Microporous insulating material and method for its production, insulating part, gas-insulated switch

Abstract

The application discloses a kind of microporous insulating materials and preparation method thereof, insulating piece, gas-insulated switch, it is related to high-voltage insulating material technical field;The microporous insulating material provided by the application uses thermosetting resin as matrix, closed micropores are distributed in the matrix, the equivalent dielectric constant of the whole material can be matched with the environment-friendly insulating gas by adjusting porosity, so as to optimize the internal electric field distribution of GIS;At the same time, the dielectric constant of supercritical gas or high-pressure gas filled in the closed micropore is higher than that of normal-pressure gas, which is closer to the dielectric constant of thermosetting resin, thereby inhibiting the occurrence of partial discharge in the pore;In addition, the insulation strength of high-pressure gas in the micropore is higher than that of normal-pressure gas, which effectively reduces the safety hazard of micropore as a weak insulating point;The microporous insulating material provided by the application can be prepared into GIS core load-bearing and insulating components, meeting the demand of environment-friendly GIS, and having important significance for the green development of power equipment.

Description

Technical Field

[0001] This invention relates to the field of high-voltage insulation materials technology, and in particular to a microporous insulation material and its preparation method, an insulating component, and a gas-insulated switch. Background Technology

[0002] Gas-insulated switchgear (GIS) is a core device in power systems, and its reliability largely depends on the performance of the insulating medium. Traditional GIS commonly uses sulfur hexafluoride (SF6) as the gaseous insulating medium. However, SF6 is one of the strongest known greenhouse gases, with a global warming potential approximately 23,500 times that of carbon dioxide. Therefore, the use of environmentally friendly gases (such as dry air, N2 / O2 mixtures, etc.) in GIS has become an inevitable trend in power system development. However, the insulating performance of environmentally friendly gases is far inferior to that of SF6. This requires solid insulating components in GIS (such as basin insulators, support insulators, etc.) to withstand more severe electric field stresses and possess superior insulation performance. Traditional epoxy resin casting materials have a high dielectric constant (usually greater than 4.0), which is severely mismatched with the dielectric constant of environmentally friendly gases (close to 1.0). This leads to severe electric field distortion at the solid-gas interface, which can cause surface flashover and threaten equipment safety.

[0003] To address the aforementioned issues, microporous structures can be introduced to reduce the equivalent dielectric constant of solid insulating materials. However, porous materials prepared using traditional foaming processes suffer from two fatal flaws: first, uneven pore size distribution, with large pores easily becoming discharge initiation points; second, the gas inside the pores is at ambient pressure, with a dielectric constant much lower than that of the solid matrix, leading to electric field concentration within the pores. Under high field strength, local discharge first occurs inside the pores, causing cumulative damage to the material and eventually breakdown during long-term operation of GIS. While existing research has attempted to optimize pore size distribution and control porosity using supercritical fluid foaming, these processes are mostly "high-pressure impregnation-depressurization foaming-atmospheric pressure curing." Porous materials prepared by depressurization foaming and atmospheric pressure curing are essentially still composed of ambient pressure gas inside. Ambient pressure gas has a low dielectric constant and poor insulation performance, failing to solve the fundamental problem of electric field concentration within the pores. Summary of the Invention

[0004] This invention provides a microporous insulating material that matches the dielectric constant of environmentally friendly gases and effectively suppresses discharge within pores, as well as a method for preparing the same, aiming to meet the stringent requirements of environmentally friendly gas-insulated switches and insulating components for the insulation performance of solid insulating materials.

[0005] The microporous insulating material provided by the present invention includes a thermosetting resin matrix in which closed micropores are distributed; the closed micropores are filled with an insulating gas in a supercritical state or at a pressure higher than 2 MPa.

[0006] Optionally, the thermosetting resin matrix is ​​an epoxy resin.

[0007] Optionally, the insulating gas is argon or nitrogen.

[0008] Optionally, the porosity of the thermosetting resin matrix is ​​20% to 50%.

