A device and method for detecting high-temperature electrical performance of an insulating material

Abstract

This invention relates to the field of electrical performance testing technology for insulating materials, and particularly to a device and method for testing the high-temperature electrical performance of insulating materials. The device includes: a rigid frame, a movable plate, a manual pressurization mechanism, an upper electrode assembly, a lower electrode assembly, an electrical isolation structure, and a movable, split-type heating system. The movable, split-type heating system merges at the test position to form an annular heating cavity surrounding the insulating material under test, and separates at non-test positions to expose the insulating material. The method of this invention includes the following steps: a sample clamping step, a thermal expansion compensation pressurization step, a dynamic thermal cycling loading step, and a non-destructive withstand voltage test step. The device and testing method of this invention can accurately reproduce the key service stress state of materials, and are as intuitive to operate, easy to maintain, and flexible to configure as general-purpose tools, thereby achieving a fundamental optimization between R&D depth, quality inspection efficiency, and overall cost.

Description

Technical Field

[0001] This invention relates to the field of electrical performance testing technology for insulating materials, and in particular to a device and method for testing the high-temperature electrical performance of insulating materials. Background Technology

[0002] In the fields of energy development and conversion, such as heavy oil thermal recovery, shale oil in-situ conversion, and underground coal retorting, continuous tubular electric heaters are core energy conversion equipment. They require high-performance insulating materials (such as magnesium oxide) to ensure reliable isolation between the heating wire and the metal tube wall. These insulating materials operate under harsh environments of extreme high temperature, high pressure, and complex electro-thermal-mechanical stress coupling. Their high-temperature insulation resistance and withstand voltage directly determine the heater's safety, energy efficiency, and service life. Therefore, accurately evaluating the basic electrical performance of insulating materials under simulated operating temperatures is crucial in material development, product inspection upon arrival, and fault analysis.

[0003] In the performance testing of insulating materials for electric heaters, the core technical challenge of existing instruments lies in balancing testing accuracy, operational efficiency, and cost control. In practical applications, materials are subjected to extreme conditions of high temperature, high pressure, and thermo-electrical-mechanical stress coupling for extended periods. Conventional equipment is often limited to single steady-state high-temperature testing, failing to conveniently and cost-effectively simulate dynamic temperature cycles or comprehensive stress fields, resulting in discrepancies between test data and actual failure modes. Furthermore, adapting to diverse insulating component forms and enabling functions such as rapid electrode replacement and adjustable contact force often leads to complex instrument structures and high costs. In addition, the precision design required to ensure measurement accuracy at high temperatures often makes routine maintenance (such as electrode replacement and temperature sensing element calibration) difficult.

[0004] Specifically, existing testing devices suffer from the following technical shortcomings: First, the heating unit is usually fixedly integrated with the testing station, requiring room temperature and high temperature tests to be performed separately on different equipment or at different stations. Repeated sample assembly and disassembly is not only inefficient but also prone to introducing human error. Second, the contact pressure between the electrode and the sample is difficult to control precisely, especially in high-temperature environments. Due to the difference in the thermal expansion coefficients of materials, the contact pressure will change nonlinearly, leading to fluctuations in contact resistance and severely affecting the accuracy and repeatability of insulation resistance test data. Third, traditional withstand voltage tests often employ destructive methods, i.e., gradually increasing the voltage until the sample breaks down. For expensive high-temperature sintered insulating materials (such as high-purity magnesium oxide), the testing cost is high, and it is impossible to conduct multi-dimensional performance evaluations of the same material. Fourth, existing high-precision testing systems are often highly automated and integrated, with complex structures and high manufacturing costs, making it difficult to widely promote them in application scenarios with high requirements for economy and practicality, such as material research and development laboratories and production quality inspection sites.

[0005] Therefore, in order to address the bottleneck of existing high-temperature electrical performance testing technology for insulating materials, which aims to accurately reproduce the key service stress state of materials while being as intuitive to operate, easy to maintain, and flexible to configure as a general-purpose tool, and to achieve a fundamental optimization between R&D depth, quality inspection efficiency, and overall cost, a device and method for testing the high-temperature electrical performance of insulating materials are proposed. Summary of the Invention

[0006] To overcome the difficulty of existing high-temperature electrical performance testing technologies for insulating materials in simultaneously achieving both accurate reproduction of the material's key service stress state and making the device structure as intuitive to operate, easy to maintain, and flexible in configuration as a general-purpose tool.

[0007] The technical solution of this invention is: a high-temperature electrical performance testing device for insulating materials, comprising: The rigid frame consists of a base plate, a top plate, and multiple columns connecting the base plate and the top plate; The movable panel is slidably fitted onto the column; A manual pressurizing mechanism, installed on the top plate, includes a handwheel, a lead screw driven to rotate by the handwheel, and a conical disc connecting the lead screw and the movable plate. The manual pressurizing mechanism is used to drive the movable plate to move up and down along the column by rotating the handwheel. An upper electrode assembly is fixed to the movable plate and moves with the movable plate. The upper electrode assembly includes an upper electrode rod, a high-temperature spring disposed on the upper electrode rod, and an upper electrode detachably mounted on the top of the upper electrode rod. A lower electrode assembly is fixed to the base plate. The lower electrode assembly includes a lower electrode rod and a lower electrode detachably mounted on the top of the lower electrode rod. An electrical isolation structure includes ceramic rings disposed between the upper electrode rod and the movable plate, and between the lower electrode rod and the base plate; A movable split heating system includes two semi-circular electric heaters hinged to the base plate by a pivot and a joint. The semi-circular electric heaters can rotate around the pivot and merge to form an annular heating cavity surrounding the insulating material under test in the test position, and separate from each other in the non-test position to expose the insulating material under test. The semi-circular electric heater has a built-in heating element and a thermocouple for monitoring temperature. Furthermore, the detection device is configured to perform the following test procedure: In the first operation stage, the upper electrode is driven by the manual pressurization mechanism to move towards the insulating material to be tested placed on the lower electrode until the high temperature spring generates a preset compression amount, so that the insulating material to be tested is clamped between the upper electrode and the lower electrode. In the second operation stage, the two semi-circular electric heaters are brought together, and the heating element heats the insulating material under test, while the thermocouple monitors the heating temperature. In the third operation stage, during the heating process or after the target temperature is reached, the electrical performance parameters of the insulating material under test are collected by an external testing instrument connected to the upper electrode rod and the lower electrode rod.

[0008] Preferably, this invention constructs a manually operated, modularly adjustable, and safely insulated testing platform through the coordinated operation of a rigid frame, a manual pressurization mechanism, an upper electrode assembly, a lower electrode assembly, an electrical isolation structure, and a movable, split-type heating system. The design of the movable, split-type heater allows for rapid switching between room temperature and high temperature testing at the same workstation without sample disassembly. The manual pressurization mechanism, combined with a high-temperature spring, provides stable and repeatable contact pressure. The electrical isolation structure ensures the safety of high-voltage testing operations. The detachable electrode design allows the device to flexibly adapt to different testing standards and diverse sample sizes.

