Single-phase earth fault line selection method and system based on zero-sequence current mode decomposition

Abstract

The invention belongs to the technical field of power distribution network ground fault line selection, and provides a single-phase ground fault line selection method and system based on zero-sequence current mode decomposition, and the technical scheme is as follows: obtaining zero-sequence current and nth harmonic current; calculating the total harmonic distortion rate of the current according to the zero-sequence current and the nth harmonic current, and determining the maximum and minimum value of the distortion rate of the zero-sequence current; if the maximum value of the zero-sequence current distortion rate is far greater than the minimum value, the outgoing line has a fault, the zero-sequence transient current signal of each line is decomposed by using full-noise-assisted aggregation empirical mode decomposition to obtain an IMF component of each line, and the IMF component of each line is calculated; linear Gaussian fuzzy information granulation is carried out on the IMF component of each line to obtain a membership function of linear Gaussian fuzzy information particles, a fuzzy entropy is solved according to the membership function, and a single-phase earth fault line is determined according to the fuzzy entropy; if the maximum value of the zero-sequence current distortion rate is equal to the minimum value, the bus breaks down. And the fault type can be quickly and accurately judged.

Description

Technical Field

[0001] The present invention belongs to the technical field of ground fault line selection in distribution network, and in particular relates to a single-phase ground fault line selection method and system based on zero-sequence current modal decomposition. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] In the power distribution network, there are two main ways to ground the neutral point: one is ungrounded, and the other is grounded through an arc suppression coil. In the power system, ground faults and phase-to-phase short circuits are the most common types of faults, which pose a great threat to the safe operation of the system. Statistics show that the incidence of single-phase grounding faults is very high, usually accounting for more than 80% of all faults. If this fault is not handled for a long time, it may cause arc grounding overvoltage, damage the insulation of the system, and may even cause phase-to-phase short circuits, causing the protection device to operate, thereby affecting the stable operation of the power system.

[0004] Although a variety of line selection methods have been proposed for the line selection problem of single-phase grounding faults, such as zero-sequence current method, first half-wave method, correlation analysis method and signal injection method, these methods all have certain limitations and have not yet completely solved the line selection problem.

[0005] For example, although the zero-sequence current comparison method is applicable to systems with ungrounded neutral points, it is not applicable to arc suppression coil grounding systems. The first half-wave rule uses the polarity of the first half cycle of the transient zero-sequence current after the fault occurs to determine the fault line. This method is not affected by the arc suppression coil and is applicable to systems with arc suppression coil grounding. However, the large amount of harmonics generated when a fault occurs may interfere with the detection of zero-sequence current and increase the difficulty of line selection. Although some methods such as the signal injection method and the fifth harmonic method provide different line selection ideas, they each have their own limitations. For example, the signal injection method may be interfered by the working signal, while the fifth harmonic rule requires additional equipment and it is difficult to achieve accurate line selection and positioning in lines with many branches.

[0006] The method of using transient quantities for line selection can effectively utilize the transient fault components generated during ground faults, which usually have high content and amplitude. Modern mathematical analysis methods also provide technical support for the analysis of these transient high-frequency signals. However, this method has high requirements for signal capture accuracy and requires high sampling and processing capabilities, which not only puts higher requirements on the performance of the line selection device, but also increases the cost accordingly. With the development of the power system, the access ratio of new energy sources such as photovoltaic and wind power continues to increase. These new energy sources are accompanied by a large number of power electronic equipment when connected to the grid, resulting in a significant increase in the injection of high-frequency harmonic currents in the power grid, especially in high-frequency harmonic components above the 13th order. These factors have brought challenges to the method of using transient components for line selection, which may lead to line selection failure or misjudgment.

[0007] Traditional steady-state quantity methods have problems of insufficient sensitivity and slow response speed in line selection, which makes it difficult to meet the protection needs of the rapid development of modern power grids. Many steady-state quantity line selection methods may lead to line selection failure or misjudgment due to weak theoretical foundations or defects in the methods themselves, bringing additional risks to the safe and stable operation of the power grid. For the neutral point arc suppression coil grounding system, after single-phase grounding occurs, due to the compensation effect of the arc suppression coil, the single-phase grounding fault current is small, which is not conducive to fault line selection. If the fault is not eliminated in time, it will cause the fault to expand further and threaten the safe operation of the power grid. Summary of the invention

