A high-voltage cascade isolation transformer of solid insulation structure

Abstract

The application provides a high-voltage cascade isolation transformer with a solid insulation structure, and belongs to the technical field of isolation transformers, and comprises at least one transformer module, wherein the transformer module has two cascade-connected sub-transformer units arranged side by side, and the sub-transformer unit comprises: a high-voltage winding, which is of a solid insulation structure; and a low-voltage winding, which is coaxially arranged with the high-voltage winding; the low-voltage windings of the two sub-transformer units are connected in series; the high-voltage cascade isolation transformer with the solid insulation structure of the application adopts insulation materials applicable to direct-current voltage, adopts semiconductor shielding and main insulation pouring technology in stages, and can realize low partial discharge design and high insulation resistance of the transformer; meanwhile, the cascade connection mode is adopted to form a unit modular structure, and the unit modular structure can be expanded and applied according to different voltage grades. The high-voltage cascade isolation transformer with the solid insulation structure can realize power supply from ground potential to tens of kilovolts or even hundreds of kilovolts or higher potential, and realizes ground isolation of the high potential.

Description

Technical Field

[0001] The present invention relates to the technical field of isolation transformers, and in particular to a high-voltage cascade isolation transformer with a solid insulation structure. Background Art

[0002] A high-voltage isolation transformer is a transformer that uses certain insulation measures to isolate the currents between the primary and secondary windings, thereby electrically separating the input and output windings.

[0003] With the development of DC transmission design, some new devices have appeared in DC systems, such as DC circuit breakers. These devices are passive devices and require external energy supply. These devices contain a large number of power components that need to be supplied, but these DC devices cannot obtain energy from the DC system, so they need external energy supply. Such external energy supply devices need to have several characteristics: (1) they can realize the transmission of electric energy from ground potential to high potential, and the potential distribution and performance of DC passive devices cannot be affected by the power transmission; (2) they can realize the isolation of DC voltage and can withstand the transient voltage impact of the system; (3) they can avoid various DC effects caused by DC voltage, such as space charge accumulation and electrostatic dust absorption effect under DC; (4) most importantly, they cannot use oil insulation like conventional transformers to avoid fire risks. Therefore, there is a demand for isolation transformers.

[0004] Currently, high-voltage power transformers are primarily used in the AC sector, and there are various types of transformers, all primarily designed to withstand AC voltages. Common power transformers above 35kV, to achieve voltage isolation and provide the necessary primary insulation, are generally oil-immersed transformers. This poses a fire risk and therefore cannot be used as isolation transformers for DC passive devices. While solid insulation structures are available for transformers 35kV and below, these are typically made of epoxy resin, which can lead to significant partial discharge and space charge accumulation under DC voltages. Furthermore, the voltage level is too low to meet application requirements. Another type of gas-filled transformer, while oil-free, requires a gas pressure exceeding 0.5MPa to ensure insulation. This poses a risk of leakage during operation, making operation and maintenance difficult.

[0005] In view of the general technical level and design methods of current power transformers, as well as the unfavorable factors of voltage level expansion, and based on the application requirements of transformers in high voltage and special application conditions, a new design of solid-insulated high-voltage DC isolation transformers is needed. Summary of the Invention

[0006] Therefore, the patent of this invention aims to provide a new type of high-voltage cascade isolation transformer with solid insulation structure, so as to realize the application of isolation transformer under DC high voltage of hundreds of kilovolts and above, and at the same time have the characteristics of low partial discharge and high suppression of space charge to meet the long-term reliable application under DC voltage.

[0007] In order to solve the above technical problems, the present invention provides a high-voltage cascade isolation transformer with a solid insulation structure, comprising: at least one transformer module, wherein the transformer module has two cascade-connected sub-transformer units arranged in parallel, and the sub-transformer units include:

[0008] High voltage winding, solid insulation structure;

[0009] A low-voltage winding is coaxially arranged with the high-voltage winding;

[0010] The low-voltage windings of the two sub-transformer units are connected in series.

