An Analysis Method and System for the Aging State of Overhead Lines Based on Frequency Domain Dielectric Spectroscopy

Abstract

The present application discloses a method and system for analyzing the aging state of overhead lines based on frequency domain dielectric spectroscopy, aiming to solve the technical problem that the existing aging state analysis methods are difficult to accurately detect the overall aging phenomenon of overhead lines. The method includes: a computer device determines the information of the test sample to be tested; a frequency domain dielectric spectroscopy tester tests the frequency domain dielectric spectroscopy of the test sample under the current aging state based on a preset test frequency range, and sends the test result to the computer device; the computer device respectively determines the frequency domain dielectric spectroscopy of the test sample in the non-aging state and the fully aging state in the dielectric spectroscopy database; the computer device compares the received frequency domain dielectric spectroscopy of the test sample under the current aging state with the frequency domain dielectric spectroscopy of the test sample in the non-aging state and the frequency domain dielectric spectroscopy of the test sample in the fully aging state to determine the current aging state of the test sample. Through the above method, the overall aging phenomenon of overhead lines can be accurately detected.

Description

Technical Field

[0001] This application relates to the technical field of power systems, and particularly to a method and system for analyzing the aging state of overhead lines based on frequency-domain dielectric spectroscopy. Background Art

[0002] In the rapidly developing power system of our country, the safety and reliability of the power transmission and distribution system are crucial for the safe and stable operation of the entire power system. Among them, overhead lines play an important role in the power transmission and distribution system. Cross-linked polyethylene insulated overhead lines are widely used in high-voltage and large-span power transmission due to their good insulation performance. However, due to cable overcapacity and the influence of bad weather, it is easy to cause the gradual deterioration of the insulation layer of overhead lines during operation, resulting in the aging of overhead lines, which seriously affects the safe operation of the power system.

[0003] In the existing analysis process of the aging state of overhead lines, oscillation wave partial discharge testing and dielectric response testing are usually adopted. However, in the actual application process, it is difficult to detect the overall aging phenomenon of overhead lines by oscillation wave partial discharge testing, and the test results of dielectric response testing are easily affected by interference factors, resulting in deviation of the test results and difficulty in correction, which is likely to cause inaccurate analysis of the aging phenomenon. Summary of the Invention

[0004] An embodiment of this application provides a method and system for analyzing the aging state of overhead lines based on frequency-domain dielectric spectroscopy, which are used to solve the technical problems that the existing methods for analyzing the aging state of overhead lines are difficult to detect the overall aging phenomenon of overhead lines and cannot ensure the accuracy of the analysis results.

[0005] On the one hand, an embodiment of this application provides a method for analyzing the aging state of overhead lines based on frequency-domain dielectric spectroscopy, including: a computer device determines the information of the test article to be tested; a frequency-domain dielectric spectroscopy tester tests the frequency-domain dielectric spectroscopy of the test article under the current aging state based on a preset test frequency range, and sends the test results to the computer device; the computer device determines the frequency-domain dielectric spectroscopy of the test article under the non-aging state and the frequency-domain dielectric spectroscopy of the test article under the fully aging state in the pre-stored dielectric spectroscopy database; the computer device compares the frequency-domain dielectric spectroscopy of the test article under the current aging state received from the frequency-domain dielectric spectroscopy tester with the frequency-domain dielectric spectroscopy of the test article under the non-aging state and the frequency-domain dielectric spectroscopy of the test article under the fully aging state to determine the current aging state of the test article.

[0006] An overhead line aging state analysis method based on frequency domain dielectric spectroscopy provided by an embodiment of the present application determines the aging state of a test article by measuring the frequency domain dielectric spectroscopy of the test article and comparing it with the frequency domain dielectric spectroscopy in the fully aged state and the frequency domain dielectric spectroscopy in the unaged state. This not only ensures the accuracy of the determined aging state result, but also this method is not limited to determining local aging phenomena of the overhead line, and realizes the discovery of the overall aging phenomenon of the test article of the overhead line.

[0007] In an implementation manner of the present application, the computer device determines the test article information, specifically including: the computer device determines the model of the test article; the computer device determines that one end of the test article is a conductor and the other end is an insulating layer; wherein, copper wires are wound around both ends of the insulating layer, and a copper mesh is wound around the middle position to serve as a low-voltage electrode during the frequency domain dielectric spectroscopy test.

