Power transmission cable fault sensing and diagnosing method and system based on trace gas analysis

Abstract

The invention relates to the technical field of power transmission cables, in particular to a power transmission cable fault sensing and diagnosing method and system based on trace gas analysis, and the system comprises a power supply module, a gas sensing module, a data acquisition module, a gas circuit module, a pump driving module and a communication module. The gas sensing device can monitor trace gas released due to cable insulation defects and high temperature in the high-voltage power transmission cable well, whether prompting and alarming are needed or not is judged through an automatic concentration calibration algorithm in the device, and monitoring data and results are uploaded to the intelligent state online monitoring platform through the wireless ad hoc network access device. Operation and maintenance personnel can remotely monitor the current operation state of the cable, determine whether field maintenance is needed or not, and make a field maintenance plan.

Description

Technical Field

[0001] The present invention relates to the technical field of power transmission cables, and more specifically, to a method and system for fault perception and diagnosis of power transmission cables based on trace gas analysis. Background Art

[0002] Cross-linked polyethylene (XLPE) insulated cables play an important role in the power system for power transmission. As the most basic power facilities, power cables are commonly used for power introduction and lead-out lines in power plants, substations, and industrial and mining enterprises. Research shows that after XLPE cables are put into operation, their main insulation layers will undergo irreversible insulation aging and generate insulation defects under the action of multiple factors such as electricity, heat, mechanics, and environment, which are extremely likely to induce cable faults and threaten the safe and stable operation of the power grid.

[0003] With the continuous increase in the cable rate, the situation of dense laying of power cables of various voltage levels is increasing. Current detection methods for the main insulation of cables include partial discharge detection technology, infrared detection technology, etc. Among them, the cable partial discharge detection technology mainly focuses on live detection or online monitoring based on high-frequency current sensors. However, the current applications mainly have the following problems: 1) The traditional live detection mainly based on manual work has low efficiency. Moreover, since cables are usually laid in cable trenches with harsh operating environments, it poses potential hazards to the health and safety of inspection operators, and there are also problems such as low detection efficiency and unsatisfactory detection effects; 2) The online monitoring system mainly based on partial discharge sensors needs to be installed for each cable intermediate joint laid over a long distance. The deployment of the complete set of systems is expensive and the maintenance cost is high; 3) When partial discharge occurs due to insulation defects in the cable, signal detection methods such as electromagnetic waves, high-frequency current pulses, and sound waves are easily affected by environmental interference, which affects the detection accuracy; 4) Currently, the visualization application of massive calculation data in online monitoring is not mature, and the functions of the visualization platform are not perfect enough.

[0004] Therefore, for the cable insulation layer and protective layer, when they are at high temperatures and insulation fails, physical phenomena such as thermal degradation, thermal decomposition, electrical degradation, and electrical decomposition will occur. According to the high-temperature physical phenomenon that occurs when partial discharge occurs in high-voltage transmission cables, the main insulation will decompose to generate volatile organic compounds, and these organic compounds can also be used as cable fault characteristics to identify and predict potential early faults in operating cables. Thus, it is possible to pre-control and eliminate defects before serious faults such as cable insulation aging, partial discharge, overheating leading to fire, short circuit / open circuit occur, and eliminate potential cable operation faults at the budding stage. There is a need for a method and system for fault perception and diagnosis of power transmission cables based on trace gas analysis to solve this problem. Summary of the Invention

[0005] The purpose of the present invention is to provide a power transmission cable fault perception and diagnosis method and system based on trace gas analysis to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: A power transmission cable fault perception and diagnosis system based on trace gas analysis, including a power supply module, a gas sensing module, a data acquisition module, a gas path module, a pump drive module, and a communication module; The cable trace gas sensing system is composed of a power supply module, a gas sensing module, a data acquisition module, a gas path module, a pump drive module, and a communication module.

[0007] As a preferred technical solution of the present invention, the gas sensing system in the power supply module can be designed as a low-power circuit, powered by a high-performance 3.6V lithium thionyl chloride battery, with data acquisition once a day, and the power supply duration can reach 6 years, and no power wiring is required for installation.

[0008] As a preferred technical solution of the present invention, the gas sensing module can select a high-sensitivity gas sensing probe according to the qualitative and quantitative grouping test results of the cable trace gas, and convert the gas content into a weak current signal through A / D.

