Tool for high-voltage test of switch cabinet joint and production process thereof

Abstract

The invention relates to a production process of a tool for high-voltage test of a switch cabinet joint, which comprises the following steps of: preparing raw materials, and providing a conducting rod, a shielding net and an epoxy resin material; the conducting rod and the shielding net are processed, the end part of the conducting rod is provided with a cavity, the inner side wall is provided with threads, the outer surface is subjected to arc treatment, and the shielding net is cut and provided with threads for grounding; preparing and heating a mold; mounting and fixing the components; epoxy resin is subjected to injection molding and primary curing; taking out and finishing; and carrying out secondary curing. The technical problem that an existing high-voltage test tool is insufficient in structural sealing, electric field uniformity and manufacturing process control is solved.

Description

Technical Field

[0001] The present invention is a tooling for high - voltage testing of switchgear joints and its production process. Background Art

[0002] In a power distribution system with a voltage level of 35 kV and below, after equipment such as switchgear and cable joints are installed, on - site high - voltage insulation tests are usually required to verify the reliability of their electrical performance. Since most of these devices are of fully enclosed structure and cable joints are mostly of fully shielded form, traditional high - voltage testing methods are difficult to directly act on the inside of the joints, resulting in complex test operations and relatively high safety risks.

[0003] In the prior art, generally, the connection components are modified or part of the structure is removed to introduce high voltage. However, this not only increases the preparation work before the test but also easily affects the sealing and insulation performance of the subsequent equipment use due to structural damage. In addition, if the high - voltage introduction part lacks good electric - field control and insulation design, problems such as partial discharge and insulation breakdown may occur, even affecting the accuracy and repeatability of the test results.

[0004] Regarding the manufacture of high - voltage test tooling, there is currently a lack of a systematic and standardized production process. The existing products have the following problems in process control: unreasonable material selection, easy corrosion or poor contact of conductive components; imperfect shielding treatment, uneven electric - field distribution; poor forming accuracy of the insulation structure, insufficient local creepage distance; unstable temperature and pressure control during the curing process, affecting the density and mechanical strength of the finished product.

[0005] Therefore, there is an urgent need for a test - tooling production process with a standardized structure, selection of high - performance materials, precision injection molding, and high - voltage insulation design capabilities to meet the comprehensive requirements of cable - joint products in the high - voltage test process, such as structural connection, safety insulation, and electric - field shielding. This will help improve the consistency of the test device, the convenience of operation, and the safety during use. Summary of the Invention

[0006] The purpose of the present invention is to solve the above - mentioned deficiencies of the prior art and provide a tooling for high - voltage testing of switchgear joints and its production process.

[0007] A production process of a tooling for high - voltage testing of switchgear joints includes the following steps:

[0008] Raw material preparation: Provide a conductive rod, a shielding net, and epoxy resin material. The conductive rod is made of brass or stainless - steel material, and the shielding net is made of copper mesh;

[0009] Processing of the conductive rod and the shielding net: Process the conductive rod so that its end is provided with a cavity, the inner side wall of the cavity is provided with threads, and the outer surface is processed by an arc; Cut the shielding net and set M4 threads for grounding;

[0010] Mold preparation: Provide the mold and heat it to 120 °C;

[0011] Component installation and fixation: Fix the conductive rod and the shielding net in the mold cavity and apply a pressure of 20 MPa;

[0012] Epoxy resin injection molding: Inject the pre-mixed epoxy resin and keep it for 20 minutes to complete the preliminary curing;

[0013] Removal and trimming: Demold and clean the flash;

[0014] Secondary curing: Carry out thermal curing on the product at 120 °C for 3 - 5 hours.

[0015] Furthermore, the mixing ratio of the epoxy resin material is that the mass ratio of epoxy resin to curing agent is 100:30 - 40, and vacuum degassing treatment is carried out before injection.

[0016] Furthermore, the surface of the conductive rod is treated by electro-polishing or electroless nickel plating to enhance its corrosion resistance and electrical conductivity.

[0017] Furthermore, the mesh size of the shielding net is 0.1 mm to 0.3 mm, and it is connected to the conductive rod by silver soldering.

