A DC isolation transformer with an expandable iron core structure

Abstract

The present invention discloses a DC isolation transformer with a same core expandable structure, which is composed of several sub-transformers connected in cascade form, and the sub-transformer includes: a core assembly, including a first core column and a second core column; an input side winding, including an input side inner winding, an input side insulating support, and an input side outer winding sleeve sequentially sleeved on the first core column, and the input side outer winding sleeve contains the input side outer winding; an output side winding, including an output side inner winding, an output side insulating support, and an output side outer winding sleeve sequentially sleeved on the second core column, and the input side outer winding sleeve contains the input side outer winding; the two ends of the input side inner winding and the two ends of the output side inner winding are respectively connected to form a circuit for transmitting energy. The sub-transformer with the same core structure can achieve double insulation isolation capability under the same core; and several sub-transformers can be expanded in a cascade manner to achieve insulation isolation of higher voltage levels.

Description

Technical Field

[0001] The invention relates to the technical field of high-voltage direct current power transmission, and in particular to a direct current isolation transformer with an expandable iron core. Background Art

[0002] High-voltage DC circuit breakers are the core equipment for realizing short-circuit current interruption and fault isolation in flexible DC transmission systems, and are also the key connection nodes in high-voltage and large-capacity DC power grids.

[0003] At present, DC circuit breakers with engineering application significance generally adopt a hybrid technology route that combines power electronic switches and mechanical switches, collectively referred to as hybrid DC circuit breakers. The hybrid DC circuit breaker includes a large number of semiconductor cascade components and multiple sets of mechanical switch modules. These components can only work when they are supplied with external power. However, the special operating conditions of the DC circuit breaker make it impossible to obtain power online like the converter valve, but need to be supplied with energy from the station power system. The station power is at ground potential, and the circuit breaker is at high DC potential. It is necessary to achieve high DC potential isolation between the two. The current research methods include electromagnetic energy transmission and isolation with transformers, wireless energy electromagnetic transmission without transformers, laser energy transmission and other energy transmission methods. The engineering operable method is the electromagnetic energy transmission and isolation method with transformers. In this case, the transformer is required to have the function of high voltage isolation of power transmission.

[0004] At present, transformers above 35kV used in the power field basically use oil-immersed transformers to achieve voltage isolation and provide necessary main insulation. However, the use of oil-immersed transformers has the risk of oil leakage and fire. For some special high-voltage application conditions, especially power electronic equipment in the field of flexible AC transmission and DC equipment in the field of high-voltage and large-capacity DC transmission, power equipment is required to adopt oil-free design.

[0005] Transformers that adopt oil-free design include gas-insulated transformers, pure dry-type insulation transformers, or gas-and-dry mixed insulation transformers instead of oil-immersed transformers. Since gas-insulated transformers need to detect gas pressure and temperature, and explosion-proof issues must also be considered, pure dry-type insulation transformers are currently the preferred choice.

[0006] However, the current pure dry-type insulation transformers usually adopt a structure in which the input winding and the output winding are arranged on the same core column. The main insulation distance, dry arc distance and creepage distance are generally insufficient, and the insulation withstand voltage capability is poor. In high-voltage systems with voltage levels above 35kV, partial discharge problems are prone to occur. Based on conventional design methods, dry-type transformers have technical bottlenecks at voltage levels above 35kV, and the problem of partial discharge under high voltage has not been solved. Summary of the invention

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the poor insulation withstand voltage capability of the dry-type isolation transformer in the prior art and the technical problem that partial discharge is prone to occur at high voltage levels, thereby providing a DC isolation transformer with an expandable iron core structure.

