereby determining the location of the grounding leakage fault. Simultaneously, the central analysis terminal combines the phase or correlation relationship between the grounding current signal and the three-phase voltage signal to identify the phase with the most obvious correspondence to the grounding leakage current, thus identifying the phase of the grounding leakage fault.

[0050] By having multiple measurement units work together and perform comprehensive analysis under synchronous conditions, this embodiment can determine the location and phase of a grounding leakage fault without power interruption, thus improving the pertinence and reliability of grounding leakage fault detection in low-voltage distribution networks.

[0051] In a preferred embodiment, the first measurement unit is implemented using a clamp-on current sensing device. Specifically, the clamp-on current sensing device has a frequency response range of DC to 2kHz to accommodate the measurement of power frequency and its main harmonics. For example, a flexible current clamp similar to the Flukei400s can be selected, or its function can be integrated into a fixedly installed multi-channel current sensing device.

[0052] The clamp-on current sensing device is installed at the measurement location on the low-voltage distribution trunk line. During installation, its jaws simultaneously encircle and clamp the three-phase live wires (A, B, and C) and the neutral wire (N), enabling the clamp-on current sensing device to perform a combined measurement of the current in the three-phase and neutral wires. This results in an output analog or digital signal proportional to the sum of the four-wire current vectors, i.e., the first residual current vector I. Δ1 Because the three-phase live wire current and neutral wire current are balanced in a vector sense under normal operating conditions, the current imbalance at the measurement point can be directly reflected by using the clamps to simultaneously surround all four conductors.

[0053] By employing a clamp-on current sensor as the first measurement unit, measurements can be completed without disconnecting or modifying the existing low-voltage distribution trunk line, thus avoiding any impact on normal power supply. This method is suitable for implementation in operating low-voltage distribution networks. Simultaneously, this measurement method can acquire residual current information reflecting the overall condition of the upstream and downstream of the line at a single measurement location, providing fundamental data support for subsequent synchronous comparison with the grounding leakage current collected at the neutral point grounding wire of the distribution transformer.

[0054] In a preferred embodiment, the second measuring unit is implemented using a zero-sequence current sensor, which is installed on the grounding lead of the neutral point of the distribution transformer.

[0055] During the operation of a low-voltage distribution network, when a grounding leakage fault occurs, the leakage current returns to the neutral point grounding device of the distribution transformer via the earth loop. By installing a zero-sequence current sensor on the neutral point grounding lead, the grounding leakage current passing through this loop can be directly collected, thereby obtaining a grounding current signal reflecting the actual grounding leakage state of the system. This measurement method can avoid interference caused by complex line branch structures or unbalanced loads in the judgment of grounding leakage current.

[0056] The zero-sequence current sensor preferably adopts an open-type structure, which can be directly installed on the outside of the neutral point grounding lead without power interruption, without needing to disconnect or modify the original grounding line, making it convenient for implementation in existing distribution transformer areas. Since the zero-sequence current sensor collects the ground leakage current I after it has been collected through the earth loop... g This signal can serve as a reference for the total amount of ground leakage in the system. When the central analysis terminal further analyzes this ground current signal in conjunction with the three-phase voltage information, it can provide stable data support for the identification of the phase with ground leakage fault, thereby improving the practicality of the ground leakage fault location and identification results.

[0057] In a preferred embodiment, the data synchronization and communication module uses a unified clock reference to timestamp multiple measurement data from the first measurement unit, the second measurement unit, and the reference measurement unit.

[0058] Specifically, the data synchronization and communication module has a built-in unified clock source or uses an external clock signal for time synchronization. It assigns a corresponding timestamp to the data collected by each measurement unit at the time of generation or reception, ensuring that current and voltage signals acquired from different measurement locations have a consistent time reference. After the data is transmitted to the central analysis terminal, the terminal can align the multi-channel measurement data based on the timestamps, allowing for comparative analysis of current and voltage information at different measurement points under the same time reference. The core of the data synchronization and communication module is a data acquisition unit with precise clock synchronization capabilities. An industrial gateway supporting the IEEE 1588 (PTP) precision clock protocol is preferred, such as an embedded device using an ARM Cortex-A series processor and running a Linux system. The data synchronization and communication module integrates multiple analog / digital input channels, each connected to one of the three measurement units. It assigns a unified timestamp to the data from all input channels through an internal clock synchronization mechanism. The packaged synchronized data is then transmitted to the central analysis terminal via wired or wireless means.

