Distribution line state on-line monitoring system and grounding fault diagnosis method

Abstract

The invention relates to a distribution line state on-line monitoring system and a grounding fault diagnosis method, the system comprises a signal acquisition module, a collection preprocessing module and an analysis master station, the signal acquisition module is used for acquiring distribution line state and environmental data and sending the acquired data to the collection preprocessing module; the collection preprocessing module is used for receiving, storing and processing the data sent by the signal acquisition module, and actively or passively uploading the data to an analysis master station according to a data processing result; and the analysis master station is used for receiving or measuring the data stored by each collection preprocessing module, and carrying out line state evaluation and fault positioning diagnosis. According to the invention, the operation state of the distribution network feeder can be monitored in real time and potential hidden dangers can be identified by using the existing monitoring equipment, the fault position can be rapidly positioned after the fault occurs, and rapid troubleshooting and power transmission recovery are facilitated.

Description

Technical Field

[0001] The present application relates to the field of detection, and particularly to an online state monitoring system and a fault diagnosis method for a distribution line under a new power system. Background Art

[0002] The distribution network receives electric energy from the transmission network or a regional power plant and distributes it to users locally or step by step through distribution facilities, playing an important role in distributing electric energy in the power grid.

[0003] On the one hand, improving the power supply reliability of the distribution network has been the core work for a long time, and the key measures lie in quickly and accurately diagnosing faults and further identifying line defects. Among various faults occurring in the distribution network, single-phase grounding faults account for more than 80%, which are likely to cause user power outages, personal electric shock, and electrical fires. At present, there is still a lack of economical and effective technical means for detecting and diagnosing single-phase grounding faults, which is the key concern area of power companies in various provinces. Due to the large proportion of cable lines in the current distribution network, the neutral point operation mode mostly adopts the neutral point grounded through an arc suppression coil (resonant grounding system) to offset the capacitive current of the cable and suppress the arc during the grounding fault, thereby reducing the overvoltage risk and fault duration of the system. Although adopting this neutral point operation mode allows the small-current grounding distribution network to operate with faults for 1 - 2 hours, due to the influence of the arc suppression coil, it is impossible to use steady-state electrical quantities to judge the grounding fault.

[0004] In contrast, transient electrical quantities contain rich information and can break through the interference of the arc suppression coil on fault detection. For example, the changes in transient voltage and transient current at the moment of the fault are more intense, and their amplitudes are several times to more than a dozen times that of the steady-state value, and the frequency characteristics are less affected by the arc suppression coil. Therefore, analyzing transient electrical quantities can accurately reflect the electrical state at the time of the fault and help quickly and accurately select the fault line and locate the fault. However, the existing methods for judging grounding faults based on transient electrical quantities have the following difficulties:

[0005] 1. The fault determination basis is complex. The determination of a grounding fault involves multiple transient electrical quantities, especially for small-current single-phase grounding faults, such as faults. How to select effective transient electrical quantities and reasonably combine them directly determines the accuracy of fault judgment. However, in the face of diverse characteristic quantities, it is highly complex to select and combine the optimal determination basis, increasing the difficulty of fault determination.

[0006] 2. Difficult data acquisition and lack of unified standards. The number of monitoring devices is huge, and the amount of data collected is enormous. However, since the oscillographic monitoring devices deployed in the distribution network come from different manufacturers, the oscillogram trigger standards are not unified. There is no unified regulation for the fault oscillogram trigger amplitude and duration of different devices, which easily leads to increased difficulty in data utilization and integration. This inconsistency in standards affects the accuracy of data analysis and the reliability of fault judgment.

[0007] 3. Insufficient sensitivity to weak fault signals. Current fault indicators and line selection technologies mainly rely on obvious current and voltage change signals, and it is difficult to capture and identify weak-changing fault signals in a timely manner, such as high-resistance single-phase grounding faults. At the same time, under abnormal operating conditions (such as differences in system operating mode, fault location, transition impedance, fault time, etc.), the characteristic quantities are easily interfered with greatly, increasing the difficulty of characteristic identification.

[0008] 4. High requirements for real-time performance and computing resources. With the expansion of the scale of the power system, the number of monitoring points and the amount of data have increased sharply. There are delays and missed transmissions in data upload, and processing a large amount of high-frequency sampled data requires powerful computing resources, which may cause the fault judgment algorithm to not run in real time and effectively. In this case, the timeliness of fault detection and location is affected, and it cannot meet the rapid response requirements of the power system.

