A Ground Fault Direction Detection Method and System Based on the Consistency of Phase Sequence Currents

Abstract

The present invention provides a grounding fault direction detection method and system based on the consistency of phase sequence currents. During the steady state process of the grounding fault, the effective value of the zero-sequence current and the effective value of the sudden change of the three-phase phase currents are obtained according to a preset period; calculate the ratio T1 of the maximum value in the effective values of the sudden changes of the three-phase phase currents to the effective value of the zero-sequence current, and calculate the ratio T2 of the maximum value to the minimum value in the effective values of the sudden changes of the three-phase phase currents; when T1 is greater than the first setting value and T2 is greater than the second setting value, it is determined that the fault direction is the first direction, otherwise, it is determined that the fault direction is the second direction. The present invention overcomes the problem that transient signals are difficult to accurately extract. When there is no zero-sequence current generated due to system load fluctuations, the consistency relationship between the sudden change of the phase current and the zero-sequence current is used as the fault direction criterion, reducing the influence of load fluctuations.

Description

Technical Field

[0001] The invention belongs to the technical field of distribution network fault detection and protection, and particularly relates to a grounding fault direction detection method and system based on phase sequence current consistency. Background Technique

[0002] The statements in this part only provide background technical information related to the present invention, and do not necessarily constitute prior art.

[0003] The small current grounding method is the main grounding method adopted by the distribution network. According to relevant statistical data, more than half of the substations supplying power to the distribution network adopt the ungrounded neutral point method, and about one-third are resonant grounding methods. In the past, the operating regulations of some regional power grids allowed the distribution network to operate with a grounding fault for a period of time to avoid user power outages. However, when the system operates with a grounding point for a long time, the overvoltage generated by the grounding fault is likely to cause the breakdown of weak insulation links in the non-fault phase, triggering a two-phase grounding short-circuit fault and expanding the accident; the grounding fault often causes cable trenches and cable tunnels to catch fire, switch cabinets to burn out, and busbars to short-circuit, resulting in large-scale power outages; in the event of a human electric shock accident, the harm to the electric shock victim cannot be terminated in time.

[0004] The development of social economy has put forward higher requirements for power supply safety and quality. The problem of distribution network grounding protection has attracted great attention in the industry. Many power grid companies have revised and formulated the operating regulations of the distribution network, requiring the solution of the protection problem of small current grounding faults and the rapid and nearby isolation of permanent grounding faults, which has brought new challenges to the handling of small current grounding system faults.

[0005] At present, for the single-phase grounding fault of the small current grounding system, the literature "Grounding Fault Direction Algorithm for Resonant Grounding System Using Only Zero-Sequence Current" proposes to use the power frequency component of the zero-sequence current as the polarization phasor of the zero-sequence voltage to further identify the fault direction. This method is only applicable to the resonant grounding system, and the ungrounded neutral point system cannot use this method to realize the fault direction discrimination; the literature "Distribution Network Single-Phase Grounding Fault Section Location Based on Phase Current Sudden Change" proposes a distribution network single-phase grounding fault section location method based on the phase current sudden change, but this method needs to use transient signals and is easily interfered. The low measurement accuracy of the current transformer is not conducive to accurately extracting transient signals, and the reliability is low. Summary of the Invention

[0006] In order to solve the above problems, the invention proposes a grounding fault direction detection method and system based on phase sequence current consistency. The invention overcomes the problem that transient signals are difficult to accurately extract. When the system load fluctuates, no zero-sequence current is generated. The consistency relationship between the phase current sudden change and the zero-sequence current is used as the fault direction criterion, reducing the influence of load fluctuations.

[0007] According to some embodiments, the present invention adopts the following technical solutions:

[0008] A grounding fault direction detection method based on the consistency of phase sequence current, applicable to a small current grounding system, includes the following steps:

[0009] During the steady state process of the grounding fault, obtain the effective value of the zero-sequence current and the effective value of the sudden change of the three-phase phase current according to a preset period;

[0010] Calculate the ratio T1 of the maximum value to the effective value of the zero-sequence current among the effective values of the sudden changes of the three-phase phase currents, and calculate the ratio T2 of the maximum value to the minimum value among the effective values of the sudden changes of the three-phase phase currents;

[0011] When T1 is greater than the first setting value and T2 is greater than the second setting value, determine that the fault direction is the first direction; otherwise, determine that the fault direction is the second direction.

