A natural ester insulating oil current transformer and a design and manufacturing method thereof

Abstract

The application belongs to the field of current transformers, and particularly relates to a natural ester insulating oil current transformer and a design and manufacturing method thereof, which comprises an expander, an oil storage tank, a primary winding, main insulation, insulating oil, a sealing gasket, a secondary winding, an oil tank and a porcelain sleeve. The bottom end of the expander is provided with the oil storage tank, the bottom end of the oil storage tank is provided with the porcelain sleeve, the inside of the porcelain sleeve is provided with the primary winding, the outside of the primary winding is provided with the main insulation, the insulating oil is filled in the inside of the current transformer, the oil tank is arranged at the bottom end of the porcelain sleeve, the sealing gasket is arranged between the sealing surfaces of the oil tank and the porcelain sleeve, and the secondary winding is arranged in the inside of the oil tank. The insulating oil filled with the natural ester insulating oil material can improve the ignition point, has excellent fireproof characteristics, is environmentally friendly, can be recycled, can prolong the insulation life of the current transformer, has high heat resistance, can reduce the weight and volume of the current transformer, and has better high-temperature resistance and overload capacity.

Description

Technical Field

[0001] This invention relates to the field of current transformers, specifically a natural ester insulating oil current transformer and its design and manufacturing method. Background Technology

[0002] A current transformer is an instrument made based on the principle of electromagnetic induction. It is used in the processes of power generation, transformation, transmission, distribution and consumption to transform current and provide electrical isolation.

[0003] With the development of science and technology and the progress of the times, existing current transformers have been improved over a long period of time and can now accurately transform current. The accuracy and speed have been greatly improved compared with previous current transformers.

[0004] Current high-voltage oil-immersed current transformers use transformer oil as insulating oil, which is a mineral oil. This oil has drawbacks such as low flash point, low insulation and heat resistance, flammability and explosiveness, poor fire safety, non-renewability, difficulty in biodegradation, and environmental pollution from leakage. Therefore, this paper proposes a natural ester insulating oil current transformer and its design and manufacturing method to address these issues. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the insulating oil used in current high-voltage oil-immersed current transformers is transformer oil, which is a mineral oil. This oil has problems such as low flash point, low insulation heat resistance, flammability and explosiveness, poor fire safety, non-renewability, difficulty in biodegradation, and environmental pollution from leakage. This invention proposes a natural ester insulating oil current transformer and its design and manufacturing method.

[0006] The technical solution adopted by this invention to solve its technical problem is as follows: A natural ester insulating oil current transformer and its design and manufacturing method, comprising an expander, an oil conservator, a primary winding, main insulation, insulating oil, a sealing gasket, a secondary winding, an oil tank, and a porcelain bushing; the expander has an oil conservator at its bottom end, the oil conservator has a porcelain bushing at its bottom end, the porcelain bushing has a primary winding inside, the primary winding has main insulation outside, the insulating oil fills the interior of the current transformer, the oil tank is located at the bottom end of the porcelain bushing, the sealing gasket is located between the oil tank and the porcelain bushing, and the secondary winding is located inside the oil tank. The insulating oil is a natural ester insulating oil, the main insulation uses heat-modified cable paper or heat-modified crepe paper, and the sealing gasket uses fluororubber. Using natural ester insulating oil increases the ignition point and provides excellent fire resistance; it is environmentally friendly and recyclable; it extends the insulation life of the current transformer; it has a high heat resistance rating, reducing the weight and volume of the current transformer; and it has better high-temperature resistance and overload capacity. Using natural ester insulating oil further improves the overall high-temperature resistance and overload capacity of the current transformer.

[0007] Preferably, a connecting mechanism is provided between the expander and the oil tank. The connecting mechanism includes a connecting column, a limiting plate, a limiting component, a sliding component, a positioning block, a positioning spring, a moving block, a moving groove, a positioning groove, and a locking block. The connecting column is located at the bottom end of the expander, and the connecting column passes through the expander and extends to the outside of the expander. The limiting plate is fixedly connected to one side of the connecting column. The limiting component is located at the top of the limiting plate. The sliding component is located at the top of the connecting column near the center position. The positioning block is sleeved on the side of the connecting column away from the limiting plate. The positioning spring is located inside the positioning block. The moving block is fixedly connected inside the positioning block near the positioning block and is slidably connected inside the moving groove. The moving groove is opened at both ends of the connecting column near the positioning block. The positioning groove is opened on both sides of the top of the oil tank. The locking block is fixedly connected to the top of the positioning groove and engages with the positioning block. The connecting mechanism facilitates the connection between the components of the current transformer, improving the efficiency of assembling the current transformer.