[0008] In an implementation manner of the present application, the computer device determining the test article information further includes: the computer device determines that the copper wires at both ends of the insulating layer of the test article are grounded to lead out the leakage current on the surface of the insulating layer of the test article.

[0009] The test article in the embodiment of the present application is different from the traditional test article. Instead, copper wires are wound around both ends of the insulating layer, and the copper wires are grounded to achieve the purpose of leading out the leakage current on the insulating layer of the test article, thereby ensuring the accuracy of the measured frequency domain dielectric spectroscopy.

[0010] In an implementation manner of the present application, the computer device determines the frequency domain dielectric spectroscopy of the test article in the unaged state and determines the frequency domain dielectric spectroscopy of the test article in the fully aged state in the dielectric spectroscopy database, specifically including: the computer device traverses the dielectric spectroscopy database based on the model of the test article; when the computer device determines that the cable model corresponding to any frequency domain dielectric spectroscopy included in the dielectric spectroscopy database is the same as the model of the test article, it determines the frequency domain dielectric spectroscopy of the test article in the unaged state and determines the frequency domain dielectric spectroscopy of the test article in the fully aged state.

[0011] In the embodiment of the present application, the frequency domain dielectric spectroscopy in the fully aged state and the frequency domain dielectric spectroscopy in the unaged state corresponding to the test article are determined in the dielectric spectroscopy database through the model of the test article, which ensures that the determined frequency domain dielectric spectroscopy in the fully aged state and the frequency domain dielectric spectroscopy in the unaged state are the dielectric spectroscopies corresponding to the test article in the fully aged or unaged state, thereby ensuring the accuracy of the aging state determined by comparing the dielectric spectroscopies subsequently.

[0012] In an implementation of the present application, the computer device compares the frequency-domain dielectric spectrum of the test sample in the current aging state received with the frequency-domain dielectric spectrum of the test sample in the non-aging state and the frequency-domain dielectric spectrum of the test sample in the fully aged state to determine the current aging state of the test sample. Specifically, it includes: the computer device displays the frequency-domain dielectric spectrum of the test sample in the current aging state, the frequency-domain dielectric spectrum of the test sample in the non-aging state, and the frequency-domain dielectric spectrum of the test sample in the fully aged state in the same dielectric spectrum diagram; the computer device respectively compares the frequency-domain dielectric spectrum of the test sample in the current aging state with the frequency-domain dielectric spectrum of the test sample in the non-aging state and the frequency-domain dielectric spectrum of the test sample in the fully aged state based on the pre-divided first frequency range, second frequency range, and third frequency range; where the first frequency range is 0.001 - 0.1 HZ; the second frequency range is 0.1 HZ - 10 HZ; the third frequency range is 10 HZ - 1 kHz.

[0013] In an implementation of the present application, the method further includes: when the computer device determines that the frequency-domain dielectric spectrum value of the test sample in the current aging state is less than the frequency-domain dielectric spectrum value of the test sample in the non-aged state and greater than the frequency-domain dielectric spectrum value of the test sample in the fully aged state in the first frequency range, it determines that the current aging state of the test sample is aging.

[0014] In an implementation of the present application, after determining that the current aging state of the test sample is aging, the method further includes: the computer device determines that the aging cause of the test sample is leakage conduction loss. That is, the leakage current caused by the conductance of the test sample itself leads to the aging of the test sample.

[0015] In an implementation of the present application, after determining that the current aging state of the test sample is aging, the method further includes: the computer device calculates the average value of the first difference between the frequency-domain dielectric spectrum value of the test sample in the current aging state and the frequency-domain dielectric spectrum value of the test sample in the fully aged state in the second frequency range; when the average value of the first difference is greater than the preset value, it determines that the current aging state of the test sample is aging.

[0016] In an implementation of the present application, after determining that the current aging state of the test sample is aging, the method further includes: the computer device calculates the average value of the second difference between the frequency-domain dielectric spectrum value of the test sample in the current aging state and the frequency-domain dielectric spectrum value of the test sample in the fully aged state in the third frequency range; when the average value of the second difference is less than or equal to the preset value, it determines that the current aging state of the test sample is fully aged.