[0009] Preferably, in the manual pressurization mechanism, the lead screw is threadedly engaged with the lead screw sleeve fixed on the top plate, and the conical disc is fixed to the lower end of the lead screw and fixedly connected to the movable plate by fasteners, forming a transmission structure that converts the rotational motion of the lead screw into the linear motion of the movable plate.

[0010] Preferably, in the upper electrode assembly, the high-temperature spring is fitted onto the upper electrode rod, with one end abutting against the base of the upper electrode and the other end abutting against the lower surface of the movable plate, for providing a continuous flexible clamping force when clamping the insulating material being tested.

[0011] Preferably, in the movable split heating system, the two semi-circular electric heaters close together at the test position to form an annular heating cavity, and the central axis of the annular heating cavity coincides with the central axis of the upper electrode and the lower electrode.

[0012] Preferably, the upper electrode and the lower electrode have a variety of interchangeable specifications, including plate electrodes and spherical electrodes, to adapt to the insulating materials under test with different shapes and sizes.

[0013] A method for testing the high-temperature electrical properties of insulating materials based on the above-mentioned device includes the following steps: Sample clamping steps: Place the insulating material block to be tested on the lower electrode, rotate the handwheel to drive the upper electrode to move downward until the upper electrode contacts the insulating material block to be tested, and continue to rotate the handwheel to generate the initial compression of the high temperature spring to clamp the insulating material block to be tested; Thermal expansion compensation pressurization step: Based on the preset target test temperature and the thermal expansion characteristics of the insulation material being tested, determine the thermal expansion compensation amount, and adjust the handwheel in the opposite direction based on the thermal expansion compensation amount to adjust the compression amount of the high temperature spring so that the compression amount of the high temperature spring reaches the target compression amount after compensation. Dynamic thermal cycling loading steps: Two semi-circular electric heaters are closed to form an annular heating cavity. The heating element is started to heat the tested insulating material block according to the preset temperature rise program. At the same time, the insulation resistance and dielectric loss factor of the tested insulating material block are continuously collected during the temperature rise process to generate insulation resistance-temperature curves and dielectric loss factor-temperature curves. Non-destructive withstand voltage test procedure: After reaching the target test temperature and stabilizing, an external high-voltage source connected to the upper and lower electrode rods is used to apply a stepped-increase test voltage to the insulating material block under test. During each voltage holding stage, a micro-current noise signal flowing through the insulating material block under test is collected. The micro-current noise signal is subjected to spectrum analysis. When the amplitude of a specific characteristic frequency exceeds a preset threshold, the voltage increase is stopped and the current voltage value is recorded as the ultimate withstand voltage.

[0014] Preferably, the thermal expansion compensation pressurization step specifically includes: Read the initial compression Δx0 when the high-temperature spring contacts the tested insulating material block; Obtain the total thermal expansion elongation ΔL of the device at the target test temperature T; Obtain the pressure adaptive coefficient k related to the hardness of the tested insulating material block; The compensated target compression amount Δx_c is calculated according to the formula Δx_c=Δx0-k·ΔL; Rotating the handwheel causes the high-temperature spring to compress to Δx_c.

[0015] Preferably, the dynamic thermal cycling loading step further includes a sub-step of performing coupled diagnosis based on the insulation resistance-temperature curve and the dielectric loss factor-temperature curve: Monitor the insulation resistance-temperature curve. If an inflection point occurs during the heating process where the resistance value increases abnormally with the temperature, it is determined that the contact pressure is abnormal. Stop heating and return to the thermal expansion compensation pressurization step to readjust the compression amount. Record the temperature points corresponding to the characteristic peaks appearing in the dielectric loss factor-temperature curve as the critical temperatures for microstructural instability of the tested insulating material block.

[0016] Preferably, the non-destructive withstand voltage test step includes spectral analysis of the micro-current noise signal, which includes: The acquired microcurrent noise signal is subjected to a fast Fourier transform to generate a spectrum. In the spectrum, a characteristic frequency f_c that is distinct from the white noise background is identified; The amplitude A of the characteristic frequency f_c is monitored in real time and compared with the preset safety threshold A_max.

[0017] Preferably, the step-increase test voltage is applied by increasing the voltage step by step with a preset voltage step size ΔU, and maintaining each voltage level for a preset duration t until the stopping condition is met or the upper limit of the output voltage of the test instrument is reached.

[0018] The beneficial effects of this invention are: 1. This invention achieves convenient switching between room temperature and high temperature testing through the structural design of a movable split heater; two semi-circular electric heaters are hinged to the base plate through a rotating shaft and joint, and can be opened and closed freely like a door. During testing, they are closed to form a uniform annular heating cavity, and when not testing, they are moved apart, which facilitates room temperature testing and sample assembly and disassembly; this structural design allows for rapid switching between room temperature and high temperature testing modes without disassembling the sample, improving the overall efficiency of serial testing and comparative research; 2. This invention utilizes a manual lead screw combined with a high-temperature spring electrode pressurization mechanism, along with a thermal expansion compensation algorithm, to eliminate contact misjudgment caused by thermal expansion. The high-temperature spring provides continuous flexible clamping force, compensating for microscopic unevenness of the material surface and differences in thermal expansion. Based on the compensation algorithm of the formula Δx_c=Δx0-k·ΔL, without adding any automatic feedback device, it relies on the precise scale of the original manual mechanism to establish a nonlinear clamping state of cold relaxation and hot tightening, ensuring constant contact pressure throughout the entire temperature range. This solves the problem of contact force runaway caused by thermal expansion at high temperatures, and improves the accuracy and repeatability of insulation resistance test data at high temperatures. 3. This invention uses dynamic thermal cycling loading and multi-parameter coupled diagnosis to continuously collect insulation resistance and dielectric loss factor during the heating process and generate real-time change curves. It can not only monitor changes in contact state, but also capture microstructural changes (such as phase transitions and microcracks) of materials during the heating process, providing richer intermediate state data for material research and development, and realizing a leap from single steady-state testing to dynamic monitoring of temperature variation. 4. This invention is based on the spectral analysis of microcurrent noise in the pre-breakdown stage. It identifies the characteristic frequency f_c through fast Fourier transform and monitors its amplitude change. It can provide early warning when the voltage reaches 70%-80% of the breakdown threshold. It can accurately assess the withstand voltage limit of the material without causing actual breakdown damage to the sample. This method is especially useful for expensive high-temperature sintered insulating materials, such as high-purity magnesium oxide, which can reduce their research and development costs and allow the same sample to be tracked and tested throughout its entire life cycle. 5. This invention ensures testing accuracy while also considering cost control and ease of operation; the device structure is relatively simplified, mainly relying on manual precision mechanical transmission, avoiding the high manufacturing costs caused by highly automated integration; the comprehensive ceramic insulation design ensures the safety of high-voltage testing operations; the modular electrode design allows the device to flexibly adapt to different testing standards; the testing method of this invention improves the testing depth and intelligence level without increasing hardware costs; this makes the device suitable for use in scenarios with high requirements for economy and practicality, such as materials research and development laboratories and production quality inspection sites. Attached Figure Description