[0012] As an alternative implementation, before obtaining the effective value of the zero-sequence current and the effective value of the sudden change of the three-phase phase current according to a preset period, it further includes:

[0013] Continuously obtain the effective value of the zero-sequence current at the detection point according to a preset period;

[0014] Compare the effective value of the zero-sequence current at the detection point with the setting value. When the effective value of the zero-sequence current at the detection point is greater than the setting value, determine that a grounding fault has occurred;

[0015] When the effective value of the zero-sequence current at the detection point is less than the setting value, re-obtain the effective value of the zero-sequence current at the detection point and compare the effective value of the zero-sequence current at the detection point with the setting value.

[0016] As a further limited implementation, the setting value is 0.5 - 1.5 A.

[0017] As an alternative implementation, when T1 is greater than the first setting value and T2 is greater than the second setting value, the specific process of determining that the fault direction is the first direction and otherwise determining that the fault direction is the second direction includes: Define that the fault direction is positive when the detection point is upstream of the fault point on the fault line, and the fault direction is negative when the detection point is downstream of the fault point on the fault line or on a sound line; When T1 is greater than the first setting value and T2 is greater than the second setting value, determine that the fault direction is positive, otherwise, determine that the fault direction is negative.

[0018] As an alternative implementation, for an ungrounded neutral system, the first setting value is greater than 1, and the second setting value is greater than 2.

[0019] As an alternative implementation, for a resonant grounding system, the first setting value is greater than 0.365, and the second setting value is greater than 1.15.

[0020] A ground fault direction detection system based on the consistency of phase sequence current, comprising:

[0021] A first acquisition module, configured to continuously acquire the effective value of zero-sequence current according to a preset period;

[0022] A second acquisition module, configured to acquire the effective value of zero-sequence current and the effective value of the sudden change of three-phase phase current according to a preset period during the steady state process of the ground fault;

[0023] A calculation module, configured to calculate the ratio T1 of the maximum value to the effective value of zero-sequence current among the effective values of the sudden changes of three-phase phase currents, and calculate the ratio T2 of the maximum value to the minimum value among the effective values of the sudden changes of three-phase phase currents;

[0024] A direction determination module, configured to determine that the fault direction is the first direction when T1 is greater than a first setting value and T2 is greater than a second setting value, otherwise, determine that the fault direction is the second direction.

[0025] As an alternative implementation, it further includes a ground fault determination module, configured to compare the effective value of zero-sequence current of the first acquisition module with a set value, and when the effective value of zero-sequence current is greater than the set value, determine that a ground fault has occurred and activate the second acquisition module.

[0026] A terminal device, comprising a processor and a computer-readable storage medium, the processor is used to implement each instruction; the computer-readable storage medium is used to store multiple instructions, and the instructions are adapted to be loaded and executed by the processor to perform the steps of the above method.

[0027] A small current grounding system, comprising detection devices arranged at each detection point, and the detection devices perform the steps of the above method to realize ground fault direction detection.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] The present invention overcomes the problem that transient signals are difficult to accurately extract. When the system load fluctuates, no zero-sequence current is generated. Using the consistency relationship between the sudden change of phase current and zero-sequence current as the fault direction criterion reduces the influence of load fluctuation.

[0030] The present invention does not require additional primary equipment on the line, and can indicate the fault direction only by using current information. It can still operate reliably for lines without voltage transformers installed. It can also avoid the measurement dead zone of current transformers during high-resistance faults, has strong common-mode interference resistance, and the detection points do not depend on communication with each other. Through time-delay coordination, multi-level protection can be achieved using local information.

