A Comprehensive Judgment Method and System for Distribution Network Fault Type Identification and Fault Line Selection

Abstract

The present invention belongs to the technical field of power detection, and provides a comprehensive judgment method and system for distribution network fault type identification and fault line selection. The method includes obtaining the operation data of a small current grounding system; calculating the zero-sequence voltage based on the system operation data, and judging whether the zero-sequence voltage exceeds the limit. If it exceeds the limit, a fault occurs. Compare the amplitude-frequency characteristic values of each zero-sequence voltage. If the characteristic frequency bands of all lines are the same and the maximum fault characteristic value is negative, the fault occurs on the bus, otherwise the fault occurs on the line. Conduct a comprehensive judgment on the fault type, fault form, and fault line of the line to obtain a comprehensive fault judgment result; cut off the fault according to the fault signal corresponding to the comprehensive fault judgment result, output complete fault information, and better serve the subsequent protection device.

Description

Technical Field

[0001] The present invention belongs to the technical field of power detection, and particularly relates to a comprehensive judgment method and system for identifying distribution network fault types and fault line selection. Background Technique

[0002] The statements in this part only provide background technical information related to the present invention, and do not necessarily constitute prior art.

[0003] Currently, the line selection method based on steady-state components generally applies to metallic or resistive grounding faults. At this time, the steady-state component content of the fault is large and easy to extract. Moreover, in a system grounded through an arc suppression coil, the distribution of the steady-state current may be changed due to over-compensation, resulting in the loss of fault characteristics and the inability to detect the fault. The fault line selection is carried out by using the characteristics that the zero-sequence current of the fault line is opposite in polarity to the zero-sequence current of the non-fault line when a single-phase grounding fault occurs on the line, and the zero-sequence current of the fault line is equal to the sum of the zero-sequence currents of the non-fault lines. This method basically meets the requirements for an ungrounded neutral system, but is not applicable to an arc suppression coil grounded system. Furthermore, the line selection is carried out by using the characteristic that the first half-wave of the transient zero-sequence current of the fault line and the non-fault line is opposite in polarity in the first cycle after a single-phase grounding fault occurs. Since the capacitor is not fully charged in the transient stage after the fault, the transient current value is not affected by the arc suppression coil, so the first half-wave method is applicable to an arc suppression coil grounded system. However, since the fault current is generally capacitive and the generation of the arc is also inevitable, a large amount of harmonics will be generated after the fault, interfering with the detection of the zero-sequence current and increasing the difficulty of line selection. The above methods for fault line selection using zero-sequence current are prone to misjudgment.

[0004] The signal injection method utilizes the fact that the amplitude of the injected signal flowing into the fault line is much larger than that of the injected signals of other non-fault lines. By comparing the amplitudes of the injected signals in each line, the faulty line can be found. However, if the injected signal is too small, it will be interfered by the working signal, and if it is too large, it will interfere with the normal working signal.

[0005] Currently, a large amount of in-depth research has been carried out on fault line selection at home and abroad, and many fault line selection methods have been proposed, such as the zero-sequence current method, the first half-wave method, the correlation analysis method, and the signal injection method, etc. However, these methods all have certain limitations, and many problems have not been well solved.

[0006] Compared with the steady-state component, the transient component during a fault has a relatively short duration but is more obvious when it exists, and it is hardly affected by the arc suppression coil. Among the transient component line selection algorithms, the first half-wave method, the instantaneous power method, the amplitude ratio and phase comparison of transient zero current, the transient energy method, etc. are more commonly used. The first half-wave method and the amplitude ratio and phase comparison of transient zero current use the polarity relationship between the zero-sequence voltage and the zero-sequence current of the faulty line itself during the transient process for line selection. However, the time required to capture the characteristic quantities by such methods is short, and they are affected by the fault resistance and the initial fault angle, so the reliability is not high. The instantaneous power and transient energy methods use the transient zero voltage and zero current to construct a fault component representing energy through integration, analyze the polarity and magnitude on the faulty line and the healthy line to distinguish the fault, and can also achieve line selection for faults around 1KΩ.

