Single-phase grounding fault section location method, system and medium

Abstract

The present application relates to a method, system and medium for locating a single-phase grounding fault section. The method comprises detecting and extracting the zero-sequence current at sampling points in each section of the line; injecting an industrial frequency current signal into the neutral point, and again detecting and extracting the zero-sequence current at the sampling points in each section of the line; calculating the phase angle formed by the ratio of the relative change of the zero-sequence current at each sampling point to the zero-sequence current before and after the injection of the industrial frequency current signal at the neutral point; calculating the phase angle difference between the sampling points at both ends of the section, and determining the section corresponding to the maximum value of all phase angle differences as the grounding fault section. The present application can realize rapid and accurate fault section location.

Description

Technical Field

[0001] The present application relates to the technical field of distribution network fault detection, and in particular to a method, system and medium for locating a single-phase grounding fault section based on the ratio of the fault zero-sequence current phase angle difference. Background Art

[0002] As a critical national public infrastructure, the distribution network plays a vital role in ensuring power supply, supporting economic and social development, and improving people's livelihoods. The distribution network's topology and operating environment are complex, and the incidence of single-phase grounding faults is high. According to incomplete statistics from the State Grid, single-phase grounding faults account for over 80% of all faults. High-resistance grounding faults have weak fault characteristics, with fault currents typically only a few amperes or even less than one ampere. The complex environment of the lines, combined with the weak electrical characteristics of high-resistance grounding faults, makes it difficult to locate the section of the system when a high-resistance grounding fault occurs. This poses a serious threat to the distribution network and the safety of people's lives and property, with significant social impact. Therefore, research on high-resistance grounding fault section location technology in distribution networks is of great significance.

[0003] Current fault location techniques can be broadly categorized into two types. The first utilizes steady-state or transient measurements to identify characteristic differences for fault location. However, these methods are ineffective in detecting high-resistance ground faults and are affected by the system's ground admittance parameters. The second method involves signal injection, most notably the "S" injection method, which is significantly affected by the system's ground admittance parameters. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a single-phase grounding fault section locating method, system and medium, which can realize fast and accurate fault section locating.

[0005] To achieve the above objectives, this application provides the following technical solutions:

[0006] In a first aspect, an embodiment of the present application provides a method for locating a single-phase grounding fault section, comprising the following steps:

[0007] Detect and extract the zero-sequence current of sampling points in each section of the line;

[0008] Inject the power frequency current signal into the neutral point, and detect and extract the zero sequence current of the sampling points in each section of the line again;

[0009] According to the zero-sequence current extracted before and after the neutral point is injected with the power frequency current signal, the current at each sampling point is calculated. The phase angle formed by the ratio of the relative change of the zero-sequence current to the zero-sequence current before the power frequency current signal is injected ;

[0010] The phase angle difference between the sampling points at both ends of the section is calculated, and the section corresponding to the maximum value of all phase angle differences is determined as the ground fault section.

[0011] The distribution network automation terminal is used to detect and extract the zero-sequence current of the sampling points in each section of the line.

[0012] Sampling point The phase angle formed by the ratio of the relative change of the zero-sequence current to the zero-sequence current before the power frequency current signal is injected , its calculation expression is:

[0013]

[0014] Where, Sampling points for the segment The zero-sequence current difference before and after the power frequency current signal is injected into the neutral point, Sampling points for the segment The zero-sequence current value before the power frequency current signal is injected into the neutral point, Indicates phase angle operation.

[0015] The phase angle difference between the sampling points at both ends of the calculated section and the section corresponding to the maximum value of all the phase angle differences are determined as the ground fault section, specifically:

[0016] The distribution network is divided into n sections. The starting point of each section is used as the 1st to nth sampling points. Each sampling point is equipped with an automated terminal for current detection. The phase angle difference between the sampling points at both ends of the i-th section is calculated as follows:

[0017]

[0018] Where, Represents the phase angle difference between the sampling points at both ends of the i-th segment.

[0019] The power frequency current signal is injected into the neutral point by using a PWM active inverter.

[0020] In a second aspect, an embodiment of the present application provides a single-phase grounding fault section location system, comprising: a central processor and a plurality of automation terminals provided on each section of a distribution network line, each automation terminal being communicatively connected to the central processor;

[0021] The automation terminal is used to detect the zero-sequence current of the sampling points in each section of the line and send the detected zero-sequence current to the central processor;

[0022] The central processor is used to receive the zero-sequence current of each sampling point from each automation terminal, and calculate the zero-sequence current of each sampling point according to the zero-sequence current detected and extracted before and after the power frequency current signal is injected into the neutral point by the distribution network automation terminal. The phase angle formed by the ratio of the relative change of the zero-sequence current to the zero-sequence current before the power frequency current signal is injected , then calculate the phase angle difference between the sampling points at both ends of the section, and determine the section corresponding to the maximum value of all phase angle differences as the ground fault section.