[0008] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0009] A DC isolation transformer with an expandable iron core structure, comprising a plurality of sub-transformers connected in cascade, the sub-transformers comprising:

[0010] A core assembly, comprising a first core leg and a second core leg;

[0011] The input side winding comprises an input side inner winding sleeved on the first core column, an input side outer winding sleeve sleeved on the outer periphery of the input side inner winding, and an input side insulating support member located between the input side inner winding and the input side outer winding sleeve, wherein the input side outer winding sleeve is wrapped with the input side outer winding;

[0012] The output side winding comprises an output side inner winding sleeved on the second core column, an output side outer winding sleeve sleeved on the outer periphery of the output side inner winding, and an output side insulating support member located between the output side inner winding and the output side outer winding sleeve, wherein the output side outer winding sleeve is wrapped with the output side outer winding;

[0013] The two ends of the input side inner winding and the two ends of the output side inner winding are respectively connected to form a loop for transmitting energy; the input side outer winding has an input terminal extending out of the insulating layer of the input side outer winding casing, and the output side outer winding has an output terminal extending out of the insulating layer of the output side outer winding casing.

[0014] Furthermore, an inner shielding layer is provided between the input-side inner winding and the input-side insulating support member, and between the output-side inner winding and the output-side insulating support member.

[0015] Furthermore, the core assembly is a rectangular core, and the first core column and the second core column are located on the two long sides of the rectangular core; the sub-transformer also includes: a first core clamp and a second core clamp that respectively clamp the two short sides of the rectangular core as the main support structure of the sub-transformer; and a shielding cover that is installed on the first core clamp and the second core clamp and surrounds the core assembly to form a shielding space.

[0016] Furthermore, the shielding cover includes four corner shielding covers, the main body of the corner shielding cover is L-shaped and has an arc structure at the corner position, and the four corner shielding covers are respectively connected to the two ends of the first core clamping plate and the two ends of the second core clamping plate.

[0017] Furthermore, terminal shielding rings are provided on the input terminal and the output terminal.

[0018] Furthermore, when there is one sub-transformer, the input-side external winding is connected to the input voltage, and the output-side external winding is connected to the first load;

[0019] When there are multiple sub-transformers, the input side external winding of the latter sub-transformer is connected to the output side external winding of the former sub-transformer.

[0020] Furthermore, the input-side inner winding or the output-side inner winding is connected to a second load.

[0021] Furthermore, the input side outer winding sleeve is cast by silicone rubber on the periphery of the input side outer winding and the input side insulating support, and the output side outer winding sleeve is cast by silicone rubber on the periphery of the output side outer winding and the output side insulating support.

[0022] Furthermore, the direction of the wiring port of the input terminal is opposite to the direction of the wiring port of the output terminal.

[0023] Furthermore, umbrella skirt structures located at both ends of the input side outer winding or the output side outer winding are respectively formed on the input side outer winding bushing and the output side outer winding bushing.

[0024] The technical solution of the present invention has the following advantages:

[0025] 1. The DC isolation transformer with a same iron core expandable structure provided by the present invention, the input side inner winding and the input side outer winding, the output side outer winding and the output side outer winding in the sub-transformer are all designed with the same iron core structure, and the two ends of the input side inner winding and the two ends of the output side inner winding are respectively connected, which can achieve double DC isolation of the insulation voltage, improve the insulation isolation capability of the sub-transformer, and overcome the problem of partial discharge of the main insulation; and multiple sub-transformers can be expanded in a cascade manner to achieve DC isolation of higher voltage levels.

[0026] 2. The DC isolation transformer with an expandable iron core structure provided by the present invention has a shielding cover arranged around the iron core assembly and a terminal shielding ring arranged on the output terminal and the output terminal, so as to achieve electric field optimization in a compact space.

[0027] 3. In the DC isolation transformer with the same iron core expandable structure provided by the present invention, the inner winding on the input side or the inner winding on the output side of the sub-transformer can be connected to a second load, so that the DC isolation transformer formed by cascading multiple sub-transformers can achieve multiple different outputs to meet the load requirements with different voltage isolation needs.