[0009] Currently, most fault judgment methods and models based on transient electrical quantities have theoretically solved the theoretical basis problem of grounding fault judgment in Difficulty 1, such as the first half-wave method, transient zero-sequence current amplitude ratio and phase comparison method, and transient energy method, as well as the time-frequency analysis method, waveform similarity method, and traveling wave method that have been studied more currently. However, there is still much room for improvement in Difficulties 2, 3, and 4: In terms of Difficulties 2 and 4, existing patents such as CN109683062B, CN205787050U, CN219552575U, etc. all use the development and large-scale installation of more accurate fault indicators as the only data acquisition device, without integrating and utilizing the already installed distribution automation terminals in the distribution network. Therefore, only the fault section location of pure overhead lines can be realized, and the situations of pure cable lines and overhead-cable hybrid lines in the distribution network are not considered; there is still no effective implementation approach for high-resistance grounding faults in Difficulty 3 in actual judgment.

[0010] On the other hand, enhancing the carrying capacity of the distribution network for new energy elements is an important task in the current transformation and upgrading of the power system, and it is also necessary to monitor the volatility and uncertainty of new energy. With the continuous emergence and large-scale access of diversified loads such as distributed power sources, electric vehicles, energy storage, and intelligent microgrids, the functions and forms of the distribution network are undergoing significant changes, gradually developing from unidirectional power flow to bidirectional power flow, presenting an increasingly complex "multi-source" characteristic. Relying solely on the monitoring of electrical quantities is difficult to provide sufficient monitoring data support for the reliability and security of the distribution network after the integration of new energy. It is necessary to consider more the collection of non-electrical quantity data such as environmental parameters and meteorological information while monitoring electrical quantity data. Through the active monitoring of these multi-source data, a data foundation for the optimal regulation and control of the new distribution network is laid. Summary of the Invention

[0011] The purpose of the embodiments of the present application is to provide an on-line monitoring system for the state of distribution lines and a grounding fault diagnosis method, which can use existing monitoring equipment to monitor the operating state of distribution network feeders in real time and identify potential hidden dangers, can quickly locate the fault location after a fault occurs, and helps to quickly troubleshoot the fault and restore power supply.

[0012] To achieve the above purpose, the present application provides the following technical solutions:

[0013] In the first aspect, the embodiments of the present application provide a distribution line state monitoring system, including a signal acquisition module, an aggregation preprocessing module, and an analysis master station.

[0014] The signal acquisition module is used to obtain the state and environmental data of the distribution line and send the collected data to the aggregation preprocessing module.

[0015] The aggregation preprocessing module is used to receive, store, and process the data sent by the signal acquisition module, and actively or passively upload the data to the analysis master station according to the data processing results.

[0016] The analysis master station is used to receive or call the data stored in each aggregation preprocessing module, and perform line state evaluation and fault location diagnosis.

[0017] The signal acquisition module uses on-line terminal monitoring equipment installed in the distribution network to collect the voltage waveform, current waveform, temperature, image, and environmental temperature and humidity data of line equipment in real time, and transmits the data to the aggregation preprocessing module. Each signal acquisition module is only responsible for the signal acquisition of one monitoring point. The on-line terminal monitoring equipment includes a fault indicator, an infrared camera, and a temperature and humidity sensor.

[0018] The aggregation and preprocessing module includes a data aggregation unit, a data preprocessing unit and a communication unit. The data aggregation unit aggregates the data collected by a signal acquisition module and stores it locally. The data preprocessing unit calculates the zero-sequence voltage and zero-sequence current based on the stored three-phase voltage and three-phase current data. When the amplitude of the zero-sequence voltage or zero-sequence current exceeds the safety threshold and the duration exceeds the fixed value T, all data are actively uploaded to the analysis main station through the communication unit. Each aggregation and preprocessing module receives, stores, preprocesses and uploads the data to the analysis main station for a collection module.

[0019] The aggregation preprocessing module forms a wireless communication network with the signal acquisition module and the analysis main station through a communication unit using a time-division multiplexing wireless communication method. The communication unit of the aggregation preprocessing module uses GPS or Beidou timing to achieve accurate time synchronization with the signal acquisition module and the analysis main station.

