A three-phase five-column voltage transformer

Abstract

The utility model discloses a three -phase five -column voltage transformer relates to electric power measuring equipment technical field, including main insulator adopts epoxy resin vacuum casting forming, and its inside is formed with resin -coil integrated structure, five -column structure sets up in the inside of main insulator, including A, B, C three -phase body and zero sequence body, wherein A, B, C three -phase body is arranged in the front of five -column structure, and zero sequence body is arranged in the rear of five -column structure, A, B, C three -phase iron core is correspondingly embedded in A, B, C three -phase body inside respectively, and every phase iron core is connected with corresponding phase resin -coil integrated structure, and the european C -shaped joint is along the lateral parallel distribution in the top of A, B, C three -phase iron core, is integrated in the top of main insulator. The application introduces five -column type iron core structure, provides low magnetic resistance loop for zero sequence magnetic flux. Possesses the comprehensive advantage such as high measurement accuracy, good functional integration, stable and reliable operation, compact structure and good economy.

Description

Technical Field

[0001] The present utility model relates to the technical field of electric power measuring equipment, in particular to a three-phase five-limb voltage transformer. Background Art

[0002] At present, in power systems, three-phase five-limb voltage transformers are key equipment for realizing voltage measurement, electric energy metering and relay protection functions. Under high-current working conditions or three-phase unbalanced working conditions, traditional three-phase three-limb voltage transformers are prone to magnetic circuit saturation, which leads to a significant drop in measurement accuracy, and even affects the safe operation of the entire power system in severe cases.

[0003] With the rapid development of new energy power generation grid-connection technology and the extensive construction of smart grids, the amplitude of voltage fluctuations during power grid operation increases, and the harmonic content also rises significantly, which puts forward more stringent requirements on the linearity, anti-saturation capability and frequency response characteristics of voltage transformers.

[0004] The five-limb voltage transformer in the prior art provides a path for zero-sequence magnetic flux by adding two auxiliary side limbs, which improves the magnetic circuit distribution under three-phase unbalance to a certain extent and reduces the risk of core saturation. However, this type of product still has obvious defects: first, the equipment is large in size, takes up much installation space, and does not conform to the development trend of miniaturization of power equipment; second, the manufacturing cost is relatively high, which is not conducive to large-scale promotion and application; third, the measurement error increases significantly under harmonic conditions, and it is difficult to meet high-precision measurement requirements. In addition, some five-limb voltage transformers have deficiencies in core material selection, winding layout design or insulation structure optimization, and are prone to excessive temperature rise or partial discharge problems during operation, which seriously affects the long-term reliability of the equipment. Contents of the Utility Model

[0005] The purpose of the present utility model is to provide a three-phase five-limb voltage transformer to solve the problems of large size, high manufacturing cost and increased error under harmonic conditions of voltage transformers in the prior art.

[0006] To achieve the above purpose, the present application proposes a three-phase five-limb voltage transformer, comprising: a main insulator, which is formed by vacuum casting of epoxy resin, a resin-coil integrated structure is formed inside the main insulator, and the overall shape is convex; a five-limb structure, which is arranged inside the main insulator, comprises A-phase, B-phase, C-phase bodies and a zero-sequence body, and adopts a Y-Y wiring mode; wherein the A-phase, B-phase and C-phase bodies are arranged in front of the five-limb structure, and the zero-sequence body is arranged behind the five-limb structure, forming a symmetric magnetic circuit layout; A-phase, B-phase and C-phase iron cores, which are respectively embedded inside the A-phase, B-phase and C-phase bodies correspondingly, and each phase of iron core is connected with the resin-coil integrated structure of the corresponding phase; European-style C-shaped connectors are arranged horizontally in parallel above the A, B, and C phase iron cores, integrated on the top of the main insulator, and used for wiring connections to the high-voltage side of the power grid.

[0007] In one embodiment, a rectangular resin box encapsulating the A, B, and C phase iron cores is provided in front of the main insulator. The top of the rectangular resin box has an inclined surface, and the bottom is flush with the main insulator. Both sides of the top of the main insulator are C-shaped, and the bottom is concave near the bottom surface. A secondary wiring groove is provided between the A and B phases in front of the main insulator.

