A coal mine power grid mine cable high-resistance grounding fault line selection method and system

Abstract

The present application belongs to the field of power system relay protection, and provides a coal mine power grid mine cable high resistance grounding fault line selection method and system, based on the zero sequence current of each line before and after the fault, the zero sequence current vector of each line before and after the fault is calculated; according to the difference of the zero sequence current vector of each line before and after the fault, the zero sequence current variation of each line before and after the fault is determined; based on the zero sequence current variation of each line before and after the fault, signal detection is carried out by using the oscillator chaotic system, and the output phase diagram of different lines is obtained; according to the state of the output phase diagram of different lines, the fault line selection is carried out, and the fault line is determined. The present application uses the principle that the phase and amplitude of the zero sequence current variation of the fault line are different from those of the non-fault line, and the zero sequence current variation of the non-fault line is the same, to determine the fault line, and under the condition of three-phase load imbalance, the fault line can still be determined, thereby improving the accuracy and universality of high resistance grounding fault line selection.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power system relay protection, and particularly relates to a coal mine power grid mine cable high-resistance grounding fault line selection method and system. BACKGROUND

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

[0003] The coal mine 10kV and 6kV power grid generally adopts a non-effective grounding system mode of neutral point grounding or neutral point grounding through an arc suppression coil. When a cable occurs a high-resistance grounding fault in this grounding system mode, the zero sequence current is small, the fault characteristics are not obvious, and the interference is large, so it is difficult to accurately identify the fault line. The existing line selection methods rarely consider the influence of three-phase imbalance and different fault cable parameters, thereby leading to line selection misjudgment. Therefore, how to realize fault line selection has been a research hotspot in the electrical field.

[0004] At present, domestic and foreign scholars have done a lot of research work and proposed a variety of fault line selection methods. Among them, the fault line selection methods of non-effective grounding system mainly analyze from two aspects of steady-state characteristics and transient characteristics. Some methods adopt zero sequence current amplitude comparison method to compare the amplitudes of each line, wherein the line with the largest amplitude is the fault line. Some methods adopt zero sequence current group amplitude and phase comparison method to select three lines with the largest amplitudes, then compare the phases of the three lines, and then select the fault line. In addition, in the existing technology, in the flexible grounding system, the zero sequence measurement impedance of each line is compared to realize the line selection of high-resistance grounding fault. Some methods perform EMD decomposition on the steady-state current signal, then take the five times harmonic of each current of the line as input, input into the Duffing oscillator system for line selection judgment. In addition, in some research methods, discrete wavelet transform is used to extract the characteristics of the zero sequence current, the signals of each frequency band are normalized and taken as characteristic quantities, pso-svm is taken as a fault diagnosis model for training to realize fault diagnosis. In some research methods, the fault positioning principle of transient component is used to collect the components of the zero sequence network, and accurate positioning is realized through grouping comparison method. In some research methods, a current waveform similarity comparison traveling wave method is proposed, which fully utilizes the transient traveling wave information to calculate the comprehensive similarity coefficient of the traveling wave between lines. In the above methods, the steady-state characteristics such as zero sequence voltage, zero sequence current, three-phase voltage and other state quantities are more stable, and the signal quantity characteristics are easier to extract, so that the fault line selection is more convenient to realize.

[0005] However, the above research methods still have the following problems: First, line faults are diverse, including metallic grounding and high-resistance grounding. Different fault types have different fault characteristics. Furthermore, considering the impact of three-phase load imbalance and different parameters of different cable types on the criteria, the universality of single-fault line selection methods is weak. Second, the criterion of comparing the phase and amplitude changes of zero-sequence current, although simple in principle and easy to implement, requires high identification accuracy and is easily affected by factors such as unbalanced current, system operating mode, and noise, leading to misjudgments. Third, while the method of using steady-state zero-sequence current correlation quantities as the basis for line selection has some application in practical engineering, research through formula derivation and practical application shows that when a high-resistance grounding fault occurs in a coal mine system, regardless of the characteristic used, the steady-state zero-sequence current characteristic is a tiny signal, making it difficult to use in practical engineering. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a method and system for selecting high-resistance grounding faults in mining cables used in coal mine power grids. This invention utilizes the amplitude and phase of the zero-sequence current change before and after a line fault as criteria, enabling accurate identification of faulty and non-faulty lines under conditions of unbalanced three-phase loads and the influence of different cable parameters.

[0007] According to some embodiments, the first aspect of the present invention provides a method for locating high-resistance grounding faults in mining cables of coal mine power grids, employing the following technical solution:

[0008] A method for locating high-resistance grounding faults in mining cables of coal mine power grids, comprising:

[0009] Calculate the zero-sequence current vector of each line before and after the fault based on the zero-sequence current of each line before and after the fault.

[0010] The change in zero-sequence current of each line before and after the fault is determined by the difference between the zero-sequence current vectors of each line before and after the fault.

[0011] Based on the changes in zero-sequence current of each line before and after the fault, the output phase diagram of different lines is obtained by using the oscillator chaotic system for signal detection.

[0012] Based on the status of the output phase diagram of different lines, fault line selection is performed to determine the faulty line.

[0013] Furthermore, determining the change in zero-sequence current of each line before and after the fault based on the difference in zero-sequence current vectors before and after the fault specifically involves:

[0014]

[0015] In the formula, This represents the zero-sequence current vector after the fault in the nth cycle. a zero sequence current vector of the nth cycle, two cycles before the nth cycle, and before the fault, a zero sequence current variation of each line before and after the fault.

[0016] Further, the zero sequence current variation of each line before and after the fault is used to perform signal detection by using a dipole chaotic system to obtain an output phase diagram of different lines, specifically:

[0017] When the driving coefficient of the external driving force is greater than the critical value of the chaotic state, the zero sequence current variation of each line before and after the fault is detected by using a dipole chaotic system;

[0018] to obtain an output phase diagram of different lines.

[0019] Further, the state of the output phase diagram of different lines is used to perform fault line selection to determine a fault line, specifically:

[0020] obtaining an output phase diagram of different lines;

[0021] When the state of the output phase diagram of a certain line is different from the state of the output phase diagram of all other lines, and the state of the output phase diagram of all other lines is the same, it is determined that the certain line is a fault line and all other lines are non-fault lines.

