GB2640008A - High-voltage winding, preparation method therefor, and use thereof - Google Patents

Abstract

The present application relates to the technical field of insulating dry-type transformers, and in particular to a high-voltage winding, a preparation method therefor, and a use thereof. The present application provides a preparation method for a high-voltage winding, comprising the following steps: using a silicone rubber solution to carry out first vacuum casting on an uncast high-voltage winding, and then carrying out first curing molding to obtain primarily cast high-voltage winding; and winding glass fiber mesh fabrics on the inner side and the outer side of the primarily cast high-voltage winding, then using a polyurethane resin solution to carry out second vacuum casting, and carrying out second curing molding to obtain the high-voltage winding. A copper material wrapped in the high-voltage winding can be conveniently recovered.

Description

HIGH-VOLTAGE WINDING AND PREPARATION METHOD AND USE THEREOF

[0001] The present application claims priority to Chinese Patent Application CN202311475629.7 filed with the China National Intellectual Property Administration (CNIPA) on November 07, 2023 and entitled "HIGH-VOLTAGE WINDING AND PREPARATION METHOD AND USE THEREOF", which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of insulating dry-type transformers, and in particular to a high-voltage winding and a preparation method and use thereof

BACKGROUND

[0003] Traditional epoxy resin dry-type transformers use an epoxy resin as an insulating material, and the epoxy resin is cast and cured under vacuum to form a high-strength fiber-reinforced plastic structure. The epoxy resin dry-type transformer has characteristics such as excellent electrical performance, strong lightning impulse resistance, strong short circuit resistance, small size, and light weight.

[0004] However, the vitrified solid formed after the vitrification of epoxy resin has a very large brittleness and an elongation at break of only 2%. Although a glass fiber network is added as a filler inside and outside a coil, when the coil is used in low-temperature and high-temperature environments, photovoltaic farms, wind farms, and energy storage power stations, there will be extreme working conditions such as large load changes, drastic changes in indoor and outdoor working temperatures, and high harmonic wave contents, which will result in the excessive local temperature rise, and the uneven heating and cracking of a resin. In addition, the thickness of the resin layer at the tapping part with a thicker insulation of the coil reaches 40 mm to 80 mm, while the thickness of the wire part with a thinner resin layer of the coil is only 2 mm to 6 mm. Since the expansion coefficient of a copper wire is 17 x 10'/°C and the expansion coefficient of an epoxy resin is about 60 x 10-6/°C, the two materials have inconsistent shrinkage rates, which can very easily cause the cracking of a winding. Moreover, the vitrified solid formed after the curing of the epoxy resin has a very high strength. As a result, once the service life of the transformer expires at a later stage, it is extremely difficult to strip the insulating material to recover the copper wire.

SUMMARY

[0005] An object of the present disclosure is to provide a high-voltage winding and a preparation method and use thereof It is very convenient to recover a copper material wrapped inside the high-voltage winding.

100061 To realize the above object, the present disclosure provides the following technical solutions: 100071 The present disclosure provides a method for preparing a high-voltage winding, including: 100081 subjecting a high-voltage winding before casting to a first vacuum casting using a silicone rubber solution, and then conducting a first curing and forming to obtain a high-voltage winding after first casting; and 100091 winding a fiberglass mesh on inner and outer sides of the high-voltage winding after first casting, subjecting a resulting high-voltage winding to a second vacuum casting using a polyurethane resin solution, and then conducting a second curing and forming to obtain the high-voltage winding.

100101 In some embodiments, the silicone rubber solution includes liquid polydimethylsiloxane, polymethylhydrosiloxane, a platinum ethylene complex, aluminum oxide, and boron nitride in a mass ratio of (22-32): (25-31): (25-35): (5-8): (5-10).

100111 In some embodiments, the first vacuum casting is conducted with a vacuum degree of 70 Pa to 100 Pa for 40 min to 60 min, and during the first vacuum casting, a casting tank has a vacuum temperature of 80°C and a mold temperature of 70°C; and 100121 after the first vacuum casting is completed, the method further includes: placing a resulting material under a vacuum state for 30 min to 40 min while applying a positive pressure of 0.2 MPa.

100131 In some embodiments, the first curing and forming is conducted by heating a resulting material obtained after the first vacuum casting from room temperature to a temperature of 80±5°C, and holding at the temperature for 5 h, then heating to a temperature of 1105°C, and holding at the temperature for 4 h, then heating to a temperature of 130±5°C, and holding at the temperature for 6 h to 8 h, and cooling.

100141 In some embodiments, the polyurethane resin solution includes a polyurethane resin and a curing agent; and 100151 a mass ratio of the polyurethane resin to the curing agent is 3: 1.

100161 In some embodiments, the second vacuum casting is conducted with a vacuum degree of 70 Pa to 100 Pa for 10 min to 15 min, and during the second vacuum casting, a casting tank has a vacuum temperature of 80°C and a mold temperature of 70°C; and 100171 after the second vacuum casting is completed, the method further includes: placing a resulting material under a vacuum state for 5 min while applying a positive pressure of 0.2 MPa.

[0018] In some embodiments, the second curing and forming is conducted by heating a resulting material obtained after the second vacuum casting from room temperature to a temperature of 80±5°C, and holding at the temperature for 0.5 h, then heating to a temperature of 110±5°C, and holding at the temperature for 1 h, then heating to a temperature of 130+5°C, then holding at the temperature for 1.5 h, and cooling.

