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

Abstract

The invention belongs to the field of power system relay protection, and provides a mine cable high-resistance grounding fault line selection method and system for a coal mine power grid, and the method comprises the steps: calculating the zero-sequence current vector of each line before and after a fault based on the zero-sequence current of each line before and after the fault; determining the zero-sequence current variable quantity of each line before and after the fault according to the difference value of the zero-sequence current vector of each line before and after the fault; based on the zero-sequence current variation of each line before and after the fault, performing signal detection by using an oscillator chaotic system to obtain output phase diagrams of different lines; and performing fault line selection according to the states of the output phase diagrams of different lines, and determining a fault line. According to the method, the fault line is judged according to the principle that the phase and the amplitude of the zero-sequence current variable quantity of the fault line are different from the phase of the zero-sequence current variable quantity of the non-fault line, and the zero-sequence current variable quantity of the non-fault line is the same, so that the fault line can still be judged under the condition that the three-phase load is unbalanced; and the accuracy and the universality of high-resistance grounding fault line selection are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of relay protection of power systems, and particularly relates to a method and a system for selecting a high-resistance grounding fault line of a mine-used cable in a coal mine power grid. 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] The 10kV and 6kV power grids in coal mines generally adopt the non-effective grounding system mode of ungrounded neutral point or neutral point grounded through an arc suppression coil. When a high-resistance grounding fault occurs in the cable under this grounding system mode, the zero-sequence current is small, the fault characteristics are not obvious, and the interference is large, making it 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, which leads to misjudgment of line selection; therefore, how to realize fault line selection has always been a research hotspot in the electrical field.

[0004] At present, scholars at home and abroad have done a lot of research work and proposed various fault line selection methods. Among them, the fault line selection methods for non-effective grounding systems mainly analyze from two aspects of steady-state characteristics and transient characteristics. Some methods adopt the zero-sequence current amplitude comparison method to compare the amplitudes of each line, and the line with the largest amplitude is the fault line. There are also methods that adopt the zero-sequence current group amplitude-phase comparison method, select the three lines with the largest amplitudes, and then compare the phases of the three lines to select the fault line. In addition, in the flexible grounding system in the prior art, the high-resistance grounding fault line selection is realized by comparing the zero-sequence measured impedance of each line. There are also methods that perform EMD decomposition on the steady-state current signal, and then use the fifth harmonic of each line current as the input and input it 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, and after normalization processing, the signals of each frequency band are used as characteristic quantities, and pso-svm is used as a fault diagnosis model for training to realize fault diagnosis; there are also research methods that use the fault location principle of transient components, collect the components of the zero-sequence network, and realize accurate positioning through the grouping comparison method. There are also research methods that propose a traveling wave method for comparing the similarity of current waveforms, which makes full use of transient traveling wave information and calculates the comprehensive similarity coefficient of traveling wave waveforms between lines. Among the above methods, the electrical signals in the steady-state characteristics, such as zero-sequence voltage, zero-sequence current, three-phase voltage and other state quantities, are more stable, and their signal characteristics are easier to extract, so it is more convenient to realize fault line selection.

[0005] However, the above research methods still have the following problems. First, there are various types of line faults, including metallic grounding, high-resistance grounding, etc. Different fault types have different fault characteristics. Considering the influence of unbalanced three-phase loads and different parameters of different types of cables on the criterion at the same time, this makes the universality of a single fault line selection method relatively weak. Second, the criterion for comparing the phase change and amplitude change of zero-sequence current, although simple in principle and easy to implement, has high requirements for recognition accuracy and is easily affected by factors such as unbalanced current, system operation mode, noise, etc., resulting in misjudgment of line selection. Third, the method based on the relevant quantities of steady-state zero-sequence current as the line selection basis has certain applications in actual engineering. However, through formula derivation and actual application research, it shows that when a high-resistance grounding fault occurs in the coal mine system, regardless of the characteristics adopted, the steady-state zero-sequence current characteristic is a small signal, which is difficult to adopt in actual engineering. Summary of the Invention

[0006] To solve the above problems, the present invention proposes a method and system for selecting a high-resistance grounding fault line of a mine-used cable in a coal mine power grid. The present invention uses the amplitude and phase of the zero-sequence current change amount before and after the line fault as the criterion, and can accurately identify and determine the fault line and non-fault line under the condition of unbalanced three-phase loads and the influence of different cable parameters.

[0007] According to some embodiments, the first solution of the present invention provides a method for selecting a high-resistance grounding fault line of a mine-used cable in a coal mine power grid, and adopts the following technical solution:

[0008] A method for selecting a high-resistance grounding fault line of a mine-used cable in a coal mine power grid includes:

[0009] Calculating the zero-sequence current vectors of each line before and after the fault based on the zero-sequence current of each line before and after the fault;

[0010] Determining the zero-sequence current change amount 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;

[0011] Based on the zero-sequence current change amount of each line before and after the fault, using the oscillator chaotic system for signal detection to obtain the output phase diagrams of different lines;

[0012] Selecting the fault line according to the states of the output phase diagrams of different lines to determine the fault line.

