A method and device for locating single-phase grounding fault in a small current grounding system

Abstract

The present invention provides a method and device for locating a single-phase grounding fault in a small current grounding system. When a single-phase grounding fault occurs in the small current grounding system, the phase current of the monitoring point is obtained; the amplitude and phase of the phase current component are determined based on the phase current; the single-phase grounding fault is located based on the amplitude and phase, and the positioning process is simple and the positioning result is highly reliable. The technical solution provided by the present invention does not rely on electromagnetic voltage sensors and capacitive voltage sensors, avoids ferromagnetic resonance, and does not affect the safe and stable operation of the primary side of the distribution network; it relies as much as possible on the local signals collected by the electric field sensors and current transformers installed at the monitoring points to detect and locate the single-phase grounding fault, avoiding a large amount of information communication and effectively improving the reliability of detection and positioning.

Description

Technical Field

[0001] The invention relates to the technical field of power distribution networks, and in particular to a method and device for locating a single-phase grounding fault in a small current grounding system. Background Art

[0002] Distribution networks mostly use low-current grounding, and single-phase grounding faults are one of the most frequent faults. Since the neutral point is not directly grounded, the fault path impedance value formed by the single-phase grounding fault is large, and the fault manifestation caused is not obvious. At the same time, due to noise interference and the influence of distribution network operation conditions (such as asymmetry), the existing single-phase grounding fault detection and positioning methods of small current grounding systems have undergone long-term and extensive research, but they still have shortcomings in reliability and universal applicability.

[0003] In the prior art, the detection of single-phase grounding faults in small current grounding systems is usually based on zero-sequence voltage. When there is an obvious and long-lasting zero-sequence voltage in the small current grounding system, it is determined that a permanent single-phase grounding fault occurs in the small current grounding system. This method has two problems: on the one hand, the three-phase imbalance phenomenon is common in the distribution network, which will also cause persistent zero-sequence voltage, which is easy to be confused with a single-phase grounding fault; on the other hand, the zero-sequence voltage in the distribution network is mostly collected by electromagnetic voltage transformers, which are easy to cause ferromagnetic resonance after a single-phase grounding fault occurs, endangering the safety of the small current grounding system.

[0004] In the existing technology, the single-phase grounding fault location of the small current grounding system is generally based on the different characteristic quantities. The specific methods can be divided into three categories: signal injection method, steady-state quantity location method and transient quantity location method. Among them, the signal injection method requires additional signal devices, and the positioning process is complicated; the characteristic signal in the steady-state quantity location method is weak, and the reliability of the positioning result is low; and the transient characteristics based on the transient quantity location method are several times or even dozens of times larger than the steady-state value, and are not affected by the arc suppression coil, so it has higher application value. However, due to its short existence time, transient quantities are difficult to capture and extract signals. In addition, it is necessary to compare transient quantities at different locations for fault location, which is highly dependent on communication technology and has low reliability of positioning results. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, such as the complex positioning process and the low reliability of the positioning results, the present invention provides a method and device for locating a single-phase grounding fault in a small current grounding system. When a single-phase grounding fault occurs in the small current grounding system, the phase current of the monitoring point is obtained; the amplitude and phase of the phase current component are determined based on the phase current; the single-phase grounding fault is located based on the amplitude and phase, the positioning process is simple, and the reliability of the positioning result is high.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical scheme:

[0007] On the one hand, the present invention provides a method for locating a single-phase grounding fault in a small current grounding system, comprising:

[0008] When a single-phase grounding fault occurs in the small current grounding system, the phase current of the monitoring point is obtained;

[0009] determining the magnitude and phase of a phase current component based on the phase current;

[0010] Locate single-phase to ground fault based on amplitude and phase.

[0011] When a single-phase grounding fault occurs in the small current grounding system, before obtaining the phase current of the monitoring point, the method includes:

[0012] Based on the electric field sensors and current transformers installed at each monitoring point on the overhead line of the distribution network, the phase electric field and phase current of the monitoring point are obtained in real time, and based on the phase electric field, it is determined whether a single-phase grounding fault occurs in the small current grounding system.

