An expander and oil-filled bushing structure suitable for harmonic operating conditions

Abstract

The application discloses an expander and oil-filled bushing structure suitable for harmonic working conditions and relates to the technical field of voltage transformers. The expander is in a ring-shaped cavity structure. The expander is used for being arranged in the cavity structure between two adjacent oil-filled insulating bushings. The cavity of the expander is used for being filled with liquid insulating medium. A hole is arranged on the expander and is used for being connected with the cavity of one of the oil-filled insulating bushings through an external oil communication pipe. The expander is made of elastic material. The volume of the expansion cavity is greater than that of the expander. The expander is arranged at the connection position of the two capacitors, a larger expansion space is provided, a larger insulating oil expansion allowance is provided, the bushing structure is simplified, the operation reliability is improved, the expander is suitable for oil-insulated transformers, the expander is not arranged in the oil-filled bushing, the volume adaptive change of the insulating oil under different seasons and temperatures can be realized, the cost is reduced, and the transformer of different structures can be flexibly adapted.

Description

Technical Field

[0001] This invention relates to the field of voltage transformer technology, specifically to an expander and oil-filled bushing structure suitable for harmonic operating conditions. Background Technology

[0002] Voltage transformers are essential measuring devices in power systems, typically using oil as the primary insulating medium. Due to temperature variations in different seasons and operating conditions, the volume of the insulating oil changes accordingly, necessitating an expander to ensure that the insulating oil within a confined space has room to expand or contract.

[0003] With the rapid development of new power systems, the widespread application of power electronic devices has led to increasingly serious harmonic problems in these systems. Harmonics can cause significant temperature rises, with studies showing that harmonic temperature rises can exceed 50K. This temperature rise causes more pronounced oil expansion. Traditional expanders are cylindrical structures placed inside the oil-filled bushing. The conductive rods inside the bushing interfere with the expander, and there is no space to accommodate a traditional cylindrical expander, making it unable to effectively compensate for changes in oil volume with temperature. In extreme cases, if the internal pressure cannot be released through the expander, the enormous mechanical stress may cause the bushing porcelain sleeve to rupture or the internal insulation to be damaged, leading to serious equipment accidents.

[0004] In summary, the existing expanders cannot meet the expansion requirements under harmonic conditions and are prone to generating excessive stress, which can damage the equipment. Summary of the Invention

[0005] To address the problem that existing expanders cannot adapt to the expansion requirements under harmonic conditions, and are prone to generating excessive stress that could damage the equipment.

[0006] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention proposes an expander suitable for harmonic operating conditions, wherein the expander has an annular cavity structure; The expander is used to be fitted inside the expansion cavity structure between two adjacent oil-filled insulating sleeves; The annular cavity of the expander is used to fill the liquid insulating medium. The expander has a hole for connecting to the cavity of one of the oil-filled insulating sleeves through an external oil connecting pipe. The expander is made of an elastic material; The volume of the expansion cavity is larger than the volume of the expander.

[0007] Preferably, the ratio of the volume of the expander to the volume of the expansion cavity is in the range of 1:2 to 2:3.

[0008] Preferably, the expander is made of rubber.

[0009] Preferably, the oil connecting pipe is located at the bottom of the expander and is connected to the cavity of the oil-filled insulating sleeve below the expander.

[0010] Preferably, the oil connecting pipe and the expander are integrally formed.

[0011] Preferably, the liquid insulating medium is insulating oil.

[0012] Secondly, the present invention proposes an oil-filled sleeve structure, comprising: several interconnected sections of oil-filled insulating sleeve, a metal flange fixed on each section of oil-filled insulating sleeve, an insulating insert mounted on the metal flange, a metal guide rod mounted on the insulating insert, and an expander suitable for harmonic conditions as described in any of the above. The metal flanges on two adjacent oil-filled insulating bushings are joined together, and the joining end faces are brought close together to form an annular expansion cavity structure. The expander is installed in the annular expansion cavity structure. The insulating insert and the metal guide rod are fixedly installed at the center of the annular expansion cavity structure. The metal guide rod passes through the insulating insert and connects to the conductor at the center of the oil-filled insulating bushing.

[0013] Preferably, the metal guide rod is located at the central axis of the oil-filled insulating sleeve.

[0014] Preferably, a gap is provided between the insulating insert and the expander.