[0019] In some embodiments, casting molds used for the first vacuum casting and the second vacuum casting each independently include a casting inner mold 1, an end ring 2, a panel 3, and a casting outer mold 4; [0020] an outer diameter of a casting inner mold used for the second vacuum casting is 5 mm smaller than an inner diameter of a casting inner mold used for the first vacuum casting; [0021] an outer diameter of an end ring used for the second vacuum casting is 5 mm larger than an outer diameter of an end ring used for the first vacuum casting, and an inner diameter of the end ring used for the second vacuum casting is 5 mm smaller than an inner diameter of the end ring used for the first vacuum casting; [0022] a width of a panel used for the second vacuum casting is 20 mm larger than a width of a panel used for the first vacuum casting; and [0023] an outer diameter of a casting outer mold used for the second vacuum casting is 5 mm larger than an outer diameter of a casting outer mold used for the first vacuum casting.

[0024] In some embodiments, before the first vacuum casting, the method further includes: preheating the silicone rubber solution, and the preheating is conducted by placing the silicone rubber solution in an oven at 70°C, preheating for 3 h, then stirring at a temperature of 60°C to 65°C for 1 h to 1.5 h, while vacuuming to 120 Pa to 150 Pa.

[0025] In some embodiments, the high-voltage winding after first casting has a Shore hardness of 60 HA to 70 HA.

[0026] In some embodiments, the fiberglass mesh is an H-grade fiberglass mesh having a thickness of 4 mm to 6 mm.

[0027] In some embodiments, the curing agent includes polymethylene polyphenylene isocyanate and diphenylmethane diisocyanate; and a mass ratio of the polymethylene polyphenylene isocyanate to the diphenylmethane diisocyanate is 3: 1.

[0028] In some embodiments, before the second vacuum casting, the method further includes: preheating the polyurethane resin solution, and the preheating is conducted by placing the polyurethane resin solution in an oven at 70°C, preheating for 3 h, then stirring at a temperature of 60°C to 65°C for 1 h to 1.5 h, while vacuuming to 120 Pa to 150 Pa.

[0029] The present disclosure also provides a high-voltage winding prepared by the method described in the above technical solutions, including a first polyurethane layer as an inner layer, a second polyurethane layer as an outer layer, and a silicone rubber layer filled in a middle.

[0030] The present disclosure also provides use of the high-voltage winding described in the above technical solutions in an insulating dry-type transformer.

[0031] In some embodiments, the insulating dry-type transformer includes the high-voltage winding 9, a low-voltage winding 10, an iron core 11, and a clamp 12.

[0032] The present disclosure provides a method for preparing a high-voltage winding, including: subjecting a high-voltage winding before casting to a first vacuum casting using a silicone rubber solution, and then conducting a first curing and forming to obtain a high-voltage winding after first casting; and winding a fiberglass mesh on inner and outer sides of the high-voltage winding after first casting, subjecting a resulting high-voltage winding to a second vacuum casting using a polyurethane resin solution, and then conducting a second curing and forming to obtain the high-voltage winding. In the present disclosure, two times of vacuum casting are used to prepare a polyurethane resin hard shell outside and inside of the high-voltage winding. The electrically conductive material included in the middle layer is a silicone rubber material. The silicone rubber material is soft (with an elastic damping effect, a slightly low hardness, and a Shore hardness of about 60 HA), and can be removed by crushing, incineration, and chemical degradation. Therefore, it is very convenient to recover a copper material wrapped inside the high-voltage winding of the present disclosure. The problem that it is extremely difficult to strip an insulating material to recover a copper wire at the end of the life of the traditional epoxy resin dry-type transformer, in which the epoxy resin cures to form a vitrified solid, is well solved. In addition, the preparation method of the present disclosure has characteristics such as environmental friendliness, non-toxicity, strong overload capacity, high temperature resistance, and outstanding flame resistance. The silicone rubber has outstanding properties, such as a hardness of greater than 70 HA, a tensile strength of greater than 1.5 MTN, an elongation at break of higher than 50%, a flame resistance grade of VO, and a breakdown voltage of up to 25 kV/mm. A hard-soft-hard combination redundancy insulation structure is adopted, which can adapt especially to various harsh environments such as plateau, severe-cold, high-humidity, dusty, and thundery environments and will not cause the cracking of a winding due to excessive changes in load and temperature. The silicone rubber material has an elastic damping effect, and can reduce noise.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. I is a schematic diagram showing the overall structure of the casting mold used for the first vacuum casting and the second vacuum casting according to the present disclosure, where 1-a casting inner mold, 2-an end ring, 3-a panel, and 4-a casting outer mold.

[0034] FIG. 2 is a schematic diagram showing the structure of the casting inner mold according to the present disclosure.

[0035] FIG. 3 is a schematic diagram showing the structure of the end ring according to the present disclosure.

[0036] FIG. 4 is a schematic diagram showing the structure of the panel according to the present disclosure, where 5-a wire-lead-out hole.

[0037] FIG. 5 is a schematic diagram showing the structure of the casting outer mold according to the present disclosure.

[0038] FIG. 6 is a schematic diagram showing the structure of the winding machine used for the winding according to the present disclosure.

[0039] FIG. 7 is a schematic diagram showing the structure of the comb-shaped stay used for preparing the high-voltage winding before casting according to the present disclosure.

[0040] FIG. 8 shows a schematic diagram of winding during the preparation of the high-voltage winding before casting according to the present disclosure, [0041] FIG. 9 is a schematic diagram showing the structure of the high-voltage winding according to the present disclosure, where 6-a first polyurethane layer, 7-a second polyurethane layer, and 8-a silicone rubber layer.

[0042] FIG. 10 is a schematic diagram showing the structure of the insulating dry-type transformer according to the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The present disclosure provides a method for preparing a high-voltage winding, including the following steps: [0044] subjecting a high-voltage winding before casting to a first vacuum casting using a silicone rubber solution, and then conducting a first curing and forming to obtain a high-voltage winding after first casting; and [0045] winding a fiberglass mesh on inner and outer sides of the high-voltage winding after first casting, subjecting a resulting high-voltage winding to a second vacuum casting using a polyurethane resin solution, and then conducting a second curing and forming to obtain the high-voltage winding.