[0013] The determining whether a single-phase grounding fault occurs in the low-current grounding system based on the phase electric field includes:

[0014] If the phase electric field drop amplitude of a phase at the monitoring point exceeds the preset first phase electric field threshold, and the phase electric field increase amplitudes of the other two phases exceed the preset second phase electric field threshold, it is determined that a single-phase grounding fault has occurred in the small current grounding system, and the phase whose phase electric field drop amplitude exceeds the first preset threshold is the faulty phase.

[0015] The determining the amplitude and phase of the phase current component based on the phase current comprises:

[0016] determining phase current components based on the phase currents;

[0017] A magnitude and a phase of the phase current component are determined based on the phase current component.

[0018] The determining of the phase current component based on the phase current comprises:

[0019] Intercepting the phase current waveform of at least two cycles before and after the single-phase grounding fault occurs;

[0020] Based on the periodic characteristics and frequency characteristics of the phase current, the power frequency load current component is removed from the intercepted phase current waveform to obtain the phase current component.

[0021] The method of locating a single-phase grounding fault based on amplitude and phase includes:

[0022] If the absolute value of the phase difference between the fault phase and the non-fault phase exceeds a preset phase threshold, and the amplitude of the fault phase is greater than or equal to the sum of the amplitudes of the two non-fault phases, it is determined that a single-phase grounding fault occurs downstream of the monitoring point;

[0023] If the absolute value of the phase difference between the faulty phase and the non-faulty phase does not exceed the preset phase threshold, or the amplitude of the faulty phase is less than the sum of the amplitudes of the two non-faulty phases, it is determined that no single-phase grounding fault occurs downstream of the monitoring point.

[0024] After locating the single-phase grounding fault based on the amplitude and phase, the method includes:

[0025] monitoring the duration of the single-phase ground fault;

[0026] The type of the single-phase grounding fault is determined based on the duration.

[0027] The determining the type of the single-phase grounding fault based on the duration includes:

[0028] If the duration exceeds a preset time threshold and the single-phase grounding fault is not eliminated, determining that the single-phase grounding fault is a permanent single-phase grounding fault;

[0029] If the duration does not exceed a preset time threshold, and the single-phase grounding fault occurs once and then automatically eliminates, it is determined that the single-phase grounding fault is an instantaneous single-phase grounding fault.

[0030] If the duration does not exceed a preset time threshold, and the single-phase grounding fault occurs multiple times and is automatically eliminated, it is determined that the single-phase grounding fault is an intermittent single-phase grounding fault.

[0031] After determining the type of the single-phase grounding fault based on the duration, the method further comprises:

[0032] The action mode of the local switch at the monitoring point is determined based on the location of the monitoring point and the fault type.

[0033] The determining of the action mode of the local switch at the monitoring point based on the location and fault type of the monitoring point includes:

[0034] If a single-phase grounding fault occurs downstream of the monitoring point and the monitoring point is located on a branch line, if the single-phase grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switch is tripped, and the monitoring point sends the fault location information to the main station; if the single-phase grounding fault is an instantaneous single-phase grounding fault, the monitoring point sends risk warning information to the main station;

[0035] If a single-phase grounding fault occurs downstream of the monitoring point, and no single-phase grounding fault occurs downstream of the monitoring point adjacent to the monitoring point, and the monitoring point is located on the feeder main line, if the single-line grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switches at the two monitoring points will be tripped, and the two monitoring points will send the fault location information to the main station respectively; if the single-phase grounding fault is an instantaneous single-phase grounding fault, the two monitoring points will send risk warning information to the main station respectively.

[0036] On the other hand, the present invention also provides a single-phase grounding fault locating device for a small current grounding system, comprising:

[0037] An acquisition module, used for acquiring the phase current of the monitoring point when a single-phase grounding fault occurs in the small current grounding system;

[0038] A determination module, configured to determine the amplitude and phase of a phase current component based on the phase current;

[0039] The positioning module is used to locate the single-phase grounding fault based on the amplitude and phase.

