Distribution network line fault early warning and inspection method

Abstract

The invention discloses a distribution network line fault early warning and inspection method, and relates to the technical field of distribution network line monitoring, and the method comprises the steps: monitoring and collecting the electrical parameters of a distribution network line in real time, carrying out the preprocessing of the electrical parameters, extracting a power frequency signal of the distribution network line, and carrying out the calculation to obtain a power frequency electric field and a power frequency magnetic field; performing electrical dynamic analysis on the operation state of the power frequency electric field to obtain a first analysis result, and synchronously performing electrical dynamic analysis on the operation state of the power frequency magnetic field to obtain a second analysis result; whether the distribution network line is abnormal or not is judged based on the first analysis result and the second analysis result, if yes, fault early warning is initiated, and secondary study and judgment are conducted on whether the distribution network line breaks down or not; if not, continuing to collect the electrical parameters to monitor the operation state of the distribution network line; if the distribution network line fault is judged through secondary research, obtaining a fault traveling wave to position a fault point of the distribution network line; and the reliability of fault monitoring of the distribution network line and the accuracy of fault positioning are obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network line monitoring, and in particular to a distribution network line fault early warning and inspection method. Background Art

[0002] At present, various distribution network fault monitoring devices have realized the fault analysis function to a certain extent, but it is still difficult to achieve "precise location" for the detection of specific fault points in the distribution network line. After the fault occurs, a lot of manpower and material resources are still needed to find the fault and analyze the cause of the fault. The existing technology uses intrusive monitoring equipment installed on the distribution network line for fault detection. It determines whether the distribution network line has a fault by detecting the current changes of the three-phase conductors and locates the section fault. However, due to the complexity of the distribution network and the intricacy of the lines, it is difficult to accurately locate the line fault in the first time and it is impossible to determine the fault type in the first time.

[0003] Chinese patent, publication number: CN117406032B, publication date: March 26, 2024, discloses a method for early fault detection and section positioning of medium-voltage distribution network cables, which monitors and identifies early faults through the grounding current characteristics of the cable shield layer, effectively monitors the current changes when early faults occur in the low-resistance grounding system, reduces the interference of factors such as noise, and realizes the fault section positioning of early faults in the medium-voltage distribution network and improves the accuracy of identification. However, this invention mainly detects and locates early grounding faults of medium-voltage cables by intrusive monitoring and measuring the changes in zero-sequence current in the three-phase current in the cable, which will cause certain intrusion to the cable system and increase the possibility of new fault points in the cable. In addition, zero-sequence current monitoring mainly monitors the current changes inside the cable, which is not sensitive enough to external environmental factors, resulting in insufficient comprehensive and flexible monitoring of the operating status of the distribution network line, and cannot directly reflect the operating status of the distribution network line. Summary of the invention

[0004] The purpose of the present invention is to address the problem that the reliability of fault monitoring of distribution network lines is poor due to the failure to comprehensively consider the dynamic changes of cable electromagnetic fields in existing distribution network line monitoring technologies; a distribution network line fault early warning and inspection method is proposed, and the power frequency signal of the distribution network line is collected by a non-contact fault early warning and inspection device for the distribution network line to obtain the power frequency electric field and the power frequency magnetic field, and the operating states of the power frequency electric field and the power frequency magnetic field are electrically and dynamically analyzed respectively, and the fault state of the distribution network line is warned and secondary judged. If a fault occurs in the distribution network line, high-frequency traveling waves are collected to calculate the precise fault point, and the dynamic changes of the cable electromagnetic field are fully considered, which significantly improves the reliability of fault monitoring and the accuracy of fault location.

[0005] In order to solve the above technical problems, a distribution network line fault early warning and inspection method is provided, comprising the following steps: S1. Real-time monitoring and collection of electrical parameters of the distribution network line, preprocessing of the electrical parameters and extraction of the power frequency signal of the distribution network line, and calculation of the power frequency electric field and the power frequency magnetic field based on the power frequency signal; S2. Performing an electrical dynamic analysis on the operating state of the power frequency electric field to obtain a first analysis result of the power frequency electric field, and performing an electrical dynamic analysis on the operating state of the power frequency magnetic field to obtain a second analysis result of the power frequency magnetic field; S3, judging whether the distribution network line is abnormal based on the first analysis result and the second analysis result, if so, executing S4; if not, executing S1; S4, initiating a fault warning based on the first analysis result and the second analysis result, and conducting a secondary analysis on whether a fault occurs in the distribution network line. If so, executing S5; if not, executing S1; S5. Acquire a fault traveling wave of the distribution network line, and locate the fault point of the distribution network line according to the transmission time characteristics of the fault traveling wave.

