Low-current primary coil structure of oil-immersed current transformer
By using a combined structure of U-shaped aluminum tube and an insulating layer in an oil-immersed current transformer, the problem of difficult forming and fixing of small current primary coils is solved, and the effect of efficient forming, cost reduction and product quality is achieved.
Patent Information
- Application Number
- CN202421833290.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-31
- Publication Date
- 2025-05-09
- Estimated Expiration
- 2034-07-31
AI Technical Summary
In the prior art, due to the small specifications of primary wires required to make primary coils with smaller current specifications, the molding and fixing of primary coils are difficult to use mechanic bandages to make primary coils with smaller current specifications, and the manual bandaging efficiency is low, resulting in an increase in labor costs, time costs and product quality of the enterprise cannot be guaranteed.
A U-shaped aluminum tube sleeve is used to set on several primary conductors to form a U-shaped tubular structure, and a permeation hole is provided on the U-shaped aluminum tube. A U-shaped insulating layer sleeve is used to set on the U-shaped aluminum tube to form a primary coil, solving the problems of molding and fixing difficulties.
Through the combination of U-shaped aluminum tube and insulating layer, efficient molding and fixing of the primary coil is achieved, reducing labor and time costs, improving product quality, and ensuring complete soaking and bubble-free primary coil during oil immersion.
Smart Images
Figure CN222851251U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of current transformers, in particular to a small current primary coil structure of an oil-immersed current transformer. Background Art
[0002] The primary coil of the oil-immersed 110kV current transformer is usually a U-shaped structure. In order to meet the insulation performance requirements of the product, the U-shaped primary coil needs to be insulated and wrapped, and the wrapping methods include manual wrapping and machine wrapping. The current transformation ratio of the oil-immersed 110kV current transformer is different, and the material specifications used for its primary conductor are also different. The conventional primary current is usually 2*50-2*1250A, and the primary conductor specifications required to meet the above primary current are also larger. The machine wrapping method can be used to wrap multiple primary conductors to form a primary coil.
[0003] However, with the changes in the market, the market's required specifications for primary current have become smaller, and currents of 2A, 5A, 10A and other specifications must be met. Therefore, the specifications of the primary wires are smaller, and the forming and fixing of the primary coils are difficult. It is impossible to use the machine wrapping method to wrap multiple smaller primary wires to form a primary coil. The manual wrapping method is labor-intensive and inefficient, resulting in an increase in the company's labor and time costs, and the quality of the primary coil products cannot be guaranteed. Utility Model Content
[0004] The purpose of the embodiments of the present application is to provide a small current primary coil structure of an oil-immersed current transformer, which is used to solve the technical problems in the prior art that the primary wire required to make the primary coil with a smaller current specification is small, the primary coil is difficult to form and fix, resulting in the inability to use a machinist's wrapping method to make the primary coil with a smaller current specification, and the manual wrapping of the primary coil with a smaller current specification leads to increased labor costs and time costs for the enterprise and the inability to guarantee product quality.
[0005] To achieve the above objectives, the present application embodiment adopts the following technical solutions:
[0006] A small current primary coil structure of an oil-immersed current transformer, comprising a plurality of primary conductors, a U-shaped aluminum tube and a U-shaped insulating layer;
[0007] The plurality of primary conductors all pass through the first end of the U-shaped aluminum tube to the second end of the U-shaped aluminum tube, the first end of the primary conductor is located outside the first end of the U-shaped aluminum tube, the second end of the primary conductor is located outside the second end of the U-shaped aluminum tube, the first end and the second end of the primary conductor are connected to each other to form a conductor loop, and the primary conductor is a 1.8mm*3mm paper-covered copper rectangular wire;
[0008] A plurality of penetration holes are provided on two inner side surfaces opposite to the first end of the U-shaped aluminum tube and the second end of the U-shaped aluminum tube, and the penetration holes are connected to the inside of the U-shaped aluminum tube and the outside;
[0009] The insulating layer is sleeved outside the U-shaped aluminum tube.