[0040] The device further includes a first judgment module, wherein the first judgment module is specifically configured to:

[0041] Based on the electric field sensors and current transformers installed at each monitoring point on the overhead line of the distribution network, the phase electric field and phase current of the monitoring point are obtained in real time, and based on the phase electric field, it is determined whether a single-phase grounding fault occurs in the small current grounding system.

[0042] The first judging unit is specifically configured to:

[0043] If the phase electric field drop amplitude of a phase at the monitoring point exceeds the preset first phase electric field threshold, and the phase electric field increase amplitudes of the other two phases exceed the preset second phase electric field threshold, it is determined that a single-phase grounding fault has occurred in the small current grounding system, and the phase whose phase electric field drop amplitude exceeds the first preset threshold is the faulty phase.

[0044] The determination module comprises:

[0045] A first determining unit, configured to determine a phase current component based on the phase current;

[0046] The second determining unit is used to determine the amplitude and phase of the phase current component based on the phase current component.

[0047] The first determining unit is specifically configured to:

[0048] Intercepting the phase current waveform of at least two cycles before and after the single-phase grounding fault occurs;

[0049] Based on the periodic characteristics and frequency characteristics of the phase current, the power frequency load current component is removed from the intercepted phase current waveform to obtain the phase current component.

[0050] The positioning module is specifically used for:

[0051] If the absolute value of the phase difference between the fault phase and the non-fault phase exceeds a preset phase threshold, and the amplitude of the fault phase is greater than or equal to the sum of the amplitudes of the two non-fault phases, it is determined that a single-phase grounding fault occurs downstream of the monitoring point;

[0052] If the absolute value of the phase difference between the faulty phase and the non-faulty phase does not exceed the preset phase threshold, or the amplitude of the faulty phase is less than the sum of the amplitudes of the two non-faulty phases, it is determined that no single-phase grounding fault occurs downstream of the monitoring point.

[0053] The device further includes a second judgment module, wherein the second judgment module includes:

[0054] A monitoring unit, used for monitoring the duration of the single-phase grounding fault;

[0055] The second judgment unit is configured to judge the type of the single-phase grounding fault based on the duration.

[0056] The second judgment unit is specifically used for:

[0057] If the duration exceeds a preset time threshold and the single-phase grounding fault is not eliminated, determining that the single-phase grounding fault is a permanent single-phase grounding fault;

[0058] If the duration does not exceed a preset time threshold, and the single-phase grounding fault occurs once and then automatically eliminates, it is determined that the single-phase grounding fault is an instantaneous single-phase grounding fault.

[0059] If the duration does not exceed a preset time threshold, and the single-phase grounding fault occurs multiple times and is automatically eliminated, it is determined that the single-phase grounding fault is an intermittent single-phase grounding fault.

[0060] The device further includes an execution module, which is specifically configured to:

[0061] The action mode of the local switch at the monitoring point is determined based on the location of the monitoring point and the fault type.

[0062] The execution module is specifically used for:

[0063] If a single-phase grounding fault occurs downstream of the monitoring point and the monitoring point is located on a branch line, if the single-phase grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switch is tripped, and the monitoring point sends the fault location information to the main station; if the single-phase grounding fault is an instantaneous single-phase grounding fault, the monitoring point sends risk warning information to the main station;

[0064] If a single-phase grounding fault occurs downstream of the monitoring point, and no single-phase grounding fault occurs downstream of the monitoring point adjacent to the monitoring point, and the monitoring point is located on the feeder main line, if the single-line grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switches at the two monitoring points will be tripped, and the two monitoring points will send the fault location information to the main station respectively; if the single-phase grounding fault is an instantaneous single-phase grounding fault, the two monitoring points will send risk warning information to the main station respectively.