[0009] Optionally, the microporous insulating material further includes inorganic nanoparticles and reinforcing fibers dispersed in the thermosetting resin matrix; the inorganic nanoparticles have a particle size of 1~100nm, and the reinforcing fibers have a diameter of 1~100μm.

[0010] Optionally, the inorganic nanoparticles are nano-silica, and the reinforcing fiber is chopped E-glass fiber.

[0011] The microporous insulating material provided by this invention can be prepared by the following steps:

[0012] S1, Thermosetting resin and curing agent are mixed to form a slurry;

[0013] S2, the slurry is placed in a high-pressure container, insulating gas is introduced into the high-pressure container to make the pressure inside the high-pressure container higher than the critical pressure of the insulating gas, and the slurry is stirred to allow the insulating gas to enter the slurry;

[0014] S3, maintain the pressure inside the high-pressure container and heat the slurry to solidify it until it is fully formed;

[0015] S4, maintain the pressure inside the high-pressure container and cool the cured resin material to room temperature;

[0016] S5, the pressure inside the high-pressure container is gradually reduced to atmospheric pressure to obtain the microporous insulating material.

[0017] Optionally, before mixing the thermosetting resin with the curing agent, the method further includes the step of dispersing inorganic nanoparticles and reinforcing fibers in the thermosetting resin; wherein the particle size of the inorganic nanoparticles is 1~100nm and the diameter of the reinforcing fibers is 1~100μm.

[0018] Optionally, in steps S2 to S4, the pressure inside the high-pressure vessel is 5 to 15 MPa.

[0019] The present invention also provides an insulating component formed of the microporous insulating material described above; the insulating component includes, but is not limited to, basin insulators, support insulators, partition insulators, insulating tie rods, insulating cranks, sealing insulators, insulating bushings, arc-extinguishing chamber shells, arc-extinguishing nozzles, and current transformer insulating shells, etc.

[0020] The present invention also provides a gas-insulated switch, which includes an insulating gas and the insulating components described above; the insulating gas includes, but is not limited to, dry air, N2 / O2 mixture, etc.

[0021] The present invention has the following beneficial effects:

[0022] The microporous insulating material provided by this invention uses thermosetting resin as the matrix material. Closed micropores are distributed within the thermosetting resin matrix. By controlling the porosity, the overall equivalent dielectric constant of the material can be controlled within a range that achieves good matching with the dielectric constant of environmentally friendly insulating gases, thereby optimizing the electric field distribution inside GIS and avoiding problems such as surface flashover. Simultaneously, the closed micropores are filled with supercritical gas or high-pressure gas with a pressure higher than 2 MPa. The dielectric constant of these gases is higher than that of gases at atmospheric pressure and closer to that of the thermosetting resin matrix, thus alleviating the electric field concentration phenomenon at the solid-gas interface in the pores and suppressing the occurrence of partial discharge in the pores. Furthermore, the breakdown voltage of the gas is proportional to the gas density, and the insulation strength of the high-pressure gas inside the micropores is higher than that of gases at atmospheric pressure, effectively reducing the safety hazard of micropores becoming weak points in the insulation. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The flowcharts are for some embodiments of the preparation method of the microporous insulating material of the present invention.

[0025] Figure 2 This is a schematic diagram showing the distribution of the matrix, filler, and closed micropores in the microporous insulating material prepared in Example 1 of the present invention.

[0026] Explanation of reference numerals in the attached figures: 1. Resin matrix; 2. Closed micropores; 3. Nano-silica particles; 4. Short-cut E-glass fiber. Detailed Implementation

[0027] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] Experimental methods in the embodiments of this invention that do not specify specific conditions are generally performed under conventional conditions and conditions described in the manual, or under conditions recommended by the manufacturer; the general equipment, materials, reagents, etc. used are commercially available unless otherwise specified.

[0029] The microporous insulating material provided in this embodiment of the invention includes a thermosetting resin matrix in which closed micropores are distributed; the closed micropores are filled with an insulating gas in a supercritical state or at a pressure higher than 2 MPa.