[0018] Furthermore, the mold is heated by electric heating or oil temperature heating, and the temperature is controlled between 115 °C and 125 °C.

[0019] Furthermore, an equalizing pressure of 0.5 to 1.5 MPa is applied after injecting the epoxy resin to improve the insulation density.

[0020] Furthermore, the secondary curing process includes stepwise temperature rise. In the first stage, it is cured at 80 °C for 2 hours, and in the second stage, it is cured at 120 °C for 3 hours.

[0021] Furthermore, the quality inspection process includes partial discharge testing, and the test voltage is 1.1 times the rated test voltage.

[0022] The trial tooling manufactured according to the above production process includes:

[0023] A conductive rod, with a cavity at its end, a threaded inner side wall of the cavity, and an outer surface with an arc surface structure for connecting with a cable joint;

[0024] A shielding net for electric field shielding, which is arranged inside the trial tooling and has an M4 thread on the side for grounding;

[0025] An insulating structure, in which the conductive rod and the shielding net are integrally coated with an epoxy resin material, and a shed structure is provided at the high-voltage introduction end;

[0026] Among them, the conductive rod is made of brass or stainless steel material, and the shielding net is made of copper mesh.

[0027] Beneficial effects: A 35kV distribution network line test equipment and its manufacturing method provided by the present invention can effectively solve the problems in the prior art such as the lack of a reliable high-voltage introduction structure, uneven test electric field distribution, high risk of partial discharge, and insufficient insulation protection ability during the insulation test of fully enclosed switchgear or fully shielded cables, and has the following beneficial effects:

[0028] By setting the M12 threaded end on the conductive rod, the present invention can directly achieve reliable fixed connection with the cable joint, avoid poor contact and discharge phenomena caused by temporary wiring or exposed connection, and realize a structured and highly stable high-voltage introduction method.

[0029] The outer part of the conductive rod adopts an arc transition structure, and the end is provided with an inner empty avoidance structure, which avoids the problems of sharp corner discharge and local electric field concentration, effectively controls the electric field distribution in the high-voltage area, and improves the electrical safety during the test process.

[0030] The provided copper mesh shielding structure can effectively cover the connection area between the test equipment and the cable joint, and is reliably connected to the grounding system through M4 threads, thereby suppressing the leakage of the electric field, avoiding interference with surrounding equipment, and improving the electromagnetic compatibility of the test environment.

[0031] The present invention designs a petticoat structure at the high-voltage access end, extends the voltage-to-ground path, increases the creepage distance, is suitable for insulation tests under harsh working conditions such as humidity and pollution, and meets the insulation protection standards of the 35kV voltage level.

[0032] Adopting the APG automatic pressure gel molding process to realize the integrated molding of the conductive rod, shielding net and insulation structure, improves the production efficiency and product consistency, and avoids the quality fluctuation problems caused by traditional manual encapsulation.

[0033] The conductive rod is selected from brass or stainless steel materials, the shielding net is selected from copper mesh, and the insulating layer is selected from epoxy resin. All are mature and reliable engineering materials, with good electrical conductivity, insulation and structural strength, ensuring that the equipment can be used stably for a long time.

[0034] The overall structure is compact, the interface is standardized, suitable for various types of 35kV cable joints, convenient for on-site installation, disassembly and reuse, and improves the efficiency of insulation test operations. Description of the drawings

[0035] Figure 1 is the flowchart of the production process of the trial tooling;

[0036] Figure 2 is the structural schematic diagram of the trial tooling;

[0037] Figure 3 It is a schematic diagram of the use of the trial tooling;

[0038] Figure 4 It is a connection diagram of the cable connector and the equipment casing;

[0039] In the figure, 1. conductive rod, 2. insulating structure, 3. shielding net, 4. cavity, 5. equipment casing, 6. cable connector, 7. trial tooling, 8. connecting guide rod. DETAILED DESCRIPTION

[0040] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0041] Embodiment 1: Production process

[0042] A production process of a switch cabinet joint high voltage test tool, comprising the following steps:

[0043] Raw material preparation: provide conductive rods, shielding nets and epoxy resin materials, wherein the conductive rods are made of brass or stainless steel, and the shielding nets are made of copper nets;