[0031] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following specific preferred embodiments are given, and in conjunction with the accompanying drawings, the detailed description is as follows. Description of the Drawings

[0032] The accompanying drawings forming a part of this invention are used to provide a further understanding of the invention. The schematic embodiments and descriptions thereof of the invention are used to explain the invention and do not constitute an improper limitation of the invention.

[0033] Figure 1 It is a schematic diagram of the process flow of the grounding fault direction detection method for at least one embodiment of the present invention;

[0034] Figure 2 It is a flowchart of the process flow of the grounding fault direction detection method for at least one embodiment of the present invention;

[0035] Figure 3 It is a Matlab / Simulink simulation model for at least one embodiment of the present invention;

[0036] Figures 4(a)-(c) are schematic diagrams of simulation waveforms when a fault point in an ungrounded neutral system is grounded through resistors of 100Ω / 1500Ω / 4000Ω;

[0037] Figures 5(a)-(c) are schematic diagrams of simulation waveforms when a fault point in a resonant grounding system is grounded through resistors of 100Ω / 1500Ω / 4000Ω. Detailed implementation manners

[0038] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed descriptions are all illustrative and are intended to provide a further description of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0040] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary implementation manners of the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] Embodiment 1:

[0042] For ease of understanding, please refer to Figure 1 , the method for detecting the grounding fault direction of a small current grounding system based on the phase sequence current consistency provided by the present invention includes the following steps:

[0043] S1. Each detection point on the line continuously detects the effective value of the zero-sequence current 3I according to a preset period 01 ;

[0044] At S2, the detection points on the line during the steady-state fault process acquire the effective value of the zero-sequence current 3I at a preset period 02 and the effective values of the sudden changes in the three-phase phase currents ΔI A , ΔI B , ΔI C ;

[0045] It should be noted that, as Figure 2 shown, during the steady-state fault process, the detection points on the line acquire the effective value of the zero-sequence current 3I at a preset period 02 and the effective values of the sudden changes in the three-phase phase currents ΔI A , ΔI B , ΔI C It is also necessary to determine whether a ground fault has occurred on the line before that. Only when a ground fault has occurred on the line, it is necessary to further acquire the effective value of the zero-sequence current 3I at a preset period at the detection points on the line during the steady-state fault process 02 and the effective values of the sudden changes in the three-phase phase currents ΔI A , ΔI B , ΔI C ;

[0046] The method for determining the line ground fault is that the setting value I set is set to 0.5 - 1.5 A. If the effective value of the zero-sequence current 3I continuously detected at each detection point on the line at a preset period 01 exceeds the setting value I set , it is determined that a ground fault has occurred in the grounding system. If so, continue with the subsequent steps. If not, re-determine until it is satisfied and then execute the subsequent steps;

[0047] At S3, the detection points on the line calculate the maximum value ΔI A , ΔI B , ΔI C among the effective values of the sudden changes in the three-phase phase currents ΔI max and the ratio T1 of the effective value of the zero-sequence current 3I 02 . Calculate the maximum value ΔI A , ΔI B , ΔI C among the effective values of the sudden changes in the three-phase phase currents ΔI max and the ratio T2 of the minimum value ΔI A , ΔI B , ΔI C among the sudden changes in the three-phase phase currents ΔI min ;

[0048] At S4, it is defined that the fault direction is positive when the detection point is upstream of the fault point on the fault line, and the fault direction is negative when the detection point is downstream of the fault point on the fault line or on a healthy line; T1 is greater than the setting value Rset and T2 is greater than the setting value K set When this is the case, it is determined that the fault direction is positive; otherwise, it is determined that the fault direction is negative;

[0049] It should be noted that for an ungrounded neutral system, the setting value R set > 1, and the setting value K set > 2; for a resonant grounded system, the setting value R set > 0.365, and the setting value K set > 1.15.

