Distribution line fault discrimination method and system

Abstract

The invention provides a distribution line fault judgment method and system. The distribution line fault judgment method comprises the steps that S1, a plurality of detection points are arranged on a distribution line to be detected, and three-phase current is collected; s2, converting the three-phase current of the plurality of detection points into a plurality of zero-sequence currents through an intelligent fusion terminal; s3, collecting a plurality of zero-sequence currents, and analyzing the plurality of zero-sequence currents respectively; and S4, when the distribution line to be detected has a fault, calculating the occurrence duration of the corresponding zero-sequence current. According to the method, maintenance processing in different modes can be performed in a targeted manner when a fault occurs, tedious troubleshooting and maintenance processes under an instantaneous fault are avoided, the operation efficiency and reliability of the power distribution network are improved, the maintenance cost is greatly reduced, and in addition, compared with a conventional detection mode at the present stage, the maintenance cost is greatly reduced. The method has the remarkable advantages of being convenient to operate, wide in application range, high in detection precision, high in response speed and the like, and a new thought is provided for power distribution maintenance engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution lines, and in particular to a distribution line fault determination method and system. Background Art

[0002] In today's power system, the safe and stable operation of distribution lines is crucial to ensuring the reliability of the power grid and the quality of power supply to users. Short-circuit faults are one of the most common problems in distribution lines and occur frequently, and most of them are transient. Transient faults are usually caused by external short-term factors, such as trees touching wires, bird activity, or instantaneous lightning strikes. Once these faults are triggered, normal power supply can be quickly restored through reclosing operations, thereby avoiding long-term power outages and ensuring the continuous power supply capacity of the power grid.

[0003] Despite this, existing distribution line protection and monitoring technologies, such as fault indicators, feeder terminal units (FTUs) and other distribution terminal devices, often have difficulty accurately distinguishing between transient faults and permanent faults in actual applications. When these devices detect a fault, they often adopt a unified response strategy, that is, they operate according to the processing procedures for permanent faults. This means that even those transient faults that can be restored by reclosing require cumbersome troubleshooting and maintenance procedures, which not only leads to a waste of maintenance resources, but may also cause unnecessary power outages, seriously affecting the operating efficiency of the distribution system and the user's power experience.

[0004] In addition, due to the frequent occurrence of transient faults, the use of permanent fault maintenance methods will greatly increase the workload of maintenance personnel, while increasing maintenance costs and difficulty. This inefficient fault handling method is not only not conducive to the optimized operation of the distribution system, but also does not meet the requirements of modern power grids for efficient, reliable, and intelligent operation and maintenance. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problem in the prior art that it is difficult to identify the type of distribution line faults, and to provide a distribution line fault identification method and system.

[0006] In order to solve the above technical problems, the present invention provides a distribution line fault identification method, which includes: step S1, setting multiple detection points on the distribution line to be detected, and collecting three-phase currents at multiple detection points; step S2, converting the three-phase currents of multiple detection points into multiple zero-sequence currents through an intelligent fusion terminal; step S3, collecting multiple zero-sequence currents, and analyzing the multiple zero-sequence currents respectively to determine whether there is a fault on the distribution line to be detected: when the zero-sequence current is greater than 1A, the distribution line to be detected has a fault; when the zero-sequence currents are all ≤1A, the distribution line to be detected does not have a fault; step S4, when the distribution line to be detected has a fault When a fault occurs, the corresponding zero-sequence current occurrence duration and the corresponding proportion are calculated to determine the type of fault: when the zero-sequence current occurrence duration is greater than 1s, and the proportion of the number of intelligent fusion terminals on the distribution line to be detected with the zero-sequence current occurrence duration greater than 1s in all the intelligent fusion terminals on the distribution line to be detected is less than 0.5, it is determined that a permanent fault exists in the distribution line to be detected; when the zero-sequence current occurrence duration is ≤1s, and the proportion of the number of intelligent fusion terminals on the distribution line to be detected with the zero-sequence current occurrence duration greater than 1s in all the intelligent fusion terminals on the distribution line to be detected is greater than or equal to 0.5, it is determined that a transient fault exists in the distribution line to be detected.