[0008] In one embodiment, the European-style C-shaped connector has a fuse cavity in the horizontal direction, and a spring, a high-voltage fuse, and a bolt sleeve are sequentially assembled in the fuse cavity.

[0009] In one embodiment, the inner wall of the fuse cavity is provided with a high-voltage shielding mesh, a fuse shielding mesh and a ground shielding mesh in sequence from the inside to the outside; the high-voltage shielding mesh and the fuse shielding mesh are horizontally fitted inside and outside the fuse cavity, with gaps between them.

[0010] In one embodiment, the three-phase iron cores A, B, and C are all arranged longitudinally, and the zero-sequence coil corresponding to the zero-sequence coil is arranged laterally behind the B-phase iron core; two vertical cylinders are provided above the zero-sequence coil, and the arc surface of the cylinders is provided with umbrella skirts. The O and N terminals are located at the top of the cylinders, and the cylinders are provided with bolt inserts, conductive rods, and shielding rings from top to bottom.

[0011] In one embodiment, the resin-coil integrated structure includes: The iron core clamp is wrapped around the outside of the iron core, and its edge is integrally formed with a support base with a support frame; The primary conductive sheet is fixed to the bottom outer side of the primary coil, serving the dual functions of conductive connection and structural support. The resin bracket is connected to the support frame of the primary conductive sheet and the iron core clamp respectively through connectors, thereby achieving precise positioning of the primary coil and the iron core.

[0012] In one embodiment, the iron core clamp is provided with symmetrically distributed support seats, wherein a pair of diagonally opposite support seats are respectively provided with support frames, and countersunk holes are provided on the support frames.

[0013] In one embodiment, the countersunk hole is an elliptical countersunk hole, with an adjustment margin reserved along the major axis of the elliptical countersunk hole for adjusting the insulation distance between the primary coil and the iron core and the secondary coil.

[0014] In one embodiment, the resin support is a cylindrical structure, and metal inserts are pre-embedded in the end face of the resin support. The metal inserts have threaded holes that are adapted to the connector.

[0015] In one embodiment, the connector is a cross-slot countersunk bolt, a fixing seat is provided on the primary conductive sheet, the cross-slot countersunk bolt is welded on the fixing seat, and the top of the cross-slot countersunk bolt does not exceed the plane of the fixing seat.

[0016] The advantages of the above technical solution adopted in this utility model compared with the prior art are: 1. Excellent insulation performance, improving equipment reliability: This utility model adopts an epoxy resin vacuum casting process to form an integrated structure of resin and coil, which greatly improves the insulation performance. The resin bracket has high mechanical strength and can stably fix the primary coil, eliminating the need for traditional binding or gluing methods. It can effectively avoid the risk of coil loosening under temperature changes or vibration, ensuring the overall structure is stable and reliable. 2. Easy adjustment and efficient installation: This utility model innovatively adopts an elliptical countersunk hole design on the support frame of the diagonal fixing seat of the iron core clamp, with sufficient adjustment margin reserved in the long axis direction. During the assembly of the device body, the insulation distance between the primary coil and the iron core and the secondary winding can be precisely adjusted through this design; during the installation process, the bolts can be pre-tightened, and then fully tightened after the primary coil position is adjusted into place, which significantly shortens the assembly time and improves the installation efficiency. 3. Compact structure, suitable for miniaturization requirements: Compared with the traditional metal suspension fixing method, the resin bracket of this utility model is directly fixed to the bottom of the coil, which can save the space occupied by the metal frame on the upper part and side wall of the coil, effectively reduce the volume of the casting body, and fully meet the technical requirements of the State Grid for the miniaturization and intensification of power equipment. 4. Reduce casting defects and achieve dual cost reduction: Traditional metal suspension fixing methods are prone to air gaps or stress concentrations during casting, leading to increased partial discharge and decreased yield. In this invention, the resin support and epoxy casting material have similar coefficients of thermal expansion, resulting in a tighter bond and no interface cracking after curing, thus reducing casting defects at the source. Simultaneously, the resin support is directly fixed to the bottom of the coil, eliminating the need for upper or sidewall metal supports. The casting body can closely adhere to the outer contour of the coil, reducing unnecessary resin filling and significantly lowering epoxy resin usage, saving material costs. Furthermore, the resin support can be produced in multiple parts at once using a compression molding process, resulting in high production efficiency. Since epoxy resin is cheaper than metal materials and requires no additional rust prevention treatment or machining, manufacturing costs are further reduced. 5. Fuse protection enhances system safety: A high-voltage current-limiting fuse is connected in series at the high-voltage end of the instrument transformer. When an internal short circuit, overload, or power grid fault occurs in the instrument transformer, the fuse can quickly melt and cut off the fault current, preventing the accident from escalating. This design effectively isolates faulty equipment, prevents high voltage from entering the secondary circuit, thereby protecting the safety of operators and the integrity of measurement and protection devices, significantly improving the reliability of system operation. 6. High measurement accuracy, also functions as a zero-sequence voltage transformer: Under normal operating conditions or in the event of a single-phase ground fault, the zero-sequence magnetic flux can smoothly pass through the two end posts to form a loop, without being forced to close through a high magnetic reluctance path such as air. This stable magnetic flux path significantly reduces the additional errors caused by the zero-sequence magnetic flux, providing a low magnetic reluctance loop for the zero-sequence magnetic flux generated during three-phase imbalance or ground faults, ensuring the accuracy of phase and line voltage measurements. This device can measure line and phase voltages like a regular PT (voltage transformer), and its auxiliary secondary winding (open delta winding) can accurately reflect the system's zero-sequence voltage for monitoring system insulation conditions and single-phase ground faults, achieving "multi-purpose functionality" and high integration. Attached Figure Description

