Air breakdown prevention structure of dry-type transformer and dry-type transformer

Abstract

The invention discloses an air breakdown prevention structure of a dry-type transformer and the dry-type transformer, the air breakdown prevention structure comprises an annular high-voltage winding and an annular low-voltage winding, the high-voltage winding and the low-voltage winding are encapsulated by epoxy resin casting, the high-voltage winding is sleeved outside the low-voltage winding, and the low-voltage winding is sleeved outside the high-voltage winding. The high-voltage winding comprises a first insulating layer arranged on the inner surface, the low-voltage winding comprises a second insulating layer arranged on the outer surface, an air interlayer is arranged between the first insulating layer and the second insulating layer, and notches are formed in the upper end and the lower end of the first insulating layer and / or the second insulating layer. The notches are formed in the upper end and the lower end of the insulating layer, so that the air distance of the end area is increased, the local electric field intensity is reduced, magnetic field distortion is eliminated, the air breakdown phenomenon is avoided fundamentally, and stable and safe operation of the transformer is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of power supply line facilities technology, and in particular to an air breakdown protection structure for a dry-type transformer and the dry-type transformer itself. Background Technology

[0002] Dry-type transformers, as core equipment in power supply line facilities, have been widely used in power transmission and transformation systems due to their significant advantages such as being oil-free, fireproof, having a long service life, being energy-saving and low-noise, easy to maintain, and safe and reliable. They have become a key component in ensuring stable power transmission. With the continuous improvement of voltage level requirements in power systems, the application scenarios of high-voltage dry-type transformers are increasing. However, the contradiction between electrical insulation performance and operational safety is becoming increasingly prominent.

[0003] In the actual operation of dry-type transformers, a core problem that urgently needs to be solved is the frequent occurrence of air breakdown, which leads to arcing and significant discharge noise. Existing dry-type transformers generally use epoxy resin as the insulating shell and winding encapsulation material. Although epoxy resin has certain insulating properties, it inherently possesses flammable and explosive characteristics. Once arcing occurs in the windings due to air breakdown, it can easily ignite or explode the epoxy resin shell, leading to decreased equipment performance, shortened service life, and potentially equipment failure, posing a serious threat to the overall safety of power supply line facilities.

[0004] To address the insulation and safety issues of dry-type transformers, existing technologies have proposed various improvement schemes. For example, patent document CN111383829A discloses a dry-type transformer that enhances the electrical insulation strength between the low-voltage and high-voltage windings by adding an additional insulation layer inside the high-voltage winding. However, this scheme only focuses on the overall insulation performance between windings and does not address the issue of air breakdown in the windings. Patent document CN111933423A discloses a single-phase direct-buried dry-type transformer that improves insulation and sealing performance through epoxy resin integral casting and shielding layer design. However, its improvement focuses on the overall insulation structure and waterproof and corrosion-resistant performance of the windings, and it also fails to solve the problem of air breakdown in the windings.

[0005] In summary, existing technologies cannot solve the problem of air breakdown in dry-type transformers, resulting in the operational safety of dry-type transformers failing to meet the high reliability requirements of power supply line facilities. Summary of the Invention

[0006] The present invention aims to address how to reduce the risk of air breakdown and related safety hazards in dry-type transformers, so as to ensure the stable and safe operation of transformers.

[0007] To solve the above-mentioned technical problems, the first aspect of the present invention provides an air breakdown protection structure for a dry-type transformer, comprising an annular high-voltage winding and a low-voltage winding, wherein the high-voltage winding and the low-voltage winding are encapsulated by epoxy resin casting, the high-voltage winding is sleeved outside the low-voltage winding, the high-voltage winding includes a first insulating layer disposed on the inner surface, the low-voltage winding includes a second insulating layer disposed on the outer surface, an air gap is formed between the first insulating layer and the second insulating layer, and notches are provided at the upper and lower ends of the first insulating layer and / or the second insulating layer.

[0008] Studies have shown that air breakdown mainly occurs at the upper and lower ends of the high-voltage and low-voltage windings in dry-type transformers because of significant magnetic field distortion at the winding ends. This invention introduces gaps at both ends of the insulation layer, thereby increasing the air distance in the end region, reducing the local electric field strength, eliminating magnetic field distortion, and fundamentally preventing air breakdown, thus ensuring the stable and safe operation of the transformer.

[0009] Furthermore, a silicone rubber layer is provided on the surface of the notch. The silicone rubber layer on the notch surface further improves the protection against air breakdown and effectively prevents the arc light generated by air breakdown from igniting the insulation layer, thus ensuring the safe operation of the transformer.

