JP5849617B2 - Mold current transformer - Google Patents

Description

  The present invention relates to a mold current transformer mounted in a gas insulated switchgear.

  The configuration of a conventional mold current transformer (Patent Document 1) is shown in FIG. Reference numeral 6 denotes a main circuit conductor, and a current transformer body 9 is arranged so as to surround the main circuit conductor 6 in the circumferential direction. The current transformer main body 9 is provided with a shield electrode 8. Further, the main circuit conductor 6 and the shield electrode 8 are fixed with an insulator 14. Here, in order to ensure insulation between the main circuit conductor 6 on the high voltage side and the shield electrode 8 on the low voltage side, the insulator 14 is formed in a size having a sufficient insulation distance in the axial direction.

JP 9-232170 A

  In the current transformer as in the above-mentioned Patent Document 1, the triple point formed by the contact portion of the insulating gas, the main circuit conductor 6 and the solid insulator 14 and the contact point of the insulating gas, the electric field shield 8 and the solid insulator 14 are used. The triple point which consists of a part was made and the triple point generate | occur | produced in two places. For this reason, two triple points become weak points on insulation, so it is necessary to make the insulator 14 large in the axial direction or radial direction, which hinders downsizing of the device.

  In addition, when installing in a switchgear that uses a gas with low insulation, for example, dry air, it is necessary to further increase the insulation in the axial direction or radial direction in order to increase the creepage distance on the insulation. There was a problem that the entire current transformer would be enlarged.

  In order to solve the above-described problems, a mold current transformer according to the present invention includes a conductor disposed in a ground tank in which an insulating gas is sealed, an iron core wound concentrically on the conductor, and the iron core. In a mold current transformer having a winding to be wound, and a solid insulator interposed between the conductor, the iron core, and the winding, the solid insulator includes at least the conductor, the iron core, and the winding. Covering the entire surface and forming both ends of the conductor to protrude outward, and the creeping surface from the triple point consisting of the conductor, the solid insulator and the insulating gas to the iron core is convex. It is formed.

  The conductor has at least a first diameter of a portion facing the iron core and a second diameter of both ends of the conductor, and the first diameter is smaller than the second diameter, The boundary between the first diameter and the second diameter is formed in a curved surface.

  More preferably, the corner of the iron core facing the conductor is formed in a step shape.

  By covering the entire iron core with the solid insulator, it is not necessary to consider the electric field of the triple point composed of the insulating gas, the solid insulator and the iron core among the two existing triple points. For this reason, the insulation distance from the triple point which became only one place, ie, the triple point which consists of a conductor, a solid insulator, and insulating gas, and an iron core can be reduced. Furthermore, the creeping surface of the solid insulator from the triple point consisting of the conductor, the solid insulator, and the insulating gas to the iron core is formed in a convex shape to ensure a sufficient creepage distance. The axial and radial dimensions of the flow device can be reduced.

  Also, in a solid insulator with higher insulation performance than in insulating gas, while ensuring insulation between the conductor and the iron core, the conductor diameter of the conductor facing the iron core is made smaller than the diameter of both ends of the conductor. Since the iron core is disposed close to the conductor side, the radial dimension of the current transformer can be reduced. In addition, by forming the boundary portion of the conductor generated by changing the conductor diameter into a curved surface and arranging the conductor inside the solid insulator, the insulation performance can be ensured and the size expansion can be prevented.

   Furthermore, by forming the corners of the iron core on the side facing the conductor in a stepped manner and increasing the radius of curvature of the coated portion of the core corners, the electric field between the conductor and the iron core is relaxed, and the radial dimension is expanded. Can be prevented. With such a configuration, the radial direction and the axial direction of the current transformer can be reduced, so that even when a gas having low insulation properties, for example, dry air, is used as an insulating medium, the size of the current transformer is increased. Can be suppressed.

Side sectional view of a current transformer according to the present invention Sectional view seen from the AA direction of FIG. 1 is an enlarged view of the main part of FIG. Side sectional view of a conventional current transformer

  Hereinafter, embodiments to which the present invention is applied will be described with reference to the accompanying drawings. As shown in FIGS. 1 and 2, the current transformer according to the present embodiment is roughly constituted by a conductor 1, a solid insulator 2, an iron core 3, and a winding 7. The conductor 1, the iron core 3, and the winding 7 wound around the iron core 3 are entirely covered with a solid insulator 2 made of epoxy resin or the like, and are integrally molded.