[0017] On the other hand, the embodiment of the present application also provides an overhead line aging state analysis system based on frequency domain dielectric spectroscopy, including a computer device and a frequency domain dielectric spectroscopy tester; wherein, the computer device is used to determine the information of the test sample to be tested; the frequency domain dielectric spectroscopy tester is used to test the frequency domain dielectric spectroscopy of the test sample under the current aging state based on a preset test frequency range, and send the test result to the computer device; the computer device is further used to determine the frequency domain dielectric spectroscopy of the test sample in the non-aging state and the frequency domain dielectric spectroscopy of the test sample in the fully aging state in the pre-stored dielectric spectroscopy database; the computer device is further used to compare the received frequency domain dielectric spectroscopy of the test sample under the current aging state from the frequency domain dielectric spectroscopy tester with the frequency domain dielectric spectroscopy of the test sample in the non-aging state and the frequency domain dielectric spectroscopy of the test sample in the fully aging state, so as to determine the current aging state of the test sample. Description of the Drawings

[0018] The drawings described herein are used to provide a further understanding of the present application, and constitute a part of the present application. The schematic embodiments and descriptions thereof of the present application are used to explain the present application, and do not constitute an improper limitation of the present application. In the drawings:

[0019] Figure 1 It is a flowchart of a method for analyzing the aging state of an overhead line based on frequency domain dielectric spectroscopy provided by an embodiment of the present application;

[0020] Figure 2 It is a schematic structural diagram of a test sample to be tested provided by an embodiment of the present application;

[0021] Figure 3 It is a frequency domain dielectric spectroscopy diagram of a test sample under different aging degrees provided by an embodiment of the present application;

[0022] Figure 4 It is a structural diagram of an overhead line aging state analysis system based on frequency domain dielectric spectroscopy provided by an embodiment of the present application. Detailed Embodiments

[0023] To make the purpose, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0024] In the rapidly developing power system of our country, the safety and reliability of the power transmission and distribution system are crucial for the safe and stable operation of the entire power system, and overhead lines play an important role. With the increasing complexity of urban power transmission and distribution corridors, the power supply reliability of traditional overhead bare conductors often decreases when affected by adverse weather, complex environments (such as passing through tree branches and leaves), etc., posing potential safety hazards to the surrounding environment of the bare conductors. Therefore, the phenomenon of using overhead insulated cables instead of overhead bare conductors is becoming more and more common. Cross-linked polyethylene cables (XLPE) are increasingly widely used in urban power transmission and distribution systems due to their excellent performance and convenient installation.

[0025] Compared with overhead bare conductors, cross-linked polyethylene insulated overhead lines have good insulation performance, especially suitable for high-voltage and large-span power transmission. However, due to the influence of complex environmental conditions, cable overcapacity and adverse weather often occur during the on-site operation of cross-linked polyethylene insulated overhead lines, which can easily lead to the gradual deterioration of the cable insulation layer during operation, resulting in a decrease in insulation performance and seriously affecting the safe operation of the power system. Therefore, effectively diagnosing the insulation state of cross-linked polyethylene insulated overhead lines is of great significance for improving the safety of power equipment and overhead line transmission channels.

[0026] At present, the "GB 50217-2018 Design Standard for Electric Cables in Power Engineering" clearly stipulates that the maximum temperature of cross-linked polyethylene cables under normal operation shall not exceed 90°C. However, during the long-term operation of the cables, local overheating of the cables is still likely to occur due to reasons such as overcapacity during laying, the influence of complex weather, and excessive short-term load. Therefore, analyzing the thermal aging state of overhead insulated lines, combined with scientific maintenance planning methods and operation and maintenance strategies, and effectively screening overhead lines with a high degree of urgent maintenance can make the operation and maintenance work of overhead lines more targeted, greatly reducing the work burden and operation and maintenance costs of front-line operation and maintenance personnel, and is of great significance for improving power supply reliability.

[0027] At present, the main methods for judging the insulation state of overhead cables include visual inspection and withstand voltage tests. However, visual inspection and withstand voltage tests can only roughly determine whether the overhead line is damaged and cannot quantitatively determine the insulation state of the overhead line. In this case, whether the cable should be repaired or replaced can only be determined based on the experience of operation and maintenance personnel, and the judgment is highly subjective. Therefore, how to quantitatively evaluate the deterioration status of overhead insulated cables and reduce or avoid cable failures has become an extremely urgent issue in the operation and maintenance work of the power transmission network.

[0028] Compared with traditional methods, in recent years, oscillating wave partial discharge tests and dielectric response tests have gradually been applied in important cities at home and abroad and have achieved relatively obvious results.

[0029] At present, the oscillating wave method has been able to effectively identify the type of defects and locate the corresponding defects, which has strongly guided the safe production work of power grid companies. However, the oscillating wave method mainly detects the discharge phenomenon caused by local defects in cables and is difficult to detect the overall aging or moisture absorption phenomenon of cables.

