A full-insulation v-shaped combined mutual inductor for state grid

Abstract

This utility model discloses a fully insulated V-type combined instrument transformer for State Grid, relating to the technical field of high-voltage measurement or relay protection equipment in the State Grid power system. It includes an epoxy resin vacuum casting process to integrally encapsulate the current transformer bodies A and C, voltage transformer bodies A and C, primary current terminals P1 and P2, B-phase primary voltage terminals, and secondary terminals, forming a fully insulated integrated main insulator. The primary current terminals P1 and P2 and the B-phase primary voltage terminals extend out of the main insulator, while their lower parts are located within the main insulator and connected to their corresponding current transformer bodies and voltage transformer bodies, respectively. The first high-voltage terminal of the primary voltage winding of voltage transformer bodies A and C is connected to the primary high-voltage busbar of the current transformer via a primary connecting line. The exposed portion of the connection is sealed with semi-conductive rubber tape to shield the primary high-voltage electric field. This application significantly reduces the product size, and combined with semiconductor shielding technology, greatly improves measurement accuracy.

Description

Technical Field

[0001] This utility model relates to the technical field of high-voltage measurement or relay protection equipment for the State Grid power system, specifically to a fully insulated V-type combined instrument transformer for the State Grid. Background Technology

[0002] Currently, there are two main technical solutions for outdoor combined instrument transformers used in power systems: the first is the traditional combined instrument transformer that uses oil-paper insulation and magnetic bottle insulation, and the second is an improved product composed of multiple independent instrument transformers.

[0003] Traditional oil-paper insulated combined instrument transformers, due to their oil-immersed insulation structure, generally suffer from problems such as large size, poor sealing performance leading to oil leakage, and susceptibility to flashover accidents on the outer insulation surface. Furthermore, their dynamic and thermal stability current carrying capacity is low, and their secondary output capacity is insufficient, resulting in frequent maintenance and repairs, and a short service life. They no longer meet the requirements of modern power systems and are gradually being phased out.

[0004] While the multi-unit instrument transformer combination scheme solves the oil leakage problem through oil-free design and improves dynamic and thermal stability current and secondary capacity indicators to some extent, it still has significant drawbacks in practical applications: First, the combination of multiple devices leads to complex installation structures and difficult on-site construction; second, the reliability of mechanical connections and electrical coordination between units is insufficient, affecting long-term operational stability; third, the overall environmental adaptability is poor, making it difficult to meet the requirements of complex outdoor operating conditions. These technical bottlenecks severely restrict the performance improvement of outdoor combined instrument transformers and bring many difficulties to power system operation and maintenance. Utility Model Content

[0005] The purpose of this utility model is to provide a fully insulated V-type combined instrument transformer for State Grid, which has the advantages of small size, large creepage distance, strong anti-interference, high metering accuracy, convenient installation, easy maintenance, stable insulation, and safe operation.

[0006] To achieve the above objectives, the technical solution of this application is as follows: a fully insulated V-type combined instrument transformer for State Grid, comprising an epoxy resin vacuum casting process to encapsulate the current transformer body A and C, the voltage transformer body A and C, the primary current terminals P1 and P2, the B-phase primary voltage terminal and the secondary terminals as a whole, forming a fully insulated integrated main insulator. The primary current terminals P1 and P2 and the B-phase primary voltage terminal extend out of the main insulator at the top and are located inside the main insulator at the bottom, respectively connected to the corresponding current transformer body and voltage transformer body.

[0007] The first high-voltage terminal of the primary winding of voltage transformer body A and C is connected to the primary high-voltage busbar through a primary connection line. The exposed part of the connection is wrapped with semi-conductive rubber tape to shield the primary high-voltage electric field.

[0008] The second high-voltage terminals of the primary voltage windings of voltage transformer bodies A and C are connected via phase B conductive plates, phase B primary voltage terminals, and phase B connecting rods to form a V-shaped connection, thus forming a primary high-voltage phase B terminal; the primary voltage windings are connected to the primary current windings via phase A / C conductive plates and primary connecting wires.

[0009] As a preferred embodiment of this utility model, a high-temperature vulcanized silicone rubber sleeve is formed on the outer sleeve of the main insulator, and the two are bonded together by a single-component silicone rubber.

[0010] As a preferred embodiment of this utility model, the current transformer bodies A and C, and the voltage transformer bodies A and C are arranged side by side in a straight line, wherein the voltage transformer bodies A and C are located in the middle and are electrically connected through the conductive sheet at end B.

