Wide temperature range temperature control system for sheet insulation material electric heat coupling aging test

Abstract

This invention relates to the field of performance testing of insulating materials for power equipment, specifically disclosing a wide-range temperature control system for electrothermal coupling aging tests of sheet insulating materials. The system includes a test chamber body with a sealed, insulated inner cavity; multiple electrode modules disposed within the cavity for holding the sample; upper and lower heating modules respectively disposed above and below the electrode modules; a peripheral compensation heating module located on the side wall of the cavity; a multi-point temperature acquisition unit containing multiple temperature sensors disposed at different positions within the cavity; and a wide-range closed-loop control unit electrically connected to each heating module and the temperature acquisition unit. This control unit independently controls the heating power of each heating module based on feedback signals from each temperature sensor. This invention, through the combination of zoned heating and multi-point temperature control, achieves independent zoned heating and dynamic compensation for sample thickness and in-plane direction, effectively solving the problems of uneven heating and electrode heat sinking, and ensuring uniform and stable temperature in the test area.

Description

Technical Field

[0001] This invention relates to the field of performance testing of insulating materials for power equipment, and in particular to a wide-range temperature control system for electrothermal coupling aging test of sheet insulating materials. Background Technology

[0002] In the field of high-voltage electrical engineering, the long-term operational reliability of insulating materials is a key factor determining the safety and stability of power equipment. For applications such as high-voltage direct current transmission systems, power electronic converters, and new energy grid-connected equipment, their internal insulation structures are subjected to complex conditions of coupled electric and thermal fields for extended periods, resulting in significant electrothermal coupling characteristics in material performance degradation. Therefore, conducting precise electrothermal coupling aging tests is crucial for revealing the failure mechanisms of insulating materials, establishing accurate lifetime prediction models, and optimizing insulation structure design.

[0003] Semi-crystalline thermoplastic polyolefin materials, such as cross-linked polyethylene (XLPE) and polypropylene (PP), are widely used as insulation for high-voltage cables, DC bushings, and power electronic equipment due to their excellent electrical properties, chemical resistance, and processability. The microstructure of these materials consists of both crystalline and amorphous regions and is extremely sensitive to temperature changes. Under the influence of an electric field, the migration of charge carriers, the accumulation of space charge, and the electrical conductivity within the material are all closely related to its microstructure. Therefore, to realistically simulate actual operating conditions and accurately evaluate the aging behavior of materials, electrothermal coupled accelerated aging tests must be conducted under precisely controlled temperature and electric field conditions.

[0004] It is particularly important to note that the thermal response behavior of these materials exhibits distinct stages. For example, when the temperature exceeds approximately 80°C, structural relaxation and rearrangement begin to occur in their crystalline regions; when the temperature rises above 120°C, the material may soften, with a decrease in elastic modulus accompanied by microscopic deformation. Within this critical temperature range, even minute temperature fluctuations can lead to changes in material thickness, thereby causing distortion in the electric field distribution and significantly affecting the space charge dynamics and local conductivity, ultimately resulting in increased dispersion in aging test results. Therefore, in electrothermal coupling experiments, extremely high precision and uniformity in temperature field control are crucial, as they are a decisive prerequisite for obtaining reliable and repeatable experimental data.

[0005] However, most commonly used aging test systems employ single-zone centralized heating or overall box-type heating schemes. These traditional structures typically place the heating element in a single location or on the side wall of the cavity, relying on heat conduction and natural convection to slowly heat the entire cavity. This heating method has inherent drawbacks: First, due to factors such as cavity geometry, uneven heat radiation, and airflow, it is difficult to form a uniform temperature field inside the cavity, resulting in a persistent temperature difference between the center and edge regions of the sample. Second, the metal electrodes used in the test, due to their much higher thermal conductivity than the tested insulating material, create a significant "heat sink" effect, causing the temperature at the electrode-sample contact area to be significantly lower than the set value, resulting in localized cold spots. This temperature non-uniformity not only distorts the true temperature distribution inside the sample but also leads to uneven electric field distribution due to the coupling effect of thermo-electricity, severely interfering with the accurate analysis of the material aging mechanism.

[0006] Furthermore, existing temperature control systems employ relatively simple control strategies with limited response speeds, making it difficult to achieve stable and precisely settable heating rates. Unstable heating processes can lead to thermal stress concentration or microstructural abrupt changes in materials when crossing critical phase transition temperature ranges, affecting the stability of subsequent electrical performance tests. More importantly, traditional systems struggle to maintain long-term temperature stability over a wide temperature range from room temperature to high temperatures (e.g., 200°C), especially under conditions where the sample is energized (an electric field is applied). As temperature increases, the thermophysical parameters of the material and equipment undergo nonlinear changes, while Joule heating generated within the sample introduces additional, dynamic thermal disturbances. The lack of zoned, independent temperature monitoring and feedback adjustment mechanisms prevents the system from compensating for these disturbances in a timely manner, easily leading to temperature drift or oscillations, resulting in insufficient reliability of long-term steady-state aging test data under wide temperature ranges and energized conditions.