[0013] Further, the determining the zero-sequence current change amount 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 is specifically:

[0014]

[0015] In the formula, is the zero-sequence current vector after the fault in the nth cycle, is the zero-sequence current vector before the fault in the first two cycles before the nth cycle, is the change in zero-sequence current of each line before and after the fault.

[0016] Furthermore, based on the change in zero-sequence current of each line before and after the fault, a signal detection is performed using an oscillator chaotic system to obtain the output phase diagrams of different lines, specifically as follows:

[0017] 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 perform signal detection on the change in zero-sequence current of each line before and after the fault;

[0018] The output phase diagrams of different lines are obtained.

[0019] Furthermore, the fault line is selected according to the states of the output phase diagrams of different lines to determine the fault line, specifically as follows:

[0020] Obtain the output phase diagrams of different lines;

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

[0022] Furthermore, the states of the output phase diagrams of different lines include two situations, specifically as follows:

[0023] One situation is that the output phase diagram of the fault line is in a periodic state, while the output phase diagrams of non-fault lines are in a chaotic state;

[0024] Another situation is that the output phase diagram of the fault line is in a chaotic state, while the output phase diagrams of non-fault lines are in a periodic state.

[0025] Furthermore, based on the zero-sequence current of each line before and after the fault, the zero-sequence current vectors of each line before and after the fault are calculated using the fast Fourier transform.

[0026] According to some embodiments, the second solution of the present invention provides a high-resistance grounding fault line selection system for mine-used cables in a coal mine power grid, adopting the following technical solution:

[0027] A high-resistance grounding fault line selection system for mine-used cables in a coal mine power grid, comprising:

[0028] A zero-sequence current vector calculation module configured to calculate the zero-sequence current vectors 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 change amount determination module configured to determine the change amount of zero-sequence current 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] Zero-sequence current variation signal detection module, configured to perform signal detection using an oscillator chaotic system based on the zero-sequence current variations of each line before and after a fault, and obtain the output phase diagrams of different lines;

[0031] Fault line selection module, configured to perform fault line selection based on the states of the output phase diagrams of different lines and determine the fault line.

[0032] According to some embodiments, the third solution of the present invention provides a computer-readable storage medium.

[0033] A computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the steps in a method for selecting a fault line of a high-resistance grounded fault of a mine-used cable in a coal mine power grid as described in the first aspect above.

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

[0035] A computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, it implements the steps in a method for selecting a fault line of a high-resistance grounded fault of a mine-used cable in a coal mine power grid as described in the first aspect above.

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

[0037] The present invention provides a computer program product or a computer program, which includes 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, so that the computer device executes the steps in a method for selecting a fault line of a high-resistance grounded fault of a mine-used cable in a coal mine power grid as described in the first aspect above.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

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

[0040] The present invention proposes a small-signal detection method for the Holmes-Duffing oscillator chaotic system. When a high-resistance grounding fault occurs in the non-effectively grounded system of a coal mine power grid, the change in zero-sequence current is a small signal between several hundred microamperes and several milliamperes, which is difficult to detect in actual engineering. The present invention proposes to extract the change in zero-sequence current signal of the faulty line, use it as the input of the Holmes-Duffing oscillator system, and utilize the high sensitivity of the oscillator system to specific small signals to extract the small-signal fault characteristics. Then, according to the chaos principle of the Holmes-Duffing oscillator system, phase trajectories of different lines are generated, the relationship between the chaotic period state of the system and the external driving force is analyzed, and the output phase diagram states are compared to achieve accurate fault line selection for the high-resistance grounding fault in the non-effectively grounded system of the coal mine power grid. Description of the Drawings

[0041] The accompanying 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 of the present invention.

[0042] Figure 1 is a flow chart of a method for selecting a high-resistance grounding fault line of a mine-used cable in a coal mine power grid according to an embodiment of the present invention;

[0043] Figure 2 is an equivalent model of a coal mine power grid according to an embodiment of the present invention;

[0044] Figure 3 is the zero-sequence network of a coal mine power grid according to an embodiment of the present invention;

[0045] Figure 4 is a simplified diagram of the zero-sequence network according to an embodiment of the present invention;

[0046] Figure 5 is an equivalent operation circuit of the faulty line according to an embodiment of the present invention;

[0047] Figure 6 is the zero-sequence equivalent circuit of a single-phase grounding fault line according to an embodiment of the present invention;

[0048] Figure 7 is an equivalent model of arc suppression coil grounding according to an embodiment of the present invention;

[0049] Figure 8 is the zero-sequence equivalent model of arc suppression coil grounding according to an embodiment of the present invention;

[0050] Figure 9 is an equivalent circuit of a line with a three-phase unbalanced load connected according to an embodiment of the present invention;

[0051] Figure 10 is a cable parameter simulation model according to an embodiment of the present invention;

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

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

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

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

[0056] Figure 15 is the output phase diagram of the Holmes-Duffing oscillator system when a fault occurs in the longest line with the neutral point not grounded in the embodiment of the present invention;

[0057] Figure 16 is the output phase diagram of the Holmes-Duffing oscillator system when a fault occurs in the longest line with the neutral point grounded through an arc suppression coil in the embodiment of the present invention. Detailed implementation manners

[0058] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0059] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanations 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.