[0006] In this solution, by real-time monitoring of the operating status of the distribution network line, the electrical parameter data of the distribution network line, including voltage, current, power factor, load change, etc., can be continuously obtained to ensure the real-time and accuracy of the data and provide a reliable data basis for subsequent fault analysis; the collected electrical parameters are preprocessed to remove noise and interference, improve data quality, and extract the power frequency signal to calculate the accurate power frequency electric field and power frequency magnetic field, so as to accurately judge the actual operating condition of the distribution network line according to the changes of the power frequency electric field and the power frequency magnetic field; the extracted power frequency electric field and power frequency magnetic field are comprehensively and deeply analyzed to obtain their change characteristics or abnormal information, so as to judge whether the distribution network line has a fault. Since there are many factors that cause current changes or voltage changes in the distribution network line, short-term current fluctuations or voltage fluctuations do not mean that the distribution network line has an abnormality or fault. Therefore, through comprehensive judgment, the accuracy of fault detection is improved and false alarms and missed alarms are reduced; when it is detected that there may be a fault in the distribution network line, a fault warning is initiated, and a secondary judgment is conducted to further confirm whether the fault really exists. The warning can help relevant personnel to discover and deal with potential problems in a timely manner. Therefore, it is necessary to monitor and analyze the power frequency electric field and the power frequency magnetic field. When the power frequency electric field changes, the changing trend of the power frequency magnetic field is further analyzed. When both the power frequency electric field and the power frequency magnetic field are abnormal, the distribution network line fails and a fault traveling wave is generated. By obtaining the fault traveling wave and quickly calculating the precise fault point based on its transmission time characteristics, it helps to shorten the fault repair time, fully consider the dynamic changes of the cable electromagnetic field, and significantly improve the reliability of fault monitoring and the accuracy of fault location.

[0007] Preferably, in S1, real-time monitoring and acquisition of electrical parameters of the distribution network line, preprocessing of the electrical parameters and extraction of the power frequency signal of the distribution network line include the following sub-steps: S11, collecting electrical parameters of the distribution network line based on the power frequency sensor, and transmitting the electrical parameters to the main station server through directional encrypted wireless communication technology; S12, filtering, denoising and synchronizing the electrical parameters to obtain an electrical parameter feature set in a standard format; S13, extracting power frequency features from the electrical parameter feature set to obtain the power frequency signal.

[0008] Preferably, in S1, calculating the power frequency electric field and the power frequency magnetic field based on the power frequency signal includes the following sub-steps: S14. Analyze the distribution response factors of the electric field and magnetic field in the distribution network line based on the distribution network topology diagram and establish an electromagnetic field model; S15. Determine the constraint conditions and initial variables of the electromagnetic field model according to the actual operating conditions of the distribution network line; S16. Using the power frequency signal as the input of the electromagnetic field model to calculate the power frequency electric field and the power frequency magnetic field.

[0009] Preferably, the distribution response factors at least include the distance between the conductor and the ground, the spatial distribution of the conductor, the phase sequence arrangement, the conductor splitting information and the line distribution characteristics.

[0010] In this scheme, the security and real-time performance of data transmission are ensured by encrypting the collected electrical parameters during transmission, avoiding network delays and other problems that result in the electrical parameters not being sent to the master server in time, resulting in delays in fault repair and causing adverse effects. At the same time, it ensures that there are no risks such as data frame loss and data anomalies during data transmission. The electrical parameters are filtered, denoised and synchronously processed to improve the accuracy and reliability of the electrical parameter data, and obtain data in a unified format for subsequent feature extraction and analysis, so as to accurately obtain the power frequency signal from the electrical parameter feature set, and provide high-quality input data for the establishment of the electromagnetic field model. The distribution response factors of the electric field and magnetic field in the distribution network line are analyzed through the distribution network topology diagram and the electromagnetic field model is established, which can accurately reflect the electromagnetic field distribution of the actual distribution network line, so as to facilitate the intuitive and clear analysis of the operation status of the distribution network line. The constraints and initial variables of the electromagnetic field model are determined according to the actual operation conditions of the distribution network line, which can make the model more consistent with the actual operation conditions, improve the accuracy of the calculation results, and provide an important reference basis for the analysis of the operation status of the distribution network line. Through accurate electromagnetic field calculation and analysis, effective monitoring and early warning means are provided for the safe operation of the distribution network line, reducing the risk of accidents and improving the power supply quality.

[0011] Preferably, S2 comprises the following sub-steps: S21, performing a steady-state analysis on the power frequency electric field to obtain a first steady-state analysis result of the power frequency electric field, and performing a transient analysis on the power frequency electric field to obtain a first transient analysis result of the power frequency electric field; S22, performing a steady-state analysis on the power frequency magnetic field to obtain a second steady-state analysis result of the power frequency magnetic field, and performing a transient analysis on the power frequency magnetic field to obtain a second transient analysis result of the power frequency magnetic field; S23. Use the first steady-state analysis result and the first transient analysis result as the first analysis result, and use the second steady-state analysis result and the second transient analysis result as the second analysis result.

[0012] Preferably, the S21 includes the following sub-steps: S211, establishing a first steady-state model of the power frequency electric field based on the topological structure of the distribution network line and the power frequency voltage information, taking the electrical parameters as input of the first steady-state model, solving the first steady-state model, and obtaining a steady-state value of the electrical quantity of the distribution network line; S212, calculating the power frequency electric field distribution characteristics of the distribution network line according to the steady-state value of the electrical quantity, comparing and analyzing the power frequency electric field distribution characteristics with the standard power frequency electric field characteristics, and obtaining the first steady-state analysis result; S213, establishing a first transient model of the power frequency electric field based on the operating conditions and historical transient information of the distribution network line, taking the electrical parameters as input of the first steady-state model, solving the first transient model, and obtaining a transient response of the electrical quantity of the distribution network line; S214. Analyze the transient condition of the distribution network line through the transient response of the electrical quantity to obtain the first transient analysis result.