[0009] As a preferred technical solution of the present invention, the data acquisition module processes the current signal collected by the gas sensing probe and finally converts it into a voltage signal. The acquisition module is designed with a bandwidth of 1MHz, a sampling frequency of 2MHz, a storage depth of 10kB, and a resolution of 16 bits.

[0010] As a preferred technical solution of the present invention, the gas path module is designed at the front end of the gas sensing device, and a detection circuit is used to amplify the weak signal output by the sensing circuit to improve the detection sensitivity of the trace gas sensing module.

[0011] As a preferred technical solution of the present invention, the pump drive module is designed with a micro pump drive module to pump air from the gas path to increase the air intake. The traditional position sensor of the micro pump is removed, and a state observer is used to estimate the speed of the permanent magnet brushless micro pump to achieve speed closed-loop control.

[0012] As a preferred technical solution of the present invention, the communication module uses a wireless LoRa communication method based on the Internet of Things self-organizing network protocol to forward data to the access device.

[0013] A power transmission cable fault perception and diagnosis method and system based on trace gas analysis, characterized in that the following steps: S1. First, observe the operating status of the power system, pay attention to whether there are phenomena such as unstable voltage, power outage, or abnormal sounds, and record in detail the location, time, and possible causes of the fault. Disconnect the power supply under the premise of ensuring safety, and conduct a detailed inspection of the appearance of the cable to check for obvious bumps, scorching, cracks, or other problems. S2. For the characteristic gas components and contents of cable materials at different temperatures, study the automatic calibration algorithm for gas concentration, calibrate the alarm threshold of the system, improve the detection accuracy of the system, and reduce the false alarm rate. S3. The algorithm includes: The first type: the automatic spectral peak recognition algorithm Since the on-site operation of the cable insulation aging and overheating fault sensing device based on trace gases has no manual assistance, it must have the function of automatic spectral peak recognition. Considering that the peak waveforms of each gas component are similar, and the width variation range of each peak is not very large. Therefore, within the entire spectral range, a standard peak waveform (referred to as the standard wave) is used to match, and the correlation coefficient between them is calculated. If the correlation coefficient is large, it indicates the gas peak, otherwise it is a "false peak" (i.e., interference peak).

[0014]

[0015] Among them are two sets of data for which the correlation coefficient is required, and are the average values of the two sets of data respectively. If the correlation coefficient R is larger, the two sets of data are more similar. S4. The second type: the automatic baseline tracking algorithm Chromatographic quantitative analysis is carried out by measuring the height of the component peak deviating from the baseline. The reasonable and accurate division of the baseline directly affects the accuracy of quantification. Since the on-line operation of the cable insulation aging and overheating fault sensing device based on trace gases has no manual intervention, the system must have the function of automatic baseline tracking.

[0016] The system plans to adopt the sliding window extreme value extraction algorithm to achieve the function of pulling the baseline. This algorithm determines the contour points in the original spectrum according to the property that the contour points are minimum values in a certain area of the original spectrum. The specific method is: the sliding window starts from the origin of the original spectrum and slides from left to right. For each point it slides, the minimum point within the sliding window is found, and it slides until the end point of the spectrum curve, so as to obtain the contour points of the baseline. S5. Compare the data obtained from the test with the normal parameters through two different algorithms to find abnormal points. According to the comparison results, judge the specific type of the fault, whether it is an open circuit, a short circuit, or damage to the insulation layer. S6. Use a cable path tester to accurately determine the cable's routing and burial depth, narrow down the scope of fault location, and in combination with a time-domain reflectometer and other testing methods, use a cable fault locator for precise positioning to determine the specific location of the fault point. S7. After identifying the faulty section, isolate it and cut off the power supply of the faulty cable to avoid affecting other normally operating cables. Depending on the specific situation of the fault, repair or replace the cable to ensure the normal power supply of the power system.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention is a method and system for fault perception and diagnosis of power transmission cables based on trace gas analysis. The gas sensing device provided in the present invention can monitor the trace gases released due to cable insulation defects and high temperature in high-voltage power transmission cable wells. The concentration automatic calibration algorithm in the device is used to determine whether to give a warning prompt. The monitoring data and results are sent to the intelligent status online monitoring platform through the wireless ad hoc network access device. The operation and maintenance personnel can remotely monitor the current operating status of the cable, decide whether on-site inspection and maintenance are required, and formulate on-site inspection plans.