[0044] Conductive rod and shielding net processing: Process the conductive rod so that a cavity is provided at its end, the inner wall of the cavity is provided with threads, and the outer surface is processed with arcs; cut the shielding net and set M4 threads for grounding;

[0045] Mould preparation: provide the mould and heat it to 120℃;

[0046] Component installation and fixation: fix the conductive rod and shielding net in the mold cavity and apply 20MPa pressure;

[0047] Epoxy injection molding: Inject pre-mixed epoxy resin and hold for 20 minutes to complete the initial curing;

[0048] Removal and trimming: demoulding and cleaning of flash;

[0049] Secondary curing: thermally cure the product at 120°C for 3-5 hours;

[0050] Quality inspection: perform dimensional inspection, voltage resistance test and shielding performance test;

[0051] Finished product packaging and storage: Store in a dry environment after packaging.

[0052] Working principle:

[0053] Relying on the actual requirements of high-voltage introduction and electrical testing in the 35 kV distribution network line, an integrated and reliable high-voltage test interface component is achieved by optimizing the electrical connection structure and insulation encapsulation process. Its core principle is to stably introduce high voltage into the cable joint interior using a conductive rod with good electrical conductivity and structural strength. Meanwhile, a complete electric field shielding path is formed through the shielding net to reduce interference and prevent partial discharge. The end of the conductive rod is provided with an M12 thread and has an internal cavity design, which not only ensures a firm mechanical connection with the cable joint but also avoids interfering with the internal structure of the joint during electrical connection. The arc treatment on the outer surface of the conductive rod can effectively suppress sharp-corner corona and reduce electric field concentration. The structural design of the shielding net and the grounding interface can guide the uniform distribution of electric field lines and improve the safety of the system.

[0054] During the manufacturing process, by heating the mold to 120 °C and applying a pressure of 20 MPa, the temperature and pressure stability during molding can be maintained, which helps the full flow and uniform wrapping of epoxy resin. The epoxy resin undergoes vacuum degassing treatment before injection, which can effectively remove air bubbles during the mixing process and ensure the material is dense and void-free after injection. After injection, it is kept for 20 minutes for initial solidification to form a preliminary shape, and after demolding, the crosslinking reaction is completed through thermal curing (continuously at 120 °C for 3 - 5 hours) to improve the insulation performance and structural strength. The product is tested for dimensions, withstand voltage, and shielding performance to ensure it meets the usage requirements under national standards. The overall structure, through cooperation with the cable joint and testing equipment, realizes the stable introduction of high-voltage signals and the control of the test electric field, has high reliability and safety, and is suitable for on-site installation and high-voltage insulation testing.

[0055] The conductive rod is made of brass or stainless steel material, with a cavity structure machined at the end, and threads are provided inside the air. The cavity cooperates with the connecting rod at the end of the equipment bushing. The outside of the conductive rod is wrapped with insulating material, including the part extending into the cable joint, which can avoid interference with the metal connectors (such as washers and nuts) of the cable joint during installation. The outer surface of the conductive rod is designed with an arc transition to avoid electric field distortion caused by sharp corners. The shielding net is made of copper mesh, cut into a size adapted to the mold structure, and an M4 threaded hole is provided on the side to facilitate grounding connection during testing and reduce electric field leakage. The insulator part is injection-molded in one piece using epoxy resin material, taking into account both electrical insulation and mechanical strength.

[0056] The conductive rod serves as the introduction path for the test high voltage, ensuring a stable connection with the cable joint and transmitting high-voltage signals; the shielding net is used to suppress electric field interference under high voltage and conduct interference signals through grounding; the epoxy resin structure plays an overall insulation encapsulation and structural support role for the internal conductor and shield. The mold is the key tool for achieving precise molding and pressure maintenance, and its temperature control and fitting positioning structure determine the molding quality of the final product.

