Ground fault identification algorithm based on feeder terminal
By fusing zero-sequence reactive analysis and phase current mutation detection in ground fault detection, combined with transient characteristics and current information, the difficult identification problems in the prior art are solved, and higher accuracy and response speed are achieved. Ground fault detection for complex working conditions.
Patent Information
- Application Number
- CN202411512058.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-28
- Publication Date
- 2025-01-10
AI Technical Summary
The existing ground fault detection methods are difficult to identify under complex operating conditions, especially in high-resistance grounding or non-pure metal faults, which have poor accuracy and stability, prone to missed or false alarms, and cannot fully utilize multi-dimensional feature information.
Using a ground fault identification algorithm based on feeder terminals that integrates zero-sequence reactive analysis and phase current mutation detection, the ground fault identification algorithm is determined by combining transient zero-sequence reactive characteristics and phase current mutation information, and improving identification accuracy and adaptability.
It improves the accuracy and response speed of ground fault identification, reduces false alarms and missed reports, realizes online real-time monitoring and diagnosis, is suitable for actual engineering environments, and reduces system maintenance costs.
Smart Images
Figure CN119291385A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of ground fault detection, and in particular to a ground fault identification algorithm based on a feeder terminal. Background Art
[0002] The statements in this section merely provide background technical information related to the present application and do not necessarily constitute prior art.
[0003] In the distribution network, ground faults account for about 80% of the total faults. Most of my country's distribution networks use a small current grounding system (neutral point is not grounded, neutral point is grounded through arc suppression coil). In traditional ground fault detection methods, such as the steady-state component method and the transient component method, they usually rely on a single parameter or method. The steady-state component method is suitable for the neutral point ungrounded system. Although the transient component method is not affected by the neutral point grounding method, under complex working conditions, the line transient characteristics continue for a very short time and the harmonic content is large. Therefore, they all have certain limitations. The transient component method may be affected by factors such as noise and signal distortion in practical applications, especially in the case of high-resistance grounding or non-pure metallic grounding faults. The steady-state component method has certain advantages in frequency analysis, but it is not effective for faults with fast changes or weak amplitudes, and is sensitive to system stability and parameter changes, making it difficult to deal with complex fault forms. The above methods cannot fully utilize the multi-dimensional feature information of line operation, which can easily lead to low recognition accuracy, and even omissions or false alarms.
[0004] In view of this, it is necessary to provide a ground fault identification algorithm based on the fusion of zero-sequence reactive power analysis and phase current mutation at the feeder terminal to solve the above technical problems. Summary of the invention
[0005] Based on this, in order to solve the above technical problems, the present application provides a ground fault identification algorithm based on feeder terminals.
[0006] The technical solution adopted by this application to solve the problems existing in the prior art is:
[0007] This application proposes a ground fault identification algorithm based on feeder terminal, which includes the following steps:
[0008] Step 1: Determine whether the ground fault is an internal fault or an external fault by using a fusion zero-sequence reactive power analysis algorithm based on the feeder terminal;
[0009] Step 2: Determine whether the ground fault is an internal fault or an external fault through the distribution line ground fault identification algorithm based on phase current mutation detection;
[0010] Step 3: Make a comprehensive judgment to determine whether the fault is within or outside the area.
[0011] Preferably,
[0012] The feeder terminal-based fused zero-sequence reactive power analysis algorithm comprises the following steps:
[0013] Step 1: Set the terminal sampling rate to collect line signals;
[0014] Step 2: Zero-sequence reactive power direction detection, including the following steps:
[0015] Step 1: Continuously detect the collected zero-pressure and zero-current instantaneous values, and subtract the sampling value corresponding to the previous cycle from the current cycle sampling value;
[0016] Step 2: When the zero-sequence voltage mutations at three consecutive points all exceed the preset value u_val, the mutation waveforms of the two cycles before and after the mutation are copied to the calculation buffer;
[0017] Step 3: Determine whether the zero-sequence current effective value is greater than the preset value i_val.