[0019] Figure 1 The diagram shown is a three-dimensional structural schematic of the high-temperature electrical performance testing device for insulating materials according to the present invention. Figure 2 The diagram shown is a schematic of the electrode raised state on the high-temperature electrical performance testing device for insulating materials according to the present invention. Figure 3 The diagram shown illustrates the placement of the insulating material block in the high-temperature electrical performance testing device for insulating materials according to the present invention. Figure 4 The diagram shown is a schematic of the electrode clamping sample state on the high-temperature electrical performance testing device for insulating materials of the present invention. Figure 5 The diagram shown is a schematic of the heater in the closed state of the high-temperature electrical performance testing device for insulating materials according to the present invention. Figure 6 The diagram shown is a flowchart illustrating the steps of the high-temperature electrical performance testing method for insulating materials according to the present invention. Explanation of reference numerals in the attached diagram: 1. Base; 2. Base plate; 3. Lower electrode rod; 4. Ceramic ring; 5. Support column; 6. Lower electrode; 7. Rotating shaft; 8. Joint; 9. Electric heater; 10. Thermocouple; 11. Upper electrode; 12. Upper electrode rod; 13. Movable plate; 14. Top plate; 15. Lead screw sleeve; 16. Lead screw; 17. Handwheel; 18. Conical disc; 19. High-temperature spring; 20. Slider; 21. Heating element. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Example 1: Please see Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 The present invention provides an embodiment: a high-temperature electrical performance testing device for insulating materials, comprising: The rigid frame consists of a base plate 2, a top plate 14, and multiple columns 5 connecting the base plate 2 and the top plate 14. The movable panel 13 is slidably fitted onto the column 5; The manual pressurization mechanism is installed on the top plate 14 and includes a handwheel 17, a lead screw 16 driven to rotate by the handwheel 17, and a conical disc 18 connecting the lead screw 16 and the movable plate 13. The manual pressurization mechanism is used to drive the movable plate 13 to move up and down along the column 5 by rotating the handwheel 17. The upper electrode assembly is fixed on the movable plate 13 and moves with the movable plate 13. The upper electrode assembly includes an upper electrode rod 12, a high-temperature spring 19 disposed on the upper electrode rod 12, and an upper electrode 11 detachably mounted on the top of the upper electrode rod 12. The lower electrode assembly is fixed on the base plate 2. The lower electrode assembly includes a lower electrode rod 3 and a lower electrode 6 that is detachably installed on the top of the lower electrode rod 3. The electrical isolation structure includes ceramic rings 4 disposed between the upper electrode rod 12 and the movable plate 13 and between the lower electrode rod 3 and the base plate 2; The movable split heating system includes two semi-circular electric heaters 9 hinged to the base plate 2 via a rotating shaft 7 and a joint 8. The semi-circular electric heaters 9 can rotate around the rotating shaft 7, and when they are in the test position, they merge to form an annular heating cavity surrounding the insulating material under test. When they are not in the test position, they separate from each other to expose the insulating material under test. The semi-circular electric heater 9 has a built-in heating element 21 and a thermocouple 10 for monitoring temperature. Furthermore, the testing device is configured to perform the following test procedures: In the first operation stage, the upper electrode 11 is driven to move towards the insulating material to be tested placed on the lower electrode 6 by a manual pressurization mechanism until the high temperature spring 19 generates a preset compression amount, so that the insulating material to be tested is clamped between the upper electrode 11 and the lower electrode 6. In the second operation stage, the two semi-circular electric heaters 9 are brought together, and the insulating material under test is heated by the heating element 21, while the heating temperature is monitored by the thermocouple 10. In the third operation stage, during the heating process or after the target temperature is reached, the electrical performance parameters of the insulating material under test are collected by an external testing instrument connected to the upper electrode rod 12 and the lower electrode rod 3.

[0022] This invention constructs a manually operated, precision-controlled, modularly adjustable, and safely insulated testing platform through the coordinated use of a rigid frame, a manual pressurization mechanism, an upper electrode assembly, a lower electrode assembly, an electrical isolation structure, and a movable, split-type heating system. The design of the movable, split-type heater allows for rapid switching between room temperature and high-temperature testing at the same workstation without sample disassembly. The manual pressurization mechanism, combined with a high-temperature spring, provides stable and repeatable contact pressure. The electrical isolation structure ensures the safety of high-voltage testing operations. The detachable electrode design allows the device to flexibly adapt to different testing standards and diverse sample sizes.

[0023] Furthermore, in the manual pressurization mechanism, the lead screw 16 is threadedly engaged with the lead screw sleeve 15 fixed on the top plate 14, and the conical disc 18 is fixed to the lower end of the lead screw 16 and fixedly connected to the movable plate 13 through fasteners, forming a transmission structure that converts the rotational motion of the lead screw 16 into the linear motion of the movable plate 13; this transmission structure has a self-locking characteristic and can be stably maintained in any position, ensuring the stability of the electrode position during the test and avoiding position drift caused by gravity or vibration.

[0024] Furthermore, in the upper electrode assembly, a high-temperature spring 19 is fitted onto the upper electrode rod 12, with one end abutting against the base of the upper electrode 11 and the other end abutting against the lower surface of the movable plate 13, to provide a continuous flexible clamping force when clamping the insulating material being tested; the high-temperature spring 19 can compensate for the microscopic unevenness of the material surface and the difference in thermal expansion, ensuring reliable contact, while avoiding sample damage caused by rigid clamping.

[0025] Furthermore, in the movable split heating system, the two semi-circular electric heaters 9 are joined together at the test position to form an annular heating cavity. The central axis of the annular heating cavity coincides with the central axis of the upper electrode 11 and the lower electrode 6. This coaxial structure ensures heating uniformity, makes the temperature field distribution around the tested insulating material symmetrical, and avoids test errors caused by uneven temperature.

[0026] Furthermore, the upper electrode 11 and the lower electrode 6 have a variety of interchangeable specifications, including plate electrodes and ball electrodes, to adapt to the insulation materials under test with different shapes and sizes; this modular design improves the versatility and ease of maintenance of the device, and users can quickly replace electrodes of different shapes according to the test standards or sample specifications.