[0018] (2) The present invention is a method and system for fault perception and diagnosis of power transmission cables based on trace gas analysis. The multi-component trace gas sensing circuit and output signal amplification circuit provided in the present invention complete the software development and hardware design of the cable trace gas sensing device. The device hardware system is constructed with a low-power single-chip microcomputer as the core, and a gas path control system based on a permanent magnet brushless micro gas pump is designed to increase the gas detection flow rate; a detection circuit is used to amplify the weak signal output by the sensing circuit to improve the detection sensitivity of the sensing module. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0020] Figure 1 is the overall technical framework of a method and system for fault perception and diagnosis of power transmission cables based on trace gas analysis according to an embodiment of the present invention; Figure 2 is a schematic diagram of the hardware system design of the cable trace gas sensing device according to the present invention; Figure 3 is the data framework diagram of the intelligent perception, diagnosis, analysis, and early warning platform for cable aging and overheating fault hazards according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Next, in combination with the accompanying drawings and specific embodiments, the invention will be further described: Please refer to Figures 1-3 , a power transmission cable fault perception and diagnosis system based on trace gas analysis according to an embodiment of the present invention. The gas sensing system in the power supply module can be designed as a low-power circuit, powered by a high-performance 3.6V lithium thionyl chloride battery, with data collection performed once a day, and the power supply duration can reach 6 years, and no power wiring is required for installation.

[0022] In this embodiment, the gas sensing module can select a high-sensitivity gas sensing probe according to the qualitative and quantitative grouping test results of trace gases in the cable, and convert the gas content into a weak current signal through A / D.

[0023] 4. A power transmission cable fault perception and diagnosis system based on trace gas analysis according to claim 1, wherein the data acquisition module processes the current signal collected by the gas sensing probe and finally converts it into a voltage signal. The acquisition module is designed with a bandwidth of 1MHz, a sampling frequency of 2MHz, a storage depth of 10kB, and a resolution of 16 bits.

[0024] 5. A power transmission cable fault perception and diagnosis system based on trace gas analysis according to claim 1, wherein the gas path module is designed at the front end of the gas sensing device, and a detection circuit is used to amplify the weak signal output by the sensing circuit to improve the detection sensitivity of the trace gas sensing module.

[0025] 6. A power transmission cable fault perception and diagnosis system based on trace gas analysis according to claim 1, wherein the pump drive module is designed with a micro-pump drive module to pump air into the gas path to increase the intake air volume. The traditional position sensor of the micro-pump is removed, and a state observer is used to estimate the speed of the permanent magnet brushless micro-pump to achieve speed closed-loop control.

[0026] 7. A power transmission cable fault perception and diagnosis method and system based on trace gas analysis according to claim 1, wherein the communication module uses a wireless LoRa communication method based on the Internet of Things self-organizing network protocol to forward data to the access device.

[0027] A power transmission cable fault perception and diagnosis method and system based on trace gas analysis, characterized by the following steps: S1. First, observe the operating conditions of the power system, pay attention to whether there are voltage instability, power outage phenomena or abnormal sounds, and record in detail the location, time and possible causes of the fault. On the premise of ensuring safety, disconnect the power supply, and conduct a detailed inspection of the appearance of the cable to find out whether there are obvious concavities, scorches or cracks, etc. S2. For the characteristic gas components and contents of cable materials at different temperatures, study the automatic calibration algorithm for gas concentration, calibrate the system alarm threshold, improve the detection accuracy of the system, and reduce the false alarm rate; S3. The algorithm includes: The first one: the automatic spectral peak recognition algorithm Since there is no manual assistance at the working site of the cable insulation aging and overheating fault sensing device based on trace gases, it must have the function of automatic spectral peak recognition. Considering that the peak waveforms of each gas component are similar and the width variation range of each peak is not very large, a standard peak waveform (abbreviated as the standard wave) is used to match within the entire spectral range, and the correlation coefficient between them is calculated. If the correlation coefficient is large, it means that there is a gas peak; otherwise, it is a "false peak" (i.e., an interference peak).