[0020] The analysis master station receives and calls for data uploaded from the aggregation preprocessing module. The analysis master station also reserves an interface to receive distribution automation terminal recording data such as station terminal DTU, feeder terminal FTU, and primary and secondary fusion switches transmitted from an external system.

[0021] The analysis master station first synchronizes the data collection time of each monitoring point according to the timestamp of the global positioning system or the Beidou satellite navigation system. Subsequently, the master station performs time alignment and truncation processing on the three-phase voltage and three-phase current waveform data received from each monitoring point of the self-distribution network, and removes redundant data of unaligned time points to ensure that the length and time points of all waveform data are consistent. On this basis, the master station superimposes the pre-processed data through the vector sum method, calculates the zero-sequence voltage and zero-sequence current of each monitoring point, and extracts steady-state and transient signals therefrom respectively. The analysis master station further calculates the characteristic values ​​of these signals, and calculates the zero-sequence active power and zero-sequence reactive power of each monitoring point accordingly. By comparing the waveform similarity and polarity of the current signal and reactive power of each monitoring point, the faulty and non-faulty lines and further fault location are confirmed.

[0022] In a second aspect, an embodiment of the present application provides a method for diagnosing a ground fault of a distribution network line, comprising the following specific steps:

[0023] S1, real-time capture of electric field and current data, generating accurate transient waveforms;

[0024] S2, the fault triggers the judgment criteria at the moment, and all the terminal data of the bus are sent synchronously;

[0025] S3, the algorithm combines topological data to achieve fault line selection and location;

[0026] S4, rapid notification and guidance of emergency repairs;

[0027] S5. Optimize and adjust the monitoring point positions according to the fault statistics results.

[0028] In step S1, the on-site fault indicator, substation terminal DTU, feeder terminal FTU, and primary-secondary integrated switch distribution automation terminal collect and record the voltage and current of the distribution network line in real time to generate a transient recording file.

[0029] In step S2, when a fault occurs, based on the preset thresholds: the zero-sequence current I0 exceeds 200 A or the zero-sequence voltage U0 exceeds 28 V, and the duration T exceeds 0.02 s, the criterion trigger is successful. The aggregation preprocessing module and the distribution automation terminal at this location upload the recording wave to the analysis master station. At the same time, the analysis master station calls and measures the voltage and current recording wave data of all the remaining substation terminals DTU, feeder terminals FTU, and primary-secondary integrated switches, these distribution automation terminals under the same bus according to the line topology.

[0030] In step S3, the analysis master station performs time alignment and truncation processing on the received and called recording files, removes the redundant data at the unaligned time points, calculates the zero-sequence voltage and zero-sequence current of each monitoring point, extracts the steady-state and transient signals respectively from them, calculates the characteristic values of these signals, and realizes fault line selection and location positioning according to the grounding fault location determination principle.

[0031] In step S4, the grounding fault location conclusion given by the analysis master station is used to guide the repair personnel to quickly rush to the scene to implement repair and power transmission.

[0032] In step S5, based on the on-site verification of the accuracy of the grounding fault judgment, according to the formula , where k is the transformation ratio of the 10 kV voltage transformer, v is the arc suppression coil transition compensation coefficient, U N is the rated phase voltage, and R g is the transition resistance. When the safety threshold of the zero-sequence current I0 is 200 A, if there are many missed grounding fault cases statistically on-site, then reduce the safety threshold of the zero-sequence voltage U0 and the duration T, and the corresponding withstand transition resistance value increases, so as to reduce the missed grounding fault cases.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: This application conducts multi-dimensional active monitoring on the distribution network line and its diversified loads, providing decision support for the new distribution network to cope with the large-scale access of distributed power sources. By formulating a unified grounding fault criterion, it solves the problem that the traditional monitoring system cannot comprehensively process multi-source heterogeneous data, realizes the accurate diagnosis and rapid location of grounding faults, and enhances the reliability and safety of the distribution network. Description of the Drawings

[0034] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings required for use in the embodiments of the present application. It should be understood that the following drawings only show certain embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0035] Figure 1 It is a block diagram of a distribution line status monitoring system;

[0036] Figure 2 It is a schematic diagram of a distribution line status monitoring system;

[0037] Figure 3 It is a flowchart of the working mode of the aggregation and preprocessing module;

[0038] Figure 4 It is a flowchart of a grounding fault diagnosis method;

[0039] Figure 5 It shows the principle of grounding fault line selection and location. Specific embodiments

[0040] The following will describe the technical solutions in the embodiments of the present application in combination with the accompanying drawings in the embodiments of the present application. It should be noted that: similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0041] The term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the presence of another identical element in the process, method, article or device including the said element.

