Distribution network cable traveling wave fault early warning and positioning method and distribution network cable traveling wave fault early warning and positioning system

Abstract

The invention discloses a distribution network cable traveling wave fault early warning and positioning method and system, and the method comprises the steps: installing a device in a ring main unit, collecting a high-frequency traveling wave current and a power frequency current, and recognizing a grounding fault through a transient zero sequence comparison method and a high-frequency traveling wave polarity algorithm; weak traveling wave signals generated by insulation defects are monitored to carry out hidden danger early warning; traveling wave arrival time difference is measured through double-end distance measurement, and the position of a fault point is calculated in combination with line parameters; and early warning and positioning results are transmitted to a master station through 4G / 5G and 101 / 104 protocols. The system comprises a data acquisition module, a signal processing module, a fault positioning module, a hidden danger early warning module, a master station communication module and a master station module which work cooperatively. The method and the system are high in positioning precision, can realize accurate fault positioning and hidden danger early warning, support live-line installation, are suitable for various scenes, effectively solve the operation and maintenance problem of the distribution network cable, and improve the power supply reliability.

Description

Technical Field

[0001] The present invention relates to the field of cable fault location, and particularly to a traveling wave fault early warning and location method and system for distribution network cables. Background Art

[0002] In modern urban distribution networks, cables, as key carriers of power transmission, their stable operation is crucial for ensuring power supply reliability. With the rapid development of cities, the scale of the distribution network is constantly expanding, and the cable lines are becoming increasingly complex, which poses great challenges to the monitoring and handling of cable faults. On the one hand, urban cable ring main units are dense and there are many users. Once a fault occurs in a certain branch line, it is very difficult to quickly and accurately determine the fault location. On the other hand, distribution network cables are mostly laid by direct burial underground or in cable trenches, and the operating environment is harsh. It is extremely difficult to find faults after they occur. Offline detection not only takes time but also requires power outage to disassemble cable joints, with cumbersome operations and unable to detect faults in a timely manner.

[0003] Currently, there are many deficiencies in the technologies for distribution network cable fault location and early warning on the market. Traditional fault indicators face technical and reliability problems. Based on power frequency interval location technology, they can only achieve fault interval location. For long lines, complex lines, and lines with many hidden faults and frequent power outages and frequency jumps, the use effect is not good and cannot meet the actual needs. Although the primary-secondary integrated switch can solve some problems of low-resistance grounding fault location and isolation, the location interval is large, and there are still limitations in dealing with complex line faults. The old-style DTUs and fault indicators have defects in the fault diagnosis principle. They only judge single-phase grounding faults based on power frequency and transient zero-sequence signals, with insufficient reliability, and neither of them has a defect early warning function.

[0004] In addition, the existing technologies are also inconvenient in terms of installation methods. Most of them require power outage for installation, which not only affects the continuity of power supply but also increases the operation and maintenance costs and time costs. In the face of the increasing power demand and the continuous improvement of the requirements for power supply reliability, the disadvantages of these existing technologies are becoming more and more prominent. There is an urgent need for a more advanced and efficient traveling wave fault early warning and location method and system for distribution network cables to solve the problems in the operation and maintenance of distribution network cables, improve the safety and stability of the distribution network, and meet the power supply requirements of modern urban development. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies of the existing technology, the present invention provides a traveling wave fault early warning and location method and system for distribution network cables.

[0006] The technical solution adopted by the present invention is a traveling wave fault early warning and location method for distribution network cables, which includes: Step 1: Install a cable traveling wave fault precise positioning device in the ring main unit of the urban power grid cable line. Install Terminal 1 in the cable compartment, Terminal 2 in the DTU cabinet, and the acquisition unit in the DTU cabinet. One acquisition unit collects the high-frequency traveling wave current and power frequency current of multiple loop cables. Step 2: Collect the high-frequency traveling wave current and power frequency current during the operation of the cable line. Analyze the collected current data by combining the transient zero-sequence comparison method with the high-frequency traveling wave polarity algorithm to identify the grounded cable fault. Step 3: Monitor the periodic weak traveling wave signal generated before the flashover of the insulation defect of the cable equipment, extract the discharge characteristic quantities, use the discharge times and discharge amount as comparison parameters, compare the discharge historical data, and use trend analysis to determine the hidden danger area. Step 4: When a cable line fails, the traveling wave propagates along the wire to both ends. Use the double-end ranging method to collect the steady-state, transient information and traveling wave current of the line fault, and measure the time difference when the initial current traveling wave reaches the monitoring terminal. Step 5: According to the measured time difference and combined with the relevant parameters of the cable line, calculate the position of the fault point in the cable line. Step 6: Transmit the fault warning information and fault location result to the master station through the 4G / 5G communication method according to the 101 / 104 protocol. The master station processes and displays the information, and the operation and maintenance personnel can obtain it in time and take safety response measures.

