Fault section identification method and system for single-circuit zero-sequence current distribution characteristic relationship

Abstract

The application discloses a fault section identification method and system of single-loop zero sequence current distribution characteristics, comprising the following steps: for key feeder, arranging zero sequence current measuring points and edge nodes and numbering, monitoring bus zero sequence voltage on line and uploading to local edge node; each edge node extracts signal waveform after fault for 1s, and calculates amplitude of zero sequence current of each measuring point by using FFT to extract power frequency component; all edge nodes upload amplitude information to master station, and the master station judges fault section or sends early warning signal according to zero sequence current amplitude distribution characteristics. The application arranges zero sequence current measuring points for key feeder of ungrounded and arc suppression coil grounded power distribution network, when the fault position is located in the key feeder, only the measuring point information of the line itself is needed to identify the fault section, the method is simple and easy to implement, the required sampling frequency is lower, and the method has higher practicability.

Description

Technical Field

[0001] This invention belongs to the field of distribution network fault section identification, specifically a fault section identification method and system based on the distribution characteristics of zero-sequence current of a single circuit. Background Technology

[0002] In my country, the power distribution network largely operates under a neutral-point non-effectively grounded mode. The numerous branch lines, short line lengths, complex grid structure, and low voltage levels make fault location a persistent hot topic and challenge in smart grid research. Single-phase grounding faults account for approximately 80% of all grid faults. If not addressed promptly, these faults can easily escalate into two- or three-phase grounding faults, causing widespread power outages. Therefore, the rapid and accurate identification of the faulty feeder and faulty section after a single-phase grounding fault occurs is crucial for the safe operation of the power grid, improving power supply reliability, and reducing power outage losses.

[0003] Currently, the reliability of fault location and fault section localization in distribution networks with low-current grounding systems needs improvement. Existing methods for fault location and section localization include transient traveling wave method, instantaneous power method, zero-sequence admittance method, and injection method. However, in actual power grids, various factors affect the correct location of faults and sections, and the applicability of each method is limited. Therefore, fault location and section localization remains a hot topic and a challenge in research and engineering applications. Based on the importance level of users, distribution network feeders can be divided into critical feeders and non-critical feeders. Most existing methods for fault location and section localization rely heavily on information from all network measurement points, failing to achieve efficient utilization of this information. Therefore, the problem of how to rationally and efficiently utilize only the limited measurement point information of critical feeders in a distribution network for fault location and section localization needs to be solved. Summary of the Invention

[0004] To address the challenges mentioned in the background art, this invention proposes a method and system for identifying fault sections based on the distribution characteristics of zero-sequence current in a single-circuit line.

[0005] To achieve the aforementioned technical objectives and effects, this invention first proposes a fault section identification method based on the characteristic relationship of zero-sequence current distribution in a single-circuit line, comprising the following steps:

[0006] (1) For critical feeders, arrange and number zero-sequence current measurement points and edge nodes, monitor the zero-sequence voltage of the busbar online, and determine whether a grounding fault has occurred.

[0007] The principle for arranging zero-sequence current measurement points is as follows: For critical lines of the distribution network, zero-sequence current measurement points must be arranged at the beginning, end and branch points of the line, and the spacing between measurement points on the line shall not exceed 2km.

[0008] The principle for arranging edge nodes is as follows: the critical feeder is divided into different areas at the branch points of the line, and one edge node is arranged in each area.

[0009] Among them, the threshold value for online monitoring of whether the zero-sequence voltage of the distribution network bus exceeds the limit should be set to avoid the impact of the three-phase imbalance of the system reaching 10%. When the zero-sequence voltage exceeds the set threshold value, it is judged that a ground fault has occurred.

[0010] (2) The fault recording device acquires the original waveform of the zero-sequence current at each measurement point of the critical feeder and filters it, then uploads it to the local edge node;

[0011] When the system determines that a ground fault has occurred, the zero-sequence current waveforms of each measurement point obtained by the fault recording device in different areas are uploaded to the local edge node; otherwise, they are not uploaded.