[0065] Compared with the closest prior art, the technical solution provided by the present invention has the following beneficial effects:

[0066] In the method for locating a single-phase grounding fault in a small current grounding system provided by the present invention, when a single-phase grounding fault occurs in the small current grounding system, the phase current of the monitoring point is obtained; the amplitude and phase of the phase current component are determined based on the phase current; the single-phase grounding fault is located based on the amplitude and phase, the locating process is simple, and the reliability of the locating result is high;

[0067] The technical solution provided by the present invention not only detects the single-phase grounding fault occurring in the small current grounding system based on the phase electric field, but also locates the single-phase grounding fault through the phase current, and at the same time determines the fault type of the fault, and gives the action mode of the local switch at the monitoring point;

[0068] The technical solution provided by the present invention does not rely on electromagnetic voltage sensors and capacitive voltage sensors, avoids ferromagnetic resonance, and does not affect the safe and stable operation of the primary side of the distribution network;

[0069] The technical solution provided by the present invention relies as much as possible on the local signals collected by the electric field sensors and current transformers installed at the monitoring points to detect and locate single-phase grounding faults, avoiding a large amount of information communication and effectively improving the reliability of detection and positioning;

[0070] The technical solution provided by the present invention reasonably utilizes the phase electric field and the phase current, and adopts prominent fault characteristics, thereby achieving accurate, reliable and rapid detection and positioning of single-phase grounding faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 It is a flow chart of a method for locating a single-phase grounding fault in a small current grounding system of the present invention;

[0072] Figure 2 It is a schematic diagram of a single-phase grounding fault occurring in a small current grounding system in an embodiment of the present invention. DETAILED DESCRIPTION

[0073] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0074] Example 1

[0075] Embodiment 1 of the present invention provides a method for locating a single-phase grounding fault in a small current grounding system. The specific flow chart is as follows: Figure 1 As shown, the specific process is as follows:

[0076] S101: When a single-phase grounding fault occurs in a low-current grounding system, the phase current of the monitoring point is obtained;

[0077] S102: Determine the amplitude and phase of the phase current component based on the phase current;

[0078] S103: Locate the single-phase grounding fault based on the amplitude and phase.

[0079] When a single-phase grounding fault occurs in the low-current grounding system in S101, before obtaining the phase current of the monitoring point, single-phase grounding fault detection is performed, including:

[0080] Based on the electric field sensors and current transformers installed at each monitoring point on the overhead line of the distribution network, the phase electric field and phase current of the monitoring point are obtained in real time, and based on the phase electric field, it is determined whether a single-phase grounding fault occurs in the small current grounding system.

[0081] Schematic diagram of single-phase grounding fault in small current grounding system Figure 2 As shown, Figure 2 In the figure, F is the fault location. The configuration principle of the monitoring point is as follows: 1) One monitoring point is configured at the outgoing switch (such as Figure 2 M1 and M4 of the line); 2) As the line extends, a monitoring point is configured at each section switch (such as Figure 2 The density of the configuration determines the accuracy of fault diagnosis;

[0082] Based on the phase electric field, it is judged whether a single-phase grounding fault occurs in the small current grounding system. The specific process is as follows:

[0083] If the phase electric field drop amplitude of a phase at the monitoring point exceeds the preset first phase electric field threshold (for example, the phase electric field drop amplitude of a phase exceeds 50%), and the phase electric field increase amplitude of the other two phases exceeds the preset second phase electric field threshold (for example, the phase electric field increase amplitude of the other two phases exceeds 50%), it is determined that a single-phase grounding fault has occurred in the small current grounding system, and the phase whose phase electric field drop amplitude exceeds the first preset threshold is the fault phase, and the phases whose phase electric field increase amplitude of the other two phases exceeds the preset second phase electric field threshold are non-fault phases.

[0084] In the above S102, the amplitude and phase of the phase current component are determined based on the phase current, including:

[0085] determining phase current components based on the phase currents;

[0086] The amplitude and phase of the phase current components are determined based on the phase current components. The specific process is as follows:

[0087] Intercept the phase current waveform of at least two cycles before and after the single-phase grounding fault occurs (for example, three cycles are intercepted before and after, i.e., 3*0.02s=0.06s in time length);

[0088] Based on the periodic and frequency characteristics of the phase current, the power frequency load current component is removed from the intercepted phase current waveform (such as the values ​​collected at each collection point three cycles after the fault occurs, and the values ​​collected at the corresponding collection points three cycles before the fault occurs are synchronously subtracted, or the power frequency current signal is filtered out using a bandpass filter) to obtain the phase current component.