[0030] The dielectric response method can be divided into time-domain dielectric response and frequency-domain dielectric response methods. Among them, the time-domain dielectric test methods include: Polarization and Depolarization Current (PDC) method and Recovery Voltage Method (RVM). Among them, PDC judges the insulation state of the test object by measuring the charging current (polarization current) of the test object under the action of a step single-polarity voltage and the discharging current (depolarization current) in the relaxation state. However, when conducting PDC and RVM tests on overhead lines, due to the more complex electromagnetic environment and the denser distribution of busbars and feeders, the test results are more affected by interference. Coupled with the fact that most of the commonly used non-linear fitting methods are local optimizations, it leads to a high degree of uncertainty in the post-processing and fitting of test data, restricting the applicable range of the time-domain dielectric response method and affecting the popularization and application of the PDC and RVM methods in the field. Conventional electrical means, such as insulation resistance, absorption ratio, power frequency dielectric loss test, etc., also belong to the dielectric response method, but the test information is mainly the step response at steady state and the frequency-domain dielectric response at a single power frequency point. Such methods have a certain effectiveness for insulation diagnosis, but it is difficult to quantify the degree of moisture absorption and aging degree in the evaluation results. When facing the change of the insulation temperature of on-site equipment, there are certain deviations in the measurement results and it is difficult to correct. Therefore, studying the frequency-domain dielectric spectrum of insulated overhead lines is of great significance for mastering their overall insulation state.

[0031] Therefore, the embodiments of the present application provide a method and system for analyzing the aging state of overhead lines based on the frequency-domain dielectric spectrum. By testing the frequency-domain dielectric spectrum of the overhead line specimen under the current state and comparing it with the frequency-domain dielectric spectrum of the overhead line specimen corresponding to the fully aged state and the non-aged state, the current aging state of the overhead line specimen is determined. To solve the technical problems in the above-mentioned existing technologies that the method for analyzing the aging state of overhead lines cannot detect the overall aging phenomenon of overhead lines and cannot ensure the accuracy of the determined aging state.

[0032] The technical solutions proposed in the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0033] Figure 1 It is a flowchart of a method for analyzing the aging state of overhead lines based on the frequency-domain dielectric spectrum provided by the embodiments of the present application. As Figure 1As shown in the figure, the aging state analysis process of the test sample in the embodiment of the present application mainly includes the following steps:

[0034] Step 101, the computer device determines the information of the test sample.

[0035] A method for analyzing the aging state of an overhead line based on frequency domain dielectric spectroscopy proposed in the embodiment of the present application first needs to determine the overhead line to be tested during execution, and then preprocess it to obtain the test sample. Specifically: select the overhead line sample that needs to be analyzed for aging state, and then process one end of the overhead line sample to expose the conductor contained inside the insulation layer, and do not process the insulation layer at the other end; secondly, wind tight copper wires around both ends of the insulation layer at the other end of the overhead line sample, and wind a tight copper mesh in the middle position of the insulation layer to act as the low electrode during frequency domain dielectric spectroscopy testing. It should be noted that the copper wires and copper mesh wound around the middle position and both ends of the insulation layer are not connected.

[0036] Figure 2 It is a schematic structural diagram of a test sample provided by the embodiment of the present application. As Figure 2 shown, one end of the overhead line test sample is conductor 1, and the other end is insulation layer 2; and copper wires 3 are wound around both ends of the insulation layer 2 and a copper mesh 3 is wound in the middle position of the insulation layer 2.

[0037] Furthermore, before the computer device analyzes the aging state of the test sample, it first determines the information of the test sample. Specifically: the computer device determines the model of the test sample, and at the same time determines that one end of the test sample is a conductor and the other end is an insulation layer; and copper wires are wound around both ends of the insulation layer, and a copper mesh is wound in the middle position to determine that the test sample meets the requirements of the frequency domain dielectric spectroscopy test process.

[0038] It should be noted that the computer device also determines that the copper wires at both ends of the insulation layer of the test sample are grounded, so as to export the leakage current on the surface of the insulation layer of the overhead line test sample, thereby ensuring the accuracy of the measured frequency domain dielectric spectroscopy.

[0039] Step 102, the frequency domain dielectric spectrometer performs dielectric spectroscopy testing on the test sample.