[0060] 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 form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0061] Without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0062] Embodiment 1

[0063] This embodiment provides a method for selecting the line with a high-resistance grounding fault in a mine-used cable of a coal mine power grid. This embodiment takes the application of this method to a server as an example. It can be understood that this method can also be applied to a terminal, and can also be applied to a system including a terminal and a server, and is implemented through the interaction between the terminal and the server. The server can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network servers, cloud communications, middleware services, domain name services, security services CDN, and big data and artificial intelligence platforms. The terminal can be a smart phone, a tablet computer, a notebook computer, a desktop computer, a smart speaker, a smart watch, etc., but is not limited thereto. The terminal and the server can be directly or indirectly connected through wired or wireless communication methods, and this application does not make any restrictions here. In this embodiment, the method includes the following steps:

[0064] 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;

[0065] Determine the zero-sequence current change amount 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;

[0066] Based on the zero-sequence current change amount of each line before and after the fault, use the oscillator chaotic system to perform signal detection to obtain the output phase diagrams of different lines;

[0067] Select the fault line according to the states of the output phase diagrams of different lines to determine the fault line.

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

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

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

[0071] The determination of the zero-sequence current change amount 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 is specifically:

[0072]

[0073] In the formula, is the zero-sequence current vector after the fault in the nth cycle, is the zero-sequence current vector before the fault in the two cycles before the nth cycle, is the zero-sequence current change amount of each line before and after the fault;

[0074] Step 3: Obtain the zero-sequence current variation of each line and use it as the input of the Holmes-Duffing oscillator system;

[0075] Step 4: Perform the Holmes-Duffing oscillator system algorithm operation to obtain the output phase diagram;

[0076] Step 5: Judge the state of the obtained output phase diagram. The lines with the same output phase diagram state are healthy lines, and the lines with different output phase diagram states are faulty lines.

[0077] First, based on the high-resistance grounding fault line selection criterion of the steady-state impedance analysis method, in a coal mine distribution network, there is generally a high-voltage main power supply line to deliver electricity from the substation to the main equipment and areas in the mining area. The incoming line of the coal mine substation generally uses an incoming line of 110 kV, which is transformed to 6 kV or 10 kV medium and low voltages through the main transformer. The 6 kV and 10 kV power supply systems will have multiple power supply areas, which are led out 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 grounding method on the 10 kV side of the transformer in a 110 / 10 kV coal mine substation generally adopts a non-effective grounding method, that is, the neutral point non-grounding method and the neutral point grounded through an arc suppression coil method. The following conducts circuit analysis on the two methods.

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

[0079] In the study of the steady-state fault characteristics of a single-phase grounding fault, the admittance of the line has little influence on the system, and the resistance and inductive reactance of the line are much smaller than the capacitive reactance of the circuit. Therefore, the resistance and inductance of the line can be ignored when drawing the equivalent circuit diagram. In this embodiment, according to the actual 10 kV power grid structure of an underground coal mine, an equivalent model of the coal mine distribution network as shown in Figure 2 is established. Its neutral point adopts a non-grounding method. For the convenience of circuit analysis, the model considers a single busbar and four outgoing branch methods. The single-phase grounding short circuit, two-phase short circuit, single-phase open circuit fault, etc. that occur in the system are all asymmetric short circuits. When an asymmetric fault occurs in the power system, the three-phase impedances are not the same, the three-phase voltage and current effective values are not equal, and the phase differences between phases are also not equal. Therefore, when analyzing, the three-phase situation must be considered simultaneously. In this embodiment, the symmetrical component method is used to analyze the system fault problem.

[0080] When the four cables are operating normally and it is assumed that the second cable has a single-phase high-resistance grounding fault, the system will generate zero-sequence current. The equivalent zero-sequence network diagram is as shown in Figure 3As shown. When a fault occurs in the second line, in the zero-sequence network, a voltage source with the same magnitude and direction as the zero-sequence voltage is equivalently added at the fault point, which can be equivalently represented by the voltage source U0. For the coal mine power grid, the longest cable power supply line generally does not exceed 3 km. In short-distance cables, the influence of using the π-type equivalent circuit and T-type equivalent circuit parameters on the steady-state analysis results is extremely small and can be ignored. In the zero-sequence network of this embodiment, the line adopts the T-type equivalent circuit. In the figure, Z L1 、Z L2 、Z L3 、Z L4 are the zero-sequence impedances of four cable lines, and Z1, Z3, and Z4 are the insulation impedances of the first line, the third line, and the fourth line respectively. The line end is connected to the load. In the figure are the zero-sequence currents of the four lines.

[0081] Figure 3 In Figure 3 n >>Z Ln , so Figure 3 can be simplified, the zero-sequence impedance of the line is ignored, and the insulation impedance is represented at the same time. The simplified zero-sequence network diagram is as shown in Figure 4 .