[0013] Preferably, the S22 comprises the following sub-steps: S221. Establishing a second steady-state model of the power frequency magnetic field based on the power frequency current information in the distribution network line, solving the second steady-state model, and obtaining a steady-state distribution of the power frequency magnetic field in the distribution network line; S222, comparing and analyzing the steady-state distribution of the power frequency magnetic field with the standard power frequency magnetic field distribution characteristics to obtain the second steady-state analysis result; S223, establishing a second transient model of the power frequency magnetic field based on the operating conditions and historical transient information of the distribution network line, taking the electrical parameters as input of the second transient model for calculation, and obtaining transient response data of the power frequency magnetic field during the transient process of the distribution network line; S224. Analyze the transient condition of the distribution network line through the transient response data of the power frequency magnetic field to obtain the second transient analysis result.

[0014] In this solution, by performing steady-state analysis on the power frequency electric field and the power frequency magnetic field, we can understand the performance of the distribution network under normal operating conditions, such as whether the load is balanced, whether the equipment is overloaded, whether the voltage is stable, and the distribution characteristics of the electric field and the magnetic field. By monitoring these steady-state signals in real time, we can determine whether the distribution network is in normal operation. If the steady-state signals are abnormal, such as voltage fluctuations, current imbalance, etc., it may indicate potential fault risks, so as to facilitate fault warning. Transient analysis of the power frequency electric field and the power frequency magnetic field can capture the instantaneous changes in electrical parameters caused by some reasons (such as lightning strikes, equipment failures, etc.). Transient analysis can extract fault information of the distribution network, such as fault type, etc. The fault characteristics can provide an important basis for fault analysis; through the steady-state and transient analysis of the electric field and magnetic field, the basic operating status of the distribution network line and the steady-state value of the electrical quantity can be understood, providing a basis for optimizing the operating parameters; the faults in the distribution network line can be detected more accurately to avoid missed reports and false alarms. At the same time, the faults can be discovered in time and corresponding treatment measures can be taken to shorten the fault recovery time; in addition, the changes in electrical parameters during the transition from the original stable state to the new stable state can be obtained, as well as the impact of these changes on the operating status of the distribution network line, so as to evaluate the response capability, recovery capability and stability performance of the distribution network after disturbance, thereby guiding the planning, design and operation of the distribution network line.

[0015] Preferably, S3 includes the following sub-steps: S31, judging whether a distribution network line fails based on the first steady-state analysis result and the second steady-state analysis result, if one and only one of the first steady-state analysis result and the second steady-state analysis result is abnormal, executing S4; if both the first steady-state analysis result and the second steady-state analysis result are abnormal, executing S5; S32. Determine whether a distribution network line fault occurs based on the first transient analysis result and the second transient analysis result. If one and only one of the first transient analysis result and the second transient analysis result is abnormal, execute S4; if both the first transient analysis result and the second transient analysis result are abnormal, execute S5.

[0016] In this scheme, through the combined judgment of steady-state and transient analysis results, it is possible to detect the early stage of the distribution network line fault, which is helpful to timely discover potential problems, avoid further development of faults, and reduce the impact of faults on the operation of distribution network lines; when judging faults, the steady-state and transient analysis results of electric and magnetic fields are considered at the same time to ensure that fault detection is more comprehensive and accurate, which helps to reduce false alarms and missed alarms and improve the reliability of fault detection; based on the steady-state and transient analysis of actual operation data, fault detection and processing are more scientific and reasonable. This helps to achieve data-driven decision-making and improve the intelligent level of distribution network line management; different processing strategies are adopted according to different analysis results, making the monitoring and abnormal processing of the distribution network line operation status more flexible, so as to be able to deal with different types of faults more efficiently and improve the efficiency of fault processing; at the same time, early detection of faults and taking corresponding measures can help prevent the further expansion of faults, reduce the damage caused by faults to distribution network lines, and improve the safety, reliability and operation efficiency of distribution network lines; through automated fault detection and analysis, the workload of manual inspections is reduced and the inspection efficiency is improved.

[0017] Preferably, S4 includes the following sub-steps: The fault warning is initiated according to the abnormal analysis results of the power frequency electric field and the power frequency magnetic field, and the high-frequency traveling wave state of the distribution network line is monitored, and the fault state of the distribution network line is secondary analyzed. If a high-frequency traveling wave is generated, S5 is executed; if no high-frequency traveling wave is generated, S1 is executed within the standard abnormal disturbance time range.

[0018] In this scheme, after the initial judgment is abnormal, the authenticity and severity of the fault can be further confirmed by monitoring the high-frequency traveling wave state for secondary analysis, ensuring the accuracy of the fault judgment; after confirming the fault, timely starting the fault warning can remind the operation and maintenance personnel to take prompt measures to avoid further expansion of the fault; through secondary analysis, some abnormal signals caused by interference or misjudgment can be eliminated, reducing false alarms and missed alarms, which helps to improve the reliability and accuracy of fault detection; according to the results of the secondary analysis, high-frequency traveling wave information can be collected in time, the fault point can be quickly located, the fault repair time can be shortened, the efficiency of fault handling can be improved, the impact of the fault on the distribution network line can be reduced, and the reliability and stability of the distribution network line can be improved.

