Support type large creepage distance current transformer
By designing a support-type large creepage current transformer, using epoxy resin vacuum casting and a skirt structure, the problems of small creepage and partial discharge of current transformers in high-altitude areas are solved, realizing high-precision current measurement and anti-theft functions, which is suitable for high-altitude power systems.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- DALIAN NORTH INSTR TRANSFORMER GROUP
- Filing Date
- 2025-05-23
- Publication Date
- 2026-04-24
AI Technical Summary
The current transformers in existing 35kV switchgear in high-altitude areas have small surface creepage distances, low partial discharge qualification rates, and short product lifespans, posing a hidden danger to the safe operation of power system equipment.
Design a support-type large creepage current transformer, which adopts an epoxy resin vacuum casting structure, with an internal iron core and coil, an external umbrella skirt structure to increase the creepage distance, an internal equalizing mesh to ensure insulation and moisture protection, and a transparent secondary terminal design to prevent electricity theft.
It enables stable current measurement in high-altitude areas, improves product lifespan and partial discharge performance, prevents insulation degradation, and has moisture-proof, anti-condensation, and anti-theft functions. It has high metering accuracy and is suitable for high-altitude power systems.
Smart Images
Figure CN224164137U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to high-voltage measurement and protection devices for power systems, and in particular to a support-type large creepage current transformer. Background Technology
[0002] 35kV switchgear current transformers are devices used in solid-state switchgear of power systems to measure current, electrical energy, or for relay protection. Currently, the current transformers used in switchgear of power systems are generally used at altitudes below 1000 meters. They have relatively small surface creepage distances and have disadvantages such as easy discharge, short service life, and low partial discharge qualification rate. As the service time increases, the product performance deteriorates to varying degrees in terms of insulation performance, partial discharge, and other electrical performance, becoming a hidden danger to the safe operation of equipment in the power system. These problems have always plagued power system designers and maintenance personnel, and have become urgent issues to be solved in the upgrading, transformation, and development of current transformers for 35kV switchgear at high altitudes of 4000 meters in power systems. Utility Model Content
[0003] To address the aforementioned problems, the purpose of this utility model is to provide a support-type large creepage current transformer to solve the problems of small surface creepage, low partial discharge qualification rate, and short product life in existing 35kV switchgear at 4000 meters above sea level in high-altitude areas.
[0004] To achieve the above objectives, the present invention adopts the following technical solution:
[0005] This utility model provides a support-type large creepage current transformer, including an insulator and a coil body enclosed in the insulator. A primary terminal is provided on the top of the insulator, a secondary terminal is provided on the bottom front side of the insulator, an umbrella skirt structure is provided on the outer surface of the insulator between the primary terminal and the secondary terminal, and a front equalizing grid and a rear equalizing grid are provided at the lower inner end of the insulator.
[0006] The coil body includes an iron core, a primary winding, and a secondary winding. The iron core is wrapped from the inside out with a layer of cardboard corner rings, a layer of polyurethane board, a half-layer of twill tape, a half-layer of polyester film, and two half-layers of PVC tape. The secondary winding is wound around the iron core, and its bottom is supported by a secondary winding bracket. Both axial ends of the secondary winding are padded with an insulating cardboard sheet and two half-layers of polyester film. The secondary winding's secondary wire layers are separated by a half-layer of polyester film, and the outer half-layer of the secondary winding... The first layer consists of a semi-conductive crepe paper, under which a long strip of shielding copper foil is pressed. Copper braided wire is welded to the end of the shielding copper foil. The copper braided wire and the semi-conductive crepe paper are interlaced and overlapped. The copper braided wire is fitted with a high-voltage inner tubing and led out from the non-out-of-wire side of the secondary winding. The copper braided wire is connected to the back equalizing mesh. The outermost layer of the secondary winding is wrapped with two layers of semi-conductive crepe paper and a half-overlapping layer of protective yellow crepe paper. The primary winding passes through the middle of the secondary winding and is independently wound. The outer side of the primary winding is wrapped with polyurethane board and semi-conductive crepe paper.
[0007] The umbrella skirt structure includes vertical umbrella skirts located on both sides of the top of the insulator and multiple horizontal umbrella skirts located on the side surface of the insulator. The indentation between adjacent horizontal umbrella skirts increases in a stepwise gradient from the middle position of the insulator to the upper and lower ends.
[0008] The upper and lower parts of the insulator are a small square prism and a large square prism, respectively, with a sloping transition between the two.
[0009] The front equalizing mesh has an L-shaped structure, and its bottom is connected to the mounting insert located at the front end of the bottom of the insulator via copper wire.