[0030] The thermosetting resin matrix includes epoxy resin, phenolic resin, silicone resin, polyurethane resin, etc., and epoxy resin is preferred in the embodiments of the present invention. Epoxy resin has many advantages such as excellent dielectric properties, strong adhesion, high mechanical strength, aging resistance, and good processability, and is the mainstream electrical insulation material. There are many types of epoxy resin. The epoxy resins suitable for the embodiments of the present invention include, but are not limited to, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic type epoxy resin, alicyclic epoxy resin, etc. The epoxy resin needs to react with a curing agent (amine, acid anhydride, imidazole, etc.) to achieve irreversible cross-linking and curing (a small amount of accelerator can usually be added to reduce the curing temperature, shorten the curing time, and increase the cross-linking density. Accelerators include, but are not limited to, imidazole accelerators, amine accelerators, urea accelerators, etc.).

[0031] In this embodiment of the invention, the filling gas in the sealed micropores is an insulating gas, including but not limited to argon (Ar) or nitrogen (N2). Under the operating temperature of the microporous insulating material (e.g., -25℃ to 105℃), the internal pressure in the sealed micropores must always be higher than the standard atmospheric pressure, so that the dielectric constant and insulating strength of the insulating gas are higher than those of the gas at normal pressure. For example, at a pressure of 5MPa, the relative dielectric constant of Ar is about 1.025, which is significantly higher than the relative dielectric constant of Ar at normal pressure (about 1.0005). The dielectric constant of the high-pressure gas is closer to that of the resin matrix, which can suppress the occurrence of partial discharge at the interface between the microporous gas and the resin.

[0032] In some preferred embodiments, the porosity of the thermosetting resin matrix is ​​20% to 50%, that is, the closed micropores in the microporous insulating material account for 20% to 50% of the total volume of the material, so that the overall equivalent dielectric constant of the microporous insulating material is in the ideal range of 1.8 to 2.5.

[0033] In this embodiment of the invention, the supercritical state refers to a state in which the temperature and pressure of a gas both exceed its critical temperature and critical pressure. In this state, the interface between the gas and liquid phases disappears, forming a homogeneous fluid (supercritical fluid) that has the dual characteristics of both gas and liquid. When the gas exceeds the critical temperature, the gas cannot be liquefied, and when it exceeds the critical pressure, it transforms into a supercritical fluid. For example, the critical temperature of nitrogen is -147°C. When the temperature is greater than -147°C, nitrogen cannot be liquefied no matter how much pressure is applied. When the pressure is higher than the critical pressure (approximately 3.4 MPa), nitrogen exhibits a supercritical fluid state.

[0034] The microporous insulating material provided in this invention uses thermosetting resin as the matrix material. Closed micropores are distributed within the thermosetting resin matrix. By adjusting the porosity, the overall equivalent dielectric constant of the material can be controlled within a range that achieves good matching with the dielectric constant of environmentally friendly insulating gases (this range can be selected as a relative dielectric constant of 1.8~2.5), thereby optimizing the electric field distribution inside the GIS and avoiding problems such as surface flashover. Simultaneously, the closed micropores are filled with supercritical gas or high-pressure gas with a pressure higher than 2 MPa. The dielectric constant of these gases is higher than that of atmospheric pressure gases and closer to that of the thermosetting resin matrix, thus alleviating the electric field concentration phenomenon at the solid-gas interface in the pores and suppressing the occurrence of partial discharge in the pores. Furthermore, the breakdown voltage of the gas is proportional to the gas density, and the insulation strength of the high-pressure gas inside the micropores is higher than that of the atmospheric pressure gas, effectively reducing the safety hazard of the micropores becoming weak points in the insulation.