[0022] Further, the state of the output phase diagram of different lines includes two cases, specifically:

[0023] One case is that the output phase diagram of the fault line is in a periodic state, and the output phase diagram of the non-fault line is in a chaotic state;

[0024] The other case is that the output phase diagram of the fault line is in a chaotic state, and the output phase diagram of the non-fault line is in a periodic state.

[0025] Further, based on the zero sequence current of each line before and after the fault, a fast Fourier transform is used to calculate the zero sequence current vector of each line before and after the fault.

[0026] According to some embodiments, the second aspect of the present application provides a coal mine power grid mine cable high-resistance grounding fault line selection system, which adopts the following technical scheme:

[0027] A coal mine power grid mine cable high-resistance grounding fault line selection system, comprising:

[0028] A zero sequence current vector calculation module configured to calculate the zero sequence current vector of each line before and after the fault based on the zero sequence current of each line before and after the fault;

[0029] A zero sequence current variation determination module configured to determine the zero sequence current variation of each line before and after the fault according to the difference between the zero sequence current vectors of each line before and after the fault;

[0030] The zero sequence current variation signal detection module is configured to utilize the vibrator chaotic system to perform signal detection based on the zero sequence current variation of each line before and after the fault, and obtain the output phase diagram of different lines.

[0031] The fault line selection module is configured to perform fault line selection according to the state of the output phase diagram of different lines, and determine the fault line.

[0032] According to some embodiments, the third aspect of the present application provides a computer readable storage medium.

[0033] A computer readable storage medium, having stored thereon a computer program, which, when executed by a processor, implements the steps of the coal mine power grid mine cable high resistance grounding fault line selection method according to the first aspect.

[0034] According to some embodiments, the fourth aspect of the present application provides a computer device.

[0035] A computer device, comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of the coal mine power grid mine cable high resistance grounding fault line selection method according to the first aspect when executing the program.

[0036] According to some embodiments, the fifth aspect of the present application provides a computer program product or a computer program.

[0037] The present application provides a computer program product or a computer program, which comprises computer instructions stored in a computer readable storage medium. The processor of the computer device reads the computer instructions from the computer readable storage medium, and the processor executes the computer instructions to make the computer device execute the steps of the coal mine power grid mine cable high resistance grounding fault line selection method according to the first aspect.

[0038] Compared with the prior art, the present application has the following beneficial effects:

[0039] The present application proposes a fault line selection criterion based on a steady-state impedance analysis method. Before and after the fault, the phase of the zero sequence current variation of the fault line is different from that of the non-fault line. In the impedance equivalent model of the coal mine distribution network, under the neutral point grounding and neutral point grounding through arc suppression coil, when a high resistance grounding fault occurs, according to the steady-state impedance characteristics and zero sequence current characteristics, the phase and amplitude of the zero sequence current variation of the fault line before and after the fault are different from those of the non-fault line, which is used as a line selection criterion, and correct line selection can be realized in the non-effective grounding system.

[0040] The Holmes-Duffing oscillator chaotic system small signal detection method is proposed, when the high resistance grounding fault occurs in the non-effective grounding system of the coal mine power grid, the zero sequence current variation is a small signal between several hundred microamperes and several milliamperes, which is difficult to detect in actual engineering. The zero sequence current variation signal of the fault line is extracted, which is used as the input of the Holmes-Duffing oscillator system, the small signal fault characteristics are extracted by using the high sensitivity of the oscillator system to the specific small signal. Then, according to the chaos principle of the Holmes-Duffing oscillator system, the phase trajectory of different lines is generated, the relationship between the system chaotic period state and the outer driving force is analyzed, and the output phase diagram state is compared, so that the high resistance grounding fault of the coal mine power grid non-effective grounding system can be accurately selected. BRIEF DESCRIPTION OF DRAWINGS

[0041] The drawings accompanying the specification of this application form a part thereof, serve to further provide a further understanding of the application, and together with the description of the exemplary embodiments of the application, explain the application, and do not constitute an improper limitation of the application.

[0042] Figure 1 It is a coal mine power grid mine cable high resistance grounding fault line selection method flow chart in the embodiment of the application;

[0043] Figure 2 It is a coal mine power grid equivalent model in the embodiment of the application;

[0044] Figure 3 It is a zero sequence network of the coal mine power grid in the embodiment of the application;

[0045] Figure 4 It is a simplified diagram of the zero sequence network in the embodiment of the application;

[0046] Figure 5 It is an equivalent operation circuit of the fault line in the embodiment of the application;

[0047] Figure 6 It is a zero sequence equivalent circuit of the single-phase grounding fault line in the embodiment of the application;

[0048] Figure 7 It is an arc suppression coil grounding equivalent model in the embodiment of the application;

[0049] Figure 8 It is an arc suppression coil grounding zero sequence equivalent model in the embodiment of the application;

[0050] Figure 9 It is a line equivalent circuit connected with a three-phase unbalanced load in the embodiment of the application;

[0051] Figure 10 It is a cable parameter simulation model in the embodiment of the application;

[0052] Figure 11 is the Holmes-Duffing oscillator system output phase diagram when the neutral point is not grounded in the embodiment of the present application;

[0053] Figure 12 is the Holmes-Duffing oscillator system output phase diagram when the neutral point is grounded through an arc-extinguishing coil in the embodiment of the present application;

[0054] Figure 13 is the Holmes-Duffing oscillator system output phase diagram when the neutral point is not grounded and the load is unbalanced in the embodiment of the present application;

[0055] Figure 14 is the Holmes-Duffing oscillator system output phase diagram when the neutral point is grounded through an arc-extinguishing coil and the load is unbalanced in the embodiment of the present application;

[0056] Figure 15 is the Holmes-Duffing oscillator system output phase diagram when the longest line is faulted and the neutral point is not grounded in the embodiment of the present application;

[0057] Figure 16 is the Holmes-Duffing oscillator system output phase diagram when the longest line is faulted and the neutral point is grounded through an arc-extinguishing coil in the embodiment of the present application. DETAILED DESCRIPTION

[0058] The present application will be further described with reference to the drawings and embodiments.