[0050] In this embodiment, the characteristics of the sudden change in the phase current of the faulty line upstream and downstream of the fault point and the sound line after a single-phase grounding fault occurs in the small current grounding system are analyzed, and a fault direction method based on the consistency relationship between the sudden change in phase current and zero-sequence current is proposed. The present invention overcomes the problem that transient signals are difficult to accurately extract. When the system load fluctuates, no zero-sequence current is generated. Using the consistency relationship between the sudden change in phase current and zero-sequence current as the fault direction criterion reduces the influence of load fluctuations.

[0051] This method does not require additional primary equipment on the line, and can indicate the fault direction only by using current information. It can still operate reliably for lines without voltage transformers installed. It can also avoid the measurement dead zone of current transformers during high-resistance faults, has strong anti-common-mode interference ability, and does not rely on communication between detection points. Through time-delay coordination, multi-level protection can be achieved using local information.

[0052] Please refer to Figure 3 Figures 4(a)-(c), Figures 5(a)-(c) and Tables 1 and 2. The following will further introduce in detail a method for detecting the grounding fault direction of a small current grounding system based on phase sequence current consistency in this embodiment in combination with typical ungrounded neutral systems and resonant grounded systems.

[0053] As Figure 3 shown, a simulation model of a 10 kV small current grounding system is built using the simulink library in Matlab. This system has a total of four outgoing lines (L1 to L4), where L1, L2, and L3 are overhead-cable hybrid lines, and L4 is a cable line. Two detection points are set on line L4. The distances from detection points P1 and P2 to the bus are 2 km and 6 km respectively, and the fault point f1 is set at a position 2 km from detection point P1; two detection points are set on line L1. Detection points P3 and P4 are located 3 km from the bus and 5.5 km from the bus respectively. The over-compensation degree of the arc suppression coil is 10%. When switch K1 is open, it is an ungrounded neutral system, and when switch K1 is closed, it is a resonant grounded system.

[0054] The zero-sequence resistance of the cable line is set to 2.7 Ω / km, the zero-sequence inductance is 1.109 mH / km, the zero-sequence capacitance is 0.276 μF / km, the positive-sequence resistance is 0.27 Ω / km, the positive-sequence inductance is 0.255 mH / km, and the positive-sequence capacitance is 0.376 μF / km; the zero-sequence resistance of the overhead line is set to 0.32 Ω / km, the zero-sequence inductance is 3.56 mH / km, the zero-sequence capacitance is 0.0062 μF / km, the positive-sequence resistance is 0.17 Ω / km, the positive-sequence inductance is 1.017 mH / km, and the positive-sequence capacitance is 0.155 μF / km.

[0055] Taking this as an example, the above system is used to verify the effectiveness of the method described in the present invention. The specific implementation steps are as follows:

[0056] Step 1: When the line is operating normally, each detection point on the line continuously detects the effective value of the zero-sequence current 3I according to a preset period (1 cycle in this example). 01 The effective value of the zero-sequence current 3I 01 is compared with the setting value I set . In this example, the setting value I set is set to 0.75 A. If the effective value of the zero-sequence current 3I 01 exceeds the setting value I set , it is determined that a grounding fault has occurred in the grounding system. If so, the subsequent steps are continued. If not, the judgment is repeated until it is satisfied and then the subsequent steps are executed; as shown in Table 1, through simulation, an A-phase grounding fault occurs at f1 in the non-grounded neutral system. At this time, only the detection point P1 is located upstream of the fault point on the fault line, and the detection points P2, P3, and P4 are all located downstream of the fault point on the fault line or on the sound line. From Table 1 and Figure 3 it can be seen that when the transition resistance is 100 Ω / 1500 Ω, the effective value of the zero-sequence current 3I detected by the detection points P1, P2, P3, and P4 01 > 0.75 A, and the detection points P1, P2, P3, and P4 all judge that a grounding fault has occurred, and step 2 is executed; when the transition resistance is 4000 Ω, only the detection point P1 detects that the effective value of the zero-sequence current 3I 01 > 1 A, the detection point P1 judges that a grounding fault has occurred, step 2 is executed, and the detection points P2, P3, and P4 are rejudged until it is satisfied and then the subsequent steps are executed.

