Method for improving insulation performance of 10kV generator at level H and application thereof

Abstract

This invention relates to the field of motor insulation technology, and discloses a method and application for improving the H-class insulation performance of a 10kV generator. The method includes: preparing a composite insulating impregnating resin; disassembling the 10kV generator to be maintained and cleaning and pre-drying it; vacuum pressure impregnating the pre-dried stator with the resin, and then subjecting the impregnated stator to a two-step temperature-controlled curing process with applied mechanical micro-vibration to obtain a stator with a gradient insulation layer; performing mechanical maintenance and dynamic balancing tests on the rotor; and finally reassembling the qualified rotor, stator, and housing assembly. This invention, by employing a specific composite resin and a two-step curing process with micro-vibration, enables the insulation layer to possess both high thermal conductivity and dust repellency, forming a gradient structure, thereby improving the heat dissipation capacity and anti-flashover stability of the 10kV generator, and achieving further improvement in overall performance.

Description

Technical Field

[0001] This invention relates to the field of motor insulation technology, specifically to a method and application for improving the H-class insulation performance of a 10kV generator. Background Technology

[0002] 10kV medium- and high-voltage generators are key equipment in power systems, distributed energy sources (such as coalbed methane power plants), and large-scale industrial drives. Their stator windings operate under high temperature, high voltage, and mechanical vibration for extended periods, making the insulation system a crucial component for ensuring their safe and stable operation. Therefore, developing highly reliable Class H insulation systems and performing insulation performance enhancement maintenance on existing units is of great significance for ensuring power grid and production safety.

[0003] Currently, for the treatment of H-class insulation of 10kV generators, whether for new construction or maintenance, the vacuum pressure impregnation (VPI) process is commonly used. This technology typically uses F-class or H-class epoxy impregnation resin to impregnate the entire stator winding, and then cures the resin through static heating (static baking) to form a dense insulation unit. For harsh operating environments, an additional layer of protective paint is sometimes sprayed onto the winding surface to enhance its protective capabilities.

[0004] However, the aforementioned existing technologies still reveal shortcomings in application. First, the traditional epoxy impregnated resin matrix itself has poor thermal conductivity, while 10kV generator windings generate a large amount of Joule heat during operation. If this heat cannot be quickly dissipated through the insulation layer, the actual operating temperature inside the windings will remain high. This not only reduces the generator's output efficiency but also accelerates the thermal aging process of Class H insulation materials, shortening their service life. Second, the operating environment of generators (especially gas generators) is often accompanied by high levels of dust, oil, or moisture. The surface of traditional epoxy resin after curing easily adsorbs these contaminants, forming conductive paths at the winding ends, leading to a decrease in insulation resistance and easily triggering surface flashover accidents, seriously threatening the stability of the insulation system.

[0005] Therefore, this invention proposes a method and application for improving the H-level insulation performance of 10kV generators to address the shortcomings of existing technologies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method and application for improving the H-class insulation performance of 10kV generators. The existing H-class insulation materials for 10kV generators have poor thermal conductivity, leading to poor heat dissipation of windings, rapid thermal aging, and weak surface anti-flashover capability, resulting in decreased insulation stability.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a method for improving the H-level insulation performance of a 10kV generator, employing the following technical solution:

[0009] Step S1: Prepare composite insulating impregnation resin; Step S2: Disassemble the 10kV generator to be maintained to obtain the stator, rotor, and housing assembly to be processed; clean and pre-dry the stator and rotor to be processed, and clean the housing assembly to obtain a pre-dried stator, a pre-dried rotor, and a clean housing assembly; Step S3: Vacuum pressure impregnate the pre-dried stator after step S2 using the composite insulating impregnation resin prepared in step S1 to obtain an impregnated stator; and perform double-step temperature-controlled curing on the impregnated stator to obtain a stator with a gradient insulation layer; Step S4: Perform mechanical maintenance on the pre-dried rotor obtained in step S2 to obtain a rotor that has completed maintenance; Step S5: Perform a dynamic balancing test on the rotor obtained in step S4, and reassemble the dynamically balanced rotor, the stator with a gradient insulation layer obtained in step S3, and the clean housing assembly obtained in step S2.

[0010] The composite insulating impregnating resin is made from components comprising the following parts by weight:

[0011] Bisphenol A diglycidyl ether type epoxy resin: 100 parts; Methylhexahydrophthalic anhydride: 80-95 parts; Butyl glycidyl ether: 5-15 parts; 2-Ethyl-4-methylimidazolium: 0.5-1.5 parts; 3-(2,3-epoxypropoxy)propyltrimethoxysilane: 1-3 parts; Plate-like hexagonal boron nitride: 50-150 parts; Dust-repellent functional filler: 1-5 parts.

[0012] The dust-repellent functional filler is prepared by the following steps: 100 parts by weight of hydrophilic fumed silica are vacuum dried at 115°C and then added to 1000 parts by weight of cyclohexane and ultrasonically dispersed to form a suspension; 15-25 parts by weight of perfluorooctyltriethoxysilane are added dropwise to the suspension and refluxed at 80°C for 6-8 hours; after the reaction is completed, the filler is centrifuged, washed and vacuum dried to obtain the dust-repellent functional filler.

