Capacitive bushing based on thermoplastic material and preparation method thereof

Abstract

The invention discloses a capacitive bushing based on a thermoplastic material and a preparation method of the capacitive bushing. The capacitive bushing comprises a central conducting rod, a wiring terminal, an external insulator, a capacitor core, a measuring terminal, a flange and a voltage-sharing ball. The wiring terminal is located at the top of the sleeve and used for being connected with an external power source or power equipment, and the outer insulation layer covers the capacitor core to guarantee insulation between the structure and the external environment. The capacitor core is formed by alternately rolling a plurality of layers of metal foils and thermoplastic insulating materials, so that the uniformity and stability of electric field distribution can be ensured. The voltage-sharing ball is located at the bottom of the sleeve and used for uniformizing electric field distribution and reducing voltage gradient change. The capacitive bushing has the advantages of excellent insulating property, extremely high mechanical strength, good temperature resistance and light weight, materials can be recycled and reused, and the requirement of sustainable development is met. The device can be widely applied to a high-voltage power system, and the safety, durability and operation efficiency are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of preparation of capacitor bushings, and more particularly to a capacitor bushing based on thermoplastic material and a preparation method thereof. Background Art

[0002] In modern power transmission and distribution systems, capacitor bushings are key electrical insulation equipment, and the stability and safety of their performance directly affect the reliable operation of the power system. Traditional capacitor bushings are mainly made of materials such as ceramics, oil-impregnated paper, glue-impregnated paper, and glass fiber reinforced epoxy resin. However, these materials have gradually exposed many limitations in practical applications and are difficult to fully meet the high requirements of modern power systems for insulation equipment.

[0003] Among them, although the ceramic bushing has good insulation performance, it is heavy, which makes transportation and installation more difficult and more costly. At the same time, due to the brittleness of the ceramic material, it is easy to break during operation and use, increasing safety hazards.

[0004] Due to its inherent structural problems, oil-impregnated paper bushings are prone to defects such as poor sealing, internal moisture, and terminal overheating, and the failure rate has remained high for many years. The more serious safety hazard is that oil-paper bushing failures can easily cause transformer fires, causing huge economic losses, personal safety hazards, and adverse social impacts. Causing fire has become a fatal flaw of oil-paper bushings.

[0005] The rubber-impregnated paper casing has good insulation properties and mechanical strength to a certain extent, but its performance is easily degraded in harsh environments such as high temperature. It has many process steps, high control requirements, high costs and long production cycles. The finished products are prone to defects such as cracking, and the epoxy resin is difficult to recycle, which puts a certain amount of pressure on the environment and cannot meet the requirements of sustainable development.

[0006] Against the backdrop of rapid development of the electric power industry, and in the face of modern power equipment’s demand for environmentally friendly, high-performance materials, developing a new type of capacitor bushing material with excellent insulation performance, high mechanical strength, good temperature resistance, relatively light weight, and green recyclability has become an urgent issue to be addressed. Summary of the invention

[0007] In order to solve the problems existing in the prior art, the present invention provides a capacitive bushing based on thermoplastic material and a preparation method thereof, and the specific scheme is as follows:

[0008] A capacitive bushing based on thermoplastic material, the capacitive bushing comprises a central conductive rod, a wiring terminal, an outer insulation, a capacitor core, a measuring terminal, a flange and a voltage-equalizing ball; the wiring terminal is located at the top of the bushing and is used to connect an external power supply or power equipment; the outer insulation is an insulating layer covering the outside of the capacitive core,

[0009] The capacitor core is formed by alternately rolling multiple layers of metal foil and thermoplastic insulating material; the voltage-equalizing ball is located at the bottom of the sleeve and is used for evenly distributing the electric field.

[0010] For the present technical solution, the form of external insulation can be applied to various forms in the current prior art, including but not limited to the structural form proposed in this application, without affecting the basic insulation performance of the capacitive bushing.

[0011] Such as any one of thermoplastic insulating material sheds, silicone rubber composite insulating sleeves or porcelain sleeves. It is worth noting that the use of other insulation forms can still be considered as one of the ways to achieve the core purpose of this application. That is, the main improvement of this technical solution lies in the improvement of the internal structure, rather than the improvement of the external insulation part.

[0012] In order to improve the overall capacitor bushing forming efficiency and improve electrical performance.