[0019] Preferably, S5 comprises the following sub-steps: S51, collecting high-frequency traveling wave signals of the target distribution network line through an industrial frequency sensor; S52. Calculate the traveling wave time difference between the high-frequency traveling wave signal and the two ends of the target distribution network line based on the two-terminal traveling wave ranging method, and locate the fault point in the target distribution network line.

[0020] In this scheme, the two-terminal traveling wave ranging method can accurately calculate the position of the fault point by accurately measuring the time difference of the high-frequency traveling wave signal propagating from the fault point to both ends of the line, thereby realizing the precise positioning of the fault point; since the two-terminal traveling wave ranging method can quickly calculate the position of the fault point, it can realize a rapid response to the distribution network line fault, which helps to shorten the fault recovery time and improve the power supply reliability and stability; by accurately measuring the time difference of the high-frequency traveling wave signal, the two-terminal traveling wave ranging method can reduce the false alarm and missed alarm caused by signal interference or misjudgment, thereby improving the accuracy and reliability of fault detection.

[0021] Beneficial effects of the present invention: By acquiring the power frequency electric field and power frequency magnetic field through the non-contact fault warning and inspection device of the distribution network line, conducting a comprehensive and in-depth analysis of the power frequency electric field and the power frequency magnetic field, and obtaining their changing characteristics or abnormal information, it is possible to determine whether a fault has occurred in the distribution network line, improve the accuracy of fault detection, and reduce false alarms and missed alarms; when a possible fault is detected in the distribution network line, a fault warning is initiated, and a secondary analysis is conducted to further confirm whether the fault actually exists. According to the results of the secondary analysis, high-frequency traveling wave information can be collected in time, the fault point can be quickly located, the fault repair time can be shortened, the efficiency of fault handling can be improved, the impact of the fault on the distribution network line can be reduced, and the reliability and stability of the distribution network line can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings. The drawings are only for the purpose of illustrating preferred embodiments and are not to be considered as limiting the present invention. Also, the same reference symbols are used throughout the drawings to represent the same parts.

[0023] Figure 1 The present invention is a flow chart of a method for early warning and inspection of distribution network line faults according to an embodiment of the present invention.

[0024] Figure 2 The figure is a schematic diagram of high-frequency traveling wave transmission according to an embodiment of the present invention.

[0025] Figure 3 The present invention is a schematic diagram of a non-contact fault warning and inspection organizational structure. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation method described herein is only an optimal embodiment of the present invention, which is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] Example 1: Figure 1 As shown, a distribution network line fault warning and inspection method includes steps S1-S5, wherein: S1, based on the distribution network line non-contact fault warning and inspection device, real-time monitoring and collection of electrical parameters of the distribution network line, pre-processing the electrical parameters and extracting the power frequency signal of the distribution network line, based on the power frequency signal, calculating the power frequency electric field and the power frequency magnetic field.

[0028] Specifically, in S1, real-time monitoring and acquisition of electrical parameters of the distribution network line, preprocessing of the electrical parameters and extraction of the power frequency signal of the distribution network line include the following sub-steps: S11, collecting electrical parameters of the distribution network line based on the power frequency sensor, and transmitting the electrical parameters to the main station server through directional encrypted wireless communication technology; S12, filtering, denoising and synchronizing the electrical parameters to obtain an electrical parameter feature set in a standard format; S13. Extracting power frequency features from the electrical parameter feature set to obtain a power frequency signal.

[0029] Specifically, in S1, calculating the power frequency electric field and the power frequency magnetic field based on the power frequency signal includes the following sub-steps: S14. Analyze the distribution response factors of the electric field and magnetic field in the distribution network line based on the distribution network topology diagram and establish an electromagnetic field model; S15. Determine the constraints and initial variables of the electromagnetic field model according to the actual operating conditions of the distribution network line; S16. Use the industrial frequency signal as the input of the electromagnetic field model to calculate the industrial frequency electric field and the industrial frequency magnetic field.

[0030] Specifically, the distribution response factor includes at least the distance between the conductor and the ground, the spatial distribution of the conductor, the phase sequence arrangement, the conductor splitting information and the line distribution characteristics.

