Phase selection method, system and medium for high-resistance grounding fault in distribution network

Abstract

The present application relates to a phase selection method, system and medium for a high-resistance grounding fault in a distribution network. The method includes setting a resistor R1 between the neutral point of the distribution network and the ground; calculating the total ground capacitance and total ground conductance of the distribution network system when the distribution network is operating normally; calculating the fault transition conductance after a single-phase high-resistance grounding fault occurs in the distribution network; determining a zero-sequence admittance vector offset; adding preset margin values ​​to both ends of the zero-sequence admittance vector offset to obtain an offset interval of the zero-sequence admittance vector, and determining the phase spanned by the offset interval as the fault phase. The present application is not affected by the system operation mode, has strong transition resistance resistance, and improves the accuracy and robustness of grounding fault phase selection.

Description

Technical Field

[0001] The present application relates to the technical field of distribution network fault detection, and in particular to a phase selection method, system and medium for high-resistance grounding fault in a distribution network. Background Art

[0002] Arc suppression coils are widely used as neutral points in my country's urban medium-voltage distribution systems. As medium-voltage cable networks continue to expand, capacitive current to ground increases year by year, leading to insufficient coil capacity. Even after compensation, residual current remains high, making it ineffective in suppressing intermittent arc overvoltages. Current improvements include fault phase transfer technology and active control technologies based on power electronics or power electronic devices. However, these technologies rely on identifying the faulty phase, posing the risk of further impact due to phase selection failure.

[0003] Currently, the phase selection of ground fault in distribution network mainly relies on zero-sequence voltage or current signal, which is difficult to detect. The above high-resistance faults are greatly affected by the imbalance of the three-phase-to-ground parameters of the line, making it difficult to accurately identify the fault in its early stages. While injecting a resonant signal can effectively measure system parameters, it is easily affected by the system's damping resistance, causing the resonance point to shift, leading to failure in fault phase selection. Furthermore, the use of active inverters places high demands on device measurement accuracy and control, making their widespread application difficult. Therefore, current distribution network ground fault phase selection technologies have the following drawbacks:

[0004] (1) The protection method based on zero-sequence voltage or current signal requires real-time detection of the change in zero-sequence component. Most of my country's distribution networks belong to small current grounding systems, and the fault characteristics under high-resistance faults are not obvious. This method is greatly affected by the system operation mode and fault conditions: by setting the phase selection functions of the three phases of the line separately, comparing the minimum value between the selected phases as the fault phase selection criterion, it is greatly affected by the asymmetry. Under the influence of the inherent zero-sequence voltage, the difference between the phase selection functions is close, which can easily lead to misjudgment.

[0005] (2) The protection method based on active control requires phase injection to control the zero-sequence voltage or current changes, relies on active control devices, and requires at least three phase controls on the neutral point, which places high demands on the measurement accuracy of the device and the control of the active inverter device. Summary of the Invention

[0006] The purpose of the embodiments of the present application is to provide a phase selection method, system and medium for high-resistance grounding faults in a distribution network, which can determine the phase where the distribution network fault occurs under different fault conditions, is not affected by the system operation mode, and has strong resistance to transition resistance, and can improve the accuracy and robustness of the phase selection for grounding faults in the distribution network.

[0007] To achieve the above objectives, this application provides the following technical solutions:

[0008] In a first aspect, an embodiment of the present application provides a phase selection method for a high-resistance ground fault in a distribution network, comprising the following steps:

[0009] During normal operation of the distribution network, the zero-sequence voltage at the neutral point before and after the resistor R1 is connected to the neutral point is measured, and the total capacitance to ground and the total conductance to ground of the distribution network system are calculated based on the geometric relationship of the zero-sequence admittance vector offset; wherein the resistor R1 is set between the neutral point of the distribution network and the ground;

[0010] After a single-phase high-resistance grounding fault occurs in the distribution network, the zero-sequence voltage of the neutral point is measured before and after the resistor R1 is connected to the neutral point, and the fault transition conductance is calculated based on the geometric relationship of the zero-sequence admittance vector offset;

[0011] The zero-sequence admittance vector offset is determined based on the zero-sequence voltage of the neutral point when the distribution network is operating normally and when a single-phase high-resistance ground fault occurs and before the resistor R1 is connected, as well as the total ground capacitance, total ground conductance and fault transition conductance of the distribution network system.