[0059] It should be noted that the following detailed description is merely exemplary and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0060] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, devices, components and / or combinations thereof, but do not preclude the presence or addition of one or more other features, steps, operations, devices, components and / or combinations thereof.

[0061] The embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0062] Embodiment One

[0063] This embodiment provides a method for selecting the fault location of high-resistance grounding cables in coal mine power grids. This embodiment uses the application of this method to a server as an example for illustration. It is understood that this method can also be applied to terminals, and can also be applied to systems including terminals, servers, and other components, and can be implemented through interaction between the terminal and the server. The server can be an independent physical server, a server cluster composed of multiple physical servers, or a distributed system. It can also be a cloud server providing basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network servers, cloud communication, middleware services, domain name services, CDN security services, and big data and artificial intelligence platforms. The terminal can be a smartphone, tablet, laptop, desktop computer, smart speaker, smartwatch, etc., but is not limited to these. The terminal and server can be directly or indirectly connected via wired or wireless communication, which is not limited herein. In this embodiment, the method includes the following steps:

[0064] Calculate the zero-sequence current vector of each line before and after the fault based on the zero-sequence current of each line before and after the fault.

[0065] The change in zero-sequence current of each line before and after the fault is determined by the difference between the zero-sequence current vectors of each line before and after the fault.

[0066] Based on the changes in zero-sequence current of each line before and after the fault, the output phase diagram of different lines is obtained by using the oscillator chaotic system for signal detection.

[0067] Based on the status of the output phase diagram of different lines, fault line selection is performed to determine the faulty line.

[0068] like Figure 1 As shown, the method described in this embodiment specifically includes:

[0069] Step 1: Collect the zero-sequence current of each line;

[0070] Step 2: Calculate the zero-sequence current vector of each line using FFT, and calculate the change in zero-sequence current of each line, as shown in formula (9);

[0071] The method of determining the change in zero-sequence current of each line before and after the fault based on the difference in zero-sequence current vectors before and after the fault is as follows:

[0072]

[0073] In the formula, This represents the zero-sequence current vector after the fault in the nth cycle. This represents the zero-sequence current vector prior to the fault in the two cycles preceding the nth cycle. This represents the change in zero-sequence current of each line before and after the fault.

[0074] Step three: obtain the zero sequence current variation of each line, and take it as the input of the Holmes-Duffing oscillator system;

[0075] Step four: perform the Holmes-Duffing oscillator system algorithm operation to obtain the output phase diagram;

[0076] Step five: judge the state of the obtained output phase diagram, and the lines with the same output phase diagram state are healthy lines, and the lines with different output phase diagram states are fault lines.

[0077] First, based on the high resistance grounding fault line selection criterion of the steady-state impedance analysis method, in the coal mine distribution network, a high-voltage main power supply line is generally provided to transmit power from the substation to the main equipment and area in the mine. The incoming line of the coal mine substation generally uses an incoming line of 110kV, which is converted to 6kV or 10kV by a main transformer. The 6kV and 10kV power supply system has multiple power supply areas, which are drawn from the main power supply area to provide power for each working face, hoist, ventilation equipment, etc., forming a three-level power supply network. The neutral point grounding method at the 10kV side of the transformer in the coal mine 110 / 10kv substation generally adopts the non-effective grounding method, i.e. the neutral point grounding method and the neutral point grounding method through arc suppression coil. The circuit analysis of the two methods is as follows.

[0078] First, the steady-state impedance analysis of high resistance grounding fault in neutral point grounding system:

[0079] In the steady-state fault characteristic research of single-phase grounding fault, the admittance of the line has little effect on the system, and the resistance and inductance of the line are much smaller than the capacitive reactance of the circuit. Therefore, when drawing the equivalent circuit diagram, the resistance and inductance of the line can be ignored. According to the actual 10kV power grid structure of the coal mine, the equivalent model of the coal mine distribution network as shown in Figure 2 is established. The neutral point adopts the non-grounding method. For the convenience of circuit analysis, the model considers single busbar and four outgoing line branches. Single-phase grounding, two-phase short-circuit, single-phase open-circuit fault and other asymmetric short-circuit faults occur in the system. When the power system is subjected to asymmetric fault, the three-phase impedance is not the same, the effective values of three-phase voltage and current are not equal, and the phase difference between phases is also not equal. Therefore, when analyzing, the three-phase situation must be considered. Therefore, this embodiment uses the symmetrical component method to analyze the system fault problem.

[0080] Four cables are in normal operation. It is assumed that a single-phase high resistance grounding fault occurs in the second cable, and the system will generate a zero sequence current. The equivalent zero sequence network diagram is as follows Figure 3As shown. When the second line fails, the zero-sequence network is equivalent to adding a voltage source of equal magnitude and direction to the zero-sequence voltage at the fault point, which can be represented by a voltage source U0. For coal mine power grids, the longest cable power supply line generally does not exceed 3km. In short-distance cables, the impact of using π-type equivalent circuits and T-type equivalent circuits on the steady-state analysis results is negligible. In this embodiment, the zero-sequence network uses a T-type equivalent circuit. (Figure Z) L1 Z L2 Z L3 Z L4 Z1, Z3, and Z4 represent the zero-sequence impedances of four cable lines, respectively, and the insulation impedances of the first, third, and fourth lines. The ends of these lines are connected to the load. (See diagram.) The zero-sequence currents of the four lines are given.

[0081] Figure 3 The insulation resistance of a medium-sized cable is the sum of the insulation resistances of its three phases, where the insulation resistance is the parallel combination of the insulation resistance and the distributed capacitance. Moreover, the cable insulation impedance is much greater than the zero-sequence impedance of the line, i.e., Z n >>Z Ln Therefore, it is possible to Figure 3 To simplify, ignoring the zero-sequence impedance of the line while representing the insulation impedance, the simplified zero-sequence network diagram is as follows: Figure 4 As shown.