[0082] For the non-faulty phase line, the relationship between the zero-sequence current and the zero-sequence voltage can be obtained as follows:

[0083]

[0084] In the formula is the zero-sequence current of the non-faulty line;

[0085] For the faulty line, the relationship between the zero-sequence current and the zero-sequence voltage in Equation (1) no longer holds. Therefore, in this embodiment, the line with a single-phase ground fault is analyzed to study the relationship between the zero-sequence current and the zero-sequence voltage of the faulty line. The zero-sequence network equivalent circuit of the faulty line as shown in Figure 5 is established. Assume that a ground fault occurs in phase A. For the types of ground faults, such as metal ground and high-resistance ground, they are special cases of ground faults, and different types of faults can be realized by setting the ground resistance. Therefore, the ground impedance R d can be used to simulate the ground fault situation of single-phase ground. When R d is very large, it belongs to the occurrence of a single-phase high-resistance ground fault. In the figure is the phase voltage of the three-phase power supply, and R a , R b , R c are the insulation resistances of the three phases to the ground, and C a , C​​​​​​​​​​​​​​​​​​​​​​​​​​b , C c is the distributed capacitance between three phases and the ground, and R d is the equivalent resistance value of the grounded fault line. According to the three-phase characteristics of the line, the three-phase insulation impedance and 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] In the formula 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 Substituting the above conditions into Equation (2) and simplifying, we get:

[0089]

[0090] According to Equation (3), the zero-sequence voltage is generated by the combined action of the grounding impedance R d , the insulation impedance Z a , and the phase voltage of the fault phase . According to the formula, the internal zero-sequence voltage of Figure 4 can be equivalently represented by a new zero-sequence network equivalent circuit as shown in Figure 6 .

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

[0092]

[0093] Using Ohm's law to express each current in Equation (4) with voltage and impedance and simplifying, the relationship between the zero-sequence voltage and the phase voltage of the system during a fault is as follows:

[0094]

[0095] In the formula C Σ = C1 + C3 + C4 + 3C a , θ = arctan(jωC Σ R Σ) And the range of θ is between (0° - 90°). Then the phase voltage of the faulty phase leads the zero - sequence voltage by an angle between (90° - 180°). Combining the analysis of the zero - sequence current, when there is no single - phase - to - ground fault in the system, there is no grounding resistance, i.e., R d = 0. Substituting this condition into Equation (2), the zero - sequence current of the system before the fault can be obtained as The zero - sequence voltage of the system after the fault is Equation (3). Taking the difference between the zero - sequence current of the system after the fault and that before the fault, the difference in zero - sequence current before and after the fault is shown in Equation (6):

[0096]

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

[0098]

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

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

[0101]

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

[0103]

[0104] In the formula is the vector of the zero - sequence current in the nth cycle, is the vector of the zero - sequence current two cycles before the nth cycle, is the change in zero - sequence current in practical engineering.

[0105] Second, steady - state impedance analysis of high - resistance grounding faults in a system with a neutral point grounded through an arc suppression coil:

[0106] In actual coal mines, some power grids adopt the neutral point grounded through an arc suppression coil system. Although this grounding method can eliminate the arc generated by single-phase grounding faults and limit the impact current during faults, thereby improving the reliability and stability of the system. However, due to the compensation effect of the arc suppression coil, traditional grounding fault line selection methods or high-resistance grounding cannot accurately determine the faulty line. Therefore, in this embodiment, a circuit analysis is carried out on the neutral point grounded through an arc suppression coil system. Currently, the neutral point grounded through an arc suppression coil in coal mine distribution networks mainly adopts the over-compensation method, and the grounding model of the arc suppression coil is as Figure 7 shown.

[0107] The equivalent operation circuit for a fault is as Figure 5 shown, and the zero-sequence equivalent network when a fault occurs in the arc suppression coil grounding system is as Figure 8 shown.

[0108] Analyzing the relationship between the zero-sequence voltage and the phase voltage in the neutral point grounded through an arc suppression coil fault model, similar to the analysis method of the ungrounded system, the relationship in Equation (10) can be obtained as follows:

[0109]

[0110] In the formula, L is the inductance of the grounding arc suppression coil, Moreover, in the arc suppression coil grounding system, the over-compensation method is adopted, and in terms of formula expression, it is This results in θ being in the range of (-90° - 0). Compared with the ungrounded system, the zero-sequence voltage is actually ahead of the phase voltage of the faulty phase by (90° - 180°) in terms of phase.

[0111] Comparing Equation (5) with Equation (10), it can be seen that the change in the total insulation parameters of the system is related to the neutral point grounding method of the system. Although the neutral grounding method will affect the zero-sequence voltage of the system, it will not affect the relationship between the zero-sequence electrical signal of the cable and the insulation parameters.

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

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

[0114] 2. The phase of the zero-sequence current change of the faulty line is the same as the phase of the ground voltage of the faulty phase of the faulty line. In this embodiment, the difference between the zero-sequence current change of the faulty line and the non-faulty lines is used as the basis for fault line selection, that is, by comparing the phase and amplitude relationships of the zero-sequence current changes of the four lines, this method can identify the faulty line and achieve the fault diagnosis of the cable, thereby improving the efficiency and accuracy of fault handling.

[0115] Through simulation, it is found that in actual engineering applications, the change in zero-sequence current of the line is in the microampere level. Especially in the coal mine environment, the change in zero-sequence current, as a tiny signal, is extremely vulnerable to interference. In actual engineering applications, it is difficult to effectively identify tiny signals, and system misjudgment may occur due to noise or interference. Therefore, this embodiment proposes a method for selecting and identifying high-resistance grounding faults of mine cables in an uneffectively grounded system by integrating steady-state impedance analysis and small-signal detection of the Holmes-Duffing oscillator.