[0018] If it is less than the preset value i_val, the calculation buffer is cleared and the process returns to step 1;
[0019] If it is greater than the preset value i_val, go to step 4;
[0020] Step 4: Further determine the average mutation amount average between the effective value of a cycle 2 starting from the mutation point and the previous two cycles 1 cycle2-cycle1 Whether it exceeds the preset value u_val, when average cycle2-cycle1 When it exceeds the preset value u_val, it is judged as exceeded and goes to step 5, otherwise it returns to step 1;
[0021] Step 5: Calculate the zero-sequence reactive average effective value Qu0i0_average within the time interval time_setting. If Qu0i0_average is a positive number and its absolute value is greater than the set value val_setting, it is judged as an internal fault; if it is a negative number and its absolute value is greater than the set value val_setting, it is judged as an external fault.
[0022] Preferably, the step 4 further includes: further determining the average mutation amount average of the effective value of a cycle cycle2 starting from the mutation point and the previous cycle cycle0 cycle2-cycle0 Whether it exceeds the preset value u_val, when average cycle2-cycle0 When it exceeds the preset value u_val, it is judged as exceeded.
[0023] Preferably,
[0024] The terminal sampling rate is above 8 kHz.
[0025] Preferably, the distribution line ground fault identification algorithm based on phase current mutation detection comprises the following steps:
[0026] Step 1: Continuously detect the collected zero-voltage and zero-current instantaneous values and the three-phase current recording data;
[0027] Step 2: When the system detects an abnormal zero-current mutation signal, the three-phase current recording data is copied to the calculation buffer, and the difference between the previous cycle and the next cycle of the mutation point is calculated respectively, and the average value of the three-phase current mutation amount val_avg_before before the mutation and the average value of the three-phase current mutation amount val_avg_after after the mutation are obtained respectively;
[0028] Step 3: Obtain the maximum mutation amount in the three phases before and after mutation:
[0029] max_val_before=MAX(val_Ia_before, val_Ib_before, val_Ic_before)
[0030] max_val_after=MAX(val_Ia_after, val_Ib_after, val_Ic_after)
[0031] in:
[0032] max_val_before is the maximum mutation amount in the three phases before the mutation; max_val_after is the maximum mutation amount in the three phases after the mutation;
[0033] val_Ia_before is the current mutation amount of phase A before the mutation; val_Ib_before is the current mutation amount of phase B before the mutation;
[0034] val_Ic_before is the current mutation amount of phase C before the mutation;
[0035] val_Ia_after is the current mutation amount of phase A after the mutation; val_Ib_after is the current mutation amount of phase B after the mutation.
[0036] val_Ic_after is the C phase current mutation amount after the mutation;
[0037] Step 4: Calculate the three-phase current imbalance before and after the mutation:
[0038]
[0039] in:
[0040] before_factor is the unbalance degree of the three-phase current before the mutation; after_factor is the unbalance degree of the three-phase current after the mutation;
[0041] Step 5:
[0042] Take the largest three-phase unbalance factor before and after the mutation = MAX (before_factor, after_factor). If it is greater than a preset value, it is determined that the ground fault is an internal fault. If it is less than the preset value, the buffer is cleared and the process returns to step 1.
[0043] Preferably,
[0044] In the step 2:
[0045]
[0046] Preferably,
[0047] The internal fault refers to the fault occurring inside the power system protected by the relay protection.
[0048] The out-of-zone fault refers to a fault that occurs outside the scope of the power system protected by the relay protection.
[0049] Preferably,
[0050] In the third step:
[0051] Fusion judgment includes the following steps:
[0052] Step 1: Set the ground sensitivity constant;
[0053] Step 2: Determine the ground sensitivity value, where:
[0054] When the grounding sensitivity value is 0 or 2, the grounding fault is judged to be an intra-zone fault;
[0055] When the ground sensitivity value is 1, if:
[0056] When the ground faults are judged to be internal faults by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal and the distribution line ground fault identification algorithm based on phase current mutation detection, the ground fault is judged to be an internal fault; otherwise, it is an external fault;
[0057] When the ground fault is judged as an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal, but the ground fault is judged as an external fault by the distribution line ground fault identification algorithm based on phase current mutation detection, more stringent ground characteristic parameters are preset to further judge the various characteristic significances of the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal. If the ground fault is judged as an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal after more stringent ground characteristic parameters are preset, the ground fault is judged to be an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal; otherwise, it is an external fault.