[0017] Figure 1 Three-view diagram of a three-phase five-limb voltage transformer; Figure 2 for Figure 1 AA section view in the middle; Figure 3 for Figure 1 BB section view in the middle; Figure 4 Here are the three views of the iron core clamp; Figure 5 This is a schematic diagram of a resin support. Figure 6 Three-view diagram of a primary conductive sheet; Figure 7 This is a schematic diagram showing the placement of the coils; In the diagram: 1 is the iron core; 2 is the iron core clamp; 3 is the cross-slot countersunk bolt; 4 is the metal insert; 5 is the resin bracket; 6 is the primary conductive sheet; 7 is the primary coil; 8 is the secondary coil; 9 is the main insulator; 10 is the shielding ring; 11 is the conductive rod; 12 is the metal insert; 13 is the spring; 14 is the fuse shielding mesh; 15 is the high-voltage fuse; 16 is the high-voltage shielding mesh; 17 is the ground shielding mesh; 18 is the European C-shaped connector; 19 is the bolt sleeve; 20 is the inclined surface; 21 is the base plate; 22 is the support base; 23 is the support frame. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0019] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise expressly specified. "Several" means one or more, unless otherwise expressly specified.

[0021] In the description of this application, it should be understood that the terms "center", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0022] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0023] This embodiment provides a three-phase five-limb voltage transformer, aiming to solve the problems of asymmetrical magnetic circuits, limited functionality, poor insulation performance, and inconvenient installation and maintenance of traditional voltage transformers. Figure 1-3As shown, it includes a mounting base plate 21 and a main insulator 9 disposed on the mounting base plate 21. The main insulator 9 forms an integrated resin-coil structure and integrates core components such as a five-column structure, a European C-shaped connector 18, and a zero-sequence coil. It has the advantages of high measurement accuracy, stable operation, and compact structure, and is suitable for power distribution systems with ungrounded neutral points or grounded through arc suppression coils. The main insulator 9 is an epoxy resin vacuum casting molded part, which is the core of insulation and structural support of the instrument transformer. Its specific structure is as follows: Shape optimization: The main insulator 9 is convex, with both the upper left and upper right corners set as C-angles (rounded transition angles), and the two sides near the bottom are concave. Simultaneously, a rectangular resin-coated structure encapsulating the A, B, and C phase iron cores 1 is added to the front of the main insulator 9. The top of this rectangular resin structure is a circular tangent surface, the two sides are designed as inclined surfaces 20, and the bottom surface is flush with the main insulator 9. This design effectively reduces the volume of the main insulation, reduces the amount of epoxy resin used, and lowers production costs.