[0059] By employing the above method, amplitude or phase deviations caused by inconsistent sampling times of different measurement units can be avoided. This ensures that the residual current information acquired by the first measurement unit and the grounding current information acquired by the second measurement unit are comparable during analysis, providing a stable data foundation for determining the distribution of grounding leakage current upstream or downstream of the measurement point. Furthermore, when performing phase analysis by combining the grounding current signal and the three-phase voltage signal, data under a unified time reference helps maintain the effectiveness of the phase relationship, thereby improving the reliability of grounding leakage fault location and phase identification results.

[0060] In a preferred embodiment, the central analysis terminal uses vector operation to compare and analyze the grounding current signal collected by the second measurement unit with the first residual current signal collected by the first measurement unit.

[0061] Specifically, under the unified time reference provided by the data synchronization and communication module, the central analysis terminal acquires the grounding current signal and the first residual current signal corresponding to the same moment, and processes them as current vectors. Based on the current conservation relationship in the low-voltage distribution network, by performing vector operations on the grounding current vector and the first residual current vector, the leakage current component upstream of the measurement point and the leakage current component downstream of the measurement point can be obtained.

[0062] Using the vector operation method described above, when a ground leakage fault occurs downstream of the measurement point, the first residual current signal and the ground current signal have a corresponding relationship in amplitude and trend. The central analysis terminal can then determine the leakage current component downstream of the measurement point. When a ground leakage fault exists upstream of the measurement point, the ground current signal contains current components that the first residual current signal fails to reflect. The central analysis terminal can identify the leakage current component upstream of the measurement point using vector difference. Thus, the distribution of ground leakage current upstream and downstream of the measurement point can be distinguished.

[0063] In a preferred embodiment, after determining the location of the ground leakage fault, the central analysis terminal further analyzes the phase relationship or waveform correlation between the ground current signal and the three-phase voltage signal to determine the phase in which the ground leakage fault occurred.

[0064] Specifically, under a unified time reference provided by the data synchronization and communication module, the central analysis terminal acquires the grounding current signal and three-phase voltage signals corresponding to the same moment. Based on the synchronized data, the central analysis terminal calculates the phase difference between the grounding current signal and each phase voltage signal, or calculates the waveform correlation between the grounding current signal and each phase voltage signal within a preset time window. By comparing the magnitude of the phase difference or the degree of correlation corresponding to different phases, the phase with the highest correlation to the grounding current signal is determined, and this phase is identified as the grounding leakage fault phase.

[0065] Since ground leakage current typically exhibits a more stable phase correspondence or waveform correlation with the phase where insulation failure occurs, the aforementioned analysis method allows for the differentiation of ground leakage fault phases without the need for additional measurement hardware. Combining this phase identification result with the aforementioned ground leakage fault location determination result provides maintenance personnel with more targeted fault information, helping to reduce the scope of troubleshooting and improve the efficiency and accuracy of ground leakage fault handling.

[0066] To more clearly illustrate the inventive concept of this invention, after receiving the synchronization data processed by the data synchronization and communication module, the central analysis terminal processes the data according to the following steps to realize the location and phase identification of the ground leakage fault.

[0067] For details, see Figure 2 The specific processing steps are as follows:

[0068] Data preprocessing and calibration:

[0069] The central analysis terminal receives the first residual current signal. Grounding current signal and three-phase voltage signals Perform data preprocessing.

[0070] Specifically, the current and voltage signals undergo digital filtering, for example, using a combination of 50Hz notch filtering and low-pass filtering to suppress noise interference. Simultaneously, the current and voltage channels are calibrated for amplitude and phase to eliminate inherent errors caused by sensor characteristics and the signal transmission link. The calibration coefficients can be pre-determined under conditions without grounding leakage faults by applying a standard signal.

[0071] Key vector parameter calculation:

[0072] After completing the data preprocessing, the central analysis terminal extracts the phase angle of phase A voltage from the three-phase voltage signal. Use it as a reference zero point, or select other phase references according to system configuration.

[0073] Based on this, the ground current signal is calculated. and the first residual current signal amplitude And calculate its relative to the reference phase. phase angle and .

[0074] Grounding leakage fault location analysis:

[0075] The central analysis terminal, based on Kirchhoff's current law, analyzes ground current signals. With the first residual current signal Perform vector operations to calculate the leakage current component upstream of the measurement point. :

[0076] ;

[0077] and the first residual current signal Component of leakage current downstream of the measurement point .

