Top connecting pipe structure of large oil-immersed transformer of nuclear power plant
By designing a top joint pipe structure of a large oil-immersed transformer in nuclear power plant, including insulating plates, bolts and insulating sleeves, a complete insulating partition of the flange surface of the two connecting pipes is realized, which solves the problem of hot spots on the top of the main transformer and improves the safe and stable operation of the main power supply.
Patent Information
- Application Number
- CN202421823154.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-30
- Publication Date
- 2025-05-27
- Estimated Expiration
- 2034-07-30
AI Technical Summary
Due to design defects, the top connecting pipe structure of large oil-immersed transformers in nuclear power plants has magnetic leakage and complex current loops, resulting in hot spots on the top of the main transformer, which increases the risk of flange leakage and oil overheating, affecting the safe operation of the main transformer.
A top coupling structure of a large oil-immersed transformer in nuclear power plant, including a first pipeline, a second pipeline and a fastening component, is designed to achieve a complete insulating partition of the flange surface of the two coupling pipes through components such as insulating plates, bolts, nuts and insulating sleeves, and block the current loop between the coupling pipes.
It completely solves the major hidden dangers of hot spots on the top of the main transformer caused by design defects, improves the safe and stable operation of the main power supply, and provides an important guarantee for the improvement of the insulation strength between the oil-connected pipe flanges on the top of the main transformer.
Smart Images
Figure CN222914538U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of nuclear power, in particular to a top connecting pipe structure of a large oil-immersed transformer in a nuclear power plant. Background Art
[0002] During the full-power operation of a certain nuclear power unit, infrared thermal imaging detection was carried out and it was found that there was local overheating at the oil connecting pipe flange near the low-voltage bin at the top of the main transformer. The hot spot temperature reached 150°C, the average temperature of the flange reached 97°C, and the average temperature of the exhaust pipe flange with a smaller diameter reached 106°C. The gasket material at the oil connecting pipe connection flange is nitrile rubber, and the maximum usable temperature is 105°C. The overheating temperature of the flange has approached the limit temperature of the gasket, accelerating the aging of the gasket and increasing the risk of oil leakage at the top flange of the main transformer and local oil overheating, resulting in an increased risk of oil leakage at the main transformer flange affecting the safe operation of the main transformer. On-site, by measuring the current of the oil connecting pipe and comparing it with the flange temperature, it was analyzed that a current loop was formed due to the damage of the paint film on the oil connecting pipe, and a large circulating current was generated under the action of the induced electromotive force at the low-voltage elevation seat.
[0003] The reason for the hot spot during the operation of the top of the main transformer is that there is a design defect in the insulation of the top flange of the main transformer. There is a large leakage magnetic field at the top of the main transformer (especially near the low-voltage bin of the main transformer). The oil connecting pipes at the top of the main transformer form a complex circuit. Under the action of electromagnetic induction, a circulating current is formed in the oil connecting pipe circuit at the top of the main transformer (during the inspection under the full-power state of the unit, it was found that the maximum current of the connecting pipe reached 300A), resulting in heating. Content of the Utility Model
[0004] The technical problem to be solved by the utility model is to provide a top connecting pipe structure of a large oil-immersed transformer in a nuclear power plant.
[0005] The technical solution adopted by the utility model to solve its technical problem is to construct a top connecting pipe structure of a large oil-immersed transformer in a nuclear power plant, including a first pipe, a second pipe, and a fastening component;
[0006] One end of the axial direction of the first pipe is provided with a first flange, and a plurality of first connection holes are provided on the first flange; one end of the axial direction of the second pipe is provided with a second flange, the second flange is arranged opposite to the first flange, a plurality of second connection holes are provided on the second flange, and the second connection holes are arranged opposite to the first connection holes;
[0007] The fastening component includes an insulating plate, a bolt, a nut, a first insulating sleeve, and a second insulating sleeve; the insulating plate is installed between the first flange and the second flange, a through cavity is provided in the middle of the insulating plate, and a plurality of third connection holes are further provided on the insulating plate, and the third connection holes are arranged opposite to the first connection holes and the second connection holes;
[0008] The bolt includes a nut and a threaded portion coaxially arranged with the nut. An insulating paper is wound around the outer periphery of the threaded portion. The threaded portion passes through the first connection hole, the third connection hole, and the second connection hole, and the nut is fastened on the portion of the threaded portion protruding from the second connection hole;
[0009] The first insulating sleeve is used to sleeve the portion of the threaded portion between the nut and the end wall of the first flange, and the second insulating sleeve is used to sleeve the portion of the threaded portion between the nut and the end wall of the second flange.