[0040] After the computer device determines that the test sample meets the requirements of the frequency domain dielectric spectroscopy test, the frequency domain dielectric spectrometer tests the frequency domain dielectric spectroscopy of the test sample under the current aging state based on the pre-determined test frequency range. Specifically, one end of the conductor of the test sample is the high-voltage electrode during testing, and the copper mesh on the insulation layer of the test sample is the low-voltage electrode during testing. Connect the test sample to the frequency domain dielectric spectrometer to implement the frequency domain dielectric spectroscopy test process.

[0041] It should be noted that the frequency domain dielectric spectroscopy test can measure the capacitance C in the conventional preventive test50Hz and the dielectric loss tangent value tanδ 50Hz The test expands from a single power frequency point to the low-frequency and high-frequency bands respectively, so as to reflect the polarization characteristics of the material at different frequencies. The dielectric loss tangent value can be expressed by the formula:

[0042]

[0043] where ε″ r is the imaginary part of the relative permittivity, and ε′ r is the real part of the relative permittivity, ε″(ω) is the imaginary part of the permittivity, σ0 is the conductivity corresponding to the overhead line material to be tested, with the unit of S·m-1; ε0 is the vacuum permittivity.

[0044] It can be seen from the formula that since tanδ can intuitively reflect the change of the permittivity, and the permittivity is closely related to the insulation characteristics or aging state of the product to be tested. Therefore, in the embodiments of the present application, the insulation characteristics or aging state of the overhead line product to be tested can be reflected by the test results of tanδ.

[0045] It should also be noted that the frequency-domain dielectric spectroscopy test is widely used in composite material equipment such as oil-paper insulated transformers and their bushings. For most insulating materials, the main sources of dielectric loss in different frequency bands are different. Among them, the conductivity and polarization loss directly related to deterioration mainly exist in the middle and low frequency bands. Therefore, when the insulation characteristics or aging state of the overhead line deteriorates, the change in the middle and low frequency bands of the frequency-domain dielectric spectroscopy is more obvious. Therefore, in the embodiments of the present application, the frequency-domain dielectric spectroscopy at 1 kHz and below frequencies is mainly studied. That is, the preset test frequency range in the embodiments of the present application is 0.001 HZ - 1 kHz.

[0046] Further, after the frequency-domain dielectric spectroscopy tester completes the test, it sends the measured frequency-domain dielectric spectroscopy of the product to be tested in the current aging state to the computer device.

[0047] Step 103: The computer device determines the frequency-domain dielectric spectroscopy of the product to be tested in the unaged state and the frequency-domain dielectric spectroscopy in the fully aged state.

[0048] After the computer device receives the frequency-domain dielectric spectrum of the test sample in the current aging state sent by the frequency-domain dielectric spectrum tester, it determines the frequency-domain dielectric spectra of the test sample in the fully aged state and the unaged state in the pre-stored dielectric spectrum database. Specifically, the computer device traverses the dielectric spectrum database according to the overhead line model corresponding to the test sample; then, when the computer device determines that the cable model corresponding to any frequency-domain dielectric spectrum included in the dielectric spectrum database is the same as the test sample model, it retrieves the frequency-domain dielectric spectrum in the fully aged state and the frequency-domain dielectric spectrum in the unaged state corresponding to any frequency-domain dielectric spectrum as the frequency-domain dielectric spectrum in the fully aged state and the frequency-domain dielectric spectrum in the unaged state of the test sample.

[0049] Step 104: The computer device determines the current aging state of the test sample.

[0050] The computer device compares the frequency-domain dielectric spectrum of the test sample in the current aging state received from the frequency-domain dielectric spectrum tester with the frequency-domain dielectric spectrum of the test sample in the unaged state and the frequency-domain dielectric spectrum of the test sample in the fully aged state to determine the current aging state of the test sample.

[0051] Specifically, first, the computer device displays the frequency-domain dielectric spectrum of the test sample in the current aging state, the frequency-domain dielectric spectrum of the test sample in the unaged state, and the frequency-domain dielectric spectrum of the test sample in the fully aged state in the same dielectric spectrum diagram; then, it divides the preset test frequency range, and the division results are as follows: the first frequency range is 0.001 - 0.1 HZ, the second frequency range is 0.1 HZ - 10 HZ, and the third frequency range is 10 HZ - 1 kHz; finally, it compares the frequency-domain dielectric spectrum of the test sample in the current aging state with the frequency-domain dielectric spectrum of the test sample in the fully aged state and the frequency-domain dielectric spectrum of the test sample in the unaged state within the three divided frequency ranges respectively.

