Wear detection device and method based on uneven thermal cycle aging of generator winding

Abstract

The application belongs to the technical field of motor insulation test and evaluation, and provides a wear detection device and method based on uneven thermal cycle aging of a generator winding. The application is aimed at the aging wear defects of the generator winding caused by uneven thermal cycle, and the quantitative detection of the aging wear degree of the winding is realized by calculating a thermal aging index and a crack defect index respectively to obtain a comprehensive detection coefficient, which can reflect the actual aging wear state of the winding under the action of uneven thermal cycle, and provide a reliable technical basis for the state evaluation and operation and maintenance of the generator winding.

Description

Technical Field

[0001] This invention belongs to the field of motor insulation testing and evaluation technology, specifically relating to a wear detection device and method based on uneven thermal cycling aging of generator windings. Background Technology

[0002] The stator winding is the main component of a generator that enables energy conversion. The condition of its insulation system directly determines the generator's operational safety, stability, and overall lifespan. The winding structure is shown in the figure. During actual operation, the generator experiences uneven temperature distribution at different locations in the winding due to grid load scheduling, unit start-up and shutdown, and changes in ambient temperature. It also repeatedly undergoes cycles of heating, heat preservation, and cooling. This periodic, non-uniform thermal cycle subjectes the winding insulation material to alternating thermal expansion and contraction stress over a long period, gradually leading to problems such as insulation resin deterioration, dielectric property decay, insulation layer delamination, and internal mechanical microcracks. If these problems become severe, insulation breakdown can occur, causing unplanned generator shutdowns and resulting in significant economic losses.

[0003] Current research on the thermal aging of generator winding insulation largely relies on accelerated aging tests to simulate the insulation degradation process. However, existing accelerated aging schemes suffer from numerous problems, including discrepancies with actual operating conditions and significant flaws in their operational procedures. Most existing thermal aging tests employ a constant-temperature chamber to uniformly heat a portion of the winding, applying a single, fixed temperature. This fails to reproduce the temperature differences at different locations within the winding, such as straight sections, ends, and slots, during actual generator operation, and also cannot simulate the uneven temperature field caused by load fluctuations. Consequently, most simulated aging processes deviate significantly from the actual degradation patterns of the windings under real operating conditions, and fail to reflect the comprehensive damage caused by dynamic thermal cycling to the insulation, thus failing to provide accurate experimental support for assessing winding insulation life.

[0004] Existing thermal cycling aging methods mostly rely solely on heating components for heating and insulation, lacking controllable active cooling methods and relying solely on natural cooling of the windings. This doubles the ineffective time of the experiment, reduces experimental efficiency, and, more importantly, fails to simulate the thermal shock effects of rapid cooling during generator start-up and shutdown or sudden load drops. In actual operating conditions, this repeated rapid thermal expansion and contraction is one of the core reasons for mechanical micro-cracks and delamination defects in the winding insulation. Current aging experiments and performance testing procedures are mostly conducted separately on different equipment. Accelerated aging of the windings is first performed on a heating device, then the windings are removed from the heating platform and transported to dedicated testing equipment for performance testing. This disassembly and transportation process easily causes secondary damage such as impacts and stretching to the already aged and weakened winding insulation. Furthermore, disassembly and reassembly change the test boundary conditions of the windings, resulting in test results that cannot accurately reflect the true aging state of the windings. Moreover, the operation procedures of this equipment are cumbersome, the experimental cycle is long, and the continuity between the aging and testing processes cannot be guaranteed.

[0005] Most performance testing of aged windings focuses only on conventional dielectric parameters such as insulation resistance and breakdown voltage, failing to simultaneously perform comprehensive thermal aging testing. This makes it difficult to comprehensively and systematically assess the combined impact of thermal cycling aging on winding insulation performance, and also hinders the provision of complete experimental data to support early warning of winding insulation failure. Furthermore, in high-altitude, low-latitude regions, low air pressure leads to decreased heat dissipation efficiency, and strong solar radiation causes additional temperature rise on the winding surface, further accelerating insulation aging. Existing accelerated aging tests do not consider these environmental factors, resulting in significant discrepancies between assessment results and actual service conditions.

[0006] To address the aforementioned shortcomings of existing technologies, this invention proposes a scheme that can accurately simulate the uneven thermal cycling process under actual generator operating conditions, and simultaneously perform accelerated aging simulation and wear detection of windings on the same device. This makes the aging simulation more closely resemble actual operating conditions, simplifies the operation process, and provides more accurate test results. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a wear detection device and method based on uneven thermal cycling aging of generator windings, thereby solving the problems in the prior art. The technical solution adopted by this invention is as follows:

[0008] Wear detection device based on uneven thermal cycling aging of generator windings, including heating and heat dissipation components, LCR analyzer, and inter-turn impact pressure tester;

[0009] The heating and heat dissipation components are used to be installed on the winding. The heating and heat dissipation components include a heating mode and a cooling mode. Multiple heating and heat dissipation components are used to periodically heat and cool different positions of the winding.

[0010] The LCR analyzer is used to perform broadband impedance spectrum measurements on the windings to obtain the dielectric loss factor. The inter-turn impact pressure tester is used to acquire the voltage decay oscillation waveform of the winding to obtain the initial voltage decay time constant. and initial accumulated energy ;

[0011] The insulation dielectric loss factor Used to calculate the thermal aging index H;

[0012] The initial voltage decay time constant and the initial accumulated energy Used to calculate the crack defect index C;

[0013] The thermal aging index H and the crack defect index C are used to determine the degree of uneven thermal cycling aging and microcrack defects in the winding.