[0010] Furthermore, the surface of the notch is an inclined plane that gradually increases in size towards the end opening, and the cross-sectional shape of the notch is a right-angled triangle. By setting the notch cross-section to a right-angled triangle and the surface to be an inclined plane that gradually increases in size towards the end opening, this structure makes the air distance in the notch region gradually distributed along the winding axis, which can more uniformly reduce the electric field intensity in the end magnetic field distortion region, effectively suppress local electric field concentration, and reduce the probability of air breakdown.

[0011] Furthermore, the dimensions of the cross-sectional triangle of the notch satisfy the following relationships: T≥a≥3 / 4T, 3D≥h≥D, where a is the base length of the cross-sectional triangle of the notch, h is the height of the cross-sectional triangle of the notch, T is the thickness of the insulation layer corresponding to the notch, and D is the width of the air gap. The dimensions of the notch are confirmed by theoretical calculations and experiments. The above-mentioned dimension design ensures that the notch fully covers the magnetic field distortion region at the winding end, maximizes the air distance in this region, and essentially eliminates the air breakdown phenomenon.

[0012] Furthermore, the surface of the notch is parallel to the inner surface of the first insulating layer, and the cross-sectional shape of the notch is rectangular. The rectangular notch structure facilitates processing and manufacturing, reduces production difficulty, ensures that the notch accurately corresponds to the magnetic field distortion region at the winding end, stably increases the air distance, and plays a role in preventing air breakdown.

[0013] Furthermore, the dimensions of the rectangular cross-section of the notch satisfy the following relationships: T≥W≥3 / 4T, 3D≥L≥D, where W is the width of the rectangular cross-section of the notch, L is the length of the rectangular cross-section of the notch, T is the thickness of the insulation layer corresponding to the notch, and D is the width of the air gap. The dimensions of the notch are confirmed by theoretical calculations and experiments to ensure that the notch covers the critical area of ​​magnetic field distortion at the winding end, thus guaranteeing the feasibility of the solution and the reliability of breakdown protection.

[0014] Furthermore, the thickness of the first and second insulating layers is 2-10 mm, and the thickness of the air gap is 20-85 mm. Limiting the insulation layer thickness ensures its structural strength and provides a reliable insulation barrier for the high and low voltage windings; the air gap provides sufficient insulation distance between the high and low voltage windings, and together with the gaps at the upper and lower ends of the insulation layer, forms a dual breakdown protection of basic insulation and gap-increasing distance, ensuring stable operation of the transformer in high-voltage scenarios.

[0015] Furthermore, the thickness of the silicone rubber layer is 0.1~1.5mm. Limiting the thickness of the silicone rubber layer provides sufficient insulation protection and fire-blocking capability, while not affecting the core breakdown protection function of increasing air gaps.

[0016] Furthermore, the first and second insulating layers are formed by epoxy resin casting or impregnation with a mesh-like glass fiber, and the silicone rubber layer is made of HTV silicone rubber or RTV silicone rubber. This insulating layer has high insulation strength and crack resistance, preventing cracking due to insecure curing after long-term operation, which could lead to insulation failure and air breakdown. Both types of silicone rubber possess high-temperature resistance, maintaining stable insulation performance in the high-temperature environment of transformer operation, preventing insulation protection failure due to silicone rubber aging, and extending the transformer's service life.

[0017] A second aspect of this invention provides a dry-type transformer, including the aforementioned air-breakdown protection structure. This enables the dry-type transformer to possess targeted air-breakdown protection capabilities at the product level, solving the problem of air breakdown at the winding ends and avoiding the combustion and explosion hazards arising from breakdown. Simultaneously, the improved structure is simple, requiring no significant modifications to other general transformer structures, facilitating structural upgrades of existing dry-type transformers, ensuring the overall stable and safe operation of the transformer, and meeting the reliability requirements of power supply line facilities.

[0018] In summary, the present invention has the following beneficial effects: (1) Accurately solve the air breakdown problem and ensure the stable operation of the transformer: By setting specific shaped gaps at the upper and lower ends of the winding (corresponding to the magnetic field distortion area), the air distance in the end area is increased in a targeted manner to reduce the local electric field intensity, avoiding the air breakdown phenomenon caused by magnetic field distortion and the accompanying arc discharge and discharge noise problems in traditional technology, eliminating the core hidden dangers that interfere with the normal operation of the transformer from the root, and ensuring the continuity and stability of its operation process.