[0089] In the above S103, the single-phase grounding fault is located based on the amplitude and phase, which is specifically divided into the following two cases:

[0090] If the absolute value of the phase difference between the fault phase and the non-fault phase exceeds the preset phase threshold, and the amplitude of the fault phase is greater than or equal to the sum of the amplitudes of the two non-fault phases, it is determined that a single-phase grounding fault occurs downstream of the monitoring point;

[0091] If the absolute value of the phase difference between the faulty phase and the non-faulty phase does not exceed the preset phase threshold, or the amplitude of the faulty phase is less than the sum of the amplitudes of the two non-faulty phases, it is determined that no single-phase grounding fault occurs downstream of the monitoring point.

[0092] After the single-phase grounding fault is located based on the amplitude and the phase in S103, the following steps are included:

[0093] Monitor the duration of single-phase ground fault;

[0094] The type of single-phase grounding fault is determined based on the duration, which is divided into the following three situations:

[0095] If the duration exceeds a preset time threshold and the single-phase grounding fault is not eliminated, the single-phase grounding fault is determined to be a permanent single-phase grounding fault;

[0096] If the duration does not exceed the preset time threshold, and the single-phase grounding fault occurs once and then automatically eliminates, it is determined that the single-phase grounding fault is a transient single-phase grounding fault.

[0097] If the duration does not exceed the preset time threshold, and the single-phase grounding fault occurs multiple times and is automatically eliminated, it is determined that the single-phase grounding fault is an intermittent single-phase grounding fault.

[0098] After the type of the single-phase grounding fault is determined based on the duration, the action mode of the local switch at the monitoring point is determined based on the location of the monitoring point and the fault type.

[0099] The action mode of the local switch (section switch or outgoing line switch) at the monitoring point is determined based on the location of the monitoring point and the fault type. The specific process is as follows:

[0100] If a single-phase grounding fault occurs downstream of the monitoring point and the monitoring point is located on a branch line, if the single-phase grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switch will be tripped and the monitoring point will send the fault location information to the main station; if the single-phase grounding fault is an instantaneous single-phase grounding fault, the monitoring point will send a risk warning message to the main station;

[0101] If a single-phase grounding fault occurs downstream of a monitoring point, and no single-phase grounding fault occurs downstream of a monitoring point adjacent to the monitoring point (i.e., the single-phase grounding fault occurs between a monitoring point and a monitoring point located downstream of and adjacent to the monitoring point), and the monitoring point is located on the main feeder line, if the single-line grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switches at the two monitoring points will be tripped, and the two monitoring points will send the fault location information to the main station respectively; if the single-phase grounding fault is a transient single-phase grounding fault, the two monitoring points will send risk warning information to the main station respectively.

[0102] Example 2

[0103] Based on the same inventive concept, Embodiment 2 of the present invention further provides a single-phase grounding fault locating device for a small current grounding system, including an acquisition module, a determination module and a locating module. The functions of the above modules are described in detail below:

[0104] An acquisition module is used to acquire the phase current of the monitoring point when a single-phase grounding fault occurs in a small current grounding system;

[0105] A determination module, configured to determine the magnitude and phase of a phase current component based on the phase current;

[0106] The positioning module is used to locate the single-phase grounding fault based on the amplitude and phase.

[0107] The device provided in Embodiment 2 of the present invention further includes a first judgment module, which is specifically configured to:

[0108] Based on the electric field sensors and current transformers installed at each monitoring point on the overhead line of the distribution network, the phase electric field and phase current of the monitoring point are obtained in real time, and based on the phase electric field, it is determined whether a single-phase grounding fault occurs in the small current grounding system.

[0109] The first judgment unit is specifically used for:

[0110] If the phase electric field drop amplitude of a phase at the monitoring point exceeds the preset first phase electric field threshold, and the phase electric field increase amplitudes of the other two phases exceed the preset second phase electric field threshold, it is determined that a single-phase grounding fault has occurred in the small current grounding system, and the phase whose phase electric field drop amplitude exceeds the first preset threshold is the faulty phase.

