Ground fault studying and judging method, device, equipment and medium

Abstract

The invention belongs to the technical field of ground fault research and judgment, and particularly relates to a ground fault research and judgment method, device and equipment and a medium, and the method comprises the steps: obtaining a real-time phase current sampling value of a to-be-researched and judged line; the real-time phase current sampling values are synthesized into zero-sequence current, and when the abrupt change of the zero-sequence current is larger than an abrupt change threshold value, the next step is executed; obtaining a phase current sampling value of a previous cycle and a phase current sampling value of a next cycle of the fault line, and subtracting the sampling values to obtain a phase transient current increment; the difference coefficient of the transient current increment of each phase is calculated, and when the difference coefficient of one phase is larger than a first threshold value and the difference coefficients of the other two phases are smaller than a second threshold value, the section is judged as a possible fault section; for a possible fault section, reconstructing the transient current increment through a variational mode decomposition algorithm to obtain a phase transient current increment signal; and comparing the direction of the phase transient current increment signal of the possible fault section with the direction of the phase transient current increment signal of the sound section, and when the two directions are opposite, determining that the section is a fault section.

Description

Technical Field

[0001] This invention belongs to the field of grounding fault assessment technology, specifically relating to a grounding fault assessment method, device, equipment, and medium. Background Technology

[0002] Single-phase grounding faults are the main type of faults in power distribution lines. With the construction and renovation of power grids, single-phase grounding detection technology has achieved good results. The sensitivity of single-phase grounding detection technology based on transient quantity principle can reach several thousand ohms or more. In neutral point ungrounded systems, satisfactory results can also be achieved based on steady-state quantity principle.

[0003] However, existing fault identification methods based on steady-state phase current increments are based on the principle that the phase current increments generated in non-faulty sections are all currents resulting from the abrupt change in phase voltage acting on the line-to-ground capacitance, and the waveforms of their three-phase current changes are similar. The two non-faulty phases in the faulty section still follow the above pattern, but the faulty phase current increment also includes the grounding current at the fault point, hence the three-phase current increment waveforms are inconsistent. Based on the above analysis, it can be seen that by utilizing the consistent three-phase current increment waveforms in healthy sections and the significant differences in the three-phase current increment waveforms in faulty sections, fault line selection and section location can be performed.

[0004] However, resonant grounding systems typically employ overcompensation, and the relationship between the sudden changes in current between the faulted phase and the healthy phase in the fault section is as follows: Figure 1 As shown. Among them The neutral point voltage, This represents the total capacitance current to ground of the system. The inductor current generated by the arc suppression coil, For the compensated current, This is the current generated by the neutral point voltage on the phase-to-ground capacitance of each phase of the faulty line. ( The current in the faulty phase before (or after) the fault is shown in the diagram. ( Let be the current of the healthy phase before (or after) the fault. The increment of the faulty phase current can be determined using the following formula: The incremental phase current is .

[0005] Faulty circuit The increment of the fault phase current before the fault point The expression is:

[0006] In the formula: , For the line Capacitance per phase to ground. Improved phase current increment in the section The expression is:

[0007] In the formula, , For the line Capacitance to ground per phase.

[0008] The steady-state increment of the fault phase current in the faulty section is in the same direction as that of the healthy phase, and due to the compensation... The difference in the three-phase current increment waveforms in the fault section is small, and using only the steady-state increment of the three-phase current for fault location can easily lead to dead zones. Summary of the Invention

[0009] The purpose of this invention is to provide a grounding fault assessment method, apparatus, equipment and medium, which solves the problem of dead zones in the operation of single-phase grounding fault location in the prior art.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for ground fault assessment, comprising: Obtain the real-time phase current sampling value of the line to be analyzed; The real-time phase current sampling values ​​are synthesized into zero-sequence current. When the sudden change of the zero-sequence current is greater than the sudden change threshold, the phase current sampling values ​​of the previous week and the phase current sampling values ​​of the next week of the faulty line are obtained and subtracted to obtain the phase transient current increment. Calculate the difference coefficient of transient current increment for each phase. If the difference coefficient of one phase is greater than the first threshold and the difference coefficients of the other two phases are less than the second threshold, it is judged as a possible fault section; otherwise, it is judged as a healthy section. For a potentially faulty section, the transient current increment is reconstructed into a phase transient current increment signal within a characteristic frequency band using a variational mode decomposition algorithm; the direction of the phase transient current increment signal of the potentially faulty section is compared with the direction of the phase transient current increment signal of the healthy section. If the two directions are opposite, it is determined to be a faulty section; otherwise, it is a healthy section.