[0011] As a preferred embodiment of this utility model, the current transformer bodies A and C both include a current core. The current core is wrapped with an insulating cardboard corner ring, a twill cloth tape insulating layer, and a polyurethane board buffer layer from the inside out for multi-layer insulation treatment. Then, a layer of self-adhesive tape is half-overlapped and enameled round copper wire is wound as a secondary winding. After the winding is completed, a layer of polyester film is half-overlapped and a shaped copper foil or aluminum foil is added to the outer layer as a shielding layer. Finally, a layer of semi-conductive crepe paper shielding layer is half-overlapped and the current secondary support is fixed.

[0012] As a preferred embodiment of this utility model, the primary current windings of the current transformer bodies A and C adopt a through-core structure and are wound through the current iron core, with primary high-voltage conductive busbars welded to both ends.

[0013] In a preferred embodiment of this utility model, both voltage transformer bodies A and C include a voltage core. A layer of insulating paperboard is wound on the voltage core and covered with multiple layers of PMP composite paper to form a basic insulation layer. A secondary voltage winding is wound outside the basic insulation layer, with PMP composite paper used as insulation between the winding layers. Semi-conductive crepe paper is wound around the outer layer of the secondary winding to form a low-voltage shielding layer. The assembly with the voltage core and secondary winding is fitted into an open insulating frame. Molded copper foil and semi-conductive crepe paper are added outside the open insulating frame to form an inner shielding layer. After covering with a layer of DMD insulating paper, a primary voltage winding is wound. After the primary winding is wound, a molded copper foil shielding layer is covered on the outside.

[0014] As a preferred embodiment of this utility model, the voltage core, excluding the voltage secondary winding wrapping part, is wrapped from the inside out with a layer of self-adhesive tape insulation layer, a molded polyurethane board buffer layer, another layer of self-adhesive tape insulation layer, an outer molded copper foil or aluminum foil shielding layer, and finally a layer of semi-conductive crepe paper to form a low-voltage shielding layer. Semi-conductive paint is then applied to both sides of the wrapped voltage core.

[0015] As a preferred embodiment of this utility model, a secondary junction box is processed at the lower part of the main insulator. The secondary junction box has built-in secondary terminals, which are respectively connected to the corresponding current transformer body A and C, and the voltage transformer body A and C.

[0016] As a preferred embodiment of this utility model, the upper outer wall of the main insulator is provided with multiple silicone umbrella skirts, which are distributed around the outer periphery of the primary current terminals P1, P2 and the primary voltage terminal of phase B; multiple silicone umbrella skirts are also provided on the outer side of the middle part of the main insulator.

[0017] As a preferred embodiment of this utility model, the primary current terminals P1 and P2 of the current transformer bodies A and C are symmetrically arranged, and the primary current terminals P1 and P2 of the same phase are arranged in a V-shape.

[0018] By adopting the above technical solution, this utility model can achieve the following technical effects:

[0019] 1. Small size, strong anti-interference, and high metering accuracy: The optimized structural design features the current and voltage transformers arranged side by side in a straight line, with the voltage transformer positioned in the middle. This makes the structure more compact and saves space, resulting in a small size and large capacity. The coils use shielding materials such as copper foil or non-magnetic aluminum foil and semi-conductive crepe paper to avoid mutual interference between the electromagnetic fields of the current and voltage, as well as between adjacent phases. This results in strong anti-interference and high metering accuracy, making it more suitable for use in various environments, including harsh outdoor weather conditions.

[0020] 2. Easy installation, remote identification, and easy maintenance: When installing and using the product, simply fix the current transformer in place and connect the primary and secondary wires according to the phase sequence, effectively saving assembly time; the product is also simpler to repair, requiring no special maintenance work.

[0021] 3. Stable insulation and safe operation: It adopts epoxy resin inner insulation and epoxy resin outer silicone rubber material for outer insulation. It has a high withstand voltage rating and reliable insulation, ensuring safer operation.

[0022] 4. Large creepage distance and protection against flashover: The primary AC phase current terminals extend to both sides, and multiple silicone umbrella skirts are distributed on the outer wall of the high-voltage end and the main body of the product, resulting in a large creepage distance. The primary ABC three-phase high-voltage ends are equipped with protective covers for sealing, protecting the high voltage from leakage and flashover, making the product safer to operate. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram of the internal structure of a fully insulated V-type combined instrument transformer for State Grid.