[0046] In some embodiments of the present disclosure, casting molds used for the first vacuum casting and the second vacuum casting each independently include a casting inner mold 1, an end ring 2, a panel 3, and a casting outer mold 4 (an overall structure of the casting molds is shown in FIG. 1 and split views for the casting molds are shown in FIG. 2 to FIG. 5).

[0047] In some embodiments of the present disclosure, an inner diameter of a casting inner mold used for the second vacuum casting is 5 mm smaller than an inner diameter of a casting inner mold used for the first vacuum casting; an outer diameter of an end ring used for the second vacuum casting is 5 mm larger than an outer diameter of an end ring used for the first vacuum casting, and an inner diameter of the end ring used for the second vacuum casting is 5 mm smaller than an inner diameter of the end ring used for the first vacuum casting; a width of a panel used for the second vacuum casting is 20 mm larger than a width of a panel used for the first vacuum casting; and an outer diameter of a casting outer mold used for the second vacuum casting is 5 mm larger than an outer diameter of a casting outer mold used for the first vacuum casting.

100481 In some embodiments of the present disclosure, the first vacuum casting is conducted by placing the high-voltage winding before casting between the casting inner mold and the casting outer mold of the casting mold, and then subjecting the high-voltage winding before casting to the first vacuum casting using the silicone rubber solution.

100491 In some embodiments of the present disclosure, placing the high-voltage winding before casting between the casting inner mold and the casting outer mold of the casting mold is conducted by a process including the following steps: 100501 clearing foreign matter on surfaces (an outer membrane and a wiring board) of the high-voltage winding before casting; applying evenly a release agent on surfaces of the casting outer mold and the panel, and then wiping cleanly the surfaces of the applied casting outer mold and the panel with a cotton cloth; pressing a sealing rubber strip into each of sealing grooves at two sides of the panel 3, and trimming two ends of the sealing rubber strip; installing the wiring board on the casting outer mold 4; penetrating a process screw on each tapping nut into a corresponding position on the wiring board, adjusting the screw to a center position of a hole, and screwing up through a screw cap to make the tapping nut firmly connected to the wiring board; adjusting a protrusion of the end ring 2 (FIG. 3) to align with the panel 3 (FIG. 4), and checking whether a height of a cast is consistent with a corresponding height specified in a drawing; clearing foreign matter on a coil by a dust collector; sleeving the casting outer mold 4 (FIG. 5) and tightening with a tightener; arranging a pressing strip at a position in contact with the wiring board; and tightly clamping the casting outer mold 4 (FIG. 5) with the panel (FIG. 4) through a "W-shaped clamp to make the two fit tightly (FIG. 1).

100511 In some embodiments of the present disclosure, before using the casting mold, a newly-made mold is fully disassembled, and checked whether the appearance and size are qualified. The contact position between an end plate and the mold should be tightly fitted to each other. The burrs and iron chips on the mold are cleared using a polisher and sandpaper, and then the mold is thoroughly cleaned with alcohol to remove oil stains and foreign matter on the mold.

Then the casting mold is placed in an electric oven, baked at 180+5°C for 3 h, and then taken out of the electric oven, then the release agent is evenly brushed on the casting mold while it is still hot, and then the casting mold is placed in the electric oven once again, baked at 180±5°C for 3 h and wiped with a cotton cloth to remove the release agent.

[0052] In the present disclosure, the high-voltage winding before casting is conducted by a process as follows: [0053] The casting inner mold (FIG. 2) used for the first vacuum casting is placed on a pressing plate with a sealing gasket. End rings (FIG. 3) each are sleeved from top to bottom, and the end rings are adjusted to two ends (they remain in a consistent main direction throughout the sleeving process), respectively. The casting inner mold (FIG. 2) is adjusted once to a center position of a lower pressing plate, thereby avoiding the occurrence of a temporary pressing plate. The casting inner mold I_ (FIG. 2) is fixed on the lower pressing plate from inside through 4 pull screws, and a transmission square steel is penetrated. After the casting inner mold is fixed, a winding machine is arranged to be ready for winding (FIG. 6).

[0054] Two layers of H-grade fiberglass mesh layers that are at the same height as the coil are wound around the casting inner mold (FIG. 1), and comb-shaped stays are evenly distributed outside in 6 to 8 equal portions (FIG. 7) and fixed on a fiberglass mesh through a glass fabric tape.

[0055] The winding machine is started to begin winding. The high-voltage winding adopts a disc structure and a continuous coil (FIG. 8). A root of each wire disc is separated from upper and lower wire discs through a NOMEX paper channel, wrapped with an NOMEX paper tape, and tied with a 0.12 x 25 mm fiberglass tape. A wire transition from the previous disc to the next disc is wrapped with two NOMEX paper layers in a half-lapping manner. After a wire turn is bent, it is wrapped with two layers of H-grade fiberglass mesh that are at the same height as the coil.

[0056] If airway plates are arranged between coil layers, POM airway plates as specified in a drawing are sleeved with glass fabric sleeves, tied tightly at two ends with glass fabric tapes, and then arranged side by side next to a comb-shaped stay (FIG. 7) at a specified layer to form a circle, and lower ends of the airway plates each are inserted into a locating slot. After the airway plates are arranged, outer diameters of the airway plates are measured, and wire turns outside the airway plates are continuously wound. When a coil wound with a plurality of wires in parallel needs to be transposed, a corresponding transposition should be conducted for a part required in a drawing. A wire transposition tool is used to make a transposition S bend of a wire, two layers of a 0.13 mm x 25 mm glass fabric tape are wrapped in a half-lapping manner that are 50 mm longer the S bend at each side, and then the winding is continued after the wire transposition.