[0028] 4. In the DC isolation transformer with an expandable iron core structure provided by the present invention, a shielding structure is arranged on the periphery of the inner winding to balance the interface transition electric field. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A top view of a DC isolation transformer with the same iron core provided in an embodiment of the present invention;

[0031] Figure 2 A rear view of a DC isolation transformer with the same iron core provided by an embodiment of the present invention;

[0032] Figure 3 A schematic diagram of the overall structure of a DC isolation transformer with an iron core provided in an embodiment of the present invention, in which a portion has been cut away to show its internal structure;

[0033] Figure 4 An electrical schematic diagram of a DC isolation transformer with an iron core provided in an embodiment of the present invention;

[0034] Figure 5 An electrical schematic diagram of an expandable structure of a DC isolation transformer with the same iron core provided by an embodiment of the present invention;

[0035] Figure 6 This is an electrical schematic diagram of a load connected to the inner winding of an iron-core DC isolation transformer provided by an embodiment of the present invention.

[0036] Explanation of the accompanying drawings: 1. Core assembly; 11. First core column; 12. Second core column; 2. Input side winding; 21. Input side inner winding; 22. Input side insulating support; 23. Input side outer winding; 24. Input side outer winding bushing; 25. Input terminal; 3. Output side winding; 31. Output side inner winding; 32. Output side insulating support; 33. Output side outer winding; 34. Output side outer winding bushing; 35. Output terminal; 4. Inner shielding layer; 5. First core clamp; 6. Second core clamp; 7. Shielding cover; 8. Terminal shielding ring; 9. Umbrella skirt structure. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] 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.

[0041] like Figure 1 A DC isolation transformer with a core expandable structure shown in FIG. 6 is composed of a plurality of sub-transformers connected in a cascade form. The number of cascades depends on the voltage level of the application. The voltage level of the sub-transformer can be flexibly designed from tens of kilovolts to hundreds of kilovolts. The sub-transformer includes a core assembly 1, an input side winding 2, and an output side winding 3. The core assembly 1 includes two parallel first core columns 11 and second core columns 12, and the first core column 11 and the second core column 12 both have an axis.

[0042] The input side winding 2 includes an input side inner winding 21 sleeved on the first core column 11, an input side outer winding sleeve 24 sleeved on the outer periphery of the input side inner winding 21, and an input side insulating support 22 located between the input side inner winding 21 and the input side outer winding sleeve 24, and the input side outer winding sleeve 24 is wrapped with an input side outer winding 23.

[0043] The output side winding includes an output side inner winding 31 sleeved on the second core column 12, an output side outer winding sleeve 34 sleeved on the outer periphery of the output side inner winding 31, and an output side insulating support 32 located between the output side inner winding 31 and the output side outer winding sleeve 34, wherein the output side outer winding sleeve 34 wraps the output side outer winding 33.

[0044] The two ends of the input side inner winding 21 and the two ends of the output side inner winding 31 are connected respectively, thereby forming a loop for transmitting energy. The input side outer winding bushing 24 and the output side outer winding bushing 34 are respectively used to achieve insulation isolation of the input side outer winding 23 and the output side outer winding 33 from external components. The input side insulating support 22 is used to achieve insulation isolation of the input side outer winding 23 and the input side inner winding 21, and the output side insulating support 32 is used to achieve insulation isolation of the output side outer winding 33 and the output side inner winding 31. The input side outer winding 23 has an input terminal 25 extending out of the insulation layer of the input side outer winding bushing 24, and the output side outer winding 33 has an output terminal 35 extending out of the insulation layer of the input side outer winding bushing 24, the input terminal 25 is connected to the external input voltage, and the output terminal 35 is connected to the load.

[0045] In this sub-transformer adopting the same iron core structure, the input side inner winding 21 and the input side outer winding 23, the output side outer winding 33 and the output side outer winding 33 all adopt the same iron core structure design, and the two ends of the input side inner winding 21 and the two ends of the output side inner winding 31 are respectively connected to form a loop, which can improve the insulation isolation capability of the sub-transformer; and a plurality of sub-transformers can be expanded in a cascade manner to achieve DC isolation of a higher voltage level.

[0046] In this embodiment, an inner shielding layer 4 is provided between the input side inner winding 21 and the input side insulating support 22, and between the input side inner winding 21 and the output side insulating support 32. The provision of the inner shielding layer 4 can balance the transition electric field at the interface between the input side inner winding 21 and the input side inner winding 21.

