Phase selection method, system and medium for single-phase grounding fault

Abstract

The present invention relates to a phase selection method, system and medium for single-phase grounding fault, and the method includes the following steps: establishing a surface magnetic field sensing model of a three-core cable, setting measuring points of an annular magnetoresistance array; obtaining a rotation angle by inverting the formula of the six measuring points of the annular magnetoresistance array; determining the planar relative arrangement of the annular magnetoresistance array and the three-phase conductors A, B and C according to the rotation angle; and accurately distinguishing the fault phase based on the difference in the peak-to-peak value of the magnetic flux density at the six measuring points during transient time. The present invention starts from the actual needs of phase selection for single-phase grounding faults of three-core cables in distribution networks, combines existing theoretical foundations and detection technologies, and is oriented towards actual working conditions and distributed online monitoring scenarios. By utilizing the annular magnetoresistance array sensing technology, a phase selection method for single-phase grounding faults of three-core cables based on the peak-to-peak value of the surface magnetic field is proposed, which accurately identifies the fault phase at the transient moment when a single-phase grounding fault occurs, and provides strong support for rapid fault removal and post-fault analysis and judgment in the power system.

Description

Technical Field

[0001] The present invention relates to the field of distribution network fault diagnosis, and in particular to a single-phase grounding fault phase selection method, system and medium. Background Art

[0002] Three-core cables are widely used in modern 10 kV distribution systems, with their usage growing at an average annual rate exceeding 10% in recent years. Single-phase ground faults are one of the most common fault types in medium-voltage cables, accounting for approximately 70% of all distribution network faults. Accurately identifying faults and rapidly restoring power are crucial, but traditional methods require invasive procedures at both ends of the cable, increasing maintenance workload and prolonging troubleshooting cycles. Therefore, there is an urgent need to develop more efficient and intelligent methods for identifying faulty phases to improve overall power supply system reliability. Summary of the Invention

[0003] The purpose of the embodiments of the present invention is to provide a single-phase grounding fault phase selection method, system and medium, which can accurately identify the faulty phase at the transient moment when a single-phase grounding fault occurs, and provide strong support for the rapid fault removal and post-fault analysis of the power system.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] In a first aspect, an embodiment of the present invention provides a phase selection method for a single-phase ground fault, comprising the following steps:

[0006] Establish a three-core cable surface magnetic field sensing model and set up annular magnetoresistive array measurement points;

[0007] The rotation angle is obtained by inverting the formula based on the six measurement points of the annular magnetoresistive array;

[0008] Determine the relative planar arrangement of the annular magnetic resistance array and the three-phase conductors A, B, and C according to the rotation angle;

[0009] The fault phase can be accurately identified based on the difference in peak-to-peak values ​​of the magnetic flux density at six measurement points during transient time.

[0010] The ring magnetoresistive array measurement points are specifically set as follows:

[0011] Six magnetoresistive sensors with a mutual difference of 60°, numbered S1 to S6, are used and placed at any position on the surface of the three-core cable.

[0012] In the three-core cable surface magnetic field sensing model, point O is the center of the three-core cable, points A, B, and C are the centers of the A, B, and C phase cores respectively, and the distances from point O to the centers of each core are r A 、r B 、r C , the radius of the cable is R, O is the centroid of triangle ABC, and from the trigonometric relationship we can get r A= r B = r C , the rotation angles between OA, OB, OC and the positive direction of the x-axis are , which differ by 120°. From the trigonometric relationship, we can get the coordinates of points A, B, and C respectively. , , .

[0013] In the three-core cable surface magnetic field sensing model, the magnetic flux density B generated at S1~S6 along the tangential direction n is S1 ~B S6 for:

[0014]

[0015]

[0016]

[0017]

[0018]

[0019] .

[0020] The rotation angle is obtained by inverting the formula of the six measurement points of the annular magnetoresistive array. Specifically, the rotation angles α, β, and γ are obtained by inverting the formula of the magnetic flux density at the six measurement points and the three-phase current waveform at the same time according to the magnetic flux density waveform at the six measurement points.

[0021] The formula for the magnetic flux density is as follows: the surface magnetic field of the three-core cable is calculated according to the Biot-Savart law, and the integral form is:

[0022]

[0023] Where B is the magnetic flux density vector, L is the integral path, I is the source current, dl is the tiny line element of the current, and e r is the unit vector of the current element pointing to the field point to be determined, r is the distance from the current element to the field point to be determined, and μ0 is the magnetic permeability of vacuum.

