High-voltage dry-type bushing insulation aging state evaluation method based on frequency domain characteristics

Abstract

The invention belongs to the technical field of aging state evaluation, and discloses a high-voltage dry-type bushing insulation aging state evaluation method based on frequency domain characteristics. According to the method, the FDS is adopted, and the aging state of the insulating material is evaluated according to the change of the complex capacitance, the complex dielectric constant, the dielectric loss factor and the like of a medium along with the frequency under a low-voltage sine alternating electric field. The FDS shows remarkable superiority in a plurality of aspects. The method comprises the following steps: firstly, measuring a dielectric constant and dielectric loss of an insulating medium in a wide frequency range by an FDS method so as to obtain response characteristics of the insulating material under different frequencies; according to the method, the frequency domain dielectric spectroscopy FDS is combined with the advantages of wide frequency range measurement, frequency domain feature recognition, comprehensive reflection of electrical characteristics and the like, so that accurate evaluation of the insulation aging state of the high-voltage dry-type bushing is realized. The safety and the stability of a power system can be improved, and faults and accidents caused by insulation aging can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of aging status assessment, and in particular relates to a method for assessing the insulation aging status of a high-voltage dry-type bushing based on frequency domain characteristics. Background Art

[0002] During operation, high-voltage dry-type bushings are subjected to long-term thermal stress, which leads to aging of the internal insulation material, which is the primary factor in the deterioration of its insulation performance. As key insulating materials, epoxy resin and insulating paper have attracted widespread attention for their aging mechanism and impact. For epoxy resin, scholars have conducted accelerated aging experiments and found that thermal aging will significantly increase its resistivity and dielectric loss value in the low-frequency band of the dielectric spectrum, reduce insulation performance, and the aging process is accompanied by oxidation, breakage and re-crosslinking of molecular chains, resulting in a decrease in glass transition temperature and breakdown voltage. At the same time, hot electrons generated by thermal aging intensify local discharge and further promote aging. For insulating paper, its main component, α-cellulose, will undergo glycosidic bond rupture at high temperatures, resulting in a decrease in the degree of polymerization and the generation of polar products such as moisture and furan, which affects the insulation performance.

[0003] Existing research focuses on oil-paper insulation, while the aging mechanism of epoxy impregnated paper insulation and its influence on dielectric properties are still unclear, and there is a lack of effective evaluation methods. Therefore, a new method for evaluating the aging state of high-voltage dry-type bushing insulation based on frequency domain characteristics is urgently needed to accurately evaluate the aging state of epoxy impregnated paper insulation and provide a scientific basis for the maintenance and safe operation of dry-type bushings. Summary of the invention

[0004] Aiming at the problems existing in the existing high-voltage dry-type bushing insulation aging status assessment technology, the present invention proposes a high-voltage dry-type bushing insulation aging status assessment method based on frequency domain characteristics. This method achieves accurate assessment of the aging status of the insulation material by deeply analyzing the dielectric response characteristics of the insulating medium in a wide frequency range.

[0005] The specific implementation steps of the present invention are as follows:

[0006] Response characteristics acquisition: The dielectric constant and dielectric loss of the insulating medium are measured in a wide frequency range to obtain the response characteristics of the insulating material at different frequencies. This step provides a rich data basis for subsequent aging status assessment.

[0007] Aging status assessment: The aging status of insulating materials is assessed by using the frequency-dependent characteristics of dielectric complex capacitance, complex dielectric constant and dielectric loss factor under low-voltage sinusoidal alternating electric fields. By comparing the dielectric response characteristics under different frequencies, the degree of aging of insulating materials can be accurately determined.

[0008] Furthermore, the present invention defines the complex capacitance C(ω) of the dielectric, as shown in equations (1) to (3), wherein Z(ω) represents the input impedance of the dielectric, and C'(ω) and C"(ω) represent the real part and the imaginary part of the complex capacitance, respectively. By measuring the voltage and current applied to the sample, Z(ω) can be calculated, and then C(ω) can be obtained. In addition, the present invention also introduces the frequency domain dielectric response function F(ω), that is, the complex polarization rate χ*(ω), as shown in equation (4), which is an inherent property of the sample and is closely related to the aging state of the sample.