[0012] (3) Extract the signal waveform 1 second after the fault at each edge node, and use FFT to extract the power frequency component to calculate the amplitude of the zero-sequence current at each measurement point.

[0013] Each edge node uses FFT to extract the power frequency component and calculates the zero-sequence current amplitude of all measurement points within its region. (i is the measurement point number, i = 1, 2, 3...).

[0014] (4) All edge nodes upload amplitude information to the master station, and the master station judges the fault section based on the distribution characteristics of zero-sequence current amplitude along the line.

[0015] The zero-sequence current amplitude distribution along the line is characterized as follows: regardless of whether the feeder is intact or faulty, the zero-sequence current is linearly distributed along the entire line, and its distribution pattern is as follows.

[0016] (a) Ensure the zero-sequence current amplitude at each point of the feeder:

[0017]

[0018] In the formula, x is the distance between the x-axis and the generatrix; I C To ensure the proper functioning of the feeder's own ground capacitance current; k is the value of the ground capacitance current per unit length of the line.

[0019] (b) Zero-sequence current amplitude at various points on the faulty feeder:

[0020]

[0021] In the formula, I ∑_C This is the sum of the ground capacitance currents of all healthy feeders in a neutral-point ungrounded system (when the neutral point is grounded with an arc suppression coil, this value is the sum of the ground capacitance currents of all healthy feeders and the neutral point current); I' CThis refers to the capacitance current to ground of the line downstream of the fault point.

[0022] The specific steps for determining the fault section based on the distribution characteristics of the zero-sequence current amplitude along the line are as follows:

[0023] (a) The main station calculates the Pearson linear correlation coefficient of the zero-sequence current amplitude uploaded by edge nodes in different regions:

[0024]

[0025] In the formula, j is the number of the edge node (j = 1, 2, 3...); x i Let i be the distance from the measurement point within the region where edge node j is located to the busbar (i is the measurement point number, i = 1, 2, 3...). This is the average distance from all measurement points within the region where edge node j is located to the busbar; This represents the average zero-sequence current amplitude of all measurement points within the region where edge node j is located.

[0026] (b) Determine the fault area based on the magnitude of the correlation coefficient:

[0027]

[0028] (c) If the measurement point i corresponding to the maximum value of the zero-sequence current amplitude in the fault area is found, the fault section is determined to be between measurement point i and measurement point i+1.

[0029] When no fault area is found based on the distribution characteristics of the zero-sequence current amplitude along the line, i.e., the critical feeder is determined to be a healthy feeder, a warning signal is issued to warn that the fault occurs on a non-critical feeder.

[0030] Then, this invention provides a fault section identification system based on the characteristic relationship of zero-sequence current distribution in a single-circuit line, comprising: a measurement unit, an edge computing unit, and a master station. Wherein:

[0031] The measurement unit is used to acquire the raw zero-sequence current signal at each measurement point of the key feeder and filter it.

[0032] The edge computing unit is used to extract the signal waveform 1 second after the fault and use FFT to extract the power frequency component to calculate the amplitude of the zero-sequence current at each measurement point.

[0033] The main station is used to determine the fault section based on the information uploaded by the edge computing unit and the distribution characteristics of the zero-sequence current amplitude along the line.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] The present invention discloses a fault section identification method and system based on the distribution characteristics of zero-sequence current in a single-circuit line. It sets up zero-sequence current measurement points on key feeders of distribution networks with ungrounded or arc-suppression coil grounding. When the fault location is located on the key feeder, the fault section can be identified only by the measurement point information of the line itself. The method is simple and easy to implement, requires a low sampling frequency, and has high practicality. Attached Figure Description

[0036] Figure 1 Flowchart of a fault section identification method based on the characteristic relationship of zero-sequence current distribution in a single-circuit line;

[0037] Figure 2 The topology diagram for the arrangement of measurement points and edge nodes in a 10kV neutral-point ungrounded distribution network. Detailed Implementation

[0038] The invention will now be further described with reference to the accompanying drawings.