[0007] Furthermore, in Step 2, the transient zero-sequence current algorithm is adopted , where are the three-phase currents respectively, calculate the transient zero-sequence current, set the range of the traveling wave current sensor to 50 mA - 500 A. When the transient zero-sequence current exceeds the set threshold and the traveling wave polarity meets specific conditions, it is determined as a grounding fault. At the same time, use the spectrum analysis algorithm of the high-frequency traveling wave current , where is the function of the high-frequency traveling wave current with respect to time, is the frequency, analyze the spectrum of the high-frequency traveling wave current. When the energy in a specific frequency band exceeds the set value, further confirm the grounding fault.

[0008] Furthermore, in Step 3, for the extraction of the discharge characteristic quantities, the wavelet transform algorithm is adopted , where is the monitored traveling wave signal, is the wavelet function, is the scale factor, is the translation factor, decompose the traveling wave signal into different frequency bands, obtain the discharge energy distribution characteristics of different frequency bands, set the discharge times threshold to 5 times per minute, and the discharge amount threshold For , when the number of discharges or the discharge amount exceeds the threshold, the hidden danger level is judged by combining trend analysis. If within three consecutive monitoring cycles, the number of discharges shows an upward trend and exceeds the threshold, or the discharge amount exceeds the threshold and continues to increase in subsequent cycles, it is determined as a level-II hidden danger. Furthermore, in step four, during double-end ranging, assume the propagation speed of the current traveling wave in the cable line is , and use the time difference measurement formula to calculate the time difference, where , are the times when the traveling wave reaches the monitoring terminals at both ends respectively. When the line length is 1 km, if the measured time difference is within - , then start the subsequent fault point calculation process to ensure that the time difference measurement accuracy is within .

[0009] Furthermore, in step five, when calculating the fault point location, if the cable line length is known, according to the fault point distance calculation formula , where is the traveling wave propagation speed, is the time difference, calculate the distance from the fault point to one end monitoring point. When , substitute into the formula to calculate , so as to determine the specific location of the fault point in the cable line, and the positioning accuracy requirement reaches .

[0010] Furthermore, in step six, the communication process adopts communication mode, and the signal strength needs to meet , , use an encryption algorithm to encrypt the transmitted data, and the encryption key length is 128 bits, which is used to prevent the data from being stolen or tampered with during the transmission process. After the master station receives the data, it is parsed according to the 101 / 104 protocol, and the check code of the data is verified during the parsing process to ensure the accuracy of the data. If the verification fails, the data is required to be retransmitted.

[0011] Furthermore, in step one, when installing the device, the live installation method is adopted, the electric field strength of the installation environment , the magnetic field strength , during the installation process, use an infrared thermometer to monitor the temperature of different parts of the equipment, and the temperature threshold is set to , if the temperature exceeds the threshold, the installation is paused, the heat dissipation of the equipment is checked, and for different types of ring main units, according to their structural characteristics, an adapted installation bracket is used, and the load-bearing capacity of the installation bracket needs to meet more than 1.5 times the weight of the equipment.

[0012] Further, in step two, when analyzing the current data, for the transient zero-sequence current, a sliding window algorithm is used for data processing, the window size is set to 10 sampling points, and the sampling rate , by calculating the mean and variance of the transient zero-sequence current through the sliding window, when the mean exceeds the set threshold and the variance exceeds a certain range, it is determined as a suspected grounding fault. For the polarity analysis of the high-frequency traveling wave, the polarity judgment threshold is set to 0.5V. When the high-frequency traveling wave voltage exceeds this threshold and the polarity conforms to the characteristics of the grounding fault, the grounding fault is further confirmed. At the same time, combined with the historical fault data of the cable line, a fault model is established using a machine learning algorithm to classify and predict the currently collected data.

[0013] Further, in step three, the trend analysis uses the time series analysis method to model the historical data of the discharge times and discharge amounts, including the ARIMA model, including this model variables, where p is the autoregressive order, set to 2, is the differencing order, set to 1, is the moving average order, set to 1. By using the model to predict the change trends of the discharge times and discharge amounts in the future for a period of time, if the predicted value exceeds the early warning threshold, an early warning of potential hazards is issued in advance. At the same time, using the geographic information system data, the potential hazard area is marked on the map.