[0057] After the winding is completed, the coil (FIG. 8) is got off and delivered to a welding-output terminal-zone for welding a output terminal.

[0058] In some embodiments of the present disclosure, the silicone rubber solution includes liquid polydimethylsiloxane, polymethylhydrosiloxane, a platinum ethylene complex, aluminum oxide, and boron nitride; and a mass ratio of the liquid polydimethylsiloxane, the polymethylhydrosiloxane, the platinum ethylene complex, the aluminum oxide, and the boron nitride is in a range of (22-32): (25-31): (25-35): (5-8): (5-10), and preferably 27: 31: 31: 6: 5 26: 27: 32: 8: 7, or 23: 26: 33: 8: 10.

[0059] In some embodiments of the present disclosure, the silicone rubber solution is prepared by a process as follows: mixing the liquid polydimethylsiloxane, the polymethylhydrosiloxane, the platinum ethylene complex, the aluminum oxide, and the boron nitride. There is no any specific limitation on the process of mixing, and any mixing process well known to those skilled in the art may be used.

[0060] In some embodiments of the present disclosure, before the first vacuum casting, the method further includes: preheating the silicone rubber solution, and the preheating is conducted by a process as follows: placing the silicone rubber solution in an oven at 70°C, preheating for 3 h, then stirred at a temperature of 60°C to 65°C for 1 h to 1.5 h, while vacuuming to 120 Pa to 150 Pa.

[0061] In some embodiments of the present disclosure, the first vacuum casting is conducted with a vacuum degree of 70 Pa to 100 Pa, preferably 80 Pa to 90 Pa, and more preferably 83 Pa to 86 Pa; during the first vacuum casting, a casting tank has a vacuum temperature of 80°C and a mold temperature of 70°C; the first vacuum casting is conducted for 40 min to 60 min, preferably 45 min to 55 min, and more preferably 48 min to 52 min; and after the first vacuum casting is completed, the method further includes: placing a resulting material obtained after the first vacuum casting under a vacuum state for 30 min to 40 min while applying a positive pressure of 0.2 MPa.

[0062] In some embodiments of the present disclosure, the first curing and forming is conducted by a process as follows: heating a resulting material obtained after the first vacuum casting from room temperature to a temperature of 80+5°C and holding at the temperature for 5 h, then heating to a temperature of 110+5°C and holding at the temperature for 4 h, then heating to a temperature of 130+5°C and holding at the temperature for 6 h to 8 h, and cooling. In some embodiments of the present disclosure, the cooling is conducted by turning off a power supply for heating, and not stopping a hot air circulation system until a temperature in the electric oven drops to 80°C.

[0063] In some embodiments of the present disclosure, after the first curing and forming is completed, the method further includes: taking out a silicone rubber cast body, and conducting a mold stripping operation, where the mold stripping is conducted by a process as follows: lifting a cured silicone rubber winding to a work site, and conducting demolding sequentially from outside to inside.

[0064] In some embodiments of the present disclosure, the high-voltage winding after first casting has a Shore hardness of 60 HA to 70 HA.

[0065] In the present disclosure, after obtaining the high-voltage winding after first casting, a fiberglass mesh is wound on inner and outer sides of the high-voltage winding after first casting, a resulting high-voltage winding is subjected to a second vacuum casting using a polyurethane resin solution, and then a second curing and forming is conducted to obtain the high-voltage winding.

[0066] In some embodiments of the present disclosure, the fiberglass mesh is an H-grade fiberglass mesh having a thickness of 4 mm to 6 mm. There is no specific limitation on the winding process, and any winding process well known to those skilled in the art may be used. [0067] In some embodiments of the present disclosure, the second vacuum casting is conducted by a process as follows: installing the high-voltage winding after first casting into a casting mold used for the second vacuum casting. In some embodiments of the present disclosure, the installation process references the process of installing the high-voltage winding before casting into the casting mold used for the first vacuum casting, which is not repeated here.

[0068] In some embodiments of the present disclosure, the polyurethane resin solution includes a polyurethane resin and a curing agent, and a mass ratio of the polyurethane resin to the curing agent is 3: 1. In some embodiments of the present disclosure, the curing agent includes polymethylene polyphenylene isocyanate and diphenylmethane diisocyanate, and a mass ratio of the polymethylene polyphenylene isocyanate to the diphenylmethane diisocyanate is 3: 1, preferably 2.8: 1, and more preferably 2.75: 1.

[0069] In some embodiments of the present disclosure, before the second vacuum casting, the method further includes: preheating the polyurethane resin solution, and the preheating is conducted by a process as follows: placing the polyurethane resin solution in an oven at 70°C, preheating for 3 h, then stirred at a temperature of 60°C to 65°C for 1 h to 1.5 h, while vacuuming to 120 Pa to 150 Pa.

[0070] In some embodiments of the present disclosure, the second vacuum casting is conducted with a vacuum degree of 70 Pa to 100 Pa, preferably 80 Pa to 90 Pa, and more preferably 83 Pa to 86 Pa; during the second vacuum casting, a casting tank has a vacuum temperature of 80°C and a mold temperature of 70°C; the second vacuum casting is conducted for 10 min to 15 min, preferably 11 min to 14 min, and more preferably 12 min to 13 min, and after the second vacuum casting is completed, the method further includes: placing a resulting material obtained after the second vacuum casting under a vacuum state for 5 min while applying a positive pressure of 0.2 M Pa.

