A kind of perfusion mold tube, a dry-type transformer winding lead and manufacturing method

Abstract

The application discloses a pouring mold pipe, a dry-type transformer winding lead and a manufacturing method. The dry-type transformer winding lead comprises a winding lead body and an insulation layer. The insulation layer is formed by pouring, and the root of the insulation layer covers the root of the winding lead body. The insulation layer comprises an insulation base and an integrated umbrella skirt. The umbrella skirt is arranged along the axis direction of the insulation base. In the application, the insulation layer is formed by pouring. Compared with the traditional wrapping insulation tape method, the pouring insulation layer has higher efficiency. Secondly, the space of the winding lead body root is sufficient to accommodate the root of the pouring mold pipe, so that the root of the insulation layer can completely cover the winding lead root, thereby eliminating the insulation weak point of the insulation layer. In addition, the setting of the umbrella skirt in the insulation layer improves the creepage performance and the anti-pollution ability. In addition, the umbrella skirt and the insulation base in the application are integrally formed by pouring, and the size of each umbrella skirt is consistent, thereby ensuring the stability of the creepage performance.

Description

Technical Field

[0001] This invention relates to the field of dry-type transformer technology, and in particular to a casting mold tube, a dry-type transformer winding lead wire, and a manufacturing method thereof. Background Technology

[0002] In dry-type transformers, such as dual high-voltage ratio dry-type transformers, the winding leads are often laid out using a unified top-outlet configuration. Dry-type transformers with unified top-outlet configurations have stringent requirements for the insulation distance, withstand voltage level, and creepage performance of the winding leads.

[0003] Current technologies generally employ a method of wrapping the winding leads with multiple layers of insulating tape to form the insulation layer of the winding leads. However, this method has several drawbacks: First, the wrapping process is cumbersome, highly dependent on manual labor, and has low production efficiency; second, the space at the root of the winding leads is narrow, making it difficult to wrap the insulating tape properly, which can easily create weak points in the insulation, leading to breakdown in the power frequency withstand voltage test and poor product reliability; third, the insulation layer is prone to moisture and dirt accumulation during long-term operation, has insufficient creepage distance, and weak resistance to pollution.

[0004] Therefore, how to improve the production efficiency of the insulation layer, eliminate the weak points of the insulation layer, and ensure the creepage distance are key issues that urgently need to be solved by those skilled in the art. Summary of the Invention

[0005] This invention proposes a dry-type transformer winding lead with high insulation layer fabrication efficiency, no weak points in the insulation, and excellent creepage performance. This invention also proposes a casting mold tube and a method for fabricating the dry-type transformer winding lead.

[0006] To achieve the above objectives, the present invention discloses the following technical solutions:

[0007] A dry-type transformer winding lead includes a winding lead body and an insulating layer covering the winding lead body. The insulating layer is formed by injection molding, and the root of the insulating layer covers the root of the winding lead body.

[0008] The insulating layer includes an insulating substrate and a skirt integrally formed on the insulating substrate, wherein the skirt is a plurality of skirts arranged along the axial direction of the insulating substrate.

[0009] Preferably, the end of the winding lead body is welded to a copper busbar, and the welded portion between the winding lead body and the copper busbar is covered by the insulating layer.

[0010] Preferably, the distance between two adjacent umbrella skirts is 20-30mm; the depth of the umbrella skirt is 5-8mm.

[0011] Preferably, the insulating layer is made of nano-silica modified room-temperature curing epoxy resin.

[0012] The present invention also provides a casting mold tube, including a tube body, which is coaxially sleeved on the outside of the winding lead body of a dry-type transformer. The inner wall of the tube body and the outer wall of the winding lead body form a casting cavity, which is used to form an insulating layer. An annular groove is provided on the inner wall of the tube body, which is used to form the skirt. There are multiple annular grooves, which are spaced apart along the axial direction of the tube body.

[0013] Preferably, the tube is a flexible tube.

[0014] Preferably, one end of the tube is located outside the root of the winding lead body, while the other end is located outside the copper busbar, and the tube encloses the welding part between the winding lead body and the copper busbar.