[0014] A distribution network cable traveling wave fault early warning and location system, which includes: Data acquisition module: This module collects the high-frequency traveling wave current and power frequency current of the cable line through the terminal one, terminal two and acquisition unit installed in the ring main unit of the urban network cable line, and the collected data is transmitted to the signal processing module in real time; Signal processing module: Receives the data transmitted by the data acquisition module, uses the transient zero-sequence comparison algorithm, high-frequency traveling wave polarity analysis algorithm and related algorithms for extracting discharge characteristic quantities to identify grounding faults, analyze discharge characteristics and calculate the time difference of arrival of traveling waves, and transmits the processed fault-related information to the fault location module and the potential hazard early warning module respectively; Fault location module: Receives the time difference of arrival of traveling waves transmitted by the signal processing module, combines the pre-stored cable line parameters, and uses the double-ended ranging algorithm to calculate the location of the fault point, and then sends the fault location result to the main station communication module; Hidden danger warning module: It receives the discharge characteristic quantity data analyzed by the signal processing module, uses an algorithm based on historical data comparison and trend analysis to judge the hidden danger area and generate warning information, and then sends the warning information to the master station communication module; Master station communication module: It receives the fault location result of the fault location module and the warning information of the hidden danger warning module, and transmits this information to the master station comprehensive processing module through 4G / 5G communication mode according to the 101 / 104 protocol. At the same time, it receives the feedback instruction of the master station comprehensive processing module to conduct two-way communication between the system and the master station; Master station comprehensive processing module: It receives the data transmitted by the master station communication module, uses data processing and display algorithms to process and visually display the fault warning information and fault location result for the operation and maintenance personnel to view and analyze. The master station comprehensive processing module also sends instructions to the master station communication module according to actual needs to remotely manage and control the entire distribution network cable traveling wave fault warning and location system.

[0015] Beneficial effects: The present invention proposes a method and system for warning and locating traveling wave faults in distribution network cables. In terms of fault warning, by monitoring the periodic weak traveling wave signals generated by insulation defects of cable equipment, extracting discharge characteristic quantities and combining historical data comparison and trend analysis, it can accurately determine the hidden danger area and issue early warnings, changing the inspection mode from passive to active and greatly reducing the tripping rate. In terms of fault location, a double-end ranging method is adopted to collect the steady-state, transient information and traveling wave current of line faults, measure the time difference of the traveling wave arriving at the monitoring terminal, and calculate the exact location of the fault point in combination with cable line parameters. The positioning accuracy is high, reaching the 10-meter level, greatly improving the rapid power restoration efficiency of urban cables. The application of this method and system effectively solves the problems in the operation and maintenance of urban distribution network cables. Its ground fault line selection function uses the transient zero-sequence comparison method combined with algorithms such as high-frequency traveling wave polarity to accurately identify ground cable faults with high line selection accuracy. Moreover, the system has strong installation adaptability, supports power outage and live working, and can also provide a power outage-free transformation plan for old ring main units, facilitating deployment in different scenarios. From the perspective of overall operation and maintenance, this method and system greatly improve work efficiency, reduce the time for fault finding and inspection, and reduce the consumption of human and material resources. At the same time, it reduces the safety risk of line inspection, especially at night or in bad weather. In addition, it can also contribute to lean operation and maintenance, reduce power outage time, generate good economic benefits and social responses, provide strong guarantee for the safe and stable operation of the distribution network, and promote the construction and development of modern intelligent distribution networks. Description of the drawings

[0016] Figure 1 It is the overall step flow chart of the present invention; Figure 2 It is the system module composition diagram of the present invention. Detailed implementation manners

[0017] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following further describes this application in detail with reference to the drawings and specific embodiments.

[0018] As Figure 1 shown, a traveling wave fault early warning and location method for distribution network cables, the method includes: Step 1: Install a cable traveling wave fault precise location device in the ring main unit of the urban network cable line, install Terminal 1 in the cable compartment, install Terminal 2 in the DTU cabinet, and install the acquisition unit in the DTU cabinet. One acquisition unit acquires the high-frequency traveling wave current and power frequency current of multiple loop cables; Specifically, installing a cable traveling wave fault precise location device in the ring main unit of the urban network cable line is the basis of the entire early warning and location method. Installing Terminal 1 in the cable compartment is because the cable compartment is a key node of the cable line and can directly and accurately obtain relevant electrical information of the cable. Terminal 2 is installed in the DTU cabinet, which is a centralized point for data transmission and control, facilitating the preliminary processing and transmission of the acquired data. The acquisition unit is also installed in the DTU cabinet, and one acquisition unit can acquire the high-frequency traveling wave current and power frequency current of multiple loop cables. For example, in a ring main unit of an urban network cable line with multiple branch loops, one acquisition unit can simultaneously acquire the current conditions of these branch loops, which not only improves the utilization efficiency of the equipment but also reduces the installation cost and space occupation. The high-frequency traveling wave current can reflect the rapidly changing current information generated by the cable line during a fault, while the power frequency current reflects the current state during normal operation of the cable. The combination of the two can provide comprehensive data support for subsequent fault analysis.

