Adjustable field intensity direct current loading device for electrical cable insulation sheet sample electrothermal aging

Abstract

The application discloses a kind of adjustable field intensity direct current loading device for cable insulation sheet sample electrothermal aging, belong to the field of high-voltage insulation material test, comprising: electric field target setting unit, sample state acquisition unit, electric field regulation and control unit, voltage output adjustment unit and electrode application unit.Sample state acquisition unit real-time collection sample thickness and other geometric parameters, electric field regulation and control unit according to target electric field intensity and real-time thickness dynamically calculates the required voltage, and controls voltage output adjustment unit to correct, so that the electric field in the sample interior remains constant during electrothermal aging process.The application eliminates the electric field deviation caused by sample processing error, thermal expansion or creep deformation through closed-loop control mechanism, significantly improves the accuracy and repeatability of aging test, and is suitable for electrothermal coupling aging research of high-voltage direct current cable insulation material.

Description

Technical Field

[0001] This invention belongs to the field of high voltage insulation material testing, and in particular relates to an adjustable field strength DC loading device for electrothermal aging of cable insulation sheet samples. Background Technology

[0002] High-voltage direct current (HVDC) cables, due to their low-loss advantage in long-distance, high-capacity power transmission, have become key equipment for offshore wind power grid connection and inter-regional power grid interconnection. With increasing service life, the cable insulation layer inevitably experiences performance degradation under the combined effects of long-term high-intensity DC electric stress and temperature rise caused by conductor heating. To assess the long-term reliability of the insulation material, electrothermal coupling aging tests need to be conducted under laboratory conditions. In existing technologies, a fixed voltage loading method is typically used, that is, a preset voltage is applied based on the nominal thickness of the sample to calculate the theoretical electric field strength.

[0003] However, the fixed voltage loading method has significant drawbacks in actual experiments. First, the sample itself may have processing errors, clamping deviations, or local thickness inhomogeneities, leading to a static deviation between the theoretical electric field calculated based on the nominal thickness and the actual electric field. Second, under electrothermal coupling conditions, especially for semi-crystalline polyolefin materials, high temperatures can cause thermal expansion, softening, or creep deformation of the sample, resulting in dynamic changes in the sample thickness or effective electrode spacing, causing the actual electric field strength to continuously deviate from the preset target value. In high-field aging tests, even small fluctuations in electric field strength can directly affect key physical processes such as carrier injection and space charge accumulation, leading to inaccurate aging rate assessments or increased dispersion in experimental data. Existing devices, lacking real-time thickness monitoring and feedback adjustment mechanisms, cannot maintain a constant electric field during sample state changes, thus hindering the development of high-precision electrothermal aging research. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides an adjustable DC loading device for electrothermal aging of sheet-like cable insulation samples, comprising: Electric field target setting unit, used to set the target electric field physical quantity; The sample state acquisition unit is used to acquire geometric parameters that affect the electric field distribution inside the sample. An electric field control unit, connected to the electric field target setting unit and the sample state acquisition unit, is used to establish an electric field control model based on the target electric field physical quantities and the geometric parameters, and to generate a voltage regulation control signal. A voltage output regulation unit, connected to the electric field regulation unit, is used to regulate the output voltage according to the control signal; An electrode application unit, connected to the voltage output adjustment unit, is used to apply the output voltage to both sides of the sample; When the state of the sample changes, the electric field control unit corrects the voltage output according to the dynamic changes of the geometric parameters in order to maintain the target electric field state constant.

[0005] Optionally, the geometric parameters acquired by the sample state acquisition unit include the sample thickness, and the electric field control unit determines the equivalent electrode spacing based on the sample thickness and calculates the corresponding target output voltage based on the target electric field physical quantity.

[0006] Optionally, the sample state acquisition unit also acquires thermal expansion deformation parameters or structural disturbance parameters, and the electric field control unit corrects the equivalent electrode spacing based on the thermal expansion deformation parameters or structural disturbance parameters, and determines the final voltage regulation control signal based on the real-time measured thickness.