[0015] The present invention also provides a method for manufacturing winding leads of a dry-type transformer, using the above-mentioned injection molding tube, comprising:

[0016] S1: Select the injection molding tube, wherein the length of the injection molding tube is longer than the length of the winding lead body by a first preset value, and the inner diameter of the injection molding tube is larger than the outer diameter of the winding lead body by a second preset value.

[0017] S2: The injection molding tube is sleeved over the winding lead body;

[0018] S3: Compress the injection mold tube from the end to the root of the injection mold tube to expose the end of the winding lead body, weld the end of the winding lead body to the copper busbar, and after welding, restore the injection mold tube to its natural state.

[0019] S4: Seal the gap between the root of the injection mold tube and the root of the winding lead body;

[0020] S5: Move the dry-type transformer into the vacuum tank, with the end opening of the injection mold tube serving as the injection port, and seal the injection port to the injection pipeline of the injection device.

[0021] S6: Evacuate the vacuum tank and inject nano-silica modified room temperature curing epoxy resin into the injection mold tube under preset negative pressure conditions through the injection device. After injection, maintain the preset negative pressure for a preset time.

[0022] S7: First preset time for curing at room temperature, second preset time for curing after heating;

[0023] S8: Remove the injection mold tube.

[0024] Preferably, step S4 specifically involves using room-temperature curing epoxy resin to seal the gap between the root of the injection mold tube and the root of the winding lead body.

[0025] Preferably, step S7 specifically involves curing at room temperature (20℃-25℃) for 24 hours, followed by curing at 38℃-42℃ for 4 hours.

[0026] As can be seen from the above technical solution, in this invention, the insulation layer is injection molded, which is more efficient than the traditional method of wrapping insulation tape. Secondly, the space at the root of the winding lead body is sufficient to accommodate the root of the injection molding tube; therefore, the root of the injection-molded insulation layer can completely cover the root of the winding lead, thereby eliminating weak points in the insulation layer. Furthermore, the sheds in the insulation layer improve creepage performance and anti-pollution capability, ensuring the long-term safe operation of the dry-type transformer. Additionally, the sheds in this invention are integrally injection molded with the insulation substrate, and the dimensions of each shed are consistent, ensuring the stability of creepage performance. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the winding leads of a dry-type transformer provided in a specific embodiment of the present invention;

[0028] Figure 2 This is a flowchart illustrating a method for manufacturing the winding leads of a dry-type transformer according to a specific embodiment of the present invention.

[0029] The annotations in the attached figures are explained as follows:

[0030] 1. Dry-type transformer; 2. Copper busbar; 3. Insulation layer. Detailed Implementation

[0031] This invention discloses a dry-type transformer winding lead, which features highly efficient insulation layer fabrication, absence of weak insulation points, and excellent creepage resistance. The invention also discloses a casting mold tube and a method for manufacturing the dry-type transformer winding lead.

[0032] 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 a part of the embodiments of the present invention, and not all of the 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.

[0033] This invention discloses a dry-type transformer winding lead, including a winding lead body and an insulating layer covering the winding lead body. The insulating layer in this invention is formed by injection molding. The root of the insulating layer covers the root of the winding lead body. Specifically, the insulating layer includes an insulating substrate and sheds. The insulating substrate covers the winding lead body. The sheds are integrally formed on the insulating substrate. There are multiple sheds, which are spaced apart along the axial direction of the insulating substrate.

[0034] In this invention, the insulation layer is injection molded, which is more efficient than the traditional method of wrapping insulation tape. Secondly, the space at the root of the winding lead body is sufficient to accommodate the root of the injection molding tube, thus the root of the injection-molded insulation layer can completely cover the root of the winding lead, eliminating weak points in the insulation layer. Furthermore, the sheds in the insulation layer improve creepage performance and anti-pollution capability, ensuring the long-term safe operation of the dry-type transformer. Additionally, the sheds in this invention are integrally injection molded with the insulation substrate, and the dimensions of each shed are consistent, ensuring the stability of creepage performance.

[0035] In this invention, the insulating layer extends towards the root of the winding lead body and covers the root of the winding lead body. On the other hand, the insulating layer extends towards the end of the winding lead body, passing over the welding point between the winding lead body and the copper busbar, and reaching the copper busbar. Thus, the welding point between the winding lead body and the copper busbar is covered by the insulating layer, further eliminating weak points in the insulation.