[0071] In some embodiments of the present disclosure, the second curing and forming is conducted by a process as follows: heating a resulting material obtained after the second vacuum casting from room temperature to a temperature of 80±5°C and holding at the temperature for 0.5 h, then heating to a temperature of 110±5°C and holding at the temperature for 1 h, then heating to a temperature of 130+5°C and holding at the temperature for 1.5 h, and cooling. In some embodiments of the present disclosure, the cooling is conducted by turning off a power supply for heating, and not stopping a hot air circulation system until a temperature in the electric oven drops to 80°C.

[0072] In some embodiments of the present disclosure, after the second curing and forming is completed, the method further includes: taking out a cast body, and conducting a mold stripping. There is no specific limitation on the processes of taking out the cast body and conducting the mold stripping, and any processes well known to those skilled in the art may be used.

[0073] The present disclosure also provides a high-voltage winding prepared by the method described in the above technical solutions, including a first polyurethane layer as an inner layer, a second polyurethane layer as an outer layer, and a silicone rubber layer filled in a middle (as shown in FIG. 9).

[0074] The present disclosure also provides use of the high-voltage winding described in the above technical solutions in an insulating thy-type transformer.

[0075] In some embodiments of the present disclosure, the insulating dry-type transformer includes the high-voltage winding 9, a low-voltage winding 10, an iron core 11, and a clamp 12 (as shown in FIG. 10).

[0076] In some embodiments of the present disclosure, the insulating thy-type transformer is prepared by a process including the following steps: [0077] Side screws and through-core screws of stacked iron cores are loosened, an upper clamp and a clamp insulator are removed, and upper iron yoke silicon-steel sheets are removed successively and stacked on a general assembly workbench. Pull screws are removed, the side screws and the through-core screws are loosened, and a "U"-shaped clamp is inserted. It should be noted that silicon-steel sheets at each level are carried in staggered positions. Disc screws and through-core screws are loosened, side screws and through-core screws are removed, and an upper clamp insulator is removed. Upper iron yoke silicon-steel sheets are removed successively and stacked on a general assembly workbench.

[0078] Lower cushion blocks and shockproof cushion blocks (the shockproof cushion blocks are stacked on the lower cushion blocks) are placed on a lower clamp. Four cushion blocks are placed under each phase coil at positions with reference to a drawing. A high-voltage coil is lifted by a lifting device, kept perpendicular to the ground, sleeved on an iron core column, and supported by the lower cushion blocks and the shockproof cushion blocks.

[0079] A low-voltage coil is lifted by a lifting device while keeping it perpendicular to the ground and sleeved on an iron core column. The concentricity is adjusted. A distance between the low-voltage coil and the iron core column is fixed with a silicone rubber strip. The high-voltage and low-voltage coils are fixed with cut silicone rubber cushion blocks. The positions and heights of the high-voltage and low-voltage coils and a distance between the high-voltage and low-voltage coils are adjusted. Air gaps between main airways and phases should be uniform as much as possible.

[0080] Iron core sheets are embedded outwards step by step from the main level and leveled for alignment. After the embedding is completed, it is checked whether eyelets of the iron core sheets are aligned. The through-core screws, the clamp insulator, and the upper clamp are installed, and an iron core sheet at each iron yoke level and two ends thereof are leveled by a finishing block. Upper iron yokes are slightly tightened, the side screws are placed, and grounding sheets are inserted at 3rd and 4th iron yoke levels from outside to inside with an insertion length of 50 mm. It is checked whether an iron core column undergoes any arching phenomenon, and if there is any, the arching phenomenon should be handled in time. Upper iron yokes are reorganized to meet the requirements of the drawing. The through-core screws and the side screws are tightened.

[0081] Cushion blocks, shockproof cushion blocks, and press-in nuts are installed. Iron core sheets are embedded outwards step by step from the main level and leveled for alignment After the embedding is completed, the iron core sheets are clamped by a "U"-shaped clamp, and it is checked whether eyelets of the iron core sheets are aligned. The through-core screws, the clamp insulator, and the upper clamp are installed, and an iron core sheet at each iron yoke level and two ends thereof are leveled by a finishing block. After the upper clamp is installed, the positions of upper and lower cushion blocks are adjusted to make the upper and lower cushion blocks at appropriate positions and beautiful. Upper iron yokes are slightly tightened, the side screws are placed, and grounding sheets are inserted at 3rd and 4th iron yoke levels from outside to inside with an insertion length of 50 mm. It is checked whether an iron core column undergoes any arching phenomenon, and if there is any, the arching phenomenon should be handled in time. Upper iron yokes are reorganized to meet the requirements of the drawing. The through-core screws and the side screws are tightened.

[0082] Connecting leads for the high-voltage coil are prepared according to requirements of the drawing. A tapping sheet is fixed on a tapping joint. A "Y" or "D" connecting copper pipe with an appropriate length is prepared, two ends of the "Y" or "D" connecting copper pipe are punched and then tinned, and the remaining part of the "Y" or "D" connecting copper pipe is sleeved with a black heat-shrink pipe. The copper pipe, the corresponding lead terminal, and the connecting lead that allow three phases A, B, and C are in yellow, green, and red, respectively, and tightened. An insulated terminal is placed between a clamp and a lead, and fixed through a bolt.

100831 An insulated terminal is placed between a clamp and an internal lead bar of the low-voltage winding, and fixed through a bolt. A copper bar is placed on a lead bar, and the two are connected and tightened to each other through a bolt. Signs are placed. All bolts are tightened. Tools are organized. A temperature controller and a fan are installed. It is checked whether the wiring is correct. Then the energization is conducted, and it is checked whether the temperature controller and the fan can work normally.

[0084] Grounding sign, tapping position, high-voltage hazard sign, rubber stopper, phase sign, and environmental protection sign or the like are attached, such that the material assembly is completed.