[0008] In order to solve at least one technical problem existing in the above-mentioned background technology, the present invention provides a single-phase ground fault line selection method and system based on zero-sequence current modal decomposition, which introduces multiple criteria of current total harmonic distortion rate and fuzzy entropy, combines the method of complete noise-assisted aggregated empirical mode decomposition and linear Gaussian fuzzy information granules, and comprehensively considers the transient characteristics and complexity of the signal. This method can not only determine whether the fault occurs on the busbar or the outgoing line, but also accurately locate the fault line through the difference of fuzzy entropy, thereby improving the reliability and accuracy of fault line selection.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] A first aspect of the present invention provides a single-phase ground fault line selection method based on zero-sequence current modal decomposition, comprising the following steps:

[0011] Obtain zero-sequence current and nth harmonic current;

[0012] Calculate the total harmonic distortion rate of current according to zero-sequence current and nth harmonic current, and determine the maximum value of zero-sequence current distortion rate;

[0013] If the maximum value of the zero-sequence current distortion rate is much greater than the minimum value, the outgoing line fails. The zero-sequence transient current signal of each line is decomposed using full noise-assisted aggregated empirical mode decomposition to obtain the IMF component of each line. The IMF component of each line is subjected to linear Gaussian fuzzy information granulation to obtain the membership function of the linear Gaussian fuzzy information granule. The fuzzy entropy is calculated based on the membership function, and the single-phase grounding fault line is determined based on the fuzzy entropy. If the maximum value of the zero-sequence current distortion rate is equal to the minimum value, the bus fails.

[0014] Furthermore, the calculation method of the total harmonic distortion rate of the current is:

[0015] The effective values ​​of all harmonic currents are squared and summed, and then the square root is taken to obtain the harmonic current content. The harmonic current content is then compared with the effective value of the fundamental current and multiplied by 100% to obtain the total harmonic distortion rate of the current in percentage form.

[0016] Furthermore, the method of decomposing the zero-sequence transient current signal of each line by using the full noise assisted aggregated empirical mode decomposition includes:

[0017] Step 1: Add the positive and negative white noise pairs to the original signal to obtain the first new signal, and perform M EMD decompositions on the first new signal to obtain M first-order IMF components;

[0018] Step 2: Calculate the mean of M first-order IMF components to obtain the first-order IMF components and the first-order residual;

[0019] Step 3: Add the positive and negative paired white noise IMF signals obtained by EMD decomposition to the first-order residual to obtain the second new signal, and perform EMD on the second new signal M times to obtain M second-order IMF components, and average them to obtain the second-order IMF components and the second-order residual;

[0020] Step 4: Repeat steps 1 to 3 until the number of extreme points of the residual component is less than 2, and obtain k IMF components and residual components.

[0021] Furthermore, the membership function of the linear Gaussian fuzzy information granule is:

[0022]

[0023] Among them, kt+b is called the center line of the LFIG, k, b∈R represent the slope and intercept of the center line; σ is called the discrete degree of the LFIG, T and x represent the data values ​​corresponding to each time point in the total time series and the time series respectively.

[0024] Furthermore, the line with the largest fuzzy entropy is taken as the pending fault line.

[0025] Furthermore, the method for obtaining zero-sequence current and nth harmonic current is: real-time monitoring of the bus voltage and zero-sequence voltage, judging the relationship between the zero-sequence voltage and the phase voltage, and when the zero-sequence voltage and the phase voltage reach a set relationship, obtaining the zero-sequence current and nth harmonic current through a detection device.

[0026] Furthermore, if the absolute value of the difference between the maximum value and the minimum value of the zero-sequence current distortion rate is less than a set threshold and the maximum value of the zero-sequence current distortion rate is not equal to the minimum value, an audible and visual alarm instruction is issued.

[0027] A second aspect of the present invention provides a single-phase ground fault line selection system based on zero-sequence current modal decomposition, comprising:

[0028] A data acquisition module, which is used to acquire zero-sequence current and nth harmonic current;

[0029] A zero-sequence current distortion rate calculation module is used to calculate the total harmonic distortion rate of the current according to the zero-sequence current and the nth harmonic current, and determine the maximum value of the zero-sequence current distortion rate;

[0030] A fault judgment module is used to determine that if the maximum value of the zero-sequence current distortion rate is much greater than the minimum value, the outgoing line fails. The zero-sequence transient current signal of each line is decomposed by full noise-assisted aggregated empirical mode decomposition to obtain the IMF component of each line. The IMF component of each line is subjected to linear Gaussian fuzzy information granulation to obtain the membership function of the linear Gaussian fuzzy information granule. The fuzzy entropy is obtained according to the membership function, and the single-phase grounding fault line is determined according to the fuzzy entropy; if the maximum value of the zero-sequence current distortion rate is equal to the minimum value, the bus fails.