[0028]

[0029] Among them are two sets of data for which the correlation coefficient is required, and are the average values of the two sets of data respectively. If the correlation coefficient R is larger, the two sets of data are more similar; S4. The second one: the automatic baseline tracking algorithm Chromatographic quantitative analysis is carried out by measuring the height of the component peak deviating from the baseline. The reasonable and accurate division of the baseline directly affects the accuracy of quantification. Since there is no manual intervention when the cable insulation aging and overheating fault sensing device based on trace gases is working online, the system must have the function of automatic baseline tracking.

[0030] The system plans to adopt the sliding window extreme value extraction algorithm to realize the function of pulling the baseline. According to the property that the contour points are minimum values in a certain area of the original spectrum, a sliding window is used to determine the contour points in the original spectrum. The specific method is as follows: The sliding window starts from the origin of the original spectrum and slides from left to right. For each point it slides, the minimum point within the sliding window is calculated until it slides to the end point of the spectral curve, so as to obtain the contour points of the baseline; S5. Compare the data obtained from the test with the normal parameters through two different algorithms, find the abnormal points, and judge the specific type of the fault according to the comparison results, whether it is an open circuit, a short circuit or insulation layer damage; S6. Use a cable path tester to accurately determine the direction and burial depth of the cable, narrow the scope of fault search, and combine with a time domain reflectometer and other test methods to use a cable fault locator for precise positioning to determine the specific location of the fault point; S7. After confirming the faulty section, isolate it and cut off the power supply of the faulty cable to avoid affecting other normally operating cables. According to the specific situation of the fault, repair or replace the cable to ensure the normal power supply of the power system; Among them: Figure 3 The system functions of the intelligent perception diagnosis analysis and early warning platform for hidden dangers of cable aging and overheating faults in mainly include: (1) Power equipment status assessment Statistically display the equipment status of the cables under the currently connected devices, including the number of normal, offline, alarmed, and total devices, and display the abnormality rate of the devices; (2) Equipment list Displays the status of the online detection sensors connected to all access devices, lists the names, test points, and status of each device; when there are too many devices to be displayed on one interface, the method of swiping up and down can be used to view; (3) Abnormal trend of power equipment and its handling statistics: In the chart at the upper right of the main interface, a trend chart of the abnormal proportion in the past week can be displayed. Taking each day as the data unit, select the ratio of the number of abnormal devices to the total number of devices on the current day as the representative value, connect the data of each day and display it as a trend chart; (4) Gas monitoring data list Click on a specific data entry in any gas monitoring data list to enter the details interface of that data; (5) Trend analysis By default, display the amplitude values of the device at each time point today and display them as a trend chart. Select one data as the representative value every hour on average; you can choose to view the amplitude trend analysis chart of the device for one month, six months, or a custom time period as needed; (6) Real-time gas monitoring data

[0031] In this embodiment, the present invention establishes the relationship between the critical pyrolysis characteristic quantity of cable insulation, the degree of insulation deterioration, and hidden dangers of faults based on the volatile organic compounds generated when the cable insulation fails. On this research basis, a cable insulation aging and overheating fault sensing device based on trace gases is developed, and an intelligent perception diagnosis analysis and early warning platform for hidden dangers of high-voltage cable aging and overheating faults is developed. By using the trace gas detection technology at high temperatures, qualitative and quantitative analysis of the trace gases decomposed by the overheating fault of the transmission cable is carried out to achieve the purpose of identifying and predicting the early hidden dangers of the operating cable. Among them Figure 3 the platform can conduct on-line monitoring and autonomous early warning of the content of the gas decomposed by the cross-linked polyethylene cable when heated, and mainly perform big data calculation, storage, and display. The role of the data background is to integrate the massive information resources in the network into a large interconnected network through computing power, and solve the problems of data storage, retrieval, use, mining, and security and privacy protection.

[0032] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "top", "bottom", "one side", "the other side", "front", "rear", "middle part", "interior", "top end", "bottom end", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention; the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance; in addition, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected to" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0033] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A transmission cable fault sensing and diagnosis system based on trace gas analysis, characterized in that: It includes a power supply module, a gas sensor module, a data acquisition module, a gas circuit module, a pump drive module and a communication module; The cable trace gas sensing system consists of a power supply module, a gas sensing module, a data acquisition module, a gas circuit module, a pump driving module and a communication module.

2. A transmission cable fault sensing and diagnosis system based on trace gas analysis according to claim 1, characterized in that: The gas sensing system in the power supply module can be designed as a low-power circuit, powered by a high-performance 3.6V lithium-ion battery, with data collection performed once a day. The power supply time can reach 6 years, and no power wiring is required during installation.