[0024] The specific method of accurately judging the fault phase based on the difference in peak-to-peak values ​​of the magnetic flux density at six measurement points during transient time is as follows:

[0025] Within one cycle after a single-phase grounding fault occurs, the apparent magnetic field of the three-core cable undergoes a transient change. The magnitude of the magnetic flux density at the six measurement points changes to different degrees during the transient time. The concept of peak-to-peak value of the magnetic flux density at each measurement point is introduced:

[0026]

[0027] Where i = 1, 2, …, 6; is the peak-to-peak value of transient magnetic flux density at the Si measurement point, is the maximum transient magnetic flux density at the Si measurement point, is the minimum value of transient magnetic flux density at the Si measurement point,

[0028] Based on the magnetic flux density data of six measurement points when single-phase grounding faults occur on phases A, B, and C respectively, and the relative position relationship between the three-phase conductors and the plane of the six measurement points of the annular magnetic resistance array, a fault identification diagram is drawn;

[0029] The phase selection and identification principle for single-phase grounding fault of three-core cable is established: under the condition of single-phase grounding fault, there is a direct correspondence between the measurement point with the largest peak-to-peak value of magnetic flux density and the fault phase, that is, the phase corresponding to the measurement point with the largest peak-to-peak value of magnetic flux density is the phase where the fault occurs.

[0030] In a second aspect, an embodiment of the present invention provides a single-phase ground fault phase selection system, comprising a memory and a processor, wherein the memory includes a program of a single-phase ground fault phase selection method, and when the program of the single-phase ground fault phase selection method is executed by the processor, the following steps are implemented:

[0031] Establish a three-core cable surface magnetic field sensing model and set up annular magnetoresistive array measurement points;

[0032] The rotation angle is obtained by inverting the formula based on the six measurement points of the annular magnetoresistive array;

[0033] Determine the relative planar arrangement of the annular magnetic resistance array and the three-phase conductors A, B, and C according to the rotation angle;

[0034] The fault phase can be accurately identified based on the difference in peak-to-peak values ​​of the magnetic flux density at six measurement points during transient time.

[0035] Specifically, the setting of the annular magnetoresistive array measurement points is to use six magnetoresistive sensors with a mutual difference of 60 degrees, numbered S1 to S6, and the magnetoresistive sensors are placed at any position on the surface of the three-core cable.

[0036] In the three-core cable surface magnetic field sensing model, point O is the center of the three-core cable, points A, B, and C are the centers of the A, B, and C phase cores respectively, and the distances from point O to the centers of each core are r A 、r B 、r C , the radius of the cable is R, O is the centroid of triangle ABC, and from the trigonometric relationship we can get r A = r B = r C , the rotation angles between OA, OB, OC and the positive direction of the x-axis are , which differ by 120°. From the trigonometric relationship, we can get the coordinates of points A, B, and C respectively. , , .

[0037] In a third aspect, an embodiment of the present invention provides a computer-readable storage medium storing program code. When the program code is executed by a processor, the steps of the single-phase grounding fault phase selection method described above are implemented.

[0038] In a fourth aspect, an embodiment of the present invention provides an electronic device, including:

[0039] Memory for storing computer programs;

[0040] The processor is configured to execute the steps of the single-phase grounding fault phase selection method described above when executing the computer program stored in the memory.

[0041] Compared with existing technologies, the present invention offers the following advantages: It addresses the practical needs of phase selection for single-phase grounding faults in three-core cables in distribution networks, combines existing theoretical foundations and detection technologies, and addresses practical operating conditions and distributed online monitoring scenarios. Leveraging annular magnetoresistive array sensing technology, a phase selection method for single-phase grounding faults in three-core cables based on peak-to-peak surface magnetic field is proposed. This method accurately identifies the faulty phase at the moment of a single-phase grounding fault, providing strong support for rapid fault removal and post-fault analysis in power systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 is a flow chart of the method of the present invention;

[0044] Figure 2 This is a schematic diagram of single-phase grounding of a three-core cable according to the present invention;

[0045] Figure 3 This is a diagram of a three-core cable surface magnetic field sensing model of the present invention;

