WO2022267986A1 - Method for preparing three-layer gradient gis/gil support insulator - Google Patents

Abstract

Provided is a method for preparing a three-layer gradient GIS/GIL support insulator. The method comprises: taking the reduction of the electric field strength of an insulator along a surface or in a local region as an optimization target, and solving an optimal spatial distribution of a dielectric constant inside a support insulator by using a variable density algorithm; according to an optimization result, dividing a region, in which the dielectric constant changes, into a dielectric constant transition region and a high dielectric region, extracting a combined contour of the dielectric constant transition region, and subsequently generating, by means of photo-curing 3D printing, a hollow dielectric constant transition region that has a support and a resin pouring gate; preparing a thermo-curable high dielectric composite material by means of high dielectric filler/polymer blending, subsequently pouring the high dielectric composite material into the dielectric constant transition region, and integrally placing the dielectric constant transition region into a metal mold for fixation; and preparing a thermo-curable high dielectric composite material by means of low dielectric filler/polymer blending, subsequently pouring the material into the metal mold, and completing curing in vacuum, such that a three-layer gradient GIS/GIL support insulator can be obtained.

Description

Preparation method of a three-layer gradient GIS/GIL support insulator

This application claims the priority of the Chinese patent application with the application number 202110701103.0 and the title of the invention "a method for preparing a three-layer gradient GIS/GIL support insulator" submitted to the China Patent Office on June 23, 2021, the entire content of which is passed References are incorporated in this application.

technical field

The invention belongs to the technical field of high-voltage power equipment manufacturing, and in particular relates to a preparation method of a three-layer gradient GIS/GIL support insulator.

Background technique

Gas Insulated Switchgear (GIS) is widely used in EHV and UHV substations due to its small footprint and stable operating environment. Gas Insulated Transmission Line (GIL), as a new type of advanced transmission method, has the advantages of large transmission capacity, small transmission loss, and high safety. It is often used as an alternative to overhead lines and is used in special transmission environments. middle.

In GIS/GIL power equipment, the supporting insulator plays the role of supporting the metal guide rod, isolating the potential, and sealing the gas chamber. However, when its structural design is unreasonable or there are defects such as bubbles and metal particles on the surface, the excellent insulation performance of SF6 gas in a uniform and slightly uneven electric field will rapidly deteriorate due to the distortion of the local electric field, and flashover along the surface will be induced. The traditional method to improve the electric field distribution is mainly the optimal design of the insulator/metal electrode structure. For example, install a metal shield on the high-voltage side to optimize the electric field at the head of the pot; design a reasonable insulator center insert structure; set an "R" arc metal shield on the tank flange and insulate the metal shield inner ring to reduce the pot root electric field. However, the above-mentioned method increases the complexity of the structure, increases the difficulty of manufacture, and often causes epiphytic problems. For example, in the tank manufacturing process of existing GIS equipment, "R" arc metal shielding is often installed at the grounding flange. Due to the special shape design, manual grinding is often required after welding, which is time-consuming and laborious, and improper grinding is easy to form metal tip, causing partial discharges. The existence of the metal shielding inner ring can homogenize the electric field at the flange to a certain extent, but on the one hand, the optimization effect is limited; on the other hand, it is easy to cause cracks in the insulator and deteriorate the mechanical properties of the basin. In recent years, the method of actively regulating the electric field distribution by optimizing the dielectric distribution of materials has gradually become a research hotspot in the field of design and manufacture of insulating structures. A large number of numerical simulation results show that the gradient distribution of dielectric parameters can be constructed by numerical simulation methods such as stack optimization and topology optimization, which can greatly reduce the maximum electric field of the insulation system and homogenize the electric field distribution along the surface. The improvement of electric field distribution based on the adjustment of material properties breaks through the limitations of previous shape optimization design, and provides a new idea for solving the miniaturization of high-voltage GIS.

However, the current gradient insulators lack effective rapid manufacturing solutions, and the lamination and centrifugation methods have poor controllability, and the size of the molding is limited. Using 3D printing technology can avoid the above problems to a certain extent, but the insulator can only be completed by 3D printing. The manufacturing processing time is long, and the mechanical/thermal properties such as the thermal expansion coefficient of the material are difficult to match with traditional vacuum casting epoxy resins.

Contents of the invention

The technical problem to be solved in this application is to provide a method for preparing a three-layer gradient GIS/GIL support insulator to improve the insulator preparation efficiency and electric field control effect.

This application adopts the following technical solutions:

A preparation method of a three-layer gradient GIS/GIL support insulator, comprising the following steps:

Divide the supporting insulator into photo-cured dielectric transition region, heat-cured high-dielectric region, and heat-cured low-dielectric region; discretize the insulator, determine the constraints, and find the optimal spatial distribution of the internal dielectric constant of the supporting insulator, according to the optimal The spatial distribution results divide the dielectric constant transition area and the high dielectric area, generate a hollow three-dimensional model, and generate a hollow photo-curing dielectric transition area with supports and resin pouring ports through photo-curing 3D printing; The heat-cured epoxy resin composite slurry mixed with high dielectric filler is poured into the light-cured dielectric transition area, and then the light-cured dielectric transition area is placed in a metal mold to fix; The heat-cured epoxy resin composite slurry of the electric filler is poured into a metal mold to form a heat-cured low-dielectric region; finally, a three-layer gradient GIS/GIL support insulator is obtained through vacuum heat curing.

Specifically, the preparation of the light-cured dielectric transition region is as follows:

S101. To reduce the electric field at the metal/epoxy resin interface of the insulator, the electric field along the surface of the insulator, or the electric field intensity in the area at the three joints on the flange side as the optimization goal, the insulator is discretized, and the dielectric constant in each micro unit is equal to the dielectric constant of the substrate. Change within the range from the constant value to the upper limit of the change of the dielectric constant, obtain the optimization target f through the topology optimization method, and determine the constraint conditions;

S102. According to the optimization target f calculated in step S101, the region with a dielectric constant value of 8 to 12 is set as a dielectric constant transition region, and the region with a dielectric constant value of 14 to 20 is set as a high dielectric region ; Extract the surface contour according to the geometry of the dielectric constant transition area, generate a hollow three-dimensional model, and set mechanical support points outside the three-dimensional model;

S103. Prepare high dielectric composite slurry by blending high dielectric filler/photosensitive resin;

S104. Pour the high-dielectric composite slurry prepared in step S103 into a light-curing 3D printer, and form by layer-by-layer curing to complete the manufacture of a hollow dielectric transition area, and then put the part into a post-curing box for curing. treatment to obtain photocured dielectric transition regions.

Further, in step S101, the optimization target f is as follows:

Among them, Ω ₁ is the dielectric constant design area, Ω ₂ is the optimization target area 1, and Ω ₃ is the optimization target area 2; C _ref is the normalization parameter of the optimization component in the electric field integral item; A, h _mesh and ρ are respectively The area of the design area Ω ₁ , the maximum size of grid division, and the density of artificial materials in the grid; q is the weight coefficient, r is the abscissa in the two-dimensional axisymmetric coordinate system, and z is the abscissa in the two-dimensional axisymmetric coordinate system ordinate, E is the electric field strength in the optimization target area Ω ₂ , Ω is the integral calculation area;

The constraints are:

Among them, ε _ri , ε _max and ε _min are the permittivity, the upper limit of permittivity change and the lower limit of permittivity in the i-th mesh, respectively, m is the density function shape control coefficient, ρ _i is the i-th mesh The material density in the grid; U _p is the upper limit of the ratio of the area of the high dielectric region to the total area.

Further, in step S103, the viscosity of the high-dielectric composite slurry at 25°C is lower than 5000mP·s, and the thickness is greater than 0.2mm under 405nm ultraviolet light irradiation; the dielectric constant after complete curing is 8-12 , the coefficient of linear thermal expansion is 30～50×10 ^-6 /K.

Further, in step S104, the layer thickness of the printer is 0.05 mm or 0.1 mm, the power of the ultraviolet light source is 45-100 mW/cm ² , and the curing is carried out at 40-60°C and 60-80 mW/cm ² for 2-4 hours .

Specifically, the preparation of the heat-cured high dielectric region is as follows:

S201, compounding the thermosetting epoxy resin and the high dielectric filler, and configuring the high dielectric composite slurry;

S202. Pour the high dielectric composite slurry prepared in step S201 into the light-cured dielectric transition region obtained in step S1, and then put it into the metal mold used for casting the supporting insulator to prepare the heat-cured high dielectric region.