[0008] Preferably, the side of the positioning spring closest to the connecting post is fixedly connected to the connecting post, and the side of the positioning spring furthest from the connecting post is fixedly connected to the positioning block. The restoring force of the positioning spring enables the positioning block to automatically reset and engage with the locking block.

[0009] Preferably, the limiting component includes a limiting block, a connecting shaft, a torsion spring, and a fixing block. The limiting block engages with the limiting plate. The connecting shaft is fixedly connected to one side of the top of the limiting block. The torsion spring is wound around the outside of the connecting shaft. The side of the fixing block near the connecting shaft is movably connected to the connecting shaft via a bearing, and the side of the fixing block away from the connecting shaft is fixedly connected to the outside of the expander. The limiting component facilitates the limiting of the connecting column and the limiting plate and facilitates the release of the limiting of the connecting column and the limiting plate.

[0010] Preferably, a protective pad is glued to the side of the limiting block near the limiting plate, and the protective pad is made of rubber. A knob is fixedly connected to the top of the limiting block away from the connecting shaft, and the outer side of the knob is provided with anti-slip texture. The rubber protective pad protects the limiting plate and prevents the limiting block and the limiting plate from being worn due to friction.

[0011] Preferably, the sliding assembly includes a slider and a groove. The slider is fixedly connected to the top of the connecting column near the center position, and the slider is slidably connected inside the groove. The groove is formed on the expander. When the connecting column moves, the slider, which is fixedly connected to the connecting column, also slides synchronously inside the groove. The combined action of the slider and the groove reduces the friction of the connecting column when it moves, preventing the connecting column from getting stuck due to excessive friction, making the connecting column move more smoothly. At the same time, the combined action of the slider and the groove limits the movement distance of the connecting column, preventing the connecting column from moving excessively and detaching from the expander.

[0012] A method for designing and manufacturing a current transformer using natural ester insulating oil, the method comprising the following steps:

[0013] S1: Wrap the main insulation around the outside of the primary winding, insert the secondary winding into the main insulation and fix it, assemble it into the transformer body, and perform heating and vacuum drying treatment to remove moisture from the transformer body; S: After the transformer body is dried, it is assembled with the expander, oil conservator, sealing gasket, oil tank, porcelain bushing, etc.

[0014] S3: The raw materials of insulating oil are alkali-refined, adsorbed, decolorized, and deodorized, and then additives such as antioxidants, metal passivators, pour point depressants, and microbial inhibitors are added. Finally, high-vacuum dehydration and degassing treatment is carried out.

[0015] S4: Vacuum the inside of the current transformer and inject the treated insulating oil into the inside of the current transformer. After static placement, pressure test for leaks, installation of the expansion tank cover, and final product test, it can be used only after passing the test.

[0016] The advantages of this invention are:

[0017] 1. This invention, through a structural design combining main insulation, insulating oil, and sealing gaskets, achieves improved ignition point and environmental friendliness of the insulating oil. It addresses the shortcomings of current high-voltage oil-immersed current transformers, which use transformer oil (a mineral oil) which suffers from low ignition point, low insulation heat resistance, flammability and explosiveness, poor fire safety, non-renewability, difficulty in biodegradation, and environmental pollution from leaks. The insulating oil used is a natural ester insulating oil with a high ignition point and excellent fire-retardant properties; it is environmentally friendly and recyclable; it extends the insulation life of the current transformer; and its high heat resistance reduces the weight and volume of the current transformer, providing better high-temperature resistance and overload capacity.

[0018] 2. Through the structural design of the connecting mechanism, this invention enables convenient connection between the expander and the oil tank, solving the problem of inconvenient connection between the current transformer expander and the oil tank in existing current transformers. This facilitates the connection between the components of the current transformer and improves the efficiency of assembling the current transformer. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a front view structural diagram of Embodiment 1;

[0021] Figure 2 This is a frontal cross-sectional view of Embodiment 1.

[0022] Figure 3 This is a partial frontal cross-sectional structural diagram of Embodiment 1;

[0023] Figure 4 Example 1 Figure 3 Enlarged structural diagram at point A in the middle;

[0024] Figure 5 Example 1 Figure 4 Enlarged structural diagram at point B;

[0025] Figure 6 This is a partial three-dimensional structural diagram of the connection mechanism in Embodiment 1.