[0058] The grounding fault is judged to be an out-of-zone fault by the fused zero-sequence reactive power analysis algorithm based on the feeder terminal, but when the grounding fault is judged to be an in-zone fault by the distribution line grounding fault identification algorithm based on phase current mutation detection, more stringent grounding characteristic parameters are preset to further judge the various feature significances of the distribution line grounding fault identification algorithm based on phase current mutation detection. If the grounding fault is judged to be an in-zone fault by the distribution line grounding fault identification algorithm based on phase current mutation detection after more stringent grounding characteristic parameters are preset, the grounding fault is judged to be an in-zone fault by the distribution line grounding fault identification algorithm based on phase current mutation detection, then the grounding fault is judged to be an in-zone fault; otherwise, it is an out-of-zone fault.
[0059] Preferably,
[0060] When the ground fault is judged as an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal, but the ground fault is judged as an external fault by the distribution line ground fault identification algorithm based on phase current mutation detection, the method of presetting more stringent ground characteristic parameters includes:
[0061] Lower the preset value u_val or lower the preset value i_val.
[0062] Preferably,
[0063] When the ground fault is judged as an out-of-zone fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal, but the ground fault is judged as an in-zone fault by the distribution line ground fault identification algorithm based on phase current mutation detection, the method of presetting more stringent ground characteristic parameters includes:
[0064] Increase the terminal sampling rate.
[0065] Compared with the prior art, the beneficial effects of this application are:
[0066] 1. The present invention aims to overcome the shortcomings of the prior art and proposes a grounding algorithm that integrates zero-sequence reactive power analysis and phase current mutation. By comprehensively analyzing multi-dimensional information such as transient zero-sequence reactive power characteristics and phase current mutation, the accuracy and adaptability of fault identification can be improved. Compared with a single method, the fusion algorithm can more comprehensively and accurately respond to different types of grounding faults and operating conditions, thereby avoiding the limitations of a single method and reducing the possibility of false alarms and missed alarms. In addition, the present invention is also based on the feeder terminal and is committed to designing algorithms suitable for actual engineering projects, and solving challenges in data acquisition, processing, and real-time performance to ensure its effective application in power systems.
[0067] 2. Stronger fault identification capability: Compared with the traditional transient component method and steady-state component method, the present invention adopts the method of zero-sequence reactive power analysis and phase current mutation detection, which can more accurately identify ground faults and comprehensively utilize two different types of information, thereby improving the comprehensiveness and comprehensiveness of fault diagnosis.
[0068] 3. Faster fault response speed: The present invention performs fault diagnosis based on feeder terminal data, without offline recording and subsequent offline processing, so it can achieve online real-time monitoring and diagnosis, greatly improving the fault response speed. Compared with traditional methods, it can find and locate faults faster, help to take timely measures to repair them, and reduce the impact of faults on the power system.
[0069] 4. Cost saving: The feeder terminal data on which the present invention is based is usually already deployed in the power system, and no additional sensors or equipment need to be installed, thus saving costs. In addition, the algorithm is relatively simple to implement, easy to deploy and maintain, which also helps to reduce system maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0070] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.
[0071] Figure 1 This is an overall logic flow chart of a ground fault identification algorithm based on a feeder terminal of the present application.
[0072] Figure 2 for Figure 1 The overall flow chart of fusion judgment in a ground fault identification algorithm based on feeder terminal in this application,
[0073] Figure 3 for Figure 1 In the present application, a ground fault identification algorithm based on feeder terminal is used to detect the fault in the area when the zero-sequence reactive power direction is detected, and the detection curve diagram of each parameter is shown.
[0074] Figure 4 for Figure 1 A ground fault identification algorithm based on a feeder terminal in the present application is a curve diagram of various parameters when it is determined to be an out-of-zone fault during zero-sequence reactive power direction detection. DETAILED DESCRIPTION
[0075] The present application is further described below in conjunction with the accompanying drawings and embodiments.
[0076] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.
[0077] In the present disclosure, terms such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "side", "bottom" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present disclosure, and do not specifically refer to any part or element in the present disclosure and should not be understood as limitations on the present disclosure.