[0011] Preferably, in the step of obtaining the real-time phase current sampling value of the line to be analyzed, the sampling frequency is 12.8 kHz.

[0012] Preferably, the mutation threshold is 0.5~2A.

[0013] Preferably, the step of obtaining the phase current sampling values ​​of the previous week and the phase current sampling values ​​of the faulty line and subtracting them to obtain the phase transient current increment includes: ; In the formula, for f The fault phase is ink The phase transient current increment at each sampling point; After the fault φ Phase in k Phase current sampled values ​​at each sampling point; Before the fault φ Phase in k N Phase current sampled values ​​at each sampling point; N This represents the number of sampling points per cycle.

[0014] Preferably, the step of calculating the difference coefficient of transient current increment for each phase, where the difference coefficient of one phase is greater than a first threshold and the difference coefficients of the other two phases are both less than a second threshold, is determined to be a potentially faulty section; otherwise, it is determined to be a healthy section, includes: Calculate the transient current increment difference coefficient for each phase, denoted as . , , : ; ; ; In the formula, The first phase of phase A k The phase transient current increment at each sampling point; The first phase of phase A k The phase transient current increment at each sampling point; For phase B k The phase transient current increment at each sampling point; The first of phase C k The phase transient current increment at each sampling point.

[0015] Preferably, the step of reconstructing the transient current increment into a phase transient current increment signal within a characteristic frequency band for a potentially faulty section using a variational mode decomposition algorithm includes: The phase transient current increment is decomposed using the variational mode decomposition method to obtain multiple mode components; the variational mode decomposition method has 4 levels of mode decomposition and a penalty factor of 2000. Perform a Fast Fourier Transform on each modal component to obtain the spectrum of the modal component; Based on the spectrum of the modal components, the frequency point with the largest amplitude is found as the center frequency; Among them, the 150-1500Hz frequency band was selected as the characteristic frequency band, and the modal components with center frequencies in the 150-1500Hz range were added together to obtain the reconstructed phase transient current increment signal.

[0016] Preferably, the step of comparing the direction of the phase transient current increment signal of the potentially faulty section with the direction of the phase transient current increment signal of the healthy section, and determining it as a faulty section when the two directions are opposite; otherwise, it is a healthy section, includes: Calculate fault parameters based on the direction of transient current change. : ; ; In the formula, D This is the direction detection function for two phases out of the three phases; for x Phase 1 k Each sample value, for y Phase 1 k Each sample value.

[0017] In a second aspect, the present invention provides a ground fault assessment device, comprising: The acquisition module is used to acquire the real-time phase current sampling values ​​of the line to be analyzed; The first judgment module is used to synthesize the real-time phase current sampling values ​​into a zero-sequence current. When the sudden change in the zero-sequence current is greater than the sudden change threshold, the next step is executed. The calculation module is used to obtain the phase current sampling values ​​of the previous week and the next week of the faulty line, and subtract them to obtain the phase transient current increment; The second judgment module is used to calculate the difference coefficient of transient current increment of each phase. If the difference coefficient of one phase is greater than the first threshold and the difference coefficients of the other two phases are less than the second threshold, it is judged as a possible fault section; otherwise, it is judged as a healthy section. The reconstruction module is used to reconstruct the transient current increment through a variational mode decomposition algorithm for possible fault sections to obtain the phase transient current increment signal. The third judgment module is used to compare the direction of the phase transient current increment signal of the possible faulty section with the direction of the phase transient current increment signal of the healthy section. If the two directions are opposite, it is determined to be a faulty section; otherwise, it is a healthy section.

[0018] In a third aspect, the present invention provides an electronic device including a processor and a memory, wherein the processor is configured to execute a computer program stored in the memory to implement the ground fault assessment method described above.

[0019] In a fourth aspect, the present invention provides a computer-readable storage medium storing at least one instruction, which, when executed by a processor, implements the ground fault assessment method described above.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: By utilizing the characteristic that the three-phase transient current difference coefficients in the faulty section are large and the three-phase transient current difference coefficients in the healthy section are approximately equal, the possible faulty section and the healthy section can be distinguished. By using fault parameters to determine the direction of the transient current increment, the faulty section and the downstream section of the fault point can be further distinguished.