[0027] A method for testing the high-temperature electrical properties of insulating materials based on the above-mentioned device includes the following steps: Sample clamping steps: Place the insulating material block to be tested on the lower electrode 6, rotate the handwheel 17 to drive the upper electrode 11 to move downward until the upper electrode 11 contacts the insulating material block to be tested, and continue to rotate the handwheel 17 to generate the initial compression of the high temperature spring 19 to clamp the insulating material block to be tested. Thermal expansion compensation pressurization step: Based on the preset target test temperature and the thermal expansion characteristics of the insulation material being tested, determine the thermal expansion compensation amount, and adjust the handwheel 17 in the opposite direction based on the thermal expansion compensation amount to adjust the compression amount of the high temperature spring 19 so that the compression amount of the high temperature spring 19 reaches the target compression amount after compensation. Dynamic thermal cycling loading steps: The two semi-circular electric heaters 9 are closed to form an annular heating cavity. The heating element 21 is started to heat the tested insulating material block according to the preset heating program. At the same time, the insulation resistance and dielectric loss factor of the tested insulating material block are continuously collected during the heating process to generate insulation resistance-temperature curves and dielectric loss factor-temperature curves. Non-destructive withstand voltage test procedure: After reaching the target test temperature and stabilizing, an external high-voltage source connected to the upper electrode rod 12 and the lower electrode rod 3 is used to apply a stepped increase test voltage to the insulating material block under test. During each voltage holding stage, the micro-current noise signal flowing through the insulating material block under test is collected. The micro-current noise signal is subjected to spectrum analysis. When the amplitude of a specific characteristic frequency is detected to exceed the preset threshold, the voltage increase is stopped and the current voltage value is recorded as the ultimate withstand voltage.

[0028] The method of this invention achieves in-depth exploration and accurate evaluation of the performance of insulating materials by introducing thermal expansion compensation algorithm, dynamic thermal cycle monitoring and non-destructive breakdown prediction based on microcurrent noise spectrum analysis, thereby improving the intelligence level of testing without increasing hardware costs.

[0029] Furthermore, the thermal expansion compensation pressurization step specifically includes: Read the initial compression Δx0 when the high-temperature spring 19 contacts the tested insulating material block; The overall thermal expansion elongation ΔL of the device is obtained at the target test temperature T; Obtain the pressure adaptive coefficient k related to the hardness of the tested insulating material block; The target compression amount Δx_c after compensation is calculated according to the formula Δx_c=Δx0-k·ΔL; Rotating the handwheel 17 causes the high-temperature spring 19 to compress to Δx_c.

[0030] This compensation algorithm establishes a nonlinear clamping state of cold-state relaxation and hot-state tightening, ensuring that the contact pressure recovers to the optimal value when the temperature is raised to the target temperature T, thereby eliminating the runaway contact force caused by thermal expansion and improving the accuracy and repeatability of insulation resistance test data at high temperatures. Among them, the comprehensive thermal expansion elongation ΔL can be obtained in advance through finite element analysis or experimental calibration to obtain a value table at different temperatures. The pressure adaptive coefficient k is usually in the range of 0.5-0.8, and the specific value is determined according to the material hardness.

[0031] Furthermore, the dynamic thermal cycling loading step also includes a sub-step for coupled diagnosis based on the insulation resistance-temperature curve and the dielectric loss factor-temperature curve: Monitor the insulation resistance-temperature curve. If an inflection point occurs during the heating process where the resistance value increases abnormally with the temperature, it is determined that the contact pressure is abnormal. Stop heating and return to the thermal expansion compensation pressurization step to readjust the compression amount. Record the temperature points corresponding to the characteristic peaks appearing in the dielectric loss factor-temperature curve, and use them as the critical temperatures for microstructural instability of the tested insulating material block.

[0032] This coupled diagnostic method can monitor changes in the contact state in real time, promptly detect abnormal contact pressure caused by thermal expansion, and ensure the consistency of test conditions through feedback adjustment. At the same time, the characteristic peaks in the dielectric loss factor curve can reveal information such as the propagation of microcracks or impurity phase transformations inside the material, providing an important basis for material modification.

[0033] Furthermore, in the non-destructive withstand voltage test procedure, the spectral analysis of the microcurrent noise signal includes: The acquired microcurrent noise signal is subjected to a fast Fourier transform to generate a spectrum. Identify the characteristic frequency f_c that is distinct from the white noise background in the spectrum; The amplitude A of the characteristic frequency f_c is monitored in real time and compared with the preset safety threshold A_max.

[0034] This spectral analysis method is based on the physical nature of the pre-breakdown stage: when the voltage approaches 70%-80% of the material's breakdown threshold, the internal space charge accumulates to a critical state, and partial discharge is about to occur. At this time, a specific frequency spike (characteristic frequency f_c) will appear in the spectrum of the current noise. By monitoring the amplitude change of this characteristic frequency, the withstand voltage limit of the material can be accurately assessed without causing actual breakdown damage to the sample, so that the same sample can continue to be used for subsequent lifetime testing, microscopic analysis, or other comparative studies.

[0035] Furthermore, the step-up test voltage is applied by gradually increasing the voltage in stages with a preset voltage step size ΔU, and maintaining each voltage level for a preset duration t until the stopping condition is met or the upper limit of the output voltage of the test instrument is reached. This step-up voltage boosting strategy can provide a stable time period for the acquisition of micro-current noise signals, ensuring the accuracy of spectrum analysis, while avoiding over-voltage breakdown that may be caused by rapid voltage boosting.

[0036] Through the above steps, this invention achieves convenient switching between ambient and high-temperature testing through the structural design of a movable, split heater. Two semi-circular electric heaters 9 are hinged to the base plate 2 via a rotating shaft 7 and a joint 8, allowing them to open and close freely like a door. During testing, they close to form a uniform annular heating cavity; when not testing, they are removed, facilitating ambient temperature testing and sample assembly / disassembly. This structural design enables rapid switching between ambient and high-temperature testing modes without sample disassembly, improving the overall efficiency of serialized testing and comparative studies. This invention utilizes a manual lead screw 16 in conjunction with a high-temperature spring 19 for electrode pressurization, along with a thermal expansion compensation algorithm. This invention eliminates contact misjudgment caused by thermal expansion; the high-temperature spring 19 provides continuous flexible clamping force to compensate for microscopic unevenness of the material surface and differences in thermal expansion; based on the compensation algorithm of the formula Δx_c=Δx0-k·ΔL, without adding any automatic feedback device, it relies on the precision scale of the original manual mechanism to establish a nonlinear clamping state of cold relaxation and hot tightening, ensuring constant contact pressure throughout the temperature range, solving the problem of contact force runaway caused by thermal expansion at high temperatures, and improving the accuracy and repeatability of insulation resistance test data at high temperatures; this invention uses dynamic thermal cycling loading and multi-parameter coupled diagnosis to... During the heating process, insulation resistance and dielectric loss factor are continuously collected to generate real-time change curves. This not only monitors changes in contact state but also captures microstructural changes in materials during heating, providing richer intermediate-state data for material research and development. This represents a leap from simple steady-state testing to dynamic monitoring under varying temperatures. Based on the spectral analysis of microcurrent noise in the pre-breakdown stage, this invention identifies characteristic frequencies f_c through Fast Fourier Transform and monitors their amplitude changes. It can provide early warning when the voltage reaches 70%-80% of the breakdown threshold, accurately assessing the material's withstand voltage limit without causing actual breakdown damage to the sample. This invention balances test accuracy with cost control and ease of operation. The device structure is relatively simplified, relying mainly on manual precision mechanical transmission, avoiding the high manufacturing costs associated with highly automated integration. The comprehensive ceramic insulation design ensures the safety of high-voltage testing operations. The modular electrode design allows the device to flexibly adapt to different testing standards. The testing method of this invention improves testing depth and intelligence without increasing hardware costs. This makes the device suitable for use in material research laboratories and production quality inspection sites where high economic efficiency and practicality are required.

