Preparation method of impregnated insulating laminated board of ultra-high voltage and extra-high voltage transformer

Abstract

The invention provides a preparation method of an impregnated insulating laminated board of an ultra-high voltage transformer. The preparation method sequentially comprises the following steps: cutting a single board, drying the single board, injecting glue into a container, immersing materials, sealing a tank body, performing negative pressure treatment, performing positive pressure treatment, draining the materials, performing hot pressing treatment, performing standing treatment, processing a product and the like. According to the method, the glue proportion can be effectively increased by reducing the thickness of the main material; a new pressure impregnation method is adopted, a paperboard is impregnated in a binding agent and put into a pressure impregnation tank, and the binding agent is completely impregnated through control of positive pressure and negative pressure.

Description

Technical Field

[0001] The invention relates to the technical field of transformer insulation laminate materials, in particular to a method for preparing an impregnated insulation laminate for an ultra-high voltage or extra-high voltage transformer. Background Art

[0002] A large amount of solid insulating materials are required inside the extra-high voltage and ultra-high voltage oil-immersed transformers. Conventional solid insulating materials are made of laminated paperboard, which is easy to shrink, absorb moisture, and compress. Therefore, for some parts with particularly high mechanical strength and assembly precision, conventional insulating materials can no longer meet the design requirements. Under the premise of ensuring the electrical performance of the product, some parts can only be replaced by epoxy or glass fiber insulation materials, and the above insulation materials are extremely expensive.

[0003] Laminated paperboard made by combining paperboard and adhesive is currently the lowest cost and most stable solid insulating material in the transformer manufacturing process. However, since paperboard is composed of paper fibers, quality problems such as deformation, cracking, and shrinkage after moisture absorption often occur during the actual use of laminated paperboard. In addition, most of the main materials of laminated paperboard are made of paperboard, and the mechanical strength of paperboard products is much lower than that of epoxy or glass fiber materials. At present, laminated paperboard is mainly made by applying glue to the surface of the paperboard and then bonding the paperboard by hot pressing (or cold pressing). Although the adhesive itself has sufficient mechanical strength and electrical properties, the method of applying glue on the surface is affected by the permeability of the adhesive, and the proportion is too small for laminated materials (about 10%). Therefore, it is difficult to improve the performance of the product by increasing the amount of glue applied. Summary of the invention

[0004] The technical problem to be solved by the present invention is: in order to overcome the deficiencies in the prior art, the present invention provides a method for preparing an impregnated insulating laminate for an ultra-high voltage transformer.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing an impregnated insulating laminate for an ultra-high voltage transformer, comprising the following steps: S1: Cutting of veneer: using cardboard with a thickness of 1mm-1.5mm to cut according to product parameters to obtain veneer raw materials; S2: veneer drying, using a vacuum tank to dry the veneer raw material obtained in step S1, the drying parameters are: temperature 105°C ± 5°C, vacuum degree <2000pa, drying time >14h; S3: filling the container with glue, filling the impregnation container with the modified adhesive; S4: Material immersion: The dried veneer in step S2 is taken out from the vacuum tank and cooled. After the veneer is cooled to below 60°C, it is immersed in the binder in the immersion container. S5: sealing the tank body, pushing the impregnation container into the pressure impregnation tank, and sealing the pressure impregnation tank; S6: Negative pressure treatment: the inside of the pressure impregnation tank is pumped to negative pressure, and the negative pressure state is maintained for at least 1 hour to discharge the air in the adhesive and the veneer; S7: Positive pressure treatment, release the negative pressure, inject gas into the pressure impregnation tank to convert the internal pressure to positive pressure, the duration is at least 3 hours, and the adhesive is pressed into the veneer by pressure; the gas injected here is air.

[0006] S8: draining the material. After the positive pressure treatment is completed, the pressure in the pressure impregnation tank is released, the impregnation container is pulled out of the pressure impregnation tank, and then the veneer is taken out of the impregnation container and drained; S9: Hot pressing treatment. After the veneer is drained, it is placed in a hot press for hot pressing. Hot pressing parameters: unit pressure is 6-8Mpa, temperature is 120℃±5, and hot pressing time is determined according to the total thickness of the product; (the thicker the product, the longer the hot pressing time) S10: static placement treatment: after the hot pressing treatment is completed, the single board is taken out from the hot press and unloaded and statically placed for at least one day; S11: Product processing, subsequent processing of the single board after static storage.

