Power transformer and electric facility

Abstract

To provide a novel structure which achieves improvement of insulation performance against high-frequency surges.SOLUTION: In a gas VT (1), a primary coil (18) is provided coaxially with a secondary coil (13) at the outer side of the secondary coil (13). The gas VT (1) includes a primary side shield layer (17) and a secondary side shield layer (15) provided between the primary coil (18) and the secondary coil (13). The secondary side shield layer (15) is wider than any of the primary coil (18), the secondary coil (13), and the primary side shield layer (17). A distance between an end (31) of the primary side shield layer (17) and the secondary side shield layer (15) is longer than a distance between a center part (32) of the primary side shield layer (17) and the secondary side shield layer (15).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a transformer and an electric equipment. More specifically, the present invention relates to a transformer having a primary coil disposed coaxially with a secondary coil outside the secondary coil, and to an electric equipment including the transformer. [Background technology]

[0002] Gas-insulated voltage transformers are used as one of the components of gas-insulated switchgear installed in electric power facilities. Hereinafter, such gas-insulated voltage transformers are referred to as "gas VTs (Voltage Transformers)." The gas VT is placed in a space filled with insulating gas such as SF6 gas, and transforms the high voltage on the primary side into a measurable voltage with high precision. The gas VT is disclosed in, for example, Patent Document 1.

[0003] The gas VT comprises an iron core, a primary coil (high voltage coil), and a secondary coil (low voltage coil). The secondary coil is wound around the iron core. The primary coil is wound around the secondary coil coaxially with the secondary coil. In a gas VT with the above configuration, if a high-frequency surge flows in from the high-voltage side of the primary coil, a high voltage is transferred to the secondary coil, and there is a possibility that insulation breakdown will occur in the secondary coil and / or in a circuit electrically connected to the secondary coil.

[0004] Therefore, a gas VT having two shield layers between the primary coil and the secondary coil is known. Hereinafter, the shield layer closer to the primary coil is referred to as the primary-side shield layer, and the shield layer closer to the secondary coil is referred to as the secondary-side shield layer. In this case, the high-frequency surge flowing in from the high-voltage side of the primary coil is mitigated by the two shield layers. As a result, it is possible to suppress the transfer of high voltage to the secondary coil. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2002-313639 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, near the end of the primary shield layer, the equipotential lines curve with a small radius of curvature, which increases the potential gradient of the equipotential lines near the end, which may cause dielectric breakdown.

[0007] In contrast, in the gas VT described in Patent Document 1, the width of the primary shield layer is made wider than the width of the secondary shield layer, which makes it possible to reduce the electric field near both ends of the primary shield layer, thereby making it possible to suppress the dielectric breakdown.

[0008] An object of one aspect of the present invention is to provide a transformer having a new structure with improved insulation performance against high-frequency surges. [Means for solving the problem]

[0009] In order to solve the above problems, a transformer according to one embodiment of the present invention is a transformer in which a primary coil is arranged coaxially with a secondary coil outside the secondary coil, and which comprises a primary side shielding layer and a secondary side shielding layer arranged between the primary coil and the secondary coil, wherein the width of the secondary side shielding layer is wider than the width of the primary coil, the width of the secondary coil, and the width of the primary side shielding layer, and the distance between the end of the primary side shielding layer and the secondary side shielding layer is longer than the distance between the center of the primary side shielding layer and the secondary side shielding layer. Effect of the Invention

[0010] According to one aspect of the present invention, it is possible to provide a transformer having a new structure with improved insulation performance against high-frequency surges. [Brief description of the drawings]

[0011] [Figure 1] 1 is a vertical cross-sectional view showing half of a gas-insulated instrument transformer according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing a quarter portion of the gas-insulated potential transformer. [Diagram 3] FIG. 2 is an equivalent circuit diagram of the gas-insulated instrument transformer. [Figure 4] 2 is a schematic diagram showing an arrangement of a secondary coil, a secondary shield layer, and a primary shield layer in the above-mentioned gas-insulated instrument transformer, and a distribution of equipotential lines in the primary shield layer. FIG. [Diagram 5] 1 is a schematic diagram showing the arrangement of a secondary coil, a secondary shield layer, and a primary shield layer in a conventional gas-insulated instrument transformer, and the distribution of equipotential lines in the primary shield layer. FIG. [Figure 6] FIG. 11 is a vertical cross-sectional view showing half of a gas-insulated instrument transformer according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described in detail. For the sake of convenience, the same reference numerals will be used to designate members having the same functions as those in the embodiments, and descriptions thereof will be omitted as appropriate.

[0013] [Embodiment 1] An embodiment of the present invention will be described in detail with reference to FIGS.

