Low-temperature preparation method of high-resistance layer on side surface of closing resistor of circuit breaker

Abstract

The invention belongs to the technical field of electrical materials, and discloses a low-temperature preparation method of a high-resistance layer on the side surface of a closing resistor of a circuit breaker. Comprising the following steps: (1) raw material compatibility: weighing a silicate-based inorganic film-forming agent and a binder, and respectively dissolving the silicate-based inorganic film-forming agent and the binder in water to prepare a film-forming agent aqueous solution and a binder aqueous solution for later use; weighing an inorganic insulating filler for later use; (2) mixing: placing the film-forming agent aqueous solution, the binder aqueous solution and the inorganic insulating filler in a ball milling tank according to a specific ratio, and carrying out ball milling to obtain slurry; (3) spraying: uniformly spraying the slurry on the side surface and the inner hole of the closing resistor, and standing for later use after spraying is completed; and (4) curing: putting the closing resistor sprayed with the high-resistance layer into a muffle furnace, and sintering at low temperature in an air atmosphere to complete curing of the high-resistance layer. The high-resistance layer prepared by the invention not only has excellent insulating property and high-temperature resistance (gt; 500 DEG C), but also has high bonding strength with a matrix.

Description

Technical Field

[0001] This invention relates to the field of electrical materials technology, and more specifically to a high-resistivity layer on the side of a circuit breaker closing resistor and its low-temperature preparation method. Background Technology

[0002] The closing resistor of a circuit breaker is a key component in ultra-high voltage switchgear, used to suppress inrush current and overvoltage generated during closing, ensuring the safe and stable operation of the power system. It is mainly used at the contact points of 550 kV and above high-voltage circuit breakers. However, the closing resistor has a low resistivity (1~1000 Ω·cm) and poor surface insulation performance, making it prone to surface flashover under high electric field strength. Furthermore, due to the edge electric field concentration effect, the breakdown of the closing resistor generally occurs at the resistor's edge. Therefore, it is necessary to coat the side of the closing resistor with a high-resistivity insulating layer (high-resistivity layer) to transform the resistor side into an "insulator-air" interface, improving the surface flashover voltage level and reducing the flashover risk. However, currently, there is no high-resistivity layer in China that meets the requirements of such operating conditions and is ready for industrialization.

[0003] Currently, organic coatings and glass glazes are commonly used materials for the high-resistivity layer of closing resistors. However, closing resistors may face short-term high-temperature conditions (>350℃) during operation, which can cause problems such as carbonization and peeling of the high-resistivity layer of the organic system during use, leading to failure (Zhu Liqun, et al. Research on sealing coatings for aircraft engines, Acta Aeronautica Sinica, 2000, 21: 85-89; Gao Xiaoyu, et al. Research progress on preparation methods and performance of superhydrophobic coatings of organic polymers, Materials Protection, 2024, 57:75-83.). While glass glazes possess excellent high-temperature resistance, their sintering temperature is relatively high (>800℃), and their electrical resistance is prone to abrupt changes during sintering. Furthermore, secondary sintering can induce abnormal grain growth in the matrix, significantly degrading its mechanical properties (Wang Yongqing, et al. Development of Low-Temperature Fast-Firing Crystallizing Glaze, Journal of Ceramics, 2009, 30: 342-344; MWBarsoum, Fundamentals of Ceramics, 2003.). Therefore, there is an urgent need to develop novel high-resistivity layer formulations that can be prepared at low temperatures. These formulations should combine high-temperature resistance, electrical insulation, and high interfacial bonding strength to achieve precise control over electrical resistance and microstructure, providing key technical support for improving the operational reliability of closing resistors.