[0007] Preferably, the negative pressure is at least -0.098 MPa.

[0008] Preferably, the positive pressure is 2.0Mpa-3.0Mpa.

[0009] Furthermore, in order to achieve impregnation, the impregnation system includes a pressure impregnation tank and an impregnation container, wherein the impregnation container is arranged inside the pressure impregnation tank, and a flat car is provided at the bottom, and the bottom of the flat car is connected to a ground rail arranged in the pressure impregnation tank.

[0010] Furthermore, the pressure impregnation tank includes a tank body and a sealed tank cover arranged on the tank body, and the top of the tank body is provided with a negative pressure inlet and a positive pressure inlet, the negative pressure inlet is used to perform negative pressure treatment on the pressure impregnation tank, and the positive pressure inlet is used to perform positive pressure treatment on the pressure impregnation tank.

[0011] Furthermore, the top of the tank body is also provided with a detection port, a safety valve and an airtight device inlet, wherein the detection port is used to monitor the internal pressure state; the safety valve is used for operational safety and automatically releases pressure when the pressure exceeds the set value; and the airtight device inlet is used to connect the air pipe for pressurized sealing of the tank cover.

[0012] Furthermore, a pressure relief port and a sewage outlet are provided at the bottom of the tank body. The pressure relief port is used to release the pressure in the pressure-sealed tank; and the sewage outlet is used to discharge the dirt in the pressure-sealed tank.

[0013] Furthermore, a rotating frame is provided on the sealed tank cover, and the left side of the rotating frame is rotatably connected to the tank body through a rotating shaft. The sealed tank cover and the left side of the tank body are provided with mutually matching locking components, and the sealed tank cover can be locked on the tank body and sealed through the locking components; a support frame is provided at the bottom of the tank body for supporting it on the ground; and a lifting lug is provided on the top of the tank body for easy lifting.

[0014] Furthermore, the conventional insulating adhesive has poor permeability, and the intrinsic molecular structure of the adhesive needs to be improved and the molecular weight distribution controlled. When the required solid content is met, the viscosity of the glue is reduced, thereby increasing the permeability of the glue and improving the interlayer bonding force. Therefore, the modified adhesive is obtained by reacting a phenolic compound with an aldehyde compound under alkaline catalyst conditions, and adding a solvent through vacuum distillation to obtain a liquid thermosetting phenolic resin. By improving the structure and controlling the distribution of the resin molecular weight during the glue synthesis process, the permeability of the adhesive is enhanced and the strength of the laminated product is improved.

[0015] The beneficial effects of the present invention are: (1) Generally, insulating laminated materials use cardboard with a thickness of ≥3 mm as the main material, while the present invention uses cardboard with a thickness of 1-1.5 mm as the main material of the laminated cardboard, which greatly reduces the thickness of the main material. Since the glue is applied between layers, the proportion of glue can be effectively increased by reducing the thickness of the main material.

[0016] (2) Traditional insulating adhesives have poor permeability, and the viscosity and solid content of the glue need to be modified to increase the permeability of the adhesive. The present invention greatly improves the permeability of the adhesive by controlling the molecular weight during the synthesis of the adhesive.

[0017] (3) The traditional surface coating method is difficult to ensure that the adhesive completely penetrates the paperboard due to the short gluing time. The present invention uses a new pressure impregnation method: the paperboard is impregnated with the adhesive and placed in a pressure impregnation tank, and the adhesive is completely impregnated by controlling the positive and negative pressures. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0019] Figure 1 It is a schematic flow chart of a method for preparing an impregnated insulating laminate for an ultra-high voltage transformer of the present invention.

[0020] Figure 2 It is a schematic diagram of the structure of a pressure impregnation tank.

[0021] Figure 3 yes Figure 2 Schematic diagram of the cross-sectional structure of AA.

[0022] Figure 4 It is a schematic diagram of the side structure of the pressure impregnation tank.

