Polymer insulating material degradation evaluation method, storage medium and computer equipment

Abstract

The invention discloses a polymer insulating material degradation evaluation method, a storage medium and computer equipment, and the method comprises the steps: obtaining an actual working condition of a to-be-evaluated polymer insulating material, determining a to-be-applied axial temperature gradient field based on a temperature change range, and determining a to-be-applied dynamic stress loading amount based on a stress change range; after simultaneously applying an axial temperature gradient field and a dynamic stress loading amount to the to-be-evaluated polymer insulating material, capturing an electrical tree image after the to-be-evaluated polymer insulating material is applied in real time; and based on the electrical tree image, calculating an accumulated damage value of the to-be-evaluated polymer insulating material, and taking the calculated accumulated damage value as an insulation degradation evaluation result of the polymer insulating material. The insulation deterioration degree of the polymer insulation material is represented by applying a multi-coupling scene of heat and mechanical stress and constructing an accumulated damage index based on the electric tree, and the deterioration degree evaluation precision is improved.

Description

Technical Field

[0001] This application relates to the technical field of high-voltage equipment detection, and particularly to a method for evaluating the degradation of polymer insulation materials, a storage medium, and a computer device. Background Art

[0002] In the fields of high-voltage power transmission and transformation equipment and power electronic devices, polymer insulation materials, as the core protective layer of key components, undertake multiple functions such as electrical isolation, mechanical support, and environmental protection. With the increasing demand for equipment compactness and large capacity in the new power system, the use proportion of polymers such as epoxy resin in equipment such as high-voltage cables and GIS insulators has increased significantly. However, under complex working conditions, the insulation materials are long-term subjected to thermal stress caused by temperature gradients, as well as dynamic loads generated by equipment vibration and mechanical deformation. The coupling effect of the two stress fields accelerates the irreversible damage of the material microstructure, resulting in the progressive degradation of insulation performance. According to statistics, about 65% of power accidents caused by insulation failure are closely related to the aging of insulation materials under the combined action of multiple physical fields.

[0003] Electrical tree is the main form of insulation material degradation. Traditional evaluation methods are mostly based on single-stress accelerated aging tests, and the degradation degree is characterized by measuring parameters such as the cumulative damage of electrical trees, with low accuracy. Summary of the Invention

[0004] In view of this, this application provides a method for evaluating the degradation of polymer insulation materials, a storage medium, and a computer device. By applying a multi-coupling scenario of heat and mechanical stress and constructing a cumulative damage index based on electrical trees, the insulation degradation degree of polymer insulation materials is characterized, and the accuracy of degradation degree evaluation is improved.

[0005] According to one aspect of this application, a method for evaluating the degradation of polymer insulation materials is provided. The method includes:

[0006] Obtain the actual working conditions of the polymer insulation material to be evaluated, where the actual working conditions include the temperature change range and stress change range suffered by the polymer insulation material to be evaluated during actual operation.

[0007] Based on the temperature change range, determine the axial temperature gradient field to be applied, and based on the stress change range, determine the dynamic stress loading amount to be applied.

[0008] After simultaneously applying the axial temperature gradient field and the dynamic stress loading amount to the polymer insulation material to be evaluated, capture the electrical tree image of the polymer insulation material to be evaluated in real time.

[0009] Based on the electrical tree image, calculate the cumulative damage value of the polymer insulating material to be evaluated, and use the calculated cumulative damage value as the evaluation result of the insulation deterioration of the polymer insulating material.

[0010] Optionally, the simultaneous application of the axial temperature gradient field and the dynamic stress loading amount to the insulating material to be evaluated includes:

[0011] Place the polymer insulating material to be evaluated in a mechanical stress and temperature gradient environment simulation device, and simultaneously apply the axial temperature gradient field and the dynamic stress loading amount to the insulating material to be evaluated based on the mechanical stress and temperature gradient environment simulation device. Among them, the mechanical stress and temperature gradient environment simulation device includes an electromechanical loading module and a thermal field regulation system. The electromechanical loading module realizes the dynamic stress loading of the dynamic stress loading amount through the closed-loop control of a push-pull force testing machine and a push-pull force gauge. The thermal field regulation system constructs the axial temperature gradient field to be applied by integrating temperature control heating sheets on the high-voltage electrode side and the grounding end respectively and using thermocouples to monitor the temperature distribution in real time.

[0012] Optionally, the dynamic stress loading range of the electromechanical loading module is 0 - 30 MPa, and the stress resolution of the electromechanical loading module is 0.1 MPa.

[0013] Optionally, the accuracy of the thermal field regulation system is ±0.5 °C.