[0014] Furthermore, it also includes a pressure test chamber, a vacuum pump, and a solar radiation simulation lamp;

[0015] The air pressure test hood is used to cover the winding and to regulate the ambient air pressure of the winding by a vacuum pump; the solar radiation simulation lamp is used to preheat the winding and to regulate the ambient temperature of the winding.

[0016] Furthermore, the heating and heat dissipation components are arranged on the straight section of the winding.

[0017] Furthermore, the heating and heat dissipation components include a fan, heat sink fins, a TEC semiconductor cooling chip, a segmented iron core, and a silicone heating pad;

[0018] The segmented iron core is provided with slots, the inner side of which is used to snap onto the winding, and the outer surface of the slot is provided with the silicone heating pad; the TEC semiconductor cooling chip is provided on the slot opening side of the segmented iron core, and the TEC semiconductor cooling chip contacts the insulating surface of the winding.

[0019] The heat dissipation fins and the fan are installed on the slot opening side of the segmented iron core; the heat dissipation fins are disposed between the TEC semiconductor cooling chip and the fan.

[0020] The wear detection method based on uneven thermal cycling aging of generator windings includes the following steps:

[0021] Step 1: Install multiple heating and heat dissipation components onto the windings;

[0022] Step 2: Arrange thermocouples on the heating and heat dissipation components and the windings; cover the windings inside the pressure test chamber, and use a vacuum pump to connect the pressure test chamber to adjust the ambient air pressure of the windings.

[0023] Step 3: Use a solar radiation simulation lamp to preheat the winding to the target value in order to adjust the ambient temperature of the winding.

[0024] Step 4: Perform broadband impedance spectrum measurement using an LCR analyzer and record the dielectric loss factor at each frequency. Then, an inter-turn impact pressure tester was used to acquire the voltage decay oscillation waveform, and the initial voltage decay time constant was extracted based on the voltage decay oscillation waveform. and initial accumulated energy ;

[0025] Step 5: Activate the heating mode of the heating and heat dissipation components to heat different parts of the winding at different temperatures. After the winding is heated to the preset temperature and held for a preset time, activate the cooling mode of the heating and heat dissipation components to cool the winding to the preset temperature and hold for a preset time. The heating mode and cooling mode are alternated for a preset number of cycles to form a non-uniform heat cycle.

[0026] Step 6: After the preset number of cycles is completed, calculate the thermal aging index H, the crack defect index C, and the comprehensive detection coefficient S, and make a judgment by referring to the grading table.

[0027] Furthermore, the thermal aging index H is calculated using the following formula:

[0028]

[0029] in, This is the initial insulation dielectric loss factor before aging.

[0030] Furthermore, the crack defect index C is calculated using the following formula:

[0031]

[0032] in, The initial decay time constant before aging. This represents the initial accumulated energy before aging.

[0033] Furthermore, the comprehensive detection coefficient S is calculated using the following formula:

[0034]

[0035] in, , This represents the scene weighting coefficient.

[0036] Furthermore, step six also includes parameter adjustments for different environments, based on a low-pressure heat dissipation correction factor. and solar radiation aggravation factor Calculate the environmental weight correction coefficient , Through environmental weight correction coefficient , The thermal aging index H, crack defect index C, and comprehensive detection coefficient S are corrected.

[0037] Furthermore, low-pressure heat dissipation correction factor The calculation formula is:

[0038]

[0039] in, Standard atmosphere, p is the target ambient pressure; This is a correction item;

[0040] Define solar irradiance aggravation factor The calculation formula is:

[0041]

[0042] in, To simulate the irradiation heat flux density, Based on the heating heat flux density; This is a correction item;

[0043] Corrected thermal aging index ; ;

[0044] Corrected crack defect index ; ;

[0045] Corrected comprehensive detection coefficient for:

[0046]

[0047] in, , , , These are the weighting coefficients.

[0048] The present invention has the following beneficial effects:

[0049] (1) The present invention forms different temperature zones in the straight section of the winding by multiple heating and heat dissipation components, and switches periodically between heating mode and cooling mode, which can more closely reflect the non-uniform temperature distribution, start-up and shutdown and load fluctuation caused by the actual operation of the generator.

[0050] (2) This invention utilizes TEC semiconductor cooling chip, heat sink and fan to achieve active cooling, avoiding the problems of long experimental cycle and insufficient thermal shock caused by relying solely on natural cooling, and improving the efficiency of non-uniform thermal cycle aging simulation.

[0051] (3) This invention integrates thermal cycling aging, broadband impedance spectrum measurement and impulse voltage decay waveform detection into the same experimental platform, reducing secondary damage caused by repeated disassembly and reassembly and transportation of the winding, and ensuring that the detection boundary conditions are consistent before and after aging.