[0078] A ground fault identification algorithm based on a feeder terminal of the present application comprises the following steps:
[0079] Step 1: Determine whether the ground fault is an internal fault or an external fault by using a fusion zero-sequence reactive power analysis algorithm based on the feeder terminal;
[0080] Step 2: Determine whether the ground fault is an internal fault or an external fault through the distribution line ground fault identification algorithm based on phase current mutation detection;
[0081] Step 3: Make a comprehensive judgment to determine whether the fault is within or outside the area.
[0082] refer to Figure 1 , the feeder terminal-based fusion zero-sequence reactive power analysis algorithm comprises the following steps:
[0083] Step 1: Set the terminal sampling rate to collect line signals;
[0084] Step 2: Zero-sequence reactive power direction detection, including the following steps:
[0085] Step 1: Continuously detect the collected zero-pressure and zero-current instantaneous values, and subtract the sampling value corresponding to the previous cycle from the current cycle sampling value;
[0086] Step 2: When the zero-sequence voltage mutations at three consecutive points all exceed the preset value u_val, the mutation waveforms of the two cycles before and after the mutation are copied to the calculation buffer;
[0087] Step 3: Determine whether the zero-sequence current effective value is greater than the preset value i_val.
[0088] If it is less than the preset value i_val, the calculation buffer is cleared and the process returns to step 1;
[0089] If it is greater than the preset value i_val, go to step 4;
[0090] Step 4: Further determine the average mutation amount average between the effective value of a cycle 2 starting from the mutation point and the previous two cycles 1 cycle2-cycle1 Whether it exceeds the preset value u_val, when average cyc1e2-cycle1 When it exceeds the preset value u_val, it is judged as exceeded and goes to step 5, otherwise it returns to step 1;
[0091] Step 5: Calculate the average effective value Qu0i0_average of the zero-sequence reactive power within the time interval time_setting. If Qu0i0_average is a positive number and its absolute value is greater than the set value val_setting, it is judged as an internal fault; if it is a negative number and its absolute value is greater than the set value val_setting, it is judged as an external fault.
[0092] The step 4 also includes: further determining the average mutation amount average of a cycle cycle 2 starting from the mutation point and the effective value of the previous cycle cycle 0 cycle2-cycle0 Whether it exceeds the preset value u_val, when
[0093] average cycle2-cycle0 When it exceeds the preset value u_val, it is judged as exceeded.
[0094] In some embodiments, the terminal sampling rate is above 8 kHz.
[0095] The distribution line grounding fault identification algorithm based on phase current mutation detection is preset before the terminal is installed according to whether there is a zero-current transformer. If there is a zero-current transformer, it is directly collected. If there is no zero-current transformer, the zero-sequence current is synthesized by three-phase current.
[0096] refer to Figure 1 The distribution line ground fault identification algorithm based on phase current mutation detection includes the following steps:
[0097] Step 1: Continuously detect the collected zero-voltage and zero-current instantaneous values and the three-phase current recording data;
[0098] Step 2: When the system detects an abnormal zero-current mutation signal, the three-phase current recording data is copied to the calculation buffer, and the difference between the previous cycle and the next cycle of the mutation point is calculated respectively, and the average value of the three-phase current mutation amount val_avg_before before the mutation and the average value of the three-phase current mutation amount val_avg_after after the mutation are obtained respectively;
[0099] Step 3: Obtain the maximum mutation amount in the three phases before and after mutation:
[0100] max_val_before=MAX(val_Ia_before, val_Ib_before, val_Ic_before)
[0101] max_val_after=MAX(val_Ia_after, val_Ib_after, val_Ic_after)
[0102] in:
[0103] max_val_before is the maximum mutation amount in the three phases before the mutation; max_val_after is the maximum mutation amount in the three phases after the mutation;
[0104] val_Ia_before is the current mutation amount of phase A before the mutation; val_Ib_before is the current mutation amount of phase B before the mutation;
[0105] val_Ic_before is the current mutation amount of phase C before the mutation;
[0106] val_Ia_after is the current mutation amount of phase A after the mutation; val_Ib_after is the current mutation amount of phase B after the mutation.