Further, in step S201, the cured composite slurry has a dielectric constant of 18-20, and a linear thermal expansion coefficient of 30-50×10 ^-6 /K at 25°C.

Specifically, the preparation of the heat-cured low-dielectric region is as follows:

S301, compounding heat-cured epoxy resin and low-dielectric filler, and configuring high-dielectric composite slurry;

S302. Pour the low-dielectric composite slurry obtained in step S301 into the metal mold in step S2, and then use an epoxy resin casting scheme to complete the molding of the three-layer gradient support insulator.

Further, in step S301, the cured composite slurry has a dielectric constant of 5-5.8, and a linear thermal expansion coefficient of 30-50×10 ^-6 /K at 25°C.

Further, in step S302, the pouring epoxy resin and alumina or silica powder are blended for 1 to 2 hours at 110-120°C and a vacuum of 1-2mbar, and then a curing agent is added, and the The temperature is 1~2mbar, the temperature is 80~100°C, keep it for 6~8 hours, then raise the temperature to 110~120°C and keep it for 2~4 hours, then take out the insulator to complete demoulding, and finally raise the temperature to 120~130°C and keep it for 12~ After 16 hours, a three-layer gradient support insulator was obtained after natural cooling to room temperature.

Compared with the prior art, the present application has at least the following beneficial effects:

This application is a preparation method of a three-layer gradient GIS/GIL support insulator. Under the condition that the main material of the insulator remains unchanged, a three-layer gradient is formed inside the insulator to control the electric field distribution along the surface and the flange side of the insulator, which can ensure the insulator. While improving the mechanical strength, the electric field distribution is significantly improved, thereby improving the electric strength along the surface of the insulator and the ability to suppress partial discharge. The three-layer gradient structure includes a high dielectric region, a transition region, and a low dielectric region. The existence of the transition region can eliminate the macro interface of high and low dielectric constants to a certain extent, and achieve a smooth transition of the dielectric properties of the material while maintaining the thermal expansion coefficient. and other thermodynamic parameters are matched to each other, so that the supporting insulator can run for a long time in the working environment; by adjusting the parameters of the topology optimization algorithm, the optimal dielectric constant distribution with clear boundary outline and easy to manufacture can be generated, and the insulator can be significantly improved from the simulation results. The distribution of the electric field along the surface or the reduction of local concentrated electric stress, the algorithm itself is flexible and changeable, and can be applied to the optimal design of various types of insulating structures.

Further, photo-curing 3D is used to print the dielectric transition region. On the one hand, photo-curing 3D printing itself has high molding accuracy and defect suppression ability, which is very suitable for the manufacture of complex insulating structures. On the other hand, the dielectric constant in the dielectric constant transition region only needs to reach 8-12 to meet the requirements. In this way, the filler content in the photosensitive composite material is low, and the cured thickness can be significantly improved compared with the high filling amount. At the same time, the viscosity of the composite material can be reduced, which greatly improves the success rate of 3D printing. In addition to the material dielectric constant transition, the other two functions of the dielectric transition area are as the mold in the high dielectric area and the internal support of the metal mold. Using photo-curing 3D printing to integrate the dielectric constant transition region and the support structure, which reduces the defects of the material interface and makes the design more flexible. Compared with the solid structure, the printing efficiency of the 3D printed dielectric structure can be greatly improved. Due to the design of the hollow structure, the ultraviolet light source can effectively penetrate the entire part during the post-curing process, ensuring that the material inside the part can also be completely post-cured.

Further, for the specific structure, first determine the position where the electric field distortion occurs, that is, the electric field at the metal/epoxy resin interface of the insulator, the electric field along the surface of the insulator, or the area at the three-junction point on the flange side, and then aim at reducing the electric field at this position, using topological The optimization algorithm finds out the optimal spatial distribution of gradient dielectric parameters inside the insulator. The topology optimization algorithm adopted takes the dielectric parameters in each small area after the discretization of insulators as the optimization target. Compared with the traditional structure optimization or parameter optimization methods, it can find the optimal solution in a larger optimization feasible area, thereby greatly reducing the optimization target. Refers to the phenomenon of local electric field distortion.

Furthermore, in order to realize the photocurable 3D printing preparation of the dielectric constant transition region, it is necessary to first configure the photocurable 3D printing slurry whose material parameters such as dielectric constant meet the optimization requirements. On the one hand, the blending method of high dielectric filler and photosensitive resin can significantly increase the dielectric constant of the composite material to meet the material requirements for the design. On the other hand, the composite process method is mature and easy to operate, which can be used in the actual production process. mass production.

Furthermore, in the process of photocuring 3D printing of composite paste, the thickness of the printing layer and the energy of photocuring are crucial to the success rate of printing the part and the surface quality of the part. Here, the layer thickness is set to 0.05 or 0.1mm. On the one hand, it can meet the requirements of the surface quality of the part. On the other hand, this parameter is also a common parameter setting of existing commercial printers. It is difficult to realize and can ensure the success rate of printing the part. The energy of the light source is set within the range of 45-100mW/ ^cm2 . Within this energy range, on the one hand, the light intensity range is sufficient to penetrate the composite slurry with high absorbance, and the corresponding thickness can be realized after the setting of the curing layer thickness is completed. Turn into a solid state, thereby ensuring molding. On the other hand, under too high energy irradiation, the inside of the slurry is prone to damage due to heat absorption, resulting in denaturation of the resin, thereby reducing the success rate of printing. There are still incompletely cured organic polymers inside the part after photocuring printing. The purpose of post-curing is to improve the crosslinking degree of the part, thereby improving the mechanical, thermal and electrical properties of the printed part. Curing at 40-60°C and 60-80mW/ ^cm2 for 2-4 hours. In this temperature range, the uncured groups have high chemical activity and can polymerize with surrounding molecules under light conditions, while The light source energy of 60-80mW/cm ² can ensure that the penetration depth is enough to cure the part on the one hand, and on the other hand, it will not cause additional damage to the part.

Furthermore, after the vacuum pouring of the three-layer gradient support insulator is completed, the dielectric constant transition area is used as a mold for the high dielectric area. One part does not need to be taken out, so that one-time molding can be realized. The high dielectric area is made of ceramic filler mixed with heat-cured epoxy resin and then vacuum cast. Except for the difference in dielectric constant, other material properties such as linear expansion coefficient have no difference. Therefore, there will be no problems such as interfacial cracking or mismatching of thermal parameters, thereby significantly improving interfacial compatibility.

Further, the dielectric constant value of the composite slurry after curing is 18-20. From the perspective of composite material realization, this parameter can be easily realized by increasing the filler content, etc. From the perspective of electric field optimization, the optimal result can be achieved when the upper limit of the dielectric constant is 18-20.

Furthermore, the low-dielectric area is made of ceramic filler mixed with heat-cured epoxy resin and then vacuum-cast. Except for the difference in dielectric constant, there is no difference in other material properties such as linear expansion coefficient, so there will be no interface cracking or thermal Problems such as parameter mismatch, thus significantly improving interface compatibility.

Furthermore, the dielectric constant of the composite slurry after curing is 5-5.8, and the linear thermal expansion coefficient at 25°C is 30-50×10 ^-6 /K, which is the dielectric constant of insulator materials actually used in current projects. The range of the constant can be conveniently realized without changing the existing production process, thereby ensuring the engineering application reliability of the prepared insulator.

Further, the epoxy resin is blended with alumina or silica powder at 110-120°C and a vacuum of 1-2mbar for 1-2 hours. In this temperature range, the viscosity of the composite material is significantly reduced. Blending for 1 to 2 hours can ensure that the filler is uniformly dispersed in the resin matrix, and stirring in a low vacuum environment can make the gas adsorbed in the composite material escape, and avoid bubble defects inside the part. After adding curing agent and mixing it into the mold, it can avoid increasing the resin gel caused by adding curing agent. The resin crosslinking reaction is mild at 110-120°C, and the resin hardening and molding can be completed in 2-4 hours, and then the insulator is taken out to complete. Release the mold, and finally raise the temperature to 120-130°C (whether it is lower than 130 or 130, it is recommended to give a range value) and keep it for 12-16 hours. Under this post-curing condition, on the one hand, the uncured group has high activity and can re-participate The crosslinking reaction improves the performance of the part. On the other hand, the long-term heat preservation process helps to release the mechanical stress existing in the internal reaction, ensuring the mechanical performance of the insulator under full load conditions.