[0010] In a small current primary coil structure of an oil-immersed current transformer described in an embodiment of the present application, the U-shaped aluminum tube includes at least two arc-shaped U-shaped grooves and a binding band;
[0011] At least two of the arc-shaped U-shaped grooves are connected end to end to form a U-shaped tubular structure, and the binding belt is wound around the outside of the U-shaped tubular structure to form the U-shaped aluminum tube.
[0012] In the small current primary coil structure of an oil-immersed current transformer described in an embodiment of the present application, the number of the arc-shaped U-shaped grooves is two or four;
[0013] When the number of the arc-shaped U-shaped grooves is two, the arc of the arc section of each arc-shaped U-shaped groove is 180°;
[0014] When the number of the arc-shaped U-shaped grooves is four, the arc angle of the arc-shaped cross section of each arc-shaped U-shaped groove is 90°.
[0015] In the small current primary coil structure of an oil-immersed current transformer described in an embodiment of the present application, the outer diameter of the U-shaped aluminum tube is defined as D, and the wall thickness of the U-shaped aluminum tube is defined as t, then D=50mm and t=3mm are satisfied.
[0016] In a small current primary coil structure of an oil-immersed current transformer described in an embodiment of the present application, the number of the penetration holes is four, and the four penetration holes are evenly distributed on the two inner side surfaces opposite to the first end of the U-shaped aluminum tube and the second end of the U-shaped aluminum tube.
[0017] In the small current primary coil structure of an oil-immersed current transformer described in an embodiment of the present application, the aperture of the penetration hole is 10 mm.
[0018] In a small current primary coil structure of an oil-immersed current transformer described in an embodiment of the present application, the hole surface of the penetration hole is set to a smooth structure.
[0019] In the small current primary coil structure of an oil-immersed current transformer described in an embodiment of the present application, the vertical distance between the penetration hole and its own forming line located at the same end of the U-shaped aluminum tube is 50mm to 100mm, wherein the forming line is the intersection of the vertical section and the curved section of the U-shaped aluminum tube.
[0020] In a small current primary coil structure of an oil-immersed current transformer described in an embodiment of the present application, the U-shaped insulating layer includes a U-shaped insulating corrugated paper layer and a U-shaped insulating cable paper layer;
[0021] The U-shaped insulating corrugated paper layer is sleeved on the outside of the U-shaped aluminum tube, and a plurality of first aluminum foils are sleeved on the outside of the U-shaped insulating corrugated paper layer at equal intervals along the axial direction;
[0022] The U-shaped insulating cable paper layer is sleeved on the outside of the U-shaped insulating corrugated paper layer and fully covers the first aluminum foils. The inside of the U-shaped insulating cable paper layer is provided with a plurality of second aluminum foil groups arranged at equal intervals along the axial direction. Each of the second aluminum foil groups includes a plurality of second aluminum foils arranged at equal intervals along the radial direction of the U-shaped insulating cable paper layer.
[0023] In the small current primary coil structure of an oil-immersed current transformer described in an embodiment of the present application, it also includes a zero screen lead wire and an end screen lead wire;
[0024] One end of the zero-shield lead is connected to the first aluminum foil, and the other end is connected to the high-voltage terminal of the current transformer;
[0025] One end of the end screen lead wire is connected to the second aluminum foil away from the U-shaped insulating corrugated paper layer, and the other end is grounded.
[0026] Compared with the prior art, the embodiments of the present application have the following beneficial effects:
[0027] 1. A small current primary coil structure of an oil-immersed current transformer provided in an embodiment of the present application, by sleeve-mounting a U-shaped aluminum tube on a number of primary conductors, is equivalent to adding a layer of "shell for easy shaping" to the number of primary conductors with the U-shaped aluminum tube, and replaces a primary coil forming method in which a U-shaped insulating layer is directly sleeved on a number of primary conductors with a primary coil forming method in which a U-shaped insulating layer is sleeved on the U-shaped aluminum tube. This solves the technical problems in the prior art that the primary wire required for making a primary coil with a smaller current specification is small, the molding and fixing of the primary coil are difficult, resulting in the inability to use a machinist's wrapping method to make a primary coil with a smaller current specification, and the manual wrapping of the primary coil with a smaller current specification leads to an increase in the company's labor cost and time cost, and the inability to guarantee product quality. At the same time, a penetration hole is set on the U-shaped aluminum tube to ensure that the primary coil is completely soaked and free of bubbles when immersed in oil.