[0013] The dual-step temperature-controlled curing process includes: the first step: applying mechanical micro-vibration with a frequency of 15-60Hz and an amplitude of 0.1-0.5mm to the impregnated stator at a temperature of 75-85℃ and maintaining it constant for 30-60 minutes; the second step: stopping the mechanical micro-vibration, raising the temperature to 175-185℃ and maintaining it constant for 10-16 hours.

[0014] By adopting the above technical solution, this invention achieves a comprehensive improvement in the insulation performance of generators through the synergistic effect of specific components of the composite insulating impregnating resin and a two-step temperature-controlled curing process. Its technical principle lies in:

[0015] Synergistic effect mechanism of composite resins:

[0016] The composite insulating impregnating resin used in this invention introduces highly thermally conductive lamellar hexagonal boron nitride (h-BN) as a thermally conductive filler. Its lamellar structure constructs efficient heat conduction pathways within the resin matrix, significantly improving the overall thermal conductivity of the cured insulation layer. This facilitates the rapid dissipation of heat generated by the generator stator windings during operation, effectively reducing winding temperature rise. Simultaneously, a dust-repellent filler is introduced into the resin. This filler is fumed silica surface-modified with fluorinated silanes (such as perfluorooctyltriethoxysilane). The modification process grafts low surface energy fluorinated groups onto the filler surface, giving the final cured insulation layer a strong hydrophobic and oleophobic property, possessing a self-cleaning ability similar to the lotus leaf effect. This makes it difficult for moisture, dust, and oil to adhere, greatly improving the surface insulation resistance and anti-flashover capability at the stator winding ends, and reducing the risk of insulation breakdown in harsh environments.

[0017] The formation mechanism of two-step curing and gradient insulation layer:

[0018] Another core innovation of this invention lies in the use of a two-step curing process (step S3) that combines mechanical micro-vibration. This process utilizes the rheological properties of the resin at different curing stages:

[0019] The first step (low temperature + micro-vibration): At a lower temperature of 75-85℃, the resin system is in a low-viscosity flow state (transition from step A to step B). Applying specific mechanical micro-vibration at 15-60Hz promotes deep penetration of the resin into the winding coil and efficiently removes any micro-air bubbles that may remain during impregnation, ensuring the compactness of the impregnation. More importantly, this micro-vibration helps the high-density thermally conductive filler (plate-like hexagonal boron nitride) to undergo controlled orientation or sedimentation in the still-low-viscosity resin, forming a relatively rich area of ​​thermally conductive filler near the winding surface. This creates a "gradient insulation layer" structure within the insulation layer, optimizing the heat conduction path from the copper wire to the iron core.

[0020] The second stage (high temperature + static curing): After the first stage is completed, the resin has initially gelled, and the filler position is relatively fixed. Vibration is then stopped (to prevent damage to the established gradient structure), and the temperature is subsequently raised to 175-185℃ for prolonged constant-temperature curing (C-stage curing). The high temperature ensures that the epoxy resin and curing agent (methylhexahydrophthalic anhydride) fully cross-link, forming a dense and stable three-dimensional network structure, giving the insulation layer the high thermal stability and excellent mechanical strength required for its H-class heat resistance rating.

[0021] In summary, the method of this invention, through optimized design of resin components and innovative control of curing process, enables the stator insulation layer to achieve high thermal conductivity (derived from h-BN and gradient structure) and high anti-flashover properties (derived from dust-repellent filler) while possessing H-class heat resistance. Combined with a complete generator disassembly, maintenance and final assembly process, it comprehensively improves the overall performance and operational reliability of the 10kV generator.

[0022] Preferably, in step S2, the pre-drying process parameters are: constant temperature baking at 110-130℃ for 4-8 hours. This step aims to thoroughly remove moisture adsorbed in the stator and rotor insulation structures, preventing moisture from evaporating during subsequent high-temperature curing and causing pores or defects inside the insulation layer.

[0023] Preferably, in step S3, the process parameters for vacuum pressure impregnation are: evacuating to 50-150 Pa and maintaining it for 2-4 hours, followed by applying a pressure of 0.4-0.6 MPa and holding it for 4-8 hours. The combination of high vacuum and high pressure (VPI process) ensures that the low-viscosity impregnation resin can completely penetrate and fill every tiny gap in the winding coil, achieving gapless insulation filling.

[0024] Preferably, in step S4, the mechanical maintenance of the rotor includes: removing the old bearing and heating and installing the new bearing. This step ensures the reliability of the generator's mechanical operating parts, matching the improved electrical performance of the stator insulation.

[0025] Preferably, in step S5, the dynamic balancing test ensures that the imbalance of the rotor after maintenance meets the G2.5 accuracy level requirements. High-precision dynamic balancing calibration is key to preventing harmful mechanical vibrations from occurring during high-speed generator operation, avoiding mechanical damage to the stator insulation structure caused by vibration, and ensuring the long-term stable operation of the entire machine.

[0026] Secondly, the present invention also provides the method for improving the H-level insulation performance of a 10kV generator as described in the first aspect, which is applied to the maintenance of a 10kV generator.

[0027] By employing the above-described application, the method of the present invention, which includes the preparation of a specific composite insulating impregnating resin and a two-step curing process, can be fully applied to the maintenance and repair process of a 10kV generator.

[0028] The value of this invention lies in providing a performance enhancement solution that surpasses traditional maintenance standards. Compared to traditional maintenance methods that merely involve cleaning, drying, or repeated impregnation with conventional varnish, this invention not only restores the generator's factory insulation level but also provides a fundamental performance upgrade.