[0021] By obtaining the phase transient current increment by subtracting the sampled values ​​of the current before and after the fault, the current characteristic difference in the transient stage after the fault can be captured, avoiding the defect of small difference in steady-state current increment waveform in resonant grounding system, avoiding the dead zone of fault judgment, and improving the response sensitivity to high-resistance grounding faults and resonant system faults. By calculating the difference coefficient of transient current increment in each phase and judging the possible fault sections according to the threshold, it is possible to quickly screen out sections with fault characteristics and exclude sound sections, reduce the calculation load of subsequent in-depth analysis, realize the hierarchical logic of fault analysis from coarse screening to fine analysis, and improve the efficiency of on-site analysis of distribution terminals. The transient current increment of the potentially faulty section is reconstructed using the VMD algorithm, which can filter out invalid interference components in the transient current, specifically enhance the fault signal in the 150-1500Hz characteristic frequency band, provide a signal with obvious fault characteristics for subsequent direction judgment, avoid judgment deviation caused by interference signals, and improve the pertinence and reliability of signal processing. The methods, apparatus, media, and equipment proposed in this invention can be used in situations where it is difficult to obtain zero-sequence voltage or phase voltage, such as cable branch boxes, switching stations, and ring main units; at the same time, they have low dependence on communication, do not require voltage signals and time synchronization of adjacent detection points, and can be implemented in equipment such as power distribution terminals (FTUs), distribution terminals (DTUs), and fault indicators. Attached Figure Description

[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram showing the relationship between the sudden changes in current between the faulty phase and the healthy phase in the faulty section in the existing technology; Figure 2 This is a flowchart of a grounding fault assessment method according to Embodiment 1 of the present invention; Figure 3 This is the simulation model system of Embodiment 1 of the present invention; Figure 4 The waveform diagrams of current increments at each monitoring point in the simulation model system of Embodiment 1 of the present invention are shown. Figure 5 This is a structural block diagram of the grounding fault assessment device according to Embodiment 2 of the present invention; Figure 6 This is a structural block diagram of an electronic device according to Embodiment 3 of the present invention. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0024] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0025] Example 1 like Figures 2-4 As shown, a ground fault assessment method includes: S1. Obtain the real-time phase current sampling value of the line to be analyzed; Specifically, the sampling frequency is 12.8kHz.

[0026] S2. Combine the real-time phase current sampling values ​​into a zero-sequence current. If the sudden change in the zero-sequence current is greater than the sudden change threshold, proceed to the next step. For distribution terminals where three-phase / zero-sequence voltage and zero-sequence current cannot be obtained, the three-phase currents are synthesized into a zero-sequence current in real time. When the sudden change in zero-sequence current exceeds the sudden change threshold... I set When the fault detection method is activated, considering that fault activation requires a certain sensitivity to high-resistivity grounding faults, a current surge threshold is set. I set The value is 0.5~2A.

[0027] S3. Obtain the phase current sampling values ​​of the faulty line one week before and the phase current sampling values ​​of the next week, and subtract them to obtain the phase transient current increment. After the transient zero-sequence current surge reaches the start-up condition, the fault waveform with time stamp is saved, the current sampling value of the previous phase before the fault is memorized, and then the current increment is obtained by subtracting the current sampling value after the fault, as shown below: ; in This represents the number of sampling points per wave. This is the sampled value of the phase current after the fault. This is the sampled value of the phase current before the fault.

[0028] S4. Calculate the difference coefficient of transient current increment for each phase. If the difference coefficient of one phase is greater than the first threshold and the difference coefficients of the other two phases are less than the second threshold, it is judged as a possible fault section; otherwise, it is judged as a healthy section. Specifically, the transient current increment difference coefficient for each phase is calculated and denoted as... , , : ; ; ; In the formula, The first phase of phase A k The phase transient current increment at each sampling point; The first phase of phase A k The phase transient current increment at each sampling point; For phase B k The phase transient current increment at each sampling point; The first of phase C k The phase transient current increment at each sampling point.

[0029] A preliminary ground fault assessment is made based on the value of the transient current increment difference coefficient. This assumes that the following conditions are generally met. , This is the difference between the system's zero-mode capacitance and the zero-mode capacitance downstream of the fault point. This refers to the zero-mode capacitance of the faulty line. Specifically, the difference coefficient of the faulty phase in the faulty section is greater than 0.6, while the difference coefficients of the healthy phases are all less than 0.2.