[0007] The inventors have found the following technical problems:

[0008] 1) In the current line selection methods for ungrounded neutral systems, there are many line selection methods using steady-state signals or transient signals, but the reliability of judging arc grounding faults has always been low. Especially when an arc grounding fault occurs in a system with an arc suppression coil grounded at the neutral point, the amplitude, phase, attenuation characteristics, etc. of the transient component are all affected by the arc suppression coil and the arc. The fault characteristics and mechanisms are complex, and the duration of the transient signal is relatively short. The analysis of the fault mechanism after introducing the arc is not yet perfect, and it is difficult to select the line.

[0009] 2) Among the types of distribution network faults, in addition to metallic or resistive faults, arc faults also often occur. The transient signals under arc faults are complex. The line selection algorithm needs to ensure the sensitivity of the action to arc faults while ensuring the reliability of the action, and at the same time take into account metallic or resistive faults. In practical applications, due to the strong nonlinearity of the arc and the high complexity of the fault signal in the arc grounding fault line selection algorithm, the circuit theory analysis still needs to be deeply studied to explore the variation law of the system electrical parameters in the transient stage after the arc fault.

[0010] 3) In the current methods for judging the types of distribution network faults, they are greatly interfered by the fault transient signals and are sensitive to the transition resistance. Since arc faults will bring a large number of transient high-frequency components, the sensitivity of fault type judgment is low, the judgment speed is slow, and it is easy to misjudge. Summary of the Invention

[0011] To solve at least one of the technical problems existing in the above-mentioned background art, the present invention provides a comprehensive judgment method for distribution network fault type identification and fault line selection. It proposes a fault line selection method applicable to arc faults in a small current grounding system, making full use of the transient high-frequency harmonics and low-frequency harmonics contained in the fault signals. The proposed method is sensitive, has a fast action speed, and strong anti-interference ability. It also proposes a fault type judgment method for a small current grounding system, using the correlation of line current moduli to accurately and quickly judge the fault type. A comprehensive fault judgment system for fault type judgment and fault line selection in a small current grounding system is established, which can judge the type, occurrence form, and fault line of the fault, output complete fault information, and better serve the subsequent protection devices.

[0012] To achieve the above object, the present invention adopts the following technical solutions:

[0013] The first aspect of the present invention provides a comprehensive judgment method for distribution network fault type identification and fault line selection, including the following steps:

[0014] Obtain the operation data of the small current grounding system;

[0015] Calculate the zero-sequence voltage based on the system operation data, judge whether the zero-sequence voltage exceeds the limit. If it exceeds the limit, a fault occurs. Compare the amplitude-frequency characteristic values of each zero-sequence voltage. If the characteristic frequency bands of all lines are the same and the maximum fault characteristic value is negative, the fault occurs on the bus; otherwise, the fault occurs on the line. Conduct a comprehensive judgment on the fault type, fault form, and fault line of the line to obtain the comprehensive fault judgment result;

[0016] Cut off the fault according to the fault signal corresponding to the comprehensive fault judgment result.

[0017] The second aspect of the present invention provides a comprehensive judgment system for distribution network fault type identification and fault line selection, including:

[0018] An operation data acquisition module for obtaining the operation data of the small current grounding system;

[0019] A fault comprehensive judgment module for calculating the zero-sequence voltage based on the system operation data, judging whether the zero-sequence voltage exceeds the limit. If it exceeds the limit, a fault occurs. Compare the amplitude-frequency characteristic values of each zero-sequence voltage. If the characteristic frequency bands of all lines are the same and the maximum fault characteristic value is negative, the fault occurs on the bus; otherwise, the fault occurs on the line. Use a line fault type judgment module, a fault form judgment module, and a fault line judgment module for comprehensive judgment to obtain the comprehensive fault judgment result;

[0020] A fault cut-off module for cutting off the fault according to the fault signal corresponding to the comprehensive fault judgment result.

[0021] The third aspect of the present invention provides a computer-readable storage medium.

[0022] A computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it realizes the steps in a comprehensive judgment method for identifying the type of distribution network fault and selecting the fault line as described above.

[0023] The fourth aspect of the present invention provides a computer device.