3. A transmission cable fault sensing and diagnosis system based on trace gas analysis according to claim 1, characterized in that: The gas sensing module can select a high-sensitivity gas sensing probe according to the qualitative and quantitative grouping test results of the cable trace gas, and realize the conversion of the gas content into a weak current signal through A / D.

4. The power transmission cable fault sensing and diagnosis system based on trace gas analysis according to claim 1 is characterized in that: The data acquisition module processes the current signal collected by the gas sensor probe and finally converts it into a voltage signal. The acquisition module is designed with a bandwidth of 1 MHz, a sampling frequency of 2 MHz, a storage depth of 10 kB, and a resolution of 16 bits.

5. The power transmission cable fault sensing and diagnosis system based on trace gas analysis according to claim 1 is characterized in that: The gas path module is designed to be located at the front end of the gas sensor device, and a detection circuit is used to amplify the weak signal output by the sensor circuit to improve the detection sensitivity of the trace gas sensor module.

6. The power transmission cable fault sensing and diagnosis system based on trace gas analysis according to claim 1 is characterized in that: The pump driving module is designed as a micro pump driving module to evacuate the gas path and increase the air intake. The micro pump removes the traditional position sensor and uses a state observer to estimate the speed of the permanent magnet brushless micro pump to achieve speed closed-loop control.

7. A method and system for sensing and diagnosing power transmission cable faults based on trace gas analysis according to claim 1, characterized in that: The communication module adopts the wireless LoRa communication method based on the Internet of Things self-organizing network protocol to realize the forwarding of data to the access device. A method and system for sensing and diagnosing power transmission cable faults based on trace gas analysis, characterized in that: The following steps are described: S1. First, observe the operation of the power system, pay attention to whether there is voltage instability, power outage or abnormal sound, and record the location, time and possible cause of the fault in detail. Disconnect the power supply under the premise of ensuring safety, and carefully check the appearance of the cable to find out whether there are obvious bumps, burns or cracks; S2. According to the characteristic gas composition and content of cable materials at different temperatures, the gas concentration automatic calibration algorithm is studied to calibrate the system alarm threshold, improve the system detection accuracy, and reduce the false alarm rate; S3, algorithms include; the first one: spectrum peak automatic identification algorithm Since there is no manual assistance at the work site of the cable insulation aging and overheating fault sensing device based on trace gas, it must have the function of automatic spectrum peak recognition. Considering that the peak waveform of each gas component is similar, and the width variation range of each peak is not very large, a standard peak waveform (referred to as standard wave) is used to match the entire spectrum range to calculate the correlation coefficient. The one with a large correlation coefficient is the gas peak, otherwise it is a "pseudo peak" (i.e. interference peak); ； in For two sets of data whose correlation coefficient is required, and are the average values ​​of the two sets of data respectively. If the correlation coefficient R is larger, the two sets of data are more similar; S4. Second type: automatic baseline tracking algorithm Chromatographic quantitative analysis is performed by measuring the height of component peaks deviating from the baseline. The reasonable and accurate division of the baseline directly affects the accuracy of quantification. Since the cable insulation aging and overheating fault sensing device based on trace gas works online without manual intervention, the system must have an automatic baseline tracking function. The system plans to use a sliding window extreme value extraction algorithm to achieve the baseline drawing function. This algorithm uses a sliding window to determine the contour points in the original spectrum according to the property that the contour points are minimum values ​​in a certain area of ​​the original spectrum. The specific method is: the sliding window starts from the origin of the original spectrum and slides from left to right. Each time it slides a point, the minimum point in the sliding window is obtained, and it slides until it reaches the end of the spectrum curve, so as to obtain the contour points of the baseline; S5. Compare the test data with normal parameters through two different algorithms to find abnormal points. According to the comparison results, determine the specific type of fault, whether it is open circuit, short circuit or insulation layer damage; S6. Use the cable path tester to accurately determine the direction and burial depth of the cable, narrow the scope of fault search, combine the time domain reflectometer and other test methods, and use the cable fault locator to accurately locate and determine the specific location of the fault point; S7. After confirming the faulty section, isolate it and disconnect the power supply of the faulty cable to avoid affecting other normally operating cables. According to the specific situation of the fault, repair or replace the cable to ensure the normal power supply of the power system.

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