[0030] As a preferred example of the above embodiments, based on the actual field calculation error, if one phase coefficient is greater than 0.57 and the other two phase coefficients are less than 0.2, then the section is a possible fault section; otherwise, it is a healthy section.

[0031] S5. For potentially faulty sections, the transient current increment within the characteristic frequency band is reconstructed using a variational mode decomposition algorithm to obtain the phase transient current increment signal. Specifically, the phase transient current increment is decomposed using the variational mode decomposition method to obtain multiple mode components; the variational mode decomposition method has 4 mode decomposition levels and a penalty factor of 2000. Perform a Fast Fourier Transform on each modal component to obtain the spectrum of the modal component; Based on the spectrum of the modal components, the frequency point with the largest amplitude is found as the center frequency; Among them, the 150-1500Hz frequency band was selected as the characteristic frequency band. Within this characteristic frequency band, the fault characteristics of the transient signal are more obvious, that is, the fault direction is more obvious when judging within this frequency band. The modal components with center frequencies in the 150-1500Hz range were selected and added together to obtain the reconstructed phase transient current increment signal.

[0032] S6. Compare the direction of the phase transient current increment signal of the possible faulty section with the direction of the phase transient current increment signal of the healthy section. If the two directions are opposite, it is determined to be a faulty section; otherwise, it is a healthy section.

[0033] For the reconstructed phase transient current data, fault parameters are calculated based on the direction of the transient current change. The calculation formula is shown below. When When the direction of change of the three-phase transient current is the same, it is determined to be a healthy section. When the direction of the change in the three-phase transient current is opposite, it is determined to be a fault section. Considering the actual operating conditions, it is determined to be a fault section.

[0034] ; ; In the formula, D This is the direction detection function for two phases out of the three phases; for x Phase 1 k Each sample value, for y Phase 1 k Each sample value; x ≠ y , x Choose any one of phases A, B, or C. y Choose any one of phases A, B, or C.

[0035] Specific application examples: like Figure 3 As shown in the figure, a simulation model of a 10kV low-current grounding system was built based on PSCAD. The sampling frequency is 12.8kHz. The system has four main feeders: L1 and L2 are overhead lines, and the rest are cable lines. When switch K is closed, it is an arc suppression coil grounding system with an overcompensation of 5%.

[0036] Example 1: A 10Ω ground fault occurs on line L1, 15km from the busbar. The transient increments at each detection point after one cycle are as follows: Figure 4 As shown, Figure 4 (a) is the waveform of the transient incremental current upstream of the fault point. The waveforms of the transient incremental current of the two healthy phases are basically the same, and the transient incremental current of the fault phase is much larger than that of the non-fault phase. Figure 4(b) shows the transient incremental current waveform of the non-faulty line, and the three-phase transient incremental current waveforms are roughly the same. Figure 4 (c) and Figure 4 (d) is the transient incremental current waveform of the downstream phase of the fault point. The transient incremental current waveforms of the two healthy phases are basically the same. The oscillation frequency of the fault phase is not the same as that of the healthy phase. Moreover, the oscillation frequency is affected by the length of the downstream line of the fault point. The shorter the length, the faster the oscillation frequency.

[0037] The calculated transient current increment difference coefficients for each phase at each monitoring point are shown in Table 1. It can be observed that the three-phase current increment difference coefficients at monitoring points 1 and 3 conform to the characteristics of a possible fault section, while the three-phase current increment difference coefficients at monitoring points 2 and 4 conform to the characteristics of a non-fault section.

[0038] Table 1. Difference coefficients of the three phases at each monitoring point

[0039] Since monitoring points 1 and 3 are potential fault sections, the direction of the phase transient current increment is used for auxiliary judgment. After extracting the characteristic frequency band according to the VMD decomposition algorithm, the results are shown in Table 2. Table 2. Possible Fault Sections value

[0040] Example 2: The current increment difference coefficients corresponding to the above model when the grounding point transition resistance is 1000Ω and the fault occurs near the zero crossing of the phase voltage are shown in Table 3. According to the method proposed in this invention, monitoring point 1 can be determined as a possible fault section.

[0041] Table 3. Difference coefficients when the fault occurs near the voltage zero crossing point and the transition resistance is 1000 ohms.