[0014] Optionally, the real-time capture of the electrical tree image of the polymer insulating material to be evaluated includes:

[0015] Real-time capture of the electrical tree image of the polymer insulating material to be evaluated through an electrical tree observation system. Among them, the electrical tree observation system includes a cold light source, an optical microscope and a computer. The optical microscope includes an objective lens, an eyepiece and a high-resolution imaging device (CCD, Charge-Coupled Device). The electrical tree observation system transmits the electrical tree image to the computer through a data cable, and the electrical tree image is used to record the growth process of the electrical tree of the polymer insulating material to be evaluated in real time.

[0016] Optionally, the calculation of the cumulative damage value of the polymer insulating material to be evaluated based on the electrical tree image includes:

[0017] After removing the tip part in the electrical tree image, perform binarization processing on the electrical tree image after removing the tip part to obtain a target electrical tree image;

[0018] In the target electrical tree image, calculate the sum of the pixel values covered by the electrical tree to obtain the cumulative damage value of the polymer insulating material to be evaluated.

[0019] Optionally, performing binarization processing on the electrical tree image after removing the tip portion to obtain a target electrical tree image, including:

[0020] In the electrical tree image after removing the tip portion, determining the optimal gray threshold based on the maximum inter-class variance algorithm;

[0021] Based on the determined optimal gray threshold, performing binarization processing on the electrical tree image after removing the tip portion to obtain a target electrical tree image.

[0022] Optionally, the maximum heating amount provided by the to-be-applied axial temperature gradient field is less than the preset maximum tolerable heating amount corresponding to the to-be-evaluated polymer insulating material, and the to-be-applied dynamic stress loading amount is less than the preset maximum tolerable tensile stress corresponding to the to-be-evaluated polymer insulating material.

[0023] According to another aspect of the present application, there is provided a storage medium on which a computer program is stored, and when the program is executed by a processor, the above-mentioned polymer insulating material degradation evaluation method is implemented.

[0024] According to still another aspect of the present application, there is provided a computer device, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor. When the processor executes the program, the above-mentioned polymer insulating material degradation evaluation method is implemented.

[0025] By means of the above technical solutions, a polymer insulating material degradation evaluation method, a storage medium, and a computer device provided by the present application obtain the actual working conditions of the to-be-evaluated polymer insulating material, determine the to-be-applied axial temperature gradient field based on the temperature change range, and determine the to-be-applied dynamic stress loading amount based on the stress change range; after simultaneously applying the axial temperature gradient field and the dynamic stress loading amount to the to-be-evaluated polymer insulating material, capturing the electrical tree image of the to-be-evaluated polymer insulating material in real time; calculating the cumulative damage value of the to-be-evaluated polymer insulating material based on the electrical tree image, and using the calculated cumulative damage value as the insulation degradation evaluation result of the polymer insulating material. By applying a multi-coupling scenario of heat and mechanical stress and constructing a cumulative damage index based on electrical trees, the insulation degradation degree of the polymer insulating material is characterized, and the accuracy of the degradation degree evaluation is improved.

[0026] The above description is only an overview of the technical solutions of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features, and advantages of the present application more obvious and understandable, the specific embodiments of the present application are specifically described below. Description of the Drawings

[0027] The accompanying drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0028] Figure 1 A schematic flowchart of a method for evaluating the degradation of a polymer insulating material provided by an embodiment of the present application is shown;

[0029] Figure 2 A schematic flowchart of another method for evaluating the degradation of a polymer insulating material provided by an embodiment of the present application is shown;

[0030] Figure 3 A schematic diagram of a mechanical stress and temperature gradient environment simulation device provided by an embodiment of the present application is shown;

[0031] Figure 4 (a) shows an electrical tree image including an original electrical tree provided by an embodiment of the present application;

[0032] Figure 4 (b) shows a target electrical tree image including a processed electrical tree provided by an embodiment of the present application. Detailed implementation manners

[0033] The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0034] In this embodiment, a method for evaluating the degradation of a polymer insulating material is provided. As Figure 1 shown, the method includes:

[0035] Step 101, obtaining the actual working conditions of the polymer insulating material to be evaluated, where the actual working conditions include the temperature change range and stress change range suffered by the polymer insulating material to be evaluated during actual operation;

[0036] Step 102, determining the axial temperature gradient field to be applied based on the temperature change range, and determining the dynamic stress loading amount to be applied based on the stress change range.

[0037] The generation of electrical trees is a complex electro-thermal-chemical process, involving various factors such as electric field distribution, material defects, and partial discharge. When there are defects such as impurities and bubbles in the polymer insulating material, these defects will cause local electric field concentration, thereby triggering partial discharge. As the discharge continues, tiny cracks will form inside the material, and these cracks gradually expand and connect with each other, eventually forming a dendritic discharge damage channel.