[0035] Microporous insulating materials, due to their porosity, have lower mechanical strength than resin materials without micropores. Therefore, to improve the mechanical properties of microporous insulating materials, in some embodiments, the microporous insulating materials also include inorganic nanoparticles and reinforcing fibers dispersed in a thermosetting resin matrix. The inorganic nanoparticles have a particle size of 1~100nm, and the reinforcing fibers have a diameter of 1~100μm. The micron-sized reinforcing fibers function to construct the skeleton structure, bear the main loads such as external tension and bending, and improve the load-bearing capacity of the resin material, while also improving the impact resistance of the resin material. The reinforcing fibers include, but are not limited to, fiber materials such as glass fiber, ceramic fiber, natural mineral fiber, and organic reinforcing fibers (aramid, ultra-high molecular weight olefin, polyimide, etc.). The nano-sized inorganic particles function to anchor the resin molecular chains, improving the strength and rigidity of the resin material. The inorganic nanoparticles include, but are not limited to, oxide inorganic particles such as nano-silica, nano-alumina, nano-titanium dioxide, and nano-zirconia, as well as nitride inorganic particles such as silicon nitride, boron nitride, and aluminum nitride.

[0036] In some specific embodiments, the inorganic nanoparticles are selected as nano-silica. Silica has high hardness and good chemical stability, and after surface modification (which can be achieved by silane coupling agents), it is compatible with the resin and can effectively suppress the accumulation of interfacial charges. The reinforcing fiber is selected as chopped E-glass fiber. Glass fiber has high tensile strength, is resistant to chemical corrosion, is lightweight, and has good compatibility with epoxy resin. E-glass fiber refers to alkali-free glass fiber, and chopped refers to the process of mechanically cutting E-glass fiber filaments to form short fibers of a fixed length (usually 1~12mm).

[0037] See Figure 1 The microporous insulating material proposed in this embodiment of the invention can be prepared by the following method, including steps S1 to S5:

[0038] S1, a slurry is formed by mixing thermosetting resin and curing agent.

[0039] For embodiments of microporous insulating materials doped with inorganic nanoparticles and reinforcing fibers, the step further includes dispersing the inorganic nanoparticles and reinforcing fibers in the thermosetting resin before mixing the thermosetting resin with the curing agent; after the thermosetting resin and the curing agent are mixed to form a slurry, the slurry is usually vacuum degassed to remove the air mixed in by stirring.

[0040] S2, place the slurry in a high-pressure container, fill the high-pressure container with insulating gas, so that the pressure inside the high-pressure container is higher than the critical pressure of the insulating gas, and stir the slurry to allow the insulating gas to enter the slurry.

[0041] In this step, the insulating gas is fully dissolved and dispersed in the resin matrix in the form of molecules or nanoparticles under conditions above the critical pressure and with stirring.

[0042] In some specific embodiments, the insulating gas is argon or nitrogen, and the pressure inside the high-pressure container is increased to 5-15 MPa by filling it with argon or nitrogen.

[0043] S3, maintain the pressure inside the high-pressure vessel and heat the slurry to solidify until fully formed.

[0044] This step is a key step in the embodiment of the present invention. During the heating and curing process of the slurry, as the temperature rises and the resin crosslinks, the dissolved gas is released to form pores. However, since the external pressure is always maintained at a high pressure, these pores are locked in a small size, forming a large number of closed, independent, and uniformly distributed micron-sized pores in the resin matrix. The small and uniform pores can maximize the mechanical properties of the material. At the same time, as the resin cures and forms, the high-pressure gas is sealed in these micropores, so that the gas in the micropores is in a supercritical state or a high-pressure state with a pressure higher than 2MPa.

[0045] S4, maintain the pressure inside the high-pressure container and cool the cured resin material to room temperature to avoid problems such as deformation, cracking, and collapse of the resin matrix and micropores due to stress caused by thermal shrinkage.

[0046] S5, the pressure inside the high-pressure vessel is slowly released to atmospheric pressure to obtain a microporous insulating material.

[0047] After cooling to room temperature, the strength of the resin material is sufficient to bind the high-pressure gas in the internal micropores. At this point, the pressure in the reactor is slowly reduced to atmospheric pressure to obtain the target microporous insulating material. Then, the microporous insulating material is subjected to necessary machining and surface treatment to obtain the insulating component.

[0048] In embodiments of the present invention, insulating components include, but are not limited to, basin insulators, support insulators, partition insulators, insulating tie rods, insulating cranks, sealing insulators, insulating bushings, arc-extinguishing chamber shells, arc-extinguishing nozzles, and current transformer insulating shells.