[0004] Silicate-based inorganic film-forming agents (sodium silicate, potassium silicate, etc.) have shown great potential in the preparation of high-resistivity layers on the side of closing resistors due to their low-temperature film-forming properties (200~600℃) and excellent comprehensive properties such as high insulation, high wear resistance, high thermal stability, and low coefficient of thermal expansion after film formation. Furthermore, silicates can undergo chemical bonding reactions with metal oxides on the substrate surface to form silicate compounds, thereby improving the adhesion between the glaze layer and the substrate. However, the industrial application of silicate-based high-resistivity layer systems is still limited by two major factors: firstly, the complex composition (such as ion / filler concentration) has a significant impact on film-forming temperature and performance; secondly, the slurry system (such as pH, rheology, etc.) has poor stability and is prone to coagulation and sedimentation. In addition, research on the application of this system in the field of high-resistivity layers on the side of closing resistors is still lacking.

[0005] Therefore, the key to preparing high-resistivity layers for high-performance closing resistors lies in how to accurately design and control the types and proportions of additives in the precursor, and evaluate its key properties such as electrical insulation and high temperature resistance. Summary of the Invention

[0006] In view of this, the present invention provides a low-temperature preparation method for a high-resistivity layer on the side of a circuit breaker closing resistor, and develops a formula for preparing the high-resistivity layer on the side of a circuit breaker closing resistor at a low temperature of 300℃. The high-resistivity layer prepared by this formula not only has excellent insulation performance and high temperature resistance (>500℃), but also has high bonding strength with the substrate. In addition, the resistance increment during the preparation process is small (<4%). The resulting high-resistivity layer has excellent overall performance, providing a solid foundation for the reliable operation of the closing resistor.

[0007] To achieve the above objectives, the present invention provides a low-temperature preparation method for a high-resistivity layer on the side of a circuit breaker closing resistor, comprising the following steps: (1) Raw material compatibility: Weigh the silicate-based inorganic film-forming agent and binder and dissolve them in water to prepare aqueous solutions of film-forming agent and binder for later use; weigh the inorganic insulating filler for later use; (2) Mixing: The film-forming agent aqueous solution, the binder aqueous solution and the inorganic insulating filler are placed in a ball mill jar in a specific ratio and ball milled to obtain a slurry; (3) Spraying: The mature spraying process is adopted, and the flow rate and spray width of the spray gun are adjusted according to the rheological characteristics of the slurry. The slurry is evenly sprayed on the side and inner hole of the closing resistor. After the spraying is completed, it is left to stand for later use. (4) Curing: The high-resistivity layer is sprayed onto the closing resistor and placed in a muffle furnace. It is then sintered at low temperature in an air atmosphere to achieve full curing and densification of the high-resistivity layer, thus completing the curing of the high-resistivity layer.

[0008] Preferably, in step (1), the silicate-based inorganic film-forming agent is selected from one or more of sodium silicate and potassium silicate; the binder is selected from one or more of organosilicon resin and alkoxychromium; and the inorganic insulating filler is composed of two or more of bauxite, clay, kaolin, alumina, zirconium oxide, titanium dioxide and chromium oxide.

[0009] Preferably, in step (1), the solid content of the film-forming agent aqueous solution is 50 wt.%, the solid content of the binder aqueous solution is 50 wt.%, and the inorganic insulating filler D 50 The size is 3~10 μm.

[0010] Preferably, the inorganic insulating filler is composed of bauxite, clay, zirconium oxide, titanium dioxide and chromium oxide in a ratio of 1:1:1:1:1 by mass.

[0011] Preferably, in step (2), the mass ratio of the film-forming agent aqueous solution, the binder aqueous solution and the inorganic insulating filler is 0.2~1:0.2~1:1~3.

[0012] More preferably, the mass ratio of the film-forming agent aqueous solution, the binder aqueous solution, and the inorganic insulating filler is 1:1:3.

[0013] Preferably, in step (2), the ball milling rate is 300~500 rpm / min and the time is 6h.

[0014] Preferably, in step (4), the low-temperature sintering operation is as follows: the temperature is increased from room temperature to 300℃ at a heating rate of 20℃ / min; and the high-resistance layer is cured by holding it at 300℃ for 2 hours.