[0031] It is understandable that increasing the installation height of the conductor can reduce the power frequency electric field strength above the ground. However, as the conductor height gradually increases, the effect of increasing the conductor height on reducing the ground power frequency electric field will gradually weaken. At the same time, increasing the conductor height will also reduce the power frequency magnetic field below the line. But after the conductor height increases to a certain extent, the effect of increasing the conductor height on reducing the power frequency magnetic field will become smaller and smaller. For single-circuit transmission lines, the conductors are arranged in three ways: horizontal, regular triangle and inverted triangle. Different arrangements will affect the maximum value and corridor width of the ground power frequency electric field below the line. Using a single-circuit inverted triangle In the case of triangular arrangement, the maximum value of the power frequency electric field and the corridor width under the line are smaller than those under the other two methods; for multi-circuit transmission lines on the same tower, the phase conductors are arranged in different phase sequences, and the power frequency electric field synthesis effect generated by the voltage of each phase conductor in space is different; different phase sequence arrangements will affect the power frequency electric field strength and magnetic induction intensity; the influence of the number of split conductors on the electric field strength in the space under the transmission line is a factor that is easily overlooked in power design. In the design of high-voltage lines, in order to increase the transmission capacity of the line, the method of splitting conductors is often used, but the increase in the number of split conductors will increase the power frequency electric field strength under the line. Therefore, when establishing an electromagnetic field model, it is necessary to comprehensively consider the distribution response factors of the electric field and magnetic field in the distribution network line to establish an accurate and highly adaptable electromagnetic field model to ensure the reliability and feasibility of the electromagnetic field model and provide guarantee for the subsequent analysis of distribution network line fault information.

[0032] S2. Perform an electrical dynamic analysis on the operating state of the power frequency electric field to obtain a first analysis result of the power frequency electric field, and perform an electrical dynamic analysis on the operating state of the power frequency magnetic field to obtain a second analysis result of the power frequency magnetic field.

[0033] Specifically, S2 includes the following sub-steps: S21, performing a steady-state analysis on the power frequency electric field to obtain a first steady-state analysis result of the power frequency electric field, and performing a transient analysis on the power frequency electric field to obtain a first transient analysis result of the power frequency electric field; S22, performing a steady-state analysis on the power frequency magnetic field to obtain a second steady-state analysis result of the power frequency magnetic field, and performing a transient analysis on the power frequency magnetic field to obtain a second transient analysis result of the power frequency magnetic field; S23. Taking the first steady-state analysis result and the first transient analysis result as the first analysis result, and taking the second steady-state analysis result and the second transient analysis result as the second analysis result.

[0034] Specifically, S21 includes the following sub-steps: S211, establishing a first steady-state model of the power frequency electric field based on the topological structure of the distribution network line and the power frequency voltage information, taking the electrical parameters as the input of the first steady-state model, solving the first steady-state model, and obtaining the steady-state value of the electrical quantity of the distribution network line; S212, calculating the power frequency electric field distribution characteristics of the distribution network line according to the steady-state value of the electrical quantity, comparing and analyzing the power frequency electric field distribution characteristics with the standard power frequency electric field characteristics, and obtaining a first steady-state analysis result; S213, establishing a first transient model of the power frequency electric field based on the operating conditions and historical transient information of the distribution network line, taking the electrical parameters as the input of the first steady-state model, solving the first transient model, and obtaining the transient response of the electrical quantity of the distribution network line; S214. Analyze the transient condition of the distribution network line through the transient response of the electrical quantity to obtain a first transient analysis result.

[0035] Specifically, S22 includes the following sub-steps: S221, establishing a second steady-state model of the power frequency magnetic field based on the power frequency current information in the distribution network line, solving the second steady-state model, and obtaining a steady-state distribution of the power frequency magnetic field in the distribution network line; S222, comparing and analyzing the steady-state distribution of the power frequency magnetic field with the standard power frequency magnetic field distribution characteristics to obtain a second steady-state analysis result; S223, establishing a second transient model of the power frequency magnetic field based on the operating conditions and historical transient information of the distribution network line, calculating the electrical parameters as input of the second transient model, and obtaining transient response data of the power frequency magnetic field during the transient process of the distribution network line; S224. Analyze the transient condition of the distribution network line through the transient response data of the power frequency magnetic field to obtain a second transient analysis result.

[0036] Specifically, the first steady-state model and the second steady-state model can be solved by circuit analysis methods or electromagnetic field calculation methods. The circuit analysis method can use Kirchhoff's law, etc. By applying Kirchhoff's current law, the location of the fault can be quickly determined, such as identifying the fault node by measuring the current changes in each branch; the electromagnetic field calculation method can use finite element method, boundary element method, etc., which can simulate the dynamic response of the line under different working conditions, such as voltage fluctuations, current transients, etc., and consider the coupling effect between the line and other equipment or the environment, such as the influence of soil and buildings on the electromagnetic field, to improve the accuracy of fault diagnosis, so as to obtain the steady-state distribution of current and magnetic field; the first transient model and the second transient model can be solved by using time-domain finite difference method, etc., to obtain the changes of current and magnetic field in the transient process, and obtain the transient response of current and magnetic field. Among them, the time-domain finite difference method can directly simulate the dynamic response of the circuit in the time domain, which is very effective for analyzing transient faults such as short circuit or insulation breakdown, and can also handle various types of circuit elements and complex geometric structures. It has strong adaptability and is suitable for the diversity of distribution network lines.