[0042] Terms such as "first", "second", etc. are only used to distinguish one entity or operation from another entity or operation, and cannot be understood as indicating or implying relative importance, nor can it be understood as requiring or implying any actual relationship or order between these entities or operations.

[0043] Such as Figure 1 、 Figure 2 And Figure 5As shown in the figure, the system consists of a signal acquisition module, an aggregation and preprocessing module, and an analysis master station. Among them, the signal acquisition module is used to obtain the distribution line status and environmental data, and send the collected data to the aggregation and preprocessing module; the aggregation and preprocessing module is used to receive, store, and process the data sent by the signal acquisition module, and actively or passively upload the data to the analysis master station according to the data processing results; the analysis master station is used to receive or call the data stored in each aggregation and preprocessing module, and perform line status evaluation and fault location diagnosis.

[0044] The signal acquisition module at each monitoring point includes the following devices:

[0045] 1) Fault indicator: Real-time monitor the current and voltage waveforms to detect abnormal signals on the line;

[0046] 2) Infrared camera: Provide real-time images of line equipment to identify the equipment status;

[0047] 3) Temperature and humidity sensor: Monitor the environmental conditions of the distribution line to assist in fault diagnosis.

[0048] The aggregation and preprocessing module is responsible for receiving the data transmitted by the signal acquisition module and storing and processing it.

[0049] As Figure 3 shown, the working mode of the aggregation and preprocessing module is as follows: When there is no fault in the distribution network line, that is, when the zero-sequence voltage and current amplitudes are within the normal range, the aggregation and preprocessing module only locally stores the data of all monitoring points but does not automatically upload it to the analysis master station through the communication module. It only uploads the specified time period and collected data as required when the analysis master station calls; when there is an abnormality in the distribution network line, that is, when the zero-sequence voltage and current amplitudes of the line exceed the normal range, causing any on-line terminal monitoring device to upload abnormal or fault data, the aggregation and preprocessing module uploads the data collected by all monitoring devices during the abnormal or fault period to the analysis master station through the communication unit.

[0050] The aggregation and preprocessing module includes the following units:

[0051] 1) Data aggregation unit: Receive the data from the signal acquisition module and perform local storage.

[0052] 2) Data preprocessing unit: Calculate the zero-sequence voltage (U0) and zero-sequence current (I0) based on the stored voltage and current data, and determine whether they exceed the set safety threshold, such as when the zero-sequence current exceeds 200A and the duration exceeds 0.02s, or the zero-sequence voltage (secondary) exceeds 28V and the duration exceeds 0.02s.

[0053] 3) Communication unit: Transmit the processed data to the analysis master station through time-division multiplexing wireless communication, and achieve accurate time synchronization between modules through GPS or Beidou time service.

[0054] As Figure 3 shown, corresponding to the working mode of the aggregation preprocessing module, the working mode of the analysis master station is as follows: when there is no fault in the distribution network line, the analysis master station does not receive the information transmitted by the aggregation preprocessing module, but can manually select the voltage waveform, current waveform, temperature, image, ambient temperature and humidity and other data within a certain time period to be viewed, and call the data stored in the aggregation preprocessing module through wireless communication to provide data for identifying potential hazards. When a fault occurs in the distribution network line, the analysis master station receives the data uploaded by a certain monitoring point signal acquisition module through wireless communication, and calls the voltage waveform, current waveform, temperature, image, ambient temperature and humidity and other data of all monitoring points on the feeder under the same bus according to the line topology, and performs analysis to realize fault line selection and location positioning.

[0055] The functions of the analysis master station include the following aspects:

[0056] 1) Data reception and processing: The master station can not only receive and call the data uploaded by the aggregation preprocessing module, but also has reserved interfaces to receive the oscillogram data of distribution automation terminals such as substation terminal DTU, feeder terminal FTU, and primary-secondary integrated switch transmitted by an external system. And perform reconstruction and fusion processing on the data, including synchronizing the data acquisition moments of each monitoring point according to the time stamps of the Global Positioning System (GPS) or Beidou satellite navigation system. Subsequently, the master station performs time alignment and truncation processing on the three-phase voltage and three-phase current waveform data received from each monitoring point of the distribution network, and removes the redundant data at the unaligned time points to ensure that the lengths and time points of all waveform data are consistent.