[0028] 2. The oil immersion efficiency of the primary coil is improved by arranging a U-shaped aluminum tube consisting of at least two arc-shaped U-shaped grooves and a binding band.
[0029] 3. By setting the outer diameter of the U-shaped aluminum tube to 50 mm and the tube wall thickness to 3 mm, the volume inside the U-shaped aluminum tube is guaranteed and the required strength of the U-shaped aluminum tube is met.
[0030] 4. By setting the hole surface of the penetration hole to a smooth structure, the influence of the penetration hole on the partial discharge of the primary coil is reduced.
[0031] 5. By setting the vertical distance between the penetration hole and the forming line at the same end of the U-shaped aluminum tube to 50mm to 100mm, the oil immersion effect of the primary coil is guaranteed and the U-shaped aluminum tube is prevented from breaking due to stress. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. The drawings are not intended to be drawn to scale, and for the sake of clarity, not every component will be marked in each figure. The drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. Among them:
[0033] Figure 1 It is a schematic diagram of the structure of an embodiment of the present application (excluding the U-shaped insulating layer).
[0034] Figure 2 It is a side view of an embodiment of the present application.
[0035] Figure 3 for Figure 2 A is a partial enlarged schematic diagram of the middle part.
[0036] Figure 4 It is a cross-sectional view of the U-shaped insulating layer (excluding the zero-screen lead wire and the end-screen lead wire) in the embodiment of the present application.
[0037] Description of reference numerals:
[0038] 10-primary conductor, 20-U-shaped aluminum tube, 21-penetration hole, 22-arc-shaped U-shaped groove, 23-binding tape, 24-molding wire, 30-U-shaped insulation layer, 31-U-shaped insulation corrugated paper layer, 32-first aluminum foil, 33-U-shaped insulation cable paper layer, 331-second aluminum foil, 34-zero-screen lead-out wire, 35-last-screen lead-out wire. DETAILED DESCRIPTION
[0039] Since it is difficult to form and fix a primary coil with a smaller primary conductor, it is not possible to use a machine-wrapped method to wrap multiple smaller primary conductors to form a primary coil. The manual wrapping method is labor-intensive and inefficient, resulting in an increase in the company's labor and time costs, and the quality of the primary coil products cannot be guaranteed.
[0040] In view of this, an embodiment of the present application provides a small current primary coil structure of an oil-immersed current transformer, the concept of which is to sleeve a U-shaped aluminum tube on a number of primary conductors, which is equivalent to adding a layer of "easy-to-shape shell" to the several primary conductors with the U-shaped aluminum tube, and replace the primary coil forming method in which the U-shaped insulation layer is directly sleeved on the several primary conductors with a primary coil forming method in which the U-shaped insulation layer is sleeved on the U-shaped aluminum tube. This solves the technical problems in the prior art that the primary wire required for making a primary coil with a smaller current specification is small, the molding and fixing of the primary coil are difficult, and the primary coil with a small current specification cannot be made by a machinist wrapping method, and the manual wrapping of the primary coil with a small current specification leads to increased labor costs and time costs of the enterprise and the inability to guarantee product quality. At the same time, a penetration hole is set on the U-shaped aluminum tube to ensure that the primary coil is completely soaked and free of bubbles when immersed in oil.
[0041] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.
[0042] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application 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 a limitation on the present application. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.
[0043] In the description of this application, 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, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0044] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.
[0045] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the various specific processes and material examples provided by the present application, but those of ordinary skill in the art can appreciate the application of other processes and / or the use of other materials.
[0046] The present application embodiment provides a small current primary coil structure of an oil-immersed current transformer, such as Figures 1 to 4 A small current primary coil structure of an oil-immersed current transformer includes a plurality of primary conductors 10, a U-shaped aluminum tube 20 and a U-shaped insulating layer 30.