[0046] Figure 4 It is a distribution network model diagram of the present invention;

[0047] Figure 5 is a steady-state magnetic field diagram of the present invention;

[0048] Figure 6is a steady-state three-phase current diagram of the present invention;

[0049] Figure 7 This is the A-phase ground fault magnetic field diagram of the present invention;

[0050] Figure 8 This is the peak-to-peak diagram of the magnetic flux density of S1 to S6 of the present invention;

[0051] Figure 9 Schematic diagram of peak-to-peak value of magnetic flux density at single-phase grounding measurement point of the present invention;

[0052] Figure 10 This is a peak-to-peak diagram of the magnetic flux density at different rotation angles of the present invention. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0054] The terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0055] The terms "first," "second," etc. are only used to distinguish one entity or operation from another entity or operation, and are not to be understood as indicating or implying relative importance, nor are they to be understood as requiring or implying any actual relationship or order between these entities or operations.

[0056] An embodiment of the present invention provides a phase selection method for a single-phase ground fault, comprising the following steps:

[0057] Establish a three-core cable surface magnetic field sensing model and set up annular magnetoresistive array measurement points;

[0058] The rotation angle is obtained by inverting the formula based on the six measurement points of the annular magnetoresistive array;

[0059] Determine the relative planar arrangement of the annular magnetic resistance array and the three-phase conductors A, B, and C according to the rotation angle;

[0060] The fault phase can be accurately identified based on the difference in peak-to-peak values ​​of the magnetic flux density at six measurement points during transient time.

[0061] This invention proposes to use a circular magnetoresistive sensor array consisting of six magnetoresistive sensors offset by 60° to achieve phase selection for single-phase ground faults in three-core cables. The surface magnetic flux density of a three-core cable exhibits a physical property of decaying with distance. The spatial distance between the six measurement points and the faulty phase conductor is correlated with the measured magnetic flux density. When a single-phase ground fault occurs in a three-core cable, the point closest to the faulty phase among the six measurement points surrounding the cable will have the highest peak-to-peak magnetic flux density, thereby enabling identification of the faulty phase.

[0062] The process of this technical solution is as follows Figure 1 As shown in the figure, when the system is in steady state, the rotation angle is obtained by inverting the formula based on the six measurement points of the annular reluctance array. This rotation angle is then used to determine the relative planar arrangement of the annular reluctance array and the three-phase conductors A, B, and C. When a single-phase ground fault occurs in the system, the faulty phase is accurately identified based on the difference in peak-to-peak magnetic flux density at the six measurement points during the transient time.

[0063] A single-phase grounding fault in a three-core cable Figure 2 As shown in the figure, a ground loop is formed between the single-phase conductor and the ground, and the cable XLPE layer to the outer sheath layer is broken down, resulting in the formation of a through discharge channel between the fault phase conductor and the ground.

[0064] The surface magnetic field calculation of the three-core cable obeys the Biot-Savart law, and the integral form is:

[0065]

[0066] Where B is the magnetic flux density vector, L is the integral path, I is the source current, dl is the tiny line element of the current, and e r is the unit vector of the current element pointing to the field point to be determined, r is the distance from the current element to the field point to be determined, and μ0 is the magnetic permeability of vacuum.

[0067] The composite magnetic field generated by the three-phase conductors of a three-core cable can be expressed as

[0068]

[0069] Where B A (r,θ),B B (r,θ),B C (r, θ) are the magnetic field components generated by the three-phase conductors A, B, and C at the measuring point (r, θ).

[0070] For the magnetic field at any measuring point (r,θ) of a circular conductor, the integral expression in the polar coordinate system is:

[0071]

[0072] When a single-phase ground fault occurs in a three-core cable, the current in the faulted phase undergoes a significant sudden change, causing a distortion in the resulting magnetic field distribution. The resulting magnetic field amplitude increases significantly in the faulted phase, far exceeding that in the direction of the other healthy phases. Simultaneously, the originally uniformly distributed rotating magnetic field becomes non-uniform, exhibiting a characteristic shift toward the faulted phase.