[0015] As can be seen from the above technical solution, compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention addresses the problems of glass glazes, which are prone to sudden changes in closing resistance due to high sintering temperatures (>800℃), and organic high-resistivity layers, which are prone to carbonization and detachment under actual operating conditions due to insufficient temperature resistance (<350℃). A silicate-based high-resistivity layer formulation that is prepared at low temperatures and is stable at high temperatures was developed. By systematically controlling the types and proportions of silicate-based inorganic film-forming agents (sodium silicate, potassium silicate), binders (organosilicon resin, alkoxychromium), and inorganic insulating fillers (bauxite, clay, zirconium oxide, titanium dioxide, and chromium oxide) in the formulation, a novel silicate-based high-resistivity layer formulation was successfully developed, ultimately obtaining a high-resistivity layer on the side of the circuit breaker closing resistor with excellent overall performance.

[0016] The establishment of the silicate-based high-resistivity layer formulation and the determination of the low-temperature preparation method in this invention effectively improve the reliability of domestically produced closing resistors. This achievement has significant technical advantages, mature industrialization conditions, and broad market prospects.

[0017] This invention develops a complete set of formulations and preparation techniques for a novel high-resistivity layer on the side of a silicate-based closing resistor. The high-resistivity layer prepared at low temperatures exhibits excellent overall performance, with an insulation strength in air exceeding 1.3 kV / mm (1.5 / 50 μs), a temperature tolerance exceeding 500℃, an interfacial bonding strength reaching level two, and minimal impact of the sintering process on the ceramic body resistance (resistance increment <4%).

[0018] This achievement fills the technological gap in the industrialization of this field in China and provides key technical support for ensuring the reliable operation of domestically produced closing resistors. Attached Figure Description

[0019] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 (a) Microstructure and (b) Silicon element distribution of the silicate-based high-resistivity layer on the side of the circuit breaker closing resistor prepared in Example 1. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The closing resistor in ultra-high voltage circuit breakers needs to be coated with a high-resistivity insulating layer on its side to suppress surface flashover caused by electric field concentration. However, there is still a lack of mature high-resistivity layer formulations in China that combine adaptability to operating conditions and industrial feasibility. In existing technologies, organic coatings lack sufficient high-temperature resistance, while glass glaze layers are prone to abrupt changes in resistance and damage to the matrix performance due to excessively high sintering temperatures. Therefore, it is crucial to develop a novel high-resistivity layer that can be prepared at low temperatures and possesses high-temperature resistance, high insulation, and strong interfacial bonding strength. Silicate-based inorganic film-forming agents, with their unique low-temperature film-forming characteristics and strong adhesion to the matrix, demonstrate excellent comprehensive performance and show broad application prospects. However, how to synergistically optimize their component types and concentrations to comprehensively improve slurry stability and process versatility while ensuring the performance of the high-resistivity layer remains a core challenge that must be overcome in its industrialization process.

[0023] This invention develops a high-resistivity layer formulation based on silicates, employing controlled spraying technology to achieve uniform coating on the sides of the resistor, followed by low-temperature sintering to obtain the high-resistivity layer. The system characterizes its key performance indicators, such as electrical insulation, heat resistance, and interfacial bonding strength. Details are as follows: (1) Formulation development The formulation consists of silicate-based inorganic film-forming agents (one or more of sodium silicate, potassium silicate, etc., wherein the modulus of sodium silicate is between 1.5 and 3.0, and the modulus of potassium silicate is between 3.2 and 4.0), binders (one or more of organosilicon resin, alkoxychromium, etc., wherein the organosilicon resin is one or more of phenyl silicone resin, methyl silicone resin, or epoxy-modified silicone resin, and the alkoxychromium is aliphatic alkoxychromium), and inorganic insulating fillers (bauxite, clay, zirconium oxide, titanium dioxide, and chromium oxide, etc.).

[0024] ①Inorganic film-forming agents The inorganic film-forming agent is composed of one or more domestically produced sodium silicate, potassium silicate, etc. Each of these film-forming agents is dissolved in water to prepare an aqueous solution with a solid content of 50 wt.%. Different functional group types (SiO3) are designed... 2- alkoxy groups and metal complex ions (Na+, alkoxy groups) and other types of ions. + K + Si 4+ The formulation scheme controls the reaction kinetics and crosslinking density during film formation, and regulates the curing temperature, curing time, and film density and adhesion of the film-forming agent.