[0047] The plurality of primary conductors 10 all pass through the first end of the U-shaped aluminum tube 20 to the second end of the U-shaped aluminum tube 20, the first end of the primary conductor 10 is located outside the first end of the U-shaped aluminum tube 20, the second end of the primary conductor 10 is located outside the second end of the U-shaped aluminum tube 20, the first end and the second end of the primary conductor 10 are interconnected to form a conductor loop, and the primary conductor 10 is a 1.8mm*3mm paper-covered copper rectangular wire.
[0048] Specifically, the U-shaped aluminum tube 20 includes at least two arc-shaped U-shaped grooves 22 and a binding band 23. At least two of the arc-shaped U-shaped grooves 22 are connected end to end to form a U-shaped tubular structure. The binding band 23 is wrapped around the outside of the U-shaped tubular structure to form the U-shaped aluminum tube 20. In this embodiment, the number of the arc-shaped U-shaped grooves 22 is two or four. When the number of the arc-shaped U-shaped grooves 22 is two, the curvature of the arc-shaped cross-section of each of the arc-shaped U-shaped grooves 22 is 180°. When the number of the arc-shaped U-shaped grooves 22 is four, the curvature of the arc-shaped cross-section of each of the arc-shaped U-shaped grooves 22 is 90°. The outer diameter of the U-shaped aluminum tube 20 is defined as D, and the tube wall thickness of the U-shaped aluminum tube 20 is t, then D=50mm and t=3mm are satisfied.
[0049] Among them, the first end and the second end of the primary conductor 10 are connected by welding, the U-shaped aluminum tube 20 includes two vertical sections and one curved section, the first end of the U-shaped aluminum tube 20 and the second end of the U-shaped aluminum tube 20 are two vertical sections respectively, and the U-shaped aluminum tube 20 is arranged to be composed of at least two of the arc-shaped U-shaped grooves 22 and the binding band 23 in order to improve the oil immersion efficiency of the primary coil, and the outer diameter of the U-shaped aluminum tube 20 is set to 50 mm and the tube wall thickness is set to 3 mm in order to ensure the volume in the U-shaped aluminum tube 20 while meeting the strength required by the U-shaped aluminum tube 20, and the arc-shaped U-shaped groove 22 is obtained by cutting the U-shaped aluminum tube into equal parts, such as, when the U-shaped aluminum tube 20 is composed of two of the arc-shaped U-shaped grooves 22 and the binding band 23, the two arc-shaped U-shaped grooves 22 are obtained by cutting the U-shaped aluminum tube along the plane where the central axis of the U-shaped aluminum tube is located.
[0050] A plurality of penetration holes 21 are provided on two inner side surfaces opposite to the first end of the U-shaped aluminum tube 20 and the second end of the U-shaped aluminum tube 20 , and the penetration holes 21 connect the inside of the U-shaped aluminum tube 20 with the outside.
[0051] Specifically, the number of the penetration holes 21 is four, and the four penetration holes 21 are evenly distributed on the two inner side surfaces opposite to the first end of the U-shaped aluminum tube 20 and the second end of the U-shaped aluminum tube 20. The aperture of the penetration hole 21 is 10 mm, and the hole surface of the penetration hole 21 is set to a smooth structure. The vertical distance between the penetration hole 21 and the forming line 24 located at the same end of the U-shaped aluminum tube 20 is 50 mm to 100 mm, and the forming line 24 is the intersection of the vertical section and the curved section of the U-shaped aluminum tube 20.