[0024] Wiring slot setting: A secondary wiring slot is provided between phases A and B (lower middle position) in front of the main insulator 9 to facilitate the connection of the secondary cables on the low voltage side, avoid the mess of secondary lines, and improve assembly efficiency. Installation and fixing: An installation insert is pre-embedded below the main insulator 9 and fixedly connected to the mounting base plate 21 by bolts, which optimizes the stability of the overall structure and facilitates the installation and removal of the current transformer on the switch cabinet. The five-column structure, located inside the main insulator 9, is the core for realizing voltage measurement and zero-sequence insulation monitoring functions, and specifically includes: Composition and Layout: The five-column structure includes three-phase A, B, and C cores and a zero-sequence core, using a YY connection. The three-phase A, B, and C cores are arranged horizontally side-by-side at the front of the five-column structure, with the corresponding A, B, and C cores 1 placed vertically. The zero-sequence core is arranged horizontally behind the B-phase core 1, forming a symmetrical magnetic circuit layout. This provides a low-resistance loop for the zero-sequence magnetic flux, improving the accuracy of zero-sequence voltage measurement. Core and coil assembly: The three-phase cores 1 (A, B, and C) are respectively embedded inside the corresponding phase body. Each phase core 1 is wrapped with a core clamp 2, which is used to fix the core 1 and isolate the coil from the core. The secondary coil 8 is wound around one long side of the core 1, and the primary coil 7 is wound around the outside of the secondary coil 8, forming a nested structure of "core-secondary coil-primary coil" to ensure magnetic coupling efficiency. like Figure 4-6 As shown, the resin-coil integrated structure is a key innovation for improving the structural stability and insulation performance of current transformers. Its composition and assembly are as follows: Core components include iron core clamp 2, primary conductive sheet 6, resin bracket 5, and cross-slot countersunk bolt 3. Core clamp 2: Wrapped around the outside of core 1, with four symmetrically distributed support seats 22 integrally formed on the edge. One pair of diagonal support seats 22 are equipped with support frames 23, and the support frames 23 have elliptical countersunk holes. The long axis of the elliptical countersunk holes is reserved for adjustment, which is used to precisely adjust the insulation distance between the primary coil 7 and core 1 and secondary coil 8 to avoid electric field concentration. Primary conductive sheet 6: Fixed to the bottom outer side of the primary coil 7, serving both as a conductive connection and structural support. A mounting base is provided on the primary conductive sheet 6, and a cross-slot countersunk bolt 3 is welded to the mounting base, ensuring that the top of the bolt does not exceed the plane of the mounting base to prevent affecting the electric field distribution. Resin bracket 5: It has a cylindrical structure with a metal insert 4 embedded in its end face. The metal insert 4 has a threaded hole that is compatible with the cross-slot countersunk bolt 3. The resin bracket 5 is connected to the fixing seat of the primary conductive sheet 6 and the support frame 23 of the iron core clamp 2 by bolts, so as to achieve precise positioning of the primary coil 7 and the iron core 1. Assembly Formation: The primary conductive sheet 6, resin bracket 5, and iron core clamp 2 are fastened together by cross-slot countersunk bolts 3, and combined with epoxy resin casting, a resin-coil integrated structure is formed, which improves the overall mechanical strength and insulation reliability. The European-style C-shaped connector 18 is integrated on the top of the main insulator 9 and is arranged horizontally above the three-phase iron cores 1 (A, B, and C). It is used for connection to the high-voltage side of the power grid and integrates a fuse assembly. The specific design is as follows: Fuse cavity: A European-style C-shaped connector 18 has a fuse cavity opened horizontally. The cavity is sequentially fitted with a spring 13, a high-voltage fuse 15, and a bolt sleeve 19. When there is an internal short circuit, overload, or power grid fault in the transformer, the high-voltage fuse 15 can quickly melt and cut off the fault current, preventing high voltage from entering the secondary circuit and protecting the safety of personnel and measuring and protection devices. Multi-layer shielding structure: The inner wall of the fuse cavity is provided with a high-voltage shielding mesh 16, a fuse shielding mesh 14, and a grounding shielding mesh 17 sequentially from the inside to the outside. The high-voltage shielding mesh 16 and the fuse shielding mesh 14 are horizontally fitted inside and outside the cavity, with a gap between them; the grounding shielding mesh 17 is located outside the high-voltage shielding mesh 16. This shielding structure can completely isolate the high and low voltage electric fields, making the electric field inside and outside the product uniform, reducing partial discharge, and ensuring safe and reliable operation.