[0025] ② Adhesive The adhesive is composed of one or more of domestically produced organosilicon resins and alkoxychromium, etc. Each of the above adhesives is dissolved in water to prepare an aqueous solution with a solid content of 50 wt.%. Inorganic films with different physicochemical properties such as adhesion, bonding strength, hardness, and abrasion resistance are obtained by controlling different reaction mechanisms.

[0026] ③Inorganic insulating filler Inorganic insulating fillers are composed of bauxite, clay, kaolin, alumina, zirconium oxide, titanium dioxide, and chromium oxide, etc., and the D of each filler is... 50 With a particle size of 3~10 μm, it is moderate and easily distributed uniformly in film-forming agents and binders. The inorganic insulating filler is composed of bauxite, clay, zirconium oxide, titanium dioxide, and chromium oxide mixed and used in a ratio of 20:20:20:20:20:20.

[0027] (2) Mixing process In each embodiment or comparative example, one or more raw materials from the above categories are selected, placed in a ball mill jar according to a specific ratio, and ball milled for 6 hours before use.

[0028] (3) Spraying process A mature spraying process is adopted, and the flow rate and spray width of the spray gun are adjusted according to the rheological characteristics of the slurry to uniformly spray the slurry onto the side of the closing resistor. After completion, it is left to stand for later use.

[0029] (4) Curing process The high-resistivity coating is applied to the switching resistor and placed in a muffle furnace. Under air atmosphere, it is sintered at 300℃ for 2 hours to achieve full curing and densification of the high-resistivity layer, ultimately obtaining a high-resistivity layer with stable performance.

[0030] (5) Performance testing The key properties of high-resistivity layers with different formulations, such as electrical insulation performance, high temperature resistance, and interfacial bonding strength, were characterized and compared to verify the reliability of high-resistivity layers in engineering applications.

[0031] The present invention will be further described in detail below through specific embodiments. The amounts of film-forming agent, binder and insulating filler added in each embodiment and comparative example are shown in Table 1: Table 1

[0032] Taking Example 1 as an example, the mixing process of the inorganic film-forming agent, binder, and inorganic insulating filler is described in detail. The mixing process steps of the other examples and comparative examples are the same as those of Example 1, with differences only in the types and quantities of materials weighed. The specific steps are as follows: (1) Mixing process ① Weigh 200 g of 50 wt.% inorganic film-forming agent aqueous solution (sodium silicate) and 200 g of 50 wt.% binder aqueous solution (organosilicon resin) respectively, and pour them into a ball milling jar containing zirconia grinding beads in sequence; ② Weigh 600 g of inorganic insulating filler composed of bauxite, clay, zirconium oxide, titanium dioxide and chromium oxide, wherein the ratio of bauxite: clay: zirconium oxide: titanium dioxide: chromium oxide is 20:20:20:20:20, and pour it into the ball mill jar of step ① in sequence. ③ After ball milling at 450 rpm / min for 6 hours, it is ready for use.

[0033] (2) Spraying process Using a mature spraying process, the slurry is evenly sprayed onto the side and inner hole of the closing resistor using a spray gun. After spraying, it is left to stand for later use.

[0034] (3) Curing process The curing process is the same for all embodiments and comparative examples in this invention, and the specific steps are as follows: ① Heat from room temperature to 300℃ at a heating rate of 20℃ / min; ② Keep at 300℃ for 2 hours to complete the curing of the high-resistance layer.