[0010] The four edges of the front equalizing mesh are all fitted with spring-shaped copper wires.
[0011] The rear equalizing mesh is arranged horizontally, and its two ends are connected to the mounting insert located at the bottom rear end of the insulator by copper wires.
[0012] The two ends of the primary winding are the beginning end and the end end of the primary winding, respectively. The beginning end of the primary winding is connected to the P1 end of the primary terminal block through a primary connecting plate, and the end end of the primary winding is directly connected to the P2 end of the primary terminal block. Both the P1 and P2 ends of the primary terminal block are flat plate structures.
[0013] The bottom of the insulator is a shrinkable structure, the secondary wiring terminal is located on the front side of the shrinkable structure, and a secondary wiring cover is provided on the outside of the secondary wiring terminal.
[0014] The bottom of the insulator is provided with a mounting base plate, which is provided with grounding bolts and mounting holes.
[0015] The insulator is made of epoxy resin as a single structure, and the shortest surface distance between the primary terminal of the primary winding and the secondary terminal of the secondary winding is the maximum surface creepage distance for high voltage and low voltage.
[0016] This utility model has the following advantages and beneficial effects:
[0017] 1. Small size and flexible installation: This utility model is made of epoxy resin vacuum casting and has a large creepage distance structure. The iron core is sealed inside the insulating material. With optimized structural design, the product can be used in areas with an altitude of 4000 meters. Moreover, the product is small in size, light in weight, has good partial discharge effect, and long service life. It can be flexibly installed in 35kV switchgear for current and energy metering and relay protection.
[0018] 2. High dynamic and thermal stability current and high metering accuracy: The primary dynamic and thermal stability current of this utility model is high, which can effectively avoid excessive temperature rise and insulation damage of the current transformer caused by system short circuit and overcurrent; the metering coil can be made in the form of complex ratio, and the metering accuracy can reach the 0.2S level, effectively ensuring the accuracy of the product under wide load and large load changes.
[0019] 3. Fully sealed, moisture-proof, and anti-condensation: The entire structure of this utility model is made of epoxy resin vacuum casting. The external design has a large surface creepage distance, and all internal components are sealed inside insulating materials to ensure that the product has moisture-proof and anti-condensation functions. The product will not experience performance degradation due to the humidity or condensation in the operating environment.
[0020] 4. Transparency to prevent electricity theft: The secondary wiring terminals of this utility model are located inside a secondary wiring cover made of transparent material, which allows for easy and direct observation of the actual situation of the secondary wiring. The secondary wiring cover has a lead seal function, which not only prevents dust and moisture but also prevents electricity theft caused by switching secondary wires.
[0021] 5. Good partial discharge effect: This utility model has grounding grids designed at both the front and rear ends of the primary winding inside the insulator, which effectively shields the discharge phenomenon of the high potential of the primary winding to the low potential of the secondary winding and ground. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the internal structure of a support-type large creepage current transformer according to the present invention.
[0023] Figure 2 for Figure 1 Side view;
[0024] Figure 3 This is a schematic diagram of the external structure of a support-type large creepage current transformer according to the present invention.
[0025] Figure 4 for Figure 3 The left view;
[0026] Figure 5 for Figure 4 Enlarged view of a portion of point A in the middle;
[0027] Figure 6 for Figure 3 Top view;
[0028] Figure 7 This is a schematic diagram of the structure of the rear pressure equalization mesh in this utility model;
[0029] Figure 8 for Figure 7 Side view;
[0030] Figure 9 for Figure 7 Top view;
[0031] Figure 10 This is a schematic diagram of the front pressure equalization mesh in this utility model;
[0032] Figure 11 for Figure 10 The left view.
[0033] In the diagram: 1 is the insulator; 2 is the primary terminal; 3 is the end of the primary winding; 4 is the primary winding; 5 is the secondary winding; 6 is the rear equalizing mesh; 7 is the secondary terminal; 8 is the front equalizing mesh; 9 is the primary connecting plate; 10 is the mounting insert; 11 is the secondary winding bracket; 12 is the grounding bolt; 13 is the secondary terminal cover; 14 is the mounting base plate; 15 is the base plate mounting hole; 16 is the iron core; and 17 is the umbrella skirt structure. Detailed Implementation
[0034] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be described in detail below with reference to the accompanying drawings and specific embodiments.