[0037] Example 2: Optionally, this embodiment provides a high-temperature electrical performance testing device for insulating materials, including a rigid frame, a movable plate 13, a manual pressurization mechanism, an upper electrode assembly, a lower electrode assembly, an electrical isolation structure, and a movable split-type heating system.

[0038] The rigid frame consists of a base plate 2, a top plate 14, and multiple columns 5 connecting the base plate 2 and the top plate 14. Specifically, four bases 1 support the base plate 2, four columns 5 are fixed on the base plate 2, and the top plate 14 is fixed to the top of the columns 5. The four columns 5 are connected to the base plate 2 and the top plate 14 by threads.

[0039] The movable plate 13 is slidably mounted on the column 5; specifically, the movable plate 13 is connected to the four columns 5 through four sliders 20, which slide up and down along the columns 5, causing the movable plate 13 to move up and down.

[0040] The manual pressurization mechanism is mounted on the top plate 14 and includes a handwheel 17, a lead screw 16, and a conical disc 18. A lead screw sleeve 15 is fixed to the top plate 14 with screws, and the lead screw sleeve 15 and the lead screw 16 are threaded together to form a helical rotation structure. The handwheel 17 is installed at the top of the lead screw 16, and the lead screw 16 moves up and down by rotating the handwheel 17. The conical disc 18 is installed below the lead screw 16 and is fixedly connected to the movable plate 13 by screws to form a linkage mechanism. This mechanism converts the rotational motion of the lead screw 16 into the linear motion of the movable plate 13. The rotation of the handwheel 17 can precisely control the up and down movement of the movable plate 13 along the column 5. This transmission structure has a self-locking characteristic and can be stably maintained in any position to ensure the stability of the electrode position during the test.

[0041] The upper electrode assembly is fixed to the movable plate 13 and moves with the movable plate 13; the upper electrode assembly includes an upper electrode rod 12, a high-temperature spring 19, and a detachable upper electrode 11; the upper electrode rod 12 is fixed to the movable plate 13 by screws through a ceramic ring 4; the upper electrode 11 is detachably installed at the top of the upper electrode rod 12, and different specifications can be replaced according to the test requirements; the high-temperature spring 19 is fitted on the upper electrode rod 12, with one end abutting against the base of the upper electrode 11 and the other end abutting against the lower surface of the movable plate 13, and is used to provide a continuous flexible clamping force when clamping the insulating material under test, to compensate for the micro-unevenness of the material surface and the difference in thermal expansion.

[0042] The lower electrode assembly is fixed on the base plate 2; the lower electrode assembly includes a lower electrode rod 3 and a detachable lower electrode 6; the lower electrode rod 3 is fixed to the base plate 2 with screws by a ceramic ring 4, so that the lower electrode rod 3 is electrically isolated from the base plate 2; the lower electrode 6 is detachably installed at the top of the lower electrode rod 3, and different specifications can be replaced according to the test requirements.

[0043] The electrical isolation structure includes ceramic rings 4 disposed between the upper electrode rod 12 and the movable plate 13 and between the lower electrode rod 3 and the base plate 2; this structure ensures that the test circuit is isolated from the metal frame of the device during high-voltage testing, thus protecting the safety of personnel and equipment.

[0044] The movable split heating system includes two semi-circular electric heaters 9 hinged to the base plate 2 via a pivot 7 and a joint 8. Specifically, two pivots 7 are installed on the base plate 2, each connecting two joints 8. Two independent semi-circular electric heaters 9 are installed at the ends of the joints 8. The semi-circular electric heaters 9 can rotate around the pivot 7, merging at the test position to form an annular heating cavity surrounding the insulating material under test, and separating at non-test positions to expose the insulating material under test. The semi-circular electric heaters 9 have a built-in heating element 21 and a thermocouple 10 for monitoring temperature. The heating element 21 generates heat when energized, and the thermocouple 10 monitors the temperature in real time and feeds it back to an external temperature controller to achieve automatic heating control.

[0045] The device in this embodiment is configured to perform the following test procedure: In the first operation stage, the upper electrode 11 is driven to move towards the insulating material to be tested placed on the lower electrode 6 by a manual pressurization mechanism until the high temperature spring 19 generates a preset compression amount, so that the insulating material to be tested is clamped between the upper electrode 11 and the lower electrode 6. In the second operation stage, the two semi-circular electric heaters 9 are brought together, and the insulating material under test is heated by the heating element 21, while the heating temperature is monitored by the thermocouple 10. In the third operation stage, during the heating process or after the target temperature is reached, the electrical performance parameters of the insulating material under test are collected by an external testing instrument connected to the upper electrode rod 12 and the lower electrode rod 3.

[0046] Example 3: Optionally, this embodiment further refines the transmission structure of the manual pressurization mechanism and the installation method of the high-temperature spring based on embodiment 2.

[0047] In the manual pressurization mechanism, the lead screw 16 is threadedly engaged with the lead screw sleeve 15 fixed on the top plate 14, and the conical disc 18 is fixed to the lower end of the lead screw 16 and fixedly connected to the movable plate 13 by fasteners. This transmission structure forms a precision lead screw and nut pair, which converts the rotational motion of the handwheel 17 into the linear motion of the movable plate 13. Since the threaded pair has a self-locking characteristic, when the handwheel 17 stops rotating, the movable plate 13 can be stably held in any position and will not be displaced due to gravity or slight vibration, thus ensuring the stability of the electrode position during the test.