[0019] (2) Enhance safety protection performance, reduce derivative risks and improve durability: The design of the silicone rubber layer on the notch surface not only helps to enhance the insulation effect to further suppress air breakdown, but also blocks the arc light generated by breakdown from igniting the insulation layer; combined with the insulation layer made of epoxy resin impregnated mesh glass fiber and high temperature resistant silicone rubber material, the insulation layer cracking and silicone rubber aging caused by insulation failure are avoided, effectively reducing derivative safety hazards such as combustion and explosion, and extending the overall service life of the transformer.

[0020] (3) Construct a collaborative protection system to meet the needs of high voltage scenarios: The insulation layer and the air gap form a synergy, and the gap is combined with the targeted optimization of the end distortion area to construct a dual protection system of basic insulation plus gap spacing, which breaks through the contradiction between insulation strength and high voltage scenario adaptability in traditional technology, and ensures that the transformer can still maintain reliable insulation performance in high voltage level operating environment, and meets the requirements of power supply line facilities for equipment withstand voltage stability.

[0021] (4) Simplified and improved structure, easy to upgrade and adapt and control cost: The air breakdown protection structure only requires notch design and material optimization for the insulation layer. It does not require major changes to the general core structure such as transformer core and winding. It can be directly integrated into the new dry transformer and is also easy to upgrade the existing transformer. It reduces the complexity and cost of structural adjustment and meets the needs of power supply line facilities for equipment upgrade convenience and economy. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a dry-type transformer in a specific embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the structure of a dry-type transformer in another specific embodiment of the present invention.

[0024] Figure 3 This is a cross-sectional view of a dry-type transformer using existing technology.

[0025] Figure 4 This is a cross-sectional view of a dry-type transformer in a specific embodiment of the present invention.

[0026] Figure 5 This is a cross-sectional view of the air breakdown protection structure of a dry-type transformer in a specific embodiment of the present invention.

[0027] Figure 6 This is a cross-sectional view of a dry-type transformer in another specific embodiment of the present invention.

[0028] Figure 7 This is a cross-sectional view of the air breakdown protection structure of a dry-type transformer in another specific embodiment of the present invention.

[0029] Figure 8 This is a cross-sectional view of the air breakdown protection structure of a dry-type transformer in another specific embodiment of the present invention.

[0030] Figure 9 This is a cross-sectional view of the air breakdown protection structure of a dry-type transformer in another specific embodiment of the present invention.

[0031] Explanation of reference numerals in the attached figures: 1-High voltage winding, 2-Low voltage winding, 3-Iron core, 4-Air gap, 5-First insulation layer, 6-Second insulation layer, 7-Notch, 8-Silicone rubber layer. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0033] It should be noted that similar symbols and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the figures of this invention, the dimensions of the structures have been adjusted for clarity and do not represent the actual product dimensions.

[0034] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "inner," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed during use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0035] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Figure 1 and Figure 2 Two common dry-type transformer structures are shown. The main body includes an iron core 3, a low-voltage winding 2 sleeved on the outside of the iron core 3, and a high-voltage winding 1 coaxially sleeved on the outside of the low-voltage winding 2. Both the high-voltage winding 1 and the low-voltage winding 2 are integrally vacuum-cast with epoxy resin to form overall insulation protection. Figure 1 The dry-type transformer is shaped like a racetrack. Figure 2 The dry-type transformer is circular in shape.

[0037] Figure 3 Given the existing cross-sectional structure of dry-type transformers, air breakdown frequently occurs during actual operation. Studies show that this phenomenon mainly concentrates at the upper and lower ends of the high-voltage winding 1 and the low-voltage winding 2 of the dry-type transformer. This is due to significant magnetic field distortion at the winding ends, while the middle region of the windings rarely experiences this problem due to the more uniform magnetic field distribution. When the air gap between the upper and lower ends of the windings is insufficient, the local electric field strength increases significantly, leading to air breakdown, arc discharge, and noticeable discharge noise. This not only interferes with the normal operation of the dry-type transformer, causing a decline in equipment performance and a shortened service life, but may also cause equipment failure, posing a serious threat to the overall safety of power supply line facilities.

[0038] This invention provides an air-breakdown prevention structure for a dry-type transformer and a dry-type transformer including this structure, solving the problems of air breakdown at the winding ends and related safety hazards through targeted structural design. Combined with... Figures 4 to 9 As shown, an annular first insulating layer 5 is attached to the inner surface of the high-voltage winding 1, and an annular second insulating layer 6 is attached to the outer surface of the low-voltage winding 2. An annular air gap 4 is formed between the first insulating layer 5 and the second insulating layer 6. This air gap 4 provides a basic insulation distance between the high-voltage winding 1 and the low-voltage winding 2. Together with the insulation protection of the insulating layer, it initially blocks the risk of electrical breakdown between the high-voltage and low-voltage windings.