[0047] In this embodiment, the core assembly 1 is a rectangular core, and the first core column 11 and the second core column 12 are located on the two long sides of the rectangular core. The sub-transformer also includes: a first core clamp 5 and a second core clamp 6 that clamp the two short sides of the rectangular core as the main support structure of the sub-transformer; and a shielding cover 7 that is installed on the first core clamp 5 and the second core clamp 6 and surrounds the core assembly 1 to form a shielding space. The setting of the shielding cover 7 can achieve the optimization of the electric field in a compact space.

[0048] Specifically, the shielding cover 7 is composed of four corner shielding covers 7, the main body of the corner shielding cover 7 is L-shaped and has an arc structure at the corner position, and the four corner shielding covers 7 are respectively connected to the two ends of the first core clamping plate 5 and the two ends of the second core clamping plate 6. In some embodiments, the shielding cover 7 can also be a structure surrounded by four sides and hollowed in the middle.

[0049] In this embodiment, in order to avoid partial discharge problems at the connection points between the input terminal 25 and the output terminal 35 and the external wiring, terminal shielding rings 8 are provided on both the input terminal 25 and the output terminal 35 .

[0050] In this embodiment, when the DC isolation transformer is composed of only one sub-transformer, the input side external winding 23 of the sub-transformer is connected to the input voltage, and the output side external winding 33 is connected to the first load. When the DC isolation transformer is composed of multiple sub-transformers in cascade, the input side external winding 23 of the latter sub-transformer is connected to the output side external winding 33 of the former sub-transformer. This sub-transformer scalable structural design can achieve DC isolation of higher voltage levels.

[0051] In some implementations of this embodiment, a second load may be connected to the input-side inner winding 21 or the output-side inner winding 31 , so as to meet the multi-channel different output requirements of the DC isolation transformer.

[0052] In this embodiment, the input side outer winding sleeve 24 is cast by silicone rubber on the outer periphery of the input side outer winding 23 and the input side insulating support 22, and the output side outer winding sleeve 34 is cast by silicone rubber on the outer periphery of the output side outer winding 33 and the output side insulating support 32. The input side outer winding sleeve 24 and the output side outer winding sleeve 34 are cast by silicone rubber, and the transformer winding for energy transmission can be wrapped in the insulating sleeve to achieve insulation isolation between the transformer winding and external components, which can solve the problem of charge accumulation and partial discharge of the insulating sleeve under long-term DC voltage, and achieve the reliability of transformer energy transmission and insulation isolation.

[0053] In this embodiment, the connection port direction of the input terminal 25 is opposite to the connection port direction of the output terminal 35. This arrangement facilitates the cascade connection of multiple sub-transformers in a longitudinal manner, and facilitates the optimization of the electric field arrangement in a limited space.

[0054] In this embodiment, an umbrella skirt structure 9 located at both ends of the input side outer winding 23 or the output side outer winding 33 is formed on the input side outer winding sleeve 24 and the output side outer winding sleeve 34, respectively. The setting of the umbrella skirt structure 9 increases the creepage distance per unit length and reduces the volume and size of the input side outer winding sleeve 24 and the output side outer winding sleeve 34. Specifically, the umbrella skirt structure 9 includes two large umbrella skirts and small umbrella skirts with different diameters, and the large umbrella skirts and the small umbrella skirts are arranged alternately. This umbrella skirt structure 9 increases the distance between the large umbrella skirt and the small umbrella skirt, which can effectively prevent sewage or icicles formed in rainy and snowy weather from causing equipment failures, ensure power supply reliability, and has a simple structure and is easy to implement. In some embodiments, the umbrella skirt structure 9 can also include three or more umbrella skirts with different diameters.

[0055] In summary, in the DC isolation transformer with a same-core expandable structure provided in an embodiment of the present invention, the input side inner winding 21 and the input side outer winding 23, the output side outer winding 33 and the output side outer winding 33 in the sub-transformer all adopt the same-core structure design, and the two ends of the input side inner winding 21 and the two ends of the output side inner winding 31 are respectively connected, which can achieve double DC isolation of the insulation voltage, thereby improving the insulation isolation capability of the sub-transformer; and multiple sub-transformers can be expanded in a cascade manner to achieve DC isolation of a higher voltage level; in addition, a load can be connected to the input side inner winding 21, so that multiple different outputs can be achieved to meet the load requirements of different voltage isolation requirements.