[0038] The influencing factors for the generation of electrical tree are as follows:

[0039] 1. Voltage: The level of voltage directly affects the initiation and growth rate of electrical tree. Generally speaking, the higher the voltage, the faster the initiation and growth rate of electrical tree.

[0040] 2. Temperature: Temperature also has a significant impact on the growth of electrical tree. Within a certain range, as the temperature increases, the growth rate of electrical tree will accelerate. However, when the temperature is too high, it may damage the properties of the material, thus affecting the growth of electrical tree.

[0041] 3. Material defects: Defects such as impurities and air bubbles in the material are the main causes for the initiation of electrical tree. These defects will lead to local electric field concentration, thus triggering partial discharge and crack propagation.

[0042] 4. Voltage rising speed and voltage application method: Changes in the voltage rising speed and voltage application method also have a great impact on the growth characteristics and morphology of electrical tree. The faster the voltage rising speed, the more conducive it is to the initiation and growth of electrical tree.

[0043] Electrical tree is one of the main forms of aging and damage of polymer insulation materials, posing a serious threat to the insulation performance and service life of equipment. When the electrical tree expands to a certain extent, it will cause insulation breakdown, triggering equipment failures or accidents. In addition, electrical tree will also reduce the electrical strength of the material, increasing the operation risk of the equipment.

[0044] In order to inhibit the growth of electrical tree in polymer insulation materials, the following measures can be taken:

[0045] 1. Improve material properties: By improving the manufacturing process and formula of the material, enhance the electrical strength and heat resistance of the material, thus reducing the generation of defects and the concentration of local electric field.

[0046] 2. Strengthen electric field shielding: In equipment design, adopt electric field shielding technology to reduce the direct action of the electric field on the insulation material, thus reducing the initiation probability of electrical tree.

[0047] 3. Control the operating environment: Control the operating environment of the equipment, such as temperature, humidity, etc., to reduce the influence of the external environment on the insulation material.

[0048] 4. Regular inspection and maintenance: Regularly conduct insulation performance inspection and maintenance on the equipment, and promptly detect and handle potential electrical tree problems.

[0049] In summary, the electrical tree in polymer insulation materials is a serious insulation aging and damage phenomenon, posing a threat to the safe operation and service life of equipment. Therefore, effective measures need to be taken to inhibit the growth of electrical tree to ensure the insulation performance and safe operation of the equipment.

[0050] In the above embodiments of the present application, a cumulative damage index based on electrical treeing can be constructed to characterize the insulation deterioration degree of polymer insulating materials. Specifically, the actual working conditions of the polymer insulating material to be evaluated are obtained, so as to determine the axial temperature gradient field to be applied and the dynamic stress loading amount according to the actual working conditions. The actual working conditions refer to various conditions and requirements faced by the material in the specific application environment, and these conditions may include multiple factors such as temperature, pressure, electric field strength, humidity, chemical substance erosion, etc., which jointly determine the performance and lifespan of the polymer insulating material during operation.

[0051] Specifically, after obtaining the actual working conditions, the environmental conditions of the polymer insulating material in the specific application can be understood in detail. For example:

[0052] Operating temperature range: Understand the performance of the material at high and low temperatures, as well as the influence of temperature fluctuations on the material performance.

[0053] Electric field strength: Determine the voltage level and electric field distribution that the material withstands during operation to evaluate its insulation performance.

[0054] Mechanical stress: Analyze the stress distribution and deformation of the material when subjected to mechanical actions such as pressure, tension, and bending.

[0055] Humidity and chemical substances: Consider the influence of humidity changes and corrosive chemical substances on the material performance.

[0056] Then, based on the actual working condition conditions, a mathematical model describing the performance of the polymer insulating material can be established. These models can include:

[0057] Heat conduction equation: Used to describe the heat transfer process inside the material, so as to determine the axial temperature gradient field.

[0058] Mechanical equation: Used to describe the deformation and stress distribution of the material under mechanical stress, so as to determine the dynamic stress loading amount.

[0059] Using the established mathematical model, simulation analysis can be carried out to predict the performance of the polymer insulating material under actual working conditions. For example:

[0060] Temperature field simulation: By solving the heat conduction equation, the temperature distribution and axial temperature gradient inside the material are obtained.

[0061] Stress field simulation: By solving the mechanical equation, the stress distribution and dynamic stress loading amount of the material under mechanical stress are obtained.

[0062] Therefore, determining the axial temperature gradient field and dynamic stress loading of polymer insulation materials according to the actual working conditions is a complex process that requires comprehensive consideration of various factors and conditions. Through detailed working condition analysis, establishing a mathematical model, conducting simulation analysis, and experimental verification and optimization, the accuracy and reliability of the obtained results can be ensured.