[0025] Figure 2 Side view of a fully insulated V-type combined instrument transformer for State Grid;

[0026] Figure 3 Front view of a fully insulated V-type combined instrument transformer for State Grid;

[0027] Figure 4 Top view of a fully insulated V-type combined instrument transformer for State Grid;

[0028] The numbers in the diagram are explained as follows: 1. Primary high-voltage conductor busbar; 2. Primary current winding; 3. Current core; 4. Secondary current winding; 5. Secondary current support; 6. Phase B primary voltage terminal; 7. Phase B connecting rod; 8. Phase A / C conductive sheet; 9. Primary connecting wire; 10. Phase B conductive sheet; 11. Primary voltage winding; 12. Voltage core; 13. Secondary voltage winding; 14. Body clamp; 15. Secondary terminal block; 16. Main insulator; 17. Silicone umbrella skirt; 18. Nameplate; 19. Base; 20. Secondary cover plate; 21. Secondary rubber pad; 22. Electronic tag. Detailed Implementation

[0029] It should be noted that, where there is no conflict, the embodiments and features in the embodiments of this utility model can be combined with each other. The present utility model will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this utility model or its application or use. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] In the description of this utility model, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms 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, and therefore should not be construed as a limitation on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0034] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0035] It should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections 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 based on the specific circumstances.

[0036] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this utility model.

[0037] Please see Figure 1-4 This embodiment provides a method for manufacturing a fully insulated V-type combined instrument transformer for State Grid, specifically including:

[0038] The current transformer bodies A and C are positioned in the casting mold through the current secondary support 5; at the same time, the voltage transformer bodies A and C are fixed in the casting mold through the body clamp 14.

[0039] The first high-voltage terminal of the voltage primary winding is fixed to the mold process hole through the A / C phase conductive sheet 8, and connected to the current primary high-voltage conductor bus 1 through the primary connection line 9. The exposed part of the connection is wrapped with semi-conductive rubber tape to shield the primary high-voltage electric field.

[0040] The second high voltage terminal of the primary voltage winding is connected to the primary high voltage B-phase terminal by the B-phase conductive sheet 10, the primary voltage terminal 6 of the B-phase, and the B-phase connecting rod 7 to form a V-type connection; the primary voltage winding 11 is connected to the primary current winding 2 by the A / C phase conductive sheet 8 and the primary connecting line 9.

[0041] According to the corresponding markings, the secondary leads of current transformer body A and C and the secondary leads of voltage transformer body A and C are connected to the corresponding secondary terminals 15 on the secondary terminal block; the distance is adjusted and the main insulator 16 is made of epoxy resin by vacuum casting; preferably, the secondary terminal block 15 is surrounded by a secondary junction box made of silicone rubber, and the secondary junction box is connected by a detachable secondary rubber pad 21 and a secondary cover plate 20, which can both facilitate wiring and provide a sealing function.

[0042] A molded high-temperature vulcanized silicone rubber sleeve is then fitted over the main insulator. The two are bonded together with a single-component silicone rubber. After curing in a constant temperature and humidity treatment chamber, the entire product is finally installed on the grooved base 19 to ensure that it meets the usage requirements in different outdoor environments.

[0043] As a preferred embodiment provided in this example, the current transformer body A and C include a current core. The current core is wrapped with an insulating cardboard corner ring, a twill cloth tape insulating layer and a polyurethane board buffer layer from the inside to the outside for multi-layer insulation treatment. Then, a layer of self-adhesive tape is half-overlapped and enameled round copper wire is wound as the secondary winding of the current. After the winding is completed, a layer of polyester film is half-overlapped and a shaped copper foil or aluminum foil is added to the outer layer as a shielding layer. Finally, a layer of semi-conductive crepe paper shielding layer is half-overlapped and the secondary current support is fixed.

[0044] The current core made of amorphous alloy is subjected to multi-layer insulation treatment: from the inside out, it is wrapped with an insulating cardboard corner ring, a twill cloth tape insulating layer, and a polyurethane board buffer layer; then a layer of self-adhesive tape is half-overlapped, and then enameled round copper wire is wound as the secondary winding of the current; after the winding is completed, a layer of polyester film is half-overlapped, and a shaped copper foil or aluminum foil is added to the outer layer as a shielding layer; finally, a layer of semi-conductive crepe paper shielding layer is half-overlapped, and the secondary current support is fixed.

[0045] The primary winding of the current circuit adopts a through-core structure, winding through the current core. High-voltage conductive busbars are welded to both ends, and insulation is applied in the following order from the inside out: first, a layer of twill tape is wrapped in half-overlap, then a layer of crepe paper is wrapped in half-overlap, and finally a layer of semi-conductive crepe paper is wrapped in half-overlap; forming the current circuit bodies A and C.