[0049] This invention also proposes a gas-insulated switch, wherein the insulating gas of the gas-insulated switch is an environmentally friendly gas such as dry air or N2 / O2 mixture, and the insulating component is prepared using the microporous insulating material provided in this invention.

[0050] Based on the above embodiments, the present invention also proposes the following specific embodiments. It should be noted that the following specific embodiments are merely exemplary and are not intended to limit the scope of protection of the present invention in any way.

[0051] Example 1

[0052] This embodiment describes the preparation of a supercritical argon-filled composite insulating support for 145kV environmentally friendly GIS. The preparation process includes the following steps:

[0053] Step 1, Material Preparation: By weight, 100 parts of bisphenol A epoxy resin (E-51), 85 parts of methylhexahydrophthalic anhydride (MeHHPA) as curing agent, 1 part of N,N-dimethylbenzylamine (BDMA) as accelerator, 20 parts of nano-silica particles (average particle size 30nm), 10 parts of chopped E-glass fiber (length 3mm), and high-purity argon gas (Ar, purity 99.999%, critical temperature -122.4℃, critical pressure 4.89MPa).

[0054] Step 2, Filler pretreatment and mixing: Add nano-silica particles to an ethanol solution of KH-560 and ultrasonically disperse for 1 hour, then dry for later use to attach epoxy functional groups to the surface of the nano-silica particles. Add the surface-treated nano-silica particles and chopped E-glass fibers to epoxy resin preheated to 60°C and stir with a high-speed mechanical stirrer for 2 hours. Then add curing agent and accelerator and continue stirring for 30 minutes to ensure uniform mixing and obtain slurry.

[0055] Step 2, Vacuum degassing: Place the slurry in a vacuum chamber and degas for 60 minutes at a vacuum of -0.09 MPa to remove air introduced during the stirring process.

[0056] Step 3, mold preparation and loading: Place the GIS insulation post mold preheated to 80℃ into the high-pressure reactor, and inject the vacuum-degassed slurry into the mold through the feed port.

[0057] Step 4, High-pressure impregnation and dispersion: Seal the high-pressure reactor and slowly inject high-purity argon gas into the reactor through a high-pressure gas cylinder and a booster pump until the pressure controller shows that the pressure inside the reactor reaches 8MPa (far higher than the critical pressure of Ar). Start the magnetic stirring device (non-contact type) inside the reactor and stir the slurry at low speed for 60 minutes at 80℃ and 8.0MPa to fully dissolve and disperse the argon gas in the epoxy resin slurry.

[0058] Step 5, Constant Pressure Curing: Maintain a constant pressure of 8 MPa inside the high-pressure reactor, start the heating system, and heat and cure the slurry according to the following procedure: First, heat to 100℃ and hold for 4 hours, then heat to 135℃ and hold for 10 hours; during this process, the resin system undergoes cross-linking and curing, simultaneously forming a large number of closed micropores filled with 8.0 MPa argon gas; see reference Figure 2 , Figure 2 The microstructure of the microporous insulating material is shown. Multiple closed micropores 2 are distributed in the resin matrix 1. The closed micropores 2 are filled with high-voltage insulating gas. The resin matrix 1 also contains nano-silica particles 3 and short-cut E-glass fibers 4.

[0059] Step 6, Pressure Holding, Cooling and Depressurization: After constant pressure curing and molding is completed, turn off the heating system and continue to maintain a pressure of 8MPa in the high-pressure reactor, allowing the reactor to cool naturally to room temperature (about 25°C); after complete cooling, slowly reduce the pressure in the reactor to atmospheric pressure within 2 hours through the pressure relief valve.

[0060] Step 7, Post-processing: Open the reactor, take out the formed insulating pillar sample, and perform post-processing such as grinding and cleaning.

[0061] The porosity of the insulating support sample prepared in this embodiment is about 35%, and the average pore size is less than 15 μm.