[0052] (4) The present invention calculates the thermal aging index H, crack defect index C and comprehensive detection coefficient S based on the insulation dielectric loss factor and voltage decay oscillation waveform, respectively, which can realize the quantitative evaluation of the degree of thermal aging and microcrack defect of winding insulation;

[0053] (5) This invention introduces environmental correction factors through an air pressure test hood, a vacuum pump and a solar radiation simulation lamp, which can correct and evaluate the aging state of windings under special service conditions such as high altitude, low air pressure and strong radiation, and provide a basis for generator winding operation, maintenance and life management. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the winding structure;

[0055] Figure 2 This is a schematic diagram of the overall structure of the present invention;

[0056] Figure 3 This is a schematic diagram of the heating and heat dissipation components;

[0057] Figure 4 A schematic diagram illustrating the pressure regulation of the pressure test chamber and vacuum pump;

[0058] Figure 5 This is a flowchart of the present invention;

[0059] Figures 1-4 The components are as follows: 1. Control system; 2. Winding; 3. Computer; 4. Heating and heat dissipation components; 5. Experimental platform; 6. Power supply box; 7. LCR analyzer; 8. High-voltage isolation switching box; 9. Inter-turn impact pressure tester; 10. Temperature collection module; 11. Solar radiation simulation lamp; 12. Thermocouple; 13. Fan; 14. Heat sink fins; 15. TEC semiconductor cooling chip; 16. Segmented iron core; 17. Screw; 18. Spring; 19. Silicone heating pad; 20. Vacuum pump; 21. Pressure test chamber; 22. Pressure sensor. Detailed Implementation

[0060] The following will be described in conjunction with embodiments of the present invention. Figures 1-5The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0061] like Figures 1-4 This invention proposes a wear detection device based on uneven thermal cycling aging of generator windings, including a heating and heat dissipation component 4, an LCR analyzer 7, and an inter-turn impact pressure tester 9.

[0062] The heating and heat dissipation component 4 is used to be installed on the winding 2. The heating and heat dissipation component 4 includes a heating mode and a cooling mode. Multiple heating and heat dissipation components 4 are used to periodically heat and cool different positions of the winding 2.

[0063] The LCR analyzer 7 is used to perform broadband impedance spectrum measurement on winding 2 to obtain the dielectric loss factor. The inter-turn impact pressure tester 9 is used to acquire the voltage decay oscillation waveform of winding 2 to obtain the initial voltage decay time constant. and initial accumulated energy ;

[0064] The insulation dielectric loss factor Used to calculate the thermal aging index H;

[0065] The initial voltage decay time constant and the initial accumulated energy Used to calculate the crack defect index C;

[0066] The thermal aging index H and the crack defect index C are used to determine the degree of uneven thermal cycling aging and microcrack defects in winding 2.

[0067] Furthermore, it also includes a pressure test chamber 21, a vacuum pump 20, and a solar radiation simulation lamp 11;

[0068] The air pressure test hood 21 is used to cover the winding 2 and the vacuum pump 20 is used to adjust the ambient air pressure of the winding 2; the solar radiation simulation lamp 11 is used to preheat the winding 2 and adjust the ambient temperature of the winding 2.

[0069] Furthermore, the heating and heat dissipation component 4 is arranged on the straight section of the winding 2. For example... Figure 1 The winding 2 consists of an involute segment, a nose end, and a straight segment, which together form a U-shaped structure. The inner layer of the winding 2 is made of copper wire, and the outer layer is an insulating layer.

[0070] Furthermore, the heating and heat dissipation assembly 4 includes a fan 13, heat dissipation fins 14, a TEC semiconductor cooling chip 15, a segmented iron core 16, and a silicone heating pad 19;

[0071] The segmented iron core 16 is provided with a slot, the inner side of which is used to snap onto the winding 2, and the outer surface of the slot is provided with the silicone heating pad 19; the slot opening side of the segmented iron core 16 is provided with the TEC semiconductor cooling chip 15, and the TEC semiconductor cooling chip 15 contacts the insulating surface of the winding 2.

[0072] The heat dissipation fins 14 and the fan 13 are installed on the slot opening side of the segmented iron core 16; the heat dissipation fins 14 are disposed between the TEC semiconductor cooling chip 15 and the fan 13.

[0073] This invention restores the installation state of winding 2 in the generator stator, fixes winding 2, and clamps the heating and heat dissipation assembly 4. The invention includes a fixing and clamping part. This part includes screws 17 with springs 18 and an experimental platform 5. Winding 2 passes through the slot of the segmented iron core 16 and forms an interference fit with the segmented iron core 16, ensuring efficient heat conduction between the segmented iron core 16 and winding 2. Four screws 17 with springs 18 connect the heat dissipation fins 14, fan 13, and segmented iron core 16, pressing them together. The resulting pressure presses the entire heat dissipation structure firmly against the surface of winding 2, maintaining tight contact between winding 2 and segmented iron core 16, while preventing winding 2 from shifting during thermal cycling. A two-millimeter gap is left between the screw head and the top of fan 13 to prevent winding 2 from being pushed up and damaging semiconductor components when heated and expanding.

[0074] The heating and cooling assembly 4 of this invention enables independent heating and controllable active cooling of different positions on the winding 2. Independent silicone heating pads 19 are installed at different positions along the straight section of the winding 2, and the output power of each heating pad can be adjusted individually, thus creating different temperature distributions on the winding 2. The heat dissipation and cooling functions are achieved through a TEC semiconductor cooling chip 15, heat sink fins 14, and a fan 13. The cold end of the TEC semiconductor cooling chip 15 is in close contact with the surface of the winding 2, and the hot end is connected to the heat sink fins 14. The fan 13 accelerates the airflow through the heat sink fins 14. The three components work together to quickly remove heat from the winding 2, achieving a cooling process to ambient temperature.