[0009]

[0010] ε * (ω)=ε′(ω)-iε″(ω)(3)

[0011]

[0012] At the same time, the present invention takes into account the influence of dielectric conductivity and modifies the definition of dielectric loss, as shown in equations (5) and (6). This makes the present invention more accurate and reliable in evaluating the aging state of insulating materials.

[0013]

[0014] Another object of the present invention is to provide a high-voltage dry-type bushing insulation aging status assessment system based on frequency domain characteristics, the system mainly includes the following two core modules:

[0015] Response characteristics acquisition module: The main function of this module is to accurately measure the dielectric constant and dielectric loss of the insulating medium in a wide frequency range, so as to obtain the detailed response characteristics of the insulating material at different frequencies. This step provides comprehensive and accurate data support for the subsequent insulation aging status assessment.

[0016] Evaluation module: This module uses the frequency-dependent characteristics of dielectric complex capacitance, complex dielectric constant and dielectric loss factor under low-voltage sinusoidal alternating electric field to conduct in-depth analysis and evaluation of the aging state of insulating materials. By comparing and analyzing the dielectric response characteristics under different frequencies, this module can accurately determine the degree of aging of insulating materials and provide a scientific basis for the maintenance and repair of power equipment.

[0017] In addition, another important object of the present invention is to provide a computer device, which includes an advanced memory and a processor. The memory stores a special computer program, which, when executed by the processor, enables the processor to perform accurate calculation and analysis according to the steps of the method for evaluating the insulation aging state of high-voltage dry-type bushings based on frequency domain characteristics.

[0018] At the same time, the present invention also relates to a computer-readable storage medium, which also stores the above-mentioned computer program. When the program is executed by any compatible processor, the processor can execute all steps of the method for evaluating the insulation aging state of high-voltage dry-type bushing based on frequency domain characteristics, thereby realizing automatic evaluation of the insulation aging state.

[0019] Finally, another object of the present invention is to provide an information data processing terminal, which is specifically used to realize all functions of the high-voltage dry-type bushing insulation aging state assessment system based on frequency domain characteristics. Through this terminal, users can easily obtain the response characteristic data of the insulation material and conduct in-depth aging state assessment and analysis.

[0020] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0021] First, in view of the technical problems existing in the above-mentioned prior art, some creative technical effects are brought about after solving the problems. The specific description is as follows:

[0022] (1) Wide frequency range measurement: The FDS method is used to measure the dielectric constant and dielectric loss of the insulating medium over a wide frequency range, and the detailed response characteristics of the insulating material at different frequencies are obtained. This makes the present invention more sensitive and accurate in identifying different types of insulation defects and aging phenomena.

[0023] (2) Frequency domain feature recognition: The FDS method can capture the changes in the microstructure of the insulation material and accurately identify and locate insulation defects through frequency domain features. Different defect types have different response characteristics to frequency, which makes the FDS method have higher resolution and accuracy in evaluating the aging state of insulation materials.

[0024] (3) Comprehensive reflection of electrical properties: By measuring parameters such as dielectric constant and dielectric loss factor, the FDS method can reflect the electrical properties of insulating materials in detail. Dielectric spectrum can reveal the polarization process, conductive properties and frequency dependence of insulating materials, which is information that other methods cannot provide.

[0025] (4) Improved evaluation accuracy: The present invention takes into account the influence of dielectric conductivity and modifies the definition of dielectric loss. This makes the evaluation of the aging state of insulating materials more accurate and reliable, and avoids evaluation errors caused by dielectric conductivity.

[0026] In summary, the present invention achieves accurate assessment of the insulation aging state of high-voltage dry-type bushings by introducing frequency domain dielectric spectroscopy FDS, combining the advantages of wide frequency range measurement, frequency domain feature recognition, and comprehensive reflection of electrical characteristics. This will help improve the safety and stability of the power system and reduce faults and accidents caused by insulation aging.