[0014] Fig. 1 is a longitudinal sectional view showing half of a gas VT (gas-insulated instrument transformer) according to this embodiment. Fig. 2 is a transverse sectional view showing 1 / 4 of the gas VT. As shown in Figs. 1 and 2, the gas VT1 (transformer) of this embodiment includes an iron core 11, a secondary winding 12, a secondary coil 13, a primary winding 14, a secondary shield layer 15, an insulating layer 16, a primary shield layer 17, and a primary coil 18.

[0015] The iron core 11 is a laminate of steel plates. The secondary winding form 12 is an insulator such as plastic that is disposed around the iron core 11. The secondary coil 13 is a low-voltage coil that is wound around the outside of the secondary winding form 12. Specifically, the cylindrical secondary winding form 12 around which the secondary coil 13 is wound in advance is fitted into the iron core 11 and fixed to legs (not shown) of the iron core 11.

[0016] The primary winding form 14 is an insulator such as plastic, and is disposed coaxially with the secondary coil 13 outside the secondary coil. A secondary shield layer 15, an insulating layer 16, and a primary shield layer 17 are laminated on the outside of the cylindrical primary winding form 14, and the primary coil 18 is wound around the outside of these. Therefore, it can be said that the iron core 11 is provided on the axis of the secondary coil 13 and the primary coil 18.

[0017] The secondary shield layer 15 is a conductor such as copper, is disposed along the outer periphery of the primary winding 14, and is provided so as not to form a single turn. For example, the secondary shield layer 15 may be a metal foil such as copper foil. The insulating layer 16 is an insulator such as plastic provided on the secondary shield layer 15. For example, the insulating layer 16 may be formed by winding an insulating film onto the secondary shield layer 15 until it reaches a predetermined thickness.

[0018] The primary shield layer 17 is a conductor such as copper, is disposed along the outer periphery of the insulating layer 16, and is provided so as not to form a single turn. For example, the primary shield layer 17 may be a metal foil such as copper foil. The primary coil 18 is a high-voltage coil, is provided around the outer periphery of the primary shield layer 17, and is wound in multiple layers with insulating films interposed between the layers.

[0019] Fig. 3 is a circuit diagram including an equivalent circuit of the gas VT1. As shown in Fig. 3, the gas VT1 is accommodated in a metal container 21 (see Fig. 3) of a gas-insulated switchgear in which insulating gas such as SF6 gas is sealed and kept at ground potential.

[0020] 1 and 3, the primary shield layer 17 is electrically connected to the beginning of the winding of the primary coil 18, and is also connected to a ground terminal 23 electrically connected to the container 21 via a primary shield layer ground lead wire 22. To enable measurement of the earth insulation resistance of the primary coil 18 with a megger, the primary shield layer ground lead wire 22 is drawn out of the container 21 in a state insulated from the container 21, and then connected to the ground terminal 23 provided on the outer surface of the container 21. For this reason, the primary shield layer ground lead wire 22 becomes long, and the reactance X becomes large.

[0021] The secondary shield layer 15 is insulated from the primary shield layer 17 by an insulating layer 16. The secondary shield layer 15 is connected to a ground point e set on the iron core 11 or a portion having the same potential as the iron core 11 (for example, a fastening metal fitting for the iron core 11) via a secondary shield layer ground lead wire 24 of a necessary minimum length that has low reactance. Therefore, the primary shield layer 17 is connected to the ground point e via the electrostatic capacitance C between the primary shield layer 17 and the secondary shield layer 15.

[0022] As described above, the reactance X of the ground lead wire 22 for the primary shield layer increases, and when a high-frequency surge flows in from the high-voltage side of the primary coil 18, the reactance X of the ground lead wire 22 for the primary shield layer increases the potential of the primary shield layer 17. This may cause a dielectric breakdown in the vicinity of the primary shield layer 17. This dielectric breakdown may appear as a layer dielectric breakdown occurring between layers of the primary coil 18, or as a creeping discharge breakdown starting from the end of the primary shield layer 17, and which form it takes depends on the design insulation strength of each. In addition, when the potential of the primary shield layer 17 increases, a high voltage may be transferred to the secondary coil 13 due to electrostatic induction between the primary shield layer 17 and the secondary coil 13, causing a dielectric breakdown on the secondary side.

[0023] Therefore, the secondary shield layer 15, which is electrically connected to the iron core 11 by a secondary shield layer ground lead wire 24 of the minimum necessary length and has low reactance, and is at ground potential, is arranged to face the primary shield layer 17. This forms a capacitance C between the primary shield layer 17 and the ground, and high-frequency surges can be bypassed via this capacitance C. As a result, the rise in potential of the primary shield layer 17 and the secondary coil 13 can be suppressed.