[0082] The relationship between zero-sequence current and zero-sequence voltage for non-faulty phase lines is as follows:

[0083]

[0084] In the formula This refers to the zero-sequence current of non-faulty lines;

[0085] For a faulty line, the relationship between zero-sequence current and zero-sequence voltage in equation (1) no longer holds. Therefore, this embodiment analyzes lines experiencing single-phase ground faults and studies the relationship between zero-sequence current and zero-sequence voltage in the faulty line. Establishment as follows... Figure 5 The zero-sequence network equivalent circuit of the faulty line is shown. Assuming a ground fault occurs in phase A, different types of ground faults, such as metallic grounding and high-resistance grounding, are special cases. Different types of faults can be addressed by setting a grounding resistance. Therefore, this grounding impedance R can be used to... d To simulate a single-phase ground fault, when R d When the resistance is very high, it indicates a single-phase high-resistance ground fault. (See diagram) R is the phase voltage of a three-phase power supply. a R b R c C is the insulation resistance of the three phases to ground. a Cb , C c is the three-phase-to-ground distributed capacitance, R d is the equivalent resistance value of the ground fault line, according to the three-phase characteristics of the line, the three-phase insulation impedance and the three-phase distributed capacitance of the cable are equal, that is, R a = R b = R c , C a = C b = C c .

[0086] According to Kirchhoff's current law, the zero sequence current of the fault line is:

[0087]

[0088] wherein According to symmetry, Z a = Z b = Z c , for the convenience of calculation and simplification, let Z a = Z b = Z c = Z; and the sum of the three-phase voltages is always zero, that is, Bring the above conditions into equation (2) to simplify:

[0089]

[0090] According to equation (3), the zero sequence voltage is generated by the ground impedance R d , the insulation impedance Z a , and the phase voltage of the fault phase V , according to the formula, the internal zero sequence voltage of Figure 4 can be equivalent to a new zero sequence network equivalent circuit as shown in Figure 6

[0091] Using Kirchhoff's current law, we can get:

[0092]

[0093] Using Ohm's law to express each current in equation (4) with voltage and impedance, we can simplify the relationship between the system zero sequence voltage and the phase voltage during fault as follows:

[0094]

[0095] wherein C Σ = C1+C3+C4+3C a , θ = arctan(jωC Σ R Σ ​And θ ranges from 0° to 90°. Therefore, the phase voltage of the faulted phase leads the zero-sequence voltage by 90° to 180°. Based on the analysis of the zero-sequence current, when no single-phase ground fault occurs in the system, there is no grounding resistance, i.e., R. d =0, and by substituting this condition into equation (2), we can obtain the zero-sequence current of the system before the fault occurs as: The zero-sequence voltage of the system after the fault is given by equation (3). The difference between the zero-sequence current of the system after the fault and before the fault can be obtained as shown in equation (6):

[0096]

[0097] In equation (6) These are the zero-sequence voltages before and after the fault, respectively. Therefore, the zero-sequence voltage change can be ignored, and equation (6) can be simplified as follows:

[0098]

[0099] In the formula, This is the voltage to ground of phase A, which is the faulty phase.

[0100] Similarly, the zero-sequence current difference before and after the fault in a non-faulty line is:

[0101]

[0102] In practical engineering, since the timing of a fault cannot be predicted, the vector of the zero-sequence current can be collected in real time. The change in the zero-sequence current can be obtained by the difference between the zero-sequence current vectors collected at two different times, as shown in equation (9):

[0103]

[0104] In the formula Let be the zero-sequence current vector of the nth period. Let be the zero-sequence current vector of the two periods preceding the nth period. This represents the change in zero-sequence current in actual engineering projects.

[0105] The second type is the steady-state impedance analysis of a high-resistance grounding fault in a neutral-point grounding system via an arc-suppression coil:

[0106] In actual coal mine, part of the power grid adopts neutral point through arc suppression coil grounding system, this grounding mode can eliminate the arc generated by single-phase grounding fault, limit the impact current when fault occurs, thereby improving the reliability and stability of the system. However, because of the compensation effect of arc suppression coil, the traditional grounding fault line selection method or high resistance grounding cannot accurately judge the fault line. Therefore, the circuit analysis of the neutral point through arc suppression coil grounding system is carried out, and the over compensation mode is mainly used in the neutral point through arc suppression coil grounding compensation in the coal mine distribution network, and the arc suppression coil grounding model is as shown in Figure 7

[0107] The equivalent operation circuit of the fault is as shown in Figure 5 The zero sequence equivalent network of the arc suppression coil grounding system when fault occurs is as shown in Figure 8

[0108] The relationship analysis between the zero sequence voltage and the phase voltage in the neutral point through arc suppression coil grounding fault model can obtain formula (10) relationship as follows:

[0109]

[0110] In the formula, L is the inductance size of the grounding arc suppression coil, And in the arc suppression coil grounding system, the over compensation mode is used, and the formula expression is This leads to the range of θ∈(-90°-0), compared with the ungrounded system, the zero sequence voltage is ahead of the phase voltage of the fault phase (90°-180°) in phase.

[0111] By comparing formula (5) and formula (10), it can be seen that the change of total insulation parameter of the system is related to the neutral point grounding mode of the system. The neutral grounding mode will affect the zero sequence voltage of the system, but will not affect the relationship between the zero sequence signal of the cable and the insulation parameter.

[0112] By comparing formula (7) and formula (8), it can be analyzed that:

[0113] 1. The phase and amplitude of the zero sequence current change of the fault line are different from those of the non-fault line, and the zero sequence current change of the non-fault line is the same;

[0114] 2. The phase of the zero sequence current change of the fault line is the same as the phase of the fault phase voltage. In this embodiment, the difference between the zero sequence current change of the fault line and that of the non-fault line is used as the basis for fault line selection, that is, by comparing the phase and amplitude relationship of the zero sequence current change of the four lines, the fault line can be identified, the fault diagnosis of the cable is realized, and the efficiency and accuracy of fault handling are improved.