[0024] A computer device includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it realizes the steps in a comprehensive judgment method for identifying the type of distribution network fault and selecting the fault line as described above.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] Regarding the judgment of the fault type and the selection of the fault line for the small current grounding system fault, through the comprehensive fault judgment of the fault type judgment and the fault line selection, the present invention can comprehensively judge the type, occurrence form, and fault line of the fault, output complete fault information, and better serve the subsequent protection device. Compared with other devices with single functions, the fault comprehensive judgment system established by the present invention can complete the judgment of the small current grounding system fault type and the selection of the fault line, with perfect functions, providing strong support for the subsequent protection.

[0027] The present invention makes full use of the transient high-frequency harmonics and low-frequency harmonics contained in the fault signal. The proposed method is sensitive, has a fast action speed, and strong anti-interference ability.

[0028] The present invention proposes a method for judging the fault type of the small current grounding system, which uses the correlation of the line current modulus to accurately and quickly judge the fault type.

[0029] The advantages of the additional aspects of the present invention will be partially given in the following description, partially will become obvious from the following description, or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0031] Figure 1 is the flow chart of the comprehensive judgment of the small current grounding system fault in the embodiment of the present invention;

[0032] Figure 2 is the schematic diagram of the 10kV distribution network fault in the embodiment 1 of the present invention;

[0033] Figure 3 is the zero-sequence voltage of single-phase arc grounding fault and its wavelet decomposition value in the embodiment of the present invention;

[0034] Figure 4 is the zero-sequence voltage of single-phase resistive grounding fault and its wavelet decomposition value in the embodiment of the present invention;

[0035] Figure 5 is the zero-sequence voltage of two-phase grounding fault and its wavelet decomposition value in the embodiment of the present invention;

[0036] Figure 6 is the zero-sequence voltage energy value of each line for 500Ω resistive grounding fault in the embodiment of the present invention;

[0037] Figure 7 is the zero-sequence voltage energy value of each line for arcing grounding fault in the embodiment of the present invention;

[0038] Figure 8 is the zero-sequence voltage energy value of each line for two-phase grounding fault in the embodiment of the present invention;

[0039] Figure 9 is the zero-sequence voltage energy value of each line for two-phase interphase fault in the embodiment of the present invention;

[0040] Figure 10 is the zero-sequence voltage energy value of each line for three-phase interphase fault in the embodiment of the present invention. Detailed implementation manners

[0041] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0042] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0043] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0044] Embodiment 1

[0045] The present invention aims at the fault type judgment and fault line selection of the small current grounding system fault, and establishes a comprehensive fault analysis system for fault type judgment and fault line selection. The focus is on studying the change law of electrical parameters after the metallic, resistive and arc grounding faults occur in the system, constructing the zero-sequence voltage amplitude-frequency characteristic value that characterizes the difference in characteristic frequency bands of different fault types after the small current grounding system fault to judge the type of fault, and constructing the zero-sequence voltage energy value by using the distribution difference of the zero-sequence voltage, and judging the faulty line according to the magnitude of the zero-sequence voltage energy value of each line. The system analyzes the modulus correlation of the line current through the proposed fault form judgment method, and can distinguish single-phase grounding fault, two-phase grounding fault and other fault forms according to the judgment criteria.

[0046] The line selection method included in this system can overcome the influence of complex fault signals caused by arc, detect arc faults and distinguish the fault types, and accurately select the fault line. Compared with other single-function devices, the comprehensive fault analysis system established by the present invention can complete the fault type judgment and fault line selection of the small current grounding system, with complete functions, providing strong support for subsequent protection.

[0047] like Figure 1 As shown, this embodiment provides a method for comprehensive analysis and judgment of distribution network fault type identification and fault line selection, including the following steps:

[0048] Step 1: Obtain the operating data of the small current grounding system;

[0049] As one or more embodiments, in step 1, the operation data includes: bus voltage, line voltage and line current data;

[0050] At the same time, the bus zero-sequence voltage u is calculated om [n] and line zero-sequence voltage u oi [n], where i = 1, 2, 3, ..., k is the line number and n = 1, 2, ..., N is the number of sampling points.

[0051] Step 2: Start the comprehensive fault analysis system and fault recording. Obtain the zero-sequence voltage based on the system operation data, and determine whether the zero-sequence voltage exceeds the limit. If it exceeds the limit, start recording the voltage and current data and execute step 3. If it does not exceed the limit, repeat steps 1 and 2.