[0057] As shown in Table 2, through simulation, an A-phase grounding fault occurs at f1 in the resonant grounding system. At this time, only the detection point P1 is located upstream of the fault point on the fault line, and the detection points P2, P3, and P4 are all located downstream of the fault point on the fault line or on the sound line. From Table 1 and Figure 3 it can be seen that when the transition resistance is 100 Ω / 1500 Ω / 4000 Ω, the effective value of the zero-sequence current 3I detected by the detection points P1, P2, P3, and P4 01> 0.75A, it is determined that a ground fault has occurred at detection points P1, P2, P3, and P4, and step two is executed.

[0058] Step two: During the steady-state process of the fault in the ungrounded neutral system, the detection points on the line obtain the effective value of the zero-sequence current 3I0 and the effective values of the sudden changes in the three-phase phase currents ΔI at a preset period (3 cycles in this example). A 、ΔI B 、ΔI C According to Table 1 and Figure 3 it can be seen that when the transition resistance is 100Ω / 1500Ω, during the steady-state process of the fault, the effective values of the zero-sequence current and the effective values of the sudden changes in the three-phase phase currents ΔI at detection points P1, P2, P3, and P4 A 、ΔI B 、ΔI C As shown in Table 1, when the transition resistance is 4000Ω, during the steady-state process of the fault, the effective value of the zero-sequence current at detection point P1 and the effective values of the sudden changes in the three-phase phase currents ΔI A 、ΔI B 、ΔI C As shown in Table 1, step three is executed;

[0059] During the steady-state process of the fault in the resonant grounded system, the detection points on the line obtain the effective value of the zero-sequence current 3I0 and the effective values of the sudden changes in the three-phase phase currents ΔI at a preset period (3 cycles in this example). A 、ΔI B 、ΔI C According to Table 2 and Figure 4, when the transition resistance is 100Ω / 1500Ω / 4000Ω, during the steady-state process of the fault, the effective values of the zero-sequence current and the effective values of the sudden changes in the three-phase phase currents ΔI at detection points P1, P2, P3, and P4 A 、ΔI B 、ΔI C As shown in Table 2, step three is executed;

[0060] Step three: In the ungrounded neutral system, when the transition resistance is 100Ω / 1500Ω, as shown in Table 1, for the line detection points P1, P2, P3, and P4, calculate the ratio T1 of the maximum value ΔI among the effective values of the sudden changes in the three-phase phase currents ΔI A 、ΔI B 、ΔI C during the steady-state process of the fault to the effective value of the zero-sequence current 3I max Calculate the ratio of the maximum value ΔI among the effective values of the sudden changes in the three-phase phase currents ΔI 02 、ΔI A 、ΔI B 、ΔI C during the steady-state process of the fault to the sudden change in the three-phase phase current ΔI max 、ΔI A 、ΔI B 、ΔIC The minimum value ΔI min The ratio T2. When the transition resistance is 4000Ω, as shown in Table 1, the effective values of the sudden changes in the three-phase phase currents ΔI A , ΔI B , ΔI C The maximum value ΔI max And the effective value of the zero-sequence current 3I 02 The ratio T1. The effective values of the sudden changes in the three-phase phase currents ΔI A , ΔI B , ΔI C The maximum value ΔI max And the sudden changes in the three-phase phase currents ΔI A , ΔI B , ΔI C The minimum value ΔI min The ratio T2.

[0061] In a resonant grounded system, when the transition resistance is 100Ω / 1500Ω / 4000Ω, as shown in Table 2, the effective values of the sudden changes in the three-phase phase currents ΔI A , ΔI B , ΔI C The maximum value ΔI max And the effective value of the zero-sequence current 3I 02 The ratio T1. The effective values of the sudden changes in the three-phase phase currents ΔI A , ΔI B , ΔI C The maximum value ΔI max And the sudden changes in the three-phase phase currents ΔI A , ΔI B , ΔI C The minimum value ΔI min The ratio T2.