[0007] Optionally, the sample state acquisition unit includes a non-contact thickness measurement device and a contact displacement detection device, and the electric field control unit selects the corresponding measurement method according to the sample temperature state or operating stage, and acquires the corresponding geometric parameters.

[0008] Optionally, the electric field control unit controls the voltage output regulation unit to switch between continuous regulation mode and graded regulation mode according to the rate of change of the geometric parameters or the operating stage, so as to generate a corresponding voltage regulation control signal.

[0009] Optionally, the electric field control unit further determines a voltage error threshold based on the target electric field physical quantity and the equivalent electrode spacing, and controls the deviation between the actual output voltage and the target voltage within the voltage error threshold range in each control cycle.

[0010] Optionally, the electric field control unit may also adaptively adjust the length of the control cycle or the voltage adjustment step according to the rate of change of geometric parameters or the rate of change of temperature.

[0011] Optionally, the electrode application unit includes an upper and lower electrode structure and a voltage equalization ring structure. The voltage equalization ring is used to optimize the electric field distribution at the electrode edge and does not participate in voltage regulation as a closed-loop control variable.

[0012] Optionally, it also includes a circuit protection device. A status monitoring interface is provided between the electric field control unit and the circuit protection device. When the protection circuit is triggered, the electric field control unit suspends closed-loop regulation and switches to a safe step-down mode.

[0013] Optionally, the electric field control unit further includes a control algorithm module, which is used to adaptively correct the output voltage according to the real-time changes of the geometric parameters, and to execute a closed-loop control process of thickness acquisition, voltage calculation, error judgment and voltage output in each control cycle.

[0014] Compared with the prior art, the present invention has the following advantages and technical effects: This invention introduces a closed-loop electric field control mechanism, which dynamically adjusts the applied voltage based on the real-time geometric parameters of the sample, effectively eliminating electric field deviations caused by sample processing errors, clamping deviations, and thermally induced deformation. This device achieves precise and constant electric field strength loading, avoiding misjudgments of aging rates due to thickness fluctuations, and significantly improving the accuracy and data repeatability of electrothermal coupling aging tests. It is applicable to sheet insulation materials of varying thicknesses and within a wide electric field strength range, providing a stable and reliable test platform for the long-term aging mechanism research and life assessment of high-voltage DC cable insulation materials. Attached Figure Description

[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the device according to an embodiment of the present invention; Figure 2 This is a complete working principle diagram of the device according to an embodiment of the present invention; Figure 3 This is a complete flowchart of the device according to an embodiment of the present invention. Detailed Implementation

[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0017] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0018] Example 1 like Figure 1 As shown, this embodiment provides an adjustable DC loading device for electrothermal aging of sheet-like cable insulation samples, comprising: The system comprises an electric field target setting unit, a sample state acquisition unit, an electric field closed-loop control unit, a voltage output adjustment unit, and an electrode application unit. The electric field closed-loop control unit is electrically connected to the electric field target setting unit, the sample state acquisition unit, and the voltage output adjustment unit, respectively, and is used to generate a voltage adjustment signal based on the target electric field physical quantity and the sample state parameters. The voltage output adjustment unit is connected to the electrode application unit and is used to apply an adjustable DC voltage to the sample.

[0019] The electric field target setting unit is used to set the target electric field strength or electric field-related physical quantities required for the test, and transmits the setting signal to the electric field closed-loop control unit.

[0020] The sample state acquisition unit is used to acquire state parameters that affect the electric field distribution inside the sample. The state parameters include at least one of sample thickness, geometric dimension change, thermal deformation parameters or structural disturbance parameters, and transmits the state parameters to the electric field closed-loop control unit.

[0021] The electric field closed-loop control unit is used to establish an electric field control model based on the target electric field physical quantity and the state parameters, calculate the corresponding voltage regulation amount according to the model, and output the voltage regulation signal to the voltage output regulation unit.