In summary, this application proposes an efficient and reliable preparation method for three-layer gradient GIS/GIL support insulators. The dielectric constant transition area is prepared by topological optimization of the internal dielectric constant of the material combined with photocuring 3D printing, and then the high dielectric area and the low dielectric area are formed inside and outside the transition area by thermal curing vacuum casting to complete the three-layer gradient Manufacture of support insulators. The prepared insulator has good mechanical properties and interface strength under the condition of ensuring a good electric field along the surface and the electric field in the three-junction area on the flange side. At the same time, the thermal expansion coefficient of the materials in the three areas remains unchanged, and there will be no interface cracking Or thermal parameters mismatch and other problems, thus significantly improving the stability and reliability of the insulator under long-term operating conditions.

The technical solutions of the present application will be described in further detail below with reference to the drawings and embodiments.

Description of drawings

Figure 1 is a flowchart according to one or more embodiments;

Figure 2 is an example of the implementation of the present invention, wherein (a) is the high dielectric region structure of the 110kV support insulator obtained by taking the surface electric field as the optimization target, and (b) is the dielectric transition region of the 110kV support insulator obtained by taking the surface electric field as the optimization target structure, (c) is the high dielectric area structure of the 110kV support insulator based on the optimization target of the electric field in the air gap on the flange side, (d) is the dielectric structure of the 110kV support insulator based on the optimization target of the electric field in the air gap on the flange side Electric transition area structure, (e) is the 550kV supporting insulator high dielectric area structure obtained by optimizing the electric field in the air gap on the flange side, (f) is the 550kV obtained by taking the electric field in the air gap on the flange side as the optimization target The structure of the dielectric transition region of the supporting insulator, (g) is the high dielectric region structure of the 252kV post insulator obtained by taking the electric field of the inner central axis of the insulation as the optimization goal, (h) is the 252kV post insulator obtained by taking the electric field of the inner central axis of the insulation as the optimization goal Dielectric transition region structure.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

It should be understood that when used in this specification and the appended claims, the terms "comprising" and "comprises" indicate the presence of described features, integers, steps, operations, elements and/or components, but do not exclude one or Presence or addition of multiple other features, integers, steps, operations, elements, components and/or collections thereof.

It should also be understood that the terminology used in the description of the present invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used in this specification and the appended claims, the singular forms "a", "an" and "the" are intended to include plural referents unless the context clearly dictates otherwise.

It should also be further understood that the term "and/or" used in the description of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations .

Various structural schematic diagrams according to the disclosed embodiments of the present invention are shown in the accompanying drawings. The figures are not drawn to scale, with certain details exaggerated and possibly omitted for clarity of presentation. The shapes of various regions and layers shown in the figure and their relative sizes and positional relationships are only exemplary, and may deviate due to manufacturing tolerances or technical limitations in practice, and those skilled in the art may Regions/layers with different shapes, sizes, and relative positions can be additionally designed as needed.

The invention provides a preparation method of a three-layer gradient GIS/GIL support insulator, which divides the insulator into three parts: a light-cured dielectric transition region, a heat-cured high-dielectric region, and a heat-cured low-dielectric region. Firstly, the dielectric transition region is prepared by light-curing 3D printing technology. Specifically, the topology optimization theory is used to reduce the electric field intensity along the surface of the insulator or in the local area as the optimization goal, and the optimal spatial distribution of the internal dielectric constant of the supporting insulator is solved by using the variable density algorithm. ;According to the optimization results, the area where the dielectric constant changes is divided into a dielectric constant transition area and a high dielectric area, and the combination profile of the dielectric constant transition area is extracted, and then photo-cured 3D printing is used to generate a support and resin Hollow dielectric constant transition area at the sprue; heat-curable high dielectric composite material is prepared by high dielectric filler/polymer blending method, and then the high dielectric composite material is poured into the dielectric constant transition area and placed as a whole Put it into a metal mold to fix it; use the low dielectric filler/polymer blending method to prepare a heat-curable high-dielectric composite material, and then pour it into a metal mold. After heat curing in vacuum, a three-layer gradient GIS/ GIL support insulators.

Please refer to Fig. 1, a preparation method of a three-layer gradient GIS/GIL support insulator according to the present invention. The support insulator is divided into three parts: a light-cured dielectric transition region, a heat-cured high-dielectric region, and a heat-cured low-dielectric region; The specific steps are as follows:

S1. Light-cured dielectric transition area: The light-cured dielectric transition area is made of light-cured 3D printing photosensitive composite materials. The main functions include insulating internal gradient dielectric constant transition, metal mold internal support and fixation, and serving as a heat-cured high dielectric area. Mold, its manufacturing steps are:

S101. With the optimization goal of reducing the electric field along the surface of the insulator and the electric field intensity at the three joint points on the flange side, the insulator is discretized, and the dielectric constant in each tiny unit can be determined by the dielectric constant value of the matrix (here selected as 5.8 ) to the upper limit of the dielectric constant change (here selected as 20), through the topology optimization algorithm, to find the optimal spatial distribution of the internal dielectric constant of the supporting insulator;

The design variable is the dielectric constant in each tiny unit after discretization, as follows:

ε(r,z),(r,z)∈Ω ₁

The dielectric constant of each point after the internal discretization of the insulator is recorded as ε(r,z),(r,z)∈Ω ₁ , and the optimization objective f is obtained as follows:

Among them, Ω ₁ is the dielectric constant design area, Ω ₂ is the optimization target area 1, and Ω ₃ is the optimization target area 2; C _ref is the normalization parameter of the optimization component in the electric field integral item; A, h _mesh and ρ are respectively The area of the design area Ω ₁ , the maximum size of grid division, and the density of artificial materials in the grid; q is the weight coefficient, r is the abscissa in the two-dimensional axisymmetric coordinate system, and z is the abscissa in the two-dimensional axisymmetric coordinate system The ordinate of , E is the electric field strength in the optimized target area Ω ₂ , and Ω is the integral calculation area.

The constraints are:

Among them, ε _ri , ε _max and ε _min are the permittivity, the upper limit of permittivity change (set to 20) and the lower limit of permittivity (set to 5.8) in the i-th grid, respectively, and m is the density function shape Control coefficient, ρi is the material density in the _i -th grid. U _p is the upper limit of the ratio of the area of the high dielectric region to the total area (the value ranges from 0.1 to 06). In the process of numerical optimization, by adjusting the optimization parameters m, q and U _p , the spatial distribution of permittivity suitable for manufacturing and with good optimization effect is found.

In the calculation process, in order to obtain a clear boundary and facilitate the subsequent extraction of high dielectric regions and dielectric constant transition regions, after optimization, the value range of m is 1, 2 or 3, and q is 0-5.

In the constraint conditions, in order to adjust the permittivity in the design domain, the mathematical relationship between the density of artificial materials and the permittivity in the corresponding grid is established through the interpolation function shown in the first constraint condition, where ε _ri , ε _max and ε _min are the permittivity in the i-th grid, the upper limit of permittivity change (set to 20) and the lower limit of permittivity (set to the actual permittivity of insulators in the current project to 5.8). In order to reduce the area where the material properties change and reduce the difficulty of manufacturing, as shown in the third item of the constraint condition, the area of the high dielectric area is limited to U _p times the area of the design domain, U _p is the density utilization ratio, and The value ranges from 0 to 1, 0 means that the dielectric constant of the entire design area is ε _min , and 1 means that the dielectric constant of the entire design area is ε _max .

S102. According to the optimal spatial distribution result calculated in step S101, the region with a value range of the dielectric constant of 8 to 12 is set as a dielectric constant transition region, and the region with a value range of a dielectric constant of 14 to 20 is set as High dielectric area; and extract its surface profile according to the geometric shape of the dielectric constant transition area, generate a hollow 3D model, and set mechanical support points on the outside of the 3D model to fix the geometric model of the dielectric transition area on the metal mold among;

By means of software modeling, the boundary contour of the transition region with a dielectric constant ranging from 7 to 12 is extracted, and according to the structure of the supporting insulator metal mold, the support with threaded lines is added on the basis of the contour of the transition region The structure is used to fix the transition area in the metal mold used for pouring; the resin gate is reserved for the subsequent pouring of high dielectric areas; after the geometric model is established, generate stl files or stp files that can be used for 3D printing .