[0052] As one or more embodiments, in this embodiment, if the zero-sequence voltage is greater than 5% of the phase voltage, it is out of limit.

[0053] Step 3: Determine whether the fault is a busbar fault. Compare the zero-sequence voltage amplitude-frequency characteristic values ​​of each line. If the characteristic frequency bands of all lines are the same and the maximum fault characteristic value is a negative number, it means that there is no fault on the line, and the fault occurs on the busbar, and the process ends. Otherwise, execute step 4.

[0054] Step 4: Comprehensive Fault Judgment. Conduct a comprehensive judgment on the fault type, fault form, and fault line. The three processes are executed synchronously to obtain the comprehensive fault judgment result.

[0055] As one or more embodiments, Step 4: The comprehensive judgment on the line fault type, fault line, and fault form specifically includes:

[0056] Step 401: Judge the fault type. Calculate the amplitude-frequency characteristic value of the zero-sequence voltage of each line. According to the set threshold S, when |E W | exceeds the threshold, it can be judged that an arc fault occurs in the system; when it is less than the threshold, it can be considered that a resistive grounding fault or a metallic grounding fault occurs in the system.

[0057] In this embodiment, the threshold S is set to 0.05. When |E W | exceeds the threshold, it can be judged that an arc fault occurs in the system; when it is less than the threshold, it can be considered that a resistive grounding fault or a metallic grounding fault occurs in the system.

[0058] Among them, the calculation process of the amplitude-frequency characteristic value of the zero-sequence voltage is as follows:

[0059] Perform three-scale discrete wavelet transform on the zero-sequence voltage of each line using db2 wavelet to obtain the detail coefficients D 1 、D 2 、D 3 of three scales. For each scale, find the maximum value D max of the detail signal at this scale, the sum of amplitudes D sum , and the standard deviation D std of the amplitudes.

[0060] It is considered that the maximum value of the amplitude occupies a higher proportion in the characteristic parameters than the sum of the amplitudes and the standard deviation of the amplitudes. Therefore, the weights L 1 、L 2 、L 3 are respectively 0.4, 0.3, and 0.3, and the weighted line zero-sequence voltage wavelet characteristic value is

[0061] D W =L 1 D max +L 2 D sum +L 3 D std (1)

[0062] Calculate the wavelet characteristic values D W1 、D W2 、D W3 of three scales. For the main frequency distribution of the arc fault, according to the magnitudes of D max in three frequency bands, take K1 ~K 3 Three weighting coefficients are used to characterize the harmonic content of each frequency band. According to the magnitudes of the fault components in the three frequency bands, the weights are taken as 0.1, 0.2, and 0.6 respectively.

[0063] The amplitude-frequency characteristic values of the zero-sequence voltages of each fault are obtained by weighting as follows:

[0064] E W = K 1 D W1 + K 2 D W2 + K 3 D W3 (2)

[0065] Step 402: Determine the fault line. Calculate the zero-sequence voltage energy values of each line. Compare the zero-sequence voltage energy values of each line one by one, and the line with the largest energy value is judged as the fault line.

[0066] The difference between the amplitude-frequency characteristic values of line i and those of other lines is added to obtain the zero-sequence voltage energy value Q of this line i , compare the voltage energy values of each line, and the line with the largest energy value is the fault line:

[0067]

[0068] Step 403: Determine the fault form. Calculate the fault current mode factor and its correlation coefficient. Determine the fault form according to the criterion.

[0069] To eliminate the electromagnetic coupling existing in the three-phase lines and overcome the influence of waveform distortion and sudden interference of transient fault signals;

[0070] The calculation process of the fault current mode factor and its correlation coefficient of the line includes:

[0071] The transient current fault components of the three phases A, B, and C are used to extract the fault transient components I of the three-phase currents from the fault current A 、I B 、I C , and the Clarke transformation is used for 0-mode and α-mode transformation with the phase-mode transformation of the three-phase current fault components as the reference to extract four mode fault components The phase-mode transformation matrix is:

[0072]

[0073] The four mode fault current components The modulus maxima of are M 0 、M αA 、M αB 、M αC, normalize each modulus maximum value:

[0074]

[0075] Four modulus factors ε 0 , ε αA , ε αB , ε αC .