[0107] val_Ic_after is the C phase current mutation amount after the mutation;
[0108] Step 4: Calculate the three-phase current imbalance before and after the mutation:
[0109]
[0110]
[0111] in:
[0112] before_factor is the unbalance degree of the three-phase current before the mutation; after_factor is the unbalance degree of the three-phase current after the mutation;
[0113] Step 5:
[0114] Take the largest three-phase unbalance factor before and after the mutation = MAX (before_factor, after_factor). If it is greater than a preset value, it is determined that the ground fault is an internal fault. If it is less than the preset value, the buffer is cleared and the process returns to step 1.
[0115] In the step 2:
[0116]
[0117] In this application, an in-zone fault refers to a fault that occurs inside the power system that the relay protection is responsible for protecting; an out-of-zone fault refers to a fault that occurs outside the scope of the power system that the relay protection is responsible for protecting.
[0118] refer to Figure 2 In this application, the fusion judgment includes the following steps:
[0119] Step 1: Set the ground sensitivity constant;
[0120] Setting: When any of the results of the ground fault determined by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal and the distribution line ground fault identification algorithm based on phase current mutation detection is an internal fault, the ground sensitivity setting value is 0;
[0121] When all the results of the ground faults determined by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal and the distribution line ground fault identification algorithm based on phase current mutation detection are internal faults, the ground sensitivity setting value is 2;
[0122] When the results of the ground fault determined by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal and the distribution line ground fault identification algorithm based on phase current mutation detection are both considered to be an internal fault, the ground sensitivity setting value is 1;
[0123] Step 2: Determine the ground sensitivity value, where:
[0124] When the grounding sensitivity value is 0 or 2, the grounding fault is judged to be an intra-zone fault;
[0125] When the ground sensitivity value is 1, if:
[0126] When the ground faults are judged to be internal faults by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal and the distribution line ground fault identification algorithm based on phase current mutation detection, the ground fault is judged to be an internal fault; otherwise, it is an external fault;
[0127] When the ground fault is judged as an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal, but the ground fault is judged as an external fault by the distribution line ground fault identification algorithm based on phase current mutation detection, more stringent ground characteristic parameters are preset to further judge the various characteristic significances of the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal. If the ground fault is judged as an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal after more stringent ground characteristic parameters are preset, the ground fault is judged to be an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal; otherwise, it is an external fault.
[0128] The grounding fault is judged to be an out-of-zone fault by the fused zero-sequence reactive power analysis algorithm based on the feeder terminal, but when the grounding fault is judged to be an in-zone fault by the distribution line grounding fault identification algorithm based on phase current mutation detection, more stringent grounding characteristic parameters are preset to further judge the various feature significances of the distribution line grounding fault identification algorithm based on phase current mutation detection. If the grounding fault is judged to be an in-zone fault by the distribution line grounding fault identification algorithm based on phase current mutation detection after more stringent grounding characteristic parameters are preset, the grounding fault is judged to be an in-zone fault by the distribution line grounding fault identification algorithm based on phase current mutation detection, then the grounding fault is judged to be an in-zone fault; otherwise, it is an out-of-zone fault.
[0129] When the ground fault is judged as an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal, but the ground fault is judged as an external fault by the distribution line ground fault identification algorithm based on phase current mutation detection, the method of presetting more stringent ground characteristic parameters includes:
[0130] Lower the preset value u_val or lower the preset value i_val.
[0131] When the ground fault is judged as an out-of-zone fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal, but the ground fault is judged as an in-zone fault by the distribution line ground fault identification algorithm based on phase current mutation detection, the method of presetting more stringent ground characteristic parameters includes:
[0132] Increase the terminal sampling rate.
[0133] Figure 3 for Figure 1 In the present application, a ground fault identification algorithm based on feeder terminal is used to detect the fault in the area when the zero-sequence reactive power direction is detected, and the detection curve diagram of each parameter is shown. Figure 4 for Figure 1 A ground fault identification algorithm based on a feeder terminal in the present application is a curve diagram of various parameters when it is determined to be an out-of-zone fault during zero-sequence reactive power direction detection.
[0134] Figure 3 and Figure 4 The curves from top to bottom are:
[0135] Zero-sequence current curve, phase A current curve, phase B current curve, phase C current curve, phase A voltage curve, phase B voltage curve, phase C voltage curve, zero-sequence voltage curve, zero-sequence reactive power curve, phase A delta current curve, phase B delta current curve, phase C delta current curve.