[0073] Assume that a single-phase ground fault occurs on phase A, I f is the fault current amplitude, ψ f Fault current phase angle. The fault current is

[0074]

[0075] Under the far-field approximation condition, the magnetic field component of the fault phase A is

[0076]

[0077] The analysis results show that when a single-phase grounding fault occurs in a three-core cable, the magnetic field mutation characteristics of the fault phase are most significant. By measuring the magnetic field changes at different angles on the surface of the three-core cable, the fault phase can be effectively identified.

[0078] 2) Ring magnetoresistive array and surface magnetic field formula

[0079] The present invention uses six magnetoresistive sensors with a mutual difference of 60 degrees, numbered S1 to S6, which are placed at any position on the surface of the three-core cable and do not need to be installed on the extension line of the line connecting the cable center and the phase center. Figure 3 As shown, point O is the center of the three-core cable, points A, B, and C are the centers of the phase A, B, and C cores respectively, and the distances from point O to the centers of the cores are r A 、r B 、r C , the radius of the cable is R. O is the centroid of triangle ABC, and from the trigonometric relationship we can get r A = r B = r C The rotation angles between OA, OB, OC and the positive direction of the x-axis are , with a difference of 120°. From the trigonometric relationship, we can get the coordinates of points A, B, and C respectively. , , .

[0080] The magnetic flux density B is generated along the tangential direction n at S1~S6 S1 ~B S6 for:

[0081]

[0082]

[0083]

[0084]

[0085]

[0086]

[0087] 3) Phase selection for single-phase grounding fault of three-core cable

[0088] Build a distribution network system model in Matlab / Simulink. The model is as follows Figure 4 In the equation shown, the system has one busbar and six feeders. The six feeders include overhead lines, cable lines, and overhead-cable lines. Feeder L1 consists of a cable line with a length of 4 km; feeder L2 consists of an overhead line with a length of 12 km; feeder L3 consists of an overhead line with a length of 15 km; feeder L4 consists of an overhead line and cable line with a length of 12 km and a length of 5 km; feeder L5 consists of an overhead line with a length of 10 km; and feeder L6 consists of a cable line with a length of 3 km. The power module in the model uses a three-phase power supply with a voltage level of 110 kV and a frequency of 50 Hz. The transformer has a transformation ratio of 110 kV / 10 kV and a Y / △ connection. The primary side is connected to the 110 kV busbar and the secondary side is connected to the 10 kV busbar. A single-phase ground fault occurred on feeder L1. The parameters of the overhead line and cable lines are shown in Table 1. The dimensions and geometric parameters of each layer of the three-core cable are shown in Table 2.

[0089] Table 1 Parameters of overhead lines and cables

[0090]

[0091] Table 2 Geometric dimensions of three-core cables

[0092]

[0093] ① Steady-state inversion rotation angle

[0094] Considering the symmetry of the cable core geometry, the distance r from the cable center O to the centers of the three-phase cores A, B, and C is A 、r B 、r C The rotation angles α, β, and γ between OA, OB, and OC and the positive direction of the x-axis differ by 120°. A = r B = r C =21mm, the rotation angles α, β, and γ are 270°, 150°, and 30° respectively, and the cable radius R is 46.3mm.

[0095] Based on the differential evolution algorithm, the three-phase current I A , I B , I C and surface magnetic induction intensity B S1 ~B S6 The steady-state magnetic field waveforms at the six measurement points are as follows: Figure 5 As shown, the three-phase current is Figure 6 shown.

[0096] according to Figure 5 and Figure 6 The magnetic flux density waveforms at the six measurement points and the three-phase current waveforms at the same time can be inverted based on the formula of the magnetic flux density at the six measurement points to obtain the angles of the three parameters α, β, and γ. The inverted rotation angles are shown in Table 3.

[0097] Table 3 shows that the absolute errors of the inverted values ​​for α, β, and γ are 0.32°, 0.84°, and 0.28°, respectively. The relative errors for the three rotation angles α, β, and γ are all less than 1%. The relative errors of the rotation angles inverted using the differential evolution algorithm are less than 1%, meeting the requirements for practical engineering applications.

[0098] The rotation angle obtained by steady-state inversion can be used to determine the planar relative position distribution of the three-phase conductors in the three-core cable and the six measurement points of the annular magnetoresistive array.

[0099] Table 3 Rotation angle inversion

[0100]

[0101] ② Single-phase grounding transient phase selection

[0102] For example, a neutral point ungrounded system has a metallic single-phase grounding fault on phase A of feeder L1. The fault time is set to 0.25s. The surface magnetic flux density waveform of feeder L1 is as follows: Figure 7 As shown, the rotation angles are set to 270°, 150°, and 30° respectively.