[0037] In this embodiment, steady-state analysis of the power frequency electric field and the power frequency magnetic field can reflect the electric field and magnetic field distribution characteristics of the distribution network line under normal operating conditions. By establishing and solving a steady-state model, the steady-state values ​​of the electrical quantities of the distribution network line, such as voltage and current, can be obtained, so as to understand the basic operating status of the distribution network line; according to the first steady-state analysis result and the second steady-state analysis result, it can be comprehensively evaluated whether the operating status of the distribution network line meets expectations, and whether the distribution network line has a fault can be judged according to the comprehensive result to ensure the accuracy of fault inspection; transient analysis of the power frequency electric field and the power frequency magnetic field can reflect the electric field and magnetic field change characteristics of the distribution network line during transient processes such as faults or operations. By establishing and solving a transient model, the transient response of the electrical quantities of the distribution network line, such as overvoltage and overcurrent, can be obtained, so as to understand the performance of the distribution network line in the transient process; by monitoring and analyzing the transient response data, faults or abnormal conditions in the distribution network line can be discovered in time, so as to take corresponding treatment measures as soon as the fault occurs, avoid the occurrence or expansion of accidents, and ensure the safe and stable operation of the distribution network line.

[0038] S3. Based on the first analysis result of the power frequency electric field and the second analysis result of the power frequency magnetic field, determine whether the distribution network line is abnormal. If so, execute S4; if not, execute S1.

[0039] Specifically, S3 includes the following sub-steps: S31, judging whether a distribution network line fails based on the first steady-state analysis result and the second steady-state analysis result, if only one of the first steady-state analysis result and the second steady-state analysis result is abnormal, executing S4; if both the first steady-state analysis result and the second steady-state analysis result are abnormal, executing S5; S32. Determine whether a distribution network line fault occurs based on the first transient analysis result and the second transient analysis result. If one and only one of the first transient analysis result and the second transient analysis result is abnormal, execute S4; if both the first transient analysis result and the second transient analysis result are abnormal, execute S5.

[0040] In this embodiment, by analyzing the steady-state and transient characteristics of the electric field and the magnetic field, characteristic information related to the fault, such as frequency, amplitude, duration, etc., can be extracted to facilitate the prediction and identification of faults in the distribution network line. Once a fault is detected, the fault location can be quickly located, the cause of the fault can be analyzed, and corresponding treatment measures can be taken to ensure the safe and stable operation of the distribution network line. For example, if the power frequency electric field changes abnormally and the power frequency magnetic field also changes abnormally, it indicates that the distribution network line has a fault, and it is necessary to locate and repair the fault and other corresponding fault treatments; for example, if the power frequency electric field changes abnormally and the power frequency magnetic field is normal or the power frequency electric field is normal and the power frequency magnetic field is abnormal, a fault warning is initiated, and the change trend of the power frequency electric field or the power frequency magnetic field is specifically analyzed. The change state of the power frequency electric field or the power frequency magnetic field is continuously monitored within the allowed abnormal change time limit, and the abnormal state is further analyzed. If the abnormal change returns to normal within the allowed time range, it indicates that the distribution network line has not failed. Otherwise, S5 is executed to monitor and collect high-frequency traveling wave information and locate the fault point.

[0041] S4. Initiate a fault warning based on the first analysis result and the second analysis result, and conduct a secondary analysis on whether a fault occurs in the distribution network line. If so, execute S5; if not, execute S1.

[0042] Specifically, S4 includes the following sub-steps: The fault warning is initiated based on the abnormal analysis results of the power frequency electric field and the power frequency magnetic field, and the high-frequency traveling wave state of the distribution network line is monitored. The fault state of the distribution network line is secondary analyzed. If a high-frequency traveling wave is generated, S5 is executed; if no high-frequency traveling wave is generated, S1 is executed within the standard abnormal disturbance time range.

[0043] In this embodiment, after the initial judgment is abnormal, the authenticity and severity of the fault can be further confirmed by monitoring the high-frequency traveling wave state for secondary judgment; high-frequency traveling waves are a unique phenomenon generated when the distribution network line fails, which can directly reflect the location and nature of the fault. Therefore, by monitoring the high-frequency traveling wave state, the accuracy of fault judgment can be improved. After confirming the fault, timely starting the fault warning can remind the operation and maintenance personnel to take prompt measures to avoid further expansion of the fault; through secondary judgment, some abnormal signals caused by interference or misjudgment can be eliminated, and the situation of false alarms and missed alarms can be reduced, which helps to improve the reliability and accuracy of fault detection.

[0044] S5. Obtain the fault traveling wave of the distribution network line, and locate the fault point of the distribution network line according to the transmission time characteristics of the fault traveling wave.

[0045] Specifically, S5 includes the following sub-steps: S51, collecting high-frequency traveling wave signals of the target distribution network line through an industrial frequency sensor; S52. Calculate the traveling wave time difference between the high-frequency traveling wave signal and the two ends of the target distribution network line based on the two-terminal traveling wave ranging method, and locate the fault point in the target distribution network line.

[0046] Specifically, Figure 2 As shown, the calculation formula of the double-terminal traveling wave ranging method is as follows: Where L represents the bus length of high-frequency traveling wave transmission, t m It represents the time when the high-frequency traveling wave reaches the first end of the busbar, t n It represents the time when the high-frequency traveling wave reaches the other end of the bus, and v represents the speed at which the high-frequency traveling wave is transmitted in the bus.