[0048] In the upper electrode assembly, the high-temperature spring 19 is specifically made of a high-temperature resistant alloy material (such as Inconel X-750) to ensure that it can maintain good elastic performance in high-temperature environments. The high-temperature spring 19 is fitted on the upper electrode rod 12, with its upper end abutting against the lower surface of the movable plate 13 and its lower end abutting against the base of the upper electrode 11. When the movable plate 13 moves downward, the high-temperature spring 19 is compressed, generating an upward reaction force, which is transmitted to the surface of the insulating material being tested through the upper electrode 11. This spring force can compensate for the thermal expansion differences caused by temperature changes and the microscopic unevenness of the sample surface, ensuring the stability and consistency of the contact pressure throughout the test. The relationship between the spring compression and the generated pressure follows Hooke's Law: F = k·Δx, where F is the spring force, k is the spring stiffness coefficient, and Δx is the spring compression. The operator can indirectly control the clamping force by reading the spring compression.

[0049] Example 4: Optionally, this embodiment further optimizes the layout of the movable split heating system and the replaceability of the electrodes based on embodiment 2.

[0050] When the two semi-circular electric heaters 9 are brought together at the test position, they form an annular heating cavity. The central axis of the annular heating cavity coincides with the central axis of the upper electrode 11 and the lower electrode 6. This coaxial design ensures that the temperature field distribution around the tested insulating material is symmetrical and the heating is uniform, avoiding test errors caused by uneven temperature. Specifically, when the two semi-circular electric heaters 9 are brought together, their inner walls maintain an appropriate gap with the upper electrode 11, the lower electrode 6, and the tested insulating material, which ensures effective heat transfer and avoids short circuits or interference caused by direct contact with the electrodes.

[0051] The upper electrode 11 and the lower electrode 6 are available in various interchangeable specifications, including but not limited to plate electrodes and spherical electrodes. Plate electrodes are suitable for blocky samples with parallel planes and can provide a uniform electric field distribution. Spherical electrodes are suitable for irregularly shaped samples or testing scenarios that require point contact. The electrode materials are made of high-temperature resistant and highly conductive materials, such as tungsten, molybdenum or their alloys, to ensure that they maintain good conductivity and mechanical strength at high temperatures. The electrodes and electrode rods are connected by threaded connections or quick-plug connections, which facilitates quick replacement according to testing standards or sample specifications, improving the versatility and ease of maintenance of the device.

[0052] Example 5: Optionally, this embodiment provides a method for testing the high-temperature electrical performance of insulating materials based on the device of Embodiment 1, specifically including a sample clamping step, a thermal expansion compensation pressurization step, a dynamic thermal cycling loading step, and a non-destructive withstand voltage test step.

[0053] First, the sample clamping procedure is performed: Based on the dimensions of the magnesium oxide ceramic block to be tested and the testing standards, the operator installs the appropriate upper electrode 11 and lower electrode 6 on the upper electrode rod 12 and lower electrode rod 3, respectively; rotating the handwheel 17 moves the movable plate 13 upwards via the lead screw 16 and conical disk 18, leaving sufficient space between the upper electrode 11 and the lower electrode 6; the insulating material block to be tested is placed on the lower electrode 6; the handwheel 17 is slowly rotated in the opposite direction, moving the upper electrode 11 downwards; when the upper electrode 11 just contacts the insulating material block to be tested, rotation is stopped. At this point, the high-temperature spring 19 is in a critical compression state, and the initial compression amount Δx0 of the spring is recorded; the handwheel 17 is continued to be rotated to generate a certain compression amount in the high-temperature spring 19 to clamp the insulating material block to be tested.

[0054] Next, the thermal expansion compensation pressurization step is performed: Based on the preset target test temperature T and the thermal expansion characteristics of the insulation material being tested, the thermal expansion compensation amount is determined; this specifically includes the following sub-steps: A1: Obtain the total thermal expansion elongation ΔL of the device at the target test temperature T; this ΔL value can be obtained in advance through finite element analysis or experimental calibration, and a table of ΔL values ​​at different temperatures can be established for the operator to look up; ΔL reflects the total thermal expansion elongation of the entire force transmission path from the contact point of the upper electrode 11 through the upper electrode rod 12, the movable plate 13, the column 5, the base plate 2 to the lower electrode 6 when the temperature rises from room temperature to the target temperature T. A2: Obtain the pressure adaptive coefficient k related to the hardness of the tested insulating material block; the value of k is usually in the range of 0.5-0.8, with a smaller value for softer materials and a larger value for harder materials. The specific value can be determined based on the technical parameters or empirical data provided by the material manufacturer. A3: Calculate the target compression amount Δx_c after compensation according to the formula Δx_c = Δx0 - k·ΔL; A4: Rotate handwheel 17 and observe the scale indicator ring on the upper electrode rod 12 to make the compression of the high temperature spring 19 reach Δx_c.

[0055] The physical meaning of this compensation formula is as follows: at room temperature, a negative compensation amount is preset, that is, the spring compression is less than the compression at the initial contact, and a cold relaxation state is established; when the temperature rises to the target temperature T, the entire device generates a thermal expansion elongation of ΔL along the force transmission path. This elongation will be converted into additional compression on the tested insulating material, making the actual compression amount Δx_c + ΔL = Δx0 + (1-k)ΔL; by reasonably selecting the value of k, the actual compression amount can be made close to or equal to the optimal value, thereby eliminating the contact force runaway caused by thermal expansion.

[0056] Then, the dynamic thermal cycling loading step is performed: rotate joint 8 to bring the two semi-circular electric heaters 9 together and wrap them around the insulating material block to be tested; energize the two semi-circular electric heaters 9 and set the temperature program through thermocouple 10 and external temperature controller, for example, to heat up to 600℃ at a rate of 5℃ / min; throughout the heating process, continuously collect the insulation resistance R(t) and dielectric loss factor tanδ(t) of the insulating material block to be tested through a precision impedance analyzer connected to the upper electrode rod 12 and the lower electrode rod 3, and generate insulation resistance-temperature curves and dielectric loss factor-temperature curves.

[0057] Simultaneously, coupled diagnostics are performed during the heating process: the insulation resistance-temperature curve is monitored. According to the intrinsic characteristics of insulating materials, the insulation resistance usually decreases exponentially with increasing temperature, which is consistent with the thermal excitation theory. If a reversal inflection point occurs at a certain temperature point T_x where the resistance value increases abnormally with increasing temperature, it is determined that the contact pressure is abnormal due to thermal expansion (excessive compression). At this time, heating should be stopped, and after the device cools down, the thermal expansion compensation pressurization step should be returned to readjust the compression amount. The temperature point corresponding to the characteristic peak appearing in the dielectric loss factor-temperature curve is recorded as the critical temperature for microstructural instability of the tested insulating material block. This information can be used to analyze phenomena such as microcrack propagation or impurity phase transformation inside the material.