[0042] The direction of the phase transient current increment at monitoring point 1 is used for auxiliary judgment to further clarify whether it is a fault section. After extracting the characteristic frequency band according to the VMD decomposition algorithm, calculations are performed. The result is -1, indicating a faulty section.

[0043] Example 2 like Figure 4 As shown, based on the same inventive concept as the above embodiments, the present invention also provides a grounding fault assessment device, comprising: The acquisition module is used to acquire the real-time phase current sampling values ​​of the line to be analyzed; The first judgment module is used to synthesize the real-time phase current sampling values ​​into a zero-sequence current. When the sudden change in the zero-sequence current is greater than the sudden change threshold, the next step is executed. The calculation module is used to obtain the phase current sampling values ​​of the previous week and the next week of the faulty line, and subtract them to obtain the phase transient current increment; The second judgment module is used to calculate the difference coefficient of transient current increment of each phase. If the difference coefficient of one phase is greater than the first threshold and the difference coefficients of the other two phases are less than the second threshold, it is judged as a possible fault section; otherwise, it is judged as a healthy section. The reconstruction module is used to reconstruct the transient current increment through a variational mode decomposition algorithm for possible fault sections to obtain the phase transient current increment signal. The third judgment module is used to compare the direction of the phase transient current increment signal of the possible faulty section with the direction of the phase transient current increment signal of the healthy section. If the two directions are opposite, it is determined to be a faulty section; otherwise, it is a healthy section.

[0044] Example 3 like Figure 5 As shown, the present invention also provides an electronic device 100 for implementing a ground fault assessment method; The electronic device 100 includes a memory 101, at least one processor 102, a computer program 103 stored in the memory 101 and executable on at least one processor 102, and at least one communication bus 104.

[0045] The memory 101 can be used to store the computer program 103. The processor 102 implements the steps of the ground fault assessment method of Embodiment 1 by running or executing the computer program stored in the memory 101 and calling the data stored in the memory 101.

[0046] The memory 101 may primarily include a program storage area and a data storage area. The program storage area may store the operating system, application programs required for at least one function (such as sound playback function, image playback function, etc.), etc.; the data storage area may store data created based on the use of the electronic device 100 (such as audio data), etc. In addition, the memory 101 may include non-volatile memory, such as hard disk, RAM, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other non-volatile solid-state storage device.

[0047] At least one processor 102 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Processor 102 may be a microprocessor or any conventional processor. Processor 102 is the control center of electronic device 100, connecting various parts of electronic device 100 via various interfaces and lines.

[0048] The memory 101 in the electronic device 100 stores multiple instructions to implement a ground fault assessment method, and the processor 102 can execute multiple instructions to achieve the following: Obtain the real-time phase current sampling value of the line to be analyzed; The real-time phase current sampling values ​​are synthesized into a zero-sequence current. If the abrupt change in the zero-sequence current is greater than the abrupt change threshold, the next step is executed. The phase current sampling values ​​of the faulty line in the previous week and the phase current sampling values ​​in the following week are obtained and subtracted to obtain the phase transient current increment. Calculate the difference coefficient of transient current increment for each phase. If the difference coefficient of one phase is greater than the first threshold and the difference coefficients of the other two phases are less than the second threshold, it is judged as a possible fault section; otherwise, it is judged as a healthy section. For potentially faulty sections, the transient current increment is reconstructed using a variational mode decomposition algorithm to obtain the phase transient current increment signal; The direction of the phase transient current increment signal of the potentially faulty section is compared with the direction of the phase transient current increment signal of the healthy section. If the two directions are opposite, it is determined to be a faulty section; otherwise, it is a healthy section.

[0049] Example 4 If the modules / units integrated in the electronic device 100 are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, and read-only memory (ROM).

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for diagnosing grounding faults, characterized in that, include: Obtain the real-time phase current sampling value of the line to be analyzed; The real-time phase current sampling values ​​are synthesized into zero-sequence current. When the sudden change of the zero-sequence current is greater than the sudden change threshold, the phase current sampling values ​​of the previous week and the phase current sampling values ​​of the next week of the faulty line are obtained and subtracted to obtain the phase transient current increment. Calculate the difference coefficient of transient current increment for each phase. If the difference coefficient of one phase is greater than the first threshold and the difference coefficients of the other two phases are less than the second threshold, it is judged as a possible fault section; otherwise, it is judged as a healthy section. For a potentially faulty section, the transient current increment is reconstructed into a phase transient current increment signal within a characteristic frequency band using a variational mode decomposition algorithm; the direction of the phase transient current increment signal of the potentially faulty section is compared with the direction of the phase transient current increment signal of the healthy section. If the two directions are opposite, it is determined to be a faulty section; otherwise, it is a healthy section.