S103. Prepare high dielectric composite slurry by blending high dielectric filler/photosensitive resin, and ensure that the viscosity of the composite slurry (at 25°C) is lower than 5000mP by adjusting the filler type, particle size, content and other parameters s, the thickness under 405nm ultraviolet light irradiation with 100mW/ ^cm2 power is greater than 0.2mm; the dielectric constant of the fully cured composite material is in the range of 8-12, and the linear thermal expansion coefficient (under 25°C) is 30-50 within the range of ×10 ^-6 /K;

The high dielectric filler used in preparing the composite material in the transition region is high-filling strontium titanate, titanium dioxide ceramic filler or low-filling strontium titanate, titanium dioxide ceramic filler supplemented by carbon nanotubes and graphene conductive fillers. Several material ratios satisfying the above conditions are given as follows:

S104. Pour the composite slurry prepared in step S103 into a 355nm or 405nm light-curing 3D printer. The printer layer thickness is set to 0.05mm or 0.1mm, and the power of the ultraviolet light source is 45-100mW/cm ² , and it is formed by curing layer by layer. For the manufacture of the hollow dielectric transition region, the part is then placed in a post-curing box, and post-cured for 4 hours under the conditions of 60°C and 60mW/cm ² to increase the degree of curing of the part.

355nm or 405nm ultraviolet light source is a common industrial-grade 3D printer light source, which is easy to obtain. In addition, compared with its long-wavelength light source, it has stronger penetration ability and higher curing depth, which can ensure a higher printing success of the parts Rate. Exposure energy ranges from 45 to 100mW/cm ² , too low exposure energy will cause the energy penetrating into the resin to be lower than the critical exposure rate of the resin itself, resulting in low cured thickness and difficult molding of the product. Excessive exposure energy will cause the temperature rise of the area under the spot to be too high, causing damage to the structure of the resin itself, and it is also difficult to realize the molding of the part. Therefore, within the exposure energy of 45-100mW/cm ² , the curing thickness and curing degree can be controlled by adjusting the curing time to ensure the success rate of printing.

During the post-curing process in the transition zone, when the ambient temperature is 60°C and the curing time is 4 hours, the uncured components inside the part can obtain a higher degree of cross-linking under the condition that the chemical reaction is more active, thereby improving the part's durability. Mechanical properties, reduced coefficient of linear expansion.

S2. Heat-cured high-dielectric region: the heat-cured high-dielectric region is formed by vacuum casting of heat-cured epoxy resin composite slurry mixed with high-dielectric filler. The main function is to regulate the electric field along the surface of the insulator and at the root of the flange side; the specific steps are as follows:

S201. Composite the heat-cured epoxy resin and the high-dielectric filler, configure the high-dielectric composite slurry, and adjust the type, particle size, content and other parameters of the filler to ensure that the dielectric constant value of the composite slurry is between 18 and 18 after curing. Within the range of 20, the coefficient of linear thermal expansion (at 25°C) is within the range of 30 to 50×10 ^-6 /K;

The high dielectric filler used in the preparation of the high dielectric composite material is a high filling amount of strontium titanate, titanium dioxide ceramic filler or a low filling amount of strontium titanate, titanium dioxide ceramic filler supplemented by carbon nanotubes and graphene conductive fillers.

The following table lists the dielectric constant and linear expansion coefficient of composite materials under different filler types meeting the above conditions.

filler	Dielectric constant	Linear expansion coefficient (10 -6 /K)
Strontium titanate (35vol%)	20	32
Titanium dioxide (40vol%)	20	30
Carbon nanotubes (0.2wt%) + titanium dioxide (20vol%)	18	40
Graphene (0.2wt%) + strontium titanate (25vol%)	20	38

S202. Pour the slurry prepared in step S201 into the light-cured dielectric transition region obtained in step S1, and then put it into the metal mold used for casting the supporting insulator.

S3. Heat-cured low-dielectric region: The heat-cured low-dielectric region is the main part of the supporting insulator, which is formed by vacuum casting of heat-cured epoxy resin composite slurry mixed with low-dielectric filler. The main function is to bear the mechanical stress of the three-layer gradient support insulator in the operating environment and its installation and fixation in the GIS/GIL pipeline. Its manufacturing steps are:

S301. Composite the thermosetting epoxy resin and low dielectric filler, configure low dielectric composite slurry, and adjust the type, particle size, content and other parameters of the filler to ensure that the dielectric constant value of the composite slurry after curing is between 5 and Within the range of 5.8, the coefficient of linear thermal expansion (at 25°C) is within the range of 30～50×10 ^-6 /K;

The low dielectric filler used in the preparation of the low dielectric composite material can be one or a combination of alumina and silica ceramic fillers.

The following table lists the dielectric constant and linear expansion coefficient of composite materials under different filler types meeting the above conditions.

filler	Dielectric constant	Linear expansion coefficient (10 -6 /K)
Aluminum oxide (40vol%)	5.8	30
Silica (35vol%)	5.0	36
Aluminum oxide (20vol%) + silica (20vol%)	5.5	34
Aluminum oxide (10vol%) + silica (30vol%)	5.3	32

S302. Pour the low-dielectric composite slurry obtained in step S301 into the metal mold in step S2, and then adopt the epoxy resin casting scheme used in the project to complete the molding of the three-layer gradient support insulator.

Casting epoxy resin and alumina or silica powder are blended at 110-120°C and the vacuum degree is 1-2mbar for 1-2 hours, then add curing agent and the vacuum degree is 1-2mbar Under the conditions of 100°C for 8 hours, then raise the temperature to 120°C for 2 hours, then take out the insulator to complete demoulding, and finally raise the temperature to 130°C for 12 hours, then cool the temperature to room temperature and take it out, you can get three Layer gradient support insulators.

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. The components of the embodiments of the invention generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations. Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1, 110kV disc support insulator

A method for preparing a three-layer gradient GIS/GIL support insulator, which divides the insulator into three parts: a light-cured dielectric transition region, a heat-cured high-dielectric region, and a heat-cured low-dielectric region.

The light-cured dielectric transition area is made of light-cured 3D printing photosensitive composite materials. The main functions include insulating the internal gradient dielectric constant transition, internal support and fixing of the metal mold, and acting as a heat-cured high-dielectric area mold. The manufacturing steps are:

S101. Taking the reduction of the electric field intensity in the region at the three junction points on the flange side of the 110kV disc support insulator as the optimization goal, the insulators are discretized, and the dielectric constant in each tiny unit can be calculated based on the dielectric constant value of the matrix (here selected as 5.8) to the upper limit of the dielectric constant change (here selected as 20), through the topology optimization algorithm, to find the optimal spatial distribution of the internal dielectric constant of the supporting insulator. The mathematical description of the optimization problem is as follows:

Design variables: ε(r,z),(r,z)∈Ω ₁

optimize the target:

Restrictions:

The design variable is the dielectric constant in each tiny unit after discretization. Ω ₁ is the internal area of the insulator, and Ω ₂ is the area at the three junctions on the flange side of the supporting insulator. The optimization target is divided into two parts, and f ₁ is the electric field regulation item, which is used to reduce the electric field in the optimized target area Ω ₂ . C _ref is the normalization parameter of f ₁ , so that the value obtained in the initial calculation process is 1, so as to achieve the purpose of dimensionless. f ₂ is the gradient penalty term, which is used to control the form of the distribution of the permittivity. r is the abscissa in the two-dimensional axisymmetric coordinate system, z is the ordinate in the two-dimensional axisymmetric coordinate system, E is the electric field intensity in the optimization target area Ω ₂ , and Ω is the integral calculation area. The parameters A, h _mesh , and ρ are the area of the computational domain Ω ₁ , the maximum size of the mesh division, and the density of artificial materials in the mesh (the value range is 0-1). _The weight coefficient q is used to adjust the weight _of f1 and f2 in the total optimization objective.

In the calculation process, the value range of m is 2, and q is 0.1.

In the constraint conditions, in order to adjust the permittivity in the design domain, the mathematical relationship between the density of artificial materials and the permittivity in the corresponding grid is established through the interpolation function shown in the first constraint condition, where ε _ri , ε _max and ε _min are the permittivity in the i-th grid, the upper limit of permittivity change (set to 20) and the lower limit of permittivity (set to 5.8).