[0075] This invention also incorporates a temperature monitoring module to collect temperature data from various locations during the experiment in real time, providing a basis for adjusting the heating and cooling processes. Multiple thermocouples 12 are arranged on the insulating surface of the winding 2 and the interlayer between it and the TEC semiconductor cooling chip 15, enabling simultaneous acquisition of temperature information from different locations. Signals from all thermocouples 12 are transmitted to the temperature collection module 10, which then displays the data in real time via a computer 3 and feeds the real-time temperature back to the control system 1, thus regulating the heating and cooling processes. When simulating a low-pressure environment, a pressure test chamber 21 is placed above the winding 2. Sealed wire holes are provided on both sides of the pressure test chamber 21 for connecting the thermocouples 12 and other equipment to the outside. The vacuum pump 20 is started to adjust to the target pressure. Simultaneously, the system records the pressure value inside the chamber and performs pressure compensation calibration on the thermocouple 12 measurements to ensure temperature measurement accuracy.

[0076] like Figure 5 The present invention also proposes a wear detection method based on uneven thermal cycling aging of generator windings, comprising the following steps:

[0077] Step 1: Install multiple heating and heat dissipation components 4 onto the straight section of winding 2;

[0078] Specifically, the process includes: slowly threading the winding 2 to be tested through the slot of the segmented iron core 16, adjusting its position so that the straight section of the winding 2 is fully embedded in the slot, forming an interference fit with the segmented iron core 16 to ensure efficient heat transfer. Silicone heating pads 19 are attached to both sides and the bottom of the segmented iron core 16. TEC semiconductor cooling chips 15 and heat sink fins 14 are then sequentially laid on the top of the segmented iron core 16. A thin layer of thermal grease is evenly applied to each contact surface and smoothed out, squeezing out any air. It is important to note that the cold end of the cooling chip should be in close contact with the winding 2, and the hot end should face the heat sink fins 14. Finally, the fan 13 is fixed to the outside of the fins and aligned with the airflow path. The spring 18 is fitted onto the bare part of the screw 17, passed through the heat sink through-hole, aligned with the screw hole in the iron core, and tightened to ensure that the spring 18, after compression, can press firmly against the heating and cooling components 4. A feeler gauge is then used to adjust the gap between the screw head and the top of the fan 13 to 2 mm to prevent the winding 2 from expanding due to heat and damaging the cooling chip.

[0079] Step 2: Thermocouples 12 are arranged on the heating and heat dissipation components 4 and the winding 2; and the winding 2 is covered inside the air pressure test chamber 21. A vacuum pump 20 is used to connect the air pressure test chamber 21 to adjust the ambient air pressure of the winding 2.

[0080] Specifically, thermocouples 12 are arranged at the cold end of the TEC semiconductor cooling chip 15 and at the connection between the straight section and the involute curve of the winding 2. Temperature measurement at the connection between the straight section and the involute curve serves two purposes: first, to compare the effectiveness of heating and cooling between the straight section and other parts; and second, because the connection between the straight section and the involute curve is a part with significant deformation and temperature difference, resulting in severe mechanical shear stress and greater wear. The control system 1 is connected to all thermocouples 12, and the signal lines of the thermocouples 12 are connected to the temperature collection module 10 according to their numbers. The corresponding positions are marked in the software of the computer 3, and then a USB cable is used to connect the temperature collection module 10 to the computer 3. The multiple independent output terminals of the power supply box 6 are connected to each silicone heating pad 19, the TEC semiconductor cooling chip 15, and the fan 13, enabling each heating and cooling unit to independently adjust its power and start / stop status. Connect the common terminal of the high-voltage isolating switch 8 to the two leads of winding 2, connect its first test terminal to the LCR analyzer 7, and connect its second test terminal to the inter-turn impact pressure tester 9. When performing broadband impedance spectroscopy measurements, the high-voltage isolating switch 8 only connects the circuit between winding 2 and the LCR analyzer 7, and disconnects the inter-turn impact pressure tester 9 and its heating / cooling power supply circuits. When acquiring impulse voltage decay waveforms, the high-voltage isolating switch 8 only connects the circuit between winding 2 and the inter-turn impact pressure tester 9, and disconnects the LCR analyzer 7 and its heating / cooling power supply circuits. The high-voltage isolating switch 8 is used to achieve electrical isolation and safe switching between different testing instruments, preventing the LCR analyzer 7 from being subjected to impulse high voltage, and also preventing the thermal cycling power supply circuit from interfering with the impedance spectroscopy and impulse voltage test results, ensuring that aging simulation and performance testing can be continuously completed on the same platform. Finally, connect the control system 1 to the power supply box 6 and the high-voltage isolating switch 8 using communication lines. To simulate a high-altitude, low-latitude environment, a pressure test hood 21 is sealed and installed around the experimental platform 5, covering the winding 2, and connected to a vacuum pump 20. An array of solar radiation simulation lamps 11 is fixed above the winding 2 and connected to an independent power supply circuit in the power supply box 6. The target pressure value and irradiance power are set in the control system 1. Simultaneously, a pressure sensor 22 is installed inside the pressure test hood 21, and its signal is connected to the temperature collection module 10 to monitor the internal pressure in real time.

[0081] Step 3: Preheat winding 2 to the target value using solar radiation simulation lamp 11 to adjust the ambient temperature of winding 2; before starting the heating and heat dissipation assembly 4, calculate the environmental weight correction coefficient. , ;

[0082] Specifically, this includes: starting the vacuum pump 20 before initiating the thermal cycle to pump the air pressure inside the air pressure test chamber 21 to the target value and continuously maintaining the target ambient air pressure by adjusting the power of the vacuum pump 20; turning on the solar radiation simulation lamp 11 and preheating it for 10 minutes according to the target irradiance power to achieve a stable additional temperature rise on the surface of the winding 2, thereby simulating the ambient temperature and real solar radiation based on the solar radiation simulation lamp 11; and inputting environmental parameters into the control system 1 to calculate the environmental weight correction coefficient. , This is used for the correction of subsequent detection indicators.