[0013] Thermoplastic insulating materials can be selected from polytetrafluoroethylene, polyetheretherketone, polyphenylene sulfide, polyetherimide, PET, polyester, and polyimide;

[0014] Or choose chemically modified materials such as polytetrafluoroethylene, polyetheretherketone, polyphenylene sulfide, polyetherimide, PET, polyester, and polyimide;

[0015] or in the form of a composition containing one or more inorganic reinforcing materials;

[0016] or in the form of copolymers of polytetrafluoroethylene, polyetheretherketone, polyphenylene sulfide, polyetherimide, PET, polyester, or polyimide;

[0017] When the thermoplastic insulating material is in the form of a composition or a copolymer, the glass transition temperature of the composition or the copolymer is ≥ 120° C. When the glass transition temperature reaches above 120° C., it will be more advantageous for subsequent processing and molding procedures.

[0018] In the process of rolling and integrally forming, metal foil and thermoplastic insulating material film made of the above materials are alternately rolled and integrally melted and formed at the designed temperature and pressure. The core commonality of the above materials is that they can be thermoplastically formed and can meet certain temperature and pressure conditions, thereby obtaining a capacitor bushing with more stable performance, which is one of the core invention points of this technical solution and one of the significant differences between this technical solution and the existing technical solution.

[0019] Further, the structure of the capacitor core includes a rolled tube, a thermoplastic insulating material film, and a metal foil as a capacitor screen, a penultimate screen, and a final screen;

[0020] In the actual processing process, the voltage tap connected to the penultimate screen can be configured according to customer needs to draw voltage from the inside; the last screen is the outermost metal foil of the capacitor core, which is connected to the measurement terminal. This method is a preferred structural form and is not used as the basic structural design of this technical solution.

[0021] Furthermore, the outer insulation structure is a plurality of umbrella-shaped protrusions, each umbrella skirt is stacked and arranged in the longitudinal direction; the shape of the umbrella skirt is arc-shaped or conical, and each umbrella skirt gradually expands outward from the center to form a protective skirt.

[0022] Furthermore, the material used for modification and reinforcement is glass fiber, inorganic nanofiller or copolymer material.

[0023] A method for preparing a capacitive bushing based on a thermoplastic material, the method comprising the following steps:

[0024] S1: Rolling of metal foil and insulating film: Cut the metal foil and thermoplastic insulating film according to the designed size. During the rolling process, use automated equipment and precision control systems to strictly control the flatness and tightness of the metal foil and insulating film. The metal foil and insulating film are rolled alternately and stacked layer by layer to form the required multi-layer structure of the capacitor core. The metal foil can be aluminum foil, copper foil or a metal coating plated on a thermoplastic insulating material as the raw material of a single-layer metal foil.

[0025] S2: Molding of capacitor core: Place the rolled capacitor core into a high-precision mold to ensure accurate positioning and avoid core deviation. In a closed mold environment, perform high pressure and high temperature treatment to heat the thermoplastic insulating material to above its melting point to ensure that the thermoplastic material is integrated;

[0026] S3: Preparation of external insulation: If thermoplastic insulation material is used as the external insulation raw material, the preparation process is to prepare it through a mold once or twice, and inject or extrude the thermoplastic material to the outside of the core to form an external insulation structure of the designed structure; if silicone rubber composite insulation sleeve is used as the external insulation raw material, the silicone rubber composite insulation sleeve adopts a hollow composite insulator, and a silicone rubber shed is molded outside the glass fiber reinforced plastic cylinder;

[0027] S4: Subsequent processing and treatment: After cooling and forming, use high-precision processing equipment to adjust the size to ensure the accuracy of the external dimensions of the capacitor sleeve, and the processing error is controlled within ±0.1mm.

[0028] Furthermore, the rolling speed in S1 is set at 5-15 m / min, and the rolling pressure is controlled at 30-1000 N to avoid impurities, loose layers or uneven tension.

[0029] Furthermore, the heating time is controlled within 30-60 minutes to ensure that the thermoplastic material has a certain fluidity and can be completely integrated with each other to form a tightly sealed capacitor core structure with the capacitive screen.

[0030] Furthermore, the parameters of the high temperature and high pressure process used in the preparation of the capacitor core are: according to the selected thermoplastic material and the voltage level of the product produced, the temperature is controlled at 300-450°C, and the pressure is controlled at 5-30MPa at the above high temperature through special molding equipment, to ensure that the thermoplastic insulation layer material is evenly integrated under high temperature and high pressure, the thickness between the capacitor screen layers is uniform, and the outer surface of the core is smooth, dense and defect-free.