[0019] Step 2: Acquire the high-frequency traveling wave current and power frequency current during the operation of the cable line, analyze the acquired current data through algorithms such as the transient zero-sequence comparison method combined with the polarity of high-frequency traveling waves, and identify the grounded cable fault; Specifically, after collecting the high-frequency traveling wave current and power frequency current during the operation of the cable line, it is necessary to deeply analyze these data to identify the grounded cable fault. The transient zero-sequence comparison method determines whether a grounding fault has occurred by comparing the characteristics such as the magnitude and direction of the transient zero-sequence current generated by the three-phase current at the moment of the fault. When a grounding fault occurs in the cable, the balance of the three-phase current is broken, resulting in a transient zero-sequence current. The high-frequency traveling wave polarity algorithm assists in judging the fault situation based on the polarity change of the high-frequency traveling wave when it propagates between the fault point and the monitoring point. For example, when a grounding fault occurs in a certain phase of the cable, the polarity of the high-frequency traveling wave of that phase will change significantly. By combining these two algorithms, the accuracy of identifying the grounded cable fault can be greatly improved. In practical applications, if the collected current data shows that the transient zero-sequence current exceeds the preset threshold and the polarity of the high-frequency traveling wave changes in line with the fault characteristics, it can be determined that a grounding fault has occurred in the cable line.

[0020] Step 3: Monitor the periodic weak traveling wave signals generated by the insulation defects of the cable equipment before flashover, extract the discharge characteristic quantities, use the number of discharges and the discharge amount as comparison parameters, compare the historical discharge data, and use trend analysis to determine the potential hazard area; Specifically, the insulation defects of the cable equipment will generate periodic weak traveling wave signals before flashover, and these signals contain important information about the severity and development trend of the insulation defects. By extracting the discharge characteristic quantities, such as the amplitude and frequency of the discharge, the insulation state of the cable can be quantitatively evaluated. Using the number of discharges and the discharge amount as comparison parameters and comparing them with the historical data can reveal the development and change of the insulation defects. For example, if the number of discharges of a certain section of the cable increases significantly in a short period of time, or the discharge amount continues to increase, it indicates that the insulation defect of the cable is intensifying and there is a potential safety hazard. Trend analysis predicts the future insulation state based on the change trend of the historical data. By analyzing a large amount of historical discharge data and establishing a trend model, the time and location where the cable may fail can be predicted in advance, thereby determining the potential hazard area. In this way, the operation and maintenance personnel can check and maintain the potential hazard area targeted to avoid the occurrence of faults.

[0021] Step 4: When a fault occurs in the cable line, the traveling wave propagates along the wire to both ends. Using the double-end ranging method, collect the steady-state, transient information and traveling wave current of the line fault, and measure the time difference for the initial current traveling wave to reach the monitoring terminal; Specifically, when a cable line fails, traveling waves will propagate along the conductors towards both ends. The double - end ranging method utilizes monitoring terminals installed at both ends of the cable line to record the arrival times of the initial current traveling waves respectively. By measuring the difference between these two times, it can provide key information for subsequent calculation of the fault location. When collecting the steady - state, transient information and traveling - wave current of the line fault, the steady - state information reflects the stable operating state of the cable line for a period of time after the fault occurs, while the transient information reflects the rapid changes at the moment of the fault. The accurate acquisition of the traveling - wave current is crucial for the measurement of the time difference. For example, in a long cable line, when a fault occurs, the traveling waves propagate from the fault point towards both ends, and the monitoring terminals at both ends will record the arrival times of the traveling waves respectively. By accurately measuring the difference between these two times, accurate data can be provided for the next step of calculating the fault location.

[0022] Step Five: Based on the measured time difference and combined with the relevant parameters of the cable line, calculate the position of the fault point in the cable line; Specifically, based on the measured time difference and combined with the relevant parameters of the cable line, such as the length of the cable, the propagation speed of the traveling wave in the cable, etc., the position of the fault point in the cable line can be calculated. The length of the cable line is a known parameter, and the propagation speed of the traveling wave in the cable is usually a relatively stable value, which can be obtained through experiments or theoretical calculations. For example, assume that the length of the cable line is 10 kilometers, the propagation speed of the traveling wave in this cable is 200,000 kilometers per second, and the measured time difference is 0.00005 seconds. According to the relevant calculation method, the distance of the fault point from one of the monitoring terminals can be calculated. In this way, the operation and maintenance personnel can quickly and accurately locate the fault point for repair and handling.