[0029] This invention provides a method and application for improving the H-class insulation performance of a 10kV generator. It has the following beneficial effects:

[0030] 1. This invention employs a composite insulating impregnating resin, which combines high thermal conductivity sheet-like fillers with low surface energy dust-repellent fillers. The high thermal conductivity fillers construct efficient heat conduction pathways within the insulation layer, significantly improving heat dissipation capacity and effectively reducing winding temperature rise during 10kV generator operation; the dust-repellent fillers impart excellent hydrophobicity and self-cleaning properties to the insulation layer surface, greatly enhancing anti-flashover capability and ensuring the insulation stability of the generator in humid or high-dust environments.

[0031] 2. This invention employs a two-step temperature-controlled curing process combined with mechanical micro-vibration. Applying specific mechanical micro-vibration during the initial curing stage of the impregnated resin effectively promotes deep resin penetration into the winding and eliminates micro-bubbles, resulting in a denser insulation structure. Simultaneously, this vibration helps the thermally conductive filler form a directional distribution within the matrix, constructing a gradient insulation layer that facilitates heat dissipation. This process, combined with high-temperature curing, ensures that the 10kV generator stator winding achieves H-class insulation with excellent mechanical properties and no defects. Attached Figure Description

[0032] Figure 1 This is a flowchart of the method for improving the H-level insulation performance of a 10kV generator according to the present invention. Detailed Implementation

[0033] The technical solutions in 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.

[0034] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0035] The epoxy resin is a bisphenol A diglycidyl ether type epoxy resin with CAS number 25068-38-6. It is a colorless to pale yellow viscous liquid with an epoxy equivalent (EEW) of 182-192 g / eq.

[0036] The curing agent is methylhexahydrophthalic anhydride, with CAS number 25550-51-0.

[0037] The active diluent is butyl glycidyl ether, CAS number 2426-08-6.

[0038] The accelerator is 2-ethyl-4-methylimidazole, whose CAS number is 931-36-2.

[0039] The coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane, with CAS number 2530-83-8.

[0040] The thermally conductive filler is a plate-shaped hexagonal boron nitride. This filler is a white powder with a plate-like or scaly morphology, an average particle size (D50) of 5-15 μm, and a purity of not less than 99.5%.

[0041] The dust-repellent filler precursor is hydrophilic fumed silica, with a native particle size of 7-40 nm and a specific surface area of ​​250-350 m² measured by the BET method. 2 / g.

[0042] The surface modifier is perfluorooctyltriethoxysilane, with CAS number 51851-37-7.

[0043] The dust-repellent functional filler is a non-commercially available, surface-modified fumed silica. The specific preparation method is detailed in the subsequent preparation examples.

[0044] The solvents are cyclohexane and anhydrous ethanol, wherein the CAS number of cyclohexane is 110-82-7.

[0045] The conventional insulating varnish used in the comparative example is a commercially available Class H epoxy impregnation resin, product model 188#.

[0046] The conventional protective paint used in the comparative example was a commercially available H-grade silicone dustproof clear coat.

[0047] Preparation Example 1 - Preparation Example 2:

[0048] Preparation Example 1: Preparation of Dust Repellent Functional Packing Material No. 1.

[0049] 100 parts by weight of hydrophilic fumed silica were placed in a vacuum oven and dried under vacuum at 115°C for 5 hours to remove adsorbed moisture from its surface. The dried hydrophilic fumed silica was then added to 1000 parts by weight of cyclohexane and dispersed in an ultrasonic disperser (500W, 22kHz) for 30 minutes to form a homogeneous suspension. Under continuous mechanical stirring, 15 parts by weight of perfluorooctyltriethoxysilane were slowly added dropwise to the suspension. After the addition was complete, the mixture was heated to 80°C and refluxed at this temperature for 6 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The product was collected by centrifugation and washed four times with anhydrous ethanol to completely remove unreacted modifiers and reaction byproducts. The washed product was placed in a vacuum oven and dried under vacuum at 75°C for 10 hours to obtain a white, loose powdery dust-repellent functional filler, No. 1, for later use.

[0050] Preparation Example 2: Preparation of Dust Repellent Functional Packing Material No. 2.

[0051] The preparation method is basically the same as in Preparation Example 1, except that: 25 parts by mass of perfluorooctyltriethoxysilane are slowly added dropwise to a cyclohexane suspension containing 100 parts by mass of dried hydrophilic fumed silica, and the reflux reaction time is extended to 8 hours. The remaining steps are the same as in Preparation Example 1. Finally, a white, loose powdery dust-repellent functional filler No. 2 is obtained for later use.

[0052] See attached document Figure 1 :

[0053] Examples 1-3:

[0054] Example 1:

[0055] This embodiment provides a method for improving the H-level insulation performance of a 10kV generator, including the following steps:

[0056] Step S1: Preparation of composite insulating impregnating resin:

[0057] According to the mass fractions, weigh 100 parts of bisphenol A diglycidyl ether type epoxy resin, 80 parts of methyl hexahydrophthalic anhydride, 15 parts of butyl glycidyl ether, 0.5 parts of 2-ethyl-4-methylimidazolium, 1 part of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 50 parts of plate-shaped hexagonal boron nitride, and 1 part of the dust-repellent functional filler No. 1 prepared in Preparation Example 1.