[0026] In the diagram: 1. Expander; 2. Oil conservator; 3. Primary winding; 4. Main insulation; 5. Insulating oil; 6. Sealing gasket; 7. Secondary winding; 8. Oil tank; 9. Porcelain bushing; 1201. Connecting post; 1202. Limiting plate; 1203. Limiting block; 1204. Protective pad; 1205. Knob; 1206. Connecting shaft; 1207. Torsion spring; 1208. Fixing block; 1209. Sliding block; 1210. Slide groove; 1211. Positioning block; 1212. Positioning spring; 1213. Moving block; 1214. Moving groove; 1215. Positioning groove; 1216. Locking block. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] Please see Figure 1-6 As shown, a natural ester insulating oil current transformer and its design and manufacturing method are disclosed, comprising an expander 1, an oil conservator 2, a primary winding 3, a main insulation 4, insulating oil 5, a sealing gasket 6, a secondary winding 7, an oil tank 8, and a porcelain bushing 9. The oil conservator 2 is located at the bottom of the expander 1, and the porcelain bushing 9 is located at the bottom of the oil conservator 2. The primary winding 3 is located inside the porcelain bushing 9, and the main insulation 4 is located outside the primary winding 3. The insulating oil 5 fills the interior of the current transformer. The oil tank 8 is located at the bottom of the porcelain bushing 9. The sealing gasket 6 is located between the sealing surfaces of the oil tank 8 and the porcelain bushing 9. The secondary winding 7 is located inside the oil tank 8. The insulating oil 5 is natural ester insulating oil, the main insulation 4 is made of heat-modified cable paper or heat-modified crepe paper, and the sealing gasket 6 is made of fluororubber.

[0030] During operation, the insulating oil 5, made from natural ester insulating oil, has an increased ignition point and excellent fire-retardant properties; it is environmentally friendly and recyclable; it can extend the insulation life of the current transformer; it has a high heat resistance rating, which can reduce the weight and volume of the current transformer; and it has better high-temperature resistance and overload capacity. By using fluororubber as the material for the sealing gasket 6, the compatibility between the sealing gasket 6 and the insulating oil 5 is improved. By using heat-modified cable paper and heat-modified crepe paper as the main insulation, and using natural ester insulating oil in the insulating oil 5, the overall high-temperature resistance and overload capacity of the current transformer are further improved.

[0031] A connecting mechanism is provided between the expander 1 and the oil tank 2. The connecting mechanism includes a connecting post 1201, a limiting plate 1202, a limiting component, a sliding component, a positioning block 1211, a positioning spring 1212, a moving block 1213, a moving groove 1214, a positioning groove 1215, and a locking block 1216. The connecting post 1201 is located at the bottom end of the expander 1, and the connecting post 1201 passes through the expander 1 and extends to the outside of the expander 1. The limiting plate 1202 is fixedly connected to one side of the connecting post 1201. The limiting component is located at the top end of the limiting plate 1202. The sliding component is located near the center of the connecting post 1201. At the top, the positioning block 1211 is sleeved on the side of the connecting column 1201 away from the limiting plate 1202. The positioning spring 1212 is disposed inside the positioning block 1211. The moving block 1213 is fixedly connected to the side of the positioning block 1211 near the positioning block 1211 inside the positioning block 1211, and the moving block 1213 is slidably connected to the inside of the moving groove 1214. The moving groove 1214 is opened at both ends of the connecting column 1201 near the positioning block 1211. The positioning groove 1215 is opened on both sides of the top of the oil tank 2. The locking block 1216 is fixedly connected to the top of the positioning groove 1215 inside the positioning groove 1215, and the locking block 1216 is engaged with the positioning block 1211.

[0032] During operation, when connecting the expander 1 and the oil tank 2, first align the positioning block 1211 with the positioning groove 1215, then press the expander 1 downwards. Under the downward pressure, the expander 1 moves the positioning block 1211 downwards, causing the positioning block 1211 to abut against the locking block 1216. The expansion block 1211 moves towards the connecting column 1201, compressing the positioning spring 1212 and causing it to elastically deform. When block 1211 moves, it is fixedly connected to positioning block 1211 and slides synchronously inside moving block 1214. The combined action of moving block 1213 and moving block 1214 limits the movement distance of positioning block 1211. When the expander 1 is pressed down to the limit, the squeezing of positioning block 1211 by locking block 1216 disappears. At this time, positioning block 1211 returns to its original position under the restoring force of positioning spring 1212 and engages with locking block 1216, thus connecting expander 1 and oil tank 2.