[0007] In one embodiment of the present invention, in step S1, multiple distribution transformers are set at multiple detection points of the distribution line to be detected, and current transformers are set on the high-voltage side of the multiple distribution transformers to collect three-phase currents at the multiple detection points.

[0008] In one embodiment of the present invention, in step S2, a plurality of the intelligent fusion terminals are respectively set corresponding to the plurality of the detection points, and the intelligent fusion terminals are respectively connected to the corresponding current transformers to receive the three-phase current information of the current transformers and integrate them into zero-sequence current.

[0009] In one embodiment of the present invention, the process of integrating the three-phase current information and integrating the output zero-sequence current of the intelligent fusion terminal includes: step S21, the intelligent fusion terminal receives the A-phase current value I output by the current transformer A , B phase current value I B and C phase current value I C Step S22: Obtain the zero-sequence current I by taking the average current of phase A, phase B and phase C. 0 =(I A +I B +I C ) / 3; Step S23, the zero-sequence current is filtered in sequence and the fault is detected before conversion.

[0010] In one embodiment of the present invention, in step S3, the zero-sequence current not greater than 1A is directly sent to the central station, and the zero-sequence current less than 1A is collected by the feeder terminal unit and then transmitted to the central station through the fault indicator.

[0011] In one embodiment of the present invention, in step S3, the fault indicator sends out an alarm message after receiving the feeder terminal unit signal, and the central station analyzes and fuses all the zero-sequence currents it receives to determine the specific fault location.

[0012] In one embodiment of the present invention, in step S3, after determining whether there is a fault on the distribution line to be detected, misjudgment detection is performed, and the misjudgment detection is: calculating the proportion P of the number of the intelligent fusion terminals with zero-sequence current>1A in the distribution line to be detected among all the intelligent fusion terminals in the distribution line to be detected. 0 , when P 0 When P is less than 0.5, there is a fault misjudgment; 0 When ≥0.5, there is no false fault diagnosis and the next step can be performed.

[0013] In one embodiment of the present invention, in step S4, when there is a fault in the distribution line to be detected, the corresponding zero-sequence current occurrence duration and the corresponding proportion are calculated by collecting the corresponding zero-sequence current waveform.

[0014] In one embodiment of the present invention, a plurality of the distribution lines to be inspected are respectively connected to a central station for synchronous inspection.

[0015] The present invention also provides a distribution line fault identification system, which uses the above distribution line fault identification method to perform distribution line fault detection.

[0016] The above technical solution of the present invention has the following advantages compared with the prior art: The distribution line fault identification method and system described in the present invention realize accurate monitoring of whether a distribution line fault occurs and the type of fault through the change of zero-sequence current in the distribution line to be detected, thereby being able to carry out targeted maintenance processing in different ways when a fault occurs, avoiding the cumbersome fault investigation and maintenance process under instantaneous faults, which not only improves the operating efficiency and reliability of the distribution network, but also greatly reduces the maintenance cost. In addition, compared with the conventional detection methods at this stage, the present application also has significant advantages such as easy operation, wide application range, high detection accuracy, and fast response speed, providing new ideas for distribution maintenance projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0018] Figure 1 It is a flow chart of a method for distinguishing distribution line faults in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Embodiment 1

[0020] This embodiment provides a distribution line fault determination method, which is used to detect and determine whether a distribution line fault occurs and what kind of fault occurs, and includes the following steps: Step S1, set multiple detection points on the distribution line to be detected, and collect three-phase current at multiple detection points; further, in step S1 described in this embodiment, multiple distribution transformers are set at multiple detection points of the distribution line to be detected, and current transformers are set on the high-voltage side of multiple distribution transformers to collect three-phase current at multiple detection points. Specifically, in the process of implementing the above steps, it is first necessary to determine the appropriate detection point location based on factors such as the length of the distribution line, load distribution and geographical environment, and then install a distribution transformer at each detection point. The function of the transformer is to convert high-voltage electricity into low-voltage electricity, which is convenient for subsequent power monitoring and control. When installing the current transformer, it is necessary to set it on the high-voltage side of the distribution transformer to ensure that the transformation ratio and accuracy level of the current transformer meet the monitoring requirements. At the same time, the secondary side of the current transformer needs to be connected to a measuring instrument or protection device. After the installation is completed, the current transformer and related equipment are debugged and calibrated to ensure their normal operation.