[0023] Step Six: Transmit the fault warning information and the fault location result to the master station via 4G / 5G communication according to the 101 / 104 protocol. The master station processes and displays the information, and the operation and maintenance personnel can obtain it in a timely manner and take safety response measures.

[0024] Specifically, transmitting the fault warning information and the fault location result to the master station via 4G / 5G communication mode according to the 101 / 104 protocol is the last step of the entire warning and location method and also a key link to achieve timely fault handling. The 4G / 5G communication mode features high speed and stability, ensuring the rapid and accurate transmission of data. The 101 / 104 protocol is a commonly used communication protocol in the power system, which stipulates the data transmission format and communication rules, ensuring that the master station can correctly receive and process the data transmitted from the monitoring terminal. After receiving the fault warning information and the fault location result, the master station will process and display this information. For example, it will mark the fault point on the map and display the type and severity of the fault, etc. The operation and maintenance personnel can obtain this information in a timely manner through the interface of the master station and take corresponding safety response measures according to the actual situation, such as arranging maintenance personnel to go to the fault point for repair, or taking temporary power outage measures to avoid the expansion of the fault, etc.

[0025] Preferably, in step two, the transient zero-sequence current algorithm is adopted , where are the three-phase currents respectively, calculate the transient zero-sequence current, set the range of the traveling wave current sensor to 50 mA - 500 A, and when the transient zero-sequence current exceeds the set threshold and the traveling wave polarity meets specific conditions, it is determined as a ground fault. At the same time, use the spectrum analysis algorithm of the high-frequency traveling wave current , where is the function of the high-frequency traveling wave current with respect to time, is the frequency, analyze the spectrum of the high-frequency traveling wave current, and when the energy in a specific frequency band exceeds the set value, further confirm the ground fault.

[0026] Preferably, in step three, for the extraction of the discharge characteristic quantity, the wavelet transform algorithm is adopted , where is the monitored traveling wave signal, is the wavelet function, is the scale factor, is the translation factor, decompose the traveling wave signal into different frequency bands, and obtain the discharge energy distribution characteristics in different frequency bands. Set the discharge times threshold to 5 times per minute, and the discharge quantity threshold is . When the discharge times or the discharge quantity exceeds the threshold, combine trend analysis to judge the hidden danger level. If within three consecutive monitoring periods, the discharge times show an upward trend and exceed the threshold, or the discharge quantity exceeds the threshold and continues to increase in subsequent periods, it is determined as a level-II hidden danger.

[0027] Preferably, in step four, during double-ended ranging, assume that the current traveling wave propagation speed in the cable line is , using the time difference measurement formula calculate the time difference, where , are the times when the traveling wave arrives at the monitoring terminals at both ends respectively. When the line length is 1 km, if the measured time difference is within - , then start the subsequent fault point calculation process to ensure that the time difference measurement accuracy is within .

[0028] Preferably, in step five, when calculating the fault point position, if the cable line length is known, according to the fault point distance calculation formula , where is the traveling wave propagation speed, is the time difference, calculate the distance from the fault point to one end monitoring point. When , substitute it into the formula to calculate , so as to determine the specific position of the fault point in the cable line, and the positioning accuracy requirement reaches .

[0029] Preferably, in step six, the communication process adopts communication mode, and the signal strength needs to meet , , to ensure the stability of data transmission. Use an encryption algorithm to encrypt the transmitted data, and the encryption key length is 128 bits to prevent the data from being stolen or tampered with during transmission. After the master station receives the data, it parses it according to the 101 / 104 protocol, and strictly checks the check code of the data during the parsing process to ensure the accuracy of the data. If the check fails, the data is required to be retransmitted.

[0030] Preferably, when installing the device in step one, if the live installation method is adopted, it is necessary to ensure that the electric field strength of the installation environment, and the magnetic field strength , to avoid harm to the operators. During the installation process, use an infrared thermometer to monitor the temperature of different parts of the equipment, and the temperature threshold is set to . If the temperature exceeds the threshold, the installation is suspended and the heat dissipation of the equipment is checked. For different types of ring main units, according to their structural characteristics, adopt an adapted installation bracket, and the load-bearing capacity of the installation bracket needs to meet more than 1.5 times the weight of the equipment to ensure the firm installation of the equipment.