[0035] See Figures 1 to 11As shown, this utility model provides a supported large creepage current transformer, including an insulator 1 and a coil body enclosed within the insulator 1. A primary terminal 2 is provided on the top of the insulator 1, and a secondary terminal 7 is provided on the bottom front side of the insulator 1. A large creepage umbrella structure 17 is provided on the outer surface of the insulator 1 between the primary terminal 2 and the secondary terminal 7. A front equalizing mesh 8 and a rear equalizing mesh 6 are provided at the lower inner end of the insulator 1. The coil body includes an iron core 16, a primary winding 4, and a secondary winding 5. The iron core 16 is wrapped from the inside out with a layer of cardboard corner ring, a layer of polyurethane board, a half-layer of twill tape, a half-layer of polyester film, and two half-layers of PVC tape. The secondary winding 5 is wound around the iron core 16, and the bottom of the secondary winding 5 is supported by a secondary winding bracket 11. An insulating cardboard sheet and two half-layers of polyester film are placed at both axial ends of the secondary winding 5. A half-layer of polyester film is placed between the secondary winding layers of the secondary winding 5. The outer side of the secondary winding 5... A semi-conductive crepe paper is half-stacked, and a long strip of shielding copper foil is pressed under the semi-conductive crepe paper. Copper braided wires are welded to the ends of the shielding copper foil. The copper braided wires are interlaced and overlapped with the semi-conductive crepe paper. The copper braided wires are fitted with high-voltage inner tubing and are led out from the non-out-of-wire side of the secondary winding 5, extending 300mm beyond the end face. After adjusting the distance between the primary winding 4 and the secondary winding 5 during molding, the copper braided wires are continuously and reliably connected to the mounting inserts 10 of the front equalizing mesh 8 and the rear equalizing mesh 6. The outermost layer of the secondary winding 5 is wrapped with... Two layers of semi-conductive crepe paper are wrapped around the primary winding 5. During the outer wrapping, the semi-conductive crepe paper is ensured to contact the secondary winding support 11. Finally, a protective layer of yellow crepe paper is half-lapped on top; this yellow crepe paper must be removed during molding. The primary winding 4 passes through the middle of the secondary winding 5 and is independently wound. Polyester tape is used on the outside of the primary winding 4 to tightly bind the primary wires, then polyurethane board is wrapped around it for buffering and heat resistance. Finally, semi-conductive crepe paper is wrapped around it to ensure a uniform electric field on the outside of the primary winding 4, which plays a crucial role in preventing partial discharge in the transformer. The two ends of the primary winding 4 are connected to the P1 and P2 terminals of the primary terminal 2, respectively. The secondary winding 5 is connected to the external secondary terminal 7 of the insulator.
[0036] See Figures 1 to 6 As shown in the embodiment of this utility model, the upper part and the lower part of the insulator 1 are small-sized square prisms and large-sized square prisms, respectively, and the small-sized square prisms and large-sized square prisms are connected by a slope transition.
[0037] See Figure 4 and Figure 5 As shown, in an embodiment of the present invention, the umbrella skirt structure 17 includes vertical umbrella skirts located on both sides of the top of the insulator 1 and multiple horizontal umbrella skirts located on the side surface of the insulator 1. The recess between adjacent horizontal umbrella skirts increases in a stepwise gradient from the middle position of the insulator 1 to the upper and lower ends.
[0038] Specifically, the primary terminal 2 is located between two vertical umbrella skirts. The recess between the horizontal umbrella skirts on the outer surface of the smaller square prism is larger than the recess between the horizontal umbrella skirts on the outer surface of the larger square prism. The recess between the horizontal umbrella skirts at the middle position on the outer surface of the larger square prism is smaller, while the recess between the horizontal umbrella skirts at the upper and lower ends is larger. The above-described design of the umbrella skirt structure 17 achieves a large surface creepage distance.
[0039] See Figures 7 to 9 As shown in the embodiment of this utility model, the rear equalizing mesh 6 is arranged horizontally, and both ends are connected to the mounting insert 10 located at the bottom rear end of the insulator 1 by copper wire.
[0040] See Figure 10 and Figure 11 As shown in the embodiment of this utility model, the front equalizing mesh 8 has an L-shaped structure, and its bottom is connected to the mounting insert 10 located at the bottom front end of the insulator 1 by copper wire.
[0041] Furthermore, the four edges of the front equalizing mesh 8 are fitted with spring-shaped copper wires, ensuring smooth contact at the edges, providing good shielding, and preventing partial discharge due to sharp corner contact. The front and rear shielding equalizing meshes effectively shield the high-voltage electric field of the primary winding 4, providing effective protection for the secondary terminals and grounding side from high voltage. The insulation distance of the secondary winding 5 is adjusted inside the insulator via a bracket.