[0033] The positioning spring 1212 is fixedly connected to the connecting post 1201 on the side closer to the connecting post 1201, and the positioning spring 1212 is fixedly connected to the positioning block 1211 on the side away from the connecting post 1201.

[0034] During operation, the restoring force of the positioning spring 1212 causes the positioning block 1211 to automatically reset and engage with the locking block 1216.

[0035] The limiting assembly includes a limiting block 1203, a connecting shaft 1206, a torsion spring 1207, and a fixing block 1208. The limiting block 1203 engages with the limiting plate 1202. The connecting shaft 1206 is fixedly connected to one side of the top of the limiting block 1203. The torsion spring 1207 is wound around the outside of the connecting shaft 1206. The side of the fixing block 1208 closest to the connecting shaft 1206 is movably connected to the connecting shaft 1206 via a bearing, and the side of the fixing block 1208 furthest from the connecting shaft 1206 is fixedly connected to the outside of the expander 1.

[0036] During operation, when disconnecting the expander 1 from the oil tank 2, first turn the knob 1205 to rotate the limiting block 1203 and the protective pad 1204, causing the limiting block 1203 and the protective pad 1204 to release their restriction on the limiting plate 1202. When the limiting block 1203 rotates, the connecting shaft 1206 also rotates synchronously, causing the torsion spring 1207 to twist and produce elastic deformation. When the knob 1205 is stopped, the limiting block 1203 can return to its original position under the restoring force of the torsion spring 1207 to limit the limiting plate 1202. Then, the limiting plate 1202 is pulled away from the expander 1. Under the action of the pulling force, the limiting plate 1202 moves and pulls the positioning block 1211 to move synchronously. At this time, the positioning block 1211 releases its engagement with the locking block 1216, and the connection between the expander 1 and the oil tank 2 is disconnected.

[0037] The limiting block 1203 has a protective pad 1204 glued to the side near the limiting plate 1202, and the protective pad 1204 is made of rubber. The top of the limiting block 1203 is fixedly connected to a knob 1205 on the side away from the connecting shaft 1206, and the outer side of the knob 1205 is provided with anti-slip texture.

[0038] During operation, the rubber protective pad 1204 protects the limiting plate 1202 and prevents the limiting block 1203 from wearing out due to friction with the limiting plate 1202. The anti-slip texture on the outside of the knob 1205 increases the friction and prevents it from slipping when the knob 1205 is turned due to insufficient friction.

[0039] The sliding assembly includes a slider 1209 and a groove 1210. The slider 1209 is fixedly connected to the top of the connecting post 1201 near the center position, and the slider 1209 is slidably connected inside the groove 1210. The groove 1210 is formed on the expander 1.

[0040] During operation, as the connecting column 1201 moves, the slider 1209, which is fixedly connected to the connecting column 1201, also slides synchronously inside the slide groove 1210. The combined action of the slider 1209 and the slide groove 1210 reduces the friction of the connecting column 1201 during movement, preventing the connecting column 1201 from jamming due to excessive friction, thus making the movement of the connecting column 1201 smoother. At the same time, the combined action of the slider 1209 and the slide groove 1210 limits the movement distance of the connecting column 1201, preventing the connecting column 1201 from moving excessively and detaching from the expander 1.

[0041] A method for designing and manufacturing a current transformer using natural ester insulating oil, the method comprising the following steps:

[0042] S1: Wrap the main insulation 4 around the outside of the primary winding 3, put the secondary winding 7 into the main insulation 4 and fix it, assemble it into the transformer body, and perform heating and vacuum drying treatment on the transformer body to remove the moisture in the transformer body.

[0043] S2: After the body is dried, it is assembled with the expander 1, oil tank 2, sealing gasket 6, oil tank 8, porcelain sleeve 9, etc.

[0044] S3: The raw materials of insulating oil 5 are subjected to alkali refining, adsorption decolorization and deodorization, and then additives such as antioxidants, metal passivators, pour point depressants and microbial inhibitors are added. Finally, high vacuum dehydration and degassing treatment is carried out.