[0023] In the figure: 1. pressure impregnation tank, 1.1. tank body, 1.2. sealing tank cover, 1.3. support frame, 1.4. pressure relief port, 1.5. sewage outlet, 1.6. detection port, 1.7. lifting lug, 1.8. negative pressure inlet, 1.9. safety valve, 1.10. positive pressure inlet, 1.11. airtight device inlet, 1.12. locking assembly, 1.13. rotating frame, 1.14. rotating shaft, 2. impregnation container, 3. flat car, 4. ground rail. DETAILED DESCRIPTION

[0024] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams that only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention, and directions and references (e.g., up, down, left, right, etc.) may only be used to help describe the features in the drawings. Therefore, the following specific embodiments are not to be taken in a limiting sense, and the scope of the subject matter claimed is limited only by the attached claims and their equivalents.

[0025] like Figure 1 As shown, a method for preparing an impregnated insulating laminate for an ultra-high voltage transformer of the present invention comprises the following steps: S1: Cutting single board materials, using cardboard with a thickness of 1 mm-1.5 mm to cut materials according to product parameters to obtain single board raw materials; in this embodiment, cardboard with a thickness of 1 mm or 1.5 mm is used as the raw material; S2: veneer drying, using a vacuum tank to dry the veneer raw material obtained in step S1, the drying parameters are: temperature 105°C ± 5°C, vacuum degree <2000pa, drying time >14h; S3: filling the container with glue, filling the impregnation container 2 with the modified adhesive; S4: Material immersion: The dried veneer in step S2 is taken out from the vacuum tank and cooled. After the veneer is cooled to below 60°C, it is immersed in the binder in the immersion container 2. S5: sealing the tank body 1.1, pushing the impregnation container 2 into the pressure impregnation tank 1, and sealing the pressure impregnation tank 1; S6: negative pressure treatment, the interior of the pressure impregnation tank 1 is evacuated to negative pressure, and the negative pressure state is maintained for at least 1 hour to discharge the air in the adhesive and the veneer; preferably, the negative pressure is at least -0.098 MPa; S7: positive pressure treatment, releasing the negative pressure, injecting gas into the pressure impregnation tank 1 to convert the internal pressure into positive pressure, the duration is at least 3 hours, and the adhesive is pressed into the veneer by pressure; preferably, the positive pressure is 2.0Mpa-3.0Mpa; S8: draining the material. After the positive pressure treatment is completed, the pressure in the pressure impregnation tank 1 is released, the impregnation container 2 is pulled out of the pressure impregnation tank 1, and then the veneer is taken out of the impregnation container 2 and drained; S9: Hot pressing treatment. After the veneer is drained, it is placed in a hot press for hot pressing. Hot pressing parameters: unit pressure is 6-8Mpa, temperature is 120℃±5, and hot pressing time is determined according to the total thickness of the product; (the thicker the product, the longer the hot pressing time) S10: static placement treatment: after the hot pressing treatment is completed, the single board is taken out from the hot press and unloaded and statically placed for at least one day; S11: Product processing, subsequent processing of the single board after static storage.

[0026] like Figure 2 and Figure 3 As shown, the pressure impregnation tank 1 comprises a tank body 1.1 and a sealed tank cover 1.2, wherein a rotating frame 1.13 is arranged on the sealed tank cover 1.2, and the left side of the rotating frame 1.13 is rotatably connected to the tank body 1.1 via a rotating shaft 1.14, and the left side of the sealed tank cover 1.2 and the tank body 1.1 are provided with mutually matching locking components 1.12, through which the sealed tank cover 1.2 can be locked on the tank body 1.1 and the sealing between the two can be ensured, and when the sealed tank cover 1.2 needs to be opened, the locking component 1.12 is unlocked, and then the rotating frame 1.13 is pulled, so that the rotating frame 1.13 drives the sealed tank cover 1.2 to rotate around the rotating shaft 1.14, thereby opening it.

[0027] A support frame 1.3 is provided at the bottom of the tank body 1.1 for supporting it on the ground. A pressure relief port 1.4 and a sewage outlet 1.5 are also provided at the bottom of the tank body 1.1. Due to its heavy weight, a crane or a crane is required for moving it. Therefore, a plurality of lifting ears 1.7 are provided on the top of the tank body 1.1 to facilitate the lifting of the pressure impregnation tank 1 when it is moved. A detection port 1.6, a negative pressure inlet 1.8, a positive pressure inlet 1.10, a safety valve 1.9 and an airtight device inlet 1.11 are also provided on the top of the tank body 1.1. The detection port 1.6 is used to monitor the internal pressure state; the safety valve 1.9 is used for the safety of operation and automatically releases the pressure when it exceeds the set value; the airtight device inlet 1.11 is used to connect the air pipe for the pressurized seal of the sealed tank cover 1.2.