[0007] In summary, existing technologies for electrothermal coupling aging tests on sheet-like insulating materials such as semi-crystalline polyolefins suffer from the following shortcomings: 1) The heating method is singular, making it difficult to ensure temperature uniformity within the sample surface and along its thickness; 2) Local temperature drops caused by electrode thermal conductivity are not adequately considered; 3) The heating rate control accuracy is poor, failing to meet the needs of material phase transformation research; 4) The system's temperature control stability is insufficient over a wide temperature range and under energized conditions. These problems directly limit the accuracy and engineering guidance value of electrothermal coupling aging tests. Therefore, there is an urgent need in this field for a heating control system capable of achieving high uniformity and high stability temperature control, and dynamically and accurately compensating for electrode areas. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a wide-temperature-range temperature control system for electrothermal coupling aging tests of sheet-like insulating materials. Compared to traditional electrothermal aging systems, this system has a more uniform internal temperature distribution, a more uniform temperature gradient in the electrode area, and can achieve stable control over a wide temperature range, effectively improving the stability and repeatability of electrothermal coupling aging tests.

[0009] To achieve the above objectives, the present invention provides the following solution: a wide-range temperature control system for electrothermal coupling aging tests of sheet insulating materials, comprising: a test chamber body having a sealed and heat-insulating inner cavity; multiple electrode modules disposed in the inner cavity for clamping the sheet insulating material sample to be tested; an upper heating module and a lower heating module respectively disposed above and below the electrode modules; a peripheral compensation heating module disposed on the side wall of the inner cavity; a multi-point temperature acquisition unit including multiple temperature sensors disposed at different positions within the inner cavity; and a wide-range closed-loop control unit electrically connected to the upper heating module, the lower heating module, the peripheral compensation heating module, and the multi-point temperature acquisition unit, for independently controlling the heating power of the upper heating module, the lower heating module, and the peripheral compensation heating module based on the feedback signals from each temperature sensor.

[0010] Optionally, the electrode module includes multiple pairs of upper and lower electrodes arranged opposite each other, which together form an array-type test station.

[0011] Optionally, the upper and lower electrodes are made of copper and are fixed to the inner cavity by an alumina ceramic insulating support.

[0012] Optionally, the upper heating module is attached to the lower surface of the support plate of the upper electrode, and the lower heating module is attached to the upper surface of the support plate of the lower electrode.

[0013] Optionally, the upper heating module and the lower heating module are flexible thin-film heating elements.

[0014] Optionally, the peripheral compensation heating module is an armored heating wire embedded in the groove of the inner cavity sidewall.

[0015] Optionally, the multi-point temperature acquisition unit includes: The first temperature sensor is embedded in the support plate of the upper electrode; The second temperature sensor is embedded in the support plate of the lower electrode; The third temperature sensor is located at the geometric center of the inner cavity. The fourth temperature sensor is located on the side wall of the inner cavity near the edge of the sample.

[0016] Furthermore, the wide-temperature-range closed-loop control unit employs a hierarchical PID control strategy, including: The main PID control loop adjusts the total output power of the upper heating module and the lower heating module based on the reading of the third temperature sensor. The first compensation control loop uses the difference between the fourth temperature sensor and the third temperature sensor as input to adjust the power of the peripheral compensation heating module. The second compensation control loop uses the difference between the first temperature sensor and the third temperature sensor as input to fine-tune the power of the upper heating module. The third compensation control loop uses the difference between the second and third temperature sensors as input to fine-tune the power of the lower heating module.

[0017] Furthermore, the wide-temperature-range closed-loop control unit can achieve precise setting and control of the heating rate within the range of 0.5℃ / min to 5℃ / min.

[0018] Optionally, the inner wall of the inner cavity of the test chamber body is wrapped with a thermal insulation layer, which is a ceramic fiber insulation material.

[0019] Optionally, the wide-temperature-range temperature control system for electrothermal coupling aging test of sheet insulation material further includes a forced circulation temperature equalization module disposed in the inner cavity, used to form a circulating airflow in the inner cavity to enhance the uniformity of the temperature field.