[0027] Second, as auxiliary evidence of the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0028] (1) The expected benefits and commercial value of the technical solution of the present invention after transformation are significant. By implementing the present invention, it is possible to accurately evaluate the insulation aging status of high-voltage dry-type bushings and improve the operating safety and reliability of power equipment. It is expected to significantly reduce equipment failures and maintenance costs caused by insulation aging, extend the service life of equipment, and bring significant economic benefits to the power industry. At the same time, the promotion and application of the present invention is expected to form new technical standards and market opportunities.

[0029] (2) The technical solution of the present invention fills the technical gap in the field of high-voltage dry-type bushing insulation aging status assessment at home and abroad. Traditional methods mainly rely on empirical judgment and regular testing, and lack effective quantitative assessment methods. The present invention realizes accurate quantitative assessment of insulation aging status by introducing frequency domain characteristic analysis, providing a new and scientific assessment method for the power industry, filling the technical gap in this field.

[0030] (3) The technical solution of the present invention successfully solves a technical problem that people have been eager to solve but have never succeeded in solving. For a long time, the accurate assessment of the aging state of high-voltage dry-type bushing insulation has been a major challenge facing the power industry. The present invention, through in-depth research on the correlation between the frequency domain characteristics and the aging state of insulating materials, proposes an innovative assessment method, which effectively solves this technical problem and provides a new scientific basis for the maintenance and management of power equipment.

[0031] (4) The technical solution of the present invention overcomes technical prejudice and achieves technical innovation. In traditional concepts, the evaluation of insulation aging status mainly relies on empirical judgment and simple physical testing, while ignoring the importance of frequency domain characteristics in the evaluation. The present invention breaks this technical prejudice by introducing frequency domain analysis technology and proposes a new evaluation method. This method not only improves the accuracy of the evaluation, but also opens up new ideas and methods for the study of insulation aging status.

[0032] Third, the technical solution of the present invention solves many key problems of the prior art in industrial applications and has achieved significant technical progress.

[0033] 1. Solved the problem of insufficient accuracy in insulation aging status assessment

[0034] In the power industry, insulation aging assessment of high-voltage dry-type bushings is an important part of ensuring the safe operation of power equipment. Traditional aging assessment methods mainly rely on single electrical characteristic measurements, which cannot fully capture the aging state of insulating materials, resulting in inaccurate assessment results. The present invention introduces frequency domain characteristic measurement technology to obtain the dielectric constant and dielectric loss of insulating materials in a wide frequency range, providing more comprehensive aging assessment information and significantly improving the accuracy and reliability of the assessment.

[0035] 2. Improved the accuracy and applicability of the evaluation method

[0036] The present invention adopts the analysis method of complex capacitance, complex dielectric constant and dielectric loss factor, which can more accurately reflect the aging degree of insulating materials, especially in key power equipment such as high-voltage dry-type bushings. This technical solution calculates the frequency domain dielectric response function and deeply analyzes the polarization characteristics of the material at different frequencies, thereby providing a more accurate judgment of the aging state and overcoming the evaluation error caused by insufficient information in the prior art.

[0037] 3. Overcome the problem that existing methods do not consider the influence of conductivity enough

[0038] Traditional evaluation methods often ignore the effect of conductivity on dielectric loss when calculating dielectric loss, resulting in deviations in the evaluation results. The present invention introduces the analysis of the effect of conductivity on dielectric loss to make the calculation of loss factor more accurate. Especially in the high-frequency range, this technical solution effectively solves the evaluation error problem caused by the conductivity effect, and provides technical support for the accurate judgment of insulation aging status in industrial applications.