[0063] Step 102: After applying the axial temperature gradient field and the dynamic stress loading to the polymer insulation material to be evaluated, capture the electrical tree image of the polymer insulation material to be evaluated in real time.

[0064] Next, after applying the axial temperature gradient field and the dynamic stress loading to the polymer insulation material to be evaluated, capture the electrical tree image of the polymer insulation material to be evaluated after being applied in real time to prepare for subsequent insulation degradation evaluation.

[0065] Step 103: Based on the electrical tree image, calculate the cumulative damage value of the polymer insulation material to be evaluated, and use the calculated cumulative damage value as the insulation degradation evaluation result of the polymer insulation material.

[0066] Then, based on the electrical tree image, calculate the cumulative damage value of the polymer insulation material to be evaluated, and use the calculated cumulative damage value as the insulation degradation evaluation result of the polymer insulation material.

[0067] Electrical tree is the main form of insulation material degradation. Traditional evaluation methods are mostly based on single-stress accelerated aging tests, and the degradation degree is characterized by measuring parameters such as the cumulative damage of electrical trees. However, in actual operation, the thermo-mechanical coupling effect has significant synergistic amplification characteristics: temperature fluctuations not only change the viscoelasticity of polymers but also cause interfacial shear stress due to differences in thermal expansion coefficients; mechanical vibrations promote molecular chain breakage through strain energy accumulation and at the same time exacerbate the micro-discharge activity inside the dielectric. Research shows that under the combined stress, the breakdown strength of the material decreases at a rate that can reach 2-3 times that of a single factor, and the degradation path shows non-linear characteristics. Currently, single-factor aging models are difficult to accurately evaluate this multi-field coupling damage mechanism, resulting in a prediction error of the remaining life of the equipment exceeding 40%.

[0068] By applying the technical solution of this embodiment, by constructing a polymer insulation degradation evaluation method under the combined action of thermal stress and mechanical stress, the evaluation accuracy can be improved, and by capturing the development trajectory of electrical trees in real time, the degradation process of the material can be dynamically observed, while traditional methods lack real-time performance. At the same time, constructing a cumulative damage index further provides a more accurate damage quantification analysis.

[0069] Furthermore, as a refinement and extension of the specific implementation manner of the above embodiment, in order to fully illustrate the specific implementation process of this embodiment, another polymer insulation material degradation evaluation method is provided, as Figure 2As shown, the method includes:

[0070] Step 201, obtaining the actual working conditions of the polymer insulating material to be evaluated, determining the axial temperature gradient field to be applied based on the temperature change range, and determining the dynamic stress loading amount to be applied based on the stress change range, where the actual working conditions include the temperature change range and stress change range that the polymer insulating material to be evaluated is subjected to during actual operation, the maximum heating amount provided by the axial temperature gradient field to be applied is less than the preset maximum tolerable heating amount corresponding to the polymer insulating material to be evaluated, and the dynamic stress loading amount to be applied is less than the preset maximum tolerable tensile stress corresponding to the polymer insulating material to be evaluated.

[0071] In the above embodiments of the present application, obtaining the actual working conditions of the polymer insulating material to be evaluated, determining the axial temperature gradient field to be applied, and the dynamic stress loading amount to be applied. In particular, the maximum heating amount provided by the axial temperature gradient field to be applied is less than the preset maximum tolerable heating amount corresponding to the polymer insulating material to be evaluated, and the dynamic stress loading amount to be applied is less than the preset maximum tolerable tensile stress corresponding to the polymer insulating material to be evaluated, which is used to ensure that the polymer insulating material to be evaluated will not be completely damaged and affect the evaluation results.

[0072] Specifically, regarding the determination of the preset maximum tolerable heating amount, thermal analysis techniques such as thermogravimetric analysis (TGA) or differential scanning calorimetry (DSC) can be used to measure the mass loss or thermal effect change of the polymer insulating material during heating, so as to determine its thermal stability and the maximum tolerable heating amount, and then evaluate whether the determined axial temperature gradient field and dynamic stress loading amount are appropriate. These tests can be carried out in an environment with controlled temperature to simulate the thermal behavior of the material at different temperatures. In particular, the ability of the material to resist breakdown at a specific voltage can also be measured, which is also an important aspect of evaluating its thermal stability. By gradually increasing the voltage until the material breaks down, the breakdown voltage and the corresponding temperature can be recorded, thereby indirectly evaluating the preset maximum tolerable heating amount of the material.