[0036] The distance between two adjacent skirts in the insulation layer is 20-30mm. The skirt depth is 5-8mm. The creepage distance is ≥31mm / kV. The skirt depth is the length of the skirt protruding outward relative to the insulating substrate, or the radial horizontal length from the outer wall of the insulating substrate to the outermost edge of the skirt. The skirt spacing and skirt depth in this invention ensure both sufficient creepage distance and prevent excessive skirt depth from accumulating dirt.

[0037] In a specific embodiment of the present invention, the insulating layer is preferably made of nano-silica-modified room-temperature curing epoxy resin. The nano-silica-modified room-temperature curing epoxy resin contains 5%–8% by mass of nano-silica, and the nano-silica particle size is 20–50 nm. The epoxy resin in the nano-silica-modified room-temperature curing epoxy resin is a two-component room-temperature curing epoxy resin with an epoxy value of 0.45–0.55, an amine curing agent, and a mass ratio of A (epoxy main agent): B (amine curing agent) = 3:1. The viscosity at 25°C is 800–1200 mPa·s.

[0038] Nano-silica-modified room-temperature curing epoxy resin exhibits excellent flowability. Combined with a vacuum degassing process, it can fully penetrate and cover the root of the winding leads, completely eliminating air bubbles and weak points in the insulation. The cured insulation layer boasts high insulation strength, effectively preventing breakdown faults. Furthermore, the nano-silica in the nano-silica-modified room-temperature curing epoxy resin significantly enhances its resistance to tracking, cracking, and weathering, thereby reducing subsequent maintenance costs.

[0039] This invention also discloses a casting mold tube, comprising a tube body for coaxially sleeved on the outside of the winding lead body of a dry-type transformer. The casting mold tube is sleeved on the winding lead body, and the inner wall of the casting mold tube and the outer wall of the winding lead body form a casting cavity. This casting cavity is used for the injection of nano-silica-modified room-temperature curing epoxy resin to form an insulating layer. A key feature of the casting mold tube of this invention is that an annular groove is provided on the inner wall of the tube body. The annular groove is axially aligned with the tube body and serves as a skirt for forming the insulating layer. Multiple annular grooves are evenly spaced along the axial direction of the tube body.

[0040] Because the inner wall of the injection molding tube has an annular groove, when nano-silica-modified room-temperature curing epoxy resin is injected into the injection cavity formed by the inner wall of the injection molding tube and the outer wall of the winding lead body, the nano-silica-modified room-temperature curing epoxy resin not only fills the inner cavity of the tube but also fills the annular groove. This allows the skirt and the insulating substrate to be integrally injection molded. Since the annular grooves are of uniform size, the skirts are also of uniform and regular size, thereby improving creepage performance.

[0041] The material of the injection molding tube body is preferably a flexible material, which allows for expansion and contraction, thereby improving the flexibility of the tube assembly. Specifically, the injection molding tube body is a PE plastic tube.

[0042] The casting mold tube is longer than the winding lead body, with its root located outside the root of the winding lead body and its end outside the copper busbar. Before casting, the casting mold tube is fitted over the winding lead body. Then, the casting mold tube is compressed from its end towards its root, exposing the end of the winding lead body for welding to the copper busbar. The compression is then released, allowing the casting mold tube to return to its natural state, with its end now at the copper busbar, encompassing the welded area between the winding lead body and the copper busbar. This creates an insulating layer at the welded area between the winding lead body and the copper busbar after casting, eliminating weak points in the insulation.

[0043] This invention also discloses a method for manufacturing winding leads of a dry-type transformer, using the aforementioned injection molding tube, comprising the following steps:

[0044] S1: Select a casting mold tube. The length of the casting mold tube is longer than the length of the winding lead body by a first preset value, and the inner diameter of the casting mold tube is larger than the outer diameter of the winding lead body by a second preset value.

[0045] Specifically, the length of the injection molding tube is 15mm longer than the length of the winding lead body. The inner diameter of the injection molding tube is 15-20mm larger than the outer diameter of the winding lead body, and the wall thickness is 2-3mm. The groove depth of the annular groove corresponds to the depth of the skirt, which is 5-8mm. The spacing between two adjacent annular grooves corresponds to the skirt spacing, which is 20-30mm.