[0052] Among them, by setting the hole surface of the penetration hole 21 to a smooth structure, the influence of the penetration hole 21 on the local discharge of the sequential coil is reduced. By setting the vertical distance between the penetration hole 21 and the molding line 24 located at the same end of the U-shaped aluminum tube 20 to 50mm-100mm, the oil immersion effect of the primary coil is guaranteed, and the U-shaped aluminum tube 20 can be prevented from breaking due to stress. There are two molding lines 24 on the U-shaped aluminum tube 20, which are respectively located at the connection between the two vertical sections and the curved section of the U-shaped aluminum tube. The penetration hole 21 located at the first end of the U-shaped aluminum tube 20 is 50mm-100mm away from the molding line 24 at the connection between the first end of the U-shaped aluminum tube 20 and the curved section of the U-shaped aluminum tube 20. The penetration hole 21 located at the second end of the U-shaped aluminum tube 20 is 50mm-100mm away from the molding line 24 at the connection between the second end of the U-shaped aluminum tube 20 and the curved section of the U-shaped aluminum tube 20. Figure 1 As shown, Figure 1 The molding line 24 in the figure is not a real line, but is for the convenience of intuitive description.
[0053] The U-shaped insulating layer 30 is sleeved outside the U-shaped aluminum tube 20 .
[0054] Specifically, the U-shaped insulating layer 30 includes a U-shaped insulating corrugated paper layer 31, a U-shaped insulating cable paper layer 33, a zero-screen lead-out wire 34 and an end-screen lead-out wire 35. The U-shaped insulating corrugated paper layer 31 is sleeved on the outside of the U-shaped aluminum tube 20. The U-shaped insulating corrugated paper layer 31 is sleeved with a plurality of first aluminum foils 32 at equal intervals along its axial direction. The U-shaped insulating cable paper layer 33 is sleeved on the outside of the U-shaped insulating corrugated paper layer 31 and fully covers the plurality of first aluminum foils 32. A plurality of second aluminum foil groups are arranged at equal intervals along the axial direction inside the U-shaped insulating cable paper layer 33. Each of the second aluminum foil groups includes a plurality of second aluminum foils 331 arranged at equal intervals along the radial direction of the U-shaped insulating cable paper layer 33. One end of the zero-screen lead-out wire 34 is connected to the first aluminum foil 32, and the other end is connected to the high-voltage terminal of the current transformer. One end of the end-screen lead-out wire 35 is connected to the second aluminum foil 331 away from the U-shaped insulating corrugated paper layer 31, and the other end is grounded.
[0055] In summary, the small current primary coil structure of an oil-immersed current transformer provided in the embodiment of the present application, by sleeve-mounting a U-shaped aluminum tube on a number of primary conductors, is equivalent to adding a layer of "easy-to-shape shell" to the number of primary conductors with the U-shaped aluminum tube, and replaces the primary coil forming method in which the U-shaped insulating layer is directly sleeved on the number of primary conductors with a primary coil forming method in which the U-shaped insulating layer is sleeved on the U-shaped aluminum tube, thereby solving the problem in the prior art that the primary wire required for making a primary coil with a smaller current specification is small, the primary coil is difficult to form and fix, resulting in the inability to use a machinist's wrapping method to make a primary coil with a smaller current specification, and the increase in the company's labor cost and time cost and the quality of the product due to the manual wrapping of the primary coil with a smaller current specification. The technical problem that the quantity cannot be guaranteed is solved, and by setting the penetration hole on the U-shaped aluminum tube, it can be ensured that the primary coil is completely soaked in oil without bubbles; at the same time, by setting the U-shaped aluminum tube to be composed of at least two arc-shaped U-shaped grooves and a binding band, the oil immersion efficiency of the primary coil is improved; by setting the outer diameter of the U-shaped aluminum tube to 50 mm and the tube wall thickness to 3 mm, the volume in the U-shaped aluminum tube is guaranteed and the strength required by the U-shaped aluminum tube is met; by setting the hole surface of the penetration hole to a smooth structure, the influence of the penetration hole on the local discharge of the primary coil is reduced; by setting the vertical distance between the penetration hole and its own forming line at the same end of the U-shaped aluminum tube to 50 mm to 100 mm, the oil immersion effect of the primary coil is guaranteed and the U-shaped aluminum tube can be prevented from breaking due to stress.
[0056] The above is a detailed introduction to the small current primary coil structure of an oil-immersed current transformer provided in an embodiment of the present application. This article uses specific examples to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solution and core idea of the present application; ordinary technicians in this field should understand that: they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the present application.