[0024] Furthermore, in this embodiment, the width of the secondary shield layer 15 is wider than the widths of the secondary coil 13, the primary shield layer 17, and the primary coil 18. This ensures that high-frequency surges from the primary coil 18 are bypassed, and that an increase in the potential of the secondary coil 13 is reliably suppressed. Here, the width refers to the length of the primary coil 18 and the secondary coil 13 in the direction of the winding axis.

[0025] Fig. 4 is a schematic diagram showing the arrangement of the secondary coil 13, secondary shield layer 15, and primary shield layer 17 in the gas VT1 of this embodiment, and the distribution of equipotential lines in the primary shield layer 17. Fig. 5 is a schematic diagram showing the arrangement of the secondary coil 113, secondary shield layer 115, and primary shield layer 117 in a conventional gas VT101 as a comparative example, and the distribution of equipotential lines in the primary shield layer 117.

[0026] In the conventional gas VT101, as shown in Fig. 5, the distance between the secondary shield layer 115 and the primary shield layer 117 is constant. Therefore, the equipotential lines curve with a small radius of curvature near the end 131 of the primary shield layer 117. As a result, the potential gradient of the equipotential lines becomes large near the end 131 of the primary shield layer 117, and dielectric breakdown may occur.

[0027] 1 and 4, in the case of gas VT1 of the present embodiment, the distance between both ends 31·31 of the primary shield layer 17 and the secondary shield layer 15 is longer than the distance between a central portion 32 of the primary shield layer 17 and the secondary shield layer 15. Specifically, as shown in Fig. 1 and 4, the distance between each end 31 of the primary shield layer 17 and the secondary shield layer 15 increases from the central portion 32 of the primary shield layer 17 toward the tip.

[0028] 4, the equipotential lines are curved with a larger radius of curvature near the end 31 of the primary shield layer 17 than the radius of curvature near the conventional end 131. As a result, the potential gradient of the equipotential lines near the end 31 of the primary shield layer 17 is smaller than that near the conventional end 131, reducing the possibility of dielectric breakdown. In other words, the insulation performance against high-frequency surges from the primary coil 18 can be improved.

[0029] In addition, in the gas VT1 of this embodiment, the insulating layer 16 has a shape that matches the shape of the primary-side shield layer 17. Specifically, as shown in Fig. 1, each end 33 of the insulating layer 16 becomes thicker from the side of the central portion 34 of the insulating layer 16 toward the tip. This allows the insulating layer 16 to support each end 31 of the primary-side shield layer 17, and as a result, it is possible to prevent the shape of each end 31 of the primary-side shield layer 17 from changing.

[0030] <Modification> The distance between one of the ends 31 of the primary shield layer 17 and the secondary shield layer 15 may be longer than the distance between the center portion 32 of the primary shield layer 17 and the secondary shield layer 15. In this case, the possibility of dielectric breakdown occurring near the one end 31 can be reduced.

[0031] [Embodiment 2] Another embodiment of the present invention will now be described with reference to FIG.

[0032] Fig. 6 is a vertical cross-sectional view showing half of the gas VT according to this embodiment. Note that the iron core 11, the secondary winding 12, and the secondary coil 13 are omitted in Fig. 6. The gas VT1 of this embodiment is different from the gas VT1 shown in Fig. 1 in the structure of the primary shield layer 17, but the other configurations are the same.

[0033] In the primary shield layer 17 shown in Fig. 1, both end portions 31 and the central portion 32 are integrally formed. In contrast, in the primary shield layer 17 of the present embodiment, as shown in Fig. 6, the end portions 31 and the central portion 32 are separate bodies.

[0034] In this embodiment, connection parts 35 are provided for electrically connecting each end part 31 and the central part 32. The connection parts 35 are fixed to each end part 31 and the central part 32 by soldering. The connection parts 35 may be fixed to each end part 31 and the central part 32 by a conductive adhesive. Also, each end part 31 and the central part 32 may be electrically connected by soldering. In this case, the solder corresponds to the connection parts 35.

[0035] Each end portion 31, the central portion 32, and the connecting portion 35 may be a metal foil such as a copper foil. From the viewpoint of ease of manufacture, the structure of either the gas VT1 shown in FIG. 1 or the gas VT1 shown in FIG. 6 may be selected.

[0036] <Additional Notes> In the above embodiment, the present invention is applied to the gas VT1, but the present invention is not limited to the gas VT1. The present invention can be applied to any transformer in which a primary coil is provided coaxially with a secondary coil outside the secondary coil. For example, the present invention can be applied to a power voltage transformer that utilizes the technology of instrument transformers.