[0076] For the modulus factors ε αA , ε αB , ε αC calculate the Pearson correlation coefficient:

[0077]

[0078] where, x i , y i are the sampling points of the signal, and n is the length of the signal.

[0079] Obtain ρ AB , ρ BC , ρ CA , and define ρ≥0.8 as the line fault correlation threshold P.

[0080] The determination of the corresponding fault form according to the fault current modulus factor and its correlation coefficient of the line specifically includes:

[0081] 1) When ε 0 ≠0,

[0082] ① If two of |ρ AB |, |ρ BC |, |ρ CA | exceed the threshold P and the other one is less than P, it can be judged that a single-phase ground fault has occurred;

[0083] ② If all of |ρ AB |, |ρ BC |, |ρ CA | are greater than 0 but less than the threshold P, it can be judged that a two-phase ground fault has occurred in the system.

[0084] 2) When ε 0 =0,

[0085] ① If two of |ρ AB |, |ρ BC |, |ρ CA | are greater than the threshold P and the other one is less than P, it can be judged that a two-phase interphase fault has occurred in the system;

[0086] ② If all of |ρ AB |, |ρ BC |, |ρ CAIf they are all non-zero and less than the threshold P, it can be determined that a three-phase symmetrical fault has occurred in the system.

[0087] Step 5: Transmit the fault signal. After the fault judgment is completed, all the fault judgment results are merged, and the fault signal is sent out and a command is issued to cut off the fault.

[0088] A 10 kV distribution network simulation model is established in PSCAD / EMTDC as Figure 2 shown. G is the equivalent power source of the system; T is the main transformer with a rated capacity of 100 MVA, Z is the arc suppression coil transformer; S is the arc suppression coil switch; L is the arc suppression coil with adjustable detuning degree, and R is the series resistance of the arc suppression coil. The system model has a total of 5 lines L1 - L5, and the line lengths are 4 km, 6 km, 6 km, 10 km, and 15 km respectively. The main parameters of the lines in the system model are shown in Table 1.

[0089] Table 1 Main parameters of the lines

[0090]

[0091] Among the lines, L1 is a pure cable line, L3 is a pure overhead line, and the remaining lines are mixed cable and overhead line lines. L1 - L4 do not contain branch lines, and L5 has an overhead line branch L5 - 2. Fa to Ff are six different grounding fault points.

[0092] Suppose a fault occurs on line L4 at 0.13 s, and the fault duration is 0.12 s. The zero-sequence voltage of the fault line and its wavelet decomposition values are as Figures 3 - 5 shown, Figure 3 is the zero-sequence voltage and its wavelet decomposition values of a single-phase arc grounding fault, Figure 4 is the zero-sequence voltage and wavelet decomposition values of a single-phase resistive grounding fault, Figure 5 is the zero-sequence voltage and wavelet decomposition values of a two-phase grounding fault.

[0093] The fault line selection results for different fault forms are as Figures 6 - 10 shown, Figure 6 is the zero-sequence voltage energy value of each line for a 500 Ω resistive grounding fault, Figure 7 is the zero-sequence voltage energy value of each line for an arcing grounding fault, Figure 8 is the zero-sequence voltage energy value of each line for a two-phase grounding fault; Figure 9 is the zero-sequence voltage energy value of each line for a two-phase phase-to-phase fault; Figure 10 is the zero-sequence voltage energy value of each line for a three-phase phase-to-phase fault.

[0094] The line selection method included in the present invention can overcome the influence of complex fault signals brought by electric arcs, detect arc faults, distinguish fault types, and accurately select the fault line. Compared with other devices with single functions, the fault comprehensive judgment system established in the present invention can complete the judgment of fault types and the selection of fault lines in a small current grounding system, with perfect functions, providing strong support for subsequent protection.

[0095] Embodiment 2

[0096] This embodiment provides a comprehensive judgment system for distribution network fault type identification and fault line selection, including:

[0097] An operating data acquisition module for acquiring the operating data of a small current grounding system;

[0098] A fault comprehensive judgment module for calculating the zero-sequence voltage based on the system operating data, judging whether the zero-sequence voltage exceeds the limit. If it exceeds the limit, a fault occurs. Compare the amplitude-frequency characteristic values of each zero-sequence voltage. If the characteristic frequency bands of all lines are the same and the maximum fault characteristic value is negative, the fault occurs on the bus, otherwise the fault occurs on the line. Use a line fault type judgment module, a fault form judgment module, and a fault line judgment module for comprehensive judgment to obtain the fault comprehensive judgment result;

[0099] A fault removal module for removing the fault according to the fault signal corresponding to the fault comprehensive judgment result.