[0058] Finally, a non-destructive withstand voltage test is performed: After reaching and stabilizing the target test temperature T, an external high-voltage source connected to the upper electrode rod 12 and the lower electrode rod 3 is used to apply a stepped increase in test voltage to the insulating material block under test; specifically, a step-by-step voltage boosting method is adopted, with the voltage gradually increased in a preset voltage step size ΔU (e.g., 500V), and each voltage level is held for a preset duration t (e.g., 60 seconds); during each voltage holding phase, a broadband micro-current detection module (which can be integrated into an external test instrument) is used to collect the micro-current noise signal flowing through the insulating material block under test.

[0059] The acquired micro-current noise signal is subjected to spectral analysis, which includes the following sub-steps: B1: Perform a Fast Fourier Transform (FFT) on the microcurrent noise signal to generate a spectrum; under normal circumstances, the current noise is distributed as uniform white noise, and there are no obvious spikes in the spectrum.

[0060] B2: Identify the characteristic frequency f_c that is distinct from the white noise background in the spectrum diagram; Studies have shown that when the voltage approaches 70%-80% of the material's breakdown threshold, the internal space charge of the material accumulates to a critical state, and partial discharge is about to occur. At this time, a specific frequency spike will appear in the spectrum diagram of the current noise. This characteristic frequency f_c is related to factors such as the dielectric properties and geometric dimensions of the material.

[0061] B3: Monitor the amplitude A of the characteristic frequency f_c in real time and compare it with the preset safety threshold A_max; A_max can be preset based on historical data or experience value.

[0062] When the amplitude A of the characteristic frequency f_c exceeds the preset threshold A_max, the system issues an audible and visual alarm, prompting the operator to immediately stop the voltage increase and record the voltage value at this time as the ultimate withstand voltage (or pre-breakdown voltage) of the material at this temperature. This method can accurately assess the withstand voltage limit of the material without causing actual breakdown damage to the sample, so that the same sample can continue to undergo subsequent lifetime testing, microscopic analysis or other comparative studies.

[0063] Example 6: Optionally, this embodiment provides a detailed description of the coupling diagnosis in the dynamic thermal cycling loading step, based on embodiment 5.

[0064] In addition to monitoring the insulation resistance-temperature curve and the dielectric loss factor-temperature curve during dynamic thermal cycling, the following diagnostic mechanisms are also introduced: For the insulation resistance-temperature curve R(T), its normal variation should conform to the Arrhenius equation: R(T)=R0·exp(E_a / (k_B·T)), where R0 is the pre-exponential factor, E_a is the thermal activation energy, k_B is the Boltzmann constant, and T is the absolute temperature. After taking the logarithm, lnR and 1 / T should have a linear relationship. If there is a significant deviation from linearity in a certain temperature range, especially if the resistance value increases abnormally, it indicates that the contact pressure has increased abnormally, leading to changes in the contact area or elastic deformation of the sample. In this case, heating should be stopped and readjusted.

[0065] For the dielectric loss factor-temperature curve tanδ(T), its normal change is usually a slow increase with increasing temperature; if a characteristic peak appears, it indicates the existence of some relaxation process or structural transformation; the temperature T_p corresponding to the characteristic peak can be automatically identified by differentiation or peak detection algorithm; the T_p value is recorded as the critical temperature for the instability of the material microstructure, and this information has important reference value for material modification and process optimization.

[0066] In addition, correlation analysis between insulation resistance and dielectric loss factor can be introduced. Under normal circumstances, as the temperature rises, the insulation resistance decreases and the dielectric loss factor increases, and the two are negatively correlated. If a positive correlation occurs (i.e., the resistance increases while the loss increases), or if the correlation changes abruptly, it also indicates that abnormal changes have occurred inside the material or at the contact interface.

[0067] Example 7: This embodiment, based on embodiment 5, provides a detailed description of the spectrum analysis and threshold setting in the non-destructive withstand voltage test procedure.

[0068] The following specific methods are used for spectral analysis of micro-current noise signals: C1: The micro-current noise signal acquired during each voltage holding stage is segmented and processed, with each segment having a length of 2^N sampling points (e.g., 1024 points) to ensure FFT calculation efficiency. C2: Apply a window function (such as a Hanning window) to each signal segment to reduce spectral leakage, and then perform an FFT transform to obtain the power spectral density function S(f); C3: Averaging the power spectrum of multiple signal segments to reduce the impact of random noise and improve the stability of spectrum estimation; C4: Search for spectral peaks in the power spectrum that are significantly higher than the background noise; the background noise level can be obtained by calculating the average power spectral density when there is no partial discharge; the peak identification condition is: at a certain frequency f, S(f)>μ+n·σ, where μ is the mean of the background noise, σ is the standard deviation of the background noise, and n is the confidence coefficient (usually taken as 3-5). C5: Record the spectral peak frequency f_c and its amplitude A that meet the conditions.

[0069] The safety threshold A_max can be set based on one of the following methods: Empirical threshold method: Based on a large amount of historical test data of similar materials, statistical analysis is performed on the characteristic frequency amplitude range of the pre-breakdown stage, and the lower value is taken as the safety threshold.

[0070] Dynamic threshold method: At the start of the test, a low voltage (such as the initial voltage) is applied, and the current noise of this stage is collected and its spectrum is calculated as a reference. As the voltage increases, the difference between the current spectrum and the reference spectrum is calculated in real time. When the difference exceeds a preset multiple, an alarm is triggered.

[0071] Trend analysis method: Monitor the trend of characteristic frequency amplitude A as voltage increases. When dA / dU exceeds the preset threshold, it indicates that the breakdown critical region is about to be entered, triggering an alarm.

[0072] When the alarm is triggered and the voltage boost is stopped, the current voltage value V_max is recorded as the ultimate withstand voltage. This value can be conservatively estimated as the lower limit of the material's breakdown voltage for material screening and quality control. If a more accurate breakdown voltage value is required, routine destructive testing can be performed on other samples in the same batch, and V_max can be compared and calibrated with the destructive test results.

[0073] Through the above steps, this embodiment achieves a comprehensive and accurate evaluation of the high-temperature dynamic electrical properties of insulating materials without damaging the sample, providing a reliable technical means for material research and development and quality control.