[0115] ​​It is found through simulation that in actual engineering applications, the line zero-sequence current variation is microampere level, especially in coal mine environment, the zero-sequence current variation as a small signal is extremely susceptible to interference. In actual engineering applications, small signals are difficult to be effectively identified, and the system may be misjudged due to noise or interference. Therefore, the embodiment proposes a non-effective grounding system mine-used cable insulation high-resistance grounding fault line selection identification method fusing steady-state impedance analysis and Holmes-Duffing oscillator small signal detection.

[0116] Firstly, the zero-sequence current variation is excavated as a grounding fault criterion feature through steady-state impedance analysis, and then the criterion is taken as the input of the Holmes-Duffing oscillator system to identify the feature of the criterion. The Holmes-Duffing oscillator system has the ability to process disturbance and has high sensitivity to small signals, and it can well solve the problem that the zero-sequence current variation is too small before and after the fault.

[0117] Secondly, adaptive analysis of high-resistance grounding fault line selection criterion based on SSIA

[0118] The first one is a high-resistance grounding fault line selection criterion considering three-phase load imbalance, specifically:

[0119] In actual coal mine distribution network, the end of the distribution network system will be connected with the load to supply power for the load, and when different single-phase loads are connected, due to the different parameters of the loads, there will be three-phase load imbalance. In order to verify the applicability of the fault line selection strategy proposed in the embodiment in actual situation, the influence of three-phase load imbalance on the strategy is mainly discussed.

[0120] Taking a single-phase high-resistance grounding fault as an example, the load adopts Y-type connection, and the equivalent line of the system is as shown in Figure 9 The figure shows that R a , R b , R c are the sizes of three-phase loads, and when three-phase loads are unbalanced, the current flowing into the load will be asymmetric, but according to Kirchhoff's current law, the line current flowing into the load still satisfies

[0121] When a single-phase high-resistance grounding fault occurs in the system and three-phase loads are unbalanced, the zero-sequence current formula (11) is obtained according to Kirchhoff's current law:

[0122]

[0123] In the formula, I is the line current flowing into the load.

[0124] By comparing formula (10) with formula (2), it is found that the expression of zero sequence current is the same in both cases, and thus it is concluded that even if three-phase imbalance occurs at the load end, the change in zero sequence current before and after the fault of each line of the system will not affect the relationship between the insulation parameters and the zero sequence component of the line when the fault occurs. Analysis shows that the criterion proposed in this embodiment will not be affected when the system has three-phase load imbalance. In the case of three-phase imbalance, high-resistance ground fault line selection can still be performed.

[0125] Second, the high-resistance ground fault line selection criterion considering the influence of different cable parameters is as follows:

[0126] In actual coal mines, there are various lines, and different cables are used in different situations, with various cable models, different line impedances, lengths, and distributed capacitance parameters. When faults occur in different types and lengths of cables, they may also affect the criterion proposed in this embodiment, so this section mainly discusses the influence of faults in different lines on the strategy.

[0127] The above analyzes the analysis of each zero sequence component of the system when line 2 fails as an example. When faults occur in other lines, the analysis method is the same as the above analysis method, and different line faults will not have any impact in terms of theoretical analysis, so the criterion proposed in this embodiment is also valid.

[0128] Finally, high-resistance ground fault recognition method based on Holmes-Duffing oscillator system

[0129] The method is based on the change in zero sequence current of each line before and after the fault, and uses the oscillator chaotic system for signal detection to obtain the output phase diagram of different lines, specifically as follows:

[0130] When the driving coefficient of the external driving force is greater than the critical value of the chaotic state, the oscillator chaotic system is used for signal detection of the change in zero sequence current of each line before and after the fault;

[0131] The output phase diagram of different lines is obtained.

[0132] The small signal detection principle of Holmes-Duffing oscillator system is as follows:

[0133] Holmes-Duffing oscillator system is commonly used for basic nonlinear dynamics research and theoretical analysis, and is widely used to understand basic vibration characteristics. The system has very high sensitivity to given parameters and can have good immunity to noise and other interference. Holmes-Duffing oscillator system has the ability to process disturbances and enhance small signals, and the specific performance depends on the nonlinear characteristics and parameter configuration of the system.

[0134] Holmes-Duffing equation as formula (12), by selecting the appropriate parameters, especially the selection of damping coefficient, can eliminate the interference of a particular frequency. In the case of resonance, the system can amplify the tiny amount, so that the signal is significantly enhanced, specifically:

[0135]

[0136] The equation (12) is written as a state equation as formula (13)

[0137]

[0138] In the formula, x is the displacement of the oscillator, δ is the damping coefficient, pcos(t) is the external driving force, p is the driving coefficient of the external driving force, and ω is the frequency of the external driving force. Holmes-Duffing oscillator system can change the motion state of the system by modifying the driving coefficient p of the external driving force. With the increase of the coefficient from the beginning, the system will enter the homoclinic orbit, period doubling bifurcation, chaotic state and periodic state.

[0139] Based on the parameter setting of Holmes-Duffing oscillator system detection, specifically:

[0140] When the system is not given a signal, the damping ratio of the oscillator system is δ=0.4, the initial displacement x=0.5, the initial speed y=0.6, the frequency of the external driving force ω=1, and the driving coefficient of the external driving force p is mainly changed, let p increase from 0, the system will gradually show homoclinic orbit, period doubling bifurcation, chaotic state and large period state. When p is very small, the phase trajectory diagram of the system output shows the homoclinic orbit state; increase the value of p, the output of the system gradually changes from the homoclinic orbit state to the chaotic state. When the critical value of the chaotic state is exceeded, the system will enter the standard periodic state.

[0141] Holmes-Duffing oscillator system has very rich nonlinear characteristics, mainly through adjusting the size of p to determine the state boundary critical value, in the process of constantly changing the driving coefficient p of the external driving force, the critical value between each state can be found. Because of the high sensitivity of the system, although the parameters have slight changes, the output phase diagram state will change to some extent, especially when the external force coefficient p exceeds the critical value, the change is more obvious. Similarly, a small signal is input into the Holmes-Duffing oscillator system, even if there is a slight difference between different signals, but under the action of Duffing oscillator system, through the difference of the system output phase diagram state, the signal can be easily identified.