[0073] Next, regarding the determination of the preset maximum tolerable tensile stress, a tensile test can be performed on the polymer insulating material to measure its tensile strength (i.e., the maximum tensile stress that can be tolerated before fracture). During the test, the sample is clamped between two relatively moving fixtures, and the tensile force is gradually increased until the sample breaks. By recording the maximum tensile force before fracture and the cross-sectional area of the sample, the tensile strength (tensile stress per unit area) can be calculated. The stress-strain curve obtained from the tensile test can also be further analyzed to obtain mechanical property parameters such as the elastic modulus and yield strength of the material. These parameters help to more comprehensively understand the tensile properties of the material and its maximum tolerable tensile stress.

[0074] Therefore, based on the preset maximum heat tolerance determined by the thermal stability test, a series of heating experiments with different temperature gradients can be designed. By gradually increasing the temperature gradient, observe the thermal behavior changes of the material at different temperature gradients to determine the appropriate axial temperature gradient field. In particular, when determining the axial temperature gradient field, physical properties such as the thermal expansion coefficient and thermal conductivity of the material, as well as the temperature environment in actual applications, also need to be considered. Ensure that the designed temperature gradient field can simulate the temperature distribution in the actual working conditions without causing excessive thermal stress or thermal damage to the material.

[0075] Similarly, based on the preset maximum tensile stress determined by the tensile test, a series of experiments with different dynamic stress loading amounts can be designed. By gradually increasing the dynamic stress loading amount, observe the mechanical response and damage of the material at different stress levels. When determining the dynamic stress loading amount, parameters such as the waveform of the stress (such as sine wave, square wave, etc.), frequency, and duration need to be considered. The selection of these parameters should be able to simulate the dynamic mechanical stress environment in actual operation and ensure the accuracy and reliability of the experimental results.

[0076] That is, through the thermal stability test, tensile test, and analysis of the stress-strain curve, the preset maximum heat tolerance and preset maximum tensile stress of the polymer insulation material to be evaluated can be obtained. Furthermore, based on these test results, the characteristics of the material, and the actual application requirements, an appropriate axial temperature gradient field and dynamic stress loading amount can be determined for experiments and evaluations.

[0077] Step 202: Place the polymer insulation material to be evaluated in a mechanical stress and temperature gradient environment simulation device, and simultaneously apply the axial temperature gradient field and the dynamic stress loading amount to the insulation material to be evaluated based on the mechanical stress and temperature gradient environment simulation device. Among them, the mechanical stress and temperature gradient environment simulation device includes an electromechanical loading module and a thermal field control system. The electromechanical loading module realizes the dynamic stress loading of the dynamic stress loading amount through the closed-loop control of a push-pull force testing machine and a push-pull force gauge. The thermal field control system constructs the axial temperature gradient field to be applied by integrating temperature control heating sheets on the high-voltage electrode side and the grounding end respectively and using thermocouples to monitor the temperature distribution in real time. The dynamic stress loading range of the electromechanical loading module is 0 - 30 MPa, the stress resolution of the electromechanical loading module is 0.1 MPa, and the accuracy of the thermal field control system is ±0.5 °C.

[0078] Then, the mechanical stress and temperature gradient environment simulation device can be used to simultaneously apply the axial temperature gradient field and the dynamic stress loading amount to the insulation material to be evaluated. The mechanical stress and temperature gradient environment simulation device is shown, for example Figure 3 as Figure 3Specifically, it includes a fixed side, a fixed fixture, a movable fixture, a high-voltage electrode, a sensor, a heating sheet, a ground electrode (i.e., the grounding terminal), and a push-pull force gauge. The polymer insulation material to be evaluated is placed between the fixed fixture and the movable fixture. A push-pull force testing machine can be added on the right side of the push-pull force gauge for dynamic stress loading to achieve dynamic stress loading of the dynamic stress loading amount through closed-loop control. The sensor and the heating sheet together form a temperature-controlled heating sheet to monitor the temperature distribution in real time through a thermocouple and construct an axial temperature gradient field to be applied. During the process of dynamic stress loading of the dynamic stress loading amount based on the closed-loop control of the push-pull force testing machine and the push-pull force gauge, compressive stress and tensile stress are generated.

[0079] In particular, the stress includes compressive force and tensile force. Correspondingly, the dynamic stress loading amount includes the dynamic compressive force loading amount and the dynamic tensile force loading amount. At the same time, after applying tensile or compressive force to the polymer insulation material to be evaluated, the change of the electrical tree is irreversible. Therefore, when applying the axial temperature gradient field and the dynamic stress loading amount to the insulation material to be evaluated based on the mechanical stress and temperature gradient environment simulation device, specifically:

[0080] The polymer insulation material to be evaluated can be divided into two parts and placed in the mechanical stress and temperature gradient environment simulation device in two separate times. For the first time, the axial temperature gradient field and the dynamic compressive force loading amount can be applied to the first part of the polymer insulation material to be evaluated, and the first electrical tree image is captured at this time. For the second time, the axial temperature gradient field and the dynamic tensile force loading amount can be applied to the second part of the polymer insulation material to be evaluated, and the second electrical tree image is captured at the same time. Correspondingly, for each electrical tree image (the first electrical tree image and the second electrical tree image), the cumulative damage value is calculated separately once. Finally, the cumulative damage values calculated separately twice are jointly used as the insulation degradation evaluation result.