[0058] Bisphenol A diglycidyl ether type epoxy resin, butyl glycidyl ether, and 3-(2,3-epoxypropoxy)propyltrimethoxysilane were mixed evenly. Flaky hexagonal boron nitride and dust-repellent functional filler No. 1 were added and dispersed by high-speed shearing. After cooling, methylhexahydrophthalic anhydride and 2-ethyl-4-methylimidazole were added and mixed evenly. The mixture was degassed under a vacuum of -0.09 MPa until no more bubbles escaped, yielding composite insulating impregnating resin A.

[0059] Step S2, Disassembly and pretreatment of the generator:

[0060] Select a 10kV generator to be maintained and record its original operating data. Disassemble the generator according to procedures to obtain the stator, rotor, and housing assembly to be processed. Thoroughly clean the stator, rotor, and housing assembly using high-pressure air and electrical cleaning fluid. Inspect and fix the insulation and securement of the high and low voltage lead cables. Place the cleaned stator and rotor in an oven and bake at a constant temperature of 110℃ for 8 hours to obtain a pre-dried stator, pre-dried rotor, and clean housing assembly.

[0061] Step S3: Improvement of core insulation of the stator:

[0062] The pre-dried stator obtained in step S2 is placed in a vacuum pressure impregnation tank, and a vacuum of 150 Pa is drawn and maintained for 2 hours. The composite insulating impregnation resin A obtained in step S1 is injected under vacuum until the winding is completely submerged. The vacuum is removed and a pressure of 0.4 MPa is applied and maintained for 8 hours to obtain the impregnated stator. The impregnated stator is placed in a curing oven with a controllable vibration platform, and a two-step temperature-controlled curing program is started: first, the temperature is raised to 75°C, and mechanical micro-vibration with a frequency of 15 Hz and an amplitude of 0.1 mm is applied and maintained constant for 30 minutes; then the vibration is stopped, and the temperature is raised to 130°C at a rate of 5°C / min, and then raised to 175°C at the same rate of 5°C / min and maintained constant for 10 hours to obtain a stator with a gradient insulation layer.

[0063] Step S4, Mechanical maintenance of the rotor:

[0064] While the stator is being cured in step S3, the pre-dried rotor obtained in step S2 undergoes mechanical maintenance. The old bearings are removed using specialized tools, and brand-new imported NSK bearings are heated and installed in place, with lubricating grease added, resulting in a rotor that has completed maintenance.

[0065] Step S5, Final Assembly:

[0066] A dynamic balancing test is performed on the rotor obtained in step S4 after maintenance to ensure that its imbalance meets the G2.5 accuracy level requirements, thus obtaining a rotor that is dynamically balanced. The stator with gradient insulation layer obtained in step S3, the dynamically balanced rotor, and the clean housing assembly obtained in step S2 are reassembled to complete the final assembly of the generator, resulting in the upgraded generator after maintenance.

[0067] Example 2:

[0068] This embodiment provides a method for improving the H-level insulation performance of a 10kV generator. The steps are basically the same as in Embodiment 1, except that:

[0069] Step S1: Preparation of composite insulating impregnating resin:

[0070] According to the mass fractions, composite insulating impregnating resin B was prepared by using 100 parts of bisphenol A diglycidyl ether type epoxy resin, 88 parts of methyl hexahydrophthalic anhydride, 10 parts of butyl glycidyl ether, 1.0 part of 2-ethyl-4-methylimidazolium, 2 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 100 parts of flake hexagonal boron nitride, and 3 parts of dust-repellent functional filler No. 1 prepared in Preparation Example 1.

[0071] Step S2, Disassembly and pretreatment of the generator:

[0072] The pre-drying process parameters are constant temperature baking at 120℃ for 6 hours.

[0073] Step S3: Improvement of core insulation of the stator:

[0074] Impregnation was performed using composite insulating impregnation resin B. The vacuum pressure impregnation process parameters were: evacuation to 100 Pa and holding for 3 hours, followed by applying a pressure of 0.5 MPa and holding for 6 hours. The parameters for the two-step temperature-controlled curing program were: first, heating to 80°C, applying mechanical micro-vibration at a frequency of 35 Hz and an amplitude of 0.3 mm, and maintaining this position for 45 minutes; then stopping the vibration, heating to 140°C at a rate of 8°C / min, and then heating to 180°C at a rate of 5°C / min and maintaining this temperature for 13 hours.

[0075] The remaining steps and product names are the same as in Example 1.

[0076] Example 3:

[0077] This embodiment provides a method for improving the H-level insulation performance of a 10kV generator. The steps are basically the same as in Embodiment 1, except that:

[0078] Step S1: Preparation of composite insulating impregnating resin:

[0079] According to the mass fractions, composite insulating impregnating resin C was prepared by using 100 parts of bisphenol A diglycidyl ether type epoxy resin, 95 parts of methyl hexahydrophthalic anhydride, 5 parts of butyl glycidyl ether, 1.5 parts of 2-ethyl-4-methylimidazolium, 3 parts of 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 150 parts of plate-like hexagonal boron nitride, and 5 parts of dust-repellent functional filler No. 2 prepared in Preparation Example 2.