[0142] The fault line selection according to the state of the output phase diagram of different lines, determines the fault line, specifically:

[0143] obtaining output phase diagrams of different lines;

[0144] When the output phase diagram state of a certain line is different from the output phase diagram states of all other lines, and the output phase diagram states of all other lines are the same, the certain line is determined as a fault line, and all other lines are determined as non-fault lines.

[0145] The output phase diagram states of the different lines include two cases, specifically:

[0146] One case is that the output phase diagram of the fault line is in a periodic state, and the output phase diagram of the non-fault line is in a chaotic state.

[0147] The other case is that the output phase diagram of the fault line is in a quasiperiodic state, and the output phase diagram of the non-fault line is in a periodic state.

[0148] When the Holmes-Duffing oscillator system is applied to the coal mine distribution network for fault line selection, the zero sequence current variation of each line before and after the fault is taken as the input. Figure 2 When a high-resistance ground fault occurs in one line of the system, the zero sequence current variation of the four lines is taken as the input, and the Holmes-Duffing oscillator system outputs four phase diagrams. The phase diagrams of the fault line and the non-fault line are in different states. One case is that the signal output of the fault line is in a periodic state, and the signal output of the non-fault line is in a chaotic state. The other case is that the signal output of the fault line is in a chaotic state, and the signal output of the non-fault line is in a periodic state. In summary, when a single-phase high-resistance ground fault occurs in the coal mine distribution network, the Holmes-Duffing oscillator system takes the zero sequence current variation of the fault line and the non-fault line as the input, and the generated phase diagram state has obvious characteristic differences. The chaotic state of the phase diagram can realize ground fault line selection.

[0149] Example analysis

[0150] The simulation model is built, and MATLAB programming and MATLAB / Simulink modeling simulation are combined to verify the effectiveness of the line selection strategy proposed in the embodiment under the discussed scenario. According to the actual situation of the coal mine, part of the hardware is simplified, and the main part is built as shown in Figure 10 The model mainly introduces a main line and four outgoing lines under the 10KV environment, as well as the parameters of the four cables. The parameter structure is cable type-3×cable diameter-cable length. A switch is placed at the neutral point, and the control of the switch realizes two grounding modes of neutral point not grounded and neutral point grounded through an arc suppression coil.

[0151] The parameters of each line in the simulation model under normal operation can be calculated by consulting the design and calculation manual of thermal characteristics of cable factories, as shown in Table 1.

[0152] Table 1 Parameter values of each line in the simulation model

[0153]

[0154]

[0155] The specific state equation is shown in equation (13). Given the parameters, set the damping coefficient to a fixed value δ = 0.4, the initial displacement x = 0.5, the initial velocity y = 0.6, the grounding impedance R d = 90 KΩ, the parameter p = 0.6827 of the external driving force is determined through experiments, and the modeling simulation frequency f = 50 Hz.

[0156] Effectiveness analysis of high-resistance grounding fault line selection criterion based on SSIA

[0157] Neutral point ungrounded system

[0158] Figure 10 The middle switch s1 is opened, the neutral point is ungrounded, and line 1 is set to have a fault. The given parameters are applied to the simulation model built using Matlab / Simulink. During simulation, both three-phase balanced and three-phase unbalanced load conditions are considered. The zero-sequence currents of each line before and after the fault are collected, the changes in zero-sequence current before and after the fault are obtained by subtraction, and the phase sizes are calculated. The results for three-phase balanced load are shown in Table 2, and the results for three-phase unbalanced load are shown in Table 3.

[0159] Table 2 Phase of zero-sequence current change of each line in neutral point ungrounded three-phase balanced load

[0160]

[0161] Table 3 Phase of zero-sequence current change of each line in neutral point ungrounded three-phase unbalanced load

[0162]

[0163] Comparing Table 2 with Table 3, it can be seen that the three-phase load balance and imbalance has little effect on the phase and amplitude of the change of zero sequence current of each line, verifying the applicability of the criterion under three-phase load imbalance; at the same time, it is analyzed that the phase direction of the change of zero sequence current of the fault line and the non-fault line is opposite before and after the fault, the phase of the change of zero sequence current of line 1 is different from that of the other three lines, and the phases of the change of zero sequence current of the other three lines are the same, so it is judged that line 1 is the fault line, which is consistent with the fault line set in the simulation, verifying the effectiveness of the criterion under the neutral point non-grounded mode.

[0164] Neutral point through arc suppression coil grounding system

[0165] Figure 10 The middle switch s1 is closed, the neutral point adopts the arc suppression coil grounding mode, line 1 is set to be faulty, and the given parameters are applied to the model using Matlab / Simulink to build a simulation model. When simulating, both three-phase balanced and three-phase unbalanced load conditions are considered. The zero sequence currents before and after the fault are collected respectively, the difference between them is obtained to get the change of zero sequence current before and after the fault, and the phase is calculated. The results are shown in Table 4 when the three-phase load is balanced; the results are shown in Table 5 when the three-phase load is unbalanced.

[0166] Table 4 Phase of change of zero sequence current of each line of neutral point through arc suppression coil grounding three-phase balanced load

[0167]

[0168] Table 5 Phase of change of zero sequence current of each line of neutral point through arc suppression coil grounding three-phase unbalanced load

[0169]

[0170] From the analysis of Table 4.4 and Table 4.5, it can be seen that the three-phase unbalance has little effect on the change of zero sequence current of each line before and after the fault, and the phase of the change of zero sequence current of line 1 is different from that of the other three lines. By comparing the phase, it is judged that line 1 is the fault line, which is consistent with the fault line set in the simulation, verifying the effectiveness of the criterion under the neutral point through arc suppression coil grounding mode.

[0171] Analysis of the influence of different cable parameters on the criterion

[0172] In order to explore the influence of different cable parameters on the criterion, different cables are set to be faulty for comparison, Figure 10 The middle switch s1 is opened, the neutral point adopts the non-grounded mode, line 3 (the longest line) is set to be faulty, and the calculation method is the same as described above, and the results are shown in Table 6. Figure 10The middle switch s1 is closed, the neutral point is grounded through the arc suppression coil, and line 3 is set to fail, and the results are shown in Table 7.