[0045] S4: Vacuum the inside of the current transformer and inject the treated insulating oil 5 into the inside of the current transformer. After static placement, pressure test for leaks, installation of the expansion tank cover, and final product test, it can be used only after passing the test.

[0046] Working Principle: The insulating oil 5, made of natural ester insulating oil, has an increased ignition point and excellent fire-retardant properties; it is environmentally friendly and recyclable; it can extend the insulation life of the current transformer; it has a high heat resistance rating, which can reduce the weight and volume of the current transformer, and has better high temperature resistance and overload capacity. The natural ester insulating oil current transformer can be designed as upright or inverted. In the design, the insulation heat resistance rating is designed as 140, the average temperature rise of the winding is designed as 95K, and the hot spot temperature rise is designed as 110K. By using fluororubber as the material of the sealing gasket 6, the compatibility between the sealing gasket 6 and the insulating oil 5 is improved. By using heat-modified cable paper and heat-modified crepe paper as the main insulation, and using natural ester insulating oil 5, the overall high temperature resistance and overload capacity of the current transformer are further improved.

[0047] When connecting the expander 1 and the oil tank 2, first align the positioning block 1211 with the positioning groove 1215, then press the expander 1 downwards. Under the downward pressure, the expander 1 moves the positioning block 1211 downwards, causing the positioning block 1211 to abut against the locking block 1216. The expansioner 1211 moves towards the connecting post 1201 and compresses the positioning spring 1212, causing the positioning spring 1212 to undergo elastic deformation. When the positioning block 1211... When 211 moves, it is fixedly connected to the positioning block 1211 and slides synchronously inside the moving block 1213. The moving block 1213 and the moving block 1214 limit the moving distance of the positioning block 1211 through the combined action of the moving block 1213 and the moving block 1214. When the expander 1 is pressed down to the limit, the squeezing of the positioning block 1211 by the locking block 1216 disappears. At this time, the positioning block 1211 returns to its original position under the action of the restoring force of the positioning spring 1212 and engages with the locking block 1216, so as to connect the expander 1 and the oil tank 2.

[0048] When disconnecting the expander 1 from the oil tank 2, first turn the knob 1205 to rotate the limiting block 1203 and the protective pad 1204 so that the limiting block 1203 and the protective pad 1204 release the limiting plate 1202. When the limiting block 1203 rotates, the connecting shaft 1206 also rotates synchronously, causing the torsion spring 1207 to twist and produce elastic deformation. When the knob 1205 is stopped, the limiting block 1203 can return to its original position under the restoring force of the torsion spring 1207 to limit the limiting plate 1202. Then, the limiting plate 1202 is pulled away from the expander 1. Under the action of the pulling force, the limiting plate 1202 moves and pulls the positioning block 1211 to move synchronously. At this time, the positioning block 1211 is released from the engagement with the locking block 1216, and the connection between the expander 1 and the oil tank 2 is disconnected.

[0049] When the connecting column 1201 moves, the slider 1209, which is fixedly connected to the connecting column 1201, also slides synchronously inside the slide groove 1210. The combined action of the slider 1209 and the slide groove 1210 reduces the friction of the connecting column 1201 when it moves, preventing the connecting column 1201 from getting stuck due to excessive friction, making the connecting column 1201 move more smoothly. At the same time, the combined action of the slider 1209 and the slide groove 1210 limits the moving distance of the connecting column 1201, preventing the connecting column 1201 from moving excessively and coming off the expander 1.