[0011] As a preferred solution, the transformer modules are multiple and cascade-connected, the multiple transformer modules are stacked with intervals in the height direction, and a resistor-capacitor voltage balancing device is connected between two adjacent transformer modules.

[0012] As a preferred solution, the resistor-capacitor voltage balancing device is connected to the outside of the transformer module.

[0013] As a preferred solution, the RC voltage grading device includes: a packaging insulating cylinder and an end voltage grading ring connected to the outside of the packaging insulating cylinder, and a voltage grading capacitor and a voltage grading resistor are arranged in the packaging insulating cylinder.

[0014] As a preferred solution, the plurality of transformer modules are supported by supporting insulator columns.

[0015] As a preferred solution, the supporting insulator columns have four groups that are symmetrically arranged.

[0016] As a preferred solution, the transformer module located at the bottom layer is supported by support insulator columns.

[0017] As a preferred solution, a support frame is provided below the transformer module located at the lowest layer at a distance in the height direction, and a resistor-capacitor voltage balancing device is connected between the support frame and the transformer module.

[0018] As a preferred solution, it also includes:

[0019] The inclined insulator is arranged obliquely and connected between two adjacent layers of the transformer modules.

[0020] As a preferred solution, a shielding cover is provided above the transformer module located at the top layer at a distance in the height direction. The shielding cover is supported above the transformer module by supporting insulator columns, and a resistor-capacitor voltage equalizing device is connected to the transformer module.

[0021] The technical solution of the present invention has the following advantages:

[0022] 1. The solid-insulated high-voltage cascade isolation transformer provided by the present invention utilizes insulating materials suitable for DC voltages, employs semiconductor shielding, and employs staged casting of the main insulation. This achieves low partial discharge design and high insulation resistance. Furthermore, the cascade connection creates a modular unit structure, enabling scalable applications based on different voltage levels. This allows for power supply from ground potential to higher potentials of tens of kilovolts, even hundreds of kilovolts, and above, while also achieving high-potential ground isolation.

[0023] 2. The high-voltage cascade isolation transformer with a solid insulation structure provided by the present invention not only has all the functional characteristics of a dry-type transformer, but also has many advantages such as flexible expansion for high-voltage applications, compact structure, and excellent fire and explosion resistance. It can also be flexibly expanded to voltage levels above 35kV. Compared with conventional dry-type transformers, it has the advantages of higher insulation strength, low partial discharge suppression, low noise, and high heat dissipation.

[0024] 3. The solid-insulation high-voltage cascade isolation transformer provided by this invention can be applied in DC systems, exhibiting low partial discharge characteristics and very low space charge accumulation under DC voltage. This design uses the basic high-voltage winding bushing as the basic insulation structural unit, adopts a modular unit structure, and uses electrical cascade connections to achieve scalable applications at different voltage levels.

[0025] 4. The solid-insulated high-voltage cascade isolation transformer provided by the present invention comprises an independently structured transformer module comprising two high-voltage winding bushings, two low-voltage windings, an iron core structure, and an auxiliary support structure, which are assembled into a structurally integrated unit. Each high-voltage winding bushing of the transformer module corresponds to one low-voltage winding, forming a complete sub-transformer unit. Therefore, one transformer module actually comprises two sub-transformer units, which are connected in cascade.

[0026] 5. The high-voltage cascade isolation transformer with a solid insulation structure provided by the present invention, in order to achieve higher DC voltage level applications, the transformer modules are structurally made into an integral whole and cascaded in electrical connection to form a high-voltage cascade isolation transformer as a whole. Since multiple transformers are cascaded, a voltage-sharing design is required under high voltage. Therefore, a resistor-capacitor voltage-sharing device is connected in parallel next to each transformer module of the high-voltage cascade isolation transformer to achieve voltage balancing under transient steady-state voltage. In order to realize the high-voltage application of the high-voltage cascade isolation transformer and suppress corona discharge under high voltage, a shielding cover is added to the periphery of the transformer to optimize and suppress the distortion field strength under high voltage.