[0080] Step S2, Disassembly and pretreatment of the generator:

[0081] The pre-drying process parameters are constant temperature baking at 130℃ for 4 hours.

[0082] Step S3: Improvement of core insulation of the stator:

[0083] Impregnation was performed using composite insulating impregnation resin C. The vacuum pressure impregnation process parameters were: vacuuming to 50 Pa and holding for 4 hours, followed by applying a pressure of 0.6 MPa and holding for 4 hours. The parameters for the two-step temperature-controlled curing program were: first, heating to 85°C, applying mechanical micro-vibration at a frequency of 60 Hz and an amplitude of 0.5 mm, and maintaining this constant temperature for 60 minutes; then stopping the vibration, heating to 150°C at a rate of 10°C / min, and then heating to 185°C at a rate of 5°C / min and maintaining this temperature for 16 hours.

[0084] The remaining steps and product names are the same as in Example 1.

[0085] Note: The housing assembly mentioned in this technical solution refers to the collection of mechanical structural components that constitute the main structure of the generator and undertake the functions of support, positioning, protection, and heat dissipation, excluding the stator and rotor components of the generator core. It mainly includes the base, front and rear end covers, bearing covers, and junction boxes, etc.

[0086] Comparative Examples 1-4:

[0087] Comparative Example 1: Compared with Example 1, the difference is that the composite insulating impregnation resin provided by this invention is not used; instead, a commercially available H-grade epoxy impregnation resin (product model 188#) is used for vacuum pressure impregnation. The curing process does not use a two-step temperature-controlled curing procedure; instead, it is directly cured at 160°C for 16 hours. After curing, an additional layer of commercially available H-grade silicone dustproof clear varnish is sprayed onto the stator winding surface as a surface protection. All other steps are the same.

[0088] Comparative Example 2: Compared with Example 1, the difference is that the composite insulating impregnating resin prepared in step S1 does not contain "dust-repellent functional filler No. 1 obtained in Preparation Example 1", that is, the resin only contains thermally conductive filler and has no dust-repellent function. All other raw material ratios and process steps are exactly the same.

[0089] Comparative Example 3: Compared with Example 1, the difference is that the composite insulating impregnating resin prepared in step S1 does not contain "plate-like hexagonal boron nitride", that is, the resin only contains dust-repellent filler and no high thermal conductivity filler. All other raw material ratios and process steps are exactly the same.

[0090] Comparative Example 4: Compared with Example 1, the difference is that the exact same composite insulating impregnation resin A is used for impregnation, but in the curing stage of step S3, the two-step temperature-controlled curing procedure is not used. Instead, the impregnated stator is directly placed in the curing oven and cured at a constant temperature of 175°C for 12 hours without any mechanical micro-vibration. The remaining steps are the same.

[0091] Test Case 1-Test Case 3:

[0092] Test Example 1:

[0093] 1. Experimental instructions:

[0094] This test aims to quantitatively evaluate the core electrical insulation performance of the generator stator winding after treatment using the method of this invention. The test was conducted in accordance with GB / T 755-2019 "Ratings and Performance of Rotating Electrical Machines" and related standards.

[0095] Test subject:

[0096] Example 1: Original generator before processing (labeled: original state)

[0097] Generators after processing in Examples 1-3 (labeled as: Example 1, Example 2, Example 3)

[0098] The generators after processing in Comparative Examples 1-4 (labeled as: Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4)

[0099] Testing environment: All tests were conducted under standard laboratory conditions, with the ambient temperature controlled at 25℃±2℃ and the relative humidity at 60%±5%. Before testing, all test objects were placed in this environment for more than 24 hours.

[0100] 2. Experimental steps:

[0101] 2.1 Measurement of Insulation Resistance (IR) and Absorption Ratio (AR):

[0102] (1) Preparation: Ensure that the surface of the stator winding leads is clean and dry. Reliably short-circuit the stator U, V and W three-phase winding leads.

[0103] (2) Connection: Use a 5000V digital megohmmeter. Connect the “L” (line) terminal of the tester to the shorting point of the three-phase winding; firmly connect the “E” (ground) terminal to the grounding bolt of the generator frame to ensure that the stator core is properly grounded.

[0104] (3) Test: Start the test and apply a 5000V DC voltage. The system will automatically time the test, marking the 15th second after the voltage is applied. ) and 60 seconds ( The insulation resistance value can be automatically recorded or read manually.

[0105] (4) Discharge: Stop applying pressure after the 60-second test. Keep the wiring in place and use the automatic discharge function inside the megohmmeter to fully discharge the winding until the voltage display is zero before disconnecting the wiring.

[0106] (5) Calculation: Record As the insulation resistance value. Calculate the absorption ratio. .

[0107] 2.2 Partial Discharge (PD) Test:

[0108] (1) Preparation: Use a partial discharge detection system (including a corona-free high voltage power supply, coupling capacitor, detection impedance and PD detector).

[0109] (2) Circuit connection and calibration: Connect the test circuit according to the IEC 60270 standard. Before applying high voltage, use a standard pulse generator to inject a pulse of known charge (e.g., 100 pC) into the test circuit to calibrate the sensitivity and amplitude of the detection system.

[0110] (3) Voltage boost and measurement: After calibration, disconnect the calibration source. Apply AC voltage smoothly while monitoring the background noise level (ensuring it is below 5 pC). Increase the voltage to the rated line voltage of 10 kV and maintain it at this voltage.