[0031] Beneficial effects:

[0032] The present invention provides a capacitive bushing based on thermoplastic material and a preparation method thereof, which has the following advantages:

[0033] (1) Excellent insulation performance: The capacitive bushing in the present invention uses high-performance thermoplastic material as the insulating medium, has excellent insulation performance, can effectively prevent current leakage and breakdown, and provide reliable protection for the safe operation of the power system with low accident costs. Through strict insulation performance tests such as power frequency withstand voltage test and partial discharge measurement, the insulation reliability of the bushing is verified to ensure compliance with relevant international and domestic standards and to meet the operating requirements under high-voltage environment.

[0034] (2) Extremely high mechanical strength: The high mechanical strength of thermoplastic materials enables the capacitor bushing to withstand greater mechanical stress, is not easily damaged, and has excellent toughness. Compared with traditional ceramic or epoxy resin bushings, it is more durable and adaptable to various complex environments. Mechanical tests such as tensile strength, bending strength, and impact strength ensure that the product meets the strict requirements of the power system and provides long-term mechanical stability.

[0035] (3) Significant weight reduction: Compared with traditional materials, the density of thermoplastic materials is relatively low, making the capacitive bushing lighter and easier to transport and install. This lightweight design reduces installation and transportation costs, improves work efficiency, and reduces pressure on equipment and facilities. The bushing's weight advantage has been verified through weighing analysis and comparative testing, which helps reduce operating costs.

[0036] (4) Excellent temperature resistance: The thermoplastic material used in the bushing has good high temperature resistance and can maintain stable physical and electrical properties in high temperature environments. This is particularly critical for power equipment working under high temperature conditions, ensuring that the bushing can continue to operate safely in harsh environments. The high temperature resistance stability of the bushing has been verified through thermal aging tests and high temperature withstand voltage tests.

[0037] (5) Easy to process: Thermoplastic materials have excellent processability and can be processed by various advanced processes such as compression molding and injection molding, with high production efficiency and low cost. At the same time, the material can be processed multiple times to meet various design and size requirements. Through the cooperation of automated equipment and precision control systems, the consistency and quality stability of the product processing process are ensured.

[0038] (6) Good recyclability: Thermoplastic materials are recyclable materials that meet the requirements of environmental protection and sustainable development. After the product's service life ends, the casing material can be recycled and reused, reducing resource waste and environmental pollution.

[0039] (7) Optimized dielectric properties: The bushing of the present invention has low dielectric constant and low dielectric loss characteristics, which reduces energy loss during power transmission, thereby improving power transmission efficiency. The effectiveness of the bushing in improving transmission efficiency has been confirmed through operation tests in actual power systems.

[0040] (8) Enhanced pollution flashover resistance: The outer insulation shed of the bushing is designed as a multi-layer shed structure, which increases the creepage distance and effectively improves the pollution flashover resistance. This structural design reduces the risk of failure caused by dirty environments. Through tests simulating dirty environments, the product's stable performance and pollution flashover resistance in harsh environments have been verified.

[0041] (9) Excellent hydrophobicity: For capacitor bushings, hydrophobic thermoplastic materials can prevent moisture from accumulating on the surface. In a humid environment, moisture may cause the insulation performance of electrical equipment to deteriorate, causing problems such as partial discharge. Hydrophobic materials can cause moisture to form water droplets and roll off, reducing the impact of moisture on insulation performance, thereby improving the reliability and service life of electrical equipment.

[0042] (10) It has excellent chemical corrosion resistance and oxidation resistance, and exhibits unparalleled stability in the face of extremely complex and harsh chemical environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A structural diagram of a capacitive bushing based on thermoplastic material.

[0044] Figure 2 It is a structural diagram of the capacitor bushing heavy capacitor core.

[0045] Figure 3 It is the structural diagram of the 0 screen in the capacitor core.

[0046] Figure ID:

[0047] 1. Wiring terminal; 2. External insulation; 3. Capacitor core; 4. Measuring terminal; 5. Voltage tap; 6. Flange; 7. Voltage equalizing ball; 3.1. Rolled tube; 3.2. Thermoplastic insulation material; 3.3. 0 screen; 3.4. The second to last screen; 3.5. Last screen; C1. 0 screen to voltage tap screen; C2. Voltage tap screen to last screen; C3. Last screen to grounding flange. DETAILED DESCRIPTION

[0048] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0049] Figure 1 It is a structural diagram of a capacitive bushing based on thermoplastic material, such as Figure 1 As shown, the capacitive bushing includes a central conductive rod, a terminal 1, an outer insulation 2, a capacitor core 3, a measuring terminal 4, a voltage tap 5, a flange 6 and a voltage equalizing ball 7; the terminal 1 is located at the top of the bushing and is used to connect an external power supply or power equipment; the outer insulation umbrella sleeve 2 is an insulating layer covering the outside of the capacitive bushing; the capacitor core 3 is formed by alternately rolling multiple layers of metal foil and thermoplastic insulating material; the voltage equalizing ball 7 is located at the bottom of the bushing and is used to evenly distribute the electric field.