[0031] Preferably, when analyzing the current data in step two, for the transient zero-sequence current, use the sliding window algorithm to process the data, and the window size is set to 10 sampling points, and the sampling rate By calculating the mean and variance of the transient zero-sequence current through a sliding window, when the mean exceeds the set threshold and the variance exceeds a certain range, it is determined as a suspected grounding fault. For the polarity analysis of high-frequency traveling waves, the polarity judgment threshold is set to 0.5V. When the high-frequency traveling wave voltage exceeds this threshold and the polarity conforms to the characteristics of a grounding fault, the grounding fault is further confirmed. At the same time, combined with the historical fault data of the cable line, a fault model is established using machine learning algorithms to classify and predict the currently collected data, improving the accuracy of grounding fault identification.

[0032] Preferably, in step three, trend analysis uses time series analysis methods to model the historical data of the discharge times and discharge amounts, including the ARIMA model, including this model variables, where p is the autoregressive order, set to 2, is the differencing order, set to 1, is the moving average order, set to 1. Through the model, predict the change trends of the discharge times and discharge amounts in the future for a period of time. If the predicted value exceeds the early warning threshold, an early warning of potential hazards is issued in advance. At the same time, using Geographic Information System (GIS) data, mark the potential hazard areas on the map to facilitate the quick positioning and troubleshooting of potential hazards by maintenance personnel.

[0033] As Figure 2 shown, a traveling wave fault early warning and location system for distribution network cables includes: Data acquisition module: This module collects the high-frequency traveling wave current and power frequency current of the cable line through terminal one, terminal two, and the acquisition unit installed in the ring main unit of the urban network cable line. The collected data is transmitted to the signal processing module in real time to provide basic data for subsequent analysis.

[0034] Signal processing module: Receive the data transmitted by the data acquisition module, and use the transient zero-sequence comparison algorithm, high-frequency traveling wave polarity analysis algorithm, and related algorithms for extracting discharge characteristic quantities to identify grounding faults, analyze discharge characteristics, and calculate the time difference of arrival of traveling waves. Transmit the processed fault-related information to the fault location module and the potential hazard early warning module respectively.

[0035] Fault location module: Receive information such as the time difference of arrival of traveling waves transmitted by the signal processing module, combine the pre-stored cable line parameters, and use the two-terminal ranging algorithm to calculate the location of the fault point, and then send the fault location result to the main station communication module.

[0036] Potential hazard early warning module: Receive the discharge characteristic quantity data analyzed by the signal processing module, use the algorithm based on historical data comparison and trend analysis to judge the potential hazard area and generate early warning information, and then send the early warning information to the main station communication module.

[0037] Master station communication module: Receives the fault location results of the fault location module and the early warning information of the potential hazard warning module, and transmits this information to the master station comprehensive processing module via 4G / 5G communication mode according to the 101 / 104 protocol. At the same time, it receives the feedback instructions from the master station comprehensive processing module to conduct two-way communication between the system and the master station.

[0038] Master station comprehensive processing module: Receives the data transmitted by the master station communication module, and uses data processing and display algorithms to process and visually display the fault warning information and fault location results for the operation and maintenance personnel to view and analyze. The master station comprehensive processing module also sends instructions to the master station communication module according to actual needs to achieve remote management and control of the entire distribution network cable traveling wave fault warning and location system.

[0039] This method and system perform excellently in fault warning and potential hazard investigation. In the existing technology, fault indicators and traditional monitoring devices cannot effectively warn of cable insulation defects and are difficult to detect early potential hazards. However, this system can accurately determine the potential hazard area and actively give early warnings by monitoring the periodic weak traveling wave signals generated before the flashover of cable equipment insulation defects, extracting discharge characteristic quantities, and combining historical data comparison and trend analysis. It changes passive inspection to active investigation and treatment, greatly reducing the tripping rate, effectively preventing faults from occurring, and ensuring the stability of power supply.

[0040] In terms of the accuracy and efficiency of fault location, this system has obvious advantages. In the past, the positioning range of the integrated primary and secondary switches was large, and the fault diagnosis reliability of the old-fashioned DTU and fault indicators was insufficient, and neither could achieve high-precision positioning. This system adopts the double-end ranging method, collects the steady-state, transient information and traveling wave current of the line fault, measures the time difference of the traveling wave reaching the monitoring terminal to calculate the fault point location, with a positioning accuracy of up to the 10-meter level and a positioning error within 10 meters, greatly improving the fault investigation speed, reducing the power outage time, and enhancing the power supply efficiency and economic benefits.