[0012] A preset margin value is added to both ends of the zero-sequence admittance vector offset to obtain an offset interval of the zero-sequence admittance vector, and the phase spanned by the offset interval is determined as the fault phase.

[0013] The resistor R1 is provided with a switch, and one resistor R1 is provided.

[0014] In the step of calculating the total capacitance to ground and the total conductance to ground of the distribution network system according to the geometric relationship of the zero-sequence admittance vector offset, the total capacitance to ground of the distribution network system is calculated specifically as follows:

[0015] ,

[0016] Where, is the total ground capacitance of the distribution network system, is the conductance of resistor R1, is the system power frequency, is the phase of the system’s total admittance to ground, is the phase of the system's total admittance to ground after resistor R1 is added;

[0017] The total ground conductance of the distribution network system is calculated as follows:

[0018] ,

[0019] Where, is the total ground conductance of the distribution network system, is the conductance of resistor R1, is the system power frequency, is the phase of the system’s total admittance to ground, It is the phase of the total admittance of the system to ground after adding resistor R1.

[0020] The phase and phase The calculation method is:

[0021] According to the zero-sequence voltage of the neutral point before and after the resistor R1 is connected to the neutral point during normal operation of the distribution network, the intermediate phase :

[0022] ,

[0023] Where, is the conductance of resistor R1, are the electromotive force of phases A, B, and C respectively, They are the relative admittances of feeder A, B, and C, and the total admittance of the system to ground The zero-sequence voltages before and after the neutral point are measured when the distribution network is operating normally and the resistor R1 is connected to the neutral point;

[0024] according to and 、 ,get , and then calculate the phase of the total system admittance to ground ; and according to and 、 ,get , and then calculate the phase :

[0025] ,

[0026] .

[0027] The fault transition conductance is calculated based on the geometric relationship of the zero-sequence admittance vector offset, which is expressed as:

[0028] ,

[0029] Where, is the total ground capacitance of the distribution network system, is the fault transition conductance, is the phase of the sum of the system's total ground admittance and the fault transition conductance, is the phase of the sum of the system's total ground admittance and the fault transition conductance after resistor R1 is added. is the conductance of resistor R1.

[0030] The phase and phase The calculation method is:

[0031] .

[0032] The method for determining the zero-sequence admittance vector offset is:

[0033] ,

[0034] Where, represents the electromotive force of the fault phase, Indicates the zero-sequence admittance vector offset during fault, To measure the zero-sequence voltage at the neutral point when the distribution network is operating normally and the resistor R1 is connected to the neutral point, is the total ground capacitance of the distribution network system, is the total earth conductance of the distribution network system, is the system power frequency, To measure the zero-sequence voltage before the neutral point when a single-phase high-resistance ground fault occurs in the distribution network and the resistor R1 is connected to the neutral point, is the fault transition conductance.

[0035] The preset margin value is added to both ends of the zero-sequence admittance vector offset to obtain the offset interval of the zero-sequence admittance vector, which is , is the preset margin value.

[0036] In a second aspect, an embodiment of the present application provides a phase selection system for a high-resistance ground fault in a distribution network, comprising:

[0037] The resistance setting module is used to set a resistor R1 with a switch between the neutral point of the distribution network and the ground;

[0038] The first calculation module is used to measure the zero-sequence voltage of the neutral point before and after the resistor R1 is connected to the neutral point when the distribution network is operating normally, and calculate the total capacitance to ground and the total conductance to ground of the distribution network system based on the geometric relationship of the zero-sequence admittance vector offset;

[0039] The second calculation module is used to measure the zero-sequence voltage of the neutral point before and after the resistor R1 is connected to the neutral point after a single-phase high-resistance grounding fault occurs in the distribution network, and calculate the fault transition conductance based on the geometric relationship of the zero-sequence admittance vector offset;

[0040] A zero-sequence admittance vector offset determination module is used to determine the zero-sequence admittance vector offset based on the zero-sequence voltage of the neutral point during normal operation of the distribution network and before the resistor R1 is connected, as well as the total ground capacitance, total ground conductance and fault transition conductance of the distribution network system;

[0041] The fault phase determination module is used to add a preset margin value to both ends of the zero-sequence admittance vector offset to obtain an offset interval of the zero-sequence admittance vector, and determine the phase spanned by the offset interval as the fault phase.