  As a method of molding a current transformer, first, a gantry made of the same member as the solid insulator 2 is created. Here, a thermosetting epoxy resin is used as the solid insulator 2. For the gantry, for example, a cylindrical member can be used. The iron core 3 and the winding 7 are fixed to the cylindrical member for positioning. Next, the positioned iron core 3 and the winding 7 are placed in a casting mold having a mold shape of the solid insulator 2 of the present embodiment described later. Thereafter, the solid insulator 2 is poured into a mold and heat treatment is performed, so that the injected solid insulator 2 and the cylindrical member made of the solid insulator 2 are integrated. By carrying out like this, the conductor 1, the iron core 3, and the coil | winding 7 whole can be coat | covered with the solid insulator 2, and it can mold integrally.

The current transformer in this invention is arrange | positioned in the earthing tank (not shown) in which the insulating gas 4 was sealed. For the insulating gas 4, for example, dry air, SF ₆ gas, or the like can be used. However, although SF ₆ gas has high insulation, there is a problem that the global warming potential is high and the environmental load is large. For this reason, in this embodiment, the insulation is as low as about 1/3 of SF ₆ gas, but dry air that can significantly reduce the environmental load is employed.

  As shown in FIG. 1, the conductor 1 has a different diameter depending on the location. In the portion of the conductor 1 that is disposed in the atmosphere of the insulating gas 4, that is, in the vicinity of both ends of the conductor 1, a diameter D <b> 1 is formed.

  Here, after the conductor 1 is molded by the solid insulator 2, it is disposed in the ground tank. The conductor 1 is made separately from other conductors (not shown) in the ground tank, and is connected to other conductors after the conductor 1 is stored in the ground tank. For this reason, the diameter D1 which secured the fixed dimension for fitting the bolt etc. which connect the conductor 1 and another conductor to the vicinity of the both ends of the conductor 1 is required.

  Furthermore, since both ends of the conductor 1 are in contact with the insulating gas 4, the electric field is stricter than the portion molded with the solid insulator 2. If the conductor diameter is too small, the electric field around the cylindrical conductor 1 becomes high, and there is a problem that insulation between the conductor 1 and the ground tank cannot be maintained. As described above, the diameter D1 in the vicinity of both ends of the conductor 1 needs to ensure a certain diameter from the viewpoint of workability and insulation performance.

  On the other hand, in the part which is the conductor 1 and was covered with the solid insulator 2, there is no work requirement like the both ends of the conductor 1 described above. Also, with respect to the insulation performance, it is not necessary to consider the insulation between the ground tanks as in the places where the insulating gas 4 is in contact. Furthermore, as will be described later with reference to FIG. 3, the solid insulator 2 has a convex shape so as to ensure a sufficient insulation distance between the triple point 10B and the iron core 3.

  Due to these factors, at the portion where the conductor 1 is covered with the solid insulator 2, the conductor diameter is formed to be D2 smaller than D1, and the iron core 3 can be disposed close to the conductor 1 direction. That is, the iron core is secured in a state where the insulation distance between the conductor 1 and the iron core 3 is ensured by reducing the conductor diameter and the insulation distance between the triple point 10B and the iron core 3 is secured by the creeping distance of the solid insulator 2. 3 can be disposed close to the conductor 1 direction.

  In the present embodiment, the diameter D2 is formed in at least a portion of the conductor 1 facing the iron core 3. By carrying out like this, the dimension of the diameter D3 of the current transformer of the part in which the conductor 1 was surrounded by the iron core 3 can be reduced.

  Further, the boundary portion 1A from the diameter D1 to the diameter D2 is formed in a smooth curved surface. In this way, electric field concentration is prevented from occurring at the boundary between two different diameters, and electric field relaxation in the solid insulator 2 is achieved.

Next, the shape of the solid insulator 2 will be described. As shown in FIGS. 1 and 2, the solid insulator 2 is formed so as to cover the conductor 1, the iron core 3, and the winding 7. Since the entire core 3 and the winding 7 are also covered, the electric field at the triple point composed of the insulating gas, the solid insulator, and the iron core is not considered among the two triple points that were weak points in the conventional insulation. It is a good configuration. Further, as described above, since the conductor 1 is connected to other conductors in the ground tank, both ends of the conductor 1 are formed so as to protrude from the solid insulator 2 to the outside.

  In FIG. 3, the axial dimension from the triple point 10 </ b> B composed of the conductor 1, the solid insulator 2, and the insulating gas 4 to the covering material 5 of the iron core 3 is assumed to be h. The axial dimension h is set to a length that can sufficiently secure insulation between the triple point 10 </ b> B and the iron core 3.