[0022] The electric field modulation model is based on the physical relationship between the average electric field strength inside the sample under parallel plate electrodes and the applied voltage. For the effective distance between the electrodes... For a sheet-like sample, when the influence of the edge field is neglected and the electrode region satisfies the uniform field condition, the average electric field intensity inside the sample is... With applied voltage satisfy: ; Therefore, when the target electric field strength is set to To maintain a constant electric field inside the sample, the output voltage must change with the thickness in real time to satisfy the following: ; Furthermore, the system calibration term, the change in inter-electrode spacing, is introduced. Then the target output voltage can be expressed as: ; in The correction amount is based on the sample thickness as the main parameter and the thermal expansion coefficient as an auxiliary parameter during actual operation. ; in This represents the actual measured change in thickness. This is the correction for thermal expansion caused by temperature changes. The correction factor is a structural or clamping disturbance correction factor, which can be predetermined during the device calibration phase, when other correction factors are very small to almost negligible. .

[0023] The voltage output adjustment unit is a programmable high-voltage DC power supply or a high-voltage adjustment module, whose output voltage is continuously adjustable, and is used to provide the corresponding DC voltage to the electrode application unit according to the voltage adjustment signal.

[0024] The continuous adjustment mode is suitable for slow thickness changes or when the field is maintained in a constant field. In this case, the voltage is continuously corrected in small steps to improve the stability of the electric field. The graded adjustment mode is suitable for the voltage boosting stage or the stage of sudden thickness change. At this time, the voltage is adjusted according to the preset step amplitude to improve the system response speed. The mode switching is automatically completed by the electric field closed-loop control unit based on the thickness change or the operation stage indicator.

[0025] The electrode application unit includes an upper electrode and a lower electrode structure, which are used to form an electric field environment on both sides of the sample, so that an electric field state corresponding to the target electric field physical quantity is established inside the sample.

[0026] When the sample state parameters change, the electric field closed-loop control unit dynamically corrects the voltage output to keep the deviation between the actual electric field inside the sample and the target electric field within a preset error range.

[0027] Furthermore, the sample state acquisition unit includes a non-contact thickness measurement device or a contact displacement detection device, used to acquire sample thickness change information in real time.

[0028] When the sample is in the high-temperature electrothermal coupling aging stage or the material softens and deforms, in order to avoid the contact measuring device from applying additional mechanical disturbance to the sample, a non-contact measuring method is preferred. When the sample is in the initial stage of loading at room temperature or pressurization, the material structure is stable, and the measurement accuracy requirement is high, the contact displacement detection method is preferred. Between different operating phases, the electric field closed-loop control unit can automatically switch the measurement mode based on the temperature signal or the operating phase indicator.

[0029] Furthermore, the electric field closed-loop control unit includes a microprocessor and a control algorithm module, which is used to adaptively adjust the voltage output according to changes in the sample state.

[0030] Furthermore, the device is suitable for sheet-like insulating materials with a thickness range of 0.1 mm to 1 mm, and can achieve stable control within a target electric field strength range of 0 to 50 kV / mm.

[0031] Example 2 like Figure 2 and Figure 3 As shown, this embodiment provides an adjustable DC loading device for electrothermal aging of sheet-like cable insulation samples, comprising: The system includes an electric field target setting unit, a sample state acquisition unit, an electric field closed-loop control unit, a voltage output adjustment unit, and an electrode application unit.

[0032] The voltage output adjustment unit is a high-voltage DC generator housing, which includes a voltage adjustment knob, a leakage current display, and a voltage display meter.

[0033] The high-voltage lead is connected to the high-voltage DC generator housing via a circuit breaker.

[0034] The equalizing ring is located at the connection between the high-voltage lead and the upper electrode. It is used to optimize the electric field distribution at the electrode edge, reduce the edge field enhancement effect, and make the electric field inside the sample more uniform. The equalizing ring is a passive electric field homogenization structure. Its geometric dimensions and installation position are determined during the device design stage and it is not used as a closed-loop control object. The control objective of the electric field closed-loop control unit is the average electric field strength inside the sample, and it does not use the uniformity of the electric field spatial distribution as a real-time adjustment parameter.