[0039] In specific embodiments, both the first insulating layer 5 and the second insulating layer 6 are made of epoxy resin casting or impregnated mesh-like glass fiber. This material combines high insulation strength and crack resistance, avoiding the problems of cracking and insulation failure caused by unreliable curing of traditional insulating layers after long-term operation, and providing a stable foundation support for the air breakdown protection structure. In some embodiments, the first insulating layer 5 and the second insulating layer 6 are part of the overall winding enclosure; in other embodiments, the first insulating layer 5 and the second insulating layer 6 can also be separate structures.

[0040] In a specific embodiment, the thickness of the first insulating layer 5 and the second insulating layer 6 is 2~10mm, which can be selected according to the different voltage levels of the product; the thickness of the air gap 4 is set to 20~85mm, which can be selected according to the different voltage levels of the product. The thickness of the insulating layers ensures sufficient structural strength while avoiding excessive thickness that would result in insufficient thickness of the air gap 4; the thickness of the air gap 4 provides sufficient basic insulation distance for the high and low voltage windings, adapting to high voltage level operating scenarios.

[0041] Combination Figure 4 and Figure 5 As shown, in this embodiment, the first insulation layer 5 of the dry-type transformer has a notch 7 at its ends (both upper and lower). The surface of the notch 7 is an inclined plane that gradually increases in size towards the winding end, and the cross-sectional shape is a right triangle. Due to the presence of the end notch 7, the air distance in the corresponding area is increased, and the air distance is gradually distributed along the winding axis, thereby eliminating the end magnetic field distortion, reducing the local electric field strength, and fundamentally preventing the occurrence of air breakdown, thus ensuring the stable and safe operation of the transformer.

[0042] In some preferred embodiments, the dimensions of the notch 7 are optimized, combined with Figure 5 As shown, the dimensions of the cross-sectional triangle satisfy the following relationships: T ≥ a ≥ 3 / 4T, 3D ≥ h ≥ D, where a is the base length of the cross-sectional triangle of notch 7, h is the height of the cross-sectional triangle of notch 7, T is the thickness of the first insulating layer 5, and D is the width of the air gap 4. This dimensional design was determined through theoretical calculations and experimental verification: the base length a is not less than 3 / 4T, ensuring that notch 7 increases the air gap without compromising the structural strength of the insulating layer; the height h is controlled between D and 3D, precisely covering the core area of ​​magnetic field distortion at the winding end, maximizing the air gap in this area, uniformly reducing the local electric field strength, and fundamentally preventing air breakdown.

[0043] Combination Figure 6 and Figure 7As shown, another preferred embodiment is provided, which improves the structure based on the above embodiment. The upper and lower ends of the second insulating layer 6 are also provided with notches 7, and the notches 7 of the first insulating layer 5 and the second insulating layer 6 are symmetrical, making the ends of the windings funnel-shaped openings. This increases the adjustable range of the air distance in the end region and effectively protects the ends of both the high-voltage winding 1 and the low-voltage winding 2.

[0044] Combination Figure 7 As shown, in this embodiment, a silicone rubber layer 8 is uniformly coated on the surface of the notch 7, thereby improving the air breakdown protection effect at the winding end and preventing the arc light generated by air breakdown from igniting the epoxy resin encapsulation layer or insulation layer, effectively reducing derivative safety hazards such as combustion and explosion, and ensuring the safe operation of the transformer.

[0045] In a specific embodiment, the material of the silicone rubber layer 8 is HTV silicone rubber or RTV silicone rubber. Both of these silicone rubbers have high temperature resistance and can maintain stable insulation performance in the high temperature environment generated by the transformer operation, avoiding insulation protection failure due to material aging.

[0046] Combination Figure 8 As shown, another embodiment of the air breakdown prevention structure is provided, which differs from the above embodiment mainly in the cross-sectional shape of the notch 7. In this embodiment, notches 7 are provided at both the upper and lower ends of the first insulating layer 5, the surface of the notch 7 is parallel to the inner surface of the first insulating layer 5, and the cross-sectional shape is rectangular. The advantage of this rectangular structure design is its ease of processing. Compared with the right-angled triangular bevel, the rectangular notch 7 does not require a complex tilting and cutting process and can be achieved through conventional cutting or mold forming, reducing production difficulty and manufacturing costs. At the same time, it can accurately correspond to the magnetic field distortion region at the winding end and stably increase the air distance.