100851 The high-voltage winding and the preparation method and use thereof provided by the present disclosure will be described in detail below with reference to examples, but the examples should not be construed as limiting the claimed scope of the present disclosure.

[0086] Example 1

[0087] A newly-made mold was fully disassembled, and checked whether the appearance and size were qualified. The contact position between an end plate and the mold were tightly fitted to each other. The burrs and iron chips on the mold were cleared using a polisher and sandpaper, and then the mold was thoroughly cleaned with alcohol to remove oil stains and foreign matter on the mold. Then the casting mold was placed in an electric oven, baked at 180+5°C for 3 h, and then taken out of the electric oven, then the release agent was evenly brushed on the casting mold while it was still hot, and then the casting mold was placed in the electric oven once again, baked at 180+5°C for 3 h and wiped with a cotton cloth to remove the release agent.

[0088] The casting inner mold (FIG. 2) used for the first vacuum casting was placed on a pressing plate with a sealing gasket. End rings (FIG. 3) each were sleeved from top to bottom, and the end rings were adjusted to two ends (they remained in a consistent main direction throughout the sleeving process), respectively. The casting inner mold (FIG. 2) was adjusted once to a center position of a lower pressing plate, thereby avoiding the occurrence of a temporary pressing plate. The casting inner mold 1 (FIG. 2) was fixed on the lower pressing plate from inside through 4 pull screws, and a transmission square steel was penetrated. After the casting inner mold was fixed, a winding machine was arranged to be ready for winding (FIG. 6). [0089] Two layers of H-grade fiberglass mesh layers that were at the same height as the coil were wound around the casting inner mold (FIG. 1), and comb-shaped stays were evenly distributed outside in 6 to 8 equal portions (FIG. 7) and fixed on a fiberglass mesh through a glass fabric tape.

[0090] The winding machine was started to begin winding. The high-voltage winding adopted a disc structure and a continuous coil (FIG. 8). A root of each wire disc was separated from upper and lower wire discs through a NOMEX paper channel, wrapped with an NOMEX paper tape, and tied with a 0.12 X 25 mm fiberglass tape. A wire transition from the previous wire disc to the next wire disc was wrapped with two NOMEX paper layers in a half-lapping manner. After a wire turn is bent, it was wrapped with two layers of H-grade fiberglass mesh that are at the same height as the coil.

[0091] If airway plates were arranged between coil layers, POM airway plates as specified in a drawing were sleeved with a glass fabric sleeve, tied tightly at two ends with a glass fabric tapes, and then arranged side by side next to a comb-shaped stay (FIG. 7) at a specified layer to form a circle, and lower ends of the airway plates each were inserted into a locating slot. After the airway plates were arranged, outer diameters of the airway plates were measured, and wire turns outside the airway plates were continuously wound. When a coil wound with a plurality of wires in parallel needed to be transposed, a corresponding transposition should be conducted for a part required in a drawing. A wire transposition tool was used to make a transposition S bend of a wire, two layers of a 0.13 mm x 25 mm glass fabric tape were wrapped in a half-lapping manner that were 50 mm longer the S bend at each side, and then the winding was continued after the wire transposition.

[0092] After the winding was completed, the coil (FIG. 8) was got off and delivered to a welding-output terminal-zone for welding a output terminal.

[0093] Foreign matter on surfaces (an outer membrane and a wiring board) of the high-voltage winding before casting were cleared. A release agent was evenly applied on surfaces of the casting outer mold and the panel, and then the surfaces of the applied casting outer mold and the panel were wiped cleanly with a cotton cloth. A sealing rubber strip was pressed into each of sealing grooves at two sides of the panel 3, and two ends of the sealing rubber strip were trimmed. The wiring board was installed on the casting outer mold 4. A process screw on each tapping nut was penetrated into a corresponding position on the wiring board, adjusted the screw to a center position of a hole, and tightened through a screw cap to make the tapping nut firmly connected to the wiring board. A protrusion of the end ring 2 (FIG. 3) was adjusted to align with the panel 3 (FIG. 4), and checked whether a height of a cast was consistent with a corresponding height specified in a drawing. Foreign matter on a coil were cleared by a dust collector. The casting outer mold 4 (FIG. 5) was sleeved and tightened with a tightener. A pressing strip was arranged at a position in contact with the wiring board. The casting outer mold 4 (FIG. 5) was tightly clamped with the panel (FIG. 4) through a "U"-shaped clamp to make the two fit tightly (FIG. 1).

[0094] Li quid polydim ethyl silox an e, polym ethyl hydrosiloxane, a platinum ethylene complex, aluminum oxide, and boron nitride were mixed in a mass ratio of 27: 31: 31: 6: 5. Then a resulting mixture was placed in an oven at 70°C, preheated for 3 h, then stirred at 65°C for 1 h, while vacuuming to 130 Pa, subjected to a first vacuum casting (with a vacuum degree of 85 Pa, a casting tank vacuum temperature of 80°C, a mold temperature of 70°C, and a casting time of 50 min, during the first vacuum casting), then placed under vacuum for 35 min while applying a positive pressure of 0.2 MI3a, and then taken out.

[0095] A winding obtained after the first vacuum casting was transferred into an electric oven, and a temperature in the electric oven was gradually increased to conduct a first curing and forming (The temperature was raised from room temperature to a first temperature of 80+5°C, the first temperature was held for 5 h, the first temperature was raised to a second temperature of 110+5°C, the second temperature was held for 4 h, the second temperature was raised to a third temperature of 130±5°C, and the third temperature was held for 7 h. Then a power supply for heating was turned off and a hot air circulation system was not turned off until a temperature in the electric oven dropped to 80°C). After the first curing and forming was completed, a cured silicone rubber winding was taken out and subjected to a mold stripping operation as follows: the cured silicone rubber winding was lifted to a work site, and demolding was conducted sequentially from outside to inside to obtain a high-voltage winding after first casting (with a Shore hardness of 65 HA).