[0041] In terms of installation and applicable scenarios, this system also overcomes the limitations of the existing technology. Most traditional devices need to be installed during a power outage, which is inconvenient to operate and affects the continuity of power supply. This system supports live installation and can provide effective solutions for various ring main units, including old-fashioned ring main units lacking phase B, with strong installation adaptability. It can also be installed distributively and the background conducts centralized research and judgment, suitable for various scenarios such as substations, distribution rooms, and outdoor ring main units. One device can monitor up to 6 cable circuits at most, with high cost performance. Whether it is a complex urban distribution network or an area with long lines and high failure rates, it can play a good role, effectively solving the problems in the operation and maintenance of distribution network cables and promoting the intelligent and efficient development of the distribution network.

[0042] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "arranged", "installed", "connected", "joined", "fixed" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0043] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various equivalent changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalent scope.

Claims

1. A traveling wave fault warning and positioning method for distribution network cables, characterized in that, The method includes: Step 1: Install a cable traveling wave fault precise positioning device in the ring main unit of the urban power grid cable line. Install Terminal 1 in the cable compartment, Terminal 2 in the DTU cabinet, and the acquisition unit in the DTU cabinet. One acquisition unit acquires the high-frequency traveling wave current and power frequency current of multiple circuit cables. Step 2: Acquire the high-frequency traveling wave current and power frequency current during the operation of the cable line. Analyze the acquired current data by combining the transient zero-sequence comparison method with the high-frequency traveling wave polarity algorithm to identify the grounded cable fault. Step 3: Monitor the periodic weak traveling wave signal generated before the flashover of the insulation defect of the cable equipment, extract the discharge characteristic quantity, use the number of discharges and the discharge quantity as comparison parameters, compare the discharge historical data, and use trend analysis to determine the potential hazard area. Step 4: When a fault occurs in the cable line, the traveling wave transmits along the wire to both ends. Use the double-end ranging method to acquire the steady-state, transient information and traveling wave current of the line fault, and measure the time difference when the initial current traveling wave arrives at the monitoring terminal. Step 5: According to the measured time difference and combined with the relevant parameters of the cable line, calculate the position of the fault point in the cable line. Step 6: Transmit the fault warning information and the fault location result to the master station through the 4G / 5G communication method according to the 101 / 104 protocol. The master station processes and displays the information, and the operation and maintenance personnel can obtain it in time and take safety response measures.

2. The traveling wave fault warning and location method for a distribution network cable according to claim 1, characterized in that: In the second step, the transient zero-sequence current algorithm is adopted. , where are the three-phase currents respectively, calculate the transient zero-sequence current, set the range of the traveling wave current sensor to 50 mA - 500 A, when the transient zero-sequence current exceeds the set threshold and the traveling wave polarity meets specific conditions, it is determined as a grounding fault. At the same time, use the spectrum analysis algorithm of the high-frequency traveling wave current , where is the function of the high-frequency traveling wave current with respect to time, is the frequency, analyze the spectrum of the high-frequency traveling wave current, when the energy in a specific frequency band exceeds the set value, further confirm the grounding fault.

3. A traveling wave fault early warning and location method for a distribution network cable according to claim 1, characterized in that: In Step 3, for the extraction of the discharge characteristic quantity, the wavelet transform algorithm is adopted , where is the monitored traveling wave signal, is the wavelet function, is the scale factor, is the translation factor. The traveling wave signal is decomposed into different frequency bands to obtain the discharge energy distribution characteristics in different frequency bands, and the discharge times threshold is set is 5 times minutes, and the discharge quantity threshold is . When the discharge times or the discharge quantity exceeds the threshold, the hidden danger level is judged by combining trend analysis. If within three consecutive monitoring periods, the discharge times show an upward trend and exceed the threshold, or the discharge quantity exceeds the threshold and continues to increase in subsequent periods, it is determined as a Class II hidden danger.

4. A traveling wave fault early warning and location method for distribution network cables according to claim 1, characterized in that: In Step 4, during double - end ranging, assuming the propagation speed of current traveling waves in the cable line is , the time difference is calculated using the time - difference measurement formula . Among them, , are the times when the traveling waves reach the monitoring terminals at both ends respectively. When the line length is 1 km, if the measured time difference is within - , then the subsequent fault - point calculation process is started to ensure that the time - difference measurement accuracy is within .