[0047] In some preferred embodiments, the dimensions of the rectangular structure are optimized so that the cross-sectional rectangular dimensions satisfy the following relationships: T≥W≥3 / 4T, 3D≥L≥D, where W is the width of the rectangular section of the notch 7, L is the length of the rectangular section of the notch 7, T is the thickness of the first insulating layer 5, and D is the width of the air gap 4. The logic behind this dimensional constraint is as follows: the width W is not less than 3 / 4T, ensuring the integrity of the insulating layer structure; the length L covers the core region of magnetic field distortion, ensuring the increased air gap effect, ultimately achieving excellent air breakdown resistance.

[0048] Combination Figure 9 As shown, in another preferred embodiment, a silicone rubber layer 8 is uniformly coated on the surface of the notch 7. The thickness of the silicone rubber layer 8 is preferably 0.1~1.5mm, providing sufficient insulation protection and fire-blocking capability, while not affecting the breakdown protection function of the notch 7.

[0049] The air breakdown protection structure provided in the above embodiments can be used in dry-type transformers without making significant changes to the transformer's core 3, winding method, and other common core structures. Only a gap 7 needs to be added during the winding insulation layer processing stage, and a silicone rubber layer 8 needs to be coated to complete the upgrade and transformation. This adapts to the existing production and transformation process of dry-type transformers and significantly reduces application costs.

[0050] In practical operation, this dry-type transformer utilizes the synergistic effect of its air-breakdown protection structure: on the one hand, the gap 7 increases the air distance at the winding ends, which, together with the air gap 4, reduces the local field strength and eliminates air breakdown caused by magnetic field distortion; on the other hand, the silicone rubber layer 8 forms an insulating protection, blocking the risk of combustion and explosion, and ensuring the long-term operational stability of the transformer. Even in high-voltage scenarios, this structure can maintain reliable insulation performance, meeting the dual requirements of power supply line facilities for stable transformer operation and safety protection.

[0051] In summary, the above embodiments, through differentiated notch morphology design, combined with material optimization and size constraints, not only accurately solve the problem of air breakdown at the winding ends of dry-type transformers, but also avoid the safety hazards caused by breakdown; at the same time, the improved structure is simple and highly adaptable, taking into account both performance improvement and cost control, providing an effective technical solution for the safe and reliable application of dry-type transformers in power supply line facilities.

[0052] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the scope of protection of this invention.

Claims

1. An air-breakdown protection structure for a dry-type transformer, characterized in that, It includes a ring-shaped high-voltage winding and a low-voltage winding, which are encapsulated by epoxy resin casting. The high-voltage winding is sleeved on the outside of the low-voltage winding. The high-voltage winding includes a first insulating layer disposed on its inner surface, and the low-voltage winding includes a second insulating layer disposed on its outer surface. An air gap is formed between the first insulating layer and the second insulating layer. The upper and lower ends of the first insulating layer and / or the second insulating layer are provided with notches.

2. The air-breakdown resistant structure according to claim 1, characterized in that, The surface of the notch is provided with a silicone rubber layer.

3. The air-breakdown resistant structure according to claim 1 or 2, characterized in that, The surface of the notch is an inclined plane that gradually increases in size towards the end opening, and the cross-sectional shape of the notch is a right triangle.

4. The air-breakdown resistant structure according to claim 3, characterized in that, The dimensions of the cross-sectional triangle of the notch satisfy the following relationship: T≥a≥3 / 4T, 3D≥h≥D, where a is the length of the base of the cross-sectional triangle of the notch, h is the height of the cross-sectional triangle of the notch, T is the thickness of the insulating layer corresponding to the notch, and D is the width of the air gap.

5. The air-breakdown resistant structure according to claim 1 or 2, characterized in that, The surface of the notch is parallel to the inner surface of the first insulating layer, and the cross-sectional shape of the notch is rectangular.

6. The air-breakdown resistant structure according to claim 5, characterized in that, The dimensions of the rectangular cross-section of the notch satisfy the following relationship: T≥W≥3 / 4T, 3D≥L≥D, where W is the width of the rectangular cross-section of the notch, L is the length of the rectangular cross-section of the notch, T is the thickness of the insulating layer corresponding to the notch, and D is the width of the air gap.

7. The air-breakdown resistant structure according to claim 1, characterized in that, The thickness of the first insulating layer and the second insulating layer is 2~10mm, and the thickness of the air gap is 20~85mm.

8. The air-breakdown resistant structure according to claim 2, characterized in that, The thickness of the silicone rubber layer is 0.1~1.5mm.

9. The air-breakdown resistant structure according to claim 2, characterized in that, The first and second insulating layers are formed by epoxy resin casting or impregnation of mesh glass fibers, and the silicone rubber layer is made of HTV silicone rubber or RTV silicone rubber.

10. A dry-type transformer, characterized in that, Includes the air-breakdown protection structure as described in any one of claims 1-9.

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