[0173] Table 6 Phase of zero sequence current variation of each line of the longest line fault of the neutral point ungrounded system

[0174]

[0175] Table 7 Phase of zero sequence current difference of each line of the longest line fault of the neutral point grounded through the arc suppression coil system

[0176]

[0177] By analyzing Table 6 and Table 7, it can be seen that the phase of the zero sequence current variation before and after the fault of line 3 is different from that of the other three lines. By judging the phase size, it is determined that line 3 is the fault line, which is consistent with the simulation setting fault line, verifying the effectiveness of the criterion when different lines and different parameters fail.

[0178] High resistance grounding fault line selection identification method based on SSIA-Holmes-Duffing

[0179] for neutral point ungrounded system

[0180] When the neutral point is not grounded, the three-phase load is in a balanced state, and each phase resistance R of each line is 1000 Ω. At the same time, line 1 is set to fail. According to the above data, the zero sequence current variation before and after the fault of the four lines is input into the Holmes-Duffing oscillator system for simulation verification, and the simulation results are as follows. Figure 11

[0181] By comparing the four phase diagrams, it is found that the output phase diagram with line 1 signal is in a chaotic state, while the output phase diagrams with signals of other lines are in a periodic state. The output phase diagram of line 1 is obviously different from the output phase diagrams of the other three lines. According to the theory proposed in the second chapter, it can be determined that line 1 has a high resistance grounding fault, which is consistent with the simulation setting fault line, and conforms to the line selection strategy proposed in this embodiment.

[0182] for neutral point grounded through arc suppression coil system

[0183] The simulation model parameters and the Holmes-Duffing oscillator system parameters remain unchanged, and line 1 is still set to fail. Only the neutral point of the simulation model is grounded through the arc suppression coil, and the over-compensation method is used. The over-compensation degree is generally in the range of 0-10%. According to the size of the grounding inductance should be 13.26H≤L≤14.6H. In this embodiment, the grounding inductance L is taken as 13.5H, and the signals of the four lines are input into the Holmes-Duffing oscillator system, and the output phase diagram is as follows.​Figure 12 are shown.

[0184] Comparison Figure 12 From the four phase diagrams, it is concluded that the output phase diagram of line 1 is in a chaotic state, and the other three lines are in a periodic state. The output phase diagrams of line 1 and the other three lines are obviously different, which is consistent with the theory proposed in the second chapter, verifying the effectiveness of the line selection strategy proposed in this embodiment. It can be determined that the single-phase high-impedance ground fault of line 1 is consistent with the fault set in the simulation. The applicability of the method proposed in this embodiment in the arc suppression coil grounding system is verified through simulation.

[0185] Considering the influence of three-phase load imbalance

[0186] In the adaptability analysis in the first chapter, it has been obtained through formula derivation and theoretical analysis that the line selection strategy proposed in this embodiment will not be affected by three-phase load imbalance. This section simulates and verifies the theoretical analysis. The load imbalance is shown in Table 8. Under the conditions of neutral grounding and neutral grounding through arc suppression coil, the phase diagrams output by the Duffing oscillator system are shown in Figure 13 and Figure 14 .

[0187] Table 8: Load parameter values of each line

[0188]

[0189]

[0190] In Figure 13 and Figure 14 , the output phase diagram of line 1 is in a chaotic state, and the other three lines are in a periodic state. Under the condition of three-phase load imbalance, line 1 can still be determined as the fault line, which is consistent with the fault line set in the simulation. The fault line selected under the two grounding modes is consistent with the fault line set in the simulation. Through the analysis of the output phase diagram, the line selection strategy proposed in this embodiment is still applicable when the load is imbalanced.

[0191] Considering the influence of different cable parameters

[0192] The above simulation verification is for the fault of line 1, which is the shortest line. This section will verify whether the line selection strategy proposed in this embodiment can be distinguished by the output phase diagram when the longest line is faulty. When line 3 has a high-impedance ground fault under the conditions of neutral grounding and neutral grounding through arc suppression coil, the change in zero-sequence current before and after the fault of the four lines is input into the Duffing oscillator system, and the output phase diagram is shown in Figure 15 , Figure 16 .

[0193] Comparison Figure 15 and Figure 16 In the four phase diagrams of, it is obvious that the phase diagram of the signal output of line 3 is in a chaotic state, and the other three lines are in a periodic state, which can be judged to be a single-phase high-resistance ground fault of line 3, which is consistent with the fault line set in the simulation, verifying the effectiveness of the strategy proposed in this embodiment.

[0194] The embodiment proposes a mine cable non-effective grounding fault line selection and identification method based on SSIA and Holmes-Duffing oscillator small signal detection fusion. Through actual system example verification, the following conclusions are drawn:

[0195] Through SSIA analysis, it can be known that the phase and amplitude of the fault line zero sequence current variation are different from those of the non-fault line zero sequence current variation, and the non-fault line zero sequence current variation is in common; the phase of the fault line zero sequence current variation is the same as the phase of the fault phase-to-ground voltage of the fault line. The above conclusions are verified through modeling and simulation.

[0196] The embodiment proposes a mine cable non-effective grounding fault line selection and identification method based on SSIA and Holmes-Duffing oscillator small signal detection fusion. First, the zero sequence current of each line is collected and calculated. Then, the phase diagram is obtained through the Holmes-Duffing oscillator system, and the fault line is identified by judging the chaotic relationship of the phase diagram of each line. Through example analysis, the effectiveness and applicability of the proposed method are verified. Based on the fault line selection of the non-effective grounding system, the influence of the size of the grounding impedance on the line selection criterion is further considered in the future, and then the grounding impedance range suitable for this method is determined.