[0081] Step 203: The electrical tree image of the polymer insulation material to be evaluated is captured in real time through the electrical tree observation system. The electrical tree observation system includes a cold light source, an optical microscope, and a computer. The optical microscope includes an objective lens, an eyepiece, and a high-resolution imaging device (CCD, Charge-Coupled Device). The electrical tree observation system transmits the electrical tree image to the computer through a data cable. The electrical tree image is used to record the growth process of the electrical tree of the polymer insulation material to be evaluated in real time.

[0082] Next, an electric tree image of the polymer insulating material to be evaluated is captured in real time through an electric tree observation system. The full English name of the high-resolution imaging device (CCD) is Charge-Coupled Device, which means charge-coupled device in Chinese. It was invented by Willard Boyle and George E. Smith of Bell Labs in 1969. It is a semiconductor device that can convert light into charge and store and read it out. It is also one of the most commonly used image sensors in digital imaging devices. The obtained electric tree image, for example Figure 4 (as shown in (a)) Figure 4 (a) contains the original electric tree.

[0083] Step 204: After removing the tip part of the electric tree image, in the electric tree image with the tip part removed, determine the optimal gray threshold based on the maximum inter-class variance algorithm.

[0084] Step 205: Based on the determined optimal gray threshold, perform binary processing on the electric tree image with the tip part removed to obtain the target electric tree image.

[0085] Next, after removing the tip part of the electric tree image, in the electric tree image with the tip part removed, determine the optimal gray threshold based on the maximum inter-class variance algorithm. Based on the determined optimal gray threshold, perform binary processing on the electric tree image with the tip part removed to obtain the target electric tree image, for example Figure 4 (as shown in (b)) Figure 4 (b) contains the processed electric tree. Therefore, by selecting an appropriate gray threshold, the problem of electric tree distortion can be avoided.

[0086] Step 206: In the target electric tree image, calculate the sum of the pixel values covered by the electric tree to obtain the cumulative damage value of the polymer insulating material to be evaluated, and use the calculated cumulative damage value as the insulation degradation evaluation result of the polymer insulating material.

[0087] Next, in the target electric tree image, calculate the sum of the pixel values covered by the electric tree, that is, the sum of the pixel values of the white part, to obtain the cumulative damage value of the polymer insulating material to be evaluated, and directly use the calculated cumulative damage value as the insulation degradation evaluation result of the polymer insulating material.

[0088] In particular, a sample can also be prepared using a mixed system of bisphenol A epoxy resin and polyamide. Then, artificial defects are constructed to conform to the actual defect distribution characteristics to test the accuracy of the evaluation results. As a key material for electrical equipment insulation, epoxy resin is subjected to mechanical stress during long-term operation. For example, as the main material for support insulators in the power system, epoxy resin bears compressive stress and tensile stress. At the same time, the epoxy resin insulation bears thermal expansion stress caused by conductor heating. The stress concentration during the operation of horizontally laid 110 kV GIS pot insulators is the main threat to the mechanical reliability of the insulators, and the edges of the insulators and the interfaces between the insulators and conductors are weak areas. As a key component of the circuit breaker of gas-insulated switchgear (GIS), the insulating rod is subjected to pushing and pulling forces during opening and closing operations, causing the epoxy resin used in the insulating rod to bear tensile or compressive stress. Under the action of tensile and compressive stresses, the physical microstructure of epoxy resin insulation changes, thereby affecting its electrical properties. In the glassy state, the free volume and electron mean free path of epoxy resin polymers decrease with the increase of compressive stress, resulting in a decrease in its dielectric constant and dielectric loss. Mechanical stress affects the arrangement order of molecular chains, and the arrangement structure of the molecular chains of epoxy resin after curing changes under the action of stress. When the epoxy resin insulation is subjected to large mechanical stress, its cross-linked structure will be damaged or even broken, thereby affecting its insulation performance. As the tensile stress increases, the dielectric strength of epoxy resin continuously decreases; as the bending stress increases, the dielectric strength of epoxy resin first increases and then decreases.