[0111] (4) Reading: Monitor the PD spectrum, and after stabilizing for 1 minute, record the maximum partial discharge quantity measured by the system. The unit is picoliters (pC). After measurement, the pressure is gradually reduced to zero.

[0112] 2.3 Power frequency withstand voltage test (high stress assessment):

[0113] (1) Preparation: Use a power frequency withstand voltage tester. The connection method is the same as in item 2.1 (2). The high voltage output terminal is connected to the winding short-circuit point, and the grounding terminal is connected to the frame.

[0114] (2) Settings: Set the test voltage to AC 22kV ( The leakage current (overcurrent protection) threshold is set to 100mA.

[0115] (3) Voltage boost: Start voltage boosting from zero, control the voltage boosting rate to about 0.5-1.0kV / s, and steadily increase to 22kV.

[0116] (4) Holding and monitoring: After the test voltage reaches 22kV, start timing and hold for 60 seconds. During this period, monitor the readings of the voltmeter and ammeter of the test instrument, and observe whether there are any abnormal discharge sounds or flashovers on the test object.

[0117] (5) Voltage reduction and judgment: After 60 seconds of timing, the voltage is smoothly reduced to zero and the high voltage is disconnected. If no breakdown occurs during the process (i.e., the leakage current does not suddenly increase and trigger the protection) and there is no flashover, it is judged as "passed". If a trip occurs, it is judged as "breakdown".

[0118] 3. Experimental data are shown in Table 1:

[0119] Table 1: Test data of core electrical insulation performance

[0120]

[0121] The test data in Table 1 confirms the improvement in core electrical performance of the generator after treatment with this technical solution. The stator winding insulation resistance (12610-19250MΩ) and absorption ratio (2.58-3.09) of Examples 1-3 are significantly higher than those of the original state (845MΩ, 1.28) and Comparative Example 1 (2510MΩ, 1.62). Furthermore, all examples passed the 22kV power frequency withstand voltage test, while the original state failed. The data indicate that the composite insulating impregnation resin and vacuum pressure impregnation process used in this solution effectively restore and improve the insulation strength and dielectric dryness of the windings.

[0122] Partial discharge data further revealed differences in the internal quality of the insulation system. The partial discharge levels of Examples 1-3 (54-81 pC) were significantly lower than those of the original state (1284 pC) and Comparative Example 1 (572 pC). The comparative analysis of Comparative Example 4 (445 pC) and Example 1 (81 pC) is particularly crucial: both used the same impregnation resin, but Comparative Example 4 lacked the mechanical micro-vibration step in the two-step temperature-controlled curing process. This data comparison confirms that applying mechanical micro-vibration plays a decisive role in promoting the escape of residual microbubbles in the impregnation resin and reducing the sources of micro-defects inside the cured insulation.

[0123] Furthermore, the partial discharge level of Comparative Example 3 (277 pC) was significantly higher than that of Example 1 (81 pC). The resin of Comparative Example 3 did not contain lamellar hexagonal boron nitride thermally conductive filler. This data indicates that the high filler content of functional fillers in the composite insulating impregnation resin contributes to optimizing volume shrinkage during curing and improving the overall compactness of the cured insulation system. In summary, the data from Test Example 1 validates that this approach, by combining the composite insulating impregnation resin with a specific curing process involving mechanical micro-vibration, can significantly improve the electrical strength of the insulation system and greatly reduce the level of internal defects.

[0124] Test Example 2:

[0125] 1. Experimental instructions:

[0126] This test aims to quantitatively evaluate the thermal stability of the generator under rated operating conditions after treatment by the method of this invention, that is, to assess the heat dissipation capacity of the insulation system. The test is performed according to the temperature rise test method in GB / T 755-2019 "Rotating Electrical Machines - Ratings and Performance".

[0127] Test subject:

[0128] Example 1: Original generator before processing (labeled: original state)

[0129] Generators after processing in Examples 1-3 (labeled as: Example 1, Example 2, Example 3)

[0130] The generator after processing in Comparative Example 1 (labeled as: Comparative Example 1)

[0131] The generator after processing in Comparative Example 3 (labeled as: Comparative Example 3)

[0132] (Note: The resin composition and curing process of Comparative Examples 2 and 4 are expected to be similar to those of Example 1 or Comparative Example 3 in terms of macroscopic thermal conductivity. This test focuses on verifying the decisive role of thermally conductive fillers, so their data are not listed.)

[0133] Test environment: The ambient temperature was maintained at 25℃±2℃. The test object was placed in a test area without significant external airflow disturbance.

[0134] 2. Experimental steps:

[0135] (1) Preparation: Install the generator under test on the load test bench and connect it coaxially with the test motor (or power meter). Correctly connect the excitation power supply and stator load.

[0136] (2) Sensors: Confirm that the PT100 temperature sensors (usually located in different positions in the slot) embedded inside the generator stator winding are all connected to the temperature monitoring instrument.

[0137] (3) Ambient temperature measurement: At least three temperature sensors shall be installed near the generator cooling air inlet, and the average value of the measured values ​​shall be taken as the ambient temperature. .

[0138] (4) Loading and Operation: Start the generator and bring it to its rated speed. Apply rated voltage, rated current, and rated power factor (i.e., 100%). ).