[0028] like Figure 4 As shown, the impregnation system includes a pressure impregnation tank 1 and an impregnation container 2. The impregnation container 2 is arranged inside the pressure impregnation tank 1, and a flat car 3 is provided at the bottom. The bottom of the flat car 3 is connected to a ground rail 4 arranged in the pressure impregnation tank 1. By pulling the flat car 3 to move on the ground rail 4, the impregnation container 2 can be driven in and out of the pressure impregnation tank 1, which is convenient for loading and unloading.

[0029] In this embodiment, the modified binder is a phenolic compound and an aldehyde compound reacted under alkaline catalyst conditions, and a liquid thermosetting phenolic resin is obtained by adding a solvent through vacuum distillation. Wherein, the phenolic compound includes: one or more of phenol, bisphenol A, cardanol, and naphthol; preferably phenol. The aldehydes include: one or more of formaldehyde, glyoxal, butyraldehyde, glutaraldehyde, paraformaldehyde, and furfural. Preferably formaldehyde and glyoxal. The catalyst includes one or more of sodium hydroxide, potassium hydroxide, magnesium oxide, calcium oxide, ammonia water, urotropine, triethylamine, triethanolamine, and diethylamine, preferably ammonia water and triethylamine. The solvent includes: one or more of methanol, ethanol, ethylene glycol, glycerol, 1,2-propylene glycol, furfuryl alcohol, acetone, butanol, butanone, and ethyl acetate. Preferably methanol and ethanol.

[0030] Comparison was made before and after the adhesive was improved.

[0031] Example: According to the binder preparation method of the present invention: 100g of phenol and 116g of formaldehyde (37% aqueous solution) are mixed, 27g of 18% ammonia solution is added, the temperature is raised to 90-95°C and the reaction is carried out at a constant temperature for 2 hours, vacuum distillation is slowly performed, the vacuum pressure is maintained at -0.09Mpa, vacuum distillation is performed to 5% water, 50g of ethanol is added, and the mixture is stirred to obtain a phenolic resin, i.e., a modified binder.

[0032] Comparative Example: According to the preparation method of ordinary binder: mix 100g phenol and 105g formaldehyde (37% aqueous solution), add 3g triethylamine, heat to 70-75℃ and react at constant temperature for 2 hours, then add 16.67g 18% ammonia solution, heat to 90-95℃, react at constant temperature for 1-2 hours, detect that the molecular weight of the resin meets the standard, slowly perform vacuum distillation, maintain the vacuum pressure at -0.09Mpa, vacuum distill to 5% water, add 50g ethanol, stir well to obtain phenolic resin.

[0033] Table 1 Performance comparison of common binder and modified binder

[0034] From the content of Table 1 above, it can be seen that the viscosity of the modified binder is 520 cp / 25°C, while the viscosity of the ordinary binder is 265 cp / 25°C, and the viscosity is significantly increased.

[0035] The laminated board prepared by conventional method was compared with the impregnated laminated board prepared by the preparation method of the present invention, and the performances thereof are shown in Table 2: Table 2 Comparison of laminated paperboard properties

[0036] As can be seen from Table 2, the bending strength represents the mechanical strength of the material. The mechanical strength of the impregnated laminated paperboard is about 50% higher than that of the conventional laminated paperboard. The shrinkage rate is the shrinkage of the material size when it is dried to an absolute dry state. In actual use, the smaller the shrinkage rate of the product, the higher the assembly accuracy. The shrinkage rate of the impregnated laminated paperboard is 50% smaller than that of the conventional laminated paperboard.

[0037] At present, in the field of UHV transformers, laminated paperboard processed by this process can be used in products with high requirements for mechanical strength and shrinkage, such as static ring skeletons, pressure support plates, and end rings. It can also be used for the manufacture of screws and nuts in the assembly process.