[0089] In actual operation, the insulation of epoxy resin electrical equipment is subjected to temperature gradient effects. The Joule heat generated by the current in the conductor causes the temperature of the inner layer of the insulation to rise, while the outer layer of the insulation is at the ambient temperature. Therefore, during the operation of the power system, there is a continuously distributed temperature gradient inside the epoxy resin insulation. Currently, the operating temperature of epoxy resin cable terminals is 50 - 60 °C, and it can reach up to 150 °C during faults, forming a large temperature gradient in the insulating material. Therefore, the epoxy resin insulation is simultaneously subjected to the combined action of mechanical stress and temperature gradient, making the insulation degradation process of epoxy components more complex.

[0090] Regarding the process of preparing the sample, it can include the following steps:

[0091] 1. Raw material preparation: Weigh the bisphenol A epoxy resin matrix and polyamide curing agent, and place them in a clean mixing container according to a mass ratio of 3:1. Use a digital balance to control the mixing ratio error within the range of ±0.05 g.

[0092] 2. Homogenization treatment: Transfer the mixed system to a magnetic stirring device and perform mechanical stirring at 60 revolutions per minute for 15 minutes to ensure full mutual solubility.

[0093] 3. Degassing treatment: Transfer the mixed solution into a vacuum drying oven and continuously conduct degassing treatment for 30 minutes under the conditions of a negative pressure of -0.1 MPa and a constant temperature of 30 °C to eliminate internal microbubbles.

[0094] 4. Mold forming: Adopt a special mold system processed by numerical control. Among them, the tensile specimens are processed according to the ASTM D638-IV standard, and the compression specimens adopt a prismatic structure in accordance with ISO 604 specifications. A needle electrode with a preset tip radius of 3 μm is arranged in the mold to ensure that the needle-plate spacing is controlled within 2.0 ± 0.2 mm.

[0095] 5. Initial stage curing: Place the specimens in a constant temperature curing box at 25 ± 1 °C and keep them for 48 hours.

[0096] 6. Post-curing treatment: Transfer to a precision temperature control box at 60 ± 0.5 °C for 8 hours of secondary curing to improve the structural stability of the material.

[0097] 7. Electrode treatment: After the specimens are demolded, paste a 100-μm copper conductive layer at the grounding end to ensure that the contact resistance is less than 0.1 Ω.

[0098] Thus, specimens are obtained for testing and evaluating the accuracy of the results.

[0099] By applying the technical solution of this embodiment, through the collaborative loading of multiple fields of mechanics, electricity, and heat, the evaluation accuracy of the polymer insulation performance can be improved.

[0100] Based on the above as Figures 1 to 2 shown in the method, correspondingly, the embodiment of the present application also provides a storage medium, on which a computer program is stored. When the computer program is executed by a processor, the polymer insulation material degradation evaluation method as Figures 1 to 2 shown above is implemented.

[0101] Based on such an understanding, the technical solution of the present application can be embodied in the form of a software product. The software product can be stored in a non-volatile storage medium (which can be a CD-ROM, USB flash drive, mobile hard disk, etc.), including several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute the methods described in various implementation scenarios of the present application.

[0102] Based on the above as Figures 1 to 2 shown in the method, in order to achieve the above object, the embodiment of the present application also provides a computer device, which can specifically be a personal computer, server, network device, etc. The computer device includes a storage medium and a processor; the storage medium is used to store a computer program; the processor is used to execute the computer program to implement the polymer insulation material degradation evaluation method as Figures 1 to 2 shown above.

[0103] Optionally, the computer device may further include a user interface, a network interface, a camera, a Radio Frequency (RF) circuit, sensors, an audio circuit, a WI-FI module, and so on. The user interface may include a display screen (Display), an input unit such as a keyboard (Keyboard), etc. Optionally, the user interface may further include a USB interface, a card reader interface, etc. The network interface may optionally include a standard wired interface, a wireless interface (such as a Bluetooth interface, a WI-FI interface), etc.

[0104] Those skilled in the art can understand that the structure of a computer device provided in this embodiment does not constitute a limitation on the computer device, and it may include more or fewer components, or combine certain components, or have different component arrangements.

[0105] The storage medium may further include an operating system and a network communication module. The operating system is a program for managing and storing the hardware and software resources of the computer device, and supports the operation of information processing programs and other software and / or programs. The network communication module is used to implement communication between components inside the storage medium, as well as communication between other hardware and software in the entity device.

[0106] Through the description of the above embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus a necessary general hardware platform, or can also obtain the actual working conditions of the polymer insulation material to be evaluated through hardware. Based on the temperature change range, determine the axial temperature gradient field to be applied, and based on the stress change range, determine the dynamic stress loading amount to be applied; after applying the axial temperature gradient field and the dynamic stress loading amount to the polymer insulation material to be evaluated simultaneously, capture the electrical tree image of the polymer insulation material to be evaluated in real time; based on the electrical tree image, calculate the cumulative damage value of the polymer insulation material to be evaluated, and use the calculated cumulative damage value as the insulation degradation evaluation result of the polymer insulation material. By applying a multi-coupled scenario of heat and mechanical stress, and constructing a cumulative damage index based on electrical trees, the insulation degradation degree of the polymer insulation material is characterized, and the evaluation accuracy of the degradation degree is improved.