[0027] 6. Compared to traditional dry-type transformers, which face numerous technical limitations, such as insulation isolation, partial discharge suppression, low application voltage levels, and inflexible expansion applications, the solid-insulated high-voltage cascade isolation transformer provided by the present invention overcomes these limitations. Through innovative design implementation methods, it suppresses partial discharge within the solid insulation, controls the external spatial field strength, and solves the problem of spatial charge accumulation in DC voltages. The structure is compact and easily scalable. Furthermore, it can not only isolate and supply energy for passive power electronic equipment, but can also be expanded to the field of conventional AC power transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 It is a schematic three-dimensional structural diagram of an embodiment of a high-voltage cascade isolation transformer with a solid insulation structure of the present invention.

[0030] Figure 2 Schematic diagram of the three-dimensional structure of a transformer module.

[0031] Figure 3 for Figure 2 Schematic diagram of the electrical connections of the transformer module.

[0032] Figure 4 It is a schematic diagram of the three-dimensional structure of the high-voltage winding.

[0033] Description of reference numerals:

[0034] 1. Transformer module; 2. Support insulator column; 3. Resistor-capacitor voltage-grading device; 4. Encapsulated insulation tube; 5. End voltage-grading ring; 6. Shielding cover; 7. Oblique-stayed insulator; 8. Sub-transformer unit; 9. High-voltage winding; 10. Low-voltage winding; 11. Connecting busbar; 12. Voltage-grading cover; 13. Main insulation structure; 14. Surface insulation shed. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0038] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0039] This embodiment provides a specific implementation of a high-voltage cascade isolation transformer with a solid insulation structure.

[0040] like Figure 1As shown, the high-voltage cascade isolation transformer consists of n (n ≥ 1) transformer modules 1 stacked in height, with a certain air clearance between adjacent transformer modules 1 to achieve electrical insulation isolation under high voltage. Adjacent transformer modules 1 are supported by support insulator columns 2, and the lowest-level transformer module 1 is also supported to a certain height by support insulator columns 2 to achieve insulation isolation of the transformer modules 1 at that level from the ground.

[0041] A RC voltage-grading device 3 is suspended and fixed outside the transformer module 1. This device connects the upper and lower transformer modules 1. The device 3 consists of a voltage-grading capacitor, a voltage-grading resistor, an encapsulating insulating tube 4, and an end voltage-grading ring 5. The use of a suspended RC voltage-grading device 3 in this embodiment reduces the transformer's footprint and facilitates replacement and maintenance.

[0042] A shielding cover 6 is provided on the top of the high-voltage cascade isolation transformer, and the shielding cover 6 is used to achieve electric field uniformity and corona suppression of the isolation transformer under high voltage.

[0043] In order to ensure the structural stability of the high-voltage cascade isolation transformer and meet the seismic fortification intensity requirements, diagonal insulators 7 are connected between each layer of transformer modules 1 to achieve structural reinforcement.

[0044] like Figure 2 As shown, the transformer module 1 includes two cascade-connected sub-transformer units 8 arranged in parallel. Each sub-transformer unit 8 has a high-voltage winding 9 and a low-voltage winding 10 arranged coaxially with the high-voltage winding 9. The two high-voltage windings 9 are wound in opposite directions, and the two low-voltage windings 10 are electrically connected via a connecting busbar 11. In terms of external structural layout, the outlet terminals of the two high-voltage windings 9 are oriented in opposite directions. The outlet terminal of one high-voltage winding 9 serves as the inlet terminal of the first sub-transformer unit 8, and the outlet terminal of the other high-voltage winding 9 serves as the outlet terminal of the second sub-transformer unit 8.