[0078] In some embodiments, the central analysis terminal determines fault location based on the following decision logic:

[0079] when (That is, the first preset threshold, for example, 0.1A) and When the grounding leakage fault is determined to be mainly located upstream of the measurement point (i.e., on the power supply side), it is determined that the grounding leakage fault is mainly located upstream of the measurement point.

[0080] when (that is, the first preset threshold), and At that time, it was determined that the ground leakage fault was mainly located downstream of the measurement point, that is, on the load side;

[0081] when and All significantly greater than When the threshold (i.e., the first preset threshold) is reached, the situation is determined to be a mixed leakage state, and the upstream leakage ratio is further calculated. and downstream leakage ratio The specific calculation formula is as follows:

[0082] .

[0083] Phase identification of ground leakage fault:

[0084] After determining the location of the fault, the central analysis terminal identifies the phase of the grounding leakage fault.

[0085] In some embodiments, the phase difference method is used for identification. Specifically, the phase angle of the grounding current is calculated. Phase angle with three-phase voltage The absolute difference between them:

[0086] ;

[0087] ;

[0088] ;

[0089] Find the minimum value among them. ,when When the angle is less than a set threshold (e.g., 45°), the corresponding phase will be identified as a grounding leakage fault phase.

[0090] In another implementation, or as an auxiliary judgment method, the central analysis terminal can calculate the cross-correlation coefficient between the ground current waveform and the voltage waveform of each phase within one cycle, and determine the phase with the highest correlation as the ground leakage fault phase.

[0091] Results and Alarms:

[0092] The central analysis terminal generates diagnostic information based on the above analysis results and outputs it in a structured format, including the total ground leakage current. Upstream leakage ratio Downstream leakage ratio The main fault phases and the parameters of each current vector.

[0093] when When the set safety threshold (e.g., 0.5A) is exceeded, the central analysis terminal triggers an alarm mechanism and issues an alarm message through audible and visual prompts, SMS, or platform communication.

[0094] Example 2

[0095] This invention describes a method for locating and identifying grounding leakage faults in low-voltage distribution networks. This embodiment is based on the system structure described in Example 1, and completes the location and phase identification of grounding leakage faults without affecting the normal power supply of the low-voltage distribution network. The specific implementation steps are as follows:

[0096] S1. Synchronous Data Acquisition:

[0097] Under a unified time reference, the first residual current signal at the low-voltage distribution trunk line, the grounding current signal at the neutral grounding wire of the distribution transformer, and the three-phase voltage signal of the low-voltage distribution network are collected synchronously.

[0098] By acquiring the above multi-source measurement data under a unified time reference, the temporal consistency between different measurement locations and different signal types can be guaranteed, providing a comparable data basis for subsequent comparative analysis of current amplitude, vector relationship and phase relationship, thereby avoiding judgment deviations caused by inconsistent sampling timing.

[0099] S2. Determining the location of a grounding leakage fault:

[0100] Based on the first residual current signal and the grounding current signal obtained by synchronous acquisition, the amplitude characteristics and vector relationship of the two types of current signals are analyzed to determine whether the grounding leakage fault is located upstream or downstream of the measurement point.

[0101] The central analysis terminal, based on Kirchhoff's current law, analyzes ground current signals. With the first residual current signal Perform vector operations to calculate the leakage current component upstream of the measurement point. :

[0102] ;

[0103] and the first residual current signal Component of leakage current downstream of the measurement point .

[0104] Specifically, when the amplitude of the first residual current signal is less than the first preset threshold and the amplitude of the grounding current signal is greater than the second preset threshold, the central analysis terminal determines that the grounding leakage current mainly originates from upstream of the measurement point. Since no obvious change in residual current is detected downstream of the measurement point, but a grounding current signal exists in the grounding loop, the above determination rule can reflect the situation where the grounding leakage current occurs before the measurement point, thereby enabling the identification of upstream grounding leakage faults.

[0105] When the amplitude of the leakage current component upstream of the measurement point is less than a first preset threshold, and the amplitude and phase of the first residual current signal are consistent with those of the grounding current signal, the central analysis terminal determines that the grounding leakage fault is located downstream of the measurement point. In this case, the residual current detected at the measurement point can correspond to the grounding current in the grounding loop, indicating that the grounding leakage current flows into the ground from the downstream line of the measurement point and returns to the grounding loop. By considering both amplitude and phase consistency simultaneously, misjudgments caused by relying solely on a single amplitude can be avoided, thus improving the reliability of fault location determination.