In order to reduce the area where the material properties change and reduce the difficulty of manufacturing, as shown in the third item of the constraint condition, the area of the high dielectric area is limited to U _p times the area of the design domain, U _p is the density utilization ratio, here selected as 0.6.

S102 , according to the optimal spatial distribution result calculated in step S101 , set a region with a dielectric constant value range of 8 to 12 as a dielectric constant transition region, as shown in FIG. 2 a . The area with a dielectric constant value ranging from 14 to 20 is set as a high dielectric area, as shown in Figure 2b; and its surface contour is extracted according to the geometry of the dielectric constant transition area to generate a hollow 3D model, and according to the support For the structure of the metal mold of the insulator, on the basis of the outline of the transition area, a mechanical support point with thread and a sprue are set on the outside of the three-dimensional model, which are used to fix the geometric model of the dielectric transition area in the metal mold and the high dielectric Area casting. After the geometric model is established, an stl file or stp file that can be used for 3D printing is generated.

S103. Prepare high dielectric composite slurry by blending 15vol% strontium titanate filler with photosensitive resin, ensure that the viscosity of the composite slurry (at 25°C) is 3200mP·s, 405nm ultraviolet radiation with 100mW/ ^cm2 power The thickness as seen is 0.52 mm; the dielectric constant of the fully cured composite material is 10, and the coefficient of linear thermal expansion (at 25°C) is 38×10 ^-6 /K.

S104. Pour the composite slurry prepared in S103 into a 355nm light-curing 3D printer. The thickness of the printer layer is set to 0.05mm, and the power of the ultraviolet light source is 45mW/cm ² . Through layer-by-layer curing and molding, the manufacture of the hollow dielectric transition area is completed. , and then put the part into the post-curing box, and post-cure for 4 hours under the conditions of 60°C and 60mW/cm ² to increase the degree of curing of the part. During the post-curing process in the transition zone, when the ambient temperature is 60°C and the curing time is 4 hours, the uncured components inside the part can obtain a higher degree of cross-linking under the condition that the chemical reaction is more active, thereby improving the part's durability. Mechanical properties, reduced coefficient of linear expansion.

The thermally cured high dielectric region is vacuum cast from a thermally cured epoxy composite slurry mixed with a high dielectric filler. The main function is to regulate the electric field along the surface of the insulator and at the root of the flange side; its manufacturing steps are:

S201. Composite heat-cured epoxy resin and 35vol% strontium titanate filler, configure high-dielectric composite slurry, the dielectric constant value of the composite slurry after curing is 20, and the linear thermal expansion coefficient (at 25°C) is 32× 10 ^-6 /K.

S202. Pour the slurry configured in S201 into the light-cured dielectric transition region obtained in S1, and then put it into the metal mold used for casting the supporting insulator.

The heat-cured low-dielectric region is the main part of the supporting insulator, which is formed by vacuum casting of heat-cured epoxy resin composite slurry mixed with low-dielectric filler. The main function is to bear the mechanical stress of the three-layer gradient support insulator in the operating environment and its installation and fixation in the GIS/GIL pipeline. Its manufacturing steps are:

S301. Composite heat-cured epoxy resin and 40vol% alumina filler, and configure low-dielectric composite slurry. The dielectric constant of the composite slurry after curing is 5.8, and the linear thermal expansion coefficient (at 25°C) is 30×10 ^{- 6} /K.

S302. Pour the low-dielectric composite slurry obtained in S301 into the metal mold in S2, and then adopt the epoxy resin casting scheme used in the project to complete the molding of the three-layer gradient support insulator. Specifically, the casting epoxy resin and alumina powder were blended for 1 hour at 110°C and a vacuum of 1mbar, and then added with a curing agent, and kept at 100°C for 8 hours under a vacuum of 1mbar. , and then raise the temperature to 120°C for 2 hours, then take out the insulator to complete demoulding, and finally raise the temperature to 130°C for 12 hours, then cool the temperature naturally to room temperature and take it out to obtain a three-layer gradient support insulator.

The simulation results show that under the lightning impulse voltage of 550kV, after using the three-layer gradient structure, the maximum electric field in the area of the three joint points at the flange of the insulator can be reduced from 16kV/mm to 7kV/mm for the homogeneous insulator; the flashover voltage test results show that Compared with the traditional homogeneous insulator, the prepared three-layer gradient 110kV disc insulator can increase the lightning impulse breakdown voltage from the initial 542kV to 619kV. The failure pressure in the hydrostatic test changed from a homogeneous 3.7MPa to 3.5MPa, still much higher than the allowable value of 2.4MPa. This shows that the three-layer gradient 110kV disc insulator prepared by the present invention has excellent mechanical and electrical properties.

Example 2: 110kV disc support insulator

A method for preparing a three-layer gradient GIS/GIL support insulator, which divides the insulator into three parts: a light-cured dielectric transition region, a heat-cured high-dielectric region, and a heat-cured low-dielectric region.

The light-cured dielectric transition area is made of light-cured 3D printing photosensitive composite materials. The main functions include insulating the internal gradient dielectric constant transition, internal support and fixing of the metal mold, and acting as a heat-cured high-dielectric area mold. The manufacturing steps are:

S101. With the optimization goal of homogenizing the electric field strength along the surface of the 110kV disc support insulator, discretize the insulator, and the dielectric constant in each micro unit can vary from the dielectric constant value of the matrix (selected as 5.8 here) to the dielectric constant change The upper limit (selected as 20 here) is changed, and the optimal spatial distribution of the internal dielectric constant of the supporting insulator is found through the topology optimization algorithm. The mathematical description of the optimization problem is as follows:

Design variables: ε(r,z),(r,z)∈Ω ₁

optimize the target:

Restrictions:

The design variable is the dielectric constant in each tiny unit after discretization. Ω ₁ is the internal area of the insulator, and Ω ₂ is the area at the three junctions on the flange side of the supporting insulator. The optimization target is divided into two parts, and f ₁ is the electric field regulation item, which is used to reduce the electric field in the optimized target area Ω ₂ . C _ref is the normalization parameter of f ₁ , so that the value obtained in the initial calculation process is 1, so as to achieve the purpose of dimensionless. f ₂ is the gradient penalty term, which is used to control the form of the distribution of the permittivity. r is the abscissa in the two-dimensional axisymmetric coordinate system, z is the ordinate in the two-dimensional axisymmetric coordinate system, E is the electric field strength in the optimized target area Ω ₂ , E _mean is the average field strength, and Ω is the integral calculation area . The parameters A, h _mesh , and ρ are the area of the computational domain Ω ₁ , the maximum size of the mesh division, and the density of artificial materials in the mesh (the value range is 0-1). _The weight coefficient q is used to adjust the weight _of f1 and f2 in the total optimization objective.

In the calculation process, the value range of m is 1, and q is 5.

In the constraint conditions, in order to adjust the permittivity in the design domain, the mathematical relationship between the density of artificial materials and the permittivity in the corresponding grid is established through the interpolation function shown in the first constraint condition, where ε _ri , ε _max and ε _min are the permittivity in the i-th grid, the upper limit of permittivity change (set to 20) and the lower limit of permittivity (set to 5.8).

In order to reduce the area where the material properties change and reduce the difficulty of manufacturing, as shown in the third item of the constraint condition, the area of the high dielectric area is limited to U _p times the area of the design domain, U _p is the density utilization ratio, here selected as 0.3.

S102 , according to the optimal spatial distribution result calculated in step S101 , set the region with a dielectric constant value range of 8 to 12 as a dielectric constant transition region, as shown in FIG. 2 c . The area with a dielectric constant value ranging from 14 to 20 is set as a high dielectric area, as shown in Figure 2d; and its surface contour is extracted according to the geometry of the dielectric constant transition area to generate a hollow three-dimensional model, and according to the support For the structure of the metal mold of the insulator, on the basis of the outline of the transition area, a mechanical support point with thread and a sprue are set on the outside of the three-dimensional model, which are used to fix the geometric model of the dielectric transition area in the metal mold and the high dielectric Area casting. After the geometric model is established, an stl file or stp file that can be used for 3D printing is generated.