[0039] 4. Significant technological progress and extensive industrial application value

[0040] The present invention has achieved significant technical progress in the field of insulation aging assessment of high-voltage power equipment. Through frequency domain characteristic measurement and multi-parameter analysis, this method greatly improves the accuracy and reliability of aging status assessment, can more effectively prevent insulation failure of power equipment, and ensure the safe operation of the power system. Compared with the prior art, the method of the present invention has higher accuracy and applicability, has important industrial application value, can be widely used in status monitoring, life prediction and maintenance decision-making of power equipment, and provides strong support for the safe and stable operation of the power industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flow chart of a method for evaluating the insulation aging state of a high-voltage dry-type bushing based on frequency domain characteristics provided in an embodiment of the present invention.

[0042] Figure 2It is a structural block diagram of a high-voltage dry-type bushing insulation aging status assessment system based on frequency domain characteristics provided by an embodiment of the present invention.

[0043] Figure 3 It is a schematic diagram of the FDS measurement principle provided by an embodiment of the present invention.

[0044] Figure 4 4 is a tanδ-f curve diagram of the core under different aging days provided by an embodiment of the present invention.

[0045] Figure 5 3 is a C'-f curve diagram of the core under different aging days provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0047] The following are two examples of industrial applications, showing the specific operation and effects of the present invention in practical applications:

[0048] Example 1: Power transformer insulation aging assessment

[0049] In the long-term operation of power transformers, their internal insulation materials (such as epoxy resin and impregnated paper) will gradually age over time, which may lead to a decrease in insulation performance and increase the risk of equipment failure. Traditional aging assessment methods mainly rely on partial discharge tests and simple dielectric loss measurements, which cannot fully and accurately reflect the aging status of insulation materials.

[0050] By using the high-voltage dry-type bushing insulation aging state assessment method based on frequency domain characteristics of the present invention, a more comprehensive aging state analysis of the insulation material inside the transformer can be performed. By measuring the dielectric constant and dielectric loss of the insulation material in a wide frequency range, its response characteristics at different frequencies are obtained, and the complex capacitance, complex dielectric constant and dielectric loss factor are calculated. By analyzing these data, the aging degree of the transformer insulation material can be accurately assessed, thereby predicting the remaining life of the equipment, optimizing the maintenance plan, and avoiding failures caused by insulation aging.

[0051] This method significantly improves the accuracy of aging status assessment, helps power companies manage transformer equipment more scientifically, extends equipment service life, reduces the occurrence of sudden failures, and reduces maintenance costs and operational risks.

[0052] Example 2: Aging detection of insulators in high-voltage transmission lines

[0053] Insulators in high-voltage transmission lines are exposed to the outdoors for a long time and are easily affected by environmental factors such as ultraviolet radiation, rain erosion and pollution, which makes them prone to aging. Traditional detection methods mainly rely on visual inspection and surface resistance measurement, which makes it difficult to evaluate the internal aging of insulators.

[0054] The method of the present invention can accurately evaluate the insulation state of the insulator of the high-voltage transmission line. The insulator sample is placed in a measuring fixture and connected to a frequency response analyzer to perform frequency domain measurement of its dielectric characteristics. The complex capacitance and complex dielectric constant data of the insulator material in a wide frequency range are obtained by using frequency domain analysis technology, so as to judge the aging degree of the insulator.

[0055] This frequency domain-based evaluation method can more accurately identify potential aging problems of insulators, helping power companies to replace or repair insulators with hidden dangers in a timely manner, ensuring the safe operation of transmission lines and avoiding transmission failures caused by insulator failure. At the same time, this method can also reduce unnecessary preventive maintenance, optimize resource allocation, and improve equipment efficiency.

[0056] like Figure 1 As shown, a method for evaluating the insulation aging state of a high-voltage dry-type bushing based on frequency domain characteristics provided by an embodiment of the present invention includes the following steps:

[0057] S101, by applying an alternating electric field to the insulating sample in a wide frequency range, the dielectric constant and dielectric loss of the insulating medium are measured to obtain the response characteristics of the insulating material at different frequencies. The specific steps are as follows:

[0058] Prepare aged dry casing samples and ensure that their surfaces are clean and free of damage;

[0059] Place the sample in a measurement fixture and connect its high and low voltage ends to a frequency response analyzer;

[0060] Set the analyzer's frequency sweep range, usually from low to high frequencies, to ensure that all important response areas of the insulation material are covered;

[0061] Start the measurement and record the data of dielectric constant and dielectric loss as a function of frequency.