[0046] S2: Place the injection molding tube over the winding lead body, so that the winding lead body is centered inside the injection molding tube.

[0047] S3: Compress the casting mold tube from its end to its root to expose the end of the winding lead body. Weld the end of the winding lead body to the copper busbar. After welding, allow the casting mold tube to return to its natural state, with the welded area between the winding lead body and the copper busbar located inside the casting mold tube. In this step, the casting mold tube is fitted first, and then the copper busbar is welded. This not only reduces the difficulty of fitting but also protects the welded area between the copper busbar and the end of the winding lead body.

[0048] S4: Seal the gap between the root of the injection molding tube and the root of the winding lead body.

[0049] In step S4, room-temperature curing epoxy resin is used to seal the gap between the root of the injection molding tube and the root of the winding lead body. After the room-temperature curing epoxy resin cures, it forms an insulating part.

[0050] S5: Move the dry-type transformer into the vacuum tank. The end opening of the injection mold tube is the injection port, and the injection port is sealed to the injection pipeline of the injection device.

[0051] S6: Evacuate the vacuum tank and inject nano-silica modified room temperature curing epoxy resin into the injection mold tube under preset negative pressure conditions through the injection device. After injection, maintain the preset negative pressure for a preset time.

[0052] In step S6, the vacuum tank is evacuated to a vacuum level of -0.08 to -0.1 MPa. After filling, the negative pressure is maintained for 10 minutes for vacuum degassing to ensure that the nano-silica modified room-temperature curing epoxy resin fills the inner cavity of the filling mold tube and completely covers the winding lead body.

[0053] S7: First preset time for curing at room temperature, second preset time for curing after heating.

[0054] In step S7, specifically, the product is cured at room temperature for 24 hours at 20℃-25℃, and then cured at 38℃-42℃ for 4 hours.

[0055] S8: After the nano-silica modified room-temperature curing epoxy resin is cured, the injection mold tube is removed to obtain an integrally molded insulation layer with an equidistant annular umbrella skirt array on the outer surface and a dense, bubble-free interior, thus completing the insulation treatment of the winding lead body.

[0056] Example 1

[0057] The manufacturing method of a winding lead for a 35 / 10kV dual high-voltage transformer with different turns ratio is as follows:

[0058] S1: Select a casting mold tube with an inner diameter of 30mm (fitting a 15mm outer diameter winding lead body), a wall thickness of 2.5mm, and a pre-made annular groove on the inner wall with a spacing of 25mm, a depth of 6mm, and a circular cross-section.

[0059] S2: Place the injection molding tube over the winding lead body, so that the winding lead body is centered inside the injection molding tube.

[0060] S3: Compress the injection mold tube from the end to the root of the injection mold tube to expose the end of the winding lead body, and weld the end of the 35kV side winding lead body to the copper busbar to ensure reliable electrical connection.

[0061] S4: Seal the gap between the root of the injection molding tube and the root of the winding lead body.

[0062] S5: Move the dry-type transformer into the vacuum tank. The end opening of the injection mold tube is the injection port, and the injection port is sealed to the injection pipeline of the injection device.

[0063] S6: Evacuate the vacuum tank and inject nano-silica modified room temperature curing epoxy resin into the injection mold tube under preset negative pressure conditions through the injection device. After injection, maintain the preset negative pressure for a preset time.

[0064] A two-component room-temperature curing epoxy resin with a ratio of A:B = 3:1 was modified with nano-silica, and 6% nano-silica (particle size 30nm) was added and stirred evenly. The nano-silica modified room-temperature curing epoxy resin was poured under a vacuum of -0.09MPa, and the negative pressure was maintained for 10 minutes after pouring to degas the resin.

[0065] S7: Cur at room temperature for 24 hours at 20℃-25℃, then cure at 40℃ for 4 hours.

[0066] After curing, the injection molding tube is peeled off, and seven continuous equidistant umbrella skirts are formed on the outer surface of the insulating substrate, covering the winding lead body and the root of the copper busbar, thus completing the insulation treatment.

[0067] Testing showed that the winding leads had a power frequency withstand voltage of 95kV without any breakdown or flashover. The insulation at the root of the winding leads was intact and free of air bubbles. The creepage distance of the sheds was 35mm / kV, demonstrating excellent resistance to pollution. Long-term operation showed no cracking or aging, indicating high reliability.