[0057] 2) Fault diagnosis and location: The master station superimposes the preprocessed data by the vector sum method to calculate the zero-sequence voltage and zero-sequence current of each monitoring point, and extracts the steady-state and transient signals from them respectively. The analysis master station further calculates the characteristic values of these signals, such as amplitude, average value, differential value, integral value and their combinations, and calculates the zero-sequence active power and zero-sequence reactive power of each monitoring point accordingly. By comparing the waveform similarity and polarity of the current signals and reactive power of each monitoring point, the fault and non-fault lines are confirmed and further fault location is carried out.

[0058] 3) Review and emergency repair: Once the grounding fault point is located, the analysis master station will provide a manual review mechanism to confirm the fault point and display the fault location on the Geographic Information System (GIS) map, such as Figure 2 shown, the fault point is located between monitoring point 10 and monitoring point 11. The analysis master station also supports sending the grounding fault signal to the signal acquisition module through the time-division multiplexing wireless communication network to help the on-site personnel quickly locate the fault point.

[0059] In particular, when a grounding fault occurs in the distribution network line, throughFigure 4 Five steps are used to achieve ground fault line selection and accurate positioning. As Figure 4 shown:

[0060] Step S1: Capture electric field and current data in real time to generate accurate transient recordings

[0061] Each monitoring terminal in the distribution network (such as fault indicators, DTUs, FTUs, primary-secondary integrated switches, etc.) is responsible for collecting data such as voltage, current, temperature and humidity of the distribution line in real time, and generating accurate transient recording files. These monitoring data can not only be used as the basis for line status evaluation, but also provide key basis for subsequent fault analysis. High precision is required for real-time data acquisition to ensure that the data can accurately reflect the operating conditions and instantaneous changes of the distribution line.

[0062] Step S2: Trigger the criterion at the fault moment, and synchronously upload all terminal data of the bus

[0063] When a ground fault occurs, the system automatically triggers a fault alarm according to the set criterion.

[0064] During the transient process of a single-phase ground fault, the relationship between the zero-sequence voltage (secondary) U0, zero-sequence current I0 and the transition resistance Rg is: , where k is the transformation ratio of the 10kV voltage transformer, taking 1:100 ; v is the arc suppression coil transition compensation coefficient, taking -10%; U N is the rated phase voltage, taking 10 / kV. The size of the transition resistance Rg during a ground fault directly affects the accuracy of ground fault location. Unifying the value of the withstand transition resistance is an important way and basis for different distribution automation terminals to cooperate with zero-sequence protection. At present, the general requirement for the withstand transition resistance ability of the distribution network is greater than 2000Ω. Usually, the capacitive current of the arc suppression coil grounding system is generally about 150A, and the maximum does not exceed 200A. The zero-sequence current safety threshold can be set to 200A. The zero-sequence voltage (secondary side) safety threshold can vary between 23V and 0.15U N to adjust the withstand transition resistance ability of ground fault diagnosis, improve the line selection accuracy and further identify potential line grounding defects.

[0065] When the transition resistance Rg is set to 2000Ω, the safety threshold of the zero-sequence current is taken as 200A, and the zero-sequence voltage (secondary) U0 can be calculated to be about 28V.

[0066] Therefore, the specific criterion is: when the zero-sequence current I0 exceeds 200A or the zero-sequence voltage (secondary side) U0 exceeds 28V, and the duration exceeds 0.02 seconds, the system determines that a fault has occurred and triggers an alarm. At this time, all data collection and preprocessing modules and distribution automation terminals will synchronously upload relevant data to the analysis master station.

[0067] Meanwhile, based on the line topology data of the distribution network, the analysis master station activates the data acquisition function to obtain the oscillogram data of other terminals under the faulty bus in real time, so as to ensure comprehensive data support for fault analysis.

[0068] Step S3: The algorithm combines the topology data to implement fault line selection and location.