2. The grounding fault assessment method as described in claim 1, characterized in that, In the step of obtaining the real-time phase current sampling value of the line to be analyzed, the sampling frequency is 12.8 kHz.

3. The grounding fault assessment method as described in claim 1, characterized in that, The mutation threshold is 0.5~2A.

4. The grounding fault assessment method as described in claim 1, characterized in that, The step of obtaining the phase current sampling values ​​of the faulty line one week before and the phase current sampling values ​​of the next week and subtracting them to obtain the phase transient current increment includes: ； In the formula, for f The fault phase is in k The phase transient current increment at each sampling point; For the aftermath of the fault φ Phase in k Phase current sampled values ​​at each sampling point; Before the fault φ Phase in k N Phase current sampled values ​​at each sampling point; N This represents the number of sampling points per cycle.

5. The grounding fault assessment method as described in claim 4, characterized in that, The difference coefficient of transient current increment of each phase is calculated. If the difference coefficient of one phase is greater than the first threshold and the difference coefficients of the other two phases are less than the second threshold, it is judged as a possible fault section. Otherwise, the steps to determine a healthy section include: Calculate the transient current increment difference coefficient for each phase, denoted as . , , : ； ； ； In the formula, The first phase of phase A k The phase transient current increment at each sampling point; The first phase of phase A k The phase transient current increment at each sampling point; For phase B k The phase transient current increment at each sampling point; The first of phase C k The phase transient current increment at each sampling point; N This represents the number of sampling points per cycle.

6. The grounding fault assessment method as described in claim 1, characterized in that, The step of reconstructing the transient current increment into a phase transient current increment signal within a characteristic frequency band using a variational mode decomposition algorithm for potentially faulty sections includes: The phase transient current increment is decomposed using the variational mode decomposition method to obtain multiple mode components; the variational mode decomposition method has 4 levels of mode decomposition and a penalty factor of 2000. Perform a Fast Fourier Transform on each modal component to obtain the spectrum of the modal component; Based on the spectrum of the modal components, the frequency point with the largest amplitude is found as the center frequency; Among them, the 150-1500Hz frequency band was selected as the characteristic frequency band, and the modal components with center frequencies in the 150-1500Hz range were added together to obtain the reconstructed phase transient current increment signal.

7. The grounding fault assessment method as described in claim 1, characterized in that, The direction of the phase transient current increment signal of the possible faulty section is compared with the direction of the phase transient current increment signal of the healthy section. When the two directions are opposite, it is determined to be a faulty section. Otherwise, the steps for a complete section include: Calculate fault parameters based on the direction of transient current change. : ； ； In the formula, D This is the direction detection function for two phases out of the three phases; for x Phase 1 k Each sample value, for y Phase 1 k Each sample value.

8. A grounding fault detection device, characterized in that, include: The acquisition module is used to acquire the real-time phase current sampling values ​​of the line to be analyzed; The first judgment module is used to synthesize the real-time phase current sampling values ​​into a zero-sequence current. When the sudden change in the zero-sequence current is greater than the sudden change threshold, the next step is executed. The calculation module is used to obtain the phase current sampling values ​​of the previous week and the next week of the faulty line, and subtract them to obtain the phase transient current increment; The second judgment module is used to calculate the difference coefficient of transient current increment of each phase. If the difference coefficient of one phase is greater than the first threshold and the difference coefficients of the other two phases are less than the second threshold, it is judged as a possible fault section; otherwise, it is judged as a healthy section. The reconstruction module is used to reconstruct the transient current increment through a variational mode decomposition algorithm for possible fault sections to obtain the phase transient current increment signal. The third judgment module is used to compare the direction of the phase transient current increment signal of the possible faulty section with the direction of the phase transient current increment signal of the healthy section. If the two directions are opposite, it is determined to be a faulty section; otherwise, it is a healthy section.

9. An electronic device, characterized in that, It includes a processor and a memory, the processor being used to execute a computer program stored in the memory to implement the ground fault assessment method as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores at least one instruction, which, when executed by a processor, implements the ground fault assessment method as described in any one of claims 1 to 7.

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