[0050] Figure 2 It is a structural diagram of the capacitor bushing heavy capacitor core 3, such as Figure 2 The structure of the capacitor core 3 shown includes a rolled tube 3.1, a thermoplastic insulating material 3.2, a 0 screen 3.3, a penultimate screen 3.4, and an end screen 3.5; the penultimate screen 3.4 has a voltage tap 5 for drawing voltage from the inside; the end screen 3.5 is the outermost metal foil of the capacitor core 3 and is connected to the measuring terminal 4.

[0051] The choice of thermoplastic insulation material can be

[0052] 1. Polytetrafluoroethylene, polyetheretherketone, polyphenylene sulfide, polyetherimide, PET, polyester, polyimide;

[0053] 2. Or chemically modified materials of polytetrafluoroethylene, polyetheretherketone, polyphenylene sulfide, polyetherimide, PET, polyester, polyimide;

[0054] 3. Or in the form of a composition containing one or more inorganic reinforcing materials;

[0055] 4. Or in the form of a copolymer of polytetrafluoroethylene, polyetheretherketone, polyphenylene sulfide, polyetherimide, PET, polyester, or polyimide;

[0056] An embodiment of a method for preparing a capacitive bushing based on a thermoplastic material is given below:

[0057] Embodiment 1:

[0058] Using pure polytetrafluoroethylene or its modified film material as thermoplastic insulating material to prepare capacitor bushing

[0059] S1: Rolling of metal foil and insulating film

[0060] Aluminum foil is selected as the metal foil, and the insulating film is pure polytetrafluoroethylene (PTFE) or its modified material.

[0061] The material is cut to the designed size with a width deviation of ±0.05mm. Automated equipment is used with a rolling speed of 3-5m / min, a rolling tension of 150N / m, and a rolling pressure of 80kg. The material is rolled layer by layer in strict accordance with the design requirements to form a multi-layer capacitor core.

[0062] S2: Forming of capacitor core

[0063] The rolled core is placed in a mold, heated to 380±10°C in a closed mold, and a pressure of 3MPa is applied for 60 minutes to allow the PTFE to completely melt and tightly bond to form a defect-free capacitor core.

[0064] S3: Subsequent processing and treatment

[0065] After cooling, the external dimensions are trimmed and the error is controlled within ±0.1mm.

[0066] S4: Install the bushing, strictly check the capacitor core and other related parts, ensure the core position is accurate according to the design requirements, and then install the metal accessories, including flanges and other parts.

[0067] Sealing installation: Install the seal to ensure the tightness of the casing and prevent moisture and impurities from entering. The installation of the seal must be carried out strictly in accordance with the specifications to ensure the sealing effect.

[0068] Connection and fixing: Connect the casing to the external equipment, use appropriate connectors and fixing methods to ensure that the connection is firm and reliable. At the same time, check the connection parts to ensure that there is no looseness or leakage.

[0069] Testing and debugging: Test the assembled thermoplastic capacitive bushing, including electrical performance test, insulation resistance test, sealing test, etc. Debug and optimize according to the test results to ensure that the bushing performance meets the design requirements.

[0070] In the field of patent technology, an invention often carries the wisdom and efforts of the innovator. Its value and significance are not only reflected in the specific technical solutions presented, but also in the reasonable and comprehensive protection scope it should enjoy. As far as the present invention is concerned, the contents elaborated above are only some examples of more ideal and good application effects among many embodiments, and they shall not be regarded as a constraint or limitation on the protection scope of the present invention.

[0071] We are well aware that with the continuous development of science and technology and the increasing diversification of practical application scenarios, under the premise of following the inherent spirit and core principles of the present invention, various modifications may be made to the present invention based on various practical needs, technical improvement directions, market feedback and other factors. These modifications may be minor adjustments to a specific technical link, or they may be optimized and improved from the overall architecture level; at the same time, there may also be situations where equivalent replacements with existing technologies occur, that is, although the form of expression is slightly different, from the perspective of technical essence and functional realization, alternative solutions that can achieve the same effect as the original invention; furthermore, various improvements carried out for the purpose of further improving the performance of the present invention, expanding its application field or enhancing its adaptability are also reasonable and common situations.