[0111] The above-mentioned determination module includes:

[0112] A first determining unit, configured to determine a phase current component based on the phase current;

[0113] The second determining unit is used to determine the amplitude and phase of the phase current component based on the phase current component.

[0114] The first determining unit is specifically configured to:

[0115] Intercepting the phase current waveform of at least two cycles before and after the single-phase grounding fault occurs;

[0116] Based on the periodic characteristics and frequency characteristics of the phase current, the power frequency load current component is removed from the intercepted phase current waveform to obtain the phase current component.

[0117] The above positioning module is specifically used for:

[0118] If the absolute value of the phase difference between the fault phase and the non-fault phase exceeds the preset phase threshold, and the amplitude of the fault phase is greater than or equal to the sum of the amplitudes of the two non-fault phases, it is determined that a single-phase grounding fault occurs downstream of the monitoring point;

[0119] If the absolute value of the phase difference between the faulty phase and the non-faulty phase does not exceed the preset phase threshold, or the amplitude of the faulty phase is less than the sum of the amplitudes of the two non-faulty phases, it is determined that no single-phase grounding fault occurs downstream of the monitoring point.

[0120] The device provided in Embodiment 2 of the present invention further includes a second judgment module, and the second judgment module includes:

[0121] A monitoring unit, used for monitoring the duration of a single-phase grounding fault;

[0122] The second judgment unit is used to judge the type of the single-phase grounding fault based on the duration.

[0123] The second judgment unit is specifically used for:

[0124] If the duration exceeds a preset time threshold and the single-phase grounding fault is not eliminated, the single-phase grounding fault is determined to be a permanent single-phase grounding fault;

[0125] If the duration does not exceed the preset time threshold, and the single-phase grounding fault occurs once and then automatically eliminates, it is determined that the single-phase grounding fault is a transient single-phase grounding fault.

[0126] If the duration does not exceed the preset time threshold, and the single-phase grounding fault occurs multiple times and is automatically eliminated, it is determined that the single-phase grounding fault is an intermittent single-phase grounding fault.

[0127] The device provided in Embodiment 2 of the present invention further includes an execution module, which determines the action mode of the local switch at the monitoring point based on the location of the monitoring point and the fault type. The specific process is as follows:

[0128] If a single-phase grounding fault occurs downstream of the monitoring point and the monitoring point is located on a branch line, if the single-phase grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switch will be tripped and the monitoring point will send the fault location information to the main station; if the single-phase grounding fault is an instantaneous single-phase grounding fault, the monitoring point will send a risk warning message to the main station;

[0129] If a single-phase grounding fault occurs downstream of the monitoring point, and no single-phase grounding fault occurs downstream of the monitoring point adjacent to the monitoring point, and the monitoring point is located on the feeder main line, if the single-line grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switches at the two monitoring points will be tripped, and the two monitoring points will send the fault location information to the main station respectively; if the single-phase grounding fault is an instantaneous single-phase grounding fault, the two monitoring points will send risk warning information to the main station respectively.

[0130] For the convenience of description, the various parts of the above-mentioned device are divided into various modules or units according to their functions and described separately. Of course, when implementing the present application, the functions of each module or unit can be implemented in the same or multiple software or hardware.

[0131] 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 adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0132] 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 box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes 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 generate 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.

[0133] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate 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 A function specified in one or more boxes.