[0031] A third aspect of the present invention provides a computer-readable storage medium.

[0032] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps in the single-phase grounding fault line selection method based on zero-sequence current modal decomposition as described above.

[0033] A fourth aspect of the present invention provides a computer device.

[0034] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps in the single-phase ground fault line selection method based on zero-sequence current modal decomposition as described above are implemented.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. In view of the incomplete consideration of traditional fault detection methods, which easily leads to failure or misjudgment of line selection, the present invention introduces the current total harmonic distortion rate and fuzzy entropy multiple criteria, combines the method of complete noise-assisted aggregated empirical mode decomposition and linear Gaussian fuzzy information granules, and comprehensively considers the transient characteristics and complexity of the signal. This method can not only determine whether the fault occurs on the busbar or the outgoing line, but also accurately locate the fault line through the difference of fuzzy entropy, reducing the incomplete consideration problem in traditional methods and improving the reliability and accuracy of fault line selection.

[0037] 2. In view of the fact that fault transient signals are short in time and highly mutated, and are easily affected by data acquisition asynchrony and signal processing equipment delays, the present invention uses the total harmonic distortion rate of current to determine the location of the fault. This method determines the fault location by comparing the zero-sequence current distortion rate of the fault line with that of the non-fault line. Since the harmonic distortion rate is mainly caused by the difference between the steady-state component and the transient DC component, this method is more sensitive to the instantaneous characteristics of the fault signal, and effectively reduces the impact of data acquisition asynchrony and signal processing equipment delays on fault line selection.

[0038] 3. In view of the fact that the existing methods are easily affected by harmonic interference, which leads to misjudgment of faulty lines, the present invention decomposes the zero-sequence transient current signals of each line through completely noise-assisted aggregate empirical mode decomposition (CEEMD), and combines the fuzzification processing of linear Gaussian fuzzy information particles. The calculation of fuzzy entropy can effectively quantify the complexity and uncertainty of the signal. Since the zero-sequence current signal of the faulty line changes more significantly than other normal lines, after signal decomposition and fuzzy entropy calculation, the signal characteristics of the faulty line will be significantly different from those of other lines. This method can reduce the impact of harmonic interference on faulty line selection, thereby improving the accuracy of faulty line identification.

[0039] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0041] Figure 1 It is a flow chart of a single-phase grounding fault line selection method based on zero-sequence current modal decomposition provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0043] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0044] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0045] The technical problems to be solved by the present invention are as follows:

[0046] 1. Fault transient signals are short and highly mutated, and are easily affected by asynchronous data acquisition and delays in signal processing equipment. The working principles of high-speed sampling equipment and equipment that processes transient high-frequency signals are relatively complex. In addition, it is difficult to quickly and accurately determine the type of fault.

[0047] 2. In modern power grids, due to the access of a large number of new energy sources, the power electronic equipment that follows has introduced a large number of high-frequency harmonics. In the line selection method, it is usually adopted to extract the transient high-frequency fault signal after the fault occurs and analyze its characteristics to determine the fault line. However, these methods are easily affected by harmonic interference, resulting in misjudgment of the fault line.

[0048] 3. In the power system, fault signals may contain ambiguous and uncertain information, which brings challenges to fault signal analysis and fault location. In addition, traditional fault detection methods may not be sensitive or accurate enough in some cases, especially in the case of high-resistance grounding faults. The methods proposed in the past have problems such as imperfect method mechanisms and incomplete considerations, which can easily lead to failure or misjudgment of line selection. It is necessary to analyze the mechanism of line selection methods, improve the principles of fault line selection methods, and propose new distribution network single-phase grounding fault line selection methods.