[0042] In the step of calculating the total ground capacitance and total ground conductance of the distribution network system according to the geometric relationship of the zero-sequence admittance vector offset by the first calculation module, the total ground capacitance of the distribution network system is calculated specifically as follows:

[0043] ,

[0044] Where, is the total ground capacitance of the distribution network system, is the conductance of resistor R1, is the system power frequency, is the phase of the system’s total admittance to ground, is the phase of the system's total admittance to ground after resistor R1 is added;

[0045] The total ground conductance of the distribution network system is calculated as follows:

[0046] ,

[0047] Where, is the total ground conductance of the distribution network system, is the conductance of resistor R1, is the system power frequency, is the phase of the system’s total admittance to ground, It is the phase of the total admittance of the system to ground after adding resistor R1.

[0048] The second calculation module calculates the fault transition conductance according to the geometric relationship of the zero-sequence admittance vector offset, which is expressed as:

[0049] ,

[0050] Where, is the total ground capacitance of the distribution network system, is the fault transition conductance, is the phase of the sum of the system's total ground admittance and the fault transition conductance, is the phase of the sum of the system's total ground admittance and the fault transition conductance after resistor R1 is added. is the conductance of resistor R1.

[0051] In a third aspect, an embodiment of the present application provides a computer-readable storage medium storing a program code. When the program code is executed by a processor, the steps of the method for phase selection of a high-resistance grounding fault in a distribution network as described above are implemented.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] (1) Fault analysis does not require multiple neutral point changes or calculation of three fault phase functions for comparison, and the fault phase selection criteria are simple.

[0054] (2) The zero-sequence admittance vector offset value is used for fault phase selection, which transforms the passive measurement fault characteristics into active structural fault characteristic changes.

[0055] (3) Distribution network fault phase selection does not require additional active grounding devices, and does not require multiple neutral point changes. Only one damping conductance needs to be switched on and off. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application 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 creative work.

[0057] Figure 1 This is a schematic diagram of a single-phase grounding fault in a low-current grounding system;

[0058] Figure 2 It is the zero-sequence admittance vector deviation diagram after the neutral point changes during normal operation;

[0059] Figure 3 It is the zero-sequence admittance vector offset diagram after the neutral point changes in the fault state. DETAILED DESCRIPTION

[0060] The technical solutions in the embodiments of the present application will be described below in conjunction with 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.

[0061] 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.

[0062] 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.

[0063] The schematic diagram of single-phase grounding fault in low current grounding system is as follows Figure 1 As shown, it includes ungrounded, grounded through arc suppression coil and grounded by active control device. is the neutral point voltage during normal operation, is the zero-sequence admittance of the arc suppression coil, is the damping conductance connected in parallel with the arc suppression coil. After a single-phase grounding fault occurs, whether it is fault phase transfer or active arc suppression, it is necessary to complete the selection of the fault phase. Therefore, after the fault occurs, the parallel damping resistor is put into operation. The neutral point is changed to actively offset the zero-sequence admittance vector, and the fault phase selection is completed based on the offset.

[0064] The phase selection method for a high-resistance grounding fault in a distribution network based on zero-sequence admittance vector offset in this embodiment is characterized by comprising:

[0065] Step 1: Set a resistor R1 with a switch between the neutral point of the distribution network and the ground.

[0066] Step 2: When the distribution network is operating normally, measure the zero-sequence voltage of the neutral point before and after the resistor R1 is connected to the neutral point, and calculate the total ground capacitance and total ground conductance of the distribution network system based on the geometric relationship of the zero-sequence admittance vector offset.

[0067] During normal operation, the expression of zero-sequence voltage before and after changes is:

[0068] (1)

[0069] Where, The zero-sequence voltages before and after the neutral point are measured when the distribution network is operating normally and the resistor R1 is connected to the neutral point; are the electromotive force of phases A, B, and C respectively, They are the relative admittances of feeder A, B, and C, and the total admittance of the system to ground , is the total system capacitance to ground, is the total system conductance to ground, is the system power frequency.

[0070] Separate orders Phase is , Phase is , Phase is , then from formula (1) we can get Phase is , Phase is The derivation process is:

[0071]

[0072] Further we can get:

[0073] (2)

[0074] According to formula (2), we can know Phase is , in combination with the measured Phase can be obtained by value, and the damping resistor It is known that the zero-sequence admittance vector deviation diagram after normal operation and neutral point switching damping conductance change is drawn as follows Figure 2 As shown, this figure mainly shows the total zero-sequence admittance of the system before and after the fault The vector diagram is used to analyze the geometric relationship between the two. The angle represents the phase of the total zero-sequence admittance of the system, and the distance represents the amplitude of the total zero-sequence admittance of the system.