[0116] Firstly, the change in zero-sequence current is excavated through steady-state impedance analysis as a feature of the grounding fault criterion, and then the criterion is used 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 handle perturbations and has high sensitivity to tiny signals, and it can well solve the problem that the change in zero-sequence current before and after the fault is too small.

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

[0118] The first type is the high-resistance grounding fault line selection criterion considering unbalanced three-phase loads, specifically as follows:

[0119] In the actual coal mine distribution network, the end of the distribution network system is connected to the load to supply power to the load. When different single-phase loads are connected, due to different load parameters, there will be a situation of unbalanced three-phase loads. To verify the applicability of the fault line selection strategy proposed in this embodiment in actual situations, the influence of unbalanced three-phase loads on this strategy is mainly discussed.

[0120] Taking the occurrence of a single-phase high-resistance grounding fault as an example, the load is connected in a Y shape, and the equivalent circuit of the system is as Figure 9 shown. In the figure, R a , R b , R c are the magnitudes of the three-phase loads. When the three-phase loads are unbalanced, it will cause the current flowing into the load to be asymmetric. However, according to Kirchhoff's current law, the line currents flowing into the load still satisfy

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

[0122]

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

[0124] By comparing Equation (10) with Equation (2), it is found that the expressions of the zero-sequence current in the two cases are the same. Thus, it can be obtained that even if a three-phase unbalance occurs at the load end, it has no effect on the change in the zero-sequence current before and after the fault in each line of the system, nor does it affect the relationship between the insulation parameters of the line and the zero-sequence components during a fault. Through analysis, it can be seen that when there is a three-phase load unbalance in the system, it has no impact on the criterion proposed in this embodiment. In the case of a three-phase unbalance, the selection of the high-resistance grounding fault line can still be carried out.

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

[0126] In actual coal mines, the lines are diverse. Due to the different cables used in different situations and the variety of cable models, the parameters such as the impedance, length, and distributed capacitance of each line are different. When faults occur in different types and lengths of cables, it may also have an impact on the criterion proposed in this embodiment. Therefore, this section mainly discusses the impact of faults occurring in different lines on this strategy.

[0127] In the above analysis, the analysis of the zero-sequence components of the system was carried out taking the fault of Line 2 as an example. When faults occur in other lines, the analysis method is the same as the above analysis method. From the perspective of theoretical analysis, there is no impact when faults occur in different lines. Then, the criterion proposed in this embodiment is also valid.

[0128] Finally, the high-resistance grounding fault identification method based on the Holmes-Duffing oscillator system

[0129] Based on the change in the zero-sequence current of each line before and after the fault, the oscillator chaotic system is used for signal detection to obtain the output phase diagrams 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 to detect the change in the zero-sequence current of each line before and after the fault;

[0131] The output phase diagrams of different lines are obtained.

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

[0133] The Holmes-Duffing oscillator system is mostly used in basic nonlinear dynamics research and theoretical analysis and is widely used to understand basic vibration characteristics. This system has a very high sensitivity to the given parameters and can have a good immunity to other interferences such as noise. The Holmes-Duffing oscillator system has the ability to process perturbations and enhance weak signals, and its specific performance depends on the nonlinear characteristics and parameter configuration of the system.

[0134] The Holmes-Duffing equation is as shown in Equation (12). By appropriately selecting parameters, especially the damping coefficient, interference at a specific frequency can be eliminated. In the case of resonance, the system can amplify small quantities, significantly enhancing the signal, specifically as follows:

[0135]

[0136] Write Equation (12) as a state equation as shown in Equation (13)

[0137]

[0138] where 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, ω is the frequency of the external driving force. The Holmes-Duffing oscillator system can change the motion state of the system by modifying the driving coefficient p of the external driving force. As the coefficient starts to increase, the system will enter a homoclinic orbit, period-doubling bifurcation, chaotic state, and periodic state.

[0139] Based on the parameter settings for detection by the Holmes-Duffing oscillator system, specifically as follows:

[0140] When no signal is added to the system, assume the damping ratio δ of the oscillator system is 0.4, the initial displacement x = 0.5, the initial velocity y = 0.6, and the external driving force frequency ω = 1. Mainly change the driving coefficient p of the external driving force and let p increase from 0. The system will gradually exhibit a homoclinic orbit, period-doubling bifurcation, chaotic state, and large-period state. When p is very small, the phase trajectory diagram output by the system shows a homoclinic orbit state; increasing the value of p, the output of the system gradually changes from the homoclinic orbit state to the chaotic state. When exceeding the critical value of the chaotic state, the system will enter the standard periodic state.

[0141] The Holmes-Duffing oscillator system has very rich nonlinear characteristics. The state boundary criticality is mainly determined by adjusting the magnitude of p. During the continuous process of changing the driving coefficient p of the external driving force, the critical values between each state can be found. Due to the high sensitivity of the system, even if there are slight large changes in the parameters, the state of the output phase diagram will change to a certain extent. Especially when the external driving force coefficient p exceeds the critical value, this change is more obvious. Similarly, input a small signal into the Holmes-Duffing oscillator system. Even if there are slight differences between different signals, under the action of the Duffing oscillator system, through the differences in the output phase diagram states of the system, the signals can be easily identified.