[0139] (5) Thermal stability monitoring: Continuous operation under this load. Record the readings of all PT100 windings and the ambient temperature every 10 minutes. .

[0140] (6) Stability criterion: When the temperature change rate of all measuring points is less than 1 K / h for one consecutive hour, the generator is considered to have reached a thermally stable state.

[0141] (7) Data recording: Record the temperature of the hottest spot of the stator winding when the thermal stability state is reached. (Or take the average value; here we use the hottest data).

[0142] (8) Calculation: Calculate the winding temperature rise .

[0143] 3. Experimental data are shown in Table 2:

[0144] Table 2: Thermal stability test data under rated load

[0145]

[0146] Table 2 shows the test data indicating the impact of different treatment methods on the temperature rise of the generator windings. The steady-state winding temperature rises (85.8K to 94.2K) in Examples 1-3 are all lower than those in the original state (121.3K) and Comparative Example 1 (114.6K). This data shows that the generator treated with this method has improved heat dissipation under rated load and reduced operating temperature.

[0147] The composite insulating impregnating resin used in this scheme contains lamellar hexagonal boron nitride filler with high thermal conductivity. The vacuum pressure impregnation process fills this filler into the winding insulation structure, creating a heat conduction path between the heat source (copper wire) and the heat sink (iron core). Data from Comparative Example 3 provides direct evidence for this: Comparative Example 3 uses a resin without lamellar hexagonal boron nitride, and its winding temperature rise is 111.5 K, which is close to Comparative Example 1 (114.6 K), but much higher than Examples 1-3. This data comparison confirms that the reduction in winding temperature rise is mainly attributed to the introduction of the thermally conductive filler.

[0148] Furthermore, in Examples 1, 2, and 3, the amount of lamellar hexagonal boron nitride added increases sequentially, and the corresponding winding temperature rises (94.2K, 90.1K, and 85.8K) show a clear decreasing trend. This further verifies the role of thermally conductive fillers in constructing heat conduction pathways. Data from Test Example 2 confirms that this solution, by incorporating high thermal conductivity fillers into the insulating resin and combining it with the VPI process, effectively improves the overall thermal conductivity of the stator winding insulation system and reduces the operating temperature rise of the equipment under rated conditions.

[0149] Test Example 3:

[0150] 1. Experimental instructions:

[0151] This test aims to quantitatively evaluate the hydrophobicity of the surface of the insulation system formed by the method of the present invention, as well as its ability to maintain surface insulation resistance under simulated dirty and humid environments.

[0152] Test subject:

[0153] The smooth surface samples formed after curing the composite insulating impregnating resin of Examples 1-3 (labeled as: surface of Example 1, surface of Example 2, surface of Example 3).

[0154] The smooth surface sample formed after curing with the conventional resin (including topcoat) of Comparative Example 1 (labeled as: Comparative Example 1 surface).

[0155] The smooth surface sample formed after curing the resin (without dust-repellent filler) of Comparative Example 2 (marked as: Comparative Example 2 surface).

[0156] Test environment:

[0157] Contact angle test: ambient temperature 25℃±2℃, relative humidity 60%±5%.

[0158] Anti-flashover test: conducted in an environmentally controlled test chamber at a humidity of 90%±5% RH.

[0159] 2. Experimental steps:

[0160] 2.1 Water contact angle test:

[0161] (1) Preparation: Use the resin components and cure them according to the corresponding process to prepare a 50mm×50mm sample with a smooth and clean surface.

[0162] (2) Cleaning: Clean the sample surface with anhydrous ethanol and deionized water in sequence, and dry it in a drying oven at 60°C for 1 hour.

[0163] (3) Measurement: Place the sample on the stage of the contact angle measuring instrument. Use a micro-syringe to drop 5 μL of deionized water at the center of the sample surface.

[0164] (4) Reading: After the water droplet shape stabilizes (about 10 seconds), the water droplet profile is fitted using the tangent method, and the static water contact angle is measured and recorded. Five different points are measured for each group of samples, and the average value is taken.

[0165] 2.2 Anti-flashover performance simulation test:

[0166] (1) Preparation: Use the sample prepared in step 2.1 (1) above.

[0167] (2) Staining: Prepare a staining suspension (according to GB / T 4585 standard, containing kaolin and NaCl). Apply the staining suspension evenly to the sample surface using a spraying method, controlling the equivalent salinity density (ESDD) to be 0.05 mg / cm³. 2 .

[0168] (3) Drying: Dry the sprayed sample in a 60°C oven for 2 hours to form a uniform solid dirt layer.

[0169] (4) Test: Move the sample with the contamination layer into the high humidity test chamber (90% RH, 25℃). Place two electrodes parallel to each other on the sample surface (30 mm apart).

[0170] (5) Measurement: After the sample surface has been moistened and stabilized (about 1 hour), apply a DC voltage of 500V, use a high resistance meter to measure the surface insulation resistance between the two electrodes, and record it.

[0171] 3. Experimental data are shown in Table 3:

[0172] Table 3: Surface Performance Test Data

[0173]

[0174] The test data in Table 3 show that the water contact angles of the cured resin surfaces in Examples 1-3 (146.2°-151.4°) are significantly higher than those in Comparative Example 1 (96.3°) and Comparative Example 2 (81.7°). The high water contact angles indicate that the surfaces of the examples form a low surface energy state, exhibiting hydrophobicity. This characteristic is attributed to the dust-repellent functional filler contained in the composite insulating impregnating resins of Examples 1-3. During the curing process, this functional filler accumulates at the resin-air interface, altering the physicochemical properties of the cured surface.