[0010] In some embodiments, a sealing groove is provided on the end wall of the first flange facing the second flange and / or the end wall of the second flange facing the first flange;
[0011] The top pipe connection structure of the large oil-immersed transformer in the nuclear power plant further includes an insulating gasket provided in the sealing groove.
[0012] In some embodiments, the insulating gasket includes an acrylate gasket.
[0013] In some embodiments, the thickness of the insulating gasket is 9 mm - 11 mm.
[0014] In some embodiments, the inner diameter dimension of the through cavity is 4 mm larger than the outer diameter dimension of the insulating gasket.
[0015] In some embodiments, the insulating board includes an epoxy glass cloth board.
[0016] In some embodiments, the thickness of the insulating board is 1 mm.
[0017] In some embodiments, the thicknesses of the first insulating sleeve and the second insulating sleeve are both 4 mm.
[0018] In some embodiments, the inner diameter of the third connection hole is 1 mm larger than the outer diameter of the threaded portion.
[0019] In some embodiments, the insulating paper includes NOMEX insulating paper.
[0020] Implementing the present utility model has the following beneficial effects: The top pipe connection structure of the large oil-immersed transformer in the nuclear power plant can achieve complete insulation isolation between the two pipe connection flange surfaces (such as the first flange and the second flange), completely block the current loop between the pipes, and completely solve the major hidden danger of hot spots existing at the top of the main transformer during operation caused by design defects, providing an important guarantee for the safe and stable operation of the main power supply. Description of the Drawings
[0021] To more clearly illustrate the technical solution of the present utility model, the following will further explain the present utility model in conjunction with the accompanying drawings and embodiments. It should be understood that the following drawings only show some embodiments of the present utility model, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings. In the drawings:
[0022] Figure 1 is a schematic structural diagram of the top connecting pipe structure of a large oil-immersed transformer in a nuclear power plant in some embodiments of the present utility model;
[0023] Figure 2 is a partial structural schematic diagram of the top connecting pipe structure of a large oil-immersed transformer in a nuclear power plant in some embodiments of the present utility model;
[0024] Figure 3 is a schematic structural diagram of an insulating board in some embodiments of the present utility model. Detailed implementation manners
[0025] To have a clearer understanding of the technical features, objectives, and effects of the present utility model, the detailed implementation manners of the present utility model will now be described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientation or positional relationships indicated by "front", "rear", "upper", "lower", "left", "right", "longitudinal", "transverse", "vertical", "horizontal", "top", "bottom", "inner", "outer", "head", "tail", etc. are based on the orientation or positional relationships shown in the drawings and are constructed and operated in a specific orientation, and are only for the convenience of describing the technical solution, rather than indicating that the indicated device or element must have a specific orientation. Therefore, it should not be construed as a limitation of the present utility model.
[0026] It should also be noted that, unless otherwise clearly specified and defined, terms such as "installation", "connection", "linkage", "fixation", "setting" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. When a component is referred to as "on" or "under" another component, the component can be "directly" or "indirectly" located above the other component, or there may also be one or more intermediate components. Terms such as "first", "second", "third", etc. are only for the convenience of describing the technical solution of the present invention, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.
[0027] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures, technologies, etc. are presented in order to thoroughly understand the embodiments of the present utility model. However, those skilled in the art should clearly understand that the present utility model can also be implemented in other embodiments without these specific details. In other cases, the detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present utility model.
[0028] Referring to Figures 1 to 3 , the present utility model shows a top connecting pipe structure of a large oil-immersed transformer in a nuclear power plant, which includes a first pipe 10, a second pipe 20, and a fastening assembly 30.
[0029] One end of the axial direction of the first pipe 10 is provided with a first flange 11, and a plurality of first connection holes 12 are provided on the first flange 11; one end of the axial direction of the second pipe 20 is provided with a second flange 21, the second flange 21 is arranged opposite to the first flange 11, a plurality of second connection holes 22 are provided on the second flange 21, and the second connection holes 22 are arranged opposite to the first connection holes 12. The types of the first flange 11 and the second flange 21 can include but are not limited to circular small flanges, square small flanges, butterfly valve flanges, and square large flanges.
[0030] The fastening assembly 30 is used for insulating connection between the first flange 11 and the second flange 21. The fastening assembly 30 may include an insulating plate 31, a bolt 32, a nut 33, a first insulating sleeve 34, and a second insulating sleeve 35. The insulating plate 31 is installed between the first flange 11 and the second flange 21. A through cavity 311 is provided in the middle of the insulating plate 31. The insulating plate 31 is further provided with a plurality of third connection holes 312, and the third connection holes 312 are disposed opposite to the first connection holes 12 and the second connection holes 22.