[0069] Subsequently, the analysis master station will perform time alignment and truncation processing on the received oscillogram data, remove redundant data, and ensure data accuracy. Then, the master station uses a proprietary algorithm to analyze the zero-sequence voltage and zero-sequence current, extract steady-state and transient signals, and evaluate their characteristic values (such as amplitude, average value, etc.). These characteristic values are used for subsequent screening and location of faulty lines.

[0070] As Figure 3 shown, specifically, the following methods are used for fault location:

[0071] 1) Comparison method of transient zero-sequence current amplitude and polarity: The amplitudes of the high-frequency transient zero-sequence currents of non-faulty lines and faulty lines are different, and their polarities are opposite. The polarities of the high-frequency transient zero-sequence currents before and after the fault point on the faulty line are different.

[0072] 2) Transient zero-sequence power direction method: In non-faulty lines, the actual direction of capacitive reactive power is from the bus to the line. In faulty lines, the actual direction of capacitive reactive power is from the line to the bus. The capacitive reactive powers before and after the fault point on the faulty line are in opposite directions.

[0073] For example Figure 2 in, when a ground fault occurs between monitoring points 10 and 11, the transient zero-sequence current and the direction of capacitive reactive power at monitoring points 7, 8, and 10 are from the line to the bus, while those at the remaining monitoring points are from the bus to the line. Based on this, the fault path can be confirmed as 7>8>10, and the fault point is located after monitoring point 10 and before 11.

[0074] Step S4: Rapid notification to guide emergency repair

[0075] When the analysis master station completes fault diagnosis, the system will transmit the location result of the ground fault to the on-site emergency repair personnel in real time through the communication network. Based on the fault location and fault type information provided by the master station, the emergency repair personnel can quickly carry out emergency repair work, reduce the power outage time, and ensure that the faulty line is restored to power as soon as possible.

[0076] Step S5: Optimize and adjust the monitoring point location according to the fault statistics results

[0077] By statistically analyzing the historical fault data, the analysis master station can evaluate the coverage effect of existing monitoring points and optimize the layout positions of the monitoring points and the grounding determination basis according to the results. The accuracy of fault location depends on the layout and installation interval of on-site monitoring points. If the actual grounding faults on a certain line occur frequently and the fault location range is too large, the operation and maintenance personnel can optimize it by adjusting the monitoring point layout and adding monitoring points, so as to improve the accuracy of fault location and the emergency repair efficiency. If the statistical results of the analysis master station are inconsistent with the actual situation, such as frequent misjudgment of grounding faults, the safety threshold (from 23V to 0.15U N between) and the duration T of the zero-sequence voltage (secondary) U0 can be manually reduced, and the corresponding withstand transition resistance value is increased, so as to reduce the situation of misjudging grounding faults and improve the overall diagnostic ability and fault response speed of the system.

[0078] The above description is only for the embodiments of the present application and is not used to limit the protection scope of the present application. For those skilled in the art, various changes and modifications can be made to the present application. 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.

Claims

1. A distribution line status monitoring system, characterized in that: Including signal acquisition module, collection preprocessing module and analysis main station, The signal acquisition module is used to obtain the distribution line status and environmental data, and send the collected data to the aggregation preprocessing module; The aggregation preprocessing module is used to receive, store and process the data sent by the signal acquisition module, and actively or passively upload the data to the analysis main station according to the data processing results; The analysis main station is used to receive or call for data stored in each aggregation preprocessing module to perform line status evaluation and fault location diagnosis.

2. A distribution line status monitoring system according to claim 1, characterized in that: The signal acquisition module collects the voltage waveform, current waveform, temperature, image and ambient temperature and humidity data of the line equipment in real time through the online terminal monitoring equipment installed in the distribution network, and transmits the data to the aggregation preprocessing module. Each signal acquisition module is only responsible for signal acquisition at one monitoring point. The online terminal monitoring equipment includes a fault indicator, an infrared camera, and a temperature and humidity sensor.

3. A distribution line status monitoring system according to claim 1, characterized in that: The aggregation and preprocessing module includes a data aggregation unit, a data preprocessing unit and a communication unit. The data aggregation unit aggregates the data collected by a signal acquisition module and stores it locally. The data preprocessing unit calculates the zero-sequence voltage and zero-sequence current based on the stored three-phase voltage and three-phase current data. When the amplitude of the zero-sequence voltage or zero-sequence current exceeds the safety threshold and the duration exceeds the fixed value T, all data are actively uploaded to the analysis main station through the communication unit. Each aggregation and preprocessing module receives, stores, preprocesses and uploads the data to the analysis main station for a collection module.