[0038] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the scope of the present invention through the above description. The technical scope of this invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing an impregnated insulating laminate for an ultra-high voltage transformer, characterized in that: The following steps are involved: S1: Cutting of veneer: using cardboard with a thickness of 1mm-1.5mm to cut according to product parameters to obtain veneer raw materials; S2: veneer drying, using a vacuum tank to dry the veneer raw material obtained in step S1, the drying parameters are: temperature 105°C ± 5°C, vacuum degree <2000pa, drying time >14h; S3: filling the container with glue, filling the impregnation container with the modified adhesive; S4: Material immersion: The dried veneer in step S2 is taken out from the vacuum tank and cooled. After the veneer is cooled to below 60°C, it is immersed in the binder in the immersion container. S5: sealing the tank body, pushing the impregnation container into the pressure impregnation tank, and sealing the pressure impregnation tank; S6: Negative pressure treatment: the inside of the pressure impregnation tank is pumped to negative pressure, and the negative pressure state is maintained for at least 1 hour to discharge the air in the adhesive and the veneer; S7: Positive pressure treatment, release the negative pressure, inject gas into the pressure impregnation tank to turn the internal pressure into positive pressure, the duration is at least 3 hours, and the adhesive is pressed into the veneer by pressure; S8: draining the material. After the positive pressure treatment is completed, the pressure in the pressure impregnation tank is released, the impregnation container is pulled out of the pressure impregnation tank, and then the veneer is taken out of the impregnation container and drained; S9: Hot pressing treatment. After the veneer is drained, it is placed in a hot press for hot pressing. Hot pressing parameters: unit pressure is 6-8Mpa, temperature is 120℃±5, and hot pressing time is determined according to the total thickness of the product; (the thicker the product, the longer the hot pressing time) S10: static placement treatment: after the hot pressing treatment is completed, the single board is taken out from the hot press and unloaded and statically placed for at least one day; S11: Product processing, subsequent processing of the single board after static storage.

2. The method for preparing the impregnated insulating laminate for the ultra-high voltage transformer according to claim 1, characterized in that: The negative pressure is at least -0.098Mpa.

3. The method for preparing the impregnated insulating laminate for the ultra-high voltage transformer according to claim 1, characterized in that: The positive pressure is 2.0Mpa-3.0Mpa.

4. The method for preparing the impregnated insulating laminate for the ultra-high voltage transformer according to claim 1, characterized in that: The impregnation container is arranged inside the pressure impregnation tank, and a flat car is arranged at the bottom, and the bottom of the flat car is connected to a ground rail arranged in the pressure impregnation tank.

5. The method for preparing the impregnated insulating laminate for the ultra-high voltage transformer according to claim 4, characterized in that: The pressure impregnation tank comprises a tank body and a sealed tank cover arranged on the tank body. The top of the tank body is provided with a negative pressure inlet and a positive pressure inlet. The negative pressure inlet is used for negative pressure treatment of the pressure impregnation tank, and the positive pressure inlet is used for positive pressure treatment of the pressure impregnation tank.

6. The method for preparing the impregnated insulating laminate for the ultra-high voltage transformer according to claim 5, characterized in that: The top of the tank body is also provided with a detection port, a safety valve and an airtight device inlet, wherein the detection port is used to monitor the internal pressure state; the safety valve is used for operation safety and automatically releases pressure when the pressure exceeds the set value; the airtight device inlet is used to connect the air pipe for pressurized sealing of the tank cover.

7. The method for preparing the impregnated insulating laminate for the ultra-high voltage transformer according to claim 5, characterized in that: The bottom of the tank body is also provided with a pressure relief port and a sewage outlet. The pressure relief port is used to release the pressure in the pressure-sealed tank; the sewage outlet is used to discharge the dirt in the pressure-sealed tank.

8. The method for preparing the impregnated insulating laminate for the ultra-high voltage transformer according to claim 5, characterized in that: The sealed tank cover is provided with a rotating frame, the left side of the rotating frame is rotatably connected to the tank body through a rotating shaft, and the sealed tank cover and the left side of the tank body are provided with mutually matching locking components, through which the sealed tank cover can be locked on the tank body and sealed; a supporting frame is provided at the bottom of the tank body for supporting it on the ground; and a lifting lug is provided on the top of the tank body for easy lifting.

9. The method for preparing the impregnated insulating laminate for the ultra-high voltage transformer according to claim 1, characterized in that: The modified binder is prepared by reacting a phenol compound with an aldehyde compound under alkaline catalyst conditions, and adding a solvent through vacuum distillation to obtain a liquid thermosetting phenolic resin.

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