[0083] Step 4: Perform broadband impedance spectroscopy measurements using an LCR analyzer 7 and record the dielectric loss factor at each frequency. Then, the voltage decay oscillation waveform was acquired using an inter-turn impact pressure tester 9, and the initial voltage decay time constant was extracted based on the voltage decay oscillation waveform. and initial accumulated energy ;

[0084] Specifically, this includes: operating the high-voltage isolation switch 8 to disconnect winding 2 and heating and heat dissipation components 4, and connecting the test circuit of the LCR analyzer 7. The scanning frequency range is set to 0.001Hz~1MHz, the number of scanning points is 100, the series equivalent measurement mode is selected, and the instrument is started to automatically record the insulation dielectric loss factor at each frequency. Computer 3 synchronously stores data. The initial thermal aging index baseline value is calculated based on Formula 2. .

[0085] After completing the broadband impedance spectrum measurement using the LCR analyzer 7, the circuit is switched via the high-voltage isolation switching box 8 and connected to the inter-turn impulse pressure tester 9. A standard impulse voltage of the corresponding voltage level is applied according to national standards, and the complete voltage decay oscillation waveform is recorded. The computer 3 performs envelope exponential fitting on the waveform and extracts the initial decay time constant. and the accumulated energy of the previous N cycles Save it as a baseline file;

[0086] Step 5: With winding 2 de-energized, start the heating mode of heating and heat dissipation component 4 to heat different positions of winding 2 at different temperatures. After winding 2 is heated to the preset temperature and held for a preset time, start the cooling mode of heating and heat dissipation component 4 to cool winding 2 to the preset temperature and hold for a preset time. The heating mode and cooling mode are alternated for a preset number of cycles to form an uneven heat cycle.

[0087] Specifically, this includes: controlling five adjacent iron core sections corresponding to the installation position of winding 2 through control system 1, setting them sequentially to a stepped temperature of 80℃, 130℃, 180℃, 130℃, and 80℃, to recreate the operating condition of poor heat dissipation at the center of the generator and the formation of extreme hot spots due to localized heat accumulation during generator operation. After setting the temperature gradient, a periodic thermal shock waveform is set to simulate the aging and failure process of winding 2 in a cyclical temperature alternation manner. The single thermal shock cycle process is as follows: First, all silicone heating pads 19 are started at full power, allowing the entire winding 2 to heat up rapidly until the central section reaches a high temperature of 180℃, and then maintaining this high temperature for a period of time. After the high-temperature holding stage ends, the power supply to all silicone heating pads 19 is cut off, and at the same time, the high-temperature resistant TEC semiconductor cooling chip 15 is reverse-energized, switching to cooling mode, and the external fan 13 runs at full speed to quickly remove the accumulated heat from the iron core and the surface of winding 2, allowing winding 2 to cool down rapidly to room temperature. This rapid cooling process from extreme high temperature to room temperature will subject the fragile insulating varnish film, which has already undergone chemical aging, to intense thermal expansion and contraction, naturally generating mechanical micro-cracks and replicating the physical failure of the insulation layer under actual machine operating conditions.

[0088] The total number of thermal shock cycles is set in control system 1, typically 100 cycles. After clicking start, the device automatically repeats the entire process of heating, high-temperature holding, rapid cooling, and settling at room temperature. Computer 3 can monitor the temperature change curves and equipment operating status of the five sections in real time. When excessive temperature deviations occur in any section or equipment malfunctions such as abnormal jamming, the system stops and triggers an alarm. During the experiment, the equipment can be manually paused after every 20 thermal shock cycles. The intermediate performance test of winding 2 can be completed according to step four. There is no need to disassemble winding 2 or modify the wiring throughout the process, ensuring the continuity of experimental data.

[0089] Step 6: After the preset number of cycles is completed, calculate the thermal aging index H, the crack defect index C, and the comprehensive detection coefficient S, and make a judgment by referring to the grading table.

[0090] After the preset number of cycles is completed, stop the heating and heat dissipation components 4, and allow winding 2 to cool naturally to room temperature. Repeat step four, and measure the broadband impedance spectrum and impulse voltage waveform after aging. Computer 3 calculates the thermal aging index H according to formula 2, and calculates the crack defect index C according to formula 3; if environmental correction mode is enabled, substitute... , calculate And C'. Calculate the comprehensive detection coefficient S (or the corrected S') according to Formula 4, and make a judgment by referring to the grading table. Compare the H, C, and S values ​​at the initial, intermediate, and final stages to quantitatively assess the aging process and analyze the aging differences at different locations. The judgment under the environmental correction mode still follows the grading standard in Table 1, but uses the corrected comprehensive detection coefficient S' for comparison; at the same time, the values ​​of the environmental correction factors and the corresponding conditions must be noted in the report.

[0091] After testing, turn off the power to all equipment in sequence, disconnect the main power, and disassemble the components in the reverse order of assembly. Carefully remove winding 2 to avoid damaging the aged and brittle insulation layer. Organize all experimental data, plot the temperature cycling curve and the curves showing the changes in H, C, and S with the number of cycles, analyze the aging rate and uniformity, and finally clean the experimental platform 5, wipe the components clean and put them back in their place. Store the cooling element and thermocouple 12 separately in a shockproof box.