[0134] 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 instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Ordinary technicians in the relevant field can still modify or make equivalent substitutions to the specific implementation methods of the present invention with reference to the above embodiments. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A method for locating a single-phase grounding fault in a small current grounding system, characterized in that: include: When a single-phase grounding fault occurs in the small current grounding system, the phase current of the monitoring point is obtained; determining the magnitude and phase of a phase current component based on the phase current; Locate single-phase ground fault based on amplitude and phase; When a single-phase grounding fault occurs in the small current grounding system, before obtaining the phase current of the monitoring point, the method includes: Based on the electric field sensors and current transformers installed at each monitoring point on the overhead line of the distribution network, the phase electric field and phase current of the monitoring point are obtained in real time, and based on the phase electric field, it is determined whether a single-phase grounding fault occurs in the small current grounding system; The determining whether a single-phase grounding fault occurs in the low-current grounding system based on the phase electric field includes: If the phase electric field drop amplitude of a phase at the monitoring point exceeds the preset first phase electric field threshold, and the phase electric field increase amplitudes of the other two phases exceed the preset second phase electric field threshold, it is determined that a single-phase grounding fault occurs in the small current grounding system, and the phase whose phase electric field drop amplitude exceeds the first preset threshold is the fault phase; The determining the amplitude and phase of the phase current component based on the phase current comprises: determining phase current components based on the phase currents; determining the magnitude and phase of the phase current component based on the phase current component; The determining of the phase current component based on the phase current comprises: Intercepting the phase current waveform of at least two cycles before and after the single-phase grounding fault occurs; Based on the periodic characteristics and frequency characteristics of the phase current, the power frequency load current component is removed from the intercepted phase current waveform to obtain the phase current component; The method of locating a single-phase grounding fault based on amplitude and phase includes: If the absolute value of the phase difference between the fault phase and the non-fault phase exceeds a preset phase threshold, and the amplitude of the fault phase is greater than or equal to the sum of the amplitudes of the two non-fault phases, it is determined that a single-phase grounding fault occurs downstream of the monitoring point; If the absolute value of the phase difference between the faulty phase and the non-faulty phase does not exceed the preset phase threshold, or the amplitude of the faulty phase is less than the sum of the amplitudes of the two non-faulty phases, it is determined that no single-phase grounding fault occurs downstream of the monitoring point.

2. The method for locating a single-phase grounding fault in a small current grounding system according to claim 1, characterized in that: After locating the single-phase grounding fault based on the amplitude and the phase, the method includes: monitoring the duration of the single-phase ground fault; The type of the single-phase grounding fault is determined based on the duration.

3. The method for locating a single-phase grounding fault in a small current grounding system according to claim 2, characterized in that: The determining the type of the single-phase grounding fault based on the duration includes: If the duration exceeds a preset time threshold and the single-phase grounding fault is not eliminated, determining that the single-phase grounding fault is a permanent single-phase grounding fault; If the duration does not exceed the preset time threshold, and the single-phase grounding fault occurs once and then automatically disappears, it is determined that the single-phase grounding fault is an instantaneous single-phase grounding fault; If the duration does not exceed a preset time threshold, and the single-phase grounding fault occurs multiple times and is automatically eliminated, it is determined that the single-phase grounding fault is an intermittent single-phase grounding fault.

4. The method for locating a single-phase grounding fault in a small current grounding system according to claim 3, characterized in that: After determining the type of the single-phase grounding fault based on the duration, the method further comprises: The action mode of the local switch at the monitoring point is determined based on the location of the monitoring point and the fault type.

5. The method for locating a single-phase grounding fault in a small current grounding system according to claim 4, characterized in that: The determining the action mode of the local switch at the monitoring point based on the location and fault type of the monitoring point includes: If a single-phase grounding fault occurs downstream of the monitoring point and the monitoring point is located on a branch line, if the single-phase grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switch is tripped, and the monitoring point sends the fault location information to the main station; if the single-phase grounding fault is an instantaneous single-phase grounding fault, the monitoring point sends risk warning information to the main station; If a single-phase grounding fault occurs downstream of the monitoring point, and no single-phase grounding fault occurs downstream of the monitoring point adjacent to the monitoring point, and the monitoring point is located on the feeder main line, if the single-line grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switches at the two monitoring points will be tripped, and the two monitoring points will send the fault location information to the main station respectively; if the single-phase grounding fault is an instantaneous single-phase grounding fault, the two monitoring points will send risk warning information to the main station respectively.