[0021] Step S2, converting the three-phase currents of the plurality of detection points into a plurality of zero-sequence currents through an intelligent fusion terminal; further, in this embodiment, a plurality of the intelligent fusion terminals are respectively provided corresponding to the plurality of detection points, and the intelligent fusion terminals are respectively connected to the corresponding current transformers to receive the three-phase current information of the current transformers and integrate them into zero-sequence current. Specifically, the process of the intelligent fusion terminal integrating the three-phase current information and integrating the output zero-sequence current includes: Step S21: The intelligent fusion terminal receives the A-phase current value I output by the current transformer. A , B phase current value I B and C phase current value I C ; Step S22: Obtain the zero-sequence current I by taking the average current value of phase A, phase B and phase C. 0 =(I A +I B +I C ) / 3; Step S23, the zero-sequence current is filtered and fault detected in sequence, and then the conversion is completed.

[0022] Step S3, collecting a plurality of the zero-sequence currents, and analyzing the plurality of the zero-sequence currents respectively to determine whether there is a fault on the distribution line to be detected: When the zero-sequence current is greater than 1A, the distribution line to be detected has a fault; When the zero-sequence current is ≤1A, there is no fault in the distribution line to be detected; Specifically, in this embodiment, the zero-sequence current not greater than 1A is directly sent to the central station, and the zero-sequence current less than 1A is collected by the feeder terminal unit and transmitted to the central station through the fault indicator. Furthermore, the fault indicator issues an alarm message after receiving the feeder terminal unit signal, and the central station analyzes and fuses all the zero-sequence currents it receives to determine the specific fault location.

[0023] In this embodiment, in order to avoid waste of resources due to misjudgment of detection, in this embodiment, misjudgment detection is performed after determining whether there is a fault on the distribution line to be detected. The misjudgment detection is: calculating the proportion P of the number of the intelligent fusion terminals with zero-sequence current>1A in the distribution line to be detected among all the intelligent fusion terminals in the distribution line to be detected 0 , When P 0 When <0.5, there is a fault misjudgment; When P 0 When ≥0.5, there is no false fault diagnosis and the next step can be performed.

[0024] Step S4: When there is a fault in the distribution line to be detected, the corresponding zero-sequence current occurrence duration and the corresponding proportion are calculated to determine the fault type: When the duration of the zero-sequence current appearance is greater than 1s, and the proportion of the number of the intelligent fusion terminals on the distribution line to be detected where the zero-sequence current appearance duration is greater than 1s in all the intelligent fusion terminals on the distribution line to be detected is less than 0.5, it is determined that a permanent fault exists on the distribution line to be detected; When the duration of the zero-sequence current is ≤1s, and the number of intelligent fusion terminals on the distribution line to be detected whose zero-sequence current duration is >1s accounts for P≥0.5 of all the intelligent fusion terminals on the distribution line to be detected, it is determined that there is an instantaneous fault on the distribution line to be detected.

[0025] Specifically, in this embodiment, when there is a fault in the distribution line to be detected, the corresponding zero-sequence current waveform is collected to calculate the corresponding zero-sequence current occurrence duration and the corresponding proportion. Embodiment 2

[0026] The present embodiment provides another distribution line fault identification method, which is used to perform fault detection and identification on multiple distribution lines to be detected at the same time. The detection process and principle are the same as those in the first embodiment and will not be elaborated here. In the present embodiment, the multiple distribution lines to be detected are respectively connected to the central station for synchronous detection. The specific number is determined according to the corresponding equipment according to the actual scene requirements, and the present invention does not make any specific restrictions on this. Embodiment 3

[0027] This embodiment provides a distribution line fault identification system, which uses the above-mentioned distribution line fault identification method to perform distribution line fault detection.

[0028] In summary, the distribution line fault identification method and system described in the present invention realize accurate monitoring of whether a distribution line fault occurs and the type of fault through the change of zero-sequence current in the distribution line to be detected, thereby being able to carry out targeted maintenance processing in different ways when a fault occurs, avoiding the cumbersome fault troubleshooting and maintenance process under instantaneous faults, which not only improves the operating efficiency and reliability of the distribution network, but also greatly reduces the maintenance cost. In addition, compared with the conventional detection methods at this stage, the present application also has significant advantages such as easy operation, wide application range, high detection accuracy, and fast response speed, providing new ideas for distribution maintenance projects.