[0046] As a preferred embodiment provided in this example, the method for manufacturing the voltage transformer body is as follows:

[0047] The voltage core adopts a closed-loop toroidal structure. First, an insulating paperboard is wound on the toroidal core, and then multiple layers of PMP composite paper are wrapped around it to form a basic insulation layer. The voltage secondary winding is wound outside the insulation layer, and PMP composite paper is used as insulation between the winding layers. Semi-conductive corrugated paper is wound around the outer layer of the secondary winding to form a low-voltage shielding layer.

[0048] The assembly with the iron core and secondary winding is fitted into an open insulating frame and fixed as a whole on a CNC parallel winding machine. An inner shielding layer is formed by adding shaped copper foil and semi-conductive corrugated paper to the outside of the insulating frame, and then a layer of DMD insulating paper is wrapped around it before winding the voltage primary winding; after the primary winding is completed, an outer shaped copper foil shielding layer is covered.

[0049] A / C phase conductive sheets and B phase conductive sheets are welded using a welding jig, and then a high-voltage shielding layer is formed by wrapping semi-conductive corrugated paper around the outer layer. The voltage core is reliably fixed to the clamping parts of the transformer body by passing a metal hose clamp through the gap between the outer side of the iron core and the basic insulation layer and using a positioning jig threaded fastener.

[0050] Except for the secondary coil wrapping, the voltage core undergoes the following treatment from the inside out: a half-overlapping layer of self-adhesive tape insulation, an added molded polyurethane board buffer layer, another half-overlapping layer of self-adhesive tape insulation, an outer molded copper foil or aluminum foil shielding layer, and finally a half-overlapping layer of semi-conductive crepe paper to form a low-voltage shielding layer. Appropriate widths of semi-conductive paint are then applied to both sides of the wrapped voltage core to form voltage transformer bodies A and C.

[0051] In this embodiment, the purpose of using semi-conductive crepe paper and semi-conductive paint for the current transformer body and voltage transformer body is to shield or equalize the electric field, thereby reducing the partial discharge of the combined transformer. The use of copper foil fully considers the mutual influence of electromagnetic fields between the current and voltage during the operation of the transformer, ensuring higher stability, reliability and accuracy of product measurement.

[0052] In this embodiment, after the current and voltage circuit bodies are processed by the cluster vacuum drying equipment, they are first fully dried in the layered drying chamber, and then stored in groups according to specifications and fixed in sealed boxes to ensure that the components remain dry before molding and effectively prevent moisture absorption.

[0053] In this embodiment, primary current terminals P1 and P2 are provided on the upper part of the primary high-voltage busbar 1. They are arranged symmetrically on the left and right sides of phases A and C, and the terminals P1 and P2 of each phase are arranged symmetrically front and back to form a balanced electrical structure. The primary voltage terminal 6 of phase B is located on the upper part of the primary high-voltage phase B terminal. The periphery of the primary high-voltage phase B terminal is provided with silicone rubber skirts of different sizes. These skirts increase the creepage distance and effectively prevent arc flashover. Even in harsh environments such as humid and dirty conditions, they can provide reliable insulation protection for the equipment. Multiple silicone skirts 17 are provided on the outer periphery of the main insulator 16. The upper part transitions to the high-voltage end in an arc shape. The multi-segment umbrella-shaped structure effectively increases the creepage distance and improves the insulation performance. The geometric shape of the skirts disperses the electric field stress, avoids electric field concentration, and improves the overall operational reliability of the equipment.

[0054] In this embodiment, the nameplate 18 is located on one side of the main insulator near the grooved base 19 for easy viewing; the State Grid special electronic tag 22 is attached to the secondary terminal 15 with silicone and can be scanned from a distance to remotely identify and query product-related information.

[0055] The advantages of this implementation lie in its use of an epoxy resin-silicone rubber composite insulation system, achieving optimized electric field distribution through a double-layer insulation structure. The application of copper foil or non-magnetic aluminum foil in the coil, combined with shielding materials such as semi-conductive crepe paper, effectively suppresses electromagnetic interference between current and voltage windings and between phases, fundamentally solving the technical defects of traditional equipment. The unique V-shaped structure design significantly reduces the product's size, and the semiconductor shielding layer technology greatly improves measurement accuracy. Combined with an optimized skirt structure design and reliable sealing technology, this product fully meets the stringent requirements of various outdoor application scenarios in smart grids. During installation and use, simply install the current transformer mounting bracket, perform the primary and secondary wiring according to the phase sequence, and finally seal the A, B, and C three-phase high-voltage terminals with protective covers. It boasts advantages such as small size, large creepage distance, strong anti-interference, high metering accuracy, convenient installation, easy maintenance, stable insulation, and safe operation, further enhancing the design and manufacturing level of combined current transformers.