[0035] The electric field closed-loop control unit includes a microprocessor controller and a control algorithm module, which is used to receive the electric field target signal and the sample state parameter signal, and generate a voltage regulation signal.

[0036] The sample status acquisition form includes a thickness measurement module, which is used to measure the sample thickness d in real time.

[0037] The thickness measurement module is a laser displacement sensor or a capacitive displacement sensor, and its output signal is input to the electric field closed-loop control unit.

[0038] The electrode application unit includes a support structure, a conductive structure, and a fixing structure. The equalizing ring is used to improve the electric field distribution at the electrode edge, making the electric field within the effective area of ​​the sample nearly uniform, thereby improving the control accuracy based on the average electric field model.

[0039] The equalizing ring is a structural electric field optimization component. It does not participate in dynamic voltage regulation and is not included in the calculation parameters of the electric field closed-loop control model.

[0040] The support structure includes an upper support plate and a lower support plate, which are arranged at relative intervals.

[0041] The support connects the upper and lower supports and is used to adjust the electrode spacing.

[0042] The conductive structure includes an upper electrode and a lower electrode, with the lower electrode fixedly connected to the lower support plate and the upper electrode connected to the upper support plate.

[0043] The sample is placed on the lower electrode, and the upper electrode and the lower electrode clamp the sample.

[0044] Both the upper and lower electrodes are parallel plate electrode structures, with a preferred electrode diameter of 65 mm.

[0045] The fixing fixture is used to fix the edge of the sample to prevent displacement or warping during loading.

[0046] Circuit protection devices include a current-limiting resistor and an inductor connected in series to limit the rate of current rise in the event of a transient overcurrent or breakdown event. The circuit protection device is electrically connected to the voltage output regulation unit and the electric field closed-loop control unit. The electric field closed-loop control unit monitors the status of the protection circuit through current detection signals or voltage abnormality signals.

[0047] In the device, the electric field target setting unit is used to set the target electric field strength E, and the target electric field range is 0-50kV / mm.

[0048] The electric field closed-loop control unit establishes a mapping relationship between voltage and electric field based on the real-time thickness d and the target electric field strength E, and generates a voltage regulation signal.

[0049] When the thickness of the sample changes, the electric field closed-loop control unit updates the voltage adjustment signal in real time to keep the electric field inside the sample within the preset error range.

[0050] When any of the following abnormal conditions are detected: the output current exceeds the preset overcurrent threshold; the voltage drop or rise exceeds the preset range; or the leakage current increases abnormally; The electric field closed-loop control unit determines that the protection is triggered and executes the following control strategy: (1) Immediately suspend the voltage closed-loop regulation operation; (2) Switch to safe buck mode to make the output voltage decrease at a preset slope; (3) Record abnormal status parameters; (4) Re-enter the closed-loop control mode after the abnormality is resolved.

[0051] The protection trigger state does not directly cut off the power output, but instead prioritizes entering the controlled voltage reduction mode to avoid the voltage drop causing secondary disturbance to the sample; when the abnormality persists, the system performs a power shutdown operation.

[0052] The allowable deviation range of the target electric field The accuracy requirements are preset according to the test, for example, ±1% to ±5% of the target electric field strength E0.

[0053] The corresponding voltage error threshold ε is: ; in, This is the allowable deviation ratio of the electric field. This represents the actual electrode spacing.

[0054] The electric field control unit controls the output voltage to ensure that the actual electric field satisfies the following: ; The electric field closed-loop control unit performs closed-loop adjustment according to a fixed control period T, which is a preset time interval within the range of 10ms–1000ms.

[0055] The following control flow is executed sequentially within each control cycle: (1) Thickness acquisition stage: The sample state acquisition unit collects the current thickness value d(t) of the sample in real time and transmits it synchronously to the electric field closed-loop control unit through the analog-to-digital conversion interface; (2) Voltage calculation stage: The electric field closed-loop control unit is based on the target electric field strength E0 and the current thickness d(t), according to the relationship between electric field and voltage: Calculate the target output voltage U(t) for the current cycle; (3) Error judgment stage: The electric field closed-loop control unit compares the calculated target voltage U(t) with the current power supply output voltage U0(t) to obtain the voltage deviation ΔU; (4) Adjusting the output stage: When |ΔU| exceeds the preset error threshold ε, a voltage regulation signal is generated and sent to the voltage output regulation unit; (5) Voltage application stage: The voltage output adjustment unit completes the output voltage correction in the next control cycle and applies it to both ends of the sample via the electrode application unit.