[0062] Step 4: Define that the fault direction is positive when the detection point is upstream of the fault point on the faulty line, and the fault direction is negative when the detection point is downstream of the fault point on the faulty line or on a sound line; when T1 is greater than the setting value R set And T2 is greater than the setting value K set , judge that the fault direction is positive, otherwise, judge that the fault direction is negative.

[0063] In this example, for an ungrounded neutral system, the setting value R set = 1.1, the setting value K set = 3, for a resonant grounded system, the setting value R set = 0.37, the setting value K set = 1.2.

[0064] In an ungrounded neutral system, as shown in Table 1, when the transition resistance is 100 Ω / 1500 Ω, the fault direction at the line detection point P1 is judged to be positive, and the fault directions at the line detection points P2, P3, and P4 are judged to be negative. When the transition resistance is 4000 Ω, the fault direction at the line detection point P1 is judged to be positive.

[0065] In a resonant grounded system, as shown in Table 2, when the transition resistance is 100 Ω / 1500 Ω / 4000 Ω, the fault direction at the line detection point P1 is judged to be positive, and the fault directions at the line detection points P2, P3, and P4 are judged to be negative.

[0066] Table 1 Simulation results of ungrounded neutral system under different transition resistances

[0067]

[0068]

[0069] Table 2 Simulation results of resonant grounded system under different transition resistances

[0070]

[0071] Embodiment 2:

[0072] A small current grounding system fault direction detection system based on phase sequence current consistency includes:

[0073] A first acquisition module for acquiring the effective value 3I of the zero-sequence current at the detection point of the line in real time according to a preset period 01 ;

[0074] A second acquisition module for acquiring the effective value 3I of the zero-sequence current and the effective values ΔI of the sudden changes of the three-phase phase currents at the detection point of the line in the steady state process of the fault according to a preset period 02 and ΔI A , ΔI B , ΔI C ;

[0075] A calculation module for calculating the ratio T1 of the maximum value ΔI among the effective values ΔI of the sudden changes of the three-phase phase currents A , ΔI B , ΔI C to the effective value 3I of the zero-sequence current, and calculating the maximum value ΔI among the effective values ΔI of the sudden changes of the three-phase phase currents max to the sudden change ΔI of the three-phase phase currents 02 , ΔI A , ΔI B , ΔI C and the maximum value ΔI max to the sudden changes ΔI of the three-phase phase currents A , ΔI B, ΔI C The minimum value of ΔI min The ratio T2;

[0076] A position determination module for determining whether T1 is greater than a set value R set And whether T2 is greater than a set value K set , if so, determine that the fault direction is positive, otherwise, determine that the fault direction is negative;

[0077] In this embodiment, the above system further includes:

[0078] A line fault determination module for determining the effective value 3I of the zero-sequence current at the detection point of the line 01 Whether it satisfies 3I 01 ≥I set , if so, activate the second acquisition module, if not, re-determine until it is satisfied and then activate the second acquisition module;

[0079] In some embodiments, the above system further includes:

[0080] A type acquisition module for acquiring the system type of the grounding system, and the system type includes an ungrounded system and a resonant grounding system;

[0081] Embodiment Three:

[0082] A small current grounding system grounding fault direction detection device based on phase sequence current consistency, the device includes a processor and a memory:

[0083] The memory is used to store a computer program and send the instructions of the computer program to the processor;

[0084] The processor executes the grounding fault direction method provided in Embodiment One according to the instructions of the computer program.

[0085] Embodiment Four:

[0086] A small current grounding system includes detection devices arranged at each detection point, and the detection devices execute the grounding fault direction method provided in Embodiment One to implement grounding fault direction detection.

[0087] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0088] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices produce a means for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or a means for implementing the functions specified in one block or multiple blocks.

[0089] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including an instruction means that implements the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or a means for implementing the functions specified in one block or multiple blocks.

[0090] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operating steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or a means for implementing the functions specified in one block or multiple blocks.