[0039] This invention proposes a fault section identification method based on the characteristic relationship of zero-sequence current distribution in a single-circuit line. The overall process is as follows: Figure 1 As shown, it includes the following steps:

[0040] (1) As Figure 2 As shown, for critical feeders, zero-sequence current measurement points and edge nodes are arranged and numbered to monitor the zero-sequence voltage of the busbar online and determine whether a grounding fault has occurred.

[0041] (2) The fault recording device acquires the original waveform of the zero-sequence current at each measurement point of the key feeder and filters it. When the system determines that a ground fault has occurred, it uploads it to the local edge node; otherwise, it does not upload it.

[0042] (3) Extract the signal waveform 1 second after the fault at each edge node, and use FFT to extract the power frequency component to calculate the amplitude of the zero-sequence current at each measurement point.

[0043] (4) All edge nodes upload amplitude information to the main station. The main station calculates the Pearson linear correlation coefficient of the zero-sequence current amplitude uploaded by edge nodes in different regions, and determines the fault area based on the magnitude of the correlation coefficient. Within the fault area, the measurement point i corresponding to the maximum zero-sequence current amplitude is determined, and the fault section is identified as being between measurement point i and measurement point i+1. If no fault area is found, i.e., the critical feeder is determined to be a healthy feeder, a warning signal is issued to warn that the fault occurs on a non-critical feeder.

[0044] This invention provides a fault section identification system based on the distribution characteristics of zero-sequence current in a single-circuit line, comprising: a measurement unit, an edge computing unit, and a master station. Wherein:

[0045] The measurement unit is used to acquire the raw zero-sequence current signal at each measurement point of the key feeder and filter it.

[0046] The edge computing unit is used to extract the signal waveform 1 second after the fault and use FFT to extract the power frequency component to calculate the amplitude of the zero-sequence current at each measurement point.

[0047] The main station is used to determine the fault section based on the information uploaded by the edge computing unit and the distribution characteristics of the zero-sequence current amplitude along the line.

[0048] Example verification:

[0049] To verify the reliability and effectiveness of this invention, this invention is based on PSCAD / EMTDC and constructed as follows: Figure 2 The simulation model of a 10kV neutral-point ungrounded distribution network is shown. This simulation system includes 17 zero-sequence current measurement points, 16 overhead line sections, and 5 edge nodes on the critical feeder. Specific data are shown in Table 1. Phase A grounding faults were set in sections 02-03, 05-06, 08-09, 12-13, and 15-16, with a fault transition resistance of 100Ω. The simulation sampling frequency was set to 3.2kHz. The fault section identification results are shown in Table 2. The results show that this invention is applicable to critical feeders in distribution networks with multiple branches, and the fault section identification results are all correct. This method is simple and easy to implement, requires a low sampling frequency, and has high practicality.

[0050] Table 1 Distribution Network Line Data

[0051]

[0052] Table 2. Fault section identification results under different fault conditions.

[0053]

[0054] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for identifying fault sections based on the distribution characteristics of zero-sequence current in a single-circuit line, characterized in that, The method includes the following steps: Step 1: For critical feeders, set up and number zero-sequence current measurement points and edge nodes, monitor the zero-sequence voltage of the busbar online, and determine whether a grounding fault has occurred; Step 2: The fault recording device acquires and filters the original waveforms of the zero-sequence current at each measurement point of the critical feeder, and then uploads them to the local edge node; Step 3: Extract the signal waveform 1 second after the fault at each edge node, and use FFT to extract the power frequency component to calculate the amplitude of the zero-sequence current at each measurement point; Step 4: All edge nodes upload amplitude information to the master station, and the master station determines the fault section based on the distribution characteristics of the zero-sequence current amplitude along the line; In step four, the specific steps for determining the fault section based on the distribution characteristics of the zero-sequence current amplitude along the line are as follows: (a) The main station calculates the Pearson linear correlation coefficient of the zero-sequence current amplitude of the measurement points uploaded by edge nodes in different regions: In the formula, j is the number of the edge node, j=1, 2, 3, etc.; Let be the distance from the measurement point within the region where edge node j is located to the busbar, and i be the measurement point number, i=1, 2, 3, etc.; This is the average distance from all measurement points within the region where edge node j is located to the busbar; The average zero-sequence current amplitude of all measurement points within the region where edge node j is located; (b) Determine the fault area based on the magnitude of the correlation coefficient: (c) If the measurement point i corresponding to the maximum value of the zero-sequence current amplitude in the fault area is found, the fault section is determined to be between measurement point i and measurement point i+1; In step one, the principle for arranging edge nodes is as follows: the critical feeder is divided into different areas at the branch point of the line, and an edge node is arranged in each area. In step two, when the system determines that a ground fault has occurred, the zero-sequence current waveforms of each measurement point obtained by the fault recording device in different areas are uploaded to the local edge node; otherwise, they are not uploaded.