[0062] The insulation post sample was subjected to a voltage test in a constant temperature and humidity chamber, and the power frequency breakdown field strength was tested. The test results showed that the power frequency breakdown field strength of the insulation post sample was >40kV / mm. The mechanical tensile strength of the insulation post sample was tested using a universal testing machine, and the tensile strength of the insulation post sample was >80MPa. The insulation performance and mechanical strength of the insulation post sample fully meet the application requirements of 145kV environmentally friendly GIS.

[0063] As can be seen from the above embodiments, the microporous insulating material provided by the present invention uses thermosetting resin as the matrix material. Closed micropores are distributed within the thermosetting resin matrix. By adjusting the porosity, the overall equivalent dielectric constant of the material can be controlled within a range that achieves good matching with the dielectric constant of environmentally friendly insulating gas, thereby optimizing the internal electric field distribution of GIS and avoiding problems such as surface flashover. Simultaneously, the closed micropores are filled with supercritical gas or high-pressure gas with a pressure higher than 2 MPa. The dielectric constant of these gases is higher than that of atmospheric pressure gas and closer to that of the thermosetting resin matrix, thus alleviating the electric field concentration phenomenon at the solid-gas interface in the pores and suppressing the occurrence of partial discharge in the pores. Furthermore, the breakdown voltage of the gas is proportional to the gas density, and the insulation strength of the high-pressure gas in the micropores is higher than that of the atmospheric pressure gas, effectively reducing the safety hazard of micropores becoming weak points in insulation. The microporous insulating material provided by the present invention is sufficient to serve as the core load-bearing and insulating component of GIS, meeting the needs of environmentally friendly GIS and having significant implications for the green development of power equipment.

[0064] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A microporous insulating material, characterized in that, It includes a thermosetting resin matrix, wherein closed micropores are distributed in the thermosetting resin matrix; The closed micropores are filled with insulating gas in a supercritical state or at a pressure higher than 2 MPa.

2. The microporous insulating material according to claim 1, characterized in that, The insulating gas is argon or nitrogen.

3. The microporous insulating material according to claim 1, characterized in that, The porosity of the thermosetting resin matrix is ​​20% to 50%.

4. The microporous insulating material according to claim 1, characterized in that, It also includes inorganic nanoparticles and reinforcing fibers dispersed in the thermosetting resin matrix; The inorganic nanoparticles have a particle size of 1~100nm, and the reinforcing fibers have a diameter of 1~100μm.

5. The microporous insulating material according to claim 4, characterized in that, The inorganic nanoparticles are nano-silica, and the reinforcing fibers are chopped E-glass fibers.

6. A method for preparing a microporous insulating material, characterized in that, Includes the following steps: S1, Thermosetting resin and curing agent are mixed to form a slurry; S2, the slurry is placed in a high-pressure container, insulating gas is introduced into the high-pressure container to make the pressure inside the high-pressure container higher than the critical pressure of the insulating gas, and the slurry is stirred to allow the insulating gas to enter the slurry; S3, maintain the pressure inside the high-pressure container and heat the slurry to solidify it until it is fully formed; S4, maintain the pressure inside the high-pressure container and cool the cured resin material to room temperature; S5, the pressure inside the high-pressure container is gradually reduced to atmospheric pressure to obtain the microporous insulating material.

7. The method for preparing the microporous insulating material according to claim 6, characterized in that, Before mixing the thermosetting resin with the curing agent, the method further includes the following steps: Inorganic nanoparticles and reinforcing fibers are dispersed in the thermosetting resin; The inorganic nanoparticles have a particle size of 1~100nm, and the reinforcing fibers have a diameter of 1~100μm.

8. The method for preparing the microporous insulating material according to claim 6, characterized in that, In steps S2 to S4, the pressure inside the high-pressure vessel is 5 to 15 MPa.

9. An insulating component, characterized in that, The microporous insulating material is formed by the microporous insulating material according to any one of claims 1-5 or the microporous insulating material prepared by any one of claims 6-8.

10. A gas-insulated switch, characterized in that, It includes insulating gas and the insulating component as described in claim 9.

Images