[0031] The bolt 32 includes a nut 321 and a threaded portion 322 coaxially arranged with the nut 321. An insulating paper 323 is wound around the outer periphery of the threaded portion 322. The threaded portion 322 passes through the first connection hole 12, the third connection hole 312, and the second connection hole 22, and the nut 33 is fastened to the portion of the threaded portion 322 protruding from the second connection hole 22.
[0032] The first insulating sleeve 34 is generally annular, and the first insulating sleeve 34 is used for sleeving on the portion of the threaded portion 322 between the nut 321 and the end wall of the first flange 11. The second insulating sleeve 35 is generally annular, and the second insulating sleeve 35 is used for sleeving on the portion of the threaded portion 322 between the nut 33 and the end wall of the second flange 21.
[0033] Combined Figure 1 and Figure 2 , in some embodiments, a sealing groove A is provided on the end wall of the first flange 11 facing the second flange 21 and / or the end wall of the second flange 21 facing the first flange 11. For example, a sealing groove A is provided on the end wall of the first flange 11 facing the second flange 21. Or, a sealing groove A is provided on the end wall of the second flange 21 facing the first flange 11. Or, sealing grooves A are provided on both the end wall of the first flange 11 facing the second flange 21 and the end wall of the second flange 21 facing the first flange 11, and the sealing groove A is generally in an annular structure.
[0034] Preferably, the top connecting pipe structure of the large oil-immersed transformer in the nuclear power plant further includes an insulating gasket 40 disposed in the sealing groove A. The insulating gasket 40 is generally annular, and the insulating gasket 40 is installed in the sealing groove A.
[0035] In some embodiments, the insulating gasket 40 includes an acrylate gasket, that is, the insulating gasket 40 can be made of acrylate material.
[0036] In some embodiments, the thickness of the insulating gasket 40 is 9 mm - 11 mm. Preferably, the thickness of the insulating gasket 40 is 10 mm. It can be understood that the thickness of the insulating gasket 40 in the related art is 8 mm, and the insulation ability is relatively poor. While the thickness of the insulating gasket 40 in this application is 9 mm - 11 mm, which can enhance the insulation and sealing performance.
[0037] In some embodiments, the inner diameter of the through cavity 311 of the insulating plate 31 is 4 mm larger than the outer diameter of the insulating gasket 40, ensuring that the compression surface of the insulating gasket 40 is the flange plane and guaranteeing the sealing effect. Preferably, the outer diameter of the insulating gasket 40 can be 116 mm, and the inner diameter of the insulating gasket 40 can be 100 mm. The through cavity 311 can be circular, and its inner diameter can be 104 mm.
[0038] In some embodiments, the insulating plate 31 includes an epoxy glass cloth board. The overall shape of the insulating plate 31 can be circular plate-shaped or square plate-shaped. The insulating plate 31 can be selected as an epoxy glass cloth board, that is, an epoxy glass EPGC insulating board. The epoxy glass cloth board has excellent insulation performance, mechanical strength, good impact resistance, and excellent flatness. The epoxy glass cloth board also has a flame retardant effect, which can improve the safety of the equipment.
[0039] Preferably, the thickness of the insulating plate 31 is 1 mm. Of course, the thickness of the insulating plate 31 can be 1 mm or 2 mm, which can be selected and set according to actual needs and will not be specifically limited here.
[0040] In some embodiments, the thicknesses of the first insulating sleeve 34 and the second insulating sleeve 35 are both 4 mm. The first insulating sleeve 34 and the second insulating sleeve 35 can be selected as epoxy glass cloth boards, that is, epoxy glass EPGC insulating boards.
[0041] In some embodiments, the inner diameter of the third connection hole 312 is 1 mm larger than the outer diameter of the threaded portion 322, so that at least two layers of insulating paper 323 can be wound around the threaded portion 322. The sum of the axial dimensions of the first connection hole 12, the axial dimension of the second connection hole 22, and the axial dimension of the third connection hole 312 is less than the winding length of the insulating paper 323 on the threaded portion 322 to improve insulation. Preferably, the insulating paper 323 includes NOMEX insulating paper. NOMEX insulating paper is made of two forms of aromatic polyamide polymers. The mixture of its fibrous bonding particles and short fibers forms a very stable molecular structure. This structure endows NOMEX insulating paper with high electrical insulation performance and mechanical strength. NOMEX insulating paper can withstand a short-term voltage field strength of 18 - 40 KV / mm and does not require additional varnish or resin treatment, which makes it perform excellently in high-voltage applications. NOMEX insulating paper can be continuously used at a temperature of up to 220 °C for ten years without losing its effectiveness, ensuring the reliability and safety of the equipment during long-term operation.