[0047] In this embodiment, the fault point is located by the double-end traveling wave ranging method. Unlike the single-end method, it does not need to utilize the refraction and reflection of the traveling wave. It only needs to detect the head of the first traveling wave emitted by the fault point and arriving at the traveling wave monitoring point to locate the fault. It is simple and efficient, and significantly improves the efficiency of locating distribution network line faults.

[0048] Embodiment 2, as Figure 3 As shown, this embodiment provides a non-contact fault warning and inspection device for distribution network lines, which is applicable to a distribution network line fault warning and inspection method. The non-contact fault warning and inspection device is fixedly installed on the pole tower by means of a clamp or a steel rolled strip, and is 2 to 3 meters below the conductor. The working power is provided by photovoltaic power generation. By using the high-precision and wide-band sensing application technology of the power frequency sensor, non-conductor intrusive real-time recording is performed to completely record the power frequency and transient signal change characteristics, and trigger the collection of high-frequency traveling waves in real time. The steady-state, transient and high-frequency traveling wave pulse characteristics are comprehensively combined to comprehensively judge the distribution network line fault, which significantly improves the accuracy of fault judgment. Among them, the power frequency sensor can be a differential ring sensor, which collects the synthetic electric field generated by the current in the three-phase conductor, which is similar to the magnetic field generated by the zero-sequence current. When a short circuit or metallic grounding occurs in the line, the line current changes, and the synthetic power frequency magnetic field collected by the power frequency current sensor will also change accordingly, thereby reflecting the line fault.

[0049] Furthermore, the non-contact fault warning and inspection device for distribution network lines can monitor and issue warnings for multiple single-phase grounding situations at the same location within a short period of time, so as to promptly remind the staff and solve the hidden dangers of the line in time. As a specific example analysis, the advantages of the non-contact fault warning and inspection method for distribution network lines compared with other existing technologies are shown in Table 1. Table 1 Comparative advantages of non-contact fault warning and inspection methods for distribution network lines The non-contact fault warning and inspection device for distribution network lines can also be used in combination with overhead fault locating equipment or switches with traveling wave function. The overhead fault locating equipment or switches with traveling wave function are installed at the main line switch or other key positions, and the non-contact fault warning and inspection device for distribution network lines is installed at the branch line to accurately determine the type of fault, while reducing the cost of precise positioning of the entire line.

[0050] Beneficial effects of the embodiment: By analyzing the steady state and transient state of the electric field and magnetic field, faults in the distribution network can be detected more accurately to avoid missed reports and false reports. At the same time, faults can be discovered in time and corresponding treatment measures can be taken to shorten the fault recovery time. Through steady state analysis, the basic operating status and steady state value of electrical quantities of the distribution network can be understood, providing a basis for optimizing operating parameters. By adjusting the operating parameters, the power supply quality and operating efficiency of the distribution network can be improved. In steady state, the electrical parameters of the distribution network, such as voltage, current, power factor, etc., remain relatively stable over a period of time without obvious fluctuations or changes. Through steady-state analysis, we can understand the performance of the distribution network under normal operating conditions, such as whether the load is balanced, whether the equipment is overloaded, whether the voltage is stable, etc.; through transient analysis and high-frequency traveling wave detection, we can promptly discover potential safety hazards and abnormal conditions in the distribution network lines, and take corresponding treatment measures. High-frequency traveling wave pulses are usually caused by local discharge, short circuit and other faults in the distribution network system. Through real-time monitoring and analysis of high-frequency traveling wave pulse characteristics, the source of the fault can be quickly discovered and the fault location can be accurately located, which helps to avoid the occurrence or expansion of accidents and improve the reliability and safety of distribution network lines.

[0051] The above specific embodiments are preferred embodiments of the present invention, and are not intended to limit the specific implementation scope of the present invention. The scope of the present invention includes but is not limited to the present specific embodiments. All equivalent changes made in accordance with the shape, structure, and method of the present invention are within the protection scope of the present invention.

Claims

1. A distribution network line fault early warning and inspection method, characterized in that: The steps include: S1. Real-time monitoring and collection of electrical parameters of the distribution network line, preprocessing of the electrical parameters and extraction of the power frequency signal of the distribution network line, and calculation of the power frequency electric field and the power frequency magnetic field based on the power frequency signal; S2. Performing an electrical dynamic analysis on the operating state of the power frequency electric field to obtain a first analysis result of the power frequency electric field, and performing an electrical dynamic analysis on the operating state of the power frequency magnetic field to obtain a second analysis result of the power frequency magnetic field; S3, judging whether the distribution network line is abnormal based on the first analysis result and the second analysis result, if so, executing S4; if not, executing S1; S4, initiating a fault warning based on the first analysis result and the second analysis result, and conducting a secondary analysis on whether a fault occurs in the distribution network line. If so, executing S5; if not, executing S1; S5. Acquire a fault traveling wave of the distribution network line, and locate the fault point of the distribution network line according to the transmission time characteristics of the fault traveling wave.

2. A distribution network line fault early warning and inspection method according to claim 1, characterized in that: In S1, real-time monitoring and acquisition of electrical parameters of the distribution network line, preprocessing of the electrical parameters and extraction of the power frequency signal of the distribution network line include the following sub-steps: S11, collecting electrical parameters of the distribution network line based on the power frequency sensor, and transmitting the electrical parameters to the master station server through directional encrypted wireless communication technology; S12, filtering, denoising and synchronizing the electrical parameters to obtain an electrical parameter feature set in a standard format; S13, extracting power frequency features from the electrical parameter feature set to obtain the power frequency signal.