[0142] Select the faulty line according to the state of the output phase diagram of different lines to determine the faulty line, specifically as follows:

[0143] Obtain the output phase diagrams of different lines;

[0144] 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 determine that the certain line is a faulty line and all other lines are non-faulty lines.

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

[0146] One case 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;

[0147] The other case 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.

[0148] When the Holmes-Duffing oscillator system is applied to fault line selection in a coal mine distribution network, the change in zero-sequence current before and after a fault occurs in each line is used as the input. Figure 2 When a high-resistance grounding fault occurs in one line of the system, the change in zero-sequence current of the four lines is used as the input. Four phase diagrams are output through the Holmes-Duffing oscillator system, and the phase diagrams of the faulty line and the non-faulty lines are in different states. One case is that the signal of the faulty line outputs a periodic state, while the signal of the non-faulty line outputs a chaotic state; the other case is that the signal of the faulty line outputs a chaotic state, while the signal of the non-faulty line outputs a periodic state. In summary, when a single-phase high-resistance grounding fault occurs in a coal mine distribution network, the Holmes-Duffing oscillator system uses the change in zero-sequence current of the faulty line and the non-faulty lines as the input, and the generated phase diagram states have obvious characteristic differences. The grounding fault line selection can be realized through the chaotic state of the phase diagram.

[0149] Case study

[0150] Build a simulation model. The simulation software combines MATLAB programming and MATLAB / Simulink modeling to verify the effectiveness of the line selection strategy proposed in this embodiment in the discussed scenario. According to the actual situation of the coal mine, some hardware is simplified, and the main part is shown to build the simulation model as Figure 10 shown. The model mainly introduces one main line and four outgoing lines in a 10 kV 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 two grounding methods, namely ungrounded neutral point and neutral point grounded through an arc suppression coil, are realized through the control of the switch.

[0151] By referring to the design calculation manual of the thermal characteristics parameters of the cable factory, the parameters of each line in the simulation model during normal operation can be calculated, 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 fixed value of the damping coefficient δ = 0.4, the initial displacement x = 0.5, the initial velocity y = 0.6, and the grounding impedance R d = 90 KΩ. Determine the parameter p = 0.6827 of the external driving force through experiments, and the modeling and simulation frequency f = 50 Hz.

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

[0157] Ungrounded neutral system

[0158] Figure 10 Open switch s1 in the middle, the neutral point adopts the ungrounded method, set line 1 to have a fault, and use Matlab / Simulink to build a simulation model and apply the given parameters to the model. During the simulation, consider both the three-phase balance and three-phase load imbalance of the system load. Collect the zero-sequence current of each line before the fault and the zero-sequence current of each line after the fault respectively, take the difference to obtain the change in the zero-sequence current before and after the fault and calculate its phase magnitude. The results are shown in Table 2 when the three-phase is balanced and in Table 3 when the three-phase is unbalanced.

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

[0160]

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

[0162]

[0163] By comparing Table 2 and Table 3, it can be seen that the balance and imbalance of the three-phase load have little effect on the phase and amplitude of the zero-sequence current variation of each line, verifying the applicability of the criterion under unbalanced three-phase loads. At the same time, it is analyzed that before and after the fault, the phase directions of the zero-sequence current variations of the faulty line and the non-faulty lines are opposite. The phase of the zero-sequence current variation of Line 1 is different from that of the other three lines, and the phases of the zero-sequence current variations of the other three lines are the same. Thus, it is determined that Line 1 is the faulty line, which is consistent with the faulty line set in the simulation, verifying the effectiveness of the criterion under the non-grounded neutral mode.

[0164] System with neutral grounded through an arc suppression coil

[0165] Figure 10 Switch S1 is closed, and the neutral point is grounded through an arc suppression coil. A fault is set to occur on Line 1, and a simulation model is built using Matlab / Simulink and the given parameters are applied to the model. During the simulation, both the cases of balanced three-phase load and unbalanced three-phase load in the system are considered. The zero-sequence currents of each line before the fault and after the fault are collected respectively, and the difference is taken to obtain the zero-sequence current variation before and after the fault and calculate its phase magnitude. The results when the three phases are balanced are shown in Table 4; the results when the three phases are unbalanced are shown in Table 5.

[0166] Table 4 Phase of zero-sequence current variation of each line with balanced three-phase load and neutral grounded through an arc suppression coil

[0167]

[0168] Table 5 Phase of zero-sequence current variation of each line with unbalanced three-phase load and neutral grounded through an arc suppression coil

[0169]

[0170] By analyzing Table 4.4 and Table 4.5, it is concluded that the unbalance of the three phases has little effect on the zero-sequence current variation of each line before and after the fault. The phase of the zero-sequence current variation of Line 1 before and after the fault is different from that of the other three lines. By judging the phase magnitude, it is determined that Line 1 is the faulty line, which is consistent with the faulty line set in the simulation, verifying the effectiveness of the criterion under the mode of neutral grounded through an arc suppression coil.