2. The fault section identification method based on the zero-sequence current distribution characteristics of a single-circuit line according to claim 1, characterized in that: In step one, the principle for arranging zero-sequence current measurement points is as follows: for critical lines of the distribution network, zero-sequence current measurement points must be arranged at the beginning, end and branch points of the line, and the spacing between measurement points on the line shall not exceed 2km.

3. The fault section identification method based on the zero-sequence current distribution characteristics of a single-circuit line according to claim 1, characterized in that: In step one, the zero-sequence voltage of the distribution network bus is monitored online to see if it exceeds the limit. The threshold value should be set to avoid the impact of the three-phase imbalance of the system reaching 10%. When the zero-sequence voltage exceeds the set threshold value, it is judged that a ground fault has occurred.

4. The fault section identification method based on the characteristic relationship of zero-sequence current distribution in a single-circuit line according to claim 1, characterized in that: In step three, each edge node uses FFT to extract the power frequency component and calculates the zero-sequence current amplitude of all measurement points within its region. , where i is the measurement point number, i=1, 2, 3, etc.

5. The fault section identification method based on the characteristic relationship of zero-sequence current distribution in a single-circuit line according to claim 1, characterized in that, In step four, the zero-sequence current amplitude distribution along the line is as follows: regardless of whether it is a healthy feeder or a faulty feeder, the zero-sequence current is linearly distributed along the entire line, and its distribution pattern is as follows: (a) Ensure the zero-sequence current amplitude at each point of the feeder is adequate: In the formula, x is the distance between the source and the generatrix; To ensure the proper functioning of the feeder's own ground capacitance current; k is the value of the ground capacitance current per unit length of the line; (b) Zero-sequence current amplitude at various points on the faulty feeder: In the formula, This is the sum of the ground capacitance currents of all healthy feeders in a neutral-point ungrounded system. When the neutral point is grounded by an arc suppression coil, this value is the sum of the ground capacitance currents of all healthy feeders and the neutral point current. This refers to the capacitance current to ground of the line downstream of the fault point.

6. The method for determining fault sections based on the distribution characteristics of zero-sequence current amplitude along a line, as described in claim 1, is characterized in that... If the fault area cannot be found using this method, i.e., the critical feeder is determined to be a healthy feeder, a warning signal is issued to warn that the fault occurs on a non-critical feeder.

7. A fault section identification system based on the characteristic relationship of zero-sequence current distribution in a single-circuit line is used to implement the fault section identification method based on the characteristic relationship of zero-sequence current distribution in a single-circuit line as described in any one of claims 1-6, the system comprising: Measurement unit, edge computing unit, and main station, among which: The measurement unit is used to acquire the raw zero-sequence current signal at each measurement point of the key feeder and filter it. The edge computing unit is used to extract the signal waveform 1 second after the fault and use FFT to extract the power frequency component to calculate the amplitude of the zero-sequence current at each measurement point. The main station is used to determine the fault section based on the information uploaded by the edge computing unit and the distribution characteristics of the zero-sequence current amplitude along the line.

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