[0103] Depend on Figure 7 Analysis shows that within one cycle after a single-phase ground fault occurs at 0.025s, the apparent magnetic field of the three-core cable undergoes a transient change. The magnitude of the magnetic flux density at the six measurement points changes to different degrees during the transient time. Therefore, the concept of peak-to-peak value of the magnetic flux density at each measurement point is introduced:

[0104]

[0105] Where i = 1, 2, …, 6; Bpp Si is the peak-to-peak value of the transient magnetic flux density at the Si measurement point, Bmax Si is the maximum value of the transient magnetic flux density at the Si measurement point, and Bmin Si is the minimum value of the transient magnetic flux density at the Si measurement point.

[0106] When a single-phase grounding fault occurs on phases A, B, and C, the peak-to-peak values ​​of the magnetic flux density at the six measurement points are as follows: Figure 8 Analysis shows that when a single-phase grounding fault occurs in each phase, there is always one measurement point with the highest peak-to-peak value of magnetic flux density among the six measurement points.

[0107] According to the magnetic flux density data of six measuring points when single-phase grounding faults occur in phases A, B, and C respectively, combined with the relative position relationship between the three-phase conductor and the plane of the six measuring points of the annular magnetic resistance array, the following graph is drawn: Figure 9 The fault identification diagram is shown in the figure. Detailed analysis shows that:

[0108] When a single-phase ground fault occurs on phase A, the peak-to-peak value of the magnetic flux density recorded at measurement point S4 is significantly higher than that at other measurement points, demonstrating a clear amplitude advantage. Specifically, during a ground fault on phase A, the peak-to-peak value of the magnetic flux density at measurement point S4 can reach 3-5 times that of normal operation. This significant change provides reliable evidence for accurate identification of the faulted phase. Similarly, when a single-phase ground fault occurs on phase B, the peak-to-peak value of the magnetic flux density at measurement point S2 reaches its maximum value, significantly higher than that at other measurement points. Under this condition, the magnetic flux density distribution at measurement point S2 exhibits a characteristic pattern that is highly correlated with the faulted phase, phase B. When a single-phase ground fault occurs on phase C, the peak-to-peak value of the magnetic flux density at measurement point S6 is the highest, a phenomenon that fully corresponds to the two aforementioned scenarios. The data shows that the rate of change in the magnetic flux density at point S6 is most dramatic when phase C is grounded, providing clear guidance for phase selection.

[0109] Combining the above observations and theoretical analysis, a principle for phase selection and identification of single-phase grounding faults in three-core cables has been established: Under single-phase grounding fault conditions, the measurement point with the highest peak-to-peak magnetic flux density directly corresponds to the faulty phase. That is, the phase corresponding to the measurement point with the highest peak-to-peak magnetic flux density is the faulty phase. This principle provides a theoretical basis and technical support for quickly and accurately determining the faulty phase in practical engineering applications, effectively improving the efficiency and reliability of power system fault diagnosis.

[0110] Different rotation angles directly affect the peak-to-peak distribution of the magnetic flux density detected at the six measurement points. This influence is primarily due to the change in the relative position between the three-phase conductors and the measurement points of the annular reluctance array, which alters the magnetic field distribution pattern. At certain rotation angles, two or more measurement points may simultaneously detect similar or even identical maximum peak-to-peak magnetic flux density values. This can lead to ambiguity in fault phase determination and, in turn, incorrect phase selection.

[0111] To eliminate this problem, the following verification scheme was developed. The specific operation was as follows: taking the single-phase grounding fault of phase A as the benchmark condition, the rotation angle α was used as a variable parameter, gradually increasing from 0° to 360°, and using a very small step size of 0.1° for angle increment to ensure the acquisition of high-precision continuous data. At each angle, the peak-to-peak value of the magnetic flux density at six measurement points was recorded simultaneously and plotted as follows: Figure 10 The complete peak-to-peak variation range is shown.