S103. Prepare a high dielectric composite slurry by blending 20vol% titanium dioxide with a photosensitive resin, ensuring that the viscosity of the composite slurry (at 25°C) is 3600mP·s, and the viscosity is irradiated by 405nm ultraviolet light with a power of 100mW/ ^cm2 The thickness is 0.47mm; the dielectric constant of the fully cured composite material is 11, and the linear thermal expansion coefficient (under the condition of 25°C) is 35×10 ^-6 /K.

S104. Pour the composite slurry prepared in S103 into a 355nm light-curing 3D printer. The thickness of the printer layer is set to 0.1mm, and the power of the ultraviolet light source is 50mW/cm ² . Through layer-by-layer curing and molding, the hollow dielectric transition area is manufactured. , and then put the part into the post-curing box, and post-cure for 2 hours under the conditions of 60 ° C and 80 mW/cm ² to increase the degree of curing of the part. During the post-curing process in the transition zone, the ambient temperature is 60 ° C, and the curing time is 2 hours. The uncured components inside the part can obtain a higher degree of crosslinking under the condition that the chemical reaction is more active, thereby improving the part's durability. Mechanical properties, reduced coefficient of linear expansion.

The thermally cured high dielectric region is vacuum cast from a thermally cured epoxy composite slurry mixed with a high dielectric filler. The main function is to regulate the electric field along the surface of the insulator and at the root of the flange side; its manufacturing steps are:

S201. Composite heat-cured epoxy resin and 40vol% titanium dioxide filler, and configure high-dielectric composite slurry. After the composite slurry is cured, the dielectric constant value is 20, and the linear thermal expansion coefficient (at 25° C.) is 30×10 ^{− 6} /K.

S202. Pour the slurry configured in S201 into the light-cured dielectric transition region obtained in S1, and then put it into the metal mold used for casting the supporting insulator.

The heat-cured low-dielectric region is the main part of the supporting insulator, which is formed by vacuum casting of heat-cured epoxy resin composite slurry mixed with low-dielectric filler. The main function is to bear the mechanical stress of the three-layer gradient support insulator in the operating environment and its installation and fixation in the GIS/GIL pipeline. Its manufacturing steps are:

S301. Composite heat-cured epoxy resin and 35vol% silica filler, configure low-dielectric composite slurry, the dielectric constant of the composite slurry after curing is 5, and the linear thermal expansion coefficient (under 25°C) is 36×10 ^-6 /K.

S302. Pour the low-dielectric composite slurry obtained in S301 into the metal mold in S2, and then adopt the epoxy resin casting scheme used in the project to complete the molding of the three-layer gradient support insulator. Specifically, casting epoxy resin and silica powder were blended for 1 hour at 115°C and a vacuum of 2mbar, and then added with a curing agent, and kept at 100°C for 8 hours under a vacuum of 1mbar. After that, the temperature was raised to 115°C for 3 hours, and then the insulator was taken out to complete demoulding. Finally, the temperature was raised to 120°C and held for 16 hours, and then the temperature was naturally cooled to room temperature and taken out to obtain a three-layer gradient support insulator.

The simulation results show that under the lightning impulse voltage of 550kV, the maximum electric field along the surface of the insulator can be reduced from 14.8kV/mm to 10.6kV/mm after using the three-layer gradient structure; the flashover voltage test results show that the prepared three-layer Compared with the traditional homogeneous insulator, the gradient 110kV disc insulator can increase the lightning impulse breakdown voltage from the initial 542kV to 642kV. The failure pressure in the hydrostatic test changed from a homogeneous 3.7MPa to 3.4MPa, still much higher than the allowable value of 2.4MPa. This shows that the three-layer gradient 110kV disc insulator prepared by the present invention has excellent mechanical and electrical properties. Example 3: 550kV pot support insulator

A method for preparing a three-layer gradient GIS/GIL support insulator, which divides the insulator into three parts: a light-cured dielectric transition region, a heat-cured high-dielectric region, and a heat-cured low-dielectric region.

The light-cured dielectric transition area is made of light-cured 3D printing photosensitive composite materials. The main functions include insulating the internal gradient dielectric constant transition, internal support and fixing of the metal mold, and acting as a heat-cured high-dielectric area mold. The manufacturing steps are:

S101. Taking the reduction of the electric field intensity in the region at the three joint points on the flange side of the 550kV basin-type support insulator as the optimization goal, discretize the insulator, and the dielectric constant in each micro-unit can be calculated based on the dielectric constant value of the matrix (here selected as 5.8) to the upper limit of the dielectric constant change (here selected as 20), through the topology optimization algorithm, to find the optimal spatial distribution of the internal dielectric constant of the supporting insulator. The mathematical description of the optimization problem is as follows:

Design variables: ε(r,z),(r,z)∈Ω ₁

optimize the target:

Restrictions:

The design variable is the dielectric constant in each tiny unit after discretization. Ω ₁ is the internal area of the insulator, and Ω ₂ is the area at the three junctions on the flange side of the supporting insulator. The optimization target is divided into two parts, and f ₁ is the electric field regulation item, which is used to reduce the electric field in the optimized target area Ω ₂ . C _ref is the normalization parameter of f ₁ , so that the value obtained in the initial calculation process is 1, so as to achieve the purpose of dimensionless. f ₂ is the gradient penalty term, which is used to control the form of the distribution of the permittivity. r is the abscissa in the two-dimensional axisymmetric coordinate system, z is the ordinate in the two-dimensional axisymmetric coordinate system, E is the electric field intensity in the optimization target area Ω ₂ , and Ω is the integral calculation area. The parameters A, h _mesh , and ρ are the area of the computational domain Ω ₁ , the maximum size of the mesh division, and the density of artificial materials in the mesh (the value range is 0-1). _The weight coefficient q is used to adjust the weight _of f1 and f2 in the total optimization objective.

In the calculation process, the value range of m is 1, and q is 0.05.

In the constraint conditions, in order to adjust the permittivity in the design domain, the mathematical relationship between the density of artificial materials and the permittivity in the corresponding grid is established through the interpolation function shown in the first constraint condition, where ε _ri , ε _max and ε _min are the permittivity in the i-th grid, the upper limit of permittivity change (set to 20) and the lower limit of permittivity (set to 5.8).

In order to reduce the area where the material properties change and reduce the difficulty of manufacturing, as shown in the third item of the constraint condition, the area of the high dielectric area is limited to U _p times the area of the design domain, U _p is the density utilization ratio, here selected as 0.5.

S102. According to the optimal spatial distribution result calculated in step S101, set the region with a dielectric constant value range of 8 to 12 as a dielectric constant transition region, as shown in FIG. 2e. The region with a dielectric constant value ranging from 14 to 20 is set as a high dielectric region, as shown in Figure 2f; and its surface contour is extracted according to the geometry of the dielectric constant transition region to generate a hollow 3D model, and according to the support For the structure of the metal mold of the insulator, on the basis of the outline of the transition area, a mechanical support point with thread and a sprue are set on the outside of the three-dimensional model, which are used to fix the geometric model of the dielectric transition area in the metal mold and the high dielectric Area casting. After the geometric model is established, an stl file or stp file that can be used for 3D printing is generated.

S103. Prepare a high-dielectric composite slurry by blending 0.1wt% carbon nanotubes and 10vol% titanium dioxide filler with a photosensitive resin, and ensure that the viscosity of the composite slurry (at 25°C) is 2800mP·s and the power is 100mW/cm ² The thickness under 405nm ultraviolet light irradiation is 0.32mm; the dielectric constant of the fully cured composite material is 9, and the linear thermal expansion coefficient (under the condition of 25°C) is 42×10 ^-6 /K.

S104. Pour the composite slurry prepared in S103 into a 355nm light-curing 3D printer. The thickness of the printer layer is set to 0.05mm, and the power of the ultraviolet light source is 45mW/cm ² . Through layer-by-layer curing and molding, the manufacture of the hollow dielectric transition area is completed. , and then put the part into the post-curing box, and post-cure for 4 hours under the conditions of 60°C and 60mW/cm ² to increase the degree of curing of the part. During the post-curing process in the transition zone, when the ambient temperature is 60°C and the curing time is 4 hours, the uncured components inside the part can obtain a higher degree of cross-linking under the condition that the chemical reaction is more active, thereby improving the part's durability. Mechanical properties, reduced coefficient of linear expansion.