[0023] Sampling point The phase angle formed by the relative change of zero sequence current , its calculation expression is:

[0024]

[0025] Where, Sampling points for the segment The zero-sequence current difference before and after the power frequency current signal is injected into the neutral point, Sampling points for the segment The zero-sequence current value before the power frequency current signal is injected into the neutral point, Indicates phase angle operation.

[0026] The distribution network is divided into n sections. The starting point of each section is used as the 1st to nth sampling points. Each sampling point is equipped with an automated terminal for current detection. The phase angle difference between the sampling points at both ends of the i-th section is calculated as follows:

[0027]

[0028] Where, Represents the phase angle difference between the sampling points at both ends of the i-th segment.

[0029] It also includes a PWM active inverter for injecting a power frequency current signal into the neutral point.

[0030] In a third aspect, an embodiment of the present application provides a computer-readable storage medium, wherein 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 section locating method as described above are implemented.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] When a single-phase grounding fault occurs in the power distribution system, the present invention uses a flexible grounding device to perform fault detection. When the fault type is determined to be a permanent fault, an industrial frequency current signal is injected into the neutral point through the flexible grounding device, and the zero-sequence current signals of the line and each section sampling point are detected and extracted using the distribution network automation terminal. Based on the difference in the zero-sequence current difference before and after signal injection and the phase angle of the zero-sequence current before the signal injection, the fault section can be quickly and accurately located. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] Figure 1 It is a single-phase grounding fault model of the flexible grounding distribution network described in the embodiment of the present application;

[0035] Figure 2 It is the zero-sequence equivalent model of single-phase grounding fault in the flexible grounding distribution network described in the embodiment of the present application;

[0036] Figure 3 This is a flow chart of the single-phase grounding fault section locating method described in an embodiment of the present application. DETAILED DESCRIPTION

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Example 1

[0041] Figure 1 is a single-phase grounding fault model for a 10kV distribution network flexible grounding system, where: It is a three-phase symmetrical power supply, Z0 is the arc suppression coil inductance, Rf is the fault resistance, and Y0 is the relative ground parameter. is the current signal injected into the system through the active inverter device, is the neutral point voltage.

[0042] The flexible grounding device consists of a DC power supply, a PWM inverter and an isolation transformer. S is the control switch. The proposed new topology is as follows: Figure 1 As shown, This is the current injected into the system by the flexible grounding device.

[0043] The impedance of the single-phase grounding fault model is decomposed according to the section. The distribution network line is divided into n sections. The starting point of each section is used as the 1st to nth sampling points. Each sampling point is set with an automatic terminal for current detection. The zero-sequence equivalent model of the flexible grounding distribution network fault is obtained as follows: Figure 2 As shown, where Z0 is the arc suppression coil inductance, is the current injected into the flexible device, ① represents the sampling point, Ye is the relative ground parameter between the sampling points, Gf is the fault conductance, It is the virtual power supply at the fault point. If phase C fails, , is the neutral point voltage. Assume that the fault occurs between the tth sampling point and the t+1th sampling point.

[0044] The method for locating a single-phase grounding fault section based on the ratio of the fault zero-sequence current phase angle difference in this embodiment includes:

[0045] Step 1: When a permanent single-phase ground fault occurs in the distribution network, the distribution network automation terminal detects and extracts the zero-sequence current of each section sampling point of the line. At this time (before the neutral point is injected with the power frequency current signal), the zero-sequence current value detected is expressed as , .

[0046] Step 2: Use a flexible grounding device to inject a power frequency current signal into the neutral point, and then use the distribution network automation terminal to detect and extract the zero-sequence current of the sampling points in each section of the line.

[0047] Sampling points of the segment At this time (after the power frequency current signal is injected into the neutral point), the zero-sequence current value detected is expressed as , .

[0048] Step 3: Calculate the zero-sequence current at each sampling point based on the zero-sequence current detected by the distribution network automation terminal before and after the power frequency current signal is injected into the neutral point. The phase angle difference formed by the relative change of zero sequence current , then calculate the phase angle difference between the sampling points at both ends of the section, and determine the section corresponding to the maximum value of all phase angle differences as the ground fault section.