[0052] Furthermore, when the computer device determines that the frequency-domain dielectric spectrum value of the test sample in the current aging state is less than the frequency-domain dielectric spectrum value of the test sample in the unaged state and greater than the frequency-domain dielectric spectrum value of the test sample in the fully aged state in the first frequency range, it determines that the current aging state of the test sample is aging.

[0053] After determining that the current aging state of the product to be tested is aging, it is further determined whether the current aging state of the product to be tested is complete aging. Specifically: The computer device calculates the average value of the first difference between the frequency-domain dielectric spectrum value of the product to be tested in the current aging state and the frequency-domain dielectric spectrum value of the product to be tested in the complete aging state in the second frequency range; and when the average value of the first difference is greater than a preset value, it is determined that the current aging state of the product to be tested is aging. And, the computer device calculates the average value of the second difference between the frequency-domain dielectric spectrum value of the product to be tested in the current aging state and the frequency-domain dielectric spectrum value of the product to be tested in the complete aging state in the third frequency range; and when the average value of the second difference is less than or equal to the preset value, it is determined that the current aging state of the product to be tested is complete aging.

[0054] So far, the process of determining the current aging state of the product to be tested is completed.

[0055] It should be noted that an ideal insulating material can be regarded as a pure capacitor. Under the action of a sinusoidal alternating electric field, the phase angle between the voltage and current of the insulating material should be 90°. However, there is energy loss in the insulating material under the action of the alternating electric field. Therefore, the actually measured phase angle is less than 90°, and this kind of loss is called dielectric loss. The dielectric loss of the insulating material mainly comes from the following three situations:

[0056] (1) Leakage conduction loss. The insulating material cannot be an ideal insulator, so there must be leakage current caused by its own conductance, and corresponding leakage conduction loss is generated.

[0057] (2) Loss caused by dispersion and absorption processes. This kind of loss is mainly caused by the resonance effect generated when particles such as atoms vibrate, and it occurs concentratedly in the infrared to ultraviolet frequency bands. Since the frequency-domain dielectric spectrum test frequency band involved in the embodiments of the present application is 0.001 Hz - 1 kHz, which is much smaller than the infrared to ultraviolet frequency band. Therefore, it can be determined that the aging state of the product to be tested in the embodiments of the present application is not caused by the loss caused by dispersion and absorption processes.

[0058] (3) Loss caused by relaxation polarization. The relaxation polarization here includes not only interfacial polarization loss, but also other lossy polarization types such as dipole polarization. Since the development process of this kind of lossy relaxation polarization is relatively slow, when the external applied electric field frequency is high enough, the orientation of polar groups and chain segments in the insulating cross-linked polyethylene of the overhead line cannot be fully developed, resulting in the inability to complete the polarization process, making the contribution of this part to the overall polarization process disappear, causing the polarization rate of the medium as a whole to decrease and the dielectric constant to also decrease. If the frequency is high enough, the dielectric constant will drop all the way to the optical frequency dielectric constant, and this phenomenon of the dielectric constant changing with frequency is also called the dispersion phenomenon of the dielectric. Therefore, it can be determined that the aging state of the product to be tested in the embodiments of the present application is not caused by the loss caused by relaxation polarization.

[0059] Moreover, during the actual measurement of the frequency-domain dielectric spectrum, the differences in the frequency-domain dielectric spectra at different aging times are often reflected in the low-frequency band (around 0.001 Hz). Therefore, in the embodiments of the present application, the aging state of the test article is mainly dominated by the conductance loss.

[0060] It should also be noted that for a method for analyzing the aging state of an overhead line based on the frequency-domain dielectric spectrum provided by the embodiments of the present application, during actual application, the frequency-domain dielectric spectrum of the overhead line can be periodically measured, and all the measurement results can be displayed in the same dielectric spectrum diagram. At the same time, the frequency-domain dielectric spectra of the overhead line in the fully aged state and the unaged state are also displayed. Then, by comparing the newly obtained frequency-domain dielectric spectrum measured each time with the frequency-domain dielectric spectra existing in the dielectric spectrum diagram before, the aging state of the overhead line can be continuously analyzed and studied.

[0061] For example, Figure 3 is a frequency-domain dielectric spectrum diagram of a test article with different aging degrees provided by the embodiments of the present application. As Figure 3 shown, the figure shows the results of the measured tangent value of the dielectric loss angle of a 30-cm-long insulated overhead line test article after aging for 1 day, 3 days, 5 days, 10 days, 15 days, and 20 days at 100°C. It can be seen from the figure that the differences at different aging times are mainly reflected in the low-frequency band (around 0.001 Hz). As the aging time increases, the tangent value of the dielectric loss in the low-frequency band gradually decreases. Based on this, the aging state of the overhead line can be qualitatively analyzed and studied.