[0056] The electrothermal aging test method for insulating materials includes the following steps: Step 1: Select the semi-crystalline polyolefin insulation material to be tested and process it into a sheet sample with a thickness of 0.20 mm and a diameter of 100 mm using a flat vulcanizing apparatus.

[0057] Step 2: Clean the sample with ethanol in an ultrasonic cleaner for 30 minutes to remove processing residues.

[0058] Step 3: Place the cleaned sample in a 70 ℃ constant temperature chamber for 24 hours to eliminate internal residual stress and allow the material thickness to reach a stable state in a free state. This step is used to improve the repeatability of subsequent thickness measurements, but is not used as the final reference thickness for electric field control.

[0059] Step 4: Place the sample between the upper and lower electrodes, flatten and fix the sample edges using the clamping fixture to ensure no warping. After clamping, maintain constant clamping pressure and activate the thickness measurement module to measure the real-time thickness d0 under clamping conditions. d0 serves as the initial reference thickness for electric field control. Clamping pressure may cause slight compressive deformation of the sample; therefore, the thickness measurement is performed after clamping is complete and stable. The electric field control model uses the thickness measured under clamping conditions as the initial value of the equivalent electrode spacing. During subsequent aging, the thickness change is dynamically corrected using this reference thickness as a reference. When the sample experiences thickness changes due to thermal expansion or creep during aging, the electric field closed-loop control unit updates the equivalent electrode spacing based on the difference between the real-time thickness and the initial reference thickness.

[0060] Step 5: During the subsequent voltage boosting and aging process, the thickness measurement module continuously collects the real-time thickness d(t) and transmits it to the electric field closed-loop control unit for dynamic correction.

[0061] Step 6: Set the target electric field strength to 40 kV / mm using the electric field target setting unit.

[0062] Step 7: Start the high-voltage DC generator housing and steadily increase the voltage at a rate of 1 kV / min. The electric field closed-loop control unit calculates the target voltage based on the real-time thickness. During the voltage increase process, the closed-loop control mode is activated. As the voltage rises, the electric field closed-loop control unit collects the thickness parameters in real time according to the control cycle and dynamically corrects the voltage output, ensuring that the voltage increase process always meets the matching relationship between the target electric field strength and the real-time thickness.

[0063] Step 8: Once the voltage reaches the target electric field matching the initial reference thickness, the system enters constant field control mode. The heating system is then activated, raising the temperature to 90°C at a preset heating rate. During the heating process, the electric field closed-loop control unit continues to operate without interruption due to temperature changes. When temperature changes cause variations in sample thickness, the electric field closed-loop control unit recalculates the target voltage based on the real-time thickness and completes the correction within the control cycle to maintain a constant electric field strength within the sample. Once the temperature reaches the set value and stabilizes, the system enters the constant temperature-constant field coupled operation stage. Temperature control and electric field control operate in parallel. Temperature increases may cause thermal expansion or softening deformation of the sample, thereby altering the effective distance between electrodes. The electric field closed-loop control unit continuously collects real-time thickness parameters throughout the heating and constant temperature stages and dynamically adjusts the output voltage based on the equivalent electrode spacing model. Electric field control has higher priority than temperature control; when thickness changes cause electric field deviations exceeding the error threshold, voltage correction is prioritized.

[0064] Step 9: During the aging process, the thickness measurement module continuously collects real-time thickness d(t) according to the preset control cycle T; the electric field closed-loop control unit calculates the target voltage U in each control cycle. (t), and compare it with the current output voltage Uo(t); when the voltage deviation |ΔU| exceeds the error threshold ε, a correction is performed; when the thickness change Δd exceeds the preset change threshold in a single cycle, an instant correction mechanism is triggered, and the correction frequency is increased in the current cycle.