[0197] Embodiment two

[0198] The embodiment provides a coal mine power grid mine cable high-resistance grounding fault line selection system, which comprises:

[0199] The zero sequence current vector calculation module is configured to calculate the zero sequence current vectors of each line before and after the fault based on the zero sequence currents of each line before and after the fault;

[0200] The zero sequence current variation determination module is configured to determine the zero sequence current variation of each line before and after the fault according to the difference between the zero sequence current vectors of each line before and after the fault;

[0201] The zero sequence current variation signal detection module is configured to perform signal detection on the zero sequence current variation of each line before and after the fault based on the zero sequence current variation of each line before and after the fault, and obtain the output phase diagram of different lines by using an oscillator chaotic system;

[0202] The fault line selection module is configured to select the fault line according to the state of the output phase diagram of different lines and determine the fault line.

[0203] The above modules and the corresponding steps achieve the same examples and application scenarios as the above-described embodiment one, but are not limited to the content disclosed in the above-described embodiment one. It should be noted that the above modules can be executed in a computer system such as a set of computer executable instructions as a part of the system.

[0204] The description of each of the above embodiments has its own focus, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0205] The proposed system can be implemented in other ways. For example, the above-described system embodiments are only illustrative, for example, the division of the above modules is only a logical function division, and in actual implementation, there can be another division manner, for example, a plurality of modules can be combined or integrated into another system, or some features can be ignored or not executed.

[0206] Embodiment three

[0207] The embodiment provides a computer readable storage medium, which stores a computer program, and the program is executed by a processor to realize the steps in the coal mine power grid mine cable high resistance grounding fault line selection method according to the above-described embodiment one.

[0208] Embodiment four

[0209] The embodiment provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor realizes the steps in the coal mine power grid mine cable high resistance grounding fault line selection method according to the above-described embodiment one when executing the program.

[0210] Embodiment five

[0211] The embodiment provides a computer program product or a computer program, which includes computer instructions stored in a computer readable storage medium. A processor of a computer device reads the computer instructions from the computer readable storage medium, and the processor executes the computer instructions, so that the computer device executes the steps in the coal mine power grid mine cable high resistance grounding fault line selection method according to the above-described embodiment one.

[0212] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can 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.

[0213] The embodiments of methods, apparatuses (systems) and computer program products according to the present application can be described in reference to flowchart and / or block diagram illustrations of methods, apparatuses (systems) and computer program products according to embodiments of the present application. It will be understood that each block of the flowchart and / or block diagrams and combinations of blocks in the flowchart 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, create means for implementing the functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0214] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0215] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks.

[0216] It is to be understood that all or part of the functions of the methods described above can be implemented by a computer program instructing relevant hardware, and the program can be stored in a computer readable storage medium. When the program is executed, it can include the flow of each embodiment of the method described above. The storage medium can be a magnetic disc, an optical disc, a read-only memory (ROM) or a random access memory (RAM), etc.

[0217] The above describes the specific embodiments of the present application in conjunction with the accompanying drawings, but is not a limitation on the scope of protection of the present application. Those skilled in the art should understand that various modifications or variations made by those skilled in the art without creative labor on the basis of the technical solutions of the present application are still within the scope of protection of the present application.

Claims

1. A method for locating high-resistance grounding faults in mining cables of coal mine power grids, characterized in that, include: Calculate the zero-sequence current vector of each line before and after the fault based on the zero-sequence current of each line before and after the fault. Based on the difference between the zero-sequence current vectors of each line before and after the fault, the change in zero-sequence current of each line before and after the fault is determined, specifically as follows: ； In the formula, This represents the zero-sequence current vector after the fault in the nth cycle. This represents the zero-sequence current vector prior to the fault in the two cycles preceding the nth cycle. This represents the change in zero-sequence current of each line before and after the fault. Based on the changes in zero-sequence current of each line before and after the fault, signal detection is performed using an oscillator chaotic system to obtain the output phase diagrams of different lines, specifically: When the driving coefficient of the external driving force is greater than the critical value of the chaotic state, the oscillator chaotic system is used to detect the changes in the zero-sequence current of each line before and after the fault. Obtain the output phase diagrams for different lines; Based on the status of the output phase diagrams of different lines, fault line selection is performed to determine the faulty line, specifically as follows: Obtain the output phase diagrams for different lines; When the output phase diagram state of a certain line is different from that of all other lines, and the output phase diagram states of all other lines are the same, then the certain line is determined to be a faulty line, and all other lines are non-faulty lines.

2. The method for selecting the fault location of high-resistance grounding cables in coal mine power grids as described in claim 1, characterized in that, The output phase diagrams of the different lines include two states, specifically: One scenario is that the output phase diagram of the faulty line is in a periodic state, while the output phase diagram of the non-faulty line is in a chaotic state. Another scenario is that the output phase diagram of the faulty line is in a chaotic state, while the output phase diagram of the non-faulty line is in a periodic state.

3. The method for selecting the fault location of high-resistance grounding cables in coal mine power grids as described in claim 1, characterized in that, Based on the zero-sequence current of each line before and after the fault, the zero-sequence current vector of each line before and after the fault is calculated using Fast Fourier Transform.

4. A fault location system for high-resistance grounding cables in coal mine power grids, characterized in that, The method for locating high-resistance grounding faults in coal mine power grid cables as described in any one of claims 1-3 includes: The zero-sequence current vector calculation module is configured to calculate the zero-sequence current vector of each line before and after the fault based on the zero-sequence current of each line before and after the fault. The zero-sequence current change determination module is configured to determine the change in zero-sequence current of each line before and after the fault based on the difference between the zero-sequence current vectors of each line before and after the fault. The zero-sequence current change signal detection module is configured to detect the signal based on the zero-sequence current change of each line before and after the fault using the oscillator chaotic system, and obtain the output phase diagram of different lines. The fault selection module is configured to select the faulty line based on the status of the output phase diagram of different lines.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the method for selecting high-resistance grounding faults in mining cables of coal mine power grids as described in any one of claims 1-3.

6. 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, it implements the steps in the method for selecting high-resistance grounding faults in mining cables of coal mine power grids as described in any one of claims 1-3.

7. A computer program product, characterized in that, The computer program product includes a computer program that, when executed by a processor, implements the steps in the method for selecting high-resistance grounding faults in mining cables for coal mine power grids as described in any one of claims 1-3.

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