[0025] like Figure 7 As shown, the zero-sequence coil is arranged laterally behind phase B core 1, and two vertical cylinders are installed above it. The specific design is as follows: Cylindrical structure: The cylindrical surface is equipped with a skirt to improve external insulation performance; the O and N terminals are located at the top of the cylinder for zero-sequence voltage signal output. Internal components: From top to bottom, the cylinder contains a bolt insert 12, a conductive rod 11, and a shielding ring 10. The bolt insert 12 is used to fix the terminal; the conductive rod 11 enables the conductive connection between the zero-sequence coil and the terminal; the shielding ring 10 is used to optimize the electric field distribution and avoid excessively high local electric field strength. The fabrication process of the above-mentioned three-phase five-limb voltage transformer includes the following steps: Core clamp assembly: Fix the core clamp 2 on the long side of the A, B, and C three-phase core 1, ensuring that the support seat 22 of the core clamp 2 fits tightly with the core 1. Coil winding: Wind a secondary coil 8 around the long side of the other side of the iron core 1, and then wind a primary coil 7 around the outside of the secondary coil 8. Control the coil winding tension to be uniform and avoid insulation damage. Primary conductive sheet fixing: Fix the primary conductive sheet 6 below the primary coil 7, ensuring that the cross-slot countersunk bolt 3 welded on the primary conductive sheet 6 fixing seat is coaxial with the elliptical countersunk hole of the iron core clamp 2 support frame 23. Resin bracket connection: Secure one side of the resin bracket 5 to the fixing seat of the primary conductive sheet 6 with bolts, and pre-tighten the other side on the support frame 23 of the iron core clamp 2 to initially position the relative position of the primary coil 7 and the iron core 1. Insulation distance adjustment and fastening: Using the long axis adjustment margin of the elliptical countersunk hole on the iron core clamp 2 support frame 23, adjust the insulation distance between the primary coil 7 and the iron core 1 and the secondary coil 8 to the design value, and then tighten the bolts on the support frame 23 to form a resin-coil integrated structure. Overall assembly and casting: The resin-coil integrated structure of phases A, B, and C is placed vertically and arranged horizontally, and the zero-sequence coil is installed horizontally behind the phase B structure; the entire structure is fixed on the mold base through the threaded holes of the four support seats 22 of the iron core clamp 2, and the coil is connected by YY wiring; finally, epoxy resin vacuum casting is performed, and the main insulator 9 is obtained after molding, thus completing the preparation of the transformer body. Attachment installation: Install the European C-type connector 18 on the top of the main insulator 9, and install the spring 13, high-voltage fuse 15, and bolt sleeve 19 into the fuse cavity to complete the fabrication of the three-phase five-limb voltage transformer. The method of using the three-phase five-limb voltage transformer in this embodiment is as follows: Installation and fixing: Based on the phase sequence distance of the power grid switchgear, use the mounting base 21 of the current transformer to fix the current transformer in the designated position of the switchgear with bolts to ensure a firm installation and avoid vibration during operation. High-voltage side wiring: Connect the high-voltage side lines of the power grid to the three corresponding European C-type connectors 18 (A, B, and C) respectively, ensuring tight wiring and good contact to prevent overheating caused by loose connections. Secondary side wiring: Connect the conductors of the low-voltage side secondary cable to the secondary wiring slot between phases A and B in front of the main insulator 9. Complete the connection of the secondary circuit according to the electrical wiring diagram, ensuring correct polarity and avoiding measurement deviations or equipment damage caused by wiring errors. Operational inspection: After the wiring is completed, the current transformer is visually inspected to confirm that there are no damaged parts or messy wiring. Then, insulation test and withstand voltage test are carried out. Once the test is passed, it can be put into operation to realize the functions of grid voltage measurement and zero-sequence insulation monitoring. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A three-phase five-limb voltage transformer, characterized in that, include: The main insulator is made by vacuum casting of epoxy resin, and its interior has an integrated resin-coil structure, which is convex in shape. The five-column structure is located inside the main insulator and includes the three-phase transformer body (A, B, and C) and the zero-sequence transformer body, which adopts a YY connection method. The three-phase transformer body (A, B, and C) is arranged in front of the five-column structure, and the zero-sequence transformer body is arranged behind the five-column structure, forming a symmetrical magnetic circuit layout. The three-phase iron cores A, B, and C are respectively embedded inside the three-phase transformer body, and each phase iron core is connected to the resin-coil integrated structure of the corresponding phase. European-style C-shaped connectors are arranged horizontally in parallel above the A, B, and C phase iron cores, integrated on the top of the main insulator, and used for wiring connections to the high-voltage side of the power grid.