[0065] Step 10: After the aging time reaches the set time, turn off the high-voltage DC power supply and use a grounded metal rod to discharge the load.

[0066] Step 11: Turn off the heating system and allow the sample to cool naturally to room temperature before removing it.

[0067] In this embodiment, the changes in the internal electric field of the sample were monitored at different aging stages, and no significant electric field shift was observed. Compared with the fixed voltage loading method, the closed-loop control device described in this invention can effectively maintain a constant target electric field, improving the accuracy and repeatability of the electrothermal aging test.

[0068] On the other hand, this embodiment also provides an electronic device, including a memory, a processor, and a computing program stored in the memory and executable on the processor, wherein the processor implements the method when executing the computing program.

[0069] On the other hand, this embodiment also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method.

[0070] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An adjustable DC loading device for electrothermal aging of sheet-like cable insulation samples, characterized in that, include: Electric field target setting unit, used to set the target electric field physical quantity; The sample state acquisition unit is used to acquire geometric parameters that affect the electric field distribution inside the sample. An electric field control unit, connected to the electric field target setting unit and the sample state acquisition unit, is used to establish an electric field control model based on the target electric field physical quantities and the geometric parameters, and to generate a voltage regulation control signal. A voltage output regulation unit, connected to the electric field regulation unit, is used to regulate the output voltage according to the control signal; An electrode application unit, connected to the voltage output adjustment unit, is used to apply the output voltage to both sides of the sample; When the state of the sample changes, the electric field control unit corrects the voltage output according to the dynamic changes of the geometric parameters in order to maintain the target electric field state constant.

2. The apparatus according to claim 1, characterized in that, The geometric parameters acquired by the sample state acquisition unit include the sample thickness. The electric field control unit determines the equivalent electrode spacing based on the sample thickness and calculates the corresponding target output voltage based on the target electric field physical quantity.

3. The apparatus according to claim 2, characterized in that, The sample state acquisition unit also acquires thermal expansion deformation parameters or structural disturbance parameters. The electric field control unit corrects the equivalent electrode spacing based on the thermal expansion deformation parameters or structural disturbance parameters, and determines the final voltage regulation control signal based on the real-time measured thickness.

4. The apparatus according to claim 1, characterized in that, The sample state acquisition unit includes a non-contact thickness measurement device and a contact displacement detection device. The electric field control unit selects the corresponding measurement method according to the sample temperature state or operating stage and acquires the corresponding geometric parameters.

5. The apparatus according to claim 1, characterized in that, The electric field control unit controls the voltage output regulation unit to switch between continuous regulation mode and graded regulation mode according to the rate of change of the geometric parameters or the operating stage, so as to generate a corresponding voltage regulation control signal.

6. The apparatus according to claim 1, characterized in that, The electric field control unit also determines the voltage error threshold based on the target electric field physical quantity and the equivalent electrode spacing, and controls the deviation between the actual output voltage and the target voltage within the voltage error threshold range in each control cycle.

7. The apparatus according to claim 1, characterized in that, The electric field control unit also adaptively adjusts the length of the control cycle or the voltage adjustment step according to the rate of change of geometric parameters or the rate of change of temperature.

8. The apparatus according to claim 1, characterized in that, The electrode application unit includes upper and lower electrode structures and a voltage equalization ring structure. The voltage equalization ring is used to optimize the electric field distribution at the electrode edge and does not participate in voltage regulation as a closed-loop control variable.

9. The apparatus according to claim 1, characterized in that, It also includes a circuit protection device. A status monitoring interface is provided between the electric field control unit and the circuit protection device. When the protection circuit is triggered, the electric field control unit suspends closed-loop regulation and switches to a safe step-down mode.

10. The apparatus according to claim 1, characterized in that, The electric field control unit also includes a control algorithm module, which is used to adaptively correct the output voltage according to the real-time changes of the geometric parameters, and to execute a closed-loop control process of thickness acquisition, voltage calculation, error judgment and voltage output in each control cycle.

Images