The thermally cured high dielectric region is vacuum cast from a thermally cured epoxy composite slurry mixed with a high dielectric filler. The main function is to regulate the electric field along the surface of the insulator and at the root of the flange side; its manufacturing steps are:

S201. Composite heat-cured epoxy resin with 0.2wt% carbon nanotubes and 20vol% titanium dioxide filler, configure high-dielectric composite slurry, the dielectric constant value of the composite slurry after curing is 20, and the coefficient of linear thermal expansion (25°C condition Bottom) is 40×10 ^-6 /K.

S202. Pour the slurry configured in S201 into the light-cured dielectric transition region obtained in S1, and then put it into the metal mold used for casting the supporting insulator.

The heat-cured low-dielectric region is the main part of the supporting insulator, which is formed by vacuum casting of heat-cured epoxy resin composite slurry mixed with low-dielectric filler. The main function is to bear the mechanical stress of the three-layer gradient support insulator in the operating environment and its installation and fixation in the GIS/GIL pipeline. Its manufacturing steps are:

S301. Composite heat-cured epoxy resin with 20vol% alumina plus 20vol% silica filler, and configure low-dielectric composite slurry. The dielectric constant of the composite slurry after curing is 5.5, and the coefficient of linear thermal expansion (under the condition of 25°C) ) is 34×10 ^-6 /K.

S302. Pour the low-dielectric composite slurry obtained in S301 into the metal mold in S2, and then adopt the epoxy resin casting scheme used in the project to complete the molding of the three-layer gradient support insulator. Specifically, pouring epoxy resin, alumina, and silica powder were blended for 2 hours at 115 ° C and a vacuum of 1 mbar, and then added with a curing agent, at 90 ° C under a vacuum of 2 mbar. Keep the temperature at 125°C for 7 hours, then raise the temperature to 115°C for 1 hour, then take out the insulator to complete the demoulding, and finally raise the temperature to 125°C and keep it for 15 hours, then cool it down to room temperature and take it out to get a three-layer gradient support insulator.

The simulation results show that under the lightning impulse voltage of 1675kV, after using the three-layer gradient structure, the maximum electric field in the area of the three joint points at the flange of the pot insulator can be reduced from 14.5kV/mm of the homogeneous insulator to 6.5kV/mm; flashover The voltage test results show that the lightning impulse breakdown voltage of the prepared three-layer gradient 550kV pot insulator can be increased from the initial 1752kV to 2275kV compared with the traditional homogeneous insulator. The failure pressure in the hydrostatic test changed from a homogeneous 3.8MPa to 3.6MPa, still much higher than the allowable value of 2.4MPa. This shows that the three-layer gradient 110kV disc insulator prepared by the present invention has excellent mechanical and electrical properties. Example 4: 252kV column support insulator

A method for preparing a three-layer gradient GIS/GIL support insulator, which divides the insulator into three parts: a light-cured dielectric transition region, a heat-cured high-dielectric region, and a heat-cured low-dielectric region.

The light-cured dielectric transition area is made of light-cured 3D printing photosensitive composite materials. The main functions include insulating the internal gradient dielectric constant transition, internal support and fixing of the metal mold, and acting as a heat-cured high-dielectric area mold. The manufacturing steps are:

S101. To reduce the electric field intensity in the metal insert/epoxy resin interface area of the 252kV post support insulator as the optimization goal, discretize the insulator, and the dielectric constant in each micro-unit can be determined by the matrix dielectric constant value (selected here 5.8) to the upper limit of the dielectric constant (here selected as 20), the optimal spatial distribution of the internal dielectric constant of the supporting insulator is found through the topology optimization algorithm. The mathematical description of the optimization problem is as follows:

Design variables: ε(r,z),(r,z)∈Ω ₁

optimize the target:

Restrictions:

The design variable is the dielectric constant in each tiny unit after discretization. Ω ₁ is the internal area of the insulator, and Ω ₂ is the area at the three junctions on the flange side of the supporting insulator. The optimization target is divided into two parts, and f ₁ is the electric field regulation item, which is used to reduce the electric field in the optimized target area Ω ₂ . C _ref is the normalization parameter of f ₁ , so that the value obtained in the initial calculation process is 1, so as to achieve the purpose of dimensionless. f ₂ is the gradient penalty term, which is used to control the form of the distribution of the permittivity. r is the abscissa in the two-dimensional axisymmetric coordinate system, z is the ordinate in the two-dimensional axisymmetric coordinate system, E is the electric field strength in the optimized target area Ω ₂ , E _mean is the average field strength, and Ω is the integral calculation area . The parameters A, h _mesh , and ρ are the area of the computational domain Ω ₁ , the maximum size of the mesh division, and the density of artificial materials in the mesh (the value range is 0-1). _The weight coefficient q is used to adjust the weight _of f1 and f2 in the total optimization objective.

In the calculation process, the value range of m is 3, and q is 0.2.

In the constraint conditions, in order to adjust the permittivity in the design domain, the mathematical relationship between the density of artificial materials and the permittivity in the corresponding grid is established through the interpolation function shown in the first constraint condition, where ε _ri , ε _max and ε _min are the permittivity in the i-th grid, the upper limit of permittivity change (set to 20) and the lower limit of permittivity (set to 5.8).

In order to reduce the area where the material properties change and reduce the difficulty of manufacturing, as shown in the third item of the constraint condition, the area of the high dielectric area is limited to U _p times the area of the design domain, U _p is the density utilization ratio, here selected as 0.3.

S102. According to the optimal spatial distribution result calculated in step S101, set the region with a dielectric constant value range of 8 to 12 as a dielectric constant transition region, as shown in FIG. 2g. The area with a dielectric constant value ranging from 14 to 20 is set as a high dielectric area, as shown in Figure 2h; and its surface contour is extracted according to the geometry of the dielectric constant transition area to generate a hollow 3D model, and according to the support For the structure of the metal mold of the insulator, on the basis of the outline of the transition area, a mechanical support point with thread and a sprue are set on the outside of the three-dimensional model, which are used to fix the geometric model of the dielectric transition area in the metal mold and the high dielectric Area casting. After the geometric model is established, an stl file or stp file that can be used for 3D printing is generated.

S103. Prepare high dielectric composite slurry by blending 0.2wt% graphene plus 8vol% strontium titanate filler with photosensitive resin, and ensure that the viscosity of the composite slurry (at 25°C) is 2500mP·s, 100mW/cm ² The thickness under 405nm ultraviolet light irradiation is 0.45mm; the dielectric constant of the fully cured composite material is 12, and the linear thermal expansion coefficient (at 25°C) is 48×10 ^-6 /K.

S104. Pour the composite slurry prepared in S103 into a 355nm light-curing 3D printer. The thickness of the printer layer is set to 0.1mm, and the power of the ultraviolet light source is 100mW/cm ² . Through layer-by-layer curing and molding, the manufacture of the hollow dielectric transition area is completed. , and then put the part into the post-curing box, and post-cure for 4 hours under the conditions of 60°C and 60mW/cm ² to increase the degree of curing of the part. During the post-curing process in the transition zone, when the ambient temperature is 60°C and the curing time is 4 hours, the uncured components inside the part can obtain a higher degree of cross-linking under the condition that the chemical reaction is more active, thereby improving the part's durability. Mechanical properties, reduced coefficient of linear expansion.

The thermally cured high dielectric region is vacuum cast from a thermally cured epoxy composite slurry mixed with a high dielectric filler. The main function is to regulate the electric field along the surface of the insulator and at the root of the flange side; its manufacturing steps are:

S201. Composite heat-cured epoxy resin with 0.2wt% graphene plus 25vol% strontium titanate filler, and configure high-dielectric composite slurry. The dielectric constant value of the composite slurry after curing is 20, and the linear thermal expansion coefficient (25° C. condition) is 38×10 ^-6 /K.

S202. Pour the slurry configured in S201 into the light-cured dielectric transition region obtained in S1, and then put it into the metal mold used for casting the supporting insulator.

The heat-cured low-dielectric region is the main part of the supporting insulator, which is formed by vacuum casting of heat-cured epoxy resin composite slurry mixed with low-dielectric filler. The main function is to bear the mechanical stress of the three-layer gradient support insulator in the operating environment and its installation and fixation in the GIS/GIL pipeline. Its manufacturing steps are:

S301. Composite heat-cured epoxy resin with 10vol% alumina plus 30vol% silica filler, and configure high-dielectric composite slurry. The dielectric constant of the composite slurry after curing is 5.3, and the coefficient of linear thermal expansion (under the condition of 25°C ) is 32×10 ^-6 /K.