[0020] Optionally, the forced circulation temperature equalization module includes at least one circulating fan disposed on the rear side of the inner cavity of the test chamber body. The air outlet of the circulating fan is connected to a uniform flow duct extending to the top of the cavity, and the uniform flow duct has uniformly distributed air outlet holes on its front side.

[0021] Furthermore, the wide-temperature-range temperature control system for the electrothermal coupling aging test of the sheet insulation material also includes an external DC high-voltage power supply and a high-voltage insulating sleeve. The high-voltage insulating sleeve is used to safely introduce the high voltage generated by the external DC high-voltage power supply into the inner cavity and connect it to the electrode module.

[0022] Compared with the prior art, the present invention discloses at least the following beneficial effects: This invention proposes a wide-temperature-range temperature control system for electrothermal coupling aging tests of sheet-like insulating materials. This system can achieve stable temperature control within a range from room temperature to 200°C. It can independently control the temperature of the sample surface and along its thickness, and dynamically compensate for local temperature drops caused by electrode thermal conductivity. Ultimately, it can maintain a stable temperature field under energized electrothermal coupling test conditions. This system solves the technical problems existing in current electrothermal coupling tests, such as uneven temperature distribution, insufficient temperature compensation in the electrode area, difficulty in controlling the heating rate, and poor stability over a wide temperature range. It can meet the technical requirements of the electrical engineering field for high-precision electrothermal coupling aging test equipment. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of the device of the present invention; Reference numerals in the attached diagram: 1. Test chamber body; 2. Upper heating module; 3. Electrode module; 4. Peripheral compensation heating module; 5. Thermal insulation layer; 6. Lower heating module; 7. External DC high voltage power supply; 8. High voltage insulating sleeve; 9. Circulating fan. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Reference Figure 1 As shown, this embodiment provides a wide-range temperature control system for electrothermal coupling aging tests of sheet insulation materials. The system is designed to provide a highly uniform and stable temperature environment for sheet insulation materials (especially sheet-like semi-crystalline thermoplastic polyolefin materials with a thickness of 0.05 mm to 1 mm, such as cross-linked polyethylene XLPE and polypropylene PP) in the range of room temperature to 200°C under the condition of applying a DC high voltage electric field.

[0028] In this embodiment, the temperature control system includes a test chamber body 1, an upper heating module 2, an electrode module 3, a peripheral compensation heating module 4, a thermal insulation layer 5, a lower heating module 6, an external DC high-voltage power supply 7, a high-voltage insulating sleeve 8, and a circulating fan 9.

[0029] In one specific embodiment, the test chamber body 1 constitutes the main support and housing structure of the system. The test chamber body 1 forms the system's double-layer heating chamber unit. Inside, there is an inner high-thermal-conductivity metal chamber made of a high-thermal-conductivity metal material (e.g., aluminum alloy) to form a sealed test space. The outer side of the inner high-thermal-conductivity metal chamber is tightly wrapped with the thermal insulation layer 5. The thermal insulation layer 5 is made of ceramic fiber felt and has a thickness of 30 mm. This structure minimizes heat loss from the test chamber to the external environment, providing a basis for precise temperature control over a wide temperature range.

[0030] Based on the above embodiments, the electrode module 3 is further disposed in the inner cavity of the test chamber body 1. Specifically, in this embodiment, multiple sets of electrode modules 3 are provided, each set of electrode modules 3 including several pairs of upper and lower electrodes arranged vertically opposite each other, together forming an array-type test station. The upper and lower electrodes are used to clamp the sheet-like insulating material sample to be tested.

[0031] In one specific embodiment, the inner cavity of the test chamber body 1 is provided with 16 pairs of array-type test stations consisting of upper and lower electrodes, with a 0.2 mm thick polypropylene insulating sample sandwiched between each pair of electrodes. The electrodes are fixed to the inside of the inner high thermal conductivity metal cavity by a high-temperature resistant insulating support structure, and a thermal insulation layer 5 is provided on the outside of the cavity to reduce heat loss.

[0032] Based on the above embodiments, the upper and lower electrodes are further made of copper and fixed to the inner cavity by an alumina ceramic insulating support.

[0033] In this embodiment, the temperature control system includes a multi-zone independent heating unit, which is divided into three independent temperature control zones along the sample thickness direction and in-plane direction: the upper electrode zone, the lower electrode zone, and the peripheral compensation zone. Main heating units are located in the upper and lower electrode zones, and a peripheral compensation heating unit is located in the peripheral compensation zone.

[0034] In one specific embodiment, the upper heating module 2 and the lower heating module 6 serve as the main heating units, and are respectively disposed above and below the electrode array. Specifically, the upper heating module 2 is attached to the lower surface of the ceramic support plate of the upper electrode; the lower heating module 6 is attached to the upper surface of the ceramic support plate of the lower electrode.