[0062] During this process, special attention should be paid to the consistency of the aged core samples, the stability of the measurement environment, and the accuracy of the instrument calibration to avoid errors and interference.

[0063] S102, the aging state of the insulating material is evaluated by the changes of the dielectric complex capacitance, complex dielectric constant and dielectric loss factor with frequency under a low-voltage sinusoidal alternating electric field. The changes of these parameters are closely related to the molecular structure and electrical properties inside the insulating material, as follows:

[0064] During the evaluation process, a low-voltage sinusoidal alternating electric field is first applied to the insulating material and its response characteristics are measured over a wide frequency range. Subsequently, the complex capacitance C(ω) of the dielectric can be calculated using the obtained measurement data, where the real part C'(ω) represents the actual capacitance of the dielectric, while the imaginary part C"(ω) is related to the loss of the dielectric. At the same time, the real part ε'(ω) and the imaginary part ε"(ω) of the complex dielectric constant ε(ω) can also provide important information about the aging state of the material.

[0065] It is worth noting that in order to more comprehensively evaluate the aging state of insulating materials, the influence of dielectric loss factor also needs to be considered. Dielectric loss factor is defined as the ratio of the imaginary part to the real part of the complex capacitance or complex dielectric constant, which reflects the energy loss of the medium under the action of the electric field. During the evaluation process, special attention is paid to the influence of dielectric conductivity, and the corresponding dielectric loss expression is used to accurately calculate the dielectric loss.

[0066] It is worth noting that during the evaluation process, attention should be paid to the accuracy and reliability of the measured data, and high-precision measuring equipment and strict measuring procedures should be used to ensure the accuracy of the data. At the same time, the measured data should be analyzed and processed in detail to extract information related to the aging state of the insulation material.

[0067] The complex capacitance C*(ω) of the dielectric provided in the embodiment of the present invention is defined as shown in equations (1) to (3), wherein Z(ω) represents the input impedance of the dielectric; C'(ω) and C"(ω) represent the real part and the imaginary part of the complex capacitance, respectively, C'(ω) reflects the actual capacitance of the dielectric, and C"(ω) is related to the loss of the dielectric; ε'(ω) and ε"(ω) represent the real part and the imaginary part of the complex dielectric constant ε*(ω), respectively; A and w represent the area and distance of the test electrodes; generally, by measuring the voltage and current applied to the test sample, Z(ω) in equation (1) can be calculated, and then C*(ω) can be calculated;

[0068]

[0069] ε * (ω)=ε′(ω)-iε″(ω)(3)

[0070] The frequency domain dielectric response function F(ω) of the medium is its complex polarization rate χ*(ω), as shown in formula (4), where ε∞ represents the dielectric constant of the medium at high frequency; like the dielectric response function, the frequency domain dielectric response function is also an inherent property of the specimen and is closely related to the aging state of the specimen;

[0071]

[0072] The definition of dielectric loss provided in the embodiment of the present invention is as shown in formula (5), that is, the ratio of the imaginary part and the real part of the complex capacitance or complex dielectric constant

[0073]

[0074] Since the medium generally has conductivity, considering the influence of conductivity, the dielectric loss expression is shown in formula (6), where σ represents the conductivity of the medium;

[0075]

[0076] like Figure 2 As shown, a high-voltage dry-type bushing insulation aging state assessment system based on frequency domain characteristics provided by an embodiment of the present invention includes:

[0077] A response characteristic acquisition module is used to obtain the response characteristics of the insulating material at different frequencies by measuring the dielectric constant and dielectric loss of the insulating medium in a wide frequency range;

[0078] The evaluation module is used to evaluate the aging state of insulating materials by using the changes of dielectric complex capacitance, complex dielectric constant and dielectric loss factor with frequency under low-voltage sinusoidal alternating electric field.