[0056] 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 fully insulated V-type combined instrument transformer for State Grid, characterized in that, The process involves using epoxy resin vacuum casting to encapsulate the current transformer body A and C, the voltage transformer body A and C, the primary current terminals P1 and P2, the primary voltage terminal of phase B, and the secondary terminals as a whole, forming a fully insulated integrated main insulator. The primary current terminals P1 and P2 and the primary voltage terminal of phase B extend out of the main insulator at the top and are located inside the main insulator at the bottom, respectively connected to the corresponding current transformer body and voltage transformer body. The first high-voltage terminal of the primary winding of voltage transformer body A and C is connected to the primary high-voltage busbar through a primary connection line. The exposed part of the connection is wrapped with semi-conductive rubber tape to shield the primary high-voltage electric field. The second high-voltage terminals of the primary voltage windings of voltage transformer bodies A and C are connected via phase B conductive plates, phase B primary voltage terminals, and phase B connecting rods to form a V-shaped connection, thus forming a primary high-voltage phase B terminal; the primary voltage windings are connected to the primary current windings via phase A / C conductive plates and primary connecting wires.

2. The State Grid fully insulated V-type combined instrument transformer according to claim 1, characterized in that, The main insulator is covered with a high-temperature vulcanized silicone rubber sleeve, and the two are bonded together with a single-component silicone rubber.

3. The State Grid fully insulated V-type combined instrument transformer according to claim 1, characterized in that, The current transformer bodies A and C, and the voltage transformer bodies A and C are arranged side by side in a straight line, with the voltage transformer bodies A and C located in the middle and electrically connected through the conductive plate at end B.

4. The State Grid fully insulated V-type combined instrument transformer according to claim 1, characterized in that, Both current transformer bodies A and C include current cores. The current cores are wrapped with insulating cardboard corner rings, twill tape insulating layers, and polyurethane board buffer layers from the inside out for multi-layer insulation treatment. Then, a layer of self-adhesive tape is half-overlapped and enameled round copper wire is wound as a secondary winding. After winding, a layer of polyester film is half-overlapped and a shaped copper foil or aluminum foil is added to the outer layer as a shielding layer. Finally, a layer of semi-conductive crepe paper shielding layer is half-overlapped and the current secondary support is fixed.

5. The State Grid fully insulated V-type combined instrument transformer according to claim 1, characterized in that, The primary windings of the current transformer bodies A and C adopt a through-core structure and are wound through the current iron core, with primary high-voltage busbars welded to both ends.

6. The State Grid fully insulated V-type combined instrument transformer according to claim 1, characterized in that, Both voltage transformer bodies A and C include a voltage core. A layer of insulating paperboard is wound on the voltage core and covered with multiple layers of PMP composite paper to form a basic insulation layer. A secondary voltage winding is wound outside the basic insulation layer, with PMP composite paper used as insulation between the winding layers. Semi-conductive crepe paper is wound around the outer layer of the secondary winding to form a low-voltage shielding layer. The assembly with the voltage core and secondary winding is fitted into an open insulating frame. Molded copper foil and semi-conductive crepe paper are added outside the open insulating frame to form an inner shielding layer. After covering with a layer of DMD insulating paper, a primary voltage winding is wound. After the primary winding is wound, a molded copper foil shielding layer is covered on the outside.

7. A fully insulated V-type combined instrument transformer for State Grid as described in claim 6, characterized in that, Except for the voltage secondary winding, the voltage core is wrapped from the inside out with a layer of self-adhesive tape insulation layer, a molded polyurethane board buffer layer, another layer of self-adhesive tape insulation layer, a molded copper foil or aluminum foil shielding layer, and finally a layer of semi-conductive crepe paper to form a low-voltage shielding layer. Semi-conductive paint is then applied to both sides of the wrapped voltage core.

8. The State Grid fully insulated V-type combined instrument transformer according to claim 1, characterized in that, A secondary junction box is machined at the bottom of the main insulator. The secondary junction box contains secondary terminals, which are respectively connected to the corresponding current transformer body A and C, and the voltage transformer body A and C.

9. A fully insulated V-type combined instrument transformer for State Grid as described in claim 1, characterized in that, The upper outer wall of the main insulator is provided with multiple silicone umbrella skirts, which are distributed around the outer periphery of the primary current terminals P1, P2 and the primary voltage terminals of phase B; multiple silicone umbrella skirts are also provided on the outer side of the middle part of the main insulator.

10. A fully insulated V-type combined instrument transformer for State Grid as described in claim 1, characterized in that, The primary current terminals P1 and P2 of the current transformer bodies A and C are symmetrically arranged, and the primary current terminals P1 and P2 of the same phase are arranged in a V-shape.

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