[0136] The key point of this application is to design a ground fault identification algorithm that integrates zero-sequence reactive power analysis and phase current mutation detection. This algorithm combines two different fault identification methods and takes advantage of their respective advantages, such as the rapid positioning capability of zero-sequence reactive power analysis and the high sensitivity of phase current mutation detection, thereby improving the accuracy and reliability of ground fault identification.
[0137] This application involves key technologies such as signal acquisition, processing and feature extraction. By real-time processing of the collected zero-voltage zero-current and phase current signals, and extracting key transient mutation features, zero-sequence power analysis is performed, which not only considers the direction of zero-sequence power, but also the average value within the interval, and then combines the phase current mutation features for subsequent fault judgment and location.
[0138] This application also proposes a comprehensive judgment mechanism that combines the results of zero-sequence reactive power analysis and phase current mutation detection to improve the accuracy of fault identification. In addition, according to the grounding sensitivity parameter configured by the terminal, the sensitivity of fault judgment can be flexibly adjusted to meet the needs of different power grid environments.
[0139] To sum up, the key points of the present invention lie in the design and implementation of the fusion algorithm, signal processing and feature extraction, as well as comprehensive judgment and flexible configuration, which are the innovative points involved in the present invention and the core technologies to be protected.
[0140] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
[0141] Although the above describes the specific implementation methods of the present application in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present application. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present application, various modifications or deformations that can be made by technical personnel in this field without creative work are still within the scope of protection of the present application.
Claims
1. A ground fault identification algorithm based on feeder terminal, characterized in that: The following steps are involved: Step 1: Determine whether the ground fault is an internal fault or an external fault by using a fusion zero-sequence reactive power analysis algorithm based on the feeder terminal; Step 2: Determine whether the ground fault is an internal fault or an external fault through the distribution line ground fault identification algorithm based on phase current mutation detection; Step 3: Make a comprehensive judgment to determine whether the fault is within or outside the area.
2. The feeder terminal-based ground fault identification algorithm according to claim 1, characterized in that: The feeder terminal-based fused zero-sequence reactive power analysis algorithm comprises the following steps: Step 1: Set the terminal sampling rate to collect line signals; Step 2: Zero-sequence reactive power direction detection, including the following steps: Step 1: Continuously detect the collected zero-pressure and zero-current instantaneous values, and subtract the sampling value corresponding to the previous cycle from the current cycle sampling value; Step 2: When the zero-sequence voltage mutations at three consecutive points all exceed the preset value u_val, the mutation waveforms of the two cycles before and after the mutation are copied to the calculation buffer; Step 3: Determine whether the zero-sequence current effective value is greater than the preset value i_val. If it is less than the preset value i_val, the calculation buffer is cleared and the process returns to step 1; If it is greater than the preset value i_val, go to step 4; Step 4: Further determine the average mutation amount average between the effective value of a cycle 2 starting from the mutation point and the previous two cycles 1 cycle2-cycle1 Whether it exceeds the preset value u_val, when average cycle2-cycle1 When it exceeds the preset value u_val, it is judged as exceeded and goes to step 5, otherwise it returns to step 1; Step 5: Calculate the zero-sequence reactive average effective value Qu0i0_average within the time interval time_setting. If Qu0i0_average is a positive number and its absolute value is greater than the set value val_setting, it is judged as an internal fault; if it is a negative number and its absolute value is greater than the set value val_setting, it is judged as an external fault.
3. The feeder terminal-based ground fault identification algorithm according to claim 2, characterized in that: The step 4 also includes: further determining the average mutation amount average of a cycle cycle 2 starting from the mutation point and the effective value of the previous cycle cycle 0 cycle2-cyc1e0 Whether it exceeds the preset value u_val, when average cycle2-cycle0 When it exceeds the preset value u_val, it is judged as exceeded.
4. The feeder terminal-based ground fault identification algorithm according to claim 2, characterized in that: The terminal sampling rate is above 8 kHz.