Claims
1. A small current primary coil structure of an oil-immersed current transformer, characterized in that: It includes a number of primary conductors, a U-shaped aluminum tube and a U-shaped insulating layer; The plurality of primary conductors all pass through the first end of the U-shaped aluminum tube to the second end of the U-shaped aluminum tube, the first end of the primary conductor is located outside the first end of the U-shaped aluminum tube, the second end of the primary conductor is located outside the second end of the U-shaped aluminum tube, the first end and the second end of the primary conductor are connected to each other to form a conductor loop, and the primary conductor is a 1.8mm*3mm paper-covered copper rectangular wire; A plurality of penetration holes are provided on two inner side surfaces opposite to the first end of the U-shaped aluminum tube and the second end of the U-shaped aluminum tube, and the penetration holes are connected to the inside of the U-shaped aluminum tube and the outside; The U-shaped insulating layer is sleeved outside the U-shaped aluminum tube.
2. The small current primary coil structure of an oil-immersed current transformer according to claim 1, characterized in that: The U-shaped aluminum tube includes at least two arc-shaped U-shaped grooves and a binding strap; At least two of the arc-shaped U-shaped grooves are connected end to end to form a U-shaped tubular structure, and the binding belt is wound around the outside of the U-shaped tubular structure to form the U-shaped aluminum tube.
3. The small current primary coil structure of an oil-immersed current transformer as claimed in claim 2, characterized in that: The number of the arc-shaped U-shaped grooves is two or four; When the number of the arc-shaped U-shaped grooves is two, the arc of the arc section of each arc-shaped U-shaped groove is 180°; When the number of the arc-shaped U-shaped grooves is four, the arc angle of the arc-shaped cross section of each arc-shaped U-shaped groove is 90°.
4. The small current primary coil structure of an oil-immersed current transformer according to claim 1, characterized in that: Define the outer diameter of the U-shaped aluminum tube as D, and the wall thickness of the U-shaped aluminum tube as t, then D=50 mm, and t=3 mm.
5. The small current primary coil structure of an oil-immersed current transformer according to claim 1, characterized in that: The number of the penetration holes is four, and the four penetration holes are evenly distributed on two inner side surfaces opposite to the first end of the U-shaped aluminum tube and the second end of the U-shaped aluminum tube.
6. The small current primary coil structure of an oil-immersed current transformer according to claim 1, characterized in that: The diameter of the penetration hole is 10 mm.
7. The small current primary coil structure of an oil-immersed current transformer according to claim 1, characterized in that: The hole surface of the penetration hole is set to a smooth structure.
8. The small current primary coil structure of an oil-immersed current transformer according to claim 1, characterized in that: The vertical distance between the penetration hole and its own forming line located at the same end of the U-shaped aluminum tube is 50mm to 100mm, wherein the forming line is the intersection of the vertical section and the curved section of the U-shaped aluminum tube.
9. The small current primary coil structure of an oil-immersed current transformer according to claim 1, characterized in that: The U-shaped insulating layer comprises a U-shaped insulating corrugated paper layer and a U-shaped insulating cable paper layer; The U-shaped insulating corrugated paper layer is sleeved on the outside of the U-shaped aluminum tube, and the U-shaped insulating corrugated paper layer is sleeved with a plurality of first aluminum foils at equal intervals along the axial direction thereof; The U-shaped insulating cable paper layer is sleeved on the outside of the U-shaped insulating corrugated paper layer and fully covers the first aluminum foils. The inside of the U-shaped insulating cable paper layer is provided with a plurality of second aluminum foil groups arranged at equal intervals along the axial direction. Each of the second aluminum foil groups includes a plurality of second aluminum foils arranged at equal intervals along the radial direction of the U-shaped insulating cable paper layer.
10. The small current primary coil structure of an oil-immersed current transformer according to claim 9, characterized in that: The U-shaped insulating layer also includes a zero-screen lead-out line and an end-screen lead-out line; One end of the zero-shield lead is connected to the first aluminum foil, and the other end is connected to the high-voltage terminal of the current transformer; One end of the end screen lead wire is connected to the second aluminum foil away from the U-shaped insulating corrugated paper layer, and the other end is grounded.