[0057] The manufacturing process starts with raw material preparation. The conductive rod needs to complete thread machining and cavity opening through a CNC lathe, and the outer surface is polished to form an arc transition. The shielding net needs to be cut and punched with M4 threaded holes. After the mold is heated to 120 °C, the two components are fixed at specific positions in the mold cavity, and a pressure of about 20 MPa is applied to ensure tight fitting. The pre-mixed epoxy resin is injected into the mold cavity and maintained for injection for 20 minutes. After initial curing, it is demolded. Subsequently, flash trimming is carried out, and it is thermally cured at 120 °C in an incubator for 3 - 5 hours to fully crosslink the material structure. Finally, size, withstand voltage, and shielding effect tests are carried out to ensure its performance meets the standards under 35 kV conditions.

[0058] The conductive rod and the shielding net are coaxially arranged in the mold through a positioning structure. The grounding hole positions on the side of the shielding net are docked with the mold ground wire connection structure to form an effective grounding circuit. The epoxy resin injection process ensures bubble removal through vacuum assistance. After injection molding, it forms a structurally integrated cable connector through thermal curing. The overall structure can be directly matched with the rear end of a 35 kV cable joint, facilitating on-site connection of test equipment and the object under test, and no additional auxiliary tools are required.

[0059] Furthermore, the ratio of the epoxy resin material is that the mass ratio of epoxy resin to curing agent is 100:30 - 40, and vacuum degassing treatment is carried out before injection.

[0060] By setting the mass ratio of epoxy resin to curing agent as 100:30 - 40, it ensures an appropriate crosslinking density during resin curing, thus taking into account curing speed, structural strength, and electrical insulation performance. This ratio range is precisely set according to the reaction rate and thermodynamic performance parameters of epoxy base materials and conventional amine or anhydride curing agents. Under the condition of maintaining medium-temperature curing (such as 120 °C), it can form a dense and uniform three-dimensional crosslinking network, meeting the dual requirements for insulation strength and mechanical properties under the 35 kV voltage level.

[0061] To further improve the material forming quality and dielectric uniformity, vacuum degassing treatment is carried out after resin mixing. By means of the principle of gas expansion and discharge under a negative pressure environment, the microbubbles remaining in the mixing process are eliminated. The specific operation is as follows: after the mixed epoxy resin system enters the vacuum cavity, the ambient pressure is reduced to -0.095 MPa and maintained for 5 to 10 minutes. Through continuous pumping, the bubbles escape from the liquid interior to the surface and burst. This step can significantly reduce the local insulation weak areas and potential discharge risks caused by bubbles.

[0062] The degassed epoxy system is immediately injected into the mold cavity that has been heated and pressurized to 20 MPa, and undergoes initial curing for 20 minutes under high temperature and high pressure conditions to form a stable primary structure. Subsequently, thermal curing at 120 °C for 3 - 5 hours further promotes the cross-linking of molecular chains, enabling the insulating material to have higher voltage withstand performance and long-term thermal stability. Throughout the process, vacuum degassing, as a pretreatment step, is decisive for the density, electrical strength, and dimensional consistency of the final product.

[0063] Furthermore, the surface of the conductive rod is treated by electro-polishing or electroless nickel plating to enhance its corrosion resistance and electrical conductivity. The surface-treated conductive rod can provide a more stable contact resistance and less energy loss when connecting to the high-voltage cable joint. At the same time, its antioxidant ability is significantly enhanced, making it not easy to form an electro-corrosion layer or surface oxide film, and maintaining a long-term good conductive channel. After nickel plating, the surface hardness is increased, which helps to improve the anti-wear ability of the threaded part.

[0064] Furthermore, the mesh size of the shielding net is 0.1 mm to 0.3 mm, and it is connected to the conductive rod by silver soldering. By controlling the mesh size of the shielding net between 0.1 mm and 0.3 mm, the conductive shielding performance and mechanical flexibility are effectively balanced, ensuring that it has a certain flexibility while achieving electric field shielding, which is convenient for integral molding with epoxy encapsulation. The smaller mesh size helps to improve the shielding efficiency, prevent electromagnetic interference leakage, and control the electric field distribution during the high-voltage test. The silver soldering connection technology uses the high conductivity and excellent wettability of silver to form a low-resistance and corrosion-resistant metal connection interface between the conductive rod and the shielding net. This connection method not only ensures electrical continuity but also improves the thermal stability and vibration resistance of the overall structure, and is a key component of a highly reliable electrical grounding path.