Claims

1. A capacitive bushing based on thermoplastic material, characterized in that: The capacitive bushing includes a central conductive rod, a wiring terminal, an outer insulation, a capacitor core, a measuring terminal, a flange and a voltage-equalizing ball; the wiring terminal is located at the top of the bushing and is used to connect an external power supply or power equipment; The external insulation is an insulating layer covering the outside of the capacitor core, and the material of the external insulation is any one of thermoplastic insulating material, silicone rubber composite insulating material or ceramic material; The structure of the capacitor core is: Under the designed pressure and temperature conditions, multiple layers of metal foil and film-like thermoplastic insulating material are alternately rolled and melted into one structure through molds and control equipment; The pressure equalizing ball is located at the bottom of the sleeve.

2. A capacitive bushing based on thermoplastic material according to claim 1, characterized in that: The thermoplastic insulating material is polytetrafluoroethylene, polyetheretherketone, polyphenylene sulfide, polyetherimide, PET, polyester, polyimide; or chemically modified materials of polytetrafluoroethylene, polyetheretherketone, polyphenylene sulfide, polyetherimide, PET, polyester, and polyimide; or in the form of a composition containing one or more inorganic reinforcing materials; or in the form of copolymers of polytetrafluoroethylene, polyetheretherketone, polyphenylene sulfide, polyetherimide, PET, polyester, or polyimide; Wherein, when the thermoplastic insulating material is in the form of a composition or a copolymer, the glass transition temperature of the composition or the copolymer is ≥120°C.

3. A capacitive bushing based on thermoplastic material according to claim 1, characterized in that: In the structure of the capacitor core, the rolled tube, the thermoplastic material film and the metal foil are respectively used as the capacitor screen, the penultimate screen and the last screen; the penultimate screen is provided with a voltage tap for drawing voltage from the inside; the last screen is the outermost metal foil of the capacitor core and is connected to the measuring terminal.

4. A capacitive bushing based on thermoplastic material according to claim 1, characterized in that: The outer insulating structure is composed of multiple layers of umbrella-shaped protrusions, which are arranged in a longitudinal stacked manner. The umbrella-shaped protrusions are arc-shaped or cone-shaped, and expand outward from the center to form a protective skirt.

5. A method for preparing a capacitive bushing based on thermoplastic material, characterized in that: The preparation method comprises the following steps: S1: Rolling of metal foil and thermoplastic insulating film: The metal tube is used as the central conduit, and the metal foil is processed according to the designed size. During the rolling process, the rolling tension, pressure, flatness and tightness of the metal foil and the insulating film are controlled. The metal foil and the insulating film are rolled alternately according to the design requirements until the diameter required by the design is reached to form the required capacitor core; S2: Forming of capacitor core: (1) Place the rolled capacitor core into a hot pressing device and remove moisture and impurities from the material through drying and other process steps to ensure that the material can be fully integrated during the hot pressing process to avoid defects such as bubbles and cracks; (2) In the hot pressing process, the thermoplastic material is heated to a specified temperature to make it plastic, and then pressure is applied to make the material tightly bonded to form a specific shape of the capacitor core; (3) After hot pressing, the capacitor core is cooled to gradually cool down the capacitor core and fix its shape and performance; S3: Preparation of external insulation: Thermoplastic insulation material is used as the external insulation raw material, and the preparation process is to prepare it through a mold once or twice, and inject or extrude the thermoplastic material to the outside of the core to form an external insulation structure of the designed structure; S4: Subsequent processing and treatment: After cooling and forming, adjust the external dimensions of the capacitor sleeve and control the processing error within ±0.1mm.

6. The method for preparing a capacitive bushing based on thermoplastic material according to claim 5, characterized in that: In S1, the rolling speed is set at 2-10 m / min, the rolling tension is controlled at 100-300 N / m, and the pressure is controlled at 300-1000 N.

7. The method for preparing a capacitive bushing based on thermoplastic material according to claim 5, characterized in that: The heating time is controlled within 30-60 minutes.

8. The method for preparing a capacitive bushing based on thermoplastic material according to claim 5, characterized in that: The parameters of the high temperature and high pressure hot pressing process used in the preparation of the capacitor core are: According to the selected thermoplastic material and the voltage level of the product, the temperature is controlled at 300-450℃, and the pressure is controlled at 5-30MPa under the above high temperature by the molding equipment to ensure that the thermoplastic insulating material is evenly melted into one under hot pressing, the thickness between the capacitor screen layers is uniform, and the outer surface of the core is smooth, dense and defect-free.

9. The method for preparing a capacitive bushing based on thermoplastic material according to claim 5, characterized in that: The metal foil in S1 is aluminum foil, copper foil or a raw material of a single-layer metal foil obtained by plating a metal coating on a thermoplastic insulating material.

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