[0075] make ,again It is known that by the sine formula We can get:

[0076] (3)

[0077] Step 3: After a single-phase high-resistance grounding fault occurs in the distribution network, the zero-sequence voltage of the neutral point before and after the resistor R1 is connected to the neutral point is measured, and the fault transition conductance is calculated based on the geometric relationship of the zero-sequence admittance vector offset.

[0078] After a phase C fault occurs, the parallel damping resistor is connected, and the expression of zero-sequence voltage change before and after is:

[0079] (4)

[0080] Where, is the zero-sequence voltage before and after the neutral point changes after the fault occurs, is the fault transition conductance.

[0081] Known Phase is , after the failure Phase is , after the failure Phase is Similarly, the zero-sequence admittance vector offset diagram after the fault occurs and the neutral point switching damping conductance changes is as follows: Figure 3 As shown. Figure 3 From the geometric relationship:

[0082] (5)

[0083] Step 4: Determine the zero-sequence admittance vector offset based on the zero-sequence voltage of the neutral point before the resistor R1 is connected, as well as the total ground capacitance, total ground conductance, and fault transition conductance of the distribution network system, respectively, under normal operation and fault conditions of the distribution network.

[0084] Combining equations (1) and (4) we get:

[0085] (6)

[0086] According to formula (6), With fault Phase consistent.

[0087] Zero-sequence voltage measured in the distribution network , and the line parameters calculated according to the expression Then we can get the vector offset value The offset value is the phase of the fault phase, so the fault phase can be accurately determined.

[0088] Step 5: Add preset margin values ​​to both ends of the zero-sequence admittance vector offset to obtain an offset interval of the zero-sequence admittance vector, and determine the phase spanned by the offset interval as the fault phase.

[0089] Theoretically, if the vector offset value obtained by measurement and calculation is consistent with the fault If the phase difference between the two adjacent phases is equal, it can be determined that the phase where the fault occurred is the phase. In practical applications, measurement and calculation errors should be considered and a certain margin should be reserved. Therefore, 1 / 4 of the 120° phase difference between the two adjacent phases is used as the margin value, which is set to , based on this to determine the corresponding phase selection criteria:

[0090] (7)

[0091] To avoid interference caused by asymmetric three-phase-to-ground parameters in the distribution network, the proposed criterion uses the change in zero-sequence voltage before and after the fault as the key measurement basis. Specifically, the zero-sequence voltage before a single-phase ground fault is solely due to the asymmetry of the three-phase-to-ground parameters; however, once the fault occurs, the zero-sequence voltage is caused by this asymmetry and the single-phase ground fault. By calculating the difference in zero-sequence voltage before and after the fault, we can obtain the zero-sequence voltage component caused by a single-phase ground fault. This method effectively offsets the impact of the system's inherent unbalanced voltage in the case of high-resistance ground faults; in the case of low-resistance ground faults, this difference characteristic is particularly prominent and is not affected by system asymmetry.

[0092] Case Analysis

[0093] A typical 10kV distribution network was simulated and analyzed using Pscad simulation software. The simulation model is shown in the attached figure. Three feeders are connected to the 10kV busbar. Fault zero-sequence parameters are measured using measurement devices at the feeder inlet. The line-related parameters are as follows:

[0094] Table 1 Line related parameters

[0095]

[0096] feeder L 1. L 2. L 3 Set the ground fault under fault and non-fault conditions respectively, and collect the feeder L The fault information of 3 includes zero-sequence current and zero-sequence voltage. A single-phase grounding fault occurs in any phase among A, B, and C at 0.2s. The parallel damping conductance is switched on at 0.5s. The phase selection criterion is calculated based on the zero-sequence admittance vector offset value. The phase selection results are shown in Table 2.

[0097] Table 2 Phase selection results

[0098]

[0099] When the feeder L 3 When a fault with a transition resistance of 0.01~12kΩ occurs, this method is used to select the fault phase. By calculating the zero-sequence admittance vector offset value and comparing it with the initial phase of the fault phase, it is obviously different from other normal phases. The results are correct and the error does not exceed 1°. The fault phase can be accurately selected, and the arc extinguishing device can be correctly operated to complete the fault handling.