[0049] In view of the above problems, the present invention proposes a single-phase grounding fault line selection method based on zero-sequence current modal decomposition. The zero-sequence transient current signal of each line can be decomposed by completely noise-assisted aggregated empirical mode decomposition, and then the fuzzy signal is granulated using linear fuzzy information particles. The commonly used triangular information particles and interval information particles directly use the numerical size information of the time series to establish fuzzy information particles, ignoring the time information of the data. These fuzzy information particles fail to reflect the trend of the time series, and thus cannot accurately describe the original time series. In order to overcome this problem, linear Gaussian fuzzy information particles that consider the trend of the time series are used here. Through the membership function of the fuzzy set, fuzzy entropy calculation is performed, and comparison can be made to select the single-phase grounding fault line according to the numerical size. This method can reduce the impact of harmonic interference on fault line selection, reduce the problem of incomplete consideration in traditional methods, and thus improve the accuracy of fault line identification.

[0050] Embodiment 1

[0051] This embodiment provides a single-phase ground fault line selection method based on zero-sequence current modal decomposition, comprising the following steps:

[0052] Step 1: Obtain zero-sequence current and nth harmonic current;

[0053] The method for obtaining the zero-sequence current and the nth harmonic current is: real-time monitoring of the voltage and zero-sequence voltage of the busbar, judging the relationship between the zero-sequence voltage and the phase voltage, and when the zero-sequence voltage and the phase voltage reach a set relationship, obtaining the zero-sequence current and the nth harmonic current through a detection device;

[0054] In this embodiment, when the zero-sequence voltage is greater than 1.15 times the phase voltage, the zero-sequence current and the nth harmonic current are obtained.

[0055] Step 2: Calculate the total harmonic distortion rate of current according to the zero-sequence current and the nth harmonic current, and determine the maximum value of the zero-sequence current distortion rate;

[0056] The calculation method of the total harmonic distortion rate of the current is as follows:

[0057] The effective values ​​of all harmonic currents are squared and summed, and then the square root is taken to obtain the harmonic current content. The harmonic current content is then compared with the effective value of the fundamental current and multiplied by 100% to obtain the total harmonic distortion rate of the current in percentage form.

[0058] The specific calculation formula is:

[0059] If there are n lines in the system, the harmonic content and total harmonic distortion rate of the kth line are:

[0060]

[0061]

[0062] Among them, I1 is the effective value of the fundamental current, I n It is the effective value of the current of the nth harmonic.

[0063] Step 3: Determine whether the maximum value of the zero-sequence current distortion rate is much greater than the minimum value. If so, the outgoing line fails. If the maximum value of the zero-sequence current distortion rate is equal to the minimum value, the bus fails.

[0064] The harmonics in the zero-sequence current of the line mainly come from the decomposition of the transient DC component. The difference between the transient DC components of the fault line and the non-fault line is small, while the steady-state component of the fault line is much larger than that of the non-fault line. Therefore, the transient DC component of the non-fault line has a much greater impact on the steady-state component than the fault line, and finally presents that the zero-sequence current waveform distortion rate of the non-fault line is much greater than that of the non-fault line. This indicator can be used as a preliminary basis for determining the location of the line fault. In addition, find the maximum value of the zero-sequence current distortion rate in all outgoing lines and compare them. If the maximum value is equal to the minimum value, the busbar is faulty, and if the maximum value is much greater than the minimum value, it means that the fault occurs on the outgoing line rather than the busbar.

[0065] Step 4: If the fault occurs on the outgoing line, the zero-sequence transient current signal of each line is decomposed using full noise-assisted aggregated empirical mode decomposition, and the fuzzy signal is granulated using linear fuzzy information particles to obtain the fuzzy entropy. The single-phase grounding fault line is determined based on the fuzzy entropy.

[0066] The specific steps include:

[0067] Step 401: Decomposing the zero-sequence transient current signal of each line by using the total noise-assisted aggregated empirical mode decomposition (CEEMDAN), including:

[0068] Step 4011: First, add the positive and negative white noise pairs to the original signal s(t) to form a new signal x0(t), and perform M EMD decompositions on the new signal to obtain M first-order IMF components imf1 i (t), that is:

[0069] x0(t)=s(t)+(-1) q a0n i (t) = imf1 i (t)+r1 i (t) (3),

[0070] Where n i (t) is the white noise added to the original signal by the i-th EMD decomposition; i = 1, 2, ... M; a0 is the amplitude of the white noise; r1 i (t) is the first remaining residue.