[0112] When α∈[240.1°,300°], the peak-to-peak value Bpp S1 of the magnetic flux density of S1 is greater than the peak-to-peak value of the magnetic flux density of the other measurement points, and at α=270°, Bpp S1 reaches its maximum; when α∈[300.1°,0°], the peak-to-peak value BppS2 of the magnetic flux density of S2 is greater than the peak-to-peak value of the magnetic flux density of the other measurement points, and at α=330°, Bpp S2 reaches its maximum; when α belongs to [0.1°,60°], the peak-to-peak value Bpp S3 of the magnetic flux density of S3 is greater than the peak-to-peak value of the magnetic flux density of the other measurement points, and at α=30°, BppS3 reaches its maximum; when α belongs to [60.1°,120°], the peak-to-peak value Bpp S4 of the magnetic flux density of S4 is greater than the peak-to-peak value of the magnetic flux density of the other measurement points, and at α=90°, Bpp S4 reaches its maximum; when α belongs to [120.1°, 180°], the peak-to-peak value Bpp S5 of the magnetic flux density of S5 is greater than the peak-to-peak value of the magnetic flux density of the other measurement points, and when α=150°, Bpp S5 reaches its maximum; when α belongs to [180.1°, 240°], the peak-to-peak value Bpp S6 of the magnetic flux density of S6 is greater than the peak-to-peak value of the magnetic flux density of the other measurement points, and when α=210°, Bpp S6 reaches its maximum.

[0113] Analysis shows that during the continuous change of the rotation angle α∈[0°,360°], the peak-to-peak value of the magnetic induction intensity Bpp Si at the measurement points S1~S6 presents a periodic distribution characteristic. For any measurement point Si, there is an interval [θ i1 ,θ i2 ]∈[0°,360°], so that the peak-to-peak value of the magnetic induction intensity at the measurement point in this interval satisfies

[0114]

[0115] In the formula, i≠j, i=1, 2, …, 6; ∀α∈[θ i1 ,θ i2 ].

[0116] The analysis of the rotation angle shows that when a single-phase grounding fault occurs in a three-core cable, different rotation angles have no effect on this phase selection method.

[0117] An embodiment of the present invention provides a single-phase grounding fault phase selection system, including a memory and a processor. The memory includes a program of a single-phase grounding fault phase selection method. When the program of the single-phase grounding fault phase selection method is executed by the processor, the steps of the single-phase grounding fault phase selection method as described above are implemented.

[0118] An embodiment of the present invention provides a computer-readable storage medium storing program code. When the program code is executed by a processor, the steps of the single-phase grounding fault phase selection method described above are implemented.

[0119] An embodiment of the present invention provides an electronic device, including:

[0120] Memory for storing computer programs;

[0121] The processor is configured to execute the steps of the single-phase grounding fault phase selection method described above when executing the computer program stored in the memory.

[0122] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0123] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0124] These computer program instructions may 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 produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0125] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0126] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0127] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0128] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can be implemented using any method or technology to store information. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change RAM (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media such as modulated data signals and carrier waves.

[0129] The foregoing description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A phase selection method for a single-phase grounding fault, characterized in that: The following steps are involved: Establish a three-core cable surface magnetic field sensing model and set up annular magnetoresistive array measurement points; The rotation angle is obtained by inverting the formula based on the six measurement points of the annular magnetoresistive array; Determine the relative planar arrangement of the annular magnetic resistance array and the three-phase conductors A, B, and C according to the rotation angle; Accurately identify the fault phase based on the difference in peak-to-peak values ​​of the magnetic flux density at six measurement points during transient time; The method of accurately judging the fault phase based on the difference in peak-to-peak values ​​of the magnetic flux density at six measurement points during transient time is specifically as follows: Within one cycle after a single-phase grounding fault occurs, the apparent magnetic field of the three-core cable undergoes a transient change. The magnitude of the magnetic flux density at the six measurement points changes to different degrees during the transient time. The concept of peak-to-peak value of the magnetic flux density at each measurement point is introduced: ， Where i = 1, 2, …, 6; is the peak-to-peak value of transient magnetic flux density at the Si measurement point, is the maximum transient magnetic flux density at the Si measurement point, is the minimum value of transient magnetic flux density at the Si measurement point, Based on the magnetic flux density data of six measurement points when single-phase grounding faults occur on phases A, B, and C respectively, and the relative position relationship between the three-phase conductors and the plane of the six measurement points of the annular magnetic resistance array, a fault identification diagram is drawn; The phase selection and identification principle for single-phase grounding fault of three-core cable is established: under the condition of single-phase grounding fault, there is a direct correspondence between the measurement point with the largest peak-to-peak value of magnetic flux density and the fault phase, that is, the phase corresponding to the measurement point with the largest peak-to-peak value of magnetic flux density is the phase where the fault occurs.