[0100] Among them, using a line fault type judgment module, a fault form judgment module, and a fault line judgment module for comprehensive judgment includes:

[0101] The fault type judgment module is used to compare the amplitude-frequency characteristic values of the zero-sequence voltage of each line with a set threshold. If it exceeds the threshold, it is determined that an arc fault occurs in the system, otherwise a resistance grounding fault or a metallic grounding fault occurs in the system;

[0102] The fault form judgment module is used to judge the corresponding fault form according to the fault current modulus factor of the line and its correlation coefficient;

[0103] The fault line judgment module is used to compare the zero-sequence voltage energy values of each line one by one according to the zero-sequence voltage energy values of each line, and determine the line with the largest energy value as the fault line.

[0104] Embodiment 3

[0105] This embodiment provides a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, it implements the steps in a comprehensive judgment method for distribution network fault type identification and fault line selection as described above.

[0106] Embodiment 4

[0107] This embodiment provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps in a method for comprehensive judgment of power distribution network fault type identification and fault line selection as described above are implemented.

[0108] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of an embodiment implemented in hardware, a software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories and optical memories, etc.) containing computer-usable program code.

[0109] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or combinations of blocks.

[0110] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device implements the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or combinations of blocks.

[0111] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks or combinations of blocks.

[0112] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above methods. Among them, the storage medium can be a magnetic disk, an optical disc, a read-only memory (ROM), or a random access memory (RAM), etc.

[0113] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A comprehensive judgment method for identifying distribution network fault types and fault line selection, characterized in that, it includes the following steps: Obtain the operation data of the small current grounding system; Calculate the zero-sequence voltage based on the system operation data, and judge whether the zero-sequence voltage exceeds the limit. If it exceeds the limit, a fault occurs. Compare the amplitude-frequency characteristic values of each zero-sequence voltage. If the characteristic frequency bands of all lines are the same and the maximum fault characteristic value is negative, the fault occurs on the bus. Otherwise, the fault occurs on the line. Conduct a comprehensive judgment on the fault type, fault form, and fault line of the line to obtain the comprehensive fault judgment result; Cut off the fault according to the fault signal corresponding to the comprehensive fault judgment result; The calculation process of the amplitude-frequency characteristic value of the zero-sequence voltage is as follows: Perform three-scale discrete wavelet transform on the zero-sequence voltage of each line to obtain the detail coefficients of three scales. Based on each scale, calculate the maximum value, the sum of amplitudes, and the standard deviation of the amplitudes of the detail signals of this scale; Calculate the wavelet characteristic values of three scales respectively according to the maximum value, the sum of amplitudes, and the standard deviation of the amplitudes of the detail signals of each scale. According to the maximum values of the detail signals in three frequency bands, take three weight coefficients to characterize the harmonic content of each frequency band, and obtain the amplitude-frequency characteristic value of each fault zero-sequence voltage by weighting according to the magnitudes of the fault components in three frequency bands; Judge the fault line: Calculate the zero-sequence voltage energy value of each line; Compare the zero-sequence voltage energy values line by line, and the line with the largest energy value is judged as the fault line; The zero-sequence voltage energy value of each line is obtained by adding the differences between the amplitude-frequency characteristic values of each line itself and other lines.

2. The comprehensive judgment method for identifying distribution network fault types and fault line selection according to claim 1, characterized in that, The comprehensive judgment of the fault type, fault line, and fault form of the line specifically includes: Compare the amplitude-frequency characteristic values of the zero-sequence voltage of each line with the set threshold. If it exceeds the threshold, it is determined that an arc fault occurs in the system. Otherwise, a resistive grounding fault or a metallic grounding fault occurs in the system; According to the zero-sequence voltage energy value of each line, compare the zero-sequence voltage energy values line by line, and the line with the largest energy value is determined as the fault line; Judge the corresponding fault form according to the fault current modulus factor of the line and its correlation coefficient.