[0079] Another object of the present invention is to provide a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method for evaluating the insulation aging state of a high-voltage dry-type bushing based on frequency domain characteristics.

[0080] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, which, when executed by a processor, enables the processor to execute the steps of the method for evaluating the insulation aging state of a high-voltage dry-type bushing based on frequency domain characteristics.

[0081] Another object of the present invention is to provide an information data processing terminal, which is used to implement the high-voltage dry-type bushing insulation aging status assessment system based on frequency domain characteristics.

[0082] Frequency domain dielectric spectroscopy is to evaluate the aging state of insulating materials by using the changes of complex capacitance, complex dielectric constant and dielectric loss factor of the medium with frequency under low voltage sinusoidal alternating electric field. FDS measurement is to extend the conventional power frequency complex capacitance and dielectric loss measurement to low frequency and high frequency bands (such as 0.1mHz to 1kHz). Its measurement principle is as follows Figure 3 shown.

[0083] The main parameters measured by FDS are dielectric loss tangent tanδ(ω) and complex capacitance C*(ω) of the medium. Dielectric loss tangent is defined as the active current I passing through the medium under sinusoidal voltage. R and reactive current I C Ratio.

[0084] The dielectric loss angle δ is the phase difference between the voltage V and the current I. Therefore, when the phase difference is known, In the case of , tanδ can also be calculated by formula (7):

[0085]

[0086] The complex capacitance C* of the dielectric is defined as shown in equations (8) and (9), where Z represents the input impedance of the dielectric; C′ and C″ represent the real and imaginary parts of the complex capacitance, respectively. C′ reflects the actual capacitance of the dielectric, while C″ is related to the loss of the dielectric.

[0087]

[0088] C * =C′-jC″ (9)

[0089] Only two of the three quantities tanδ, C′ and C″ need to be known to obtain the other parameter according to formula (10). For actual insulating media, by measuring parameters such as tanδ and C′ at different frequencies, tanδ-f and C*-f curves can be drawn to obtain the frequency domain dielectric properties of the insulation and complete the FDS measurement.

[0090]

[0091] The specific application field of the present invention covers the evaluation of the aging state of dry bushing insulation in high-voltage electrical equipment, and is particularly suitable for key components such as transformers and switchgear in power systems. By implementing the evaluation method based on frequency domain characteristics proposed in the present invention, the aging degree of dry bushing insulation materials can be accurately monitored and diagnosed, providing a scientific basis for the maintenance, overhaul and replacement of power equipment. The innovation of this technical solution lies in that it focuses on the analysis means of the frequency domain, deeply explores the relationship between frequency domain parameters and insulation aging state, overcomes the limitation of traditional methods that only rely on a single parameter criterion, and improves the accuracy and reliability of aging state evaluation. The technical value of the present invention is reflected in that it can achieve early warning, prevent equipment failures and power grid accidents caused by insulation aging, ensure the safe and stable operation of the power system, and reduce maintenance costs and extend the service life of equipment. Therefore, the present invention has significant technical advantages and application prospects in the field of high-voltage electrical equipment maintenance.

[0092] When the detection method proposed in the present invention is used to test the dry core at different aging days, the conclusions obtained are as follows:

[0093] The tanδ-f curve of epoxy resin under different aging days is as follows Figure 4As shown in the figure, it can be seen that the curve is "checkmark" in the whole frequency band under the double logarithmic coordinates: Overall, the spectrum curve of the rubber-impregnated paper casing is more sensitive to the change of aging degree. The tanδ spectrum curve changes inversely with the frequency in the low frequency band and in direct proportion to the frequency in the high frequency band; the change of aging degree basically does not change the overall change trend of the spectrum curve; the tanδ spectrum curve gradually moves toward the high frequency direction with the deepening of aging degree; the tanδ in the low frequency band increases with the deepening of aging degree, and the opposite is true in the high frequency band; the tanδ spectrum curves of different aging degrees will form an "intersection point", and the "intersection point" of this test result appears in 1~120Hz, and there is a minimum value in the intersection frequency band, that is, a weak local relaxation peak appears.