[0035] Based on the above embodiments, both the upper heating module 2 and the lower heating module 6 are preferably flexible thin-film heating sheets, whose shapes match the electrode support plate, and their heating power can be adjusted through independent circuits. Their main function is to provide primary heating in the thickness direction of the sample and directly compensate for the heating of the electrode module 3 to counteract the heat sink effect of the electrode.

[0036] In one specific embodiment, the peripheral compensation heating module 4 is disposed on the side wall of the inner cavity and arranged around the cavity in a circumferential manner to form a peripheral compensation heating unit.

[0037] Based on the above embodiments, the peripheral compensation heating module 4 is further defined as an armored heating wire embedded in a groove in the cavity wall. Its heating power is independent of the upper heating module 2 and the lower heating module 6, forming a third independent temperature control zone to compensate for heat dissipation at the edge of the cavity and ensure the uniformity of temperature within the sample surface.

[0038] The upper heating module 2, lower heating module 6 and peripheral compensation heating module 4 are thermally isolated from each other and are each connected to an independent power regulator, which is independently controlled by the wide temperature range closed-loop control unit.

[0039] The temperature control system in this embodiment also includes a forced circulation temperature equalization module. In one specific embodiment, the circulating fan 9 serves as the forced circulation temperature equalization module and is located on the rear side of the inner cavity of the test chamber body 1. The circulating fan 9 is a low-speed centrifugal fan, and its outlet is connected to a uniform airflow duct. The uniform airflow duct extends to the top of the cavity and has evenly distributed air outlets on its front side, thereby forming a low-speed, controllable circulating airflow within the cavity, breaking the temperature stratification formed by natural convection, and enhancing the uniformity of the temperature field.

[0040] In this embodiment, temperature control is achieved through a wide-range closed-loop control unit integrated inside the test chamber body 1. The core of this wide-range closed-loop control unit is a multivariable PID controller. Temperature signal acquisition relies on a multi-point temperature acquisition unit, which includes multiple Pt100 platinum resistance temperature sensors (not shown in the figure).

[0041] In one specific embodiment, the temperature sensors are arranged as follows: a first temperature sensor is embedded in the ceramic support plate of the upper electrode; a second temperature sensor is embedded in the ceramic support plate of the lower electrode; a third temperature sensor is located at the geometric center of the cavity; and a fourth temperature sensor is located on the side wall of the cavity near the edge of the sample. All temperature sensor signals are connected to a wide-temperature-range closed-loop control unit.

[0042] In a preferred closed-loop control strategy, the system employs a hierarchical control architecture: First, using the reading of the third temperature sensor as a global reference, a main PID control loop adjusts the total output power of the upper heating module 2 and the lower heating module 6. Second, using the difference between the fourth and third temperature sensors as input, an independent compensation PID loop adjusts the power of the peripheral compensation heating module 4. Finally, using the differences between the first and second temperature sensors and the third temperature sensor as input, two additional independent compensation PID loops fine-tune the compensation power components of the upper heating module 2 and the lower heating module 6, dynamically offsetting the heat sink effect of the electrodes.

[0043] Specifically, the wide-temperature-range closed-loop control unit adopts a hierarchical PID control strategy, including: a main PID control loop, which adjusts the total output power of the upper heating module 2 and the lower heating module 6 based on the reading of the third temperature sensor; a first compensation control loop, which adjusts the power of the peripheral compensation heating module 4 based on the difference between the fourth and third temperature sensors; a second compensation control loop, which fine-tunes the power of the upper heating module 2 based on the difference between the first and third temperature sensors; and a third compensation control loop, which fine-tunes the power of the lower heating module 6 based on the difference between the second and third temperature sensors.

[0044] Furthermore, the wide-temperature-range closed-loop control unit can achieve precise and adjustable heating rate control, and the user can set the target heating rate in the range of 0.5℃ / min to 5℃ / min.

[0045] In one specific embodiment, the electric field loading is provided by an external DC high-voltage power supply 7. The high-voltage electricity is safely introduced into the cavity from the top of the test chamber body 1 through a high-voltage insulating sleeve 8 and connected to the electrode module 3 via a shielded high-voltage cable. A grounded metal shielding mesh (not shown in the figure) is provided around the array of electrode modules 3. This shielding mesh is reliably connected to the device housing and protective ground to achieve electromagnetic isolation between the high-voltage test area and the low-voltage control area.