[0065] Furthermore, the mold is heated by electric heating or oil heating, and the temperature is controlled between 115 °C and 125 °C. By designing the mold heating method as electric heating or oil heating, it can be flexibly selected according to the on-site process conditions and equipment configuration. Among them, electric heating has the advantages of fast response speed and high temperature control accuracy, and is suitable for medium and small batch production; oil heating has a more uniform temperature distribution and is suitable for heating large structural part molds. Controlling the mold temperature in the range of 115 °C to 125 °C ensures that the epoxy resin has good fluidity and initial curing reaction rate after injection, avoiding quality problems such as uneven curing, bubble residue, and material delamination, and laying a foundation for the density and mechanical strength of the finished product.

[0066] Furthermore, after injecting the epoxy resin, an equalizing pressure of 0.5 to 1.5 MPa is applied to improve the insulation density. By applying an equalizing pressure of 0.5 to 1.5 MPa after the epoxy resin injection is completed, the internal material microstructure can be effectively compacted in the early stage of curing, preventing the regeneration of bubbles and micro cracks caused by material shrinkage, and improving the density and uniformity of the cured structure. This pressurization process, combined with the preset structure in the mold, helps to achieve a close combination between the overall insulating material and the conductive components and shielding layer, thereby improving the withstand voltage level and dielectric strength of the test equipment during high-voltage operation, and significantly reducing the risk of partial discharge.

[0067] Furthermore, the secondary curing process includes staged heating, with the first stage curing at 80°C for 2 hours and the second stage curing at 120°C for 3 hours. In the above scheme, the secondary curing treatment is carried out in a staged heating manner. The first stage is cured at 80°C for 2 hours to slowly promote the cross-linking reaction and reduce the internal stress concentration and premature surface curing problems caused by rapid temperature rise; then the second stage is cured at 120°C for 3 hours to complete the main chain cross-linking and improve the structural strength and thermal stability. This process path makes the curing process more uniform, prevents the formation of curing cracks or heat shrinkage voids, enhances the overall physical strength and dielectric consistency of the epoxy structure, and ensures the reliable performance of the finished product in long-term operation.

[0068] Furthermore, the quality inspection process includes a partial discharge test, and the test voltage is 1.1 times the rated test voltage. In the above scheme, the partial discharge test is included in the quality inspection link, and the test voltage is set to 1.1 times the rated test voltage in order to simulate the voltage stress under harsh operating conditions in advance, so as to evaluate whether the product has potential insulation defects or structural abnormalities. The partial discharge test can effectively detect electrical weak areas such as microcracks, voids, impurities, etc. that are difficult to identify by conventional visual or conventional withstand voltage tests, and is a key process in the reliability assessment of high-voltage equipment. This test method ensures the safety and stability of each batch of products shipped in actual use, in line with national standards and the high quality requirements of the power industry for 35kV insulation components.

[0069] Embodiment 2:

[0070] The trial tooling manufactured according to the production process of the first embodiment includes:

[0071] The conductive rod has a cavity at its end, a thread is provided on the inner wall of the cavity, and the outer surface is an arc surface structure, which is used to connect with the cable connector;

[0072] Shielding net, used for electric field shielding, the shielding net is arranged inside the trial tooling, and is provided with M4 thread on the side for grounding;

[0073] The insulating structure is made of epoxy resin material to cover the conductive rod and the shielding net as a whole, wherein the high voltage lead-in end is provided with an umbrella skirt structure;

[0074] Among them, the conductive rod is made of brass or stainless steel material, and the shielding net is made of copper mesh.

[0075] The working mechanism of the trial tooling is based on the triple coordination of high-voltage electrical connection, local electric field control, and insulation protection. During actual use, the conductive rod serves as the main path for high-voltage introduction and is reliably connected to the cable joint through the M12 threaded interface set at its end. The internal cavity design can effectively avoid fasteners in the joint such as nuts and washers, preventing mechanical interference and reducing the enhancement of the local electric field caused by the tip structure. The arc transition structure on the outer surface of the conductive rod makes the electric field distribution more uniform, suppressing the corona effect and partial discharge phenomenon, and enhancing its safe and stable operation ability under high-voltage conditions.