S302. Pour the low-dielectric composite slurry obtained in S301 into the metal mold in S2, and then adopt the epoxy resin casting scheme used in the project to complete the molding of the three-layer gradient support insulator. Specifically, pouring epoxy resin, alumina, and silica powder were blended for 2 hours at 120°C and a vacuum of 2mbar, and then added with a curing agent, at 100°C under a vacuum of 2mbar. Keep the temperature at 120°C for 6 hours, then raise the temperature to 110°C for 4 hours, then take out the insulator to complete demoulding, and finally raise the temperature to 120°C and keep it for 16 hours, then cool the temperature naturally to room temperature and take it out to obtain a three-layer gradient support insulator.

The simulation results show that under the lightning impulse voltage of 1050kV, after using the three-layer gradient structure, the maximum electric field at the metal insert/epoxy resin interface of the insulator can be reduced from 35kV/mm for the homogeneous insulator to 20kV/mm; the flashover voltage test results show that, Compared with the traditional homogeneous insulator, the prepared three-layer gradient 252kV support insulator can increase the lightning impulse breakdown voltage from the initial 815kV to 980kV. The failure pressure in the hydrostatic test is increased from 3.5MPa to 3.7MPa, which is much higher than the allowable value of 2.4MPa. This shows that the three-layer gradient 252kV support insulator prepared by the present invention has excellent mechanical and electrical properties.

In summary, the present invention provides a method for preparing a three-layer gradient GIS/GIL support insulator. In terms of design concept, the dielectric constant transition region is introduced. On the one hand, it can better realize the electric field optimization along the surface or in the local area of the insulator. On the other hand, the dielectric constant transition can eliminate the macro interface in the high and low dielectric constant region, and realize the smooth transition of the dielectric properties of the material. In terms of manufacturing methods, photo-curing 3D printing is used to print a hollow dielectric constant transition area, which can realize the integrated molding of the gate, support structure and transition area. Compared with the solid structure, the 3D printing hollow structure can greatly improve the printing efficiency, the post-curing process is more effective, and the internal defects of the part can also be avoided. After the pouring is completed, the mold is also used as a part of the structure without taking it out, so that one-time molding can be realized. The linear thermal expansion coefficients of the three parts of the supporting insulator are relatively close, which can significantly improve the compatibility of the material interface under the temperature gradient and avoid the occurrence of internal mechanical stress.

The above content is only to illustrate the technical ideas of the present invention, and cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solutions according to the technical ideas proposed in the present invention shall fall within the scope of the claims of the present invention. within the scope of protection.

Claims (10)

1. A method for preparing a three-layer gradient GIS/GIL support insulator, characterized in that it comprises the following steps:

   Divide the supporting insulator into photo-cured dielectric transition region, heat-cured high-dielectric region, and heat-cured low-dielectric region; discretize the insulator, determine the constraints, and find the optimal spatial distribution of the internal dielectric constant of the supporting insulator, according to the optimal The spatial distribution results divide the dielectric constant transition area and the high dielectric area, generate a hollow three-dimensional model, and generate a hollow photo-curing dielectric transition area with supports and resin pouring ports through photo-curing 3D printing; The heat-cured epoxy resin composite slurry mixed with high dielectric filler is poured into the light-cured dielectric transition area, and then the light-cured dielectric transition area is placed in a metal mold to fix; The thermally cured epoxy resin composite slurry of the filler is poured into a metal mold to form a thermally cured low-dielectric region; finally, a three-layer gradient GIS/GIL support insulator is obtained through vacuum thermal curing.
2. The method according to claim 1, wherein the preparation of the light-cured dielectric transition region is specifically:

   S101. To reduce the electric field at the metal/epoxy resin interface of the insulator, the electric field along the surface of the insulator, or the electric field intensity in the area at the three joints on the flange side as the optimization goal, the insulator is discretized, and the dielectric constant in each micro unit is equal to the dielectric constant of the substrate. Change within the range from the constant value to the upper limit of the change of the dielectric constant, obtain the optimization target f through the topology optimization method, and determine the constraint conditions;

   S102. According to the optimization target f calculated in step S101, the region with a dielectric constant value of 8 to 12 is set as a dielectric constant transition region, and the region with a dielectric constant value of 14 to 20 is set as a high dielectric region ; Extract the surface contour according to the geometric shape of the dielectric constant transition area, generate a hollow three-dimensional model, and set mechanical support points and gates on the outside of the three-dimensional model;

   S103. Prepare high dielectric composite slurry by blending high dielectric filler/photosensitive resin;

   S104. Pour the high-dielectric composite slurry prepared in step S103 into a light-curing 3D printer, and form by layer-by-layer curing to complete the manufacture of a hollow dielectric transition area, and then put the part into a post-curing box for curing. treatment to obtain a photocured dielectric transition region.
3. The method according to claim 2, wherein in step S101, the optimization target f is as follows:

   

   Among them, Ω ₁ is the dielectric constant design area, Ω ₂ is the optimization target area 1, and Ω ₃ is the optimization target area 2; C _ref is the normalization parameter of the optimization component in the electric field integral item; A, h _mesh and ρ are respectively The area of the design area Ω ₁ , the maximum size of grid division, and the density of artificial materials in the grid; q is the weight coefficient, r is the abscissa in the two-dimensional axisymmetric coordinate system, and z is the abscissa in the two-dimensional axisymmetric coordinate system ordinate, E is the electric field strength in the optimization target area Ω ₂ , Ω is the integral calculation area;

   The constraints are:

   

   1≤m≤3, 0<ρ _i <1, 0≤q≤10

   

   Among them, ε _ri , ε _max and ε _min are the permittivity, the upper limit of permittivity change and the lower limit of permittivity in the i-th mesh, respectively, m is the density function shape control coefficient, ρ _i is the i-th mesh The material density in the grid; U _p is the upper limit of the ratio of the area of the high dielectric region to the total area.
4. The method according to claim 2, characterized in that, in step S103, the viscosity of the high dielectric composite slurry at 25°C is lower than 5000mP·s, and the thickness under 405nm ultraviolet light irradiation is greater than 0.2mm; completely The cured dielectric constant is 8-12, and the linear thermal expansion coefficient is 30-50×10 ^-6 /K.
5. The method according to claim 2, characterized in that, in step S104, the layer thickness of the printer is 0.05mm or 0.1mm, the power of the ultraviolet light source is 45-100mW/cm ² , and at 40-60°C, 60-80mW/cm ² under the conditions of curing 2 to 4 hours.
6. The method according to claim 1, wherein the preparation of the heat-cured high dielectric region is specifically:

   S201, compounding the thermosetting epoxy resin and the high dielectric filler, and configuring the high dielectric composite slurry;

   S202. Pour the high dielectric composite slurry prepared in step S201 into the light-cured dielectric transition region obtained in step S1, and then put it into the metal mold used for casting the supporting insulator to prepare the heat-cured high dielectric region.
7. The method according to claim 6, characterized in that in step S201, the cured composite slurry has a dielectric constant value of 18-20, and a linear thermal expansion coefficient of 30-50×10 ^-6 /K at 25°C.
8. The method according to claim 1, wherein the preparation of the heat-cured low-dielectric region is specifically:

   S301, compounding heat-cured epoxy resin and low-dielectric filler, and configuring high-dielectric composite slurry;

   S302. Pour the low-dielectric composite slurry obtained in step S301 into the metal mold in step S2, and then use an epoxy resin casting scheme to complete the molding of the three-layer gradient support insulator.
9. The method according to claim 8, characterized in that in step S301, the dielectric constant of the composite slurry after curing is 5-5.8, and the coefficient of linear thermal expansion at 25°C is 30-50×10 ^-6 /K .
10. The method according to claim 8, characterized in that, in step S302, the pouring epoxy resin and alumina or silica powder are blended for 1-2 hours under an environment of 110-120°C and a vacuum of 1-2mbar. hours, then add the curing agent, keep the temperature at 80-100°C for 6-8 hours at a vacuum degree of 1-2mbar, then raise the temperature to 110-120°C and keep it for 2-4 hours, then take out the insulator to complete demoulding. Finally, the temperature is raised to 120-130° C. and kept for 12-16 hours, and a three-layer gradient support insulator is obtained after cooling naturally to room temperature.

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