[0046] The temperature control system in this embodiment, through the coordinated design and control of the aforementioned independent heating structure, dynamic temperature compensation structure, multi-point temperature measurement structure, and forced airflow temperature equalization structure, can operate stably for a long period within a wide temperature range from room temperature to 200℃. Actual measurements show that the system's steady-state temperature control accuracy can reach ±0.5℃, and the steady-state temperature fluctuation does not exceed ±1℃. Under steady-state conditions, the in-plane temperature uniformity within the effective area of ​​the sample can achieve a temperature difference of no more than ±1.5℃ between any two points. The system possesses excellent long-term operational reliability and can support continuous aging tests for more than 1500 hours. This system is particularly suitable for long-term electrothermal coupling aging tests of sheet-like polyolefin insulation materials with a thickness ranging from 0.1mm to 0.5mm, providing a reliable hardware platform for obtaining highly repeatable and comparable aging data.

[0047] It should be understood that the number of electrode modules 3, the specific form of the heating module (such as changing it to a heating rod or silicone heating plate), the type of insulation material (such as changing it to aerogel), the type and location of the fan, etc., described in the above embodiments can all be adjusted and changed according to the specific test capacity, sample size and other actual needs. These modifications and improvements based on the core concept of this invention should all fall within the protection scope of this invention.

[0048] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0049] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A wide temperature range temperature control system for sheet insulation material electrothermal coupling aging test, characterized in that, include: The test chamber body (1) has a sealed and heat-insulating inner cavity; Multiple electrode modules (3) are disposed in the inner cavity for holding the sheet-like insulating material sample to be tested; The upper heating module (2) and the lower heating module (6) are respectively disposed above and below the electrode module (3); Peripheral compensation heating module (4) is disposed on the side wall of the inner cavity; The multi-point temperature acquisition unit includes multiple temperature sensors located at different positions within the inner cavity; The wide-temperature-range closed-loop control unit is electrically connected to the upper heating module (2), the lower heating module (6), the peripheral compensation heating module (4) and the multi-point temperature acquisition unit, and is used to independently control the heating power of the upper heating module (2), the lower heating module (6) and the peripheral compensation heating module (4) according to the feedback signals of each temperature sensor.

2. The wide temperature range temperature control system for the sheet insulation material electrothermal coupling aging test according to claim 1, characterized in that, The electrode module (3) includes multiple pairs of upper and lower electrodes arranged opposite each other, which together form an array-type test station.

3. The wide temperature range temperature control system for the sheet insulation material electrothermal coupling aging test according to claim 2, characterized in that, The upper and lower electrodes are made of copper and are fixed to the inner cavity by an alumina ceramic insulating support.

4. The wide temperature range temperature control system for the sheet insulation material electrothermal coupling aging test according to claim 2, characterized in that, The upper heating module (2) is attached to the lower surface of the support plate of the upper electrode, and the lower heating module (6) is attached to the upper surface of the support plate of the lower electrode.

5. The wide temperature range temperature control system for the sheet insulation material electrothermal coupling aging test according to claim 1 or 4, characterized in that, The upper heating module (2) and the lower heating module (6) are flexible thin-film heating sheets.

6. The wide-range temperature control system for electrothermal coupling aging test of sheet insulation materials according to claim 1, characterized in that, The peripheral compensation heating module (4) is an armored heating wire embedded in the groove of the inner cavity side wall.

7. The wide-temperature-range temperature control system for electrothermal coupling aging test of sheet insulation materials according to claim 2, characterized in that, The multi-point temperature acquisition unit includes: The first temperature sensor is embedded in the support plate of the upper electrode; The second temperature sensor is embedded in the support plate of the lower electrode; The third temperature sensor is located at the geometric center of the inner cavity. The fourth temperature sensor is located on the side wall of the inner cavity near the edge of the sample.

8. The wide-range temperature control system for electrothermal coupling aging test of sheet insulation materials according to claim 1, characterized in that, The inner wall of the inner cavity of the test chamber body (1) is wrapped with a thermal insulation layer (5), which is a ceramic fiber thermal insulation material.

9. The wide-temperature-range temperature control system for electrothermal coupling aging test of sheet insulation materials according to claim 1, characterized in that, It also includes a forced circulation temperature equalization module disposed in the inner cavity, which is used to form a circulating airflow in the inner cavity to enhance the uniformity of the temperature field.

10. The wide-range temperature control system for electrothermal coupling aging test of sheet insulation materials according to claim 9, characterized in that, The forced circulation temperature equalization module includes at least one circulating fan (9) located on the rear side of the inner cavity of the test chamber body (1). The air outlet of the circulating fan (9) is connected to a uniform flow duct extending to the top of the cavity. The uniform flow duct has uniformly distributed air outlet holes on its front side.

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