6. A single-phase grounding fault location device for a small current grounding system, characterized in that: include: An acquisition module, used for acquiring the phase current of the monitoring point when a single-phase grounding fault occurs in the small current grounding system; A determination module, configured to determine the amplitude and phase of a phase current component based on the phase current; A positioning module, used for locating a single-phase grounding fault based on amplitude and phase; The device further includes a first judgment module, wherein the first judgment module is specifically configured to: Based on the electric field sensors and current transformers installed at each monitoring point on the overhead line of the distribution network, the phase electric field and phase current of the monitoring point are obtained in real time, and based on the phase electric field, it is determined whether a single-phase grounding fault occurs in the small current grounding system; The first judgment module is specifically used for: If the phase electric field drop amplitude of a phase at the monitoring point exceeds the preset first phase electric field threshold, and the phase electric field increase amplitudes of the other two phases exceed the preset second phase electric field threshold, it is determined that a single-phase grounding fault occurs in the small current grounding system, and the phase whose phase electric field drop amplitude exceeds the first preset threshold is the fault phase; The determination module comprises: A first determining unit, configured to determine a phase current component based on the phase current; a second determining unit, configured to determine the amplitude and phase of a phase current component based on the phase current component; The first determining unit is specifically configured to: Intercepting the phase current waveform of at least two cycles before and after the single-phase grounding fault occurs; Based on the periodic characteristics and frequency characteristics of the phase current, the power frequency load current component is removed from the intercepted phase current waveform to obtain the phase current component; The positioning module is specifically used for: If the absolute value of the phase difference between the fault phase and the non-fault phase exceeds a preset phase threshold, and the amplitude of the fault phase is greater than or equal to the sum of the amplitudes of the two non-fault phases, it is determined that a single-phase grounding fault occurs downstream of the monitoring point; If the absolute value of the phase difference between the faulty phase and the non-faulty phase does not exceed the preset phase threshold, or the amplitude of the faulty phase is less than the sum of the amplitudes of the two non-faulty phases, it is determined that no single-phase grounding fault occurs downstream of the monitoring point.

7. The single-phase grounding fault location device for a small current grounding system according to claim 6, characterized in that: The device further includes a second judgment module, wherein the second judgment module includes: A monitoring unit, used for monitoring the duration of the single-phase grounding fault; The second judgment unit is configured to judge the type of the single-phase grounding fault based on the duration.

8. The single-phase grounding fault location device for a small current grounding system according to claim 7, characterized in that: The second judgment unit is specifically used for: If the duration exceeds a preset time threshold and the single-phase grounding fault is not eliminated, determining that the single-phase grounding fault is a permanent single-phase grounding fault; If the duration does not exceed the preset time threshold, and the single-phase grounding fault occurs once and then automatically disappears, it is determined that the single-phase grounding fault is an instantaneous single-phase grounding fault; If the duration does not exceed a preset time threshold, and the single-phase grounding fault occurs multiple times and is automatically eliminated, it is determined that the single-phase grounding fault is an intermittent single-phase grounding fault.

9. The single-phase grounding fault location device for a small current grounding system according to claim 8, characterized in that: The device further includes an execution module, which is specifically configured to: The action mode of the local switch at the monitoring point is determined based on the location of the monitoring point and the fault type.

10. The single-phase grounding fault location device for a small current grounding system according to claim 9, characterized in that: The execution module is specifically used for: If a single-phase grounding fault occurs downstream of the monitoring point and the monitoring point is located on a branch line, if the single-phase grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switch is tripped, and the monitoring point sends the fault location information to the main station; if the single-phase grounding fault is an instantaneous single-phase grounding fault, the monitoring point sends risk warning information to the main station; If a single-phase grounding fault occurs downstream of the monitoring point, and no single-phase grounding fault occurs downstream of the monitoring point adjacent to the monitoring point, and the monitoring point is located on the feeder trunk line, if the single-line grounding fault is a permanent single-phase grounding fault or an intermittent single-phase grounding fault, the local switches at the two monitoring points are tripped, and the two monitoring points send fault location information to the master station respectively; If the single-phase grounding fault is an instantaneous single-phase grounding fault, the two monitoring points will send risk warning information to the master station respectively.

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