[0042] Understandably, the top pipe connection structure of the large oil-immersed transformer in a nuclear power plant can achieve complete insulation isolation between the two pipe connection flange surfaces (such as the first flange 11 and the second flange 21), completely blocking the current loop between the pipes, and thoroughly solving the major hidden danger of hot spots existing at the top of the main transformer during operation caused by design defects, providing an important guarantee for the safe and stable operation of the main power supply. The top pipe connection structure of the large oil-immersed transformer in a nuclear power plant fills the technical gap in achieving insulation upgrade for the same type of 500KV main transformer at home and abroad without changing the oil pipe connection structure at the top of the main transformer, avoiding the complex situation of completely replacing the oil pipes at the top of the main transformer, greatly saving the maintenance period and cost, mastering the core technology of pipe insulation optimization, thoroughly solving the design defects, and improving the insulation strength between the flanges of the oil pipes at the top of the main transformer.
[0043] Understandably, the above embodiments only express the preferred implementation modes of the present utility model, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present utility model; it should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, the above technical features can be freely combined, and several deformations and improvements can also be made, and these all belong to the protection scope of the present utility model; therefore, all equivalent transformations and modifications made to the scope of the claims of the present utility model shall fall within the scope covered by the claims of the present utility model.
Claims
1. A top pipe connection structure for a large oil-immersed transformer in a nuclear power plant, characterized in that: It comprises a first pipe (10), a second pipe (20) and a fastening assembly (30); A first flange (11) is provided at one axial end of the first pipe (10), and a plurality of first connection holes (12) are provided on the first flange (11); a second flange (21) is provided at one axial end of the second pipe (20), and the second flange (21) is arranged opposite to the first flange (11), and a plurality of second connection holes (22) are provided on the second flange (21), and the second connection holes (22) are arranged opposite to the first connection holes (12); The fastening assembly (30) comprises an insulating plate (31), a bolt (32), a nut (33), a first insulating sleeve (34), and a second insulating sleeve (35); the insulating plate (31) is installed between the first flange (11) and the second flange (21); a through cavity (311) is provided in the middle of the insulating plate (31); a plurality of third connecting holes (312) are also provided on the insulating plate (31); the third connecting holes (312) are arranged opposite to the first connecting hole (12) and the second connecting hole (22); The bolt (32) comprises a nut (321) and a threaded portion (322) coaxially arranged with the nut (321); an insulating paper (323) is arranged around the outer circumference of the threaded portion (322); the threaded portion (322) is passed through the first connection hole (12), the third connection hole (312) and the second connection hole (22); and the nut (33) is fastened to a portion of the threaded portion (322) protruding from the second connection hole (22); The first insulating sleeve (34) is used to be sleeved on the portion of the threaded portion (322) located between the nut (321) and the end wall of the first flange (11), and the second insulating sleeve (35) is used to be sleeved on the portion of the threaded portion (322) located between the nut (33) and the end wall of the second flange (21).
2. The top pipe connection structure of a large oil-immersed transformer in a nuclear power plant according to claim 1, characterized in that: A sealing groove (A) is provided on the end wall of the first flange (11) facing the second flange (21) and / or on the end wall of the second flange (21) facing the first flange (11); The top connecting pipe structure of a large oil-immersed transformer in a nuclear power plant further comprises an insulating sealing gasket (40) arranged in the sealing groove (A).
3. The top pipe connection structure of a large oil-immersed transformer in a nuclear power plant according to claim 2, characterized in that: The insulating sealing gasket (40) comprises an acrylic sealing gasket.
4. The top pipe connection structure of a large oil-immersed transformer in a nuclear power plant according to claim 2, characterized in that: The thickness of the insulating sealing pad (40) is 9 mm-11 mm.
5. The top pipe connection structure of a large oil-immersed transformer in a nuclear power plant according to claim 2, characterized in that: The inner diameter of the through cavity (311) is 4 mm larger than the outer diameter of the insulating sealing pad (40).
6. The top coupling structure of a large oil-immersed transformer in a nuclear power plant according to claim 1, characterized in that: The insulating board (31) comprises an epoxy glass cloth board.
7. The top pipe connection structure of a large oil-immersed transformer in a nuclear power plant according to claim 1, characterized in that: The thickness of the insulating plate (31) is 1 mm.
8. The top pipe connection structure of a large oil-immersed transformer in a nuclear power plant according to claim 1, characterized in that: The thickness of the first insulating sleeve (34) and the second insulating sleeve (35) are both 4 mm.
9. The top pipe connection structure of a large oil-immersed transformer in a nuclear power plant according to claim 1, characterized in that: The inner diameter of the third connection hole (312) is 1 mm larger than the outer diameter of the threaded portion (322).
10. The top pipe connection structure of a large oil-immersed transformer in a nuclear power plant according to claim 1, characterized in that: The insulating paper (323) comprises NOMEX insulating paper.