3. The comprehensive judgment method for identifying distribution network fault types and fault line selection according to claim 2, characterized in that, The calculation process of the fault current modulus factor of the line and its correlation coefficient includes: Extract the transient fault components of the three-phase currents from the fault current using the transient current fault components of phases A, B, and C respectively and and . Perform phase-mode transformation on the three-phase current fault components and use transformation to perform 0-mode and mode transformation to extract four mode fault components Normalize the modulus maxima of the four mode fault components to obtain the corresponding mode factors and and and ; Obtain the modulo factor and and to obtain the Pearson correlation coefficients of and and .

4. The comprehensive judgment method for identifying distribution network fault types and fault line selection according to claim 3, characterized in that, The specific method for judging the corresponding fault form according to the fault current modulus factor of the line and its correlation coefficient includes: When : If and and two items exceed the threshold , and the remaining one is less than , it is determined that there is a single-phase grounding fault in the system; If and and are all greater than 0 but less than the threshold value , it is determined that a two-phase grounding fault has occurred in the system; When : If , , two items are greater than the threshold , and the remaining one is less than , it is determined that a two-phase interphase fault has occurred in the system; If , , are all not equal to 0 and less than the threshold , it is determined that a three-phase symmetrical fault has occurred in the system.

5. A comprehensive judgment system for identifying distribution network fault types and fault line selection, characterized in that, it includes: An operation data acquisition module for acquiring the operation data of the small current grounding system; A fault comprehensive judgment module is used to calculate the zero-sequence voltage based on the system operation data, determine whether the zero-sequence voltage exceeds the limit. If it exceeds the limit, a fault occurs. Compare the amplitude-frequency characteristic values of each zero-sequence voltage. If the characteristic frequency bands of all lines are the same and the maximum fault characteristic value is negative, the fault occurs on the bus; otherwise, the fault occurs on the line. The line fault type judgment module, fault form judgment module, and fault line judgment module are used for comprehensive judgment to obtain the fault comprehensive judgment result; A fault removal module is used to remove the fault according to the fault signal corresponding to the fault comprehensive judgment result; The calculation process of the amplitude-frequency characteristic value of the zero-sequence voltage is as follows: Perform three-scale discrete wavelet transform on the zero-sequence voltage of each line to obtain the detail coefficients of three scales, and calculate the maximum value, sum of amplitudes, and standard deviation of the amplitude of the detail signal of this scale based on each scale; Calculate the wavelet characteristic values of three scales respectively according to the maximum value, sum of amplitudes, and standard deviation of the detail signal of each scale. According to the maximum value of the detail signal in three frequency bands, take three weight coefficients to characterize the harmonic content of each frequency band, and obtain the amplitude-frequency characteristic value of each fault zero-sequence voltage by weighting according to the size of the fault components in three frequency bands; Judge the fault line: Calculate the zero-sequence voltage energy value of each line; Compare the zero-sequence voltage energy values of each line one by one, and the line with the largest energy value is judged as the fault line; The zero-sequence voltage energy value of each line is obtained by adding the differences between the amplitude-frequency characteristic values of each line itself and other lines.

6. A comprehensive judgment system for distribution network fault type identification and fault line selection as described in claim 5, characterized in that, characterized in that, The comprehensive judgment using the line fault type judgment module, fault form judgment module, and fault line judgment module includes: The fault type judgment module is used to compare the amplitude-frequency characteristic value of the zero-sequence voltage of each line with a set threshold. If it exceeds the threshold, it is determined that an arc fault occurs in the system; otherwise, a resistive grounding fault or a metallic grounding fault occurs in the system; The fault form judgment module is used to judge the corresponding fault form according to the fault current modulus factor of the line and its correlation coefficient; The fault line judgment module is used to compare the zero-sequence voltage energy values of each line one by one according to the zero-sequence voltage energy value of each line, and determine the line with the largest energy value as the fault line.

7. A computer-readable storage medium, on which a computer program is stored, characterized in that, When the program is executed by a processor, it implements the steps in a comprehensive judgment method for distribution network fault type identification and fault line selection as described in any one of claims 1-4.

8. A computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in a comprehensive judgment method for distribution network fault type identification and fault line selection as described in any one of claims 1-4.

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