[0015] Preferably, the oil connecting pipe passes through the metal flange and connects the cavity of the expander and the cavity of the oil-filled insulating sleeve respectively.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides an expander suitable for harmonic operating conditions. The expander, with an annular cavity structure, is fitted inside the expansion cavity between two adjacent oil-filled insulating bushings. The annular cavity of the expander is filled with a liquid insulating medium. An opening is formed on the expander, and this opening communicates with the interior of the oil-filled insulating bushing cavity via an external oil connecting pipe. By placing the expander at the connection point of the two capacitor sections, this location can provide a larger expansion space. By limiting the volume of the expansion cavity and using an expander made of elastic material, a larger expansion margin for the insulating oil is achieved, simplifying the bushing structure design and insulation design, and improving operational reliability. This expander is suitable for oil-insulated transformers. Since the expander is not located inside the oil-filled bushing, it allows for adaptive volume changes of the insulating oil under different seasons and temperatures, reducing costs, improving reliability, and flexibly adapting to transformers with different structures. It is particularly suitable for scenarios with significant temperature changes under harmonic operating conditions, avoiding equipment damage caused by excessive stress.

[0017] This invention provides an oil-filled bushing structure. By incorporating a variable-shape expander inside the bushing, interference with insulating inserts or metal conductors is avoided, and the connection or outgoing lines between multiple sections are not affected. This structure is suitable for oil-filled bushings of instrument transformers with different structural designs. The expander is positioned at the connection point of two capacitor sections, simplifying the bushing structure and insulation design and improving operational reliability. Each oil-filled bushing unit is equipped with its own expander, providing a larger expansion margin for the insulating oil, making it suitable for scenarios with high temperature rise under harmonic operation. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the installation structure of an expander suitable for harmonic operating conditions according to Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the external structure of an expander suitable for harmonic operating conditions according to Embodiment 1 of the present invention.

[0019] In the diagram: 1 is the expander, 2 is the oil-filled insulating sleeve, 3 is the metal flange, 4 is the insulating insert, 5 is the metal guide rod, and 6 is the oil connecting pipe. Detailed Implementation

[0020] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used 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.

[0022] Furthermore, 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 indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0023] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0025] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0026] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0027] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0028] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0029] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0030] Example 1: This invention provides an expander suitable for harmonic operating conditions, such as... Figure 1 and Figure 2 As shown, the expander 1 has an annular cavity structure.

[0031] The expander 1 is used to be fitted inside the cavity structure between two adjacent oil-filled insulating sleeves 2; the cavity of the expander 1 is used to fill the liquid insulating medium, and the expander 1 has a hole for connecting to the cavity of one of the oil-filled insulating sleeves 2 through an external oil connecting pipe 6.

[0032] The expander 1 is made of an elastic material; the volume of the expansion cavity is larger than the volume of the expander 1.

[0033] This invention provides an expander suitable for harmonic operating conditions. The expander, with an annular cavity structure, is fitted inside the expansion cavity between two adjacent oil-filled insulating bushings. The annular cavity of the expander is filled with a liquid insulating medium. An opening is formed in the expander, and this opening communicates with the interior of the oil-filled insulating bushing cavity via an external oil connecting pipe. By placing the expander at the connection point of the two capacitor sections, this location can provide a larger expansion space. By limiting the volume of the expansion cavity and using an expander made of elastic material, a larger expansion margin for the insulating oil is achieved, simplifying the bushing structure design and insulation design, and improving operational reliability. This expander is suitable for oil-insulated transformers. Since the expander is not located inside the oil-filled bushing, it allows for adaptive volume changes of the insulating oil under different seasons and temperatures, reducing costs, improving reliability, and flexibly adapting to transformers with different structures. It is particularly suitable for scenarios with significant temperature changes under harmonic operating conditions, avoiding equipment damage caused by excessive stress.

[0034] Specifically, in this embodiment of the invention, the expander 1 is made of a non-metallic elastic material. The expander has a variable volume, and the material is preferably rubber. The expander proposed in this invention, suitable for oil-insulated voltage transformers, can achieve adaptive volume changes of the insulating oil under different seasons and temperatures, and is particularly suitable for scenarios with significant temperature changes under harmonic conditions. Using a rubber expander or other non-metallic materials can avoid the distortion of the electric field caused by metal expanders, reduce insulation stress, and improve the insulation reliability of the transformer.

[0035] Specifically, such as Figure 1 As shown, in this embodiment of the invention, the volume of the expansion cavity is larger than the volume of the expander 1. In this embodiment, the volume ratio of the expander 1 to the expansion cavity is preferably in the range of 1:2 to 2:3, that is, the volume of the expander 1 accounts for 1 / 2 to 2 / 3 of the volume of the expansion cavity. By limiting the expansion cavity between the expander 1 and the two oil-filled insulating bushings 2, the expansion margin is guaranteed, avoiding damage to the voltage transformer equipment caused by excessive stress, and ensuring that the volume of the insulating oil adapts to different seasons and temperatures.

[0036] Specifically, such as Figure 2 As shown, the expander 1 in this embodiment of the invention has an annular cavity structure (i.e., tire shape). The empty space in the middle is used to install the insulating insert 4 or the metal guide rod 5. Therefore, the expander 1 will not interfere with the insulating insert 4 or the metal guide rod 5, and will not affect the connection or wire exit between multiple sections of oil-filled insulating sleeves, making full use of the space between multiple sections.