[0062] In summary, a method for analyzing the aging state of an overhead line based on the frequency-domain dielectric spectrum proposed by the embodiments of the present application has the following positive effects:

[0063] (1) Innovatively expand the original frequency-domain dielectric spectrum analysis method applicable to oil-paper insulation samples to the analysis of the aging state of insulated overhead lines. By using the method of comparing the frequency-domain dielectric spectrum curves in the low-frequency band, qualitatively analyze the aging state of the insulated overhead line, and can analyze the overall aging state of the overhead line, providing a new method for detecting the aging state of the overhead line and ensuring the accuracy of the aging state analysis.

[0064] (2) Innovatively correspond the leakage conductance loss, the loss of the dispersion and absorption process, and the loss caused by relaxation polarization to different frequency bands. By the curve change trends in different frequency bands to correspond to different types of losses, thereby obtaining the characteristics of the migration of impurity particles and the orientation movement of molecular chains in XLPE, which can be used to characterize the aging state or insulation state of the material.

[0065] The above is the method embodiment provided by this application. Based on the same inventive concept, the embodiment of this application also provides an overhead line aging state analysis system based on frequency domain dielectric spectroscopy, and its structure is as Figure 4 shown.

[0066] Figure 4 This is a structure diagram of an overhead line aging state analysis system based on frequency domain dielectric spectroscopy provided by the embodiment of this application. As Figure 4 shown, the system includes: a computer device and a frequency domain dielectric spectroscopy tester; wherein, the computer device is used to determine the information of the product to be tested; the frequency domain dielectric spectroscopy tester is used to test the frequency domain dielectric spectroscopy of the product to be tested in the current aging state based on a preset test frequency range, and send the test result to the computer device; the computer device is further used to determine the frequency domain dielectric spectroscopy of the product to be tested in the non-aging state and the frequency domain dielectric spectroscopy of the product to be tested in the fully aging state in the pre-stored dielectric spectroscopy database; the computer device is further used to compare the received frequency domain dielectric spectroscopy of the product to be tested in the current aging state from the frequency domain dielectric spectroscopy tester with the frequency domain dielectric spectroscopy of the product to be tested in the non-aging state and the frequency domain dielectric spectroscopy of the product to be tested in the fully aging state, so as to determine the current aging state of the product to be tested.

[0067] Each embodiment in this application is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the key points of each embodiment are the differences from other embodiments. In particular, for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment.

[0068] It should also be noted that the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. Without further limitation, the element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, commodity or device including the said element.

[0069] The above are only the embodiments of this application and are not used to limit this application. For those skilled in the art, this application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the scope of the claims of this application.

Claims

1. A method for analyzing the aging state of overhead lines based on frequency-domain dielectric spectroscopy, characterized in that, The method includes: a computer device determines information of a product to be tested; A frequency-domain dielectric spectroscopy tester tests the frequency-domain dielectric spectrum of the product to be tested in its current aging state based on a preset test frequency range, and sends the test result to the computer device; The computer device determines the frequency-domain dielectric spectrum of the product to be tested in its non-aged state and the frequency-domain dielectric spectrum of the product to be tested in its fully-aged state in a pre-stored dielectric spectrum database; The computer device compares the frequency-domain dielectric spectrum of the product to be tested in its current aging state received from the frequency-domain dielectric spectroscopy tester with the frequency-domain dielectric spectrum of the product to be tested in its non-aged state and the frequency-domain dielectric spectrum of the product to be tested in its fully-aged state to determine the current aging state of the product to be tested; The computer device compares the frequency-domain dielectric spectrum of the product to be tested in its current aging state received with the frequency-domain dielectric spectrum of the product to be tested in its non-aged state and the frequency-domain dielectric spectrum of the product to be tested in its fully-aged state to determine the current aging state of the product to be tested. Specifically, the computer device displays the frequency-domain dielectric spectrum of the product to be tested in its current aging state, the frequency-domain dielectric spectrum of the product to be tested in its non-aged state, and the frequency-domain dielectric spectrum of the product to be tested in its fully-aged state in the same dielectric spectrum graph; The computer device compares the frequency-domain dielectric spectrum of the product to be tested in its current aging state with the frequency-domain dielectric spectrum of the product to be tested in its non-aged state and the frequency-domain dielectric spectrum of the product to be tested in its fully-aged state respectively based on a pre-divided first frequency range, second frequency range, and third frequency range; Wherein, the first frequency range is 0.001 - 0.1 HZ; The second frequency range is 0.1 HZ - 10 HZ; The third frequency range is 10 HZ - 1 kHz; The method further includes: when the computer device determines that the frequency-domain dielectric spectrum value of the product to be tested in its current aging state is less than the frequency-domain dielectric spectrum value of the product to be tested in its non-aged state and greater than the frequency-domain dielectric spectrum value of the product to be tested in its fully-aged state in the first frequency range, it determines that the current aging state of the product to be tested is aging; After determining that the current aging state of the product to be tested is aging, the method further includes: the computer device determines that the aging cause of the product to be tested is leakage conduction loss; After determining that the current aging state of the product to be tested is aging, the method further includes: the computer device calculates the average value of the first difference between the frequency-domain dielectric spectrum value of the product to be tested in its current aging state and the frequency-domain dielectric spectrum value of the product to be tested in its fully-aged state in the second frequency range; When the average value of the first difference is greater than a preset value, it determines that the current aging state of the product to be tested is aging.