5. The feeder terminal-based ground fault identification algorithm according to claim 1, characterized in that: The distribution line ground fault identification algorithm based on phase current mutation detection includes the following steps: Step 1: Continuously detect the collected zero-voltage and zero-current instantaneous values and the three-phase current recording data; Step 2: When the system detects an abnormal zero-current mutation signal, the three-phase current recording data is copied to the calculation buffer, and the difference between the previous cycle and the next cycle of the mutation point is calculated respectively, and the average value of the three-phase current mutation amount val_avg_before before the mutation and the average value of the three-phase current mutation amount val_avg_after after the mutation are obtained respectively; Step 3: Obtain the maximum mutation amount in the three phases before and after mutation: max_val_before=MAX(val_Ia_before, val_Ib_before, val_Ic_before) max_val_after=MAX(val_Ia_after, val_Ib_after, val_Ic_after) in: max_val_before is the maximum mutation amount in the three phases before the mutation; max_val_after is the maximum mutation amount in the three phases after the mutation; val_Ia_before is the current mutation amount of phase A before the mutation; val_Ib_before is the current mutation amount of phase B before the mutation; val_Ic_before is the current mutation amount of phase C before the mutation; val_Ia_after is the current mutation amount of phase A after the mutation; val_Ib_after is the current mutation amount of phase B after the mutation. val_Ic_after is the C phase current mutation amount after the mutation; Step 4: Calculate the three-phase current imbalance before and after the mutation: in: before_factor is the unbalance degree of the three-phase current before the mutation; after_factor is the unbalance degree of the three-phase current after the mutation; Step 5: Take the largest three-phase unbalance factor before and after the mutation = MAX (before_factor, after_factor). If it is greater than a preset value, it is determined that the ground fault is an internal fault. If it is less than the preset value, the buffer is cleared and the process returns to step 1.
6. The feeder terminal-based ground fault identification algorithm according to claim 5, characterized in that: In the step 2:
7. The feeder terminal-based ground fault identification algorithm according to claim 1, characterized in that: The internal fault refers to the fault occurring inside the power system protected by the relay protection. The out-of-zone fault refers to a fault that occurs outside the scope of the power system protected by the relay protection.
8. The feeder terminal-based ground fault identification algorithm according to claim 1, characterized in that: In the third step: Fusion judgment includes the following steps: Step 1: Set the ground sensitivity constant; Step 2: Determine the ground sensitivity value, where: When the grounding sensitivity value is 0 or 2, the grounding fault is judged to be an intra-zone fault; When the ground sensitivity value is 1, if: When the ground faults are judged to be internal faults by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal and the distribution line ground fault identification algorithm based on phase current mutation detection, the ground fault is judged to be an internal fault; otherwise, it is an external fault; When the ground fault is judged as an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal, but the ground fault is judged as an external fault by the distribution line ground fault identification algorithm based on phase current mutation detection, more stringent ground characteristic parameters are preset to further judge the various characteristic significances of the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal. If the ground fault is judged as an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal after more stringent ground characteristic parameters are preset, the ground fault is judged to be an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal; otherwise, it is an external fault. The grounding fault is judged to be an out-of-zone fault by the fused zero-sequence reactive power analysis algorithm based on the feeder terminal, but when the grounding fault is judged to be an in-zone fault by the distribution line grounding fault identification algorithm based on phase current mutation detection, more stringent grounding characteristic parameters are preset to further judge the various feature significances of the distribution line grounding fault identification algorithm based on phase current mutation detection. If the grounding fault is judged to be an in-zone fault by the distribution line grounding fault identification algorithm based on phase current mutation detection after more stringent grounding characteristic parameters are preset, the grounding fault is judged to be an in-zone fault by the distribution line grounding fault identification algorithm based on phase current mutation detection, then the grounding fault is judged to be an in-zone fault; otherwise, it is an out-of-zone fault.
9. The feeder terminal-based ground fault identification algorithm according to claim 8, characterized in that: When the ground fault is judged as an internal fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal, but the ground fault is judged as an external fault by the distribution line ground fault identification algorithm based on phase current mutation detection, the method of presetting more stringent ground characteristic parameters includes: Lower the preset value u_val or lower the preset value i_val.
10. The feeder terminal-based ground fault identification algorithm according to claim 8, characterized in that: When the ground fault is judged as an out-of-zone fault by the fusion zero-sequence reactive power analysis algorithm based on the feeder terminal, but the ground fault is judged as an in-zone fault by the distribution line ground fault identification algorithm based on phase current mutation detection, the method of presetting more stringent ground characteristic parameters includes: Increase the terminal sampling rate.