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

[0172] To explore the influence of different cable parameters on the criterion, different cables are set to have faults for comparison. Figure 10 Switch S1 is opened, the neutral point is not grounded, a fault is set to occur on Line 3 (the longest line), and the calculation method is the same as described above. The results are shown in Table 6. Figure 10The middle switch S1 is closed, and the neutral point is grounded through an arc suppression coil. Assume that a fault occurs on line 3, and the results are shown in Table 7.

[0173] Table 6 Phase of the zero-sequence current change of each line for the longest line fault with ungrounded neutral point

[0174]

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

[0176]

[0177] By analyzing Table 6 and Table 7, it can be obtained that the phase of the zero-sequence current change before and after the fault on line 3 is different from that of the other three lines. By judging the phase magnitude, it is determined that line 3 is the fault line, which is consistent with the fault line set in the simulation, verifying the effectiveness of the criterion when faults occur in different lines with different parameters.

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

[0179] for ungrounded neutral system

[0180] When the neutral point is ungrounded, the three-phase load is in a balanced state, and the resistance R of each phase of each line is 1000Ω. At the same time, assume that a grounding fault occurs on line 1. According to the above data, the zero-sequence current changes of the four lines before and after the fault are input into the Holmes-Duffing oscillator system for simulation verification, and the simulation results are obtained as follows Figure 11 as follows.

[0181] By comparing the four phase diagrams, it is found that the output phase diagram with the signal of line 1 added is in a chaotic state, while the output phase diagrams with the signals of the other three lines added are in a periodic state. There is an obvious difference between the output phase diagram of line 1 and the output phase diagrams of the other three lines. According to the theory proposed in Chapter 2, it can be judged that line 1 has a high-resistance grounding fault, which is consistent with the fault line set in the simulation and conforms to the line selection strategy proposed in this embodiment.

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

[0183] The parameters of the simulation model remain unchanged, and the parameters of the Holmes-Duffing oscillator system remain unchanged. Still assume that a single-phase grounding fault occurs on line 1, and only the neutral point of the simulation model is grounded through an arc suppression coil, adopting an over-compensation method. The over-compensation degree is generally in the range of 0-10%. According to it can be calculated that the magnitude of the grounding inductance should be 13.26H ≤ L ≤ 14.6H. In this embodiment, the grounding inductance L = 13.5H is taken during simulation. The signals of the four lines are input into the Holmes-Duffing oscillator system, and its output phase diagram is as followsFigure 12 as shown

[0184] Comparing Figure 12 the four phase diagrams in [reference], it can be concluded that: the output phase diagram of the signal added to line 1 is in a chaotic state, and the other three lines are in a periodic state. There is an obvious difference in the signal output phase diagram states between line 1 and the other three lines, which conforms to the theory mentioned in Chapter 2, verifying the effectiveness of the line selection strategy proposed in this embodiment. It can be judged that the single-phase high-resistance grounding fault on 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 grounded system is verified through simulation.

[0185] Considering the influence of unbalanced three-phase loads in the system

[0186] In the adaptability analysis in Chapter 1, through formula derivation and theoretical analysis, it has been obtained that unbalanced three-phase loads will not affect the line selection strategy proposed in this embodiment. In this section, the theoretical analysis will be verified by simulation. The unbalanced situation of the loads is shown in Table 8. When the three-phase loads are unbalanced, two working conditions of ungrounded neutral point and neutral point grounded through an arc suppression coil are simulated and verified. The phase diagrams output by the Duffing oscillator system are as Figure 13 and Figure 14 shown.

[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 unbalanced three-phase loads, it can still be judged that line 1 is the faulty line, which is consistent with the faulty line set in the simulation. The faulty lines selected under the two grounding methods are consistent with the faulty lines 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 loads are unbalanced.

[0191] Considering the influence of different cable parameters

[0192] All the above simulation verifications are for line 1 to have a fault, and line 1 happens to be the shortest line. In this section, it will be verified whether the line selection strategy proposed in this embodiment can be distinguished through the output phase diagram when the longest line has a fault. When a high-resistance grounding fault occurs on line 3 under the condition of balanced three-phase loads, the change amounts of zero-sequence currents before and after the fault of the four lines are input into the Duffing oscillator system under the working conditions of ungrounded neutral point and neutral point grounded through an arc suppression coil. The output phase diagrams are as Figure 15 and Figure 16 shown.

[0193] Comparison Figure 15 and Figure 16 Among the four phase diagrams in, it is obvious that: the phase diagrams with the signal output of line 3 added are all in a chaotic state, and the other three lines are in a periodic state. It can be judged that a single-phase high-resistance grounding fault has occurred on line 3, which is consistent with the fault line set in the simulation, verifying the effectiveness of the strategy proposed in this embodiment.

[0194] This embodiment proposes a method for identifying the faulty line of non-effective grounding faults in mine cables based on the fusion of SSIA and small-signal detection of Holmes-Duffing oscillators. After verification by actual system examples, the following conclusions are obtained:

[0195] It can be seen from the SSIA analysis that the phase and amplitude of the zero-sequence current variation of the faulty line are different from those of the non-faulty line, and the zero-sequence current variations of the non-faulty lines are the same; the phase of the zero-sequence current variation of the faulty line is the same as the phase of the fault-to-ground voltage of the faulty line. The above conclusions are verified by simulation.