[0096] An H-grade fiberglass mesh with a thickness of 5 mm was wound inside and outside the high-voltage winding after first casting, and an inner mold, an outer mold, an end ring, and a panel for a second vacuum casting were re-assembled. A polyurethane resin and a curing agent were mixed in a mass ratio of 3: 1 (the curing agent included polymethylene polyphenylene isocyanate and diphenylmethane diisocyanate in a mass ratio of 2: 1), then a resulting mixture was placed in an oven at 70°C, preheated for 3 h, then stirred at 65°C for 1 h, while vacuuming to 135 Pa, conducted to the second vacuum casting (with a vacuum degreeof 135 Pa, a casting tank vacuum temperature of 80°C, a mold temperature of 70°C, and a casting time of 13 min during the second vacuum casting), then placed under vacuum for 5 min while applying a positive pressure of 0.2 MiPa, and then taken out.

[0097] A winding obtained after the second vacuum casting was transferred into an electric oven, and a temperature in the electric oven was gradually increased to conduct a second curing and forming (The temperature was raised from room temperature to a first temperature of 80±5°C, the first temperature was held for 0.5 h, the first temperature was raised to a second temperature of 110+5°C, the second temperature was held for 1 h, the second temperature was raised to a third temperature of 130+5°C, and the third temperature was held for 1.5 h. Then a power supply for heating was turned off and a hot air circulation system was not turned off until a temperature in the electric oven dropped to 80°C). After the second curing and forming was completed, a resulting material was taken out and subjected to a mold stripping operation to obtain a high-voltage winding.

100981 Side screws and through-core screws of stacked iron cores were loosened, an upper clamp and a clamp insulator were removed, and upper iron yoke silicon-steel sheets were removed successively and stacked on a general assembly workbench. Pull screws were removed, the side screws and the through-core screws were loosened, and a "U"-shaped clamp was inserted. It should be noted noted that silicon-steel sheets at each level were carried in staggered positions. Disc screws and the through-core screws were loosened, the side screws and the through-core screws were removed, and an upper clamp insulator was removed. Upper iron yoke silicon-steel sheets were removed successively and stacked on a general assembly workbench. 100991 Lower cushion blocks and shockproof cushion blocks (the shockproof cushion blocks are stacked on the lower cushion blocks) were placed on a lower clamp. Four cushion blocks were placed under each phase coil at positions with reference to a drawing. A high-voltage coil was lifted by a lifting device, kept perpendicular to the ground, sleeved on an iron core column, and supported by the lower cushion blocks and the shockproof cushion blocks.

101001 A low-voltage coil was lifted by a lifting device, while kepeping it perpendicular to the ground and sleeved on an iron core column. The concentricity was adjusted. A distance between the low-voltage coil and the iron core column was fixed with a silicone rubber strip. The high-voltage and low-voltage coils were fixed with cut silicone rubber cushion blocks. The positions and heights of the high-voltage and low-voltage coils and a distance between the high-voltage and low-voltage coils were adjusted. Air gaps between main airways and phases should be uniform as much as possible.

101011 Iron core sheets were embedded outwards step by step from the main level and leveled for alignment After the embedding was completed, it was checked whether eyelets of the iron core sheets were aligned. The through-core screws, the clamp insulator, and the upper clamp were installed, and an iron core sheet at each iron yoke level and two ends thereof were leveled by a finishing block. Upper iron yokes were slightly tightened, the side screws were placed, and grounding sheets were inserted at 3rd and 4th iron yoke levels from outside to inside with an insertion length of 50 mm. It was checked whether an iron core column underwent any arching phenomenon, and if there was any, the arching phenomenon should be handled in time. Upper iron yokes were reorganized to meet the requirements of the drawing. The through-core screws and the side screws were tightened.

[01021 Cushion blocks, shockproof cushion blocks, and press-in nuts were installed. Iron core sheets were embedded outwards step by step from the main level and leveled for alignment. After the embedding was completed, the iron core sheets were clamped by a "U"-shaped clamp, and it was checked whether eyelets of the iron core sheets were aligned. The through-core screws, the clamp insulator, and the upper clamp were installed, and an iron core sheet at each iron yoke level and two ends thereof were leveled by a finishing block. After the upper clamp was installed, the positions of upper and lower cushion blocks were adjusted to make the upper and lower cushion blocks at appropriate positions and beautiful. Upper iron yokes were slightly tightened, the side screws were placed, and grounding sheets were inserted at 3rd and 4th iron yoke levels from outside to inside with an insertion length of 50 mm. It was checked whether an iron core column underwent any arching phenomenon, and if there was any, the arching phenomenon should be handled in time. Upper iron yokes were reorganized to meet the requirements of the drawing. The through-core screws and the side screws were tightened.

[0103] Connecting leads for the high-voltage coil were prepared according to requirements of the drawing. A tapping sheet was fixed on a tapping joint. A "Y" or "D" connecting copper pipe with an appropriate length was prepared, two ends of the "Y" or "D" connecting copper pipe were punched and then tinned, and the remaining part of the "Y" or "D" connecting copper pipe was sleeved with a black heat-shrink pipe. The copper pipe, the corresponding lead terminal, and the connecting lead that allowed three phases A, B, and C were in yellow, green, and red, respectively, and tightened. An insulated terminal was placed between a clamp and a lead, and fixed through a bolt.

[01041 An insulated terminal was placed between a clamp and an internal lead bar of the low-voltage winding, and fixed through a bolt. A copper bar was placed on a lead bar, and the two were connected and fastened to each other through a bolt. Signs were placed. All bolts were tightened. Tools were organized. A temperature controller and a fan were installed. It was checked whether the wiring was correct. Then the energization was conducted, and it was checked whether the temperature controller and the fan could work normally.