5. A traveling wave fault early warning and positioning method for a distribution network cable according to claim 1, characterized in that: In the fifth step, when calculating the fault point location, if the cable line length is known , according to the fault point distance calculation formula , where is the traveling wave propagation speed is the time difference, calculate the distance of the fault point from one end monitoring point , when , substitute into the formula to calculate and obtain , so as to determine the specific position of the fault point in the cable line, and the positioning accuracy requirement reaches .

6. The traveling wave fault early warning and location method for distribution network cables according to claim 1, characterized in that: In Step 6, the communication process uses communication mode, and the signal strength needs to meet , . The transmission data is encrypted using an encryption algorithm. The encryption key length is 128 bits, which is used to prevent the data from being stolen or tampered with during transmission. After receiving the data, the master station parses it according to the 101 / 104 protocol. During the parsing process, the checksum of the data is verified to ensure the accuracy of the data. If the verification fails, the data is required to be retransmitted.

7. A traveling wave fault warning and positioning method for distribution network cables according to claim 1, characterized in that: In the first step, when installing the device, the live installation method is adopted, and the electric field strength of the installation environment , the magnetic field strength . During the installation process, an infrared thermometer is used to monitor the temperature of different parts of the equipment, and the temperature threshold is set to . If the temperature exceeds the threshold, the installation is suspended, the heat dissipation of the equipment is checked, and for different types of ring main units, according to their structural characteristics, adapted installation brackets are used, and the load-bearing capacity of the installation brackets needs to meet more than 1.5 times the weight of the equipment.

8. A traveling wave fault warning and positioning method for a distribution network cable according to claim 1, characterized in that: In the second step, when analyzing the current data, for the transient zero-sequence current, a sliding window algorithm is used for data processing. The window size is set to 10 sampling points, and the sampling rate , the mean and variance of the transient zero-sequence current are calculated through the sliding window. When the mean exceeds the set threshold and the variance exceeds a certain range, it is determined as a suspected grounding fault. For the polarity analysis of the high-frequency traveling wave, the polarity judgment threshold is set to 0.5V. When the high-frequency traveling wave voltage exceeds this threshold and the polarity conforms to the characteristics of the grounding fault, the grounding fault is further confirmed. At the same time, combined with the historical fault data of the cable line, a fault model is established using a machine learning algorithm to classify and predict the currently collected data.

9. A traveling wave fault warning and positioning method for a distribution network cable according to claim 1, characterized in that: In Step 3, time series analysis method is adopted for trend analysis to model the historical data of the number of discharges and the discharge amount, including the ARIMA model, including this model variables, where p is the autoregressive order, set to 2, is the differencing order, set to 1, is the moving average order, set to 1. The change trends of the number of discharges and the discharge amount in the future period are predicted through the model. If the predicted value exceeds the warning threshold, a potential hazard warning is issued in advance. At the same time, using the geographic information system data, the potential hazard area is marked on the map.

10. A traveling wave fault warning and positioning system for distribution network cables, characterized in that, The system includes: Data acquisition module: This module acquires the high-frequency traveling wave current and power frequency current of the cable line through Terminal 1, Terminal 2 and the acquisition unit installed in the ring main unit of the urban power grid cable line, and the acquired data is transmitted to the signal processing module in real time. Signal processing module: Receive the data transmitted by the data acquisition module, and use the transient zero-sequence comparison algorithm, the high-frequency traveling wave polarity analysis algorithm and the relevant algorithms for extracting the discharge characteristic quantity to identify the grounding fault, analyze the discharge characteristics and calculate the time difference when the traveling wave arrives, and transmit the processed fault-related information to the fault location module and the potential hazard warning module respectively. Fault location module: Receive the time difference information when the traveling wave arrives transmitted by the signal processing module, combine the pre-stored cable line parameters, use the double-end ranging algorithm to calculate the position of the fault point, and then send the fault location result to the master station communication module. Potential hazard warning module: Receive the discharge characteristic quantity data analyzed by the signal processing module, use the algorithm based on historical data comparison and trend analysis to judge the potential hazard area and generate warning information, and then send the warning information to the master station communication module. Master station communication module: Receive the fault location result of the fault location module and the warning information of the potential hazard warning module, and transmit these information to the master station integrated processing module through the 4G / 5G communication method according to the 101 / 104 protocol. At the same time, receive the feedback instruction of the master station integrated processing module to conduct two-way communication between the system and the master station. Master station integrated processing module: Receives the data transmitted by the master station communication module, processes and visually displays the fault warning information and fault location results using data processing and display algorithms for operation and maintenance personnel to view and analyze. The master station integrated processing module also sends instructions to the master station communication module according to actual needs to remotely manage and control the entire distribution network cable traveling wave fault warning and location system.

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