[0042] See Figure 2 As shown in the embodiment of this utility model, the two ends of the primary winding 4 are the primary winding start end and the primary winding end end 3, respectively. The primary winding start end is connected to the P1 end of the primary terminal 2 through the primary connecting plate 9, and the primary winding end 3 is directly connected to the P2 end of the primary terminal 2. Both the P1 end and the P2 end of the primary terminal 2 are flat plate structures.
[0043] Furthermore, the bottom of the insulator 1 is a contracted structure, with the secondary wiring terminal 7 located on the front side of the contracted structure. A secondary wiring cover 13 is provided on the outside of the secondary wiring terminal 7 to facilitate the exit of the secondary leads and to provide dustproof, moisture-proof, and anti-theft functions. The secondary wiring cover 13 is made of transparent material, allowing for easy and direct observation of the actual secondary wiring and providing anti-theft functionality. A semi-circular wire outlet hole is provided on the side of the secondary wiring cover 13.
[0044] Further, see Figures 3 to 6 As shown, a mounting base plate 14 is provided at the bottom of the insulator 1, and the mounting base plate 14 is provided with a grounding bolt 12 and a mounting hole 15.
[0045] In this embodiment of the invention, the insulator 1 is an integral structure cast with epoxy resin. The insulator 1 has a stepped rectangular structure, which ensures uniform insulation of the internal coils and electric field distance, making the product structure more reasonable and compact in size. The primary terminal 2 located at the top of the insulator 1 is a flat primary terminal. The shortest surface distance between the primary terminal 2 of the primary winding 4 and the secondary terminal 7 of the secondary winding 5 is the maximum surface creepage distance for high voltage and low voltage applications. The creepage distance on the outer surface of the insulator 1 can be increased to over 1150mm, meeting the requirements for use at altitudes of up to 4000 meters.
[0046] Furthermore, the primary terminal block 2 has two P1 and P2 terminals, which are arranged in parallel directions to facilitate interface connection. The P1 and P2 terminals of the primary winding 4 are exposed on the top of the insulator 1, about 3mm above the surface. The secondary terminal block 7 of the secondary winding 5 is exposed on the bottom front side of the insulator 1. The inner side of the secondary terminal block 7 is equipped with front and rear grounding grids, which effectively shield the discharge phenomenon of the high potential of the primary winding 4 to the low potential of the secondary winding 5 and ground. The insulator 1 is designed with a large creepage distance umbrella skirt structure, which will not cause surface creepage when used in high-altitude areas, thus achieving optimal partial discharge effect and long product service life.
[0047] The manufacturing process of this utility model is as follows:
[0048] The secondary winding 5 is evenly wound on the annular iron core 16. The primary winding 4 is wound using a special tool, and insulation material is wrapped around it. After the secondary winding 5 is wrapped with buffer material, a coil body is formed with primary terminals 2 marked with P1 and P2, primary winding 4, secondary winding 5, and secondary terminals 7. The secondary winding 5 is fixed to the mold by the secondary winding bracket 11. The primary winding 4 is fixed to the mold by primary terminals P1 and P2. After adjusting the distance, it is solidified by vacuum casting with epoxy resin, thus becoming an integrated structure. Finally, the secondary wiring cover 13 is sealed with sealing screws to cover the secondary terminals 7. When the user uses it, they can easily and directly observe the actual situation of the secondary wiring. It also has the functions of dustproof, moisture-proof, and anti-theft of electricity.
[0049] Specifically, the casting body encapsulating the primary winding 4 and secondary winding 5 is rectangular in shape, with a flat plate at one end, effectively meeting the requirements for fixed connection of the switchgear busbar. While ensuring uniform insulation and electric field distance of the internal coils, it makes the product structure more rational and compact in size. The surface of the casting body is designed with a large creepage distance umbrella-shaped structure, greatly increasing the surface creepage distance of the transformer and providing safety assurance for applications in high-altitude areas. The secondary terminal insert has an M6 thread.
[0050] During use, first secure the current transformer mounting insert to the mounting holes in the cabinet using connectors, then make the electrical and mechanical connections for the primary busbar and secondary cables. Finally, install the secondary wiring cover to complete the installation.
[0051] The support-type large creepage current transformer provided by this utility model is a new product designed entirely in accordance with national standards. It adopts a rolled iron core and utilizes the electromagnetic conversion principle to enable the secondary current to accurately reflect the changes in the primary current and transmit it to the secondary metering and control device. This allows the product to be directly used in 35kV switchgear in high-altitude areas for current and energy measurement and relay protection.