[0092] The calculation process of the thermal aging index H, crack defect index C, and comprehensive detection coefficient S in this invention is as follows;

[0093] (1) Thermal aging index H:

[0094] The main insulation of winding 2 adopts an epoxy-mica composite system. Under high temperature, the epoxy resin molecular chains break, the number of polar groups increases, the micro-interface polarization effect is enhanced, and the dielectric loss factor in the low-frequency range decreases. Significantly increased. This is the ratio of energy lost to energy stored in an insulating material under an alternating electric field, i.e.

[0095] (1)

[0096] in Let be the real part of the complex permittivity. The imaginary part is represented; in the low-frequency range of 0.01Hz to 100Hz, interfacial polarization loss and conductivity loss are dominant, and it is most sensitive to chemical structural changes caused by thermal aging. The spectrum serves as a characterization of the degree of thermal aging.

[0097] Within the frequency range of 0.001Hz to 1MHz, the dielectric loss factor of winding 2 was measured using an LCR analyzer 7. Define the thermal aging index H:

[0098] (2)

[0099] in The initial dielectric loss factor before aging is H≥0;

[0100] Grading criteria: H<0.2 indicates slight aging, 0.2≤H<0.5 indicates moderate aging, and H≥0.5 indicates severe aging.

[0101] (2) Crack defect index C:

[0102] Microcracks and delamination defects within the insulation layer of winding 2 can induce partial discharge under impulse voltage, accelerating waveform decay and shortening oscillation duration. The voltage decay time constant is extracted. The accumulated energy E over the previous N cycles can effectively identify microcracks and delamination defects in the insulation layer. In the inter-turn impulse voltage test, a standard impulse voltage is applied, and the voltage decay oscillation waveform is recorded. The decay time constant is obtained through exponential fitting. Calculate the cumulative energy E over the first N oscillation cycles, and define the crack defect index C:

[0103] (3)

[0104] in The initial decay time constant before aging. The initial accumulated energy before aging; C∈0~1;

[0105] Grading criteria: C<0.2 indicates a minor defect, 0.2≤C<0.5 indicates a significant crack, and C≥0.5 indicates a severe delamination or through crack.

[0106] (3) Comprehensive detection coefficient S for aging of winding 2:

[0107] The thermal aging index H and the crack defect index C are fused using a vector synthesis method to define the comprehensive detection coefficient S:

[0108] (4)

[0109] , For scenario weighting coefficients: baseload units , Peak-shaving units , ; standard scenarios ;

[0110] The grading table is shown in Table 1:

[0111] Table 1: Grading Table of Comprehensive Detection Coefficient S

[0112]

[0113] (4) Environmental weighting correction factor:

[0114] For different special service environments (such as high altitude and low air pressure, strong solar radiation, etc.), corresponding environmental correction factors can be introduced to perform equivalent mapping of the detection indicators. This embodiment takes the low air pressure and strong solar radiation environment in a high-altitude and low-latitude region as an example for illustration. The environmental weight correction coefficient is directly related to the target air pressure value simulated by the air pressure test hood 21 and the equivalent irradiance heat flux density applied by the solar radiation simulation lamp 11, realizing the mapping from physical environmental parameters to the correction of detection indicators.

[0115] Low-pressure heat dissipation correction factor :

[0116] (5)

[0117] p is the standard atmospheric pressure, and p is the target ambient pressure; This is a correction item; a recommended value is 0.30.

[0118] Solar irradiation aggravating factor :

[0119] (6)

[0120] in, To simulate the irradiation heat flux density, Based on the heating heat flux density; This is a correction item; a recommended value is 0.25.

[0121] Parameter correction:

[0122] Corrected thermal aging index , ;

[0123] Corrected crack defect index , ;

[0124] Recommended values ​​for weighting coefficients: , , , .

[0125] Corrected comprehensive detection coefficient for:

[0126] (7)

[0127] It should be noted that the specific values ​​of the aforementioned correction factors and weighting coefficients can be adjusted according to the actual characteristics of the target environment. For other special environments, the correction framework of this invention can be used to define corresponding environmental factors for equivalent mapping, and this is not limited to high-altitude and low-latitude scenarios.

[0128] (5) Aging Defect Prediction Model:

[0129] This invention establishes an aging defect prediction model based on detection data obtained under different non-uniform thermal cycling conditions. The aging defect prediction model is used to predict the insulation aging and wear development trend of winding 2 under similar operating conditions based on thermal cycling parameters and environmental parameters, and to characterize the uncertainty of the prediction results.

[0130] In this invention, the aging defect prediction model does not replace the calculation process of the aforementioned thermal aging index H, crack defect index C, and comprehensive detection coefficient S. Instead, based on the calculation of H, C, S, and the corrected comprehensive detection coefficient S′, it further establishes the correspondence between thermal cycling parameters and the degree of aging defects in the insulation of winding 2. Through this model, the trend of aging wear of the insulation of winding 2 under different thermal cycling conditions, different ambient air pressures, and different solar irradiation conditions can be predicted within the range of existing thermal cycling aging experimental data.

[0131] The aging defect prediction model constructed in this invention can be expressed in general form as follows:

[0132] (8)

[0133] Where x is the input operating condition parameter vector, D is the degree of insulation aging defect of winding 2, f(x) is the mapping function between the input operating condition parameters and the degree of insulation aging defect, and ε is the observation noise, which is used to represent the detection error, environmental disturbance, sample difference and random fluctuation during the experiment.