[0094] In the low-frequency band of the tanδ-f curve, the tanδ value decreases rapidly in a linear trend with the increase of the frequency of the electric field change, and an obvious low-frequency dispersion phenomenon occurs. Taking the unaged sample as an example, the slope of the tanδ-f curve in the low-frequency band (0.001-0.01Hz) in the logarithmic coordinate is k≈-1, and in the linear coordinate, tanδ∝w-1, which shows that the low-frequency band of the dry core is mainly caused by the conductivity loss. As the aging degree deepens, its tanδ value increases successively in the low-frequency band. This is because as the aging degree intensifies, the long-chain molecules inside the insulating material break and generate small molecular weight polar molecules. These small molecular polar molecules are more likely to produce polarization under the low-frequency electric field, thereby increasing the dielectric loss; at the same time, it also increases the number of carriers, resulting in an increase in the conductivity loss, which is the main contribution in the low-frequency band; when the frequency of the alternating electric field change is 0.01-0.1Hz, as the frequency increases, the contribution of the conductivity loss gradually decreases, while the contribution of the relaxation polarization loss becomes larger and larger. Therefore, the core FDS curves at each aging degree have minimum values, and the position of the minimum value gradually shifts to the left as the aging degree deepens, but after the low-frequency band, tanδ increases with the increase of frequency.

[0095] The curves of the real part of the complex capacitance of the dry bushing core changing with frequency under different aging degrees are as follows: Figure 5 shown.

[0096] Depend on Figure 5It can be obtained that the C' frequency domain spectrum is sensitive to the change of aging degree in the low frequency band, and changes with the frequency f at a slope close to zero in the high frequency band. As the aging degree deepens, the change of C' is also very small. This is because as the material ages, its internal microstructure and chemical composition change, resulting in changes in the storage and transmission characteristics of the charge in the material. However, in the low frequency band, the charge has enough time to move and redistribute in the material. Therefore, the change in material properties caused by aging has a more significant effect on the real part of the capacitance. Aging causes an increase in charge traps in the material, making it more difficult for the charge to move at low frequencies, thereby causing the real part of the capacitance to increase. In the frequency band of 5Hz to 5000Hz, the real part of the capacitance C' overlaps and approximates a horizontal straight line. This is mainly because aging mainly affects the long-term storage and slow movement characteristics of the charge in the material, but has little effect on the fast-moving charge. In this frequency band, the movement speed of the charge is relatively fast and is less affected by material aging. Therefore, in this frequency band, materials with different aging degrees exhibit similar real part characteristics of capacitance, that is, they overlap and approximate horizontal straight lines.

[0097] The aging degree of the core can be effectively determined by using the difference in tanδ-f (dielectric loss factor changes with frequency) and C'-f (capacitance real part changes with frequency) curves of the dry bushing core at different aging times. By analyzing the offset of tanδ and C' in a specific frequency band, especially the rising trend of C' in the low frequency band and the increase of tanδ, combined with the coincidence characteristics of the high frequency band curve, the aging state of the core can be quantitatively evaluated. This method is based on precise experimental data and provides a scientific basis for bushing maintenance and replacement.

[0098] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. It can be understood by a person of ordinary skill in the art that the above-mentioned devices and methods can be implemented using computer executable instructions and / or contained in a processor control code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0099] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for evaluating the insulation aging state of a high-voltage dry-type bushing based on frequency domain characteristics, characterized in that: The following steps are involved: Step 1, obtaining the response characteristics of the insulating material at different frequencies by measuring the dielectric constant and dielectric loss of the insulating medium in a wide frequency range; Step 2: Use the changes of dielectric complex capacitance, complex dielectric constant and dielectric loss factor with frequency under a low-voltage sinusoidal alternating electric field to evaluate the aging state of the insulating material.