[0037] It should be further explained that the oil connecting pipe 6 is located at the bottom of the expander 1 (i.e., at the top of the oil-filled bushing sealing unit) and is connected to the interior of the oil-filled insulating bushing 2 below the expander 1. The oil connecting pipe 6 and the expander 1 are integrally structured. Each voltage transformer sealing unit of the expander is equipped with one expansion pipe, the shape of which depends on the internal structure of the bushing. The expander is internally connected to the oil-filled bushing 2. This expander is suitable for the connection part of a voltage transformer composed of multiple sealing units.

[0038] In this embodiment of the invention, an expansion joint for an oil-insulated voltage transformer is connected to an oil-filled bushing. The expansion joint has a variable volume and can be made of rubber or other non-metallic materials. The liquid insulating medium is preferably insulating oil. One expansion joint is configured in each oil-filled bushing enclosure unit of the voltage transformer. Each section is individually oil-filled and sealed, and there is a cavity between two sections to house the expansion joint. The shape of the expansion joint is determined by the internal structure of the bushing and does not affect the connection or outgoing lines between multiple sections.

[0039] Example 2: Based on the same inventive concept, the present invention also provides a voltage transformer, such as... Figure 1 As shown, it includes: several interconnected oil-filled insulating sleeves 2, a metal flange 3 installed between two adjacent oil-filled insulating sleeves 2, an insulating insert 4 installed on the metal flange 3, a metal guide rod 5 installed on the insulating insert 4, and an expander 1 as in Embodiment 1 suitable for harmonic conditions.

[0040] The metal flanges 3 on two adjacent oil-filled insulating sleeves 2 are joined together, and the joining end faces are brought close to each other to form an annular expansion cavity structure. The expander 1 is installed in the annular expansion cavity structure. The insulating insert 4 and the metal guide rod 5 are fixedly installed at the center position of the annular expansion cavity structure. The metal guide rod 5 passes through the insulating insert 4 and connects to the conductor at the center of the oil-filled insulating sleeve 2.

[0041] This invention achieves adaptive volume change of insulating oil under different seasons and temperatures by installing a variable-volume closed container on the oil-filled bushing of a voltage transformer and communicating with the bushing. It is particularly suitable for scenarios with significant temperature changes under harmonic conditions.

[0042] It should be further explained that the oil-filled insulating bushing 2, as an integral component, uses the metal flange 3, insulating oil and internal insulating inserts 4 to safely introduce the high-potential metal conductor 5 into the low-potential voltage transformer body, allowing the high-voltage conductor to safely pass through the grounded voltage transformer tank or shell.

[0043] The metal conductor 5 serves as a current path and is located at the central axis of the oil-filled insulating bushing 2. The metal conductor 5 is a conductor passing through the center of the oil-filled insulating bushing 2 and is directly connected to the external high-voltage line and the primary winding inside the transformer, responsible for conducting current or voltage signals. In a voltage transformer, the metal conductor 5 is typically connected to the primary coil.

[0044] Specifically, in this embodiment of the invention, the metal flange 3 has a ring structure and is a metal ring component installed outside the bushing insulator. It is used to connect two adjacent oil-filled insulating bushings or to fix the oil-filled insulating bushing as a whole on the oil tank or housing of the voltage transformer, and must be reliably grounded during operation.

[0045] Specifically, a gap is provided between the insulating insert 4 and the expander 1. The insulating insert 4 is a capacitive insulating core or an insulating barrier. In the oil-filled bushing, it serves to insulate the metal guide rod 5. It can be an insulating paper layer wrapped on the guide rod, or a multi-layer insulating paper tube with metal foil embedded in between. Its function is to forcibly improve the extremely uneven electric field distribution between the guide rod and the flange, and prevent partial discharge and insulation breakdown.

[0046] Further explanation is needed: the metal flange 3 fixes the oil-filled insulating bushing 2 to the housing of the voltage transformer and maintains it at ground zero potential. The high-potential metal conductor 5 passes through the center of the flange, relying on the insulating insert 4 and insulating oil to isolate the high and low potentials, thereby safely introducing voltage into the transformer's interior. The oil connecting pipe 6 passes through the metal flange 3, connecting the cavity of the expansion tank 1 to the cavity of the oil-filled insulating bushing 2. The structure of the oil-filled insulating bushing ensures that the high-voltage lead of the voltage transformer does not discharge to ground or short-circuit when passing through the grounded metal housing. The voltage transformer is used to proportionally reduce the voltage in a high-voltage circuit for use by measuring instruments and relay protection.