[0196] This embodiment proposes a method for identifying the faulty line of non-effective grounding faults in mine cables based on the fusion of SSIA and small-signal detection of Holmes-Duffing oscillators. 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 faulty line is identified by judging the chaotic relationship of the phase diagrams of each line. Through example analysis, the effectiveness and applicability of the proposed method are verified. For the faulty line selection of the non-effective grounding system, in the future, further consider the influence of the magnitude of the grounding impedance on the line selection criterion, and then determine the range of grounding impedance applicable to this method.

[0197] Embodiment 2

[0198] This embodiment provides a system for selecting the faulty line of high-resistance grounding faults in mine cables of a coal mine power grid, including:

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

[0200] A zero-sequence current variation determination module, configured to determine the zero-sequence current variations 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] A zero-sequence current variation signal detection module, configured to perform signal detection using the oscillator chaotic system based on the zero-sequence current variations of each line before and after the fault to obtain the output phase diagrams of different lines;

[0202] A faulty line selection module, configured to select the faulty line according to the states of the output phase diagrams of different lines to determine the faulty line.

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

[0204] In the above embodiments, the descriptions of each embodiment have their own emphases. For parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

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

[0206] Embodiment Three

[0207] 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 method for selecting a high-resistance grounding fault line of a mine-used cable in a coal mine power grid as described in the first embodiment above.

[0208] Embodiment Four

[0209] 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, it implements the steps in a method for selecting a high-resistance grounding fault line of a mine-used cable in a coal mine power grid as described in the first embodiment above.

[0210] Embodiment Five

[0211] This embodiment provides a computer program product or a computer program. The computer program product or the computer program includes computer instructions, and the computer instructions are 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, so that the computer device executes the steps in a method for selecting a high-resistance grounding fault line of a mine-used cable in a coal mine power grid as described in the first embodiment above.

[0212] 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 a hardware embodiment, 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.

[0213] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to 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 means for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple 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 device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including instruction means, and the instruction means implements the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0215] 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, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0216] Those of ordinary skill in the art can understand that all or part of the processes of implementing the above-described embodiment methods 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 above-described method embodiments. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0217] Although the specific implementation manners of the present invention have been described above in conjunction with the accompanying drawings, they do not limit the protection scope of the present invention. Those skilled in the art should understand that based on the technical solutions of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A method for selecting a line for a high-resistance grounding fault of a mining cable in a coal mine power grid, 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; According to the difference of the zero-sequence current vector of each line before and after the fault, the change of the zero-sequence current of each line before and after the fault is determined; Based on the change of zero-sequence current of each line before and after the fault, the oscillator chaotic system is used for signal detection to obtain the output phase diagram of different lines. The fault line is selected according to the status of the output phase diagrams of different lines to determine the faulty line.

2. A method for selecting a high-resistance grounding fault line for a coal mine power grid mining cable as claimed in claim 1, characterized in that: The difference between the zero-sequence current vectors of each line before and after the fault is used to determine the change in zero-sequence current of each line before and after the fault, specifically: In the formula, is the zero-sequence current vector after the nth cycle fault, is the zero-sequence current vector before the fault in the first two cycles of the nth cycle, It is the change of zero-sequence current of each line before and after the fault.

3. A method for selecting a high-resistance grounding fault line for a coal mine power grid mining cable as claimed in claim 1, characterized in that: Based on the change in zero-sequence current of each line before and after the fault, the oscillator chaotic system is used to perform signal detection to obtain the output phase diagram of different lines, which is 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 signal of the zero-sequence current change of each line before and after the fault. Get the output phase diagram of different circuits.

4. A method for selecting a high-resistance grounding fault line for a coal mine power grid mining cable as claimed in claim 1, characterized in that: The fault line selection is performed according to the state of the output phase diagrams of different lines to determine the fault line, specifically: Get output phase diagrams of different circuits; 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, it is determined that the certain line is a faulty line and all other lines are non-faulty lines.

5. A method for selecting a high-resistance grounding fault line for a coal mine power grid mining cable as claimed in claim 4, characterized in that: The states of the output phase diagrams of the different circuits include two situations, specifically: One case 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 situation is that the output phase diagram of the fault line is in a wonton state, while the output phase diagram of the non-fault line is in a periodic state.

6. A method for selecting a high-resistance grounding fault line for a coal mine power grid mining cable as claimed 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.

7. A coal mine power grid mining cable high resistance grounding fault line selection system, characterized in that: include: A 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; 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 of the zero-sequence current vector of each line before and after the fault; The zero-sequence current variation signal detection module is configured to perform signal detection using an oscillator chaotic system based on the zero-sequence current variation of each line before and after the fault, and obtain output phase diagrams of different lines; The fault line selection module is configured to perform fault line selection according to the states of the output phase diagrams of different lines and determine the faulty line.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps in a method for selecting a high-resistance grounding fault line for a coal mine power grid mining cable are implemented as described in any one of claims 1-6.

9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps in the method for selecting a high-resistance grounding fault line for a coal mine power grid mining cable are implemented as described in any one of claims 1-6.

10. A computer program product, characterized in that The computer program product includes a computer program, and when the computer program is executed by a processor, the steps in the method for selecting a high-resistance grounding fault line for a coal mine power grid mining cable are implemented as described in any one of claims 1-6.

Images