[0076] The shielding net is located outside the conductive rod and is used for on-site grounding through the M4 thread, playing the role of electric field balance and interference shielding. Its fine mesh design effectively prevents the leakage of high-frequency interference to the outside and also blocks external interference from entering the system internal, improving the accuracy of test data and the electromagnetic compatibility of system operation. There is a good contact between the shielding net and the conductive rod through internal design, and they are jointly embedded in the epoxy resin integral injection structure to avoid the breakdown path caused by the separation of the metal and resin interface.

[0077] The epoxy resin integral injection molding provides reliable electrical insulation and mechanical support for the conductive structure and shielding structure. The material itself has excellent voltage resistance performance and heat stability. After molding, a compact integrated insulation structure is formed, avoiding human assembly errors and enhancing the structural strength and service life. The high-voltage introduction end is provided with a petticoat structure, which increases the creepage distance and changes the direction of the surface electric field lines, preventing the concentration of the surface electric field at the high-voltage port and triggering safety risks such as flashover and arc discharge, ensuring the insulation stability under humid and high-voltage conditions.

[0078] Usage instructions: Insert one end of the equipment bushing with the connecting rod into the cable joint, and then insert the end of the trial tooling with the cavity from the other end of the cable joint and screw it in so that the connecting rod fits into the cavity of the conductive rod.

[0079] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. The production process of a tooling for high-voltage testing of switchgear joints is characterized in that, It includes the following steps: Raw material preparation: Provide a conductive rod, a shielding net and an epoxy resin material. The conductive rod is made of brass or stainless steel material, and the shielding net is made of copper mesh; Processing of the conductive rod and the shielding net: Process the conductive rod so that its end is provided with a cavity, the inner side wall of the cavity is provided with threads, and the outer surface is processed by an arc; Cut the shielding net and set threads for grounding; Mold preparation: Provide a mold and heat it to 120 °C; Component installation and fixation: Fix the conductive rod and the shielding net in the mold cavity and apply a pressure of 20 MPa; Epoxy resin injection molding: Inject the pre-mixed epoxy resin and keep it for 20 minutes to complete the preliminary curing; Removal and trimming: Demold and clean the flash; Secondary curing: Heat-cure the product at 120 °C for 3 - 5 hours.

2. The production process according to claim 9, characterized in that, Among them, The mixing ratio of the epoxy resin material is that the mass ratio of epoxy resin to curing agent is 100:30 - 40, and vacuum degassing treatment is carried out before injection.

3. The production process according to claim 10, characterized in that, The surface of the conductive rod is treated by electro-polishing or electroless nickel plating to enhance its corrosion resistance and electrical conductivity.

4. The production process according to claim 9, characterized in that, The mesh size of the shielding net is 0.1 mm to 0.3 mm, and it is connected to the conductive rod by silver soldering.

5. The production process according to claim 9, characterized in that, The mold is heated by electric heating or oil temperature heating, and the temperature is controlled between 115 °C and 125 °C.

6. The production process according to claim 9, characterized in that, Apply an equalizing pressure of 0.5 to 1.5 MPa after injecting the epoxy resin to improve the insulation density.

7. The production process according to claim 9, characterized in that, The secondary curing process includes staged heating. The first stage cures at 80 °C for 2 hours, and the second stage cures at 120 °C for 3 hours.

8. The trial tooling manufactured according to the production process of claim 1, characterized in that, It includes: A conductive rod, whose end is provided with a cavity, the inner side wall of the cavity is provided with threads, and the outer surface has an arc surface structure for connecting with a cable joint; A shielding net for electric field shielding. The shielding net is arranged inside the test tooling and is provided with M4 threads on the side for grounding; An insulating structure, which integrally coats the conductive rod and the shielding net with an epoxy resin material. Among them, the high-voltage introduction end is provided with a petticoat structure; Among them, the conductive rod is made of brass or stainless steel material, and the shielding net is made of copper mesh.

Images