[0074] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A high-temperature electrical performance testing device for insulating materials, characterized in that: include: The rigid frame consists of a base plate (2), a top plate (14), and multiple columns (5) connecting the base plate (2) and the top plate (14); The movable plate (13) is slidably fitted onto the column (5); The manual pressurization mechanism is installed on the top plate (14) and includes a handwheel (17), a lead screw (16) driven to rotate by the handwheel (17), and a conical disc (18) connecting the lead screw (16) and the movable plate (13). The manual pressurization mechanism is used to drive the movable plate (13) to move up and down along the column (5) by rotating the handwheel (17). The upper electrode assembly is fixed on the movable plate (13) and moves with the movable plate (13). The upper electrode assembly includes an upper electrode rod (12), a high temperature spring (19) disposed on the upper electrode rod (12), and an upper electrode (11) detachably mounted on the top of the upper electrode rod (12). The lower electrode assembly is fixed on the base plate (2). The lower electrode assembly includes a lower electrode rod (3) and a lower electrode (6) detachably mounted on the top of the lower electrode rod (3). The electrical isolation structure includes a ceramic ring (4) disposed between the upper electrode rod (12) and the movable plate (13) and between the lower electrode rod (3) and the base plate (2). The movable split heating system includes two semi-circular electric heaters (9) hinged to the base plate (2) via a pivot (7) and a joint (8). The semi-circular electric heaters (9) can rotate around the pivot (7), merge to form an annular heating cavity surrounding the insulating material under test at the test position, and separate from each other at the non-test position to expose the insulating material under test. The semi-circular electric heater (9) has a built-in heating element (21) and a thermocouple (10) for monitoring temperature. Furthermore, the detection device is configured to perform the following test procedure: In the first operation stage, the upper electrode (11) is driven by the manual pressurization mechanism to move towards the insulating material to be tested placed on the lower electrode (6) until the high temperature spring (19) generates a preset compression amount, so that the insulating material to be tested is clamped between the upper electrode (11) and the lower electrode (6). In the second operation stage, the two semi-circular electric heaters (9) are closed together, and the insulation material under test is heated by the heating element (21), and the heating temperature is monitored by the thermocouple (10). In the third operation stage, during the heating process or after the target temperature is reached, the electrical performance parameters of the insulation material under test are collected by an external testing instrument connected to the upper electrode rod (12) and the lower electrode rod (3).

2. The high-temperature electrical performance testing device for insulating materials according to claim 1, characterized in that: In the manual pressurization mechanism, the lead screw (16) is threadedly engaged with the lead screw sleeve (15) fixed on the top plate (14), and the conical disc (18) is fixed to the lower end of the lead screw (16) and fixedly connected to the movable plate (13) by fasteners, forming a transmission structure that converts the rotational motion of the lead screw (16) into the linear motion of the movable plate (13).

3. The high-temperature electrical performance testing device for insulating materials according to claim 1, characterized in that: In the upper electrode assembly, the high-temperature spring (19) is mounted on the upper electrode rod (12), with one end abutting against the base of the upper electrode (11) and the other end abutting against the lower surface of the movable plate (13), for providing a continuous flexible clamping force when clamping the insulating material to be tested.

4. The high-temperature electrical performance testing device for insulating materials according to claim 1, characterized in that: In the movable split heating system, the two semi-circular electric heaters (9) are joined together at the test position to form an annular heating cavity, and the central axis of the annular heating cavity coincides with the central axis of the upper electrode (11) and the lower electrode (6).

5. The high-temperature electrical performance testing device for insulating materials according to claim 4, characterized in that: The upper electrode (11) and the lower electrode (6) have a variety of interchangeable specifications, including plate electrodes and ball electrodes, for adapting to insulating materials of different shapes and sizes.

6. A method for testing the high-temperature electrical properties of insulating materials based on the high-temperature electrical property testing device for insulating materials according to any one of claims 1-5, characterized in that: Includes the following steps: Sample clamping steps: Place the insulating material block to be tested on the lower electrode (6), rotate the handwheel (17) to drive the upper electrode (11) to move downward until the upper electrode (11) contacts the insulating material block to be tested, and continue to rotate the handwheel (17) to generate the initial compression of the high temperature spring (19) to clamp the insulating material block to be tested; Thermal expansion compensation pressurization step: Based on the preset target test temperature and the thermal expansion characteristics of the insulation material being tested, determine the thermal expansion compensation amount, and adjust the handwheel (17) in the opposite direction based on the thermal expansion compensation amount to adjust the compression amount of the high temperature spring (19) so that the compression amount of the high temperature spring (19) reaches the target compression amount after compensation. Dynamic thermal cycling loading steps: Close the two semi-circular electric heaters (9) to form an annular heating cavity, start the heating element (21) to heat the tested insulating material block according to the preset heating program, and at the same time continuously collect the insulation resistance and dielectric loss factor of the tested insulating material block during the heating process to generate insulation resistance-temperature curve and dielectric loss factor-temperature curve. Non-destructive withstand voltage test procedure: After reaching the target test temperature and stabilizing, an external high voltage source connected to the upper electrode rod (12) and the lower electrode rod (3) is used to apply a stepped increase test voltage to the insulating material block under test. During each voltage holding stage, the micro-current noise signal flowing through the insulating material block under test is collected. The spectrum analysis of the micro-current noise signal is performed. When the amplitude of a specific characteristic frequency is detected to exceed the preset threshold, the voltage increase is stopped and the current voltage value is recorded as the ultimate withstand voltage.

7. The method for testing the high-temperature electrical properties of insulating materials according to claim 6, characterized in that: The thermal expansion compensation pressurization step specifically includes: Read the initial compression Δx0 when the high temperature spring (19) contacts the tested insulating material block; Obtain the total thermal expansion elongation ΔL of the device at the target test temperature T; Obtain the pressure adaptive coefficient k related to the hardness of the tested insulating material block; The compensated target compression amount Δx_c is calculated according to the formula Δx_c=Δx0-k·ΔL; Rotate the handwheel (17) to compress the high-temperature spring (19) to Δx_c.

8. The method for testing the high-temperature electrical properties of insulating materials according to claim 6, characterized in that: The dynamic thermal cycling loading step further includes a sub-step of coupled diagnosis based on the insulation resistance-temperature curve and the dielectric loss factor-temperature curve: Monitor the insulation resistance-temperature curve. If an inflection point occurs during the heating process where the resistance value increases abnormally with the temperature, it is determined that the contact pressure is abnormal. Stop heating and return to the thermal expansion compensation pressurization step to readjust the compression amount. Record the temperature points corresponding to the characteristic peaks appearing in the dielectric loss factor-temperature curve as the critical temperatures for microstructural instability of the tested insulating material block.

9. A method for testing the high-temperature electrical properties of insulating materials according to claim 6, characterized in that: The non-destructive withstand voltage test step includes spectral analysis of the micro-current noise signal, which includes: The acquired microcurrent noise signal is subjected to a fast Fourier transform to generate a spectrum. In the spectrum, a characteristic frequency f_c that is distinct from the white noise background is identified; The amplitude A of the characteristic frequency f_c is monitored in real time and compared with the preset safety threshold A_max.

10. A method for testing the high-temperature electrical properties of insulating materials according to claim 6, characterized in that: The step-increase test voltage is applied by gradually increasing the voltage step by step with a preset voltage step size ΔU, and maintaining each voltage step for a preset duration t until the stopping condition is met or the upper limit of the output voltage of the test instrument is reached.

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