2. A single-phase ground fault phase selection method according to claim 1, characterized in that: The specific setting of the annular magnetoresistive array measurement points is as follows: Six magnetoresistive sensors with a mutual difference of 60°, numbered S1 to S6, are used and placed at any position on the surface of the three-core cable.

3. A single-phase ground fault phase selection method according to claim 2, characterized in that: In the three-core cable surface magnetic field sensing model, point O is the center of the three-core cable, points A, B, and C are the centers of the A, B, and C phase cores respectively, and the distances from point O to the centers of each core are r A 、r B 、r C , the radius of the cable is R, O is the centroid of triangle ABC, and from the trigonometric relationship we can get r A = r B =r C , the rotation angles between OA, OB, OC and the positive direction of the x-axis are , which differ by 120°. From the trigonometric relationship, we can get the coordinates of points A, B, and C respectively. , , .

4. A single-phase ground fault phase selection method according to claim 3, characterized in that: In the three-core cable surface magnetic field sensing model, the magnetic flux density B generated at S1~S6 along the tangential direction n is S1 ~B S6 for: ， ， ， ， ， 。 5. A phase selection method for a single-phase grounding fault according to claim 4, characterized in that: The rotation angle is obtained by inverting the formula of the six measurement points of the annular magnetoresistive array. Specifically, the rotation angles α, β, and γ are obtained by inverting the formula of the magnetic flux density at the six measurement points and the three-phase current waveform at the same time according to the magnetic flux density waveform at the six measurement points.

6. A phase selection method for a single-phase grounding fault according to claim 5, characterized in that: The formula for the magnetic flux density is as follows: the surface magnetic field of the three-core cable is calculated according to the Biot-Savart law, and the integral form is: ， Where B is the magnetic flux density vector, L is the integration path, I is the source current, dl is the tiny line element of the current, and e r is the unit vector of the current element pointing to the field point to be determined, r is the distance from the current element to the field point to be determined, and μ0 is the magnetic permeability of vacuum.

7. A single-phase ground fault phase selection system for implementing the method according to any one of claims 1 to 6, characterized in that: The invention comprises a memory and a processor, wherein the memory comprises a program of a phase selection method for a single-phase grounding fault, and when the program of the phase selection method for a single-phase grounding fault is executed by the processor, the following steps are implemented: Establish a three-core cable surface magnetic field sensing model and set up annular magnetoresistive array measurement points; The rotation angle is obtained by inverting the formula based on the six measurement points of the annular magnetoresistive array; Determine the relative planar arrangement of the annular magnetic resistance array and the three-phase conductors A, B, and C according to the rotation angle; The fault phase can be accurately identified based on the difference in peak-to-peak values ​​of the magnetic flux density at six measurement points during transient time.

8. A single-phase ground fault phase selection system according to claim 7, characterized in that: Specifically, the setting of the annular magnetoresistive array measurement points is to use six magnetoresistive sensors with a mutual difference of 60 degrees, numbered S1 to S6, and the magnetoresistive sensors are placed at any position on the surface of the three-core cable.

9. The single-phase ground fault phase selection system according to claim 7, characterized in that: In the three-core cable surface magnetic field sensing model, point O is the center of the three-core cable, points A, B, and C are the centers of the A, B, and C phase cores respectively, and the distances from point O to the centers of each core are r A 、r B 、r C , the radius of the cable is R, O is the centroid of triangle ABC, and from the trigonometric relationship we can get r A = r B = r C , the rotation angles between OA, OB, OC and the positive direction of the x-axis are , which differ by 120°. From the trigonometric relationship, we can get the coordinates of points A, B, and C respectively. , , .

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores program code, and when the program code is executed by a processor, the steps of the single-phase grounding fault phase selection method according to any one of claims 1 to 6 are implemented.

11. An electronic device, characterized in that: include: Memory for storing computer programs; The processor is configured to execute the steps of the single-phase grounding fault phase selection method according to any one of claims 1 to 6 when executing the computer program stored in the memory.

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