4. A distribution line status monitoring system according to claim 1, characterized in that: The aggregation preprocessing module forms a wireless communication network with the signal acquisition module and the analysis main station through a communication unit using a time-division multiplexing wireless communication method. The communication unit of the aggregation preprocessing module uses GPS or Beidou timing to achieve accurate time synchronization with the signal acquisition module and the analysis main station.

5. A distribution line status monitoring system according to claim 1, characterized in that: The analysis master station receives and calls for data uploaded from the aggregation preprocessing module. The analysis master station also reserves an interface to receive distribution automation terminal recording data such as station terminal DTU, feeder terminal FTU, and primary and secondary fusion switches transmitted from an external system.

6. A distribution line status monitoring system according to claim 1, characterized in that: The analysis master station first synchronizes the data collection time of each monitoring point according to the timestamp of the global positioning system or the Beidou satellite navigation system. Subsequently, the master station performs time alignment and truncation processing on the three-phase voltage and three-phase current waveform data received from each monitoring point of the self-distribution network, and removes redundant data of unaligned time points to ensure that the length and time points of all waveform data are consistent. On this basis, the master station superimposes the pre-processed data through the vector sum method, calculates the zero-sequence voltage and zero-sequence current of each monitoring point, and extracts steady-state and transient signals therefrom respectively. The analysis master station further calculates the characteristic values ​​of these signals, and calculates the zero-sequence active power and zero-sequence reactive power of each monitoring point accordingly. By comparing the waveform similarity and polarity of the current signal and reactive power of each monitoring point, the faulty and non-faulty lines and further fault location are confirmed.

7. A method for diagnosing ground faults in a distribution network using the distribution line status monitoring system according to any one of claims 1 to 6, characterized in that: The specific steps include: S1, real-time capture of electric field and current data, generating accurate transient waveforms; S2, the fault triggers the judgment criteria at the moment, and all the terminal data of the bus are sent synchronously; S3, the algorithm combines topological data to achieve fault line selection and location; S4, rapid notification and guidance of emergency repairs; S5, optimize and adjust the monitoring point locations according to the fault statistics results.

8. The method for diagnosing ground faults in a power distribution network according to claim 7, characterized in that: In step S1, the on-site fault indicator, the station terminal DTU, the feeder terminal FTU, and the primary and secondary integrated switch distribution automation terminal collect and record the voltage and current of the distribution network line in real time to generate a transient recording file; In step S2, when a fault occurs, based on the preset threshold: the zero-sequence current I0 exceeds 200A or the zero-sequence voltage U0 exceeds 28V, and the duration T exceeds 0.02s, the criterion is triggered successfully, and the collection preprocessing module and distribution automation terminal at this location send the recording to the analysis master station. At the same time, the analysis master station calls for the voltage and current recording data of all remaining station terminals DTU, feeder terminals FTU, primary and secondary fusion switches under the same bus according to the line topology.

9. The method for diagnosing ground faults in a power distribution network according to claim 7, characterized in that: In step S3, the analysis master station performs time alignment and truncation processing on the received and called recording files, removes redundant data at unaligned time points, and calculates the zero-sequence voltage and zero-sequence current of each monitoring point, extracts steady-state and transient signals respectively, calculates the characteristic values ​​of these signals, and realizes fault line selection and position positioning according to the positioning and judgment principle of ground fault.

10. The method for diagnosing ground faults in a power distribution network according to claim 7, characterized in that: In step S4, by analyzing the ground fault location conclusion given by the master station, the emergency repair personnel are guided to rush to the scene quickly to carry out emergency repair and power supply; In step S5, based on the on-site verification of the ground fault analysis accuracy, according to the formula , k is the 10kV voltage transformer ratio, v is the arc suppression coil transition compensation coefficient, U N is the rated phase voltage, R g Transition resistance: When the safety threshold of zero-sequence current I0 is 200A, if there are many cases of missed ground faults in the on-site statistics, the safety threshold and duration T of zero-sequence voltage U0 will be reduced, and the corresponding transition resistance value will be increased, thereby reducing the cases of missed ground faults.

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