[0052] This utility model is made by vacuum casting of epoxy resin. It is small in size, has stable dynamic and thermal current, high metering accuracy, is moisture-proof, anti-condensation, and anti-theft. It can be widely used in the renovation and new design of switchgear in power systems at altitudes of 4000 meters.
[0053] The above description is merely an embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, extensions, etc., made within the spirit and principles of this utility model are included within the scope of protection of this utility model.
Claims
1. A supported large creepage current transformer, comprising an insulator (1) and a coil body enclosed within the insulator (1), characterized in that, The top of the insulator (1) is provided with a primary terminal (2), the bottom front side of the insulator (1) is provided with a secondary terminal (7), the outer surface of the insulator (1) is provided with an umbrella skirt structure (17) located between the primary terminal (2) and the secondary terminal (7), and the lower inner end of the insulator (1) is provided with a front equalizing mesh (8) and a rear equalizing mesh (6). The coil body includes an iron core (16), a primary winding (4), and a secondary winding (5). The iron core (16) is wrapped with a layer of cardboard corner rings, a layer of polyurethane board, a half-layer of twill tape, a half-layer of polyester film, and two half-layers of PVC tape from the inside out. The secondary winding (5) is wound on the iron core (16), and the bottom of the secondary winding (5) is supported by a secondary winding bracket (11). Both ends of the secondary winding (5) are padded with an insulating cardboard and two half-layers of polyester film. The secondary winding (5) has a half-layer of polyester film between its secondary winding layers. The outer half of the secondary winding (5) is covered with a layer of semi-conductive crepe paper, and a long strip of shielding copper foil is pressed under the semi-conductive crepe paper. The end of the shielding copper foil is welded with copper braided wire. The copper braided wire and the semi-conductive crepe paper are interlaced and overlapped. The copper braided wire is fitted with a high-voltage inner tube and led out from the non-wire side of the secondary winding (5). The copper braided wire is connected to the back equalizing mesh (6). The outermost layer of the secondary winding (5) is wrapped with two layers of semi-conductive crepe paper and a layer of yellow crepe paper for protection. The primary winding (4) passes through the middle of the secondary winding (5) and is wound independently. The outer side of the primary winding (4) is wrapped with polyester tape, polyurethane board and semi-conductive crepe paper.
2. The supported large creepage current transformer according to claim 1, characterized in that, The umbrella skirt structure (17) includes vertical umbrella skirts located on both sides of the top of the insulator (1) and multiple horizontal umbrella skirts located on the side surface of the insulator (1). The indentation between adjacent horizontal umbrella skirts increases in a stepwise gradient from the middle position of the insulator (1) to the upper and lower ends.
3. The supported large creepage current transformer according to claim 1, characterized in that, The upper and lower parts of the insulator (1) are small-sized square prisms and large-sized square prisms, respectively, with a sloping transition between the small-sized and large-sized square prisms.
4. The supported large creepage current transformer according to claim 1, characterized in that, The front equalizing mesh (8) has an L-shaped structure, and its bottom is connected to the mounting insert (10) located at the bottom front end of the insulator (1) by copper wire.
5. The supported large creepage current transformer according to claim 4, characterized in that, The four edges of the front pressure equalization mesh (8) are all fitted with spring-shaped copper wires.
6. The supported large creepage current transformer according to claim 1, characterized in that, The rear equalizing grid (6) is arranged horizontally, and its two ends are connected to the mounting insert (10) located at the bottom rear end of the insulator (1) by copper wire.
7. The supported large creepage current transformer according to claim 1, characterized in that, The two ends of the primary winding (4) are the first end of the primary winding and the last end of the primary winding (3). The first end of the primary winding is connected to the P1 end of the primary terminal (2) through the primary connecting plate (9), and the last end of the primary winding (3) is directly connected to the P2 end of the primary terminal (2). Both the P1 end and the P2 end of the primary terminal (2) are flat plate structures.
8. The supported large creepage current transformer according to claim 1, characterized in that, The bottom of the insulator (1) is a shrinkable structure, the secondary terminal (7) is disposed on the front side of the shrinkable structure, and a secondary terminal cover (13) is disposed on the outside of the secondary terminal (7).
9. The supported large creepage current transformer according to claim 1, characterized in that, The bottom of the insulator (1) is provided with a mounting base plate (14), and the mounting base plate (14) is provided with a grounding bolt (12) and a mounting hole (15).
10. The supported large creepage current transformer according to claim 1, characterized in that, The insulator (1) is made of epoxy resin as an integral structure. The shortest surface distance between the primary terminal (2) of the primary winding (4) and the secondary terminal (7) of the secondary winding (5) is the surface creepage distance for high voltage and low voltage.