[0107] Those skilled in the art can understand that the drawings are only schematic diagrams of a preferred implementation scenario, and the modules or processes in the drawings are not necessarily essential for implementing this application. The modules in the above implementation scenario can be combined into one module, or further split into multiple sub-modules.

[0108] The above serial numbers of this application are only for description and do not represent the advantages or disadvantages of the implementation scenarios. The above disclosure is only several specific implementation scenarios of this application. However, this application is not limited thereto, and any changes that can be made by those skilled in the art should fall within the protection scope of this application.

Claims

1. A method for evaluating the deterioration of a polymer insulating material, characterized in that, The method includes: Obtaining the actual working conditions of the polymer insulating material to be evaluated, where the actual working conditions include the temperature change range and stress change range that the polymer insulating material to be evaluated is subjected to during actual operation. Based on the temperature change range, determining the axial temperature gradient field to be applied, and based on the stress change range, determining the dynamic stress loading amount to be applied. After simultaneously applying the axial temperature gradient field and the dynamic stress loading amount to the polymer insulating material to be evaluated, capturing the electrical tree image of the polymer insulating material to be evaluated in real time. Based on the electrical tree image, calculating the cumulative damage value of the polymer insulating material to be evaluated, and using the calculated cumulative damage value as the insulation degradation evaluation result of the polymer insulating material.

2. The method according to claim 1, wherein The simultaneously applying the axial temperature gradient field and the dynamic stress loading amount to the polymer insulating material to be evaluated includes: Placing the polymer insulating material to be evaluated in a mechanical stress and temperature gradient environment simulation device, and simultaneously applying the axial temperature gradient field and the dynamic stress loading amount to the polymer insulating material to be evaluated based on the mechanical stress and temperature gradient environment simulation device. The mechanical stress and temperature gradient environment simulation device includes an electromechanical loading module and a thermal field regulation system. The electromechanical loading module realizes the dynamic stress loading of the dynamic stress loading amount through the closed-loop control of a push-pull testing machine and a push-pull gauge. The thermal field regulation system constructs the axial temperature gradient field to be applied by integrating temperature control heating sheets on the high-voltage electrode side and the grounding end respectively and using thermocouples to monitor the temperature distribution in real time.

3. The method according to claim 2, wherein The dynamic stress loading range of the electromechanical loading module is 0 - 30 MPa, and the stress resolution of the electromechanical loading module is 0.1 MPa.

4. The method according to claim 2, characterized in that, The accuracy of the thermal field regulation system is ±0.5 °C.

5. The method according to claim 1, characterized in that, The capturing the electrical tree image of the polymer insulating material to be evaluated in real time includes: Capturing the electrical tree image of the polymer insulating material to be evaluated in real time through an electrical tree observation system. The electrical tree observation system includes a cold light source, an optical microscope, and a computer. The optical microscope includes an objective lens, an eyepiece, and a high-resolution imaging device (CCD, Charge-Coupled Device). The electrical tree observation system transmits the electrical tree image to the computer through a data line, and the electrical tree image is used to record the growth process of the electrical tree of the polymer insulating material to be evaluated in real time.

6. The method according to claim 1, wherein The calculating the cumulative damage value of the polymer insulating material to be evaluated based on the electrical tree image includes: After removing the tip part from the electrical tree image, performing binarization processing on the electrical tree image after removing the tip part to obtain a target electrical tree image. In the target electrical tree image, calculating the sum of the pixel values covered by the electrical tree to obtain the cumulative damage value of the polymer insulating material to be evaluated.

7. The method according to claim 6, wherein The performing binarization processing on the electrical tree image after removing the tip part to obtain a target electrical tree image includes: In the electrical tree image after removing the tip part, determining the optimal gray threshold based on the maximum inter-class variance algorithm. Based on the determined optimal gray threshold, performing binarization processing on the electrical tree image after removing the tip part to obtain a target electrical tree image.

8. The method according to claim 1, wherein The maximum heating amount provided by the axial temperature gradient field to be applied is less than the preset maximum tolerable heating amount corresponding to the polymer insulation material to be evaluated, and the dynamic stress loading amount to be applied is less than the preset maximum tolerable tensile stress corresponding to the polymer insulation material to be evaluated.

9. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method for evaluating the deterioration of the polymer insulation material according to any one of claims 1 to 7.

10. A computer device, comprising a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method for evaluating the deterioration of the polymer insulation material according to any one of claims 1 to 7.

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