[0050] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A current transformer made of natural ester insulating oil, characterized in that: The current transformer includes an expander (1), an oil conservator (2), a primary winding (3), main insulation (4), insulating oil (5), a sealing gasket (6), a secondary winding (7), an oil tank (8), and a porcelain bushing (9). The expander (1) has an oil conservator (2) at its bottom end, and the oil conservator (2) has a porcelain bushing (9) at its bottom end. The porcelain bushing (9) contains the primary winding (3), and the primary winding (3) has main insulation (4) on its outside. The insulating oil (5) fills the interior of the current transformer. The oil tank (8) is located at the bottom end of the porcelain bushing (9), and the sealing gasket (6) is located at the bottom end of the porcelain bushing (9). Between the sealing surfaces of the oil tank (8) and the porcelain sleeve (9), the secondary winding (7) is located inside the oil tank (8); the insulating oil (5) is natural ester insulating oil, the main insulation (4) is made of heat-modified cable paper or heat-modified crepe paper, and the sealing gasket (6) is made of fluororubber material; a connecting mechanism is provided between the expander (1) and the oil tank (2), the connecting mechanism including a connecting column (1201), a limiting plate (1202), a limiting component, a sliding component, a positioning block (1211), a positioning spring (1212), a moving block (1213), a moving groove (1214), and a positioning groove. (1215) and the locking block (1216), the connecting post (1201) is located at the bottom end of the expander (1), and the connecting post (1201) penetrates the expander (1) and extends to the outside of the expander (1), the limiting plate (1202) is fixedly connected to one side of the connecting post (1201), the limiting component is located at the top of the limiting plate (1202), the sliding component is located at the top of the connecting post (1201) near the center position, the positioning block (1211) is sleeved on the side of the connecting post (1201) away from the limiting plate (1202), and the positioning spring (1212) is located at the bottom end of the expander (1), and the connecting post (1201) is located at the bottom end of the expander (1), and the connecting post (1201) is located at the bottom end of the expander (1), and the connecting post (1201) extends to the outside of the expander (1), the limiting component (1201) extends to the bottom end of the expander (1), the connecting post (1201) extends to the bottom end of the expander (1), and the connecting post (1201) extends to the bottom end of the expander (1), ... The movable block (1213) is fixedly connected to the inside of the positioning block (1211) on the side close to the positioning block (1211), and the movable block (1213) is slidably connected to the inside of the movable groove (1214). The movable groove (1214) is opened at both ends of the connecting column (1201) on the side close to the positioning block (1211). The positioning groove (1215) is opened on both sides of the top of the oil tank (2). The locking block (1216) is fixedly connected to the top of the positioning groove (1215), and the locking block (1216) engages with the positioning block (1211).

2. The natural ester insulating oil current transformer according to claim 1, characterized in that: The positioning spring (1212) is fixedly connected to the connecting post (1201) on the side closer to the connecting post (1201), and the positioning spring (1212) is fixedly connected to the positioning block (1211) on the side away from the connecting post (1201).

3. A natural ester insulating oil current transformer according to claim 2, characterized in that: The limiting assembly includes a limiting block (1203), a connecting shaft (1206), a torsion spring (1207), and a fixing block (1208). The limiting block (1203) engages with the limiting plate (1202). The connecting shaft (1206) is fixedly connected to one side of the top of the limiting block (1203). The torsion spring (1207) is wrapped around the outside of the connecting shaft (1206). The side of the fixing block (1208) close to the connecting shaft (1206) is movably connected to the connecting shaft (1206) through a bearing, and the side of the fixing block (1208) away from the connecting shaft (1206) is fixedly connected to the outside of the expander (1).

4. A natural ester insulating oil current transformer according to claim 3, characterized in that: The limiting block (1203) has a protective pad (1204) glued to the side near the limiting plate (1202), and the protective pad (1204) is made of rubber. A knob (1205) is fixedly connected to the top of the limiting block (1203) away from the connecting shaft (1206), and the outer side of the knob (1205) is provided with anti-slip texture.

5. A natural ester insulating oil current transformer according to claim 4, characterized in that: The sliding assembly includes a slider (1209) and a groove (1210). The slider (1209) is fixedly connected to the top of the connecting column (1201) near the center position, and the slider (1209) is slidably connected inside the groove (1210), which is opened on the expander (1).

6. A method for designing and manufacturing a natural ester insulating oil current transformer, comprising the natural ester insulating oil current transformer as described in any one of claims 1-5, characterized in that: The manufacturing method includes the following steps: S1: Wrap the main insulation (4) around the outside of the primary winding (3), put the secondary winding (7) into the main insulation (4) and fix it, assemble it into the transformer body, and heat and vacuum dry the transformer body to remove the moisture in the transformer body; S2: After the transformer body is dried, assemble it with the expander (1), oil tank (2), sealing gasket (6), oil tank (8) and porcelain sleeve (9); S3: The raw materials of insulating oil (5) are subjected to alkali refining, adsorption decolorization and deodorization, and then antioxidants, metal passivators, pour point depressants and microbial inhibitors are added, and finally high vacuum dehydration and degassing treatment is carried out. S4: Vacuum the inside of the current transformer and inject the treated insulating oil (5) into the inside of the current transformer. Then, after static placement, pressure test, installation of expansion tank cover, and finished product test, it can be used only after passing the test.

Images