[0035] (4) Performance testing The following performance tests were performed on the high-resistivity layers prepared in different embodiments and comparative examples: ① The bonding strength between the high-resistivity layer and the substrate was tested using the cross-cut test method; ② The change in resistance before and after curing was measured using a high-precision resistance meter, and the rate of change of resistance was calculated; ③ An impulse voltage of 1.2 / 50 μs was applied to the resistive sheet using an impulse voltage generator, and its insulation strength in air was tested; ④ The high-resistivity layer was kept in a muffle furnace at 500℃ for 2 h, and the bonding strength, insulation strength, and other properties of the high-resistivity layer before and after the heat preservation were tested, and the temperature resistance of the high-resistivity layer was detected.

[0036] Table 2

[0037] As shown in Table 2, the high-resistivity layers prepared in each embodiment under low-temperature conditions exhibit excellent comprehensive performance, with insulation strength exceeding 1.3 kV / mm, temperature resistance exceeding 500℃, and interfacial bonding strength reaching level two. Furthermore, the sintering process has minimal impact on the ceramic body's resistance (resistance increment <4%). This achievement fills a technological gap in the industrial-scale preparation of this material in China and has broad application prospects.

[0038] Furthermore, in the examples, the slurry obtained after mixing showed no sedimentation after 6-12 hours, but a small amount of sedimentation occurred after more than 12 hours, indicating that the slurry of the present invention has good stability.

[0039] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-temperature preparation method for a high-resistivity layer on the side of a circuit breaker closing resistor, characterized in that, Includes the following steps: (1) Raw material compatibility: Weigh the silicate-based inorganic film-forming agent and binder and dissolve them in water to prepare aqueous solutions of film-forming agent and binder for later use; weigh the inorganic insulating filler for later use; (2) Mixing: The film-forming agent aqueous solution, the binder aqueous solution and the inorganic insulating filler are placed in a ball mill jar in a specific ratio and ball milled to obtain a slurry; (3) Spraying: Spray the slurry evenly onto the side and inner hole of the closing resistor, and let it stand for later use after spraying. (4) Curing: Place the high-resistivity resistor with the sprayed coating in a muffle furnace and sinter it at low temperature in an air atmosphere to complete the curing of the high-resistivity layer.

2. The low-temperature preparation method of the high-resistivity layer on the side of the closing resistor of a circuit breaker according to claim 1, characterized in that, In step (1), the silicate-based inorganic film-forming agent is selected from one or more of sodium silicate and potassium silicate; the binder is selected from one or more of organosilicon resin and alkoxychromium; and the inorganic insulating filler is composed of two or more of bauxite, clay, kaolin, alumina, zirconium oxide, titanium dioxide and chromium oxide.

3. The low-temperature preparation method of the high-resistivity layer on the side of the closing resistor of a circuit breaker according to claim 1, characterized in that, In step (1), the solid content of the film-forming agent aqueous solution is 50 wt.%, the solid content of the binder aqueous solution is 50 wt.%, and the inorganic insulating filler D... 50 The size is 3~10 μm.

4. The low-temperature preparation method of the high-resistivity layer on the side of the closing resistor of a circuit breaker according to claim 2, characterized in that, The inorganic insulating filler is composed of bauxite, clay, zirconium oxide, titanium dioxide and chromium oxide in a ratio of 1:1:1:1:1 by mass.

5. The low-temperature preparation method of the high-resistivity layer on the side of the closing resistor of a circuit breaker according to claim 1, characterized in that, In step (2), the mass ratio of the film-forming agent aqueous solution, the binder aqueous solution and the inorganic insulating filler is 0.2~1:0.2~1:1~3.

6. The method for preparing a high-resistivity layer on the side of a circuit breaker closing resistor according to claim 1, characterized in that, In step (2), the ball milling rate is 300~500 rpm / min and the time is 6h.

7. The low-temperature preparation method of the high-resistivity layer on the side of the closing resistor of a circuit breaker according to claim 1, characterized in that, In step (4), the low-temperature sintering operation is as follows: the temperature is increased from room temperature to 300℃ at a heating rate of 20℃ / min; the temperature is maintained at 300℃ for 2 hours to complete the curing of the high-resistance layer.

8. A high-resistivity layer on the side of the closing resistor of a circuit breaker prepared by the method according to any one of claims 1-7.

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