[0047] Further explanation is needed regarding the installation process of the oil-filled bushing structure in this embodiment of the invention: The metal guide rod 5 is located at the very center (i.e., the central axis) of the entire oil-filled bushing structure. The conductor passes vertically through the top or side of the voltage transformer. The upper half of the conductor is exposed to the air and connected to the high-voltage line, while the lower half extends into the oil tank of the voltage transformer and is directly connected to the primary winding.

[0048] It needs to be further explained that the liquid insulating medium (i.e., insulating oil) fills the entire cavity of the oil-filled insulating sleeve 2. The metal flange 3 is fitted onto the oil-filled insulating sleeve 2, and the inner circle of the metal flange 3 is tightly fixed and seals the outer wall of the oil-filled insulating sleeve 2. The metal guide rod 5 is at the very center, wrapped with an insulating insert 4, and is inserted into the oil-filled insulating sleeve 2 filled with insulating oil and fixed on the metal flange 3. The expander 1 is installed in the cavity structure, and the outer circle of the metal flange 3 is fixedly connected by bolts.

[0049] The variable-shape expander proposed in this invention is determined according to the internal structure of the bushing, avoiding interference with the insulating insert 4 or the metal guide rod 5, and does not affect the connection or outgoing lines between multiple sections. It is suitable for oil-filled bushings of transformers with different structural designs. The expander is not inside the oil-filled bushing, but is arranged at the connection between two capacitor sections, simplifying the bushing structure design and insulation design, and improving operational reliability. The voltage transformer is composed of multiple oil-filled bushing enclosed units, each equipped with an expander, providing a larger expansion margin for the insulating oil, and is suitable for scenarios with high temperature rise under harmonic operation.

[0050] This invention provides an oil-filled bushing structure. By incorporating a variable-shape expander inside the bushing, interference with insulating inserts or metal conductors is avoided, and the connection or outgoing lines between multiple sections are not affected. This structure is suitable for oil-filled bushings of instrument transformers with different structural designs. The expander is positioned at the connection point of two capacitor sections, simplifying the bushing structure and insulation design and improving operational reliability. Each oil-filled bushing unit is equipped with its own expander, providing a larger expansion margin for the insulating oil, making it suitable for scenarios with high temperature rise under harmonic operation.

[0051] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. An expander suitable for harmonic operating conditions, characterized in that, The expander (1) has an annular cavity structure; The expander (1) is used to be fitted inside the expansion cavity between two adjacent oil-filled insulating sleeves (2); The annular cavity of the expander (1) is used to fill the liquid insulating medium. The expander (1) has a hole for connecting the hole to the cavity of one of the oil-filled insulating sleeves (2) through an external oil connecting pipe (6). The expander (1) is made of an elastic material; The volume of the expansion cavity is greater than the volume of the expander (1).

2. An expander suitable for harmonic operating conditions according to claim 1, characterized in that, The ratio of the volume of the expander (1) to the volume of the expansion cavity is in the range of 1:2 to 2:

3.

3. An expander suitable for harmonic operating conditions according to claim 1, characterized in that, The expander (1) is made of rubber.

4. An expander suitable for harmonic operating conditions according to claim 1, characterized in that, The oil connecting pipe (6) is located at the bottom of the expander (1) and is connected to the cavity of the oil-filled insulating sleeve (2) below the expander (1).

5. An expander suitable for harmonic operating conditions according to claim 1, characterized in that, The oil connecting pipe (6) and the expander (1) are integrally structured.

6. An expander suitable for harmonic operating conditions according to claim 1, characterized in that, The liquid insulating medium is insulating oil.

7. An oil-filled casing structure, characterized in that, include: A number of interconnected oil-filled insulating sleeves (2), a metal flange (3) fixed on each oil-filled insulating sleeve (2), an insulating insert (4) installed on the metal flange (3), a metal guide rod (5) installed on the insulating insert (4), and an expander (1) suitable for harmonic conditions as described in any one of claims 1 to 6. The metal flanges (3) on two adjacent oil-filled insulating sleeves (2) are joined together, and the joint end faces are brought close to each other to form an annular expansion cavity structure. The expander (1) is installed in the annular expansion cavity structure. The insulating insert (4) and the metal guide rod (5) are fixedly installed at the center of the annular expansion cavity structure. The metal guide rod (5) passes through the insulating insert (4) and connects to the conductor at the center of the oil-filled insulating sleeve (2).

8. The oil-filled casing structure according to claim 7, characterized in that, The metal guide rod (5) is located at the central axis of the oil-filled insulating sleeve (2).

9. The oil-filled casing structure according to claim 7, characterized in that, A gap is provided between the insulating insert (4) and the expander (1).

10. The oil-filled casing structure according to claim 7, characterized in that, The oil connecting pipe (6) passes through the metal flange (3) and connects the cavity of the expander (1) and the cavity of the oil-filled insulating sleeve (2) respectively.

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