2. The three-phase five-limb voltage transformer according to claim 1, characterized in that, The main insulator has a rectangular resin covering the A, B, and C phase cores in front of it. The top of the rectangular resin has an inclined surface, and the bottom is flush with the main insulator. The main insulator has C-shaped corners on both sides and a concave shape near the bottom surface. A secondary wiring groove is provided between the A and B phases in front of the main insulator.

3. A three-phase five-limb voltage transformer according to claim 1, characterized in that, The European-style C-shaped connector has a fuse cavity in the horizontal direction, and a spring, a high-voltage fuse, and a bolt sleeve are sequentially assembled in the fuse cavity.

4. A three-phase five-limb voltage transformer according to claim 3, characterized in that, The inner wall of the fuse cavity is provided with a high-voltage shielding mesh, a fuse shielding mesh and a ground shielding mesh in sequence from the inside to the outside; the high-voltage shielding mesh and the fuse shielding mesh are horizontally fitted inside and outside the fuse cavity, with gaps between them.

5. A three-phase five-limb voltage transformer according to claim 1, characterized in that, The three-phase iron cores A, B, and C are all arranged longitudinally, and the zero-sequence coil corresponding to the zero-sequence coil is arranged laterally behind the B-phase iron core. Two vertical cylinders are provided above the zero-sequence coil. The arc surface of the cylinder is provided with a skirt. The O and N terminals are located at the top of the cylinder. The cylinder is provided with a bolt insert, a conductive rod, and a shielding ring from top to bottom.

6. A three-phase five-limb voltage transformer according to claim 1, characterized in that, The resin-coil integrated structure includes: The iron core clamp is wrapped around the outside of the iron core, and its edge is integrally formed with a support base with a support frame; The primary conductive sheet is fixed to the bottom outer side of the primary coil, serving the dual functions of conductive connection and structural support. The resin bracket is connected to the support frame of the primary conductive sheet and the iron core clamp respectively through connectors, thereby achieving precise positioning of the primary coil and the iron core.

7. A three-phase five-limb voltage transformer according to claim 6, characterized in that, The iron core clamp is provided with symmetrically distributed support seats, and a pair of diagonally opposite support seats are respectively provided with support frames, and countersunk holes are opened on the support frames.

8. A three-phase five-limb voltage transformer according to claim 7, characterized in that, The countersunk hole is an elliptical countersunk hole, with an adjustment margin reserved along its major axis to adjust the insulation distance between the primary coil and the iron core, and between the secondary coil and the iron core.

9. A three-phase five-limb voltage transformer according to claim 6, characterized in that, The resin support is a cylindrical structure, and metal inserts are pre-embedded in the end face of the resin support. The metal inserts have threaded holes that are adapted to the connectors.

10. A three-phase five-limb voltage transformer according to claim 9, characterized in that, The connector is a cross-slot countersunk bolt. A fixing seat is provided on the primary conductive sheet, and a cross-slot countersunk bolt is welded on the fixing seat. The top of the cross-slot countersunk bolt does not exceed the plane of the fixing seat.

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