[0049] Among them, the sampling points The phase angle formed by the ratio of the relative change of the zero-sequence current to the zero-sequence current before the power frequency current signal is injected , its calculation expression is:

[0050]

[0051] Where, Sampling points for the segment The zero-sequence current difference before and after the power frequency current signal is injected into the neutral point, Sampling points for the segment The zero-sequence current value before the power frequency current signal is injected into the neutral point, Indicates phase angle operation.

[0052] The phase angle difference between the sampling points at both ends of the i-th segment is calculated as:

[0053]

[0054] Where, Represents the phase angle difference between the sampling points at both ends of the i-th segment.

[0055] Final criterion Find the sampling point j with the largest m value, and the segment between sampling point j and sampling point j+1 (i.e. segment j) is the fault segment.

[0056] The following provides an explanation of the principle of the method for locating a single-phase grounding fault section in this embodiment:

[0057] 1. Variation trends of zero-sequence currents before and after the flexible device injects the signal.

[0058] Before injecting the power frequency signal, the system neutral point voltage can be known according to the node voltage method for:

[0059] (1)

[0060] It can be seen from formula (1) that the system neutral point voltage is related to the transition resistance and system admittance. Figure 2 It can be obtained that the zero-sequence current measured at the line head end and each sampling point of the line should theoretically be:

[0061] (2)

[0062] After the power frequency signal is injected, the neutral point voltage of the system will change. According to the circuit superposition theorem, when the flexible device acts alone, the neutral point voltage of the system will change. for:

[0063] (3)

[0064] When the system acts alone, the system neutral point voltage It is the neutral point voltage before the signal is injected.

[0065] (4)

[0066] According to the superposition theorem, when a single-phase ground fault occurs in the distribution network, the neutral point voltage of the distribution network after the active inverter injection device injects power frequency current is obtained as follows:

[0067] (5)

[0068] From formula (5), it can be seen that after the power frequency current signal is injected, the neutral point voltage is not only related to the transition resistance and the system's admittance to ground, but also to the amplitude and phase of the injected current. The larger the amplitude of the injected power frequency current signal, the greater the change in the system neutral point voltage and the change in the zero-sequence current in each section. When the transition resistance is constant, and the injected current amplitude does not affect the system operation, the injected power frequency current is adjusted. The phase angle of the zero-sequence current before and after the injection signal can be amplified.

[0069] After the power frequency signal is injected, the zero-sequence current measured at each sampling point of the fault line should be:

[0070] (6)

[0071] As the equation shows, after the power frequency current is injected, the zero-sequence current in the fault section changes with the neutral point voltage. Therefore, it will differ from the zero-sequence current before the power frequency signal was injected. By injecting current into the neutral point, flexible and proactive intervention can be achieved in the zero-sequence voltage of the distribution network and the zero-sequence current of the feeder.

[0072] By comparing and analyzing the zero-sequence currents in each section before and after the current signal is injected, it can be seen that the flexible grounding device regulates the zero-sequence currents in each section of the system by injecting controllable power frequency current. In addition, under the premise that the injected current amplitude does not affect the system operation, the phase angle of the injected current can be adjusted to amplify the phase angle difference of the zero-sequence current before and after the injection signal.

[0073] 2. Fault section location criterion based on the change of zero-sequence current before and after signal injection.

[0074] The fault section is determined by the phase angle of the ratio of the zero-sequence current before and after the power frequency signal is injected. The difference is calculated in turn to construct the positioning criterion. The change in zero-sequence current at the head end of the line and each sampling point of the line is:

[0075] (7)

[0076] Define the phase angle of the ratio of the zero-sequence current difference before and after the power frequency signal is injected to the zero-sequence current before the signal is injected as K, then there is a fault upstream:

[0077] (8)

[0078] Downstream of the fault:

[0079] (9)

[0080] Calculate the difference K between the zero-sequence current sampling points of the fault line, defined as k, and we have:

[0081] (10)

[0082] Then the m value corresponding to the sampling point before the fault section is calculated as:

[0083] (11)

[0084] The m value corresponding to the calculation of the first sampling point in the fault section is:

[0085] (12)

[0086] The m value corresponding to the sampling point after the fault section and the sampling point after the fault section is calculated as follows:

[0087] (13)

[0088] The zero sequence current of the sampled m value before the fault section differs by only one , the calculated m value is close to zero, and its value is also related to the number of sampling points. The more sampling points, the The smaller it is, the closer the m value is to zero.

[0089] Therefore, the positioning method used in the present invention is judged as follows:

[0090]

[0091] Find the sampling point j with the largest m value, and the fault section is located between the jth sampling point and the j+1th sampling point.