[0037] In the above embodiment, the present invention is applied to a gas-insulated switchgear including a gas VT1, but the present invention is not limited to the gas-insulated switchgear. The present invention can be applied to any electrical equipment including a transformer in which a primary coil is provided coaxially with a secondary coil outside the secondary coil. For example, the present invention can be applied to a power supply system including the above-mentioned power supply voltage transformer.

[0038] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0039] 〔summary〕 The transformer according to aspect 1 of the present invention is a transformer having a primary coil arranged coaxially with the secondary coil outside the secondary coil, and further comprising a primary side shielding layer and a secondary side shielding layer arranged between the primary coil and the secondary coil, the width of the secondary side shielding layer being wider than the width of the primary coil, the width of the secondary coil, and the width of the primary side shielding layer, and the distance between the end of the primary side shielding layer and the secondary side shielding layer being longer than the distance between the center of the primary side shielding layer and the secondary side shielding layer.

[0040] According to the above configuration, the width of the secondary shield layer is wider than the widths of the secondary coil, the primary shield layer, and the primary coil, thereby enabling the secondary shield layer to reliably bypass high-frequency surges from the primary coil and reliably suppress an increase in potential of the secondary coil.

[0041] In addition, the distance between the end of the primary shield layer and the secondary shield layer is longer than the distance between the center of the primary shield layer and the secondary shield layer. This causes the equipotential lines to curve with a larger radius of curvature near the end of the primary shield layer than in the past. As a result, the potential gradient of the equipotential lines near the end of the primary shield layer is smaller than near the end of the conventional method, reducing the possibility of dielectric breakdown. In other words, the insulation performance against high-frequency surges from the primary coil can be improved.

[0042] A transformer according to a second aspect of the present invention is, in the above-mentioned first aspect, such that the distance between the end of the primary shield layer and the secondary shield layer increases from the central portion of the primary shield layer toward the tip.

[0043] A transformer according to a third aspect of the present invention is characterized in that, in the above-mentioned first or second aspect, the primary side shield layer may include the central portion, the end portions which are separate from the central portion, and connection portions for electrically connecting the central portion and the end portions.

[0044] A transformer according to a fourth aspect of the present invention, in accordance with the first to third aspects, further includes an insulating layer provided between the primary shield layer and the secondary shield layer, and the insulating layer may have a shape that matches the shape of the primary shield layer. In this case, the insulating layer can support the end of the primary shield layer, thereby preventing the shape of the end of the primary shield layer from changing.

[0045] A fifth aspect of the present invention relates to a transformer according to any one of the first to fourth aspects, wherein the primary shielding layer and the secondary shielding layer are made of a metal foil such as a copper foil.

[0046] The transformer according to a sixth aspect of the present invention, in accordance with any one of the first to fifth aspects, may further include an iron core provided on an axis of the primary coil and the secondary coil.

[0047] An electrical equipment according to a seventh aspect of the present invention includes the transformer according to any one of the first to sixth aspects. In this case, the same effects as those described above are achieved. [Explanation of symbols]

[0048] 1 Gas VT (transformer) 11 Iron Core 12 Secondary winding type 13 Secondary coil 14 Primary winding type 15 Secondary shield layer 16 Insulating layer 17 Primary shield layer 18 Primary coil 21 Container 22 Ground lead for primary shield layer 23 Ground terminal 24 Secondary shield ground lead 31 End 32 Central part 33 End 34 Central part 35 Connection

Claims

1. A transformer in which a primary coil is provided coaxially with a secondary coil outside the secondary coil, a primary shield layer and a secondary shield layer provided between the primary coil and the secondary coil, a width of the secondary shield layer is wider than a width of the primary coil, a width of the secondary coil, and a width of the primary shield layer; A transformer, wherein a distance between an end portion of the primary shield layer and the secondary shield layer is longer than a distance between a center portion of the primary shield layer and the secondary shield layer.

2. 2. The transformer according to claim 1, wherein the distance between the end of the primary shield layer and the secondary shield layer increases from the center of the primary shield layer toward the tip.

3. 2. The transformer according to claim 1, wherein the primary shield layer comprises the central portion, the end portion that is separate from the central portion, and a connection portion for electrically connecting the central portion and the end portion.

4. an insulating layer provided between the primary shield layer and the secondary shield layer, 2. The transformer of claim 1, wherein the insulating layer has a shape that matches a shape of the primary shield layer.

5. The transformer according to claim 1 , wherein the primary shield layer and the secondary shield layer are metal foils.

6. The transformer of claim 1 , further comprising an iron core provided on an axis of the primary coil and the secondary coil.

7. An electrical installation comprising a transformer according to any one of claims 1 to 6.

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