[0175] The results of anti-flashover performance simulation tests verified the effectiveness of the aforementioned hydrophobic properties. Under conditions of applied contamination and high humidity, the surface insulation resistance of Examples 1-3 (1480-2150 MΩ) was significantly higher than that of Comparative Example 1 (77 MΩ) and Comparative Example 2 (41 MΩ). This data indicates that the low surface energy hydrophobic surface formed by the functional filler effectively inhibits the formation of a continuous conductive water film on the sample surface after the contaminant layer absorbs moisture, blocking the leakage current path and thus maintaining a high surface insulation resistance.

[0176] The comparison between Comparative Example 2 (without the dust-repellent functional filler) and the Example provides direct evidence for this. The resin matrix of Comparative Example 2 is the same as that of the Example, but its water contact angle (81.7°) and surface insulation resistance (41 MΩ) are both at a low level. This data comparison confirms that the surface hydrophobicity and high surface insulation resistance are not derived from the resin matrix, but are determined by the introduction of the dust-repellent functional filler. Data from Test Example 3 confirms that this approach improves the surface insulation reliability of the insulation system in humid and polluted environments by constructing a functional surface layer within the insulation system.

[0177] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

A method for improving the H-class insulation performance of a 1.10kV generator, characterized in that: Includes the following steps: Step S1: Prepare composite insulating impregnation resin; Step S2: Disassemble the 10kV generator to be maintained to obtain the stator, rotor and housing assembly to be processed; clean and pre-dry the stator and rotor to be processed, and clean the housing assembly to obtain the pre-dried stator, pre-dried rotor and clean housing assembly. Step S3: Vacuum pressure impregnation is performed on the pre-dried stator after step S2, using the composite insulating impregnation resin prepared in step S1, to obtain the impregnated stator; and the impregnated stator is subjected to double-step temperature-controlled curing to obtain a stator with a gradient insulation layer. Step S4: Perform mechanical maintenance on the pre-dried rotor obtained in step S2 to obtain a rotor that has completed maintenance; Step S5: Perform a dynamic balancing test on the rotor obtained in step S4 after maintenance, and reassemble the rotor that has passed dynamic balancing, the stator with gradient insulation layer obtained in step S3, and the clean housing assembly obtained in step S2.

2. The method for improving the H-level insulation performance of a 10kV generator according to claim 1, characterized in that, The composite insulating impregnating resin is made from components comprising the following parts by weight: Bisphenol A diglycidyl ether type epoxy resin: 100 parts; Methylhexahydrophthalic anhydride: 80-95 parts; Butyl glycidyl ether: 5-15 parts; 2-Ethyl-4-methylimidazole: 0.5-1.5 parts; 3-(2,3-epoxypropoxy)propyltrimethoxysilane: 1-3 parts; Plate-shaped hexagonal boron nitride: 50-150 parts; Dust-repellent filler: 1-5 parts.

3. The method for improving the H-level insulation performance of a 10kV generator according to claim 2, characterized in that, The dust-repellent functional filler is prepared through the following steps: 100 parts by weight of hydrophilic fumed silica were vacuum dried at 115°C and then added to 1000 parts by weight of cyclohexane and ultrasonically dispersed to form a suspension. Add 15-25 parts by weight of perfluorooctyltriethoxysilane to the suspension and reflux at 80°C for 6-8 hours; After the reaction is completed, the dust-repellent functional filler is obtained by centrifugation, washing and vacuum drying.

4. The method for improving the H-level insulation performance of a 10kV generator according to claim 1, characterized in that, In step S2, the process parameters for the pre-drying treatment are: constant temperature baking at 110-130℃ for 4-8 hours.

5. The method for improving the H-level insulation performance of a 10kV generator according to claim 1, characterized in that, In step S3, the process parameters for vacuum pressure impregnation are as follows: evacuate to 50-150 Pa and maintain for 2-4 hours, then apply a pressure of 0.4-0.6 MPa and maintain the pressure for 4-8 hours.

6. The method for improving the H-level insulation performance of a 10kV generator according to claim 1, characterized in that, In step S3, the dual-step temperature-controlled curing includes: First step: Apply mechanical micro-vibration with a frequency of 15-60Hz and an amplitude of 0.1-0.5mm to the impregnated stator at a temperature of 75-85℃, and maintain it constant for 30-60 minutes; Second step: Stop the mechanical micro-vibration, raise the temperature to 175-185℃ and keep it at a constant temperature for 10-16 hours.

7. The method for improving the H-level insulation performance of a 10kV generator according to claim 1, characterized in that, In step S4, the mechanical maintenance of the pre-dried rotor includes: removing the old bearing and heating the new bearing before installing it in place.

8. The method for improving the H-level insulation performance of a 10kV generator according to claim 1, characterized in that, In step S5, the dynamic balancing test ensures that the imbalance of the rotor after maintenance meets the G2.5 accuracy level requirements.

9. The method for improving the H-level insulation performance of a 10kV generator according to any one of claims 1 to 8, characterized in that, The method for improving the H-level insulation performance of the 10kV generator is applied to the maintenance of 10kV generators.

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