[0092] The embodiment of the present application provides a single-phase grounding fault section location system, comprising: a central processor and a plurality of automation terminals arranged on each section of a distribution network line, each automation terminal being in communication with the central processor;

[0093] The automation terminal is used to detect the zero-sequence current of the sampling points in each section of the line and send the detected zero-sequence current to the central processor;

[0094] The central processor is used to receive the zero-sequence current of each sampling point from each automation terminal, and calculate the zero-sequence current of each sampling point according to the zero-sequence current detected and extracted before and after the power frequency current signal is injected into the neutral point by the distribution network automation terminal. The phase angle formed by the ratio of the relative change of the zero-sequence current to the zero-sequence current before the power frequency current signal is injected , then calculate the phase angle difference between the sampling points at both ends of the section, and determine the section corresponding to the maximum value of all phase angle differences as the ground fault section.

[0095] 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 single-phase grounding fault section locating method described above are implemented.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0101] 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.

[0102] 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.

[0103] 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 method for locating a single-phase grounding fault section, characterized in that: The following steps are involved: Detect and extract the zero-sequence current of sampling points in each section of the line; Inject the power frequency current signal into the neutral point, and detect and extract the zero sequence current of the sampling points in each section of the line again; According to the zero-sequence current extracted before and after the neutral point is injected with the power frequency current signal, the current at each sampling point is calculated. The phase angle formed by the ratio of the relative change of the zero-sequence current to the zero-sequence current before the power frequency current signal is injected ; The phase angle difference between the sampling points at both ends of the section is calculated, and the section corresponding to the maximum value of all phase angle differences is determined as the ground fault section.

2. A method for locating a single-phase grounding fault section according to claim 1, characterized in that: The distribution network automation terminal is used to detect and extract the zero-sequence current of the sampling points in each section of the line.

3. A method for locating a single-phase grounding fault section according to claim 1, characterized in that: Sampling point The phase angle formed by the ratio of the relative change of the zero-sequence current to the zero-sequence current before the power frequency current signal is injected , its calculation expression is: ， Where, Sampling points for the segment The zero-sequence current difference before and after the power frequency current signal is injected into the neutral point, Sampling points for the segment The zero-sequence current value before the power frequency current signal is injected into the neutral point, Indicates phase angle operation.

4. A method for locating a single-phase grounding fault section according to claim 1, characterized in that: The phase angle difference between the sampling points at both ends of the calculated section and the section corresponding to the maximum value of all the phase angle differences are determined as the ground fault section, specifically: The distribution network is divided into n sections. The starting point of each section is used as the 1st to nth sampling points. Each sampling point is equipped with an automatic terminal for current detection. The phase angle difference between the sampling points at both ends of the i-th segment is calculated as: ， Where, Represents the phase angle difference between the sampling points at both ends of the i-th segment.

5. The method for locating a single-phase grounding fault section according to claim 1, characterized in that: The power frequency current signal is injected into the neutral point by using a PWM active inverter.

6. A single-phase grounding fault section location system, characterized in that: include: A central processor and a plurality of automation terminals arranged on each section of the power distribution network, each automation terminal being in communication with the central processor; The automation terminal is used to detect the zero-sequence current of the sampling points in each section of the line and send the detected zero-sequence current to the central processor; The central processor is used to receive the zero-sequence current of each sampling point from each automation terminal, and calculate the zero-sequence current of each sampling point according to the zero-sequence current detected and extracted before and after the power frequency current signal is injected into the neutral point by the distribution network automation terminal. The phase angle formed by the ratio of the relative change of the zero-sequence current to the zero-sequence current before the power frequency current signal is injected , then calculate the phase angle difference between the sampling points at both ends of the section, and determine the section corresponding to the maximum value of all phase angle differences as the ground fault section.

7. A single-phase grounding fault section locating system according to claim 6, characterized in that: Sampling point The phase angle formed by the relative change of zero sequence current , its calculation expression is: ， Where, Sampling points for the segment The zero-sequence current difference before and after the power frequency current signal is injected into the neutral point, Sampling points for the segment The zero-sequence current value before the power frequency current signal is injected into the neutral point, Indicates phase angle operation.

8. A single-phase grounding fault section location system according to claim 6, characterized in that: The distribution network is divided into n sections. The starting point of each section is used as the 1st to nth sampling points. Each sampling point is equipped with an automatic terminal for current detection. The phase angle difference between the sampling points at both ends of the i-th segment is calculated as: ， Where, Represents the phase angle difference between the sampling points at both ends of the i-th segment.

9. A single-phase grounding fault section locating system according to claim 6, characterized in that: It also includes a PWM active inverter for injecting a power frequency current signal into the neutral point.

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 section locating method according to any one of claims 1 to 5 are implemented.

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