[0045] The transformer module 1 also includes a core assembly and a voltage-grading cover 12. The core assembly contains core laminations and clamps that secure the core laminations and strengthen the structure. The core assembly is mounted within the casing of the high-voltage winding 9. A low-voltage winding 10 is coaxially arranged on the core assembly. The low-voltage winding 10 is directly fixed to the core arms, using the core assembly as a support framework.

[0046] like Figure 3The two sub-transformer units 8 are connected in series. The high-voltage winding 9 on one core arm and its coaxial low-voltage winding 10 form a sub-transformer unit 8. The incoming line of this sub-transformer unit 8 is the high-voltage winding 9, and the outgoing line is the low-voltage winding 10. The low-voltage winding 10 of this sub-transformer unit 8 is connected to the low-voltage winding 10 of the second sub-transformer unit 8. The incoming line of the second sub-transformer unit 8 is the low-voltage winding 10, and the outgoing line is the high-voltage winding 9. The two sub-transformer units 8 are connected in series, which can double the voltage level.

[0047] like Figure 4 As shown, the high-voltage winding 9 adopts a bushing structure, using a solid insulating material suitable for DC voltage, such as silicone rubber or EPDM rubber, and is cast into an integral body using a high-pressure injection molding process. Specifically, the bushing includes the high-voltage winding 9, which is cast within the solid insulating material, a main insulating structure 13, and creeping insulation sheds 14. The main insulating structure 13 provides insulation isolation between the high-voltage winding 9 and the low-voltage potential, while the creeping insulation sheds 14 ensure creeping insulation resistance, which is necessary to ensure contamination accumulation during operation under DC voltage.

[0048] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A high-voltage cascade isolation transformer with a solid insulation structure, characterized in that: include: A plurality of transformer modules (1) connected in cascade, wherein the plurality of transformer modules (1) are stacked with intervals in a height direction, a resistor-capacitor voltage balancing device (3) is connected between two adjacent transformer modules (1), and the resistor-capacitor voltage balancing device (3) is connected to the outside of the transformer module (1); The resistor-capacitor voltage grading device (3) comprises: a packaged insulating cylinder (4) and an end voltage grading ring (5) connected to the outside of the packaged insulating cylinder (4); a voltage grading capacitor and a voltage grading resistor are provided in the packaged insulating cylinder (4); The transformer module (1) has two cascade-connected sub-transformer units (8) arranged in parallel, and the sub-transformer units (8) include: The high voltage winding (9) is a solid insulation structure; A low-voltage winding (10) is coaxially arranged with the high-voltage winding (9); The low-voltage windings (10) of the two sub-transformer units (8) are connected in series.

2. The high-voltage cascade isolation transformer according to claim 1, characterized in that: The plurality of transformer modules (1) are supported by supporting insulator columns (2).

3. The high-voltage cascade isolation transformer according to claim 2, characterized in that: The supporting insulator columns (2) have four groups that are symmetrically arranged.

4. The high-voltage cascade isolation transformer according to claim 1, characterized in that: The transformer module (1) located at the bottom layer is supported below by a supporting insulator column (2).

5. The high-voltage cascade isolation transformer according to claim 4, characterized in that: A support frame is provided below the transformer module (1) located at the bottom layer at a distance in the height direction, and a resistance-capacitance voltage balancing device (3) is connected between the support frame and the transformer module (1).

6. The high-voltage cascade isolation transformer according to claim 1, characterized in that: Also includes: The oblique insulator (7) is arranged obliquely and connected between two adjacent layers of the transformer modules (1).

7. The high-voltage cascade isolation transformer according to claim 1, characterized in that: A shielding cover (6) is provided above the transformer module (1) located at the top layer at a distance in the height direction; the shielding cover (6) is supported above the transformer module (1) via a supporting insulator column (2), and a resistance-capacitance voltage balancing device (3) is connected between the shielding cover and the transformer module (1).

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