[0134] This invention uses the corrected comprehensive detection coefficient S′ as the main output of the aging defect prediction model. The corrected comprehensive detection coefficient S′ simultaneously considers the effects of the thermal aging index H, the crack defect index C, the low-pressure heat dissipation correction factor, and the solar irradiation aggravation factor, and can reflect the comprehensive aging and wear degree of winding 2 under the combined effects of uneven thermal cycling and special environments. When it is necessary to analyze the development trends of thermal aging and crack defects separately, sub-prediction models can also be established using the thermal aging index H and the crack defect index C as outputs respectively.

[0135] Furthermore, this invention employs Gaussian process regression to establish the aging defect prediction model. Gaussian process regression does not pre-define the mapping function f(x) as a fixed linear or polynomial function, but rather treats f(x) as a Gaussian process, expressed as:

[0136] (9)

[0137] Where m(x) is the mean function, Let x and x′ be the covariance function, where x and x′ are any two operating condition parameter points in the input space. The covariance function is used to characterize the correlation between different thermal cycle operating conditions. The closer the two operating condition parameters are, the stronger the correlation of their corresponding aging defect degrees; when the two operating condition parameters are significantly different, the weaker the correlation of their corresponding aging defect degrees.

[0138] The N sets of independent operating condition data obtained from the thermal cycling aging experiment of this invention constitute a training set. For the i-th experimental condition, its input operating condition parameter vector... Including the highest heating temperature Minimum cooling temperature heating rate Cooling rate Insulation time Cooling hold time The number of thermal cycles n, the ambient air pressure p, and the simulated irradiation heat flux density Output Let S′ be the corrected comprehensive detection coefficient obtained through detection calculation under this working condition. The training set is represented as follows:

[0139] (10)

[0140] in:

[0141] (11)

[0142] It should be noted that the low-pressure heat dissipation correction factor and the solar irradiation aggravation factor are not introduced repeatedly as independent input parameters, but are used in the calculation of the comprehensive detection coefficient S′ after correction according to the aforementioned environmental correction formula. This avoids the duplication of input parameters and improves the clarity of the model structure.

[0143] Furthermore, considering that the degree of insulation aging and wear of winding 2 exhibits a continuous evolution characteristic with changes in temperature gradient, thermal shock intensity, number of thermal cycles, ambient air pressure, and solar irradiance, this invention can select a radial basis kernel function as the covariance function, the expression of which is:

[0144] (12)

[0145] in, The signal variance hyperparameter is used to characterize the overall fluctuation range of the model output; , Let represent the i-th and j-th sample points in the input space; T is the transpose sign; This is a diagonal matrix representing the length scale, used to characterize the influence of each input parameter dimension on the prediction result. After model training, the length scale corresponding to each input parameter can be used to reflect the sensitivity of that parameter to the prediction result of insulation aging defects in winding 2.

[0146] Furthermore, the Gaussian process regression model is trained and its hyperparameters are optimized. Due to measurement errors and environmental disturbances in the actual detection data, the observed data D is considered to be affected by Gaussian noise, and its logarithmic marginal likelihood function is:

[0147] (13)

[0148] Where D represents the degree of aging defect in all training samples. The column vector consists of X; X is the vector of all input operating condition parameters. The matrix formed by K; K is an N×N covariance matrix; Let θ be the observation noise variance; θ be the hyperparameter vector of the Gaussian process; and I be the identity matrix. By maximizing the above logarithmic marginal likelihood function, model parameters suitable for the thermal cycling aging detection data of this invention can be obtained.

[0149] Based on the above aging defect prediction model, for new thermal cycle input conditions to be tested... The model can output the corresponding predicted distribution of aging defect levels:

[0150] (14)

[0151] in, The predicted mean represents the value under the test condition. The predicted degree of insulation aging defects in winding 2 is obtained below; For the test condition Random variables for predicting the degree of insulation aging defects in lower winding 2; The prediction variance represents the uncertainty of the prediction result. The prediction mean and prediction variance are respectively:

[0152] (15)

[0153] (16)

[0154] in, For the test condition The covariance vector between the working conditions and the training set X; This is the kernel function value of the working condition under test.

[0155] When prediction variance When the variance is small, it indicates a high degree of similarity between the test condition and the conditions in the existing training data, and the prediction result is highly reliable; when the prediction variance is small... A large difference indicates a significant discrepancy between the test condition and the existing training data, resulting in high uncertainty in the prediction results. In this case, thermal cycling aging test data under the corresponding test condition can be added to improve the training set and enhance the stability of subsequent predictions.

[0156] Therefore, this invention can predict the trend of insulation aging and wear of winding 2 under different non-uniform thermal cycling conditions, different ambient air pressures, and different solar irradiation conditions within the training data coverage. By comparing the predicted corrected comprehensive detection coefficient S′ with the comprehensive detection coefficient grading standard, the risk of the insulation condition of winding 2 progressing from good, slightly deteriorated, and moderately deteriorated to severely deteriorated can be judged in advance, providing a technical basis for generator winding condition assessment, maintenance plan formulation, and aging defect early warning.

[0157] All test data are automatically stored in computer 3, ultimately enabling a quantitative assessment of the degree of thermal aging and microcrack defects in winding 2.