  Furthermore, the length on the creeping surface of the solid insulator 2 from the triple point 10B to the iron core 3 is defined as L1. In this embodiment, the triple point 10B is generated only at one location, but the insulation creepage distance between the triple point 10B and the iron core 3 is maintained by forming the solid insulator 2 in a convex shape and increasing the distance L1. However, the axial dimension h can be reduced.

  Next, the structure around the iron core 3 will be described with reference to FIG. 3. The iron core 3 is formed by laminating a plurality of silicon steel plates 3 a and is wound around the conductor 1 in a coaxial circle. A winding 7 is wound around the outer periphery of the iron core 3. Further, a conductive coating material 5 is provided on the outer periphery of the winding 7.

  Although not shown, a cushioning material is provided around the winding 7 to prevent damage due to contact between the winding 7 and the iron core 3, and to prevent the occurrence of uneven portions due to the winding 7, thereby concentrating the electric field. It plays a role to suppress.

  Similarly, a signal line (not shown) is connected to the winding 7. When a current flows through the conductor 1, the current induced in the winding 7 by the electromagnetic force of the conductor 1 is transmitted to the secondary circuit through this signal line.

  Further, in the present embodiment, the corner 3b on the side facing the conductor 1 of the iron core 3 where the electric field becomes severe is formed in a step shape. By doing so, the radius of curvature of the covering material 5 at the portion covering the core corner 3b can be increased, and the electric field between the conductor 1 and the iron core 3 can be relaxed.

  As described above, in the mold current transformer according to the present embodiment, the entire iron core 3 is covered with the solid insulator 2, so that the insulating gas and the solid insulator among the two existing triple points exist. There is no need to consider the electric field at the triple point consisting of the iron core. For this reason, the insulation distance from the triple point which became only one place, ie, the triple point 10B which consists of the conductor 1, the solid insulator 2, and the insulating gas 4, and the iron core 3 can be reduced. Furthermore, the creeping surface of the solid insulator 2 from the triple point 10B consisting of the conductor 1, the solid insulator 2 and the insulating gas 4 to the iron core 3 is formed in a convex shape, and the creeping distance is sufficiently secured. The axial dimension and the radial dimension of the current transformer can be reduced while maintaining

  Further, in the solid insulator 2 having a higher insulation performance than in the insulating gas 4, a portion of the conductor 1 facing the iron core 3 is secured while ensuring insulation between the conductor 1 and the iron core 3 and between the triple point 10 </ b> B and the iron core 3. The conductor diameter D2 is formed smaller than the diameter D1 at both ends of the conductor 1 and the iron core 3 is disposed close to the conductor 1 side. Therefore, the radial dimension of the current transformer can be reduced. In addition, by forming the boundary portion 1A of the conductor 1 generated by changing the conductor diameter into a curved surface and disposing it inside the solid insulator 2, it is possible to ensure insulation performance and prevent size expansion.

  Further, the corner 3b of the iron core 3 on the side facing the conductor 1 is formed in a stepped shape, and the radius of curvature of the covering material 5 at the portion covering the iron core corner 3b is increased so that the gap between the conductor 1 and the iron core 3 is increased. The electric field is alleviated and the dimensional expansion in the radial direction can be prevented. With such a configuration, the radial direction and the axial direction of the current transformer can be reduced, so that even when a gas having low insulation properties, for example, dry air, is used as an insulating medium, the size of the current transformer is increased. Can be suppressed.

In this embodiment, it is assumed that a low insulating gas such as dry air is used as the insulating medium in the ground tank. However, when a highly insulating gas such as SF ₆ is used, the gas is changed. It is obvious that further reduction in the size of the flow device can be achieved.

1 conductor 1A boundary
2 Solid Insulator 3 Iron Core 4 Insulating Gas 5 Covering Material 7 Winding 10B Triple Point

Claims (2)

A conductor disposed in a grounded tank in which an insulating gas is sealed, an iron core wound concentrically on the conductor, and a winding wound around the iron core;
In a mold current transformer in which a solid insulator is interposed between the conductor, the iron core, and the winding,
The solid insulator covers at least the conductor, the iron core, and the entire winding, and is formed so that both end portions of the conductor protrude to the outside.
Forming a creeping surface from the triple point consisting of the conductor, the solid insulator and the insulating gas to the iron core ,
The conductor has at least a first diameter of a portion facing the iron core and a second diameter of both ends of the conductor;
The first diameter is smaller than the second diameter,
Further , the mold current transformer is characterized in that the boundary between the first diameter and the second diameter is formed in a curved surface shape . The mold current transformer according to claim 1 , wherein a corner of the iron core facing the conductor is formed in a step shape.

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