[0106] By introducing the above-mentioned determination method based on amplitude threshold and phase consistency, this embodiment can distinguish the upstream or downstream location of ground leakage fault without adding additional measuring devices, reducing the need for segment-by-segment investigation and providing a more stable judgment basis for ground leakage fault location.

[0107] When the amplitude of the leakage current component upstream of the measurement point and the amplitude of the first residual current signal are both significantly greater than the first preset threshold, a mixed leakage state is determined, and the upstream leakage ratio and downstream leakage ratio are further calculated. The specific calculation formula is as follows:

[0108] .

[0109] The above analysis method can effectively determine the location of grounding leakage faults without power interruption, reducing the workload of segment-by-segment troubleshooting.

[0110] S3. Identification of phase-specific grounding leakage faults:

[0111] After determining the fault location, the phase in which the grounding leakage fault occurred is further identified based on the phase relationship or waveform correlation between the grounding current signal and the three-phase voltage signal. This step can complete the phase identification without adding additional measuring devices, thus improving the practicality of the method.

[0112] S4. Output Results: Based on the above analysis results, output the location of the grounding leakage fault and the corresponding fault phase information, providing a clear basis for subsequent operation and maintenance. By simultaneously providing the fault location and fault phase, the scope of fault investigation can be narrowed, improving the efficiency and targeting of grounding leakage fault handling in low-voltage distribution networks.

[0113] In a preferred embodiment, the central analysis terminal determines the phase of the ground leakage fault by comparing the phase difference between the ground current signal and the three-phase voltage signal.

[0114] Specifically, after acquiring the ground current signal and three-phase voltage signal under a unified time reference, the central analysis terminal calculates the phase difference between the ground current signal and each phase voltage signal, and compares the phase differences corresponding to different phases. When the phase difference of a certain phase is the smallest among all phases, and the phase difference is less than a preset threshold, that phase is identified as the phase with the ground leakage fault.

[0115] Specifically, the phase difference method is used for identification. This involves calculating the phase angle of the grounding current. Phase angle with three-phase voltage The absolute difference between them:

[0116] ;

[0117] ;

[0118] ;

[0119] Find the minimum value among them. ,when When the angle is less than a set threshold (e.g., 45°), the corresponding phase will be identified as a grounding leakage fault phase.

[0120] By introducing a phase difference threshold as a criterion, misjudgments can be avoided when the phase relationship is not obvious or when there is significant noise interference, thus providing a clear basis for the identification of fault phases. Furthermore, since ground leakage current usually has a stronger phase correlation with the phase experiencing insulation degradation or ground faults, the above comparison method can effectively distinguish the phases of ground leakage faults without adding additional measuring devices.

[0121] In some embodiments, the central analysis terminal can calculate the cross-correlation coefficient between the ground current waveform and the voltage waveform of each phase within one cycle, and identify the phase with the highest correlation as the ground leakage fault phase.

[0122] As a preferred embodiment, after locating and identifying the phase of the grounding leakage fault, the central analysis terminal further assesses or provides early warnings on the insulation status of the low-voltage distribution network based on the changing trend or harmonic characteristics of the grounding current signal.

[0123] Specifically, the central analysis terminal records and analyzes the amplitude changes of the grounding current signal over a continuous time period. By comparing the changes in the grounding current amplitude at different times, it determines whether the grounding leakage current shows a trend of continuous increase or intensified fluctuation. When the grounding current signal shows a continuous rise or abnormal fluctuation without significant load changes, it can be used as a reference for the deterioration of the insulation condition of the low-voltage distribution network.

[0124] In another embodiment, or as a supplementary analysis method, the central analysis terminal performs frequency domain analysis on the grounding current signal, extracts the harmonic components, and compares the harmonic characteristics with reference characteristics under normal operating conditions. When abnormal harmonic components or significant changes in harmonic amplitude appear in the grounding current signal, it can be used to assist in determining the nature of the grounding leakage fault and changes in the insulation state.