[0100] The embodiment of the present application provides a phase selection system for a high-resistance grounding fault in a distribution network, comprising:

[0101] The resistance setting module is used to set a resistor R1 with a switch between the neutral point of the distribution network and the ground;

[0102] The first calculation module is used to measure the zero-sequence voltage of the neutral point before and after the resistor R1 is connected to the neutral point when the distribution network is operating normally, and calculate the total capacitance to ground and the total conductance to ground of the distribution network system based on the geometric relationship of the zero-sequence admittance vector offset;

[0103] The second calculation module is used to measure the zero-sequence voltage of the neutral point before and after the resistor R1 is connected to the neutral point after a single-phase high-resistance grounding fault occurs in the distribution network, and calculate the fault transition conductance based on the geometric relationship of the zero-sequence admittance vector offset;

[0104] A zero-sequence admittance vector offset determination module is used to determine the zero-sequence admittance vector offset based on the zero-sequence voltage of the neutral point during normal operation of the distribution network and before the resistor R1 is connected, as well as the total ground capacitance, total ground conductance and fault transition conductance of the distribution network system;

[0105] The fault phase determination module is used to add a preset margin value to both ends of the zero-sequence admittance vector offset to obtain an offset interval of the zero-sequence admittance vector, and determine the phase spanned by the offset interval as the fault phase.

[0106] An embodiment of the present application provides a computer-readable storage medium storing program code. When the program code is executed by a processor, the steps of the method for phase selection of a high-resistance grounding fault in a distribution network are implemented as described above.

[0107] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present application 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.

[0108] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0109] 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.

[0110] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational 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 A step that specifies a function in one or more boxes.

[0111] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0112] 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.

[0113] 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.

[0114] The above description is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, various modifications and variations of the present application are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A phase selection method for a high-resistance ground fault in a distribution network, characterized in that: The following steps are involved: During normal operation of the distribution network, the zero-sequence voltage at the neutral point before and after the resistor R1 is connected to the neutral point is measured, and the total capacitance to ground and the total conductance to ground of the distribution network system are calculated based on the geometric relationship of the zero-sequence admittance vector offset; wherein the resistor R1 is set between the neutral point of the distribution network and the ground; After a single-phase high-resistance grounding fault occurs in the distribution network, the zero-sequence voltage of the neutral point is measured before and after the resistor R1 is connected to the neutral point, and the fault transition conductance is calculated based on the geometric relationship of the zero-sequence admittance vector offset; The zero-sequence admittance vector offset is determined based on the zero-sequence voltage of the neutral point when the distribution network is operating normally and when a single-phase high-resistance ground fault occurs and before the resistor R1 is connected, as well as the total ground capacitance, total ground conductance and fault transition conductance of the distribution network system. Adding a preset margin value to both ends of the zero-sequence admittance vector offset to obtain an offset interval of the zero-sequence admittance vector, and determining the phase spanned by the offset interval as the fault phase; In the step of calculating the total capacitance to ground and the total conductance to ground of the distribution network system according to the geometric relationship of the zero-sequence admittance vector offset, the total capacitance to ground of the distribution network system is calculated specifically as follows: ， Where, is the total ground capacitance of the distribution network system, is the conductance of resistor R1, is the system power frequency, is the phase of the system’s total admittance to ground, is the phase of the system's total admittance to ground after resistor R1 is added; The total ground conductance of the distribution network system is calculated as follows: ， Where, is the total earth conductance of the distribution network system, is the conductance of resistor R1, is the system power frequency, is the phase of the system’s total admittance to ground, is the phase of the system's total admittance to ground after resistor R1 is added; The fault transition conductance is calculated based on the geometric relationship of the zero-sequence admittance vector offset, which is expressed as: ， Where, is the total ground capacitance of the distribution network system, is the fault transition conductance, is the phase of the sum of the system's total ground admittance and the fault transition conductance, is the phase of the sum of the system's total ground admittance and the fault transition conductance after resistor R1 is added. is the conductance of resistor R1.

2. A phase selection method for a high-resistance grounding fault in a distribution network according to claim 1, characterized in that: The resistor R1 is provided with a switch, and one resistor R1 is provided.