[0071] Step 4012: Then for M imf1 i (t) calculate the mean and obtain the first-order IMF component

[0072]

[0073] The first-order residual r1(t):

[0074]

[0075] Step 4013: Decompose the positive and negative paired white noise IMF signals (-1) using EMD q a1E1(n i (t)), add it to r1(t) to form a new signal x1(t), perform M EMD on the new signal x1(t) to obtain M second-order IMF components And take the average value to get the second-order IMF component Thus, the second-order residual r2(t) can also be obtained, that is:

[0076]

[0077] Step 4014: Repeat the above steps until the remaining component r k The number of extreme points of (t) is less than 2, and finally k IMF components and residual components R(t) are obtained. The final original signal s(t) can be expressed as:

[0078]

[0079] Step 402: performing linear Gaussian fuzzy information granulation on the IMF components of each line to obtain the membership function of the linear Gaussian fuzzy information granules;

[0080] Through the above-mentioned complete noise-assisted aggregated empirical mode decomposition, the zero-sequence transient current signal of each line can be decomposed, and then the linear fuzzy information particles are used to granulate the fuzzy signal. The commonly used triangular information particles and interval information particles directly use the numerical size information of the time series to establish fuzzy information particles, ignoring the time information of the data. These fuzzy information particles fail to reflect the trend of the time series, and thus cannot accurately describe the original time series. In order to overcome this problem, linear Gaussian fuzzy information particles that consider the trend of the time series are used here. The fuzzy entropy is calculated after granulation. The fuzzy entropy can be used to quantify the complexity and uncertainty of the signal. Since the zero-sequence current signal of the fault line changes more than other normal lines when the system is running, the results after signal decomposition and fuzzy entropy calculation will have a significant difference from other line results, thereby determining the specific outgoing line where the single-phase grounding fault occurs.

[0081] Linear Gaussian fuzzy information granule L LFIG The membership function of (k,b,σ,T) is:

[0082]

[0083] Among them, kt+b is called the center line of the LFIG, k, b∈R represent the slope and intercept of the center line; σ is called the discrete degree of the LFIG, T and x represent the data values ​​corresponding to each time point in the total time series and the time series respectively.

[0084] Step 403: fuzzy entropy calculation is performed through the membership function of the above fuzzy set, and comparison is performed to select the single-phase grounding fault line according to the value size.

[0085] In this embodiment, the line with the largest fuzzy entropy is taken as the pending fault line.

[0086] Embodiment 2

[0087] This embodiment provides a single-phase grounding fault line selection system based on zero-sequence current modal decomposition, including:

[0088] A data acquisition module, which is used to acquire zero-sequence current and nth harmonic current;

[0089] A zero-sequence current distortion rate calculation module is used to calculate the total harmonic distortion rate of the current according to the zero-sequence current and the nth harmonic current, and determine the maximum value of the zero-sequence current distortion rate;

[0090] A fault judgment module is used to determine that if the maximum value of the zero-sequence current distortion rate is much greater than the minimum value, the outgoing line fails. The zero-sequence transient current signal of each line is decomposed by full noise-assisted aggregated empirical mode decomposition to obtain the IMF component of each line. The IMF component of each line is subjected to linear Gaussian fuzzy information granulation to obtain the membership function of the linear Gaussian fuzzy information granule. The fuzzy entropy is obtained according to the membership function, and the single-phase grounding fault line is determined according to the fuzzy entropy; if the maximum value of the zero-sequence current distortion rate is equal to the minimum value, the bus fails.

[0091] Embodiment 3

[0092] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps in the single-phase grounding fault line selection method based on zero-sequence current modal decomposition as described above are implemented.

[0093] Embodiment 4

[0094] This embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps in the single-phase grounding fault line selection method based on zero-sequence current modal decomposition as described above are implemented.

[0095] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of hardware embodiments, software embodiments, or embodiments combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer-usable program code.

[0096] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0097] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0098] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0099] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A single-phase ground fault line selection method based on zero-sequence current modal decomposition is characterized by: The steps include: Obtain zero-sequence current and nth harmonic current; Calculate the total harmonic distortion rate of current according to zero-sequence current and nth harmonic current, and determine the maximum value of zero-sequence current distortion rate; If the maximum value of the zero-sequence current distortion rate is much greater than the minimum value, the outgoing line fails. The zero-sequence transient current signal of each line is decomposed using full noise-assisted aggregated empirical mode decomposition to obtain the IMF component of each line. The IMF component of each line is subjected to linear Gaussian fuzzy information granulation to obtain the membership function of the linear Gaussian fuzzy information granule. The fuzzy entropy is calculated based on the membership function, and the single-phase grounding fault line is determined based on the fuzzy entropy. If the maximum value of the zero-sequence current distortion rate is equal to the minimum value, the bus fails.