[0068] Example 2

[0069] A 20 / 6kV dual high-voltage transformer winding lead is manufactured in a manner basically the same as in Example 1, except that a casting mold tube with an inner diameter of 20mm is selected. The amount of nano-silica added to the room-temperature curing epoxy resin modified with nano-silica is 5%, and the number of umbrella skirts is 5, with a spacing of 20mm and a depth of 5mm.

[0070] The structure has been tested and meets the 20kV withstand voltage requirement, with a creepage distance of 32mm / kV. It significantly improves efficiency and reliability and is suitable for insulation treatment of the winding lead body of medium-voltage dual high-voltage ratio dry-type transformers.

[0071] In the above context, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0072] The various embodiments described in this specification are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. 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.

[0073] Finally, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

Claims

1. A dry-type transformer winding lead, comprising a winding lead body and an insulating layer covering the winding lead body, characterized in that, The insulating layer is formed by injection molding, and the root of the insulating layer covers the root of the winding lead body; The insulating layer includes an insulating substrate and a skirt integrally formed on the insulating substrate, wherein the skirt is a plurality of skirts arranged along the axial direction of the insulating substrate.

2. The dry-type transformer winding leads according to claim 1, characterized in that, The end of the winding lead body is welded to the copper busbar, and the welding part between the winding lead body and the copper busbar is covered by the insulating layer.

3. The dry-type transformer winding leads according to claim 1, characterized in that, The distance between two adjacent umbrella skirts is 20-30mm; the depth of the umbrella skirt is 5-8mm.

4. The dry-type transformer winding leads according to claim 1, characterized in that, The insulating layer is made of nano-silica modified room-temperature curing epoxy resin.

5. A casting mold tube, comprising a tube body, the tube body being coaxially sleeved on the outside of the winding lead body of a dry-type transformer, the inner wall of the tube body and the outer wall of the winding lead body forming a casting cavity, the casting cavity being used to form an insulating layer, the insulating layer being the insulating layer as described in claim 1, characterized in that... The inner wall of the tube is provided with an annular groove, which is used to form the umbrella skirt. There are multiple annular grooves, which are arranged at intervals along the axial direction of the tube.

6. The injection molding tube according to claim 5, characterized in that, The tube is a flexible tube.

7. The injection molding tube according to claim 6, characterized in that, One end of the tube may be located outside the root of the winding lead body, while the other end is located outside the copper busbar. The tube encloses the welding part between the winding lead body and the copper busbar.

8. A method for manufacturing winding leads of a dry-type transformer, characterized in that, Using the injection molding tube as described in claim 5, comprising: S1: Select the injection molding tube, wherein the length of the injection molding tube is longer than the length of the winding lead body by a first preset value, and the inner diameter of the injection molding tube is larger than the outer diameter of the winding lead body by a second preset value. S2: The injection molding tube is sleeved over the winding lead body; S3: Compress the injection mold tube from the end to the root of the injection mold tube to expose the end of the winding lead body, weld the end of the winding lead body to the copper busbar, and after welding, restore the injection mold tube to its natural state. S4: Seal the gap between the root of the injection mold tube and the root of the winding lead body; S5: Move the dry-type transformer into the vacuum tank, with the end opening of the injection mold tube serving as the injection port, and seal the injection port to the injection pipeline of the injection device. S6: Evacuate the vacuum tank and inject nano-silica modified room temperature curing epoxy resin into the injection mold tube under preset negative pressure conditions through the injection device. After injection, maintain the preset negative pressure for a preset time. S7: First preset time for curing at room temperature, second preset time for curing after heating; S8: Remove the injection mold tube.

9. The method for manufacturing the winding leads of a dry-type transformer according to claim 8, characterized in that, Specifically, S4 involves using room-temperature curing epoxy resin to seal the gap between the root of the injection mold tube and the root of the winding lead body.

10. The method for manufacturing the winding leads of a dry-type transformer according to claim 8, characterized in that, Specifically, step S7 involves curing at room temperature (20℃-25℃) for 24 hours, followed by curing at 38℃-42℃ for 4 hours.

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