[0029] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for determining a distribution line fault, characterized in that: include: Step S1, setting a plurality of detection points on the power distribution line to be detected, and collecting three-phase currents at the plurality of detection points; Step S2, converting the three-phase currents of the plurality of detection points into a plurality of zero-sequence currents through an intelligent fusion terminal; Step S3, collecting a plurality of the zero-sequence currents, and analyzing the plurality of the zero-sequence currents respectively to determine whether there is a fault on the distribution line to be detected: When the zero-sequence current is greater than 1A, the distribution line to be detected has a fault; When the zero-sequence current is ≤1A, there is no fault in the distribution line to be detected; Step S4: When there is a fault in the distribution line to be detected, the corresponding zero-sequence current occurrence duration and the corresponding proportion are calculated to determine the fault type: When the duration of the zero-sequence current appearance is greater than 1s, and the proportion of the number of the intelligent fusion terminals on the distribution line to be detected where the zero-sequence current appearance duration is greater than 1s in all the intelligent fusion terminals on the distribution line to be detected is less than 0.5, it is determined that a permanent fault exists on the distribution line to be detected; When the duration of the zero-sequence current is ≤1s, and the number of intelligent fusion terminals on the distribution line to be detected whose zero-sequence current duration is >1s accounts for P≥0.5 of all the intelligent fusion terminals on the distribution line to be detected, it is determined that there is an instantaneous fault on the distribution line to be detected.

2. The method for determining a distribution line fault according to claim 1, wherein: In step S1, multiple distribution transformers are arranged at multiple detection points of the distribution line to be detected, and current transformers are arranged on the high-voltage sides of the multiple distribution transformers to collect three-phase currents at the multiple detection points.

3. The method for determining a distribution line fault according to claim 2, wherein: In step S2, a plurality of the intelligent fusion terminals are respectively provided corresponding to the plurality of the detection points, and the intelligent fusion terminals are respectively connected to the corresponding current transformers to receive the three-phase current information of the current transformers and integrate the three-phase current information into a zero-sequence current.

4. The method for determining a distribution line fault according to claim 1, wherein: The process of integrating three-phase current information and integrating output zero-sequence current by the intelligent fusion terminal includes: Step S21: The intelligent fusion terminal receives the A-phase current value I output by the current transformer. A , B phase current value I B and C phase current value I C ; Step S22: Obtain the zero-sequence current I0=(I A +I B +I C ) / 3; Step S23, the zero-sequence current is filtered and fault detected in sequence, and then the conversion is completed.

5. The method for determining a distribution line fault according to claim 1, wherein: In step S3, the zero-sequence current not greater than 1A is directly sent to the central station, and the zero-sequence current less than 1A is collected by the feeder terminal unit and then transmitted to the central station through the fault indicator.

6. The method for determining a distribution line fault according to claim 5, characterized in that: In step S3, the fault indicator sends out an alarm message after receiving the feeder terminal unit signal, and the central station analyzes and merges all the zero-sequence currents it receives to determine the specific fault location.

7. The method for determining a distribution line fault according to claim 1, characterized in that: In step S3, after determining whether there is a fault on the distribution line to be detected, misjudgment detection is performed, and the misjudgment detection is: calculating the proportion P0 of the number of the intelligent fusion terminals with zero-sequence current>1A in the distribution line to be detected among all the intelligent fusion terminals in the distribution line to be detected, When P0<0.5, there is a fault misjudgment; When P0≥0.5, there is no misjudgment of fault and the next step can be performed.

8. The method for determining a distribution line fault according to claim 1, wherein: In step S4, when there is a fault in the distribution line to be detected, the corresponding zero-sequence current waveform is collected to calculate the corresponding zero-sequence current occurrence duration and the corresponding proportion.

9. The method for determining a distribution line fault according to claim 1, characterized in that: The plurality of distribution lines to be inspected are respectively connected to a central station for synchronous inspection.

10. A distribution line fault identification system, characterized in that: A distribution line fault detection method according to any one of claims 1 to 9 is used to detect distribution line faults.

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