3. A phase selection method for a high-resistance grounding fault in a distribution network according to claim 1, characterized in that: The phase and phase The calculation method is: According to the zero-sequence voltage of the neutral point before and after the resistor R1 is connected to the neutral point during normal operation of the distribution network, the intermediate phase : ， Where, is the conductance of resistor R1, are the electromotive force of phases A, B, and C respectively, They are the relative admittances of feeder A, B, and C, and the total admittance of the system to ground The zero-sequence voltages before and after the neutral point are measured when the distribution network is operating normally and the resistor R1 is connected to the neutral point; according to and 、 ,get , and then calculate the phase of the total system admittance to ground ; and according to and 、 ,get , and then calculate the phase : ， 。 4. A phase selection method for a high-resistance grounding fault in a distribution network according to claim 1, characterized in that: The phase and phase The calculation method is: 。 5. A phase selection method for a high-resistance grounding fault in a distribution network according to claim 4, characterized in that: The method for determining the zero-sequence admittance vector offset is: ， Where, represents the electromotive force of the fault phase, Indicates the zero-sequence admittance vector offset during fault, To measure the zero-sequence voltage at the neutral point when the distribution network is operating normally and the resistor R1 is connected to the neutral point, is the total ground capacitance of the distribution network system, is the total earth conductance of the distribution network system, is the system power frequency, To measure the zero-sequence voltage before the neutral point when a single-phase high-resistance ground fault occurs in the distribution network and the resistor R1 is connected to the neutral point, is the fault transition conductance.

6. A phase selection method for a high-resistance grounding fault in a distribution network according to claim 1, characterized in that: The preset margin value is added to both ends of the zero-sequence admittance vector offset to obtain the offset interval of the zero-sequence admittance vector, which is , is the preset margin value.

7. A phase selection system for high-resistance ground fault in a distribution network, for implementing the method according to any one of claims 1 to 6, characterized in that: include, The resistance setting module is used to set a resistor R1 with a switch between the neutral point of the distribution network and the ground; The first calculation module is used to measure the zero-sequence voltage of the neutral point before and after the resistor R1 is connected to the neutral point when the distribution network is operating normally, and calculate the total capacitance to ground and the total conductance to ground of the distribution network system based on the geometric relationship of the zero-sequence admittance vector offset; The second calculation module is used to measure the zero-sequence voltage of the neutral point before and after the resistor R1 is connected to the neutral point after a single-phase high-resistance grounding fault occurs in the distribution network, and calculate the fault transition conductance based on the geometric relationship of the zero-sequence admittance vector offset; A zero-sequence admittance vector offset determination module is used to determine the zero-sequence admittance vector offset based on the zero-sequence voltage of the neutral point during normal operation of the distribution network and before the resistor R1 is connected, as well as the total ground capacitance, total ground conductance and fault transition conductance of the distribution network system; The fault phase determination module is used to add a preset margin value to both ends of the zero-sequence admittance vector offset to obtain an offset interval of the zero-sequence admittance vector, and determine the phase spanned by the offset interval as the fault phase.

8. A phase selection system for high-resistance grounding fault in a distribution network according to claim 7, characterized in that: In the step of calculating the total ground capacitance and total ground conductance of the distribution network system according to the geometric relationship of the zero-sequence admittance vector offset by the first calculation module, the total ground capacitance of the distribution network system is calculated specifically as follows: ， Where, is the total ground capacitance of the distribution network system, is the conductance of resistor R1, is the system power frequency, is the phase of the system’s total admittance to ground, is the phase of the system's total admittance to ground after resistor R1 is added; The total ground conductance of the distribution network system is calculated as follows: ， Where, is the total earth conductance of the distribution network system, is the conductance of resistor R1, is the system power frequency, is the phase of the system’s total admittance to ground, It is the phase of the total admittance of the system to ground after adding resistor R1.

9. A phase selection system for high-resistance grounding fault in a distribution network according to claim 7, characterized in that: The second calculation module calculates the fault transition conductance according to the geometric relationship of the zero-sequence admittance vector offset, which is expressed as: ， Where, is the total ground capacitance of the distribution network system, is the fault transition conductance, is the phase of the sum of the system's total ground admittance and the fault transition conductance, is the phase of the sum of the system's total ground admittance and the fault transition conductance after resistor R1 is added. is the conductance of resistor R1.

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 method for phase selection of a high-resistance grounding fault in a distribution network according to any one of claims 1 to 6 are implemented.

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