[0056] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A DC isolation transformer with an expandable iron core structure, characterized in that: It is composed of several sub-transformers connected in cascade form, and the sub-transformers include: An iron core assembly (1) comprises a first iron core column (11) and a second iron core column (12); An input side winding (2), comprising an input side inner winding (21) sleeved on the first core column (11), an input side outer winding sleeve (24) sleeved on the outer periphery of the input side inner winding (21), and an input side insulating support member (22) located between the input side inner winding (21) and the input side outer winding sleeve (24), wherein the input side outer winding sleeve (24) is wrapped with an input side outer winding (23); An output side winding (3), comprising an output side inner winding (31) sleeved on the second core column (12), an output side outer winding sleeve (34) sleeved on the outer periphery of the output side inner winding (31), and an output side insulating support member (32) located between the output side inner winding (31) and the output side outer winding sleeve (34), wherein the output side outer winding sleeve (34) is wrapped with the output side outer winding (33); The two ends of the input side inner winding (21) and the two ends of the output side inner winding (31) are respectively connected to form a loop for transmitting energy; the input side outer winding (23) has an input terminal (25) extending out of the insulating layer of the input side outer winding sleeve (24), and the output side outer winding (33) has an output terminal (35) extending out of the insulating layer of the output side outer winding sleeve (34); When there is one sub-transformer, the input-side external winding (23) is connected to an input voltage, and the output-side external winding (33) is connected to a first load; When there are multiple sub-transformers, the input side outer winding (23) of the latter sub-transformer is connected to the output side outer winding (33) of the former sub-transformer; the input side inner winding (21) or the output side inner winding (31) is connected to a second load; The input side outer winding sleeve (24) is cast by silicone rubber on the outer periphery of the input side outer winding (23) and the input side insulating support (22), and the output side outer winding sleeve (34) is cast by silicone rubber on the outer periphery of the output side outer winding (33) and the output side insulating support (32).

2. The DC isolation transformer with an expandable iron core structure according to claim 1, characterized in that: An inner shielding layer (4) is provided between the input-side inner winding (21) and the input-side insulating support member (22), and between the output-side inner winding (31) and the output-side insulating support member (32).

3. The DC isolation transformer with an expandable iron core structure according to claim 1 or 2, characterized in that: The iron core assembly (1) is a rectangular iron core, and the first iron core column (11) and the second iron core column (12) are located on the two long sides of the rectangular iron core; the sub-transformer also includes: a first iron core clamping plate (5) and a second iron core clamping plate (6) respectively clamping the two short sides of the rectangular iron core as the main body support structure of the sub-transformer; and a shielding cover (7) installed on the first iron core clamping plate (5) and the second iron core clamping plate (6) and surrounding the iron core assembly (1) to form a shielding space.

4. The DC isolation transformer with an expandable iron core structure according to claim 3, characterized in that: The shielding cover (7) comprises four corner shielding covers (7), the main body of the corner shielding cover (7) is L-shaped and has an arc-shaped structure at the corner position, and the four corner shielding covers (7) are respectively connected to the two ends of the first core clamping plate (5) and the two ends of the second core clamping plate (6).

5. The DC isolation transformer with an expandable iron core structure according to claim 1, characterized in that: The input terminal (25) and the output terminal (35) are both provided with a terminal shielding ring (8).

6. The DC isolation transformer with an expandable iron core structure according to claim 1, characterized in that: The direction of the connection port of the input terminal (25) is opposite to the direction of the connection port of the output terminal (35).

7. The DC isolation transformer with an expandable iron core structure according to claim 1, characterized in that: The input side outer winding sleeve (24) and the output side outer winding sleeve (34) are respectively provided with umbrella skirt structures (9) located at both ends of the input side outer winding (23) or the output side outer winding (33).

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