[0105] Grounding sign, tapping position, high-voltage hazard sign, rubber stopper, phase sign, and environmental protection sign or the like were attached, such that the material assembly was completed to obtain an insulating dry-type transformer.

[0106] Although the present disclosure has been described in detail through the above embodiments, the embodiments are merely some rather than all of the embodiments of the present disclosure. All other embodiments obtained by a person based on these embodiments without creative efforts shall fall within the scope of the present disclosure.

Claims (16)

1. WHAT IS CLAIMED IS: 1. A method for preparing a high-voltage winding, comprising: subjecting a high-voltage winding before casting to a first vacuum casting using a silicone rubber solution, and then conducting a first curing and forming to obtain a high-voltage winding after first casting; and winding a fiberglass mesh on inner and outer sides of the high-voltage winding after first casting, subjecting a resulting high-voltage winding to a second vacuum casting using a polyurethane resin solution, and then conducting a second curing and forming to obtain the high-voltage winding.
2. 2. The method of claim 1, wherein the silicone rubber solution comprises liquid polydimethylsiloxane, polymethylhydrosiloxane, a platinum ethylene complex, aluminum oxide, and boron nitride in a mass ratio of (22-32): (25-31): (25-35): (5-8): (5-10).
3. 3. The method of claim 1 or 2, wherein the first vacuum casting is conducted with a vacuum degree of 70 Pa to 100 Pa for 40 min to 60 min, and during the first vacuum casting, a casting tank has a vacuum temperature of 80°C and a mold temperature of 70°C; and after the first vacuum casting is completed, the method further comprises: placing a resulting material under a vacuum state for 30 min to 40 min while applying a positive pressure of 0.2 MPa.
4. 4. The method of claim 1, wherein the first curing and forming is conducted by heating a resulting material obtained after the first vacuum casting from room temperature to a temperature of 80+5°C and holding at the temperature for 5 h, then heating to a temperature of 110+5°C and holding at the temperature for 4 h, then heating to atemperature of 130+5°C and holding at the temperature for 6 h to 8 h, and cooling.
5. 5. The method of claim I, wherein the polyurethane resin solution comprises a polyurethane resin and a curing agent; and a mass ratio of the polyurethane resin to the curing agent is 3: 1.
6. 6. The method of claim 1, wherein the second vacuum casting is conducted with a vacuum degree of 70 Pa to 100 Pa for 10 min to 15 min, and during the second vacuum casting, a casting tank has a vacuum temperature of 80°C and a mold temperature of 70°C; and after the second vacuum casting is completed, the method further comprises: placing a resulting material under a vacuum state for 5 min while applying a positive pressure of 0.2 MPa.
7. 7. The method of claim 1 or 5, wherein the second curing and forming is conducted by heating a resulting material obtained after the second vacuum casting from room temperature to a temperature of 80+5°C and holding at the temperature for 0.5 h, then heating to a temperature of 110+5°C and holding at the temperature for 1 h, then heating to a temperature of 130+5°C and holding at thetemperature for 1.5 h, and cooling.
8. 8. The method of claim 1, wherein casting molds used for the first vacuum casting and the second vacuum casting each independently comprise a casting inner mold (1), an end ring (2), a panel (3), and a casting outer mold (4); an outer diameter of a casting inner mold used for the second vacuum casting is 5 mm smaller than an inner diameter of a casting inner mold used for the first vacuum casting; an outer diameter of an end ring used for the second vacuum casting is 5 mm larger than an outer diameter of an end ring used for the first vacuum casting, and an inner diameter of the end ring used for the second vacuum casting is 5 mm smaller than an inner diameter of the end ring used for the first vacuum casting; a width of a panel used for the second vacuum casting is 20 mm larger than a width of a panel used for the first vacuum casting; and an outer diameter of a casting outer mold used for the second vacuum casting is 5 mm larger than an outer diameter of a casting outer mold used for the first vacuum casting.
9. 9. The method of claim 1, wherein before the first vacuum casting, the method further comprises: preheating the silicone rubber solution, and the preheating is conducted by placing the silicone rubber solution in an oven at 70°C, preheating for 3 h, then stirring at a temperature of 60°C to 65°C for 1 h to 1.5 h, while vacuuming to 120 Pa to 150 Pa.
10. 10. The method of claim 1 or 2, wherein the high-voltage winding after first casting has a Shore hardness of 60 HA to 70 HA.
11. 11. The method of claim 1, wherein the fiberglass mesh is an H-grade fiberglass mesh having a thickness of 4 mm to 6 mm
12. 12. The method of claim 5, wherein the curing agent comprises polymethylene polyphenylene isocyanate and diphenylmethane diisocyanate; and a mass ratio of the polymethylene polyphenylene isocyanate to the diphenylmethane diisocyanate is 3: 1.
13. 13. The method of claim 1, wherein before the second vacuum casting, the method further comprises: preheating the polyurethane resin solution, and the preheating is conducted by placing the polyurethane resin solution in an oven at 70°C, preheating for 3 h, then stirring at a temperature of 60°C to 65°C for 1 h to 1.5 h, while vacuuming to 120 Pa to 150 Pa.
14. 14. A high-voltage winding prepared by the method of any one of claims 1 to 13, comprising a first polyurethane layer as an inner layer, a second polyurethane layer as an outer layer, and a silicone rubber layer filled in a middle.
15. 15. Use of the high-voltage winding of claim 14 in an insulating dry-type transformer.
16. 16. The use of claim 15, wherein the insulating dry-type transformer comprises the high-voltage winding (9), a low-voltage winding (10), an iron core (11), and a clamp (12).