2. The method for evaluating the insulation aging state of a high-voltage dry-type bushing based on frequency domain characteristics according to claim 1 is characterized in that: The step 1 specifically includes: (1) Prepare aged dry casing samples and ensure that their surfaces are clean and free of damage; (2) Place the sample in a measurement fixture and connect its high and low voltage ends to a frequency response analyzer; (3) Set the frequency scan range of the analyzer, usually from low frequency to high frequency, to ensure that all important response areas of the insulation material are covered; (4) Start the measurement and record the data of the change of dielectric constant and dielectric loss with frequency.

3. The method for evaluating the insulation aging state of a high-voltage dry-type bushing based on frequency domain characteristics according to claim 1 is characterized in that: The step 2 specifically includes: applying a low-voltage sinusoidal alternating electric field to the insulating material and measuring its response characteristics over a wide frequency range; then, using the obtained measurement data, calculating the complex capacitance C(ω) of the medium, wherein the real part C'(ω) represents the actual capacitance of the medium, and the imaginary part C"(ω) is related to the loss of the medium; at the same time, the real part ε'(ω) and the imaginary part ε"(ω) of the complex dielectric constant ε(ω) can also provide important information about the aging state of the material.

4. The method for evaluating the insulation aging state of a high-voltage dry-type bushing based on frequency domain characteristics according to claim 1 is characterized in that: The complex capacitance C*(ω) of the medium is defined as shown in equations (1) to (3), where Z(ω) represents the input impedance of the medium; C'(ω) and C"(ω) represent the real part and imaginary part of the complex capacitance respectively, C'(ω) reflects the actual capacitance of the medium, and C"(ω) is related to the loss of the medium; ε'(ω) and ε”(ω) represent the real and imaginary parts of the complex dielectric constant ε*(ω), respectively; A and w represent the area and distance of the test electrodes; generally, by measuring the voltage and current applied to the test sample, Z(ω) in formula (1) can be calculated, and then C*(ω) can be calculated; e * (ω)=ε′(ω)-iε″(ω)(3) The frequency domain dielectric response function F(ω) of the medium is its complex polarization rate χ*(ω), as shown in formula (4), where ε∞ represents the dielectric constant of the medium at high frequency; the frequency domain dielectric response function is an inherent property of the specimen and is closely related to the aging state of the specimen; 5. The method for evaluating the insulation aging state of a high-voltage dry-type bushing based on frequency domain characteristics according to claim 1, characterized in that: The dielectric loss is defined as follows: Since the medium generally has conductivity, considering the influence of conductivity, the dielectric loss expression is shown in formula (6), where σ represents the conductivity of the medium; 6. A high-voltage dry-type bushing insulation aging state assessment system based on frequency domain characteristics implementing the high-voltage dry-type bushing insulation aging state assessment method based on frequency domain characteristics as claimed in any one of claims 1 to 5, characterized in that: The high-voltage dry-type bushing insulation aging status assessment system based on frequency domain characteristics includes: A response characteristic acquisition module is used to obtain the response characteristics of the insulating material at different frequencies by measuring the dielectric constant and dielectric loss of the insulating medium in a wide frequency range; The evaluation module is used to evaluate the aging state of insulating materials by using the changes of dielectric complex capacitance, complex dielectric constant and dielectric loss factor with frequency under low-voltage sinusoidal alternating electric field.

7. A computer device, characterized in that: The computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the high-voltage dry-type bushing insulation aging status assessment method based on frequency domain characteristics as described in any one of claims 1-5.

8. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of the method for evaluating the insulation aging state of a high-voltage dry-type bushing based on frequency domain characteristics according to any one of claims 1 to 5.

9. An information data processing terminal, characterized in that: The information data processing terminal is used to implement the high-voltage dry-type bushing insulation aging status assessment system based on frequency domain characteristics as described in claim 6.

Images