2. The method for analyzing the aging state of overhead lines based on frequency-domain dielectric spectroscopy according to claim 1, characterized in that, The computer device determines information of the product to be tested. Specifically, the computer device determines the model of the product to be tested; The computer device determines that one end of the product to be tested is a conductor and the other end is an insulating layer; Among them, copper wires are wound around both ends of the insulating layer, and a copper mesh is wound around the middle position to serve as the low-voltage electrode during the frequency-domain dielectric spectroscopy test.

3. The method for analyzing the aging state of overhead lines based on frequency-domain dielectric spectroscopy according to claim 2, characterized in that, The computer device determines the information of the product to be tested, and further includes: the computer device determines that the copper wires at both ends of the insulating layer of the product to be tested are grounded to export the leakage current on the surface of the insulating layer of the product to be tested.

4. The method for analyzing the aging state of overhead lines based on frequency-domain dielectric spectroscopy according to claim 2, characterized in that, The computer device determines the frequency-domain dielectric spectroscopy of the product to be tested in the non-aged state and determines the frequency-domain dielectric spectroscopy of the product to be tested in the fully-aged state in the pre-stored dielectric spectroscopy database. Specifically, it includes: the computer device traverses the dielectric spectroscopy database based on the model of the product to be tested; When the computer device determines that the cable model corresponding to any frequency-domain dielectric spectroscopy included in the dielectric spectroscopy database is the same as the model of the product to be tested, it determines the frequency-domain dielectric spectroscopy of the product to be tested in the non-aged state and determines the frequency-domain dielectric spectroscopy of the product to be tested in the fully-aged state.

5. The method for analyzing the aging state of overhead lines based on frequency-domain dielectric spectroscopy according to claim 1, characterized in that, After determining that the current aging state of the product to be tested is aged, the method further includes: the computer device calculates the average value of the second difference between the frequency-domain dielectric spectroscopy value of the product to be tested in the current aging state and the frequency-domain dielectric spectroscopy value of the product to be tested in the fully-aged state in the third frequency range; When the average value of the second difference is less than or equal to a preset value, it is determined that the current aging state of the product to be tested is fully-aged.

6. An analysis system for the aging state of overhead lines based on frequency-domain dielectric spectroscopy, adopting the method according to claims 1-5, characterized in that, The system includes a computer device and a frequency-domain dielectric spectrometer; The computer device is used to determine the information of the product to be tested; The frequency-domain dielectric spectrometer is used to test the frequency-domain dielectric spectroscopy of the product to be tested in the current aging state based on a preset test frequency range and send the test result to the computer device; The computer device is further used to determine the frequency-domain dielectric spectroscopy of the product to be tested in the non-aged state and determine the frequency-domain dielectric spectroscopy of the product to be tested in the fully-aged state in the pre-stored dielectric spectroscopy database; The computer device is further used to compare the frequency-domain dielectric spectroscopy of the product to be tested in the current aging state received from the frequency-domain dielectric spectrometer with the frequency-domain dielectric spectroscopy of the product to be tested in the non-aged state and the frequency-domain dielectric spectroscopy of the product to be tested in the fully-aged state to determine the current aging state of the product to be tested.

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