[0158] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, alterations, alterations, or substitutions 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 wear detection device based on uneven thermal cycling aging of generator windings, characterized in that, Includes heating and heat dissipation components (4), LCR analyzer (7), and inter-turn impact pressure tester (9). The heating and heat dissipation components (4) are used to be installed on the winding (2). The heating and heat dissipation components (4) include a heating mode and a cooling mode. Multiple heating and heat dissipation components (4) are used to periodically heat and cool different positions of the winding (2). The LCR analyzer (7) is used to perform broadband impedance spectrum measurement on the winding (2) to obtain the dielectric loss factor. The inter-turn impact pressure tester (9) is used to collect the voltage decay oscillation waveform of the winding (2) to obtain the initial voltage decay time constant. and initial accumulated energy ; The insulation dielectric loss factor Used to calculate the thermal aging index H; The initial voltage decay time constant and the initial accumulated energy Used to calculate the crack defect index C; The thermal aging index H and the crack defect index C are used to determine the degree of uneven thermal cycling aging and microcrack defects of the winding (2).

2. The wear detection device based on uneven thermal cycling aging of generator windings according to claim 1, characterized in that, It also includes a pressure test chamber (21), a vacuum pump (20), and a solar radiation simulation lamp (11); The air pressure test hood (21) is used to cover the winding (2) and the ambient air pressure of the winding (2) is adjusted by the vacuum pump (20); the solar radiation simulation lamp (11) is used to preheat the winding (2) and adjust the ambient temperature of the winding (2).

3. The wear detection device based on uneven thermal cycling aging of generator windings according to claim 1, characterized in that, The heating and heat dissipation components (4) are arranged on the straight section of the winding (2).

4. The wear detection device based on uneven thermal cycling aging of generator windings according to claim 1, characterized in that, The heating and heat dissipation components (4) include a fan (13), heat dissipation fins (14), a TEC semiconductor cooling chip (15), a segmented iron core (16), and a silicone heating pad (19). The segmented iron core (16) is provided with a slot, the inner side of which is used to snap onto the winding (2), and the outer surface of the slot is provided with the silicone heating pad (19); the slot opening side of the segmented iron core (16) is provided with the TEC semiconductor cooling chip (15), and the TEC semiconductor cooling chip (15) contacts the insulating surface of the winding (2). The heat dissipation fins (14) and the fan (13) are installed on the slot opening side of the segmented iron core (16); the heat dissipation fins (14) are disposed between the TEC semiconductor cooling chip (15) and the fan (13).

5. A wear detection method based on uneven thermal cycling aging of generator windings, and based on the wear detection device based on uneven thermal cycling aging of generator windings as described in any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Install multiple heating and heat dissipation components (4) onto the winding (2); Step 2: Arrange thermocouples (12) on the heating and heat dissipation components (4) and the winding (2); cover the winding (2) inside the air pressure test chamber (21), and use a vacuum pump (20) to connect the air pressure test chamber (21) to adjust the ambient air pressure of the winding (2); Step 3: Use a solar radiation simulation lamp (11) to preheat the winding (2) to the target value in order to adjust the ambient temperature of the winding (2); Step 4: Use an LCR analyzer (7) to perform broadband impedance spectrum measurement and record the insulation dielectric loss factor at each frequency. Then, the voltage decay oscillation waveform was acquired using an inter-turn impact pressure tester (9), and the initial voltage decay time constant was extracted based on the voltage decay oscillation waveform. and initial accumulated energy ; Step 5: Start the heating mode of the heating and heat dissipation component (4) to heat different positions of the winding (2) at different temperatures. After the winding (2) is heated to the preset temperature and held for a preset time, start the cooling mode of the heating and heat dissipation component (4) to cool the winding (2) to the preset temperature and hold for a preset time. The heating mode and cooling mode are alternated until the preset number of cycles are reached to form an uneven heat cycle. Step 6: After the preset number of cycles is completed, calculate the thermal aging index H, the crack defect index C, and the comprehensive detection coefficient S, and make a judgment by referring to the grading table.

6. The wear detection method based on uneven thermal cycling aging of generator windings according to claim 5, characterized in that, The thermal aging index H is calculated using the following formula: in, This is the initial insulation dielectric loss factor before aging.

7. The wear detection method based on uneven thermal cycling aging of generator windings according to claim 5, characterized in that, The crack defect index C is calculated using the following formula: in, The initial decay time constant before aging. This represents the initial accumulated energy before aging.

8. The wear detection method based on uneven thermal cycling aging of generator windings according to claim 5, characterized in that, The comprehensive detection coefficient S is calculated using the following formula: in, , This represents the scene weighting coefficient.

9. The wear detection method based on uneven thermal cycling aging of generator windings according to claim 5, characterized in that, Step six also includes parameter adjustments for different environments, based on a low-pressure heat dissipation correction factor. and solar radiation aggravation factor Calculate the environmental weight correction coefficient , Through environmental weight correction coefficient , The thermal aging index H, crack defect index C, and comprehensive detection coefficient S are corrected.

10. The wear detection method based on uneven thermal cycling aging of generator windings according to claim 9, characterized in that, Low-pressure heat dissipation correction factor The calculation formula is: in, Standard atmosphere, p is the target ambient pressure; This is a correction item; Define solar irradiance aggravation factor The calculation formula is: in, To simulate the irradiation heat flux density, Based on the heating heat flux density; This is a correction item; Corrected thermal aging index ; ; Corrected crack defect index ; ; Corrected comprehensive detection coefficient for: in, , , , These are the weighting coefficients.

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