3. A distribution network line fault early warning and inspection method according to claim 2, characterized in that: In S1, calculating the power frequency electric field and the power frequency magnetic field based on the power frequency signal includes the following sub-steps: S14. Analyze the distribution response factors of the electric field and magnetic field in the distribution network line based on the distribution network topology diagram and establish an electromagnetic field model; S15. Determine the constraint conditions and initial variables of the electromagnetic field model according to the actual operating conditions of the distribution network line; S16. Using the power frequency signal as the input of the electromagnetic field model to calculate the power frequency electric field and the power frequency magnetic field.

4. A distribution network line fault early warning and inspection method according to claim 3, characterized in that: The distribution response factors at least include the distance between the conductor and the ground, the spatial distribution of the conductor, the phase sequence arrangement, the conductor splitting information and the line distribution characteristics.

5. A distribution network line fault early warning and inspection method according to claim 1, characterized in that: The S2 comprises the following sub-steps: S21, performing a steady-state analysis on the power frequency electric field to obtain a first steady-state analysis result of the power frequency electric field, and performing a transient analysis on the power frequency electric field to obtain a first transient analysis result of the power frequency electric field; S22, performing a steady-state analysis on the power frequency magnetic field to obtain a second steady-state analysis result of the power frequency magnetic field, and performing a transient analysis on the power frequency magnetic field to obtain a second transient analysis result of the power frequency magnetic field; S23. Use the first steady-state analysis result and the first transient analysis result as the first analysis result, and use the second steady-state analysis result and the second transient analysis result as the second analysis result.

6. A distribution network line fault early warning and inspection method according to claim 4, characterized in that: The S21 includes the following sub-steps: S211, establishing a first steady-state model of the power frequency electric field based on the topological structure of the distribution network line and the power frequency voltage information, taking the electrical parameters as input of the first steady-state model, solving the first steady-state model, and obtaining a steady-state value of the electrical quantity of the distribution network line; S212, calculating the power frequency electric field distribution characteristics of the distribution network line according to the steady-state value of the electrical quantity, comparing and analyzing the power frequency electric field distribution characteristics with the standard power frequency electric field characteristics, and obtaining the first steady-state analysis result; S213, establishing a first transient model of the power frequency electric field based on the operating conditions and historical transient information of the distribution network line, taking the electrical parameters as input of the first steady-state model, solving the first transient model, and obtaining a transient response of the electrical quantity of the distribution network line; S214. Analyze the transient condition of the distribution network line through the transient response of the electrical quantity to obtain the first transient analysis result.

7. A distribution network line fault early warning and inspection method according to claim 4, characterized in that: The S22 comprises the following sub-steps: S221. Establishing a second steady-state model of the power frequency magnetic field based on the power frequency current information in the distribution network line, solving the second steady-state model, and obtaining a steady-state distribution of the power frequency magnetic field in the distribution network line; S222, comparing and analyzing the steady-state distribution of the power frequency magnetic field with the standard power frequency magnetic field distribution characteristics to obtain the second steady-state analysis result; S223, establishing a second transient model of the power frequency magnetic field based on the operating conditions and historical transient information of the distribution network line, taking the electrical parameters as input of the second transient model for calculation, and obtaining transient response data of the power frequency magnetic field during the transient process of the distribution network line; S224. Analyze the transient condition of the distribution network line through the transient response data of the power frequency magnetic field to obtain the second transient analysis result.

8. A distribution network line fault early warning and inspection method according to claim 5 or 6, characterized in that: The S3 comprises the following sub-steps: S31, judging whether a distribution network line fails based on the first steady-state analysis result and the second steady-state analysis result, if one and only one of the first steady-state analysis result and the second steady-state analysis result is abnormal, executing S4; if both the first steady-state analysis result and the second steady-state analysis result are abnormal, executing S5; S32. Determine whether a distribution network line fault occurs based on the first transient analysis result and the second transient analysis result. If one and only one of the first transient analysis result and the second transient analysis result is abnormal, execute S4; if both the first transient analysis result and the second transient analysis result are abnormal, execute S5.

9. A distribution network line fault early warning and inspection method according to claim 1, characterized in that: The S4 comprises the following sub-steps: The fault warning is initiated according to the abnormal analysis results of the power frequency electric field and the power frequency magnetic field, and the high-frequency traveling wave state of the distribution network line is monitored, and the fault state of the distribution network line is secondary analyzed. If a high-frequency traveling wave is generated, S5 is executed; if no high-frequency traveling wave is generated, S1 is executed within the standard abnormal disturbance time range.

10. A distribution network line fault early warning and inspection method according to claim 1, characterized in that: The S5 comprises the following sub-steps: S51, collecting high-frequency traveling wave signals of the target distribution network line through an industrial frequency sensor; S52. Calculate the traveling wave time difference between the high-frequency traveling wave signal and the two ends of the target distribution network line based on the two-terminal traveling wave ranging method, and locate the fault point in the target distribution network line.

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