[0125] Based on the above analysis results, the central analysis terminal can comprehensively assess the insulation status of the low-voltage distribution network and trigger an early warning mechanism to provide alerts to maintenance personnel when abnormal trends or characteristic changes are detected to meet preset conditions. By introducing trend and harmonic analysis on the basis of completing the location and identification of grounding leakage faults, this embodiment can provide auxiliary judgment basis for changes in the insulation status of the low-voltage distribution network without adding additional measuring devices, which is conducive to the early detection of potential fault risks and supports subsequent operation and maintenance decisions.

[0126] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct or indirect applications in other related technical fields, are within the patent protection scope of the present invention.

Claims

1. A method for locating and identifying grounding leakage faults in low-voltage distribution networks, comprising a system for locating and identifying grounding leakage faults in low-voltage distribution networks, characterized in that... The system includes a first measurement unit, which is set at the measurement position of the low-voltage power distribution trunk line and is used to synchronously collect the combined residual current of the three-phase phase line and the neutral line to obtain the first residual current signal. The second measurement unit is set on the neutral point grounding wire of the distribution transformer to collect the ground fault current returning through the earth loop and obtain the ground current signal; Reference measurement unit, used to synchronously acquire amplitude and phase information of three-phase voltage in low-voltage distribution network; The data synchronization and communication module is used to synchronize the first residual current signal, the ground current signal and the three-phase voltage signal in time, and send the synchronized data to the central analysis terminal. The central analysis terminal is used to calculate the distribution of leakage current upstream and downstream of the measurement point based on the synchronously acquired first residual current signal and grounding current signal, in order to determine the location of the grounding leakage fault. Based on the phase or correlation between the grounding current signal and the three-phase voltage signal, it identifies the phase in which the grounding leakage fault occurred. The central analysis terminal uses Kirchhoff's current law to analyze the grounding current signal... With the first residual current signal Perform vector operations to calculate the leakage current component upstream of the measurement point. : ； and the first residual current signal Component of leakage current downstream of the measurement point ; The method includes the following steps: Under a unified time reference, the first residual current signal of the low-voltage distribution trunk line, the grounding current signal of the distribution transformer grounding wire, and the three-phase voltage signal are collected synchronously. Based on the amplitude and vector relationship between the first residual current signal and the grounding current signal, it is determined whether the grounding leakage fault is located upstream or downstream of the measurement point; When the amplitude of the first residual current signal is less than the first preset threshold and the amplitude of the grounding current signal is greater than the second preset threshold, it is determined that the grounding leakage fault is located upstream of the measurement point. When the amplitude of the leakage current component upstream of the measurement point is less than the first preset threshold, and the amplitude and phase of the first residual current signal are consistent with those of the grounding current signal, it is determined that the grounding leakage fault is located downstream of the measurement point. When the amplitude of the leakage current component upstream of the measurement point and the amplitude of the first residual current signal are both significantly greater than the first preset threshold, it is determined to be a mixed leakage state, and the upstream leakage ratio and the downstream leakage ratio are further calculated. Based on the phase relationship or correlation between the grounding current signal and the three-phase voltage signal, the phase in which the grounding leakage fault occurs can be identified. Output the location of the grounding leakage fault and the corresponding fault phase information.

2. The method according to claim 1, characterized in that, By comparing the phase difference between the ground current signal and the three-phase voltage signal, the phase with the smallest phase difference that is less than a set threshold is selected as the ground leakage fault phase. Alternatively, calculate the cross-correlation coefficient between the ground current waveform and the voltage waveform of each phase within one cycle, and determine the phase with the highest correlation as the ground leakage fault phase.

3. The method according to claim 1 or 2, characterized in that, After completing the location and identification of ground leakage faults, the insulation status of the low-voltage distribution network is assessed or warned based on the changing trend or harmonic characteristics of the ground current signal.

4. The method according to claim 1 or 2, characterized in that, The first measuring unit is a clamp-on current sensing device, whose jaws simultaneously surround the three phase lines and the neutral line, and is used to obtain the residual current information of the low-voltage power distribution trunk line.

5. The method according to claim 1 or 2, characterized in that, The second measuring unit is a zero-sequence current sensor installed on the neutral point grounding lead of the distribution transformer.

6. The method according to claim 1 or 2, characterized in that, The data synchronization and communication module uses a unified clock reference to timestamp multiple measurement data, so that data from different measurement points can be analyzed under the same time reference.

7. The method according to claim 1 or 2, characterized in that, The central analysis terminal determines the phase with the highest correlation to the ground current signal as the ground leakage fault phase by calculating the phase difference or waveform correlation between the ground current signal and the three-phase voltage signal.

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