[0091] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0092] Although the specific implementation manners of the present invention are described above in conjunction with the accompanying drawings, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that based on the technical solutions of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A grounding fault direction detection method based on the consistency of phase sequence current, characterized in that: It includes the following steps: During the steady-state process of the ground fault, obtain the effective value of the zero-sequence current and the effective value of the sudden change of the three-phase phase currents according to a preset period; Calculate the ratio T1 of the maximum value to the effective value of the zero-sequence current among the effective values of the sudden changes of the three-phase phase currents, and calculate the ratio T2 of the maximum value to the minimum value among the effective values of the sudden changes of the three-phase phase currents; When T1 is greater than the first setting value and T2 is greater than the second setting value, determine that the fault direction is the first direction; otherwise, determine that the fault direction is the second direction.

2. The ground fault direction detection method based on the phase sequence current consistency as described in claim 1, characterized in that: Before obtaining the effective value of the zero-sequence current and the effective value of the sudden change of the three-phase phase currents according to a preset period, it further includes: Continuously obtain the effective value of the zero-sequence current at the detection point according to a preset period; Compare the effective value of the zero-sequence current at the detection point with the setting value. When the effective value of the zero-sequence current at the detection point is greater than the setting value, determine that a ground fault has occurred; When the effective value of the zero-sequence current at the detection point is less than the setting value, re-obtain the effective value of the zero-sequence current at the detection point, and compare the effective value of the zero-sequence current at the detection point with the setting value.

3. The method for detecting the grounding fault direction based on the phase sequence current consistency according to claim 2, characterized in that: The setting value is 0.5 - 1.5 A.

4. A grounding fault direction detection method based on the consistency of phase sequence current as described in claim 1, characterized in that: The specific process of determining the fault direction when T1 is greater than the first setting value and T2 is greater than the second setting value includes: Define that the fault direction is positive when the detection point is upstream of the fault point on the fault line, and the fault direction is negative when the detection point is downstream of the fault point on the fault line or on a sound line; When T1 is greater than the first setting value and T2 is greater than the second setting value, determine that the fault direction is positive; otherwise, determine that the fault direction is negative.

5. A ground fault direction detection method based on the consistency of phase sequence current as described in claim 1, characterized in that: For an ungrounded neutral system, the first setting value is greater than 1, and the second setting value is greater than 2.

6. A ground fault direction detection method based on the consistency of phase sequence current as described in claim 1, characterized in that: For a resonant grounding system, the first setting value is greater than 0.365, and the second setting value is greater than 1.

15.

7. A grounding fault direction detection system based on the consistency of phase sequence current, characterized in that: It includes: The first acquisition module is used to continuously obtain the effective value of the zero-sequence current according to a preset period; The second acquisition module is used to obtain the effective value of the zero-sequence current and the effective value of the sudden change of the three-phase phase currents according to a preset period during the steady-state process of the ground fault; The calculation module is used to calculate the ratio T1 of the maximum value to the effective value of the zero-sequence current among the effective values of the sudden changes of the three-phase phase currents, and calculate the ratio T2 of the maximum value to the minimum value among the effective values of the sudden changes of the three-phase phase currents; The direction determination module is used to determine that the fault direction is the first direction when T1 is greater than the first setting value and T2 is greater than the second setting value; otherwise, determine that the fault direction is the second direction.

8. The ground fault direction detection system based on the phase sequence current consistency according to claim 7, characterized in that: It further includes a ground fault determination module, which is used to compare the effective value of the zero-sequence current of the first acquisition module with the setting value. When the effective value of the zero-sequence current is greater than the setting value, determine that a ground fault has occurred and activate the second acquisition module.

9. A terminal device, characterized in that: It includes a processor and a computer-readable storage medium. The processor is used to implement each instruction; the computer-readable storage medium is used to store multiple instructions, and the instructions are suitable for being loaded and executed by the processor to perform the steps of the method described in any one of claims 1 - 6.

10. A small current grounding system, characterized in that: It includes detection devices arranged at each detection point, and the detection devices perform the steps of the method described in any one of claims 1 - 6 to achieve ground fault direction detection.

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