2. The single-phase grounding fault line selection method based on zero-sequence current modal decomposition according to claim 1 is characterized in that: The calculation method of the total harmonic distortion rate of the current is: The effective values ​​of all harmonic currents are squared and summed, and then the square root is taken to obtain the harmonic current content. The harmonic current content is then compared with the effective value of the fundamental current and multiplied by 100% to obtain the total harmonic distortion rate of the current in percentage form.

3. The single-phase grounding fault line selection method based on zero-sequence current modal decomposition according to claim 1 is characterized in that: The method of decomposing the zero-sequence transient current signal of each line by using the full noise assisted aggregated empirical mode decomposition includes: Step 1: Add the positive and negative white noise pairs to the original signal to obtain the first new signal, and perform M EMD decompositions on the first new signal to obtain M first-order IMF components; Step 2: Calculate the mean of M first-order IMF components to obtain the first-order IMF components and the first-order residual; Step 3: Add the positive and negative paired white noise IMF signals obtained by EMD decomposition to the first-order residual to obtain the second new signal, and perform EMD on the second new signal M times to obtain M second-order IMF components, and average them to obtain the second-order IMF components and the second-order residual; Step 4: Repeat steps 1 to 3 until the number of extreme points of the residual component is less than 2, and obtain k IMF components and residual components.

4. The single-phase grounding fault line selection method based on zero-sequence current modal decomposition according to claim 1 is characterized in that: The membership function of the linear Gaussian fuzzy information granule is: Among them, kt+b is called the center line of the LFIG, k, b∈R represent the slope and intercept of the center line; σ is called the discrete degree of the LFIG, T and x represent the data values ​​corresponding to each time point in the total time series and the time series respectively.

5. The single-phase grounding fault line selection method based on zero-sequence current modal decomposition according to claim 1 is characterized in that: The line with the largest fuzzy entropy is taken as the pending fault line.

6. The single-phase grounding fault line selection method based on zero-sequence current modal decomposition according to claim 1 is characterized in that: The method for obtaining zero-sequence current and nth harmonic current is: monitor the voltage and zero-sequence voltage of the bus in real time, judge the relationship between the zero-sequence voltage and the phase voltage, and when the zero-sequence voltage and the phase voltage reach the set relationship, obtain the zero-sequence current and nth harmonic current through the detection device.

7. The single-phase grounding fault line selection method based on zero-sequence current modal decomposition according to claim 1 is characterized in that: If the absolute value of the difference between the maximum and minimum values ​​of the zero-sequence current distortion rate is less than the set threshold and the maximum value of the zero-sequence current distortion rate is not equal to the minimum value, an audible and visual alarm instruction is issued.

8. A single-phase ground fault line selection system based on zero-sequence current modal decomposition is characterized by: include: A data acquisition module, which is used to acquire zero-sequence current and nth harmonic current; A zero-sequence current distortion rate calculation module is used to calculate the total harmonic distortion rate of the current according to the zero-sequence current and the nth harmonic current, and determine the maximum value of the zero-sequence current distortion rate; A fault judgment module is used to determine that if the maximum value of the zero-sequence current distortion rate is much greater than the minimum value, the outgoing line fails. The zero-sequence transient current signal of each line is decomposed by full noise-assisted aggregated empirical mode decomposition to obtain the IMF component of each line. The IMF component of each line is subjected to linear Gaussian fuzzy information granulation to obtain the membership function of the linear Gaussian fuzzy information granule. The fuzzy entropy is obtained according to the membership function, and the single-phase grounding fault line is determined according to the fuzzy entropy; if the maximum value of the zero-sequence current distortion rate is equal to the minimum value, the bus fails.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps in the single-phase grounding fault line selection method based on zero-sequence current modal decomposition as described in any one of claims 1 to 7 are implemented.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps in the single-phase grounding fault line selection method based on zero-sequence current modal decomposition as described in any one of claims 1-7 are implemented.

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