JP2018160576A - Transformer gas bushing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas bushing for a transformer that is excellent in earthquake resistance and productivity, does not cause carbonization even when electric discharge occurs along an oil middle portion, does not concentrate an electric field on a cement layer, and can be attached to an existing transformer pocket.SOLUTION: There is provided a gas bushing for a transformer with a porcelain tube on the air side as a polymer porcelain tube 11 and a porcelain tube on the oil side as a porcelain pipe 12. The upper end of the porcelain tube 12 is fixed to a flange 21 by a cement layer 20, but the flange 21 is positioned above a transformer pocket 10. The cement layer 20 is protected by a conductive layer or a ground shield 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an improvement of a gas bushing for a transformer that is attached to a transformer pocket to draw a power line inside the transformer.

  As a gas bushing for a transformer, a structure in which both an air side insulating pipe and an oil inside insulating pipe are made of porcelain and a capacitor immersed in insulating oil is enclosed has been used for a long time. However, this structure is heavy, and there is a possibility that oil leaks or porcelain breaks down in the event of an earthquake, and it can contribute to improving the seismic strength of the transformer.

  Therefore, as shown in Patent Document 1, a transformer gas bushing has been developed in which the air portion is a polymer insulator tube, the oil portion is an epoxy resin insulating spacer, and an insulating gas is sealed inside. The transformer gas bushing is fixed to the transformer pocket via a support fitting disposed between the polymer insulation pipe and the epoxy resin insulating spacer. The gas bushing for transformers shown in Patent Document 1 is light and excellent in earthquake resistance, but has the following problems.

  First, the epoxy resin insulation spacer used in the oil is produced by casting using a mold. However, there are void defects, foreign matter, cracks, electrodes and fixing screw bosses inside the resin. It is necessary to perform strict production management so that peeling does not occur. This is because if there is such an internal defect, a partial discharge occurs, and a ground fault may occur with the progress of the discharge part. For this reason, many quality checks, such as an X-ray inspection, an internal pressure inspection, and a partial discharge inspection, are required, and productivity is deteriorated.

  Secondly, the epoxy resin insulating spacer is 275 kV, has a maximum diameter of about 400 mm and a maximum length of about 1000 mm, and is processed with high accuracy to ensure dimensional accuracy and surface roughness after molding. An expensive mold that can be divided is required. Therefore, a lot of material cost and processing cost are required for manufacturing the mold.

  Thirdly, considering the first production management with the minimum mold investment for the second reason, it takes 1-2 weeks to complete one epoxy resin insulating spacer, and the transformer for three-phase AC Many delivery times are required to meet the six demands required for primary and secondary.

  Fourth, since an epoxy resin, which is an organic insulating material, is used in the oil, it is easy for the oil-filled pipe to carbonize if a discharge occurs along the oil and the resin. Since it becomes tangled, it is necessary to replace the entire bushing to recover from a power failure.

  In order to solve the above-mentioned problems, the present inventor has considered replacing the oil middle portion of the transformer gas bushing with a porcelain insulator tube. However, unlike an epoxy resin insulating spacer, the top of a porcelain insulator tube must be fixed to a support fitting with a flange and cement, and the flange portion becomes larger in the diameter direction. However, because the upper diameter of the transformer pocket is standardized by JEC (Electrical Society Electrical Standards Research Committee Standard), etc., the transformer gas bushing with the oil inside enlarged in the diameter direction is not compatible with the existing bushing. There is a problem.

  Further, the upper end portion of the porcelain insulator tube must be fixed to the support fitting by a flange, and the flange faces the center conductor to which a high voltage is applied as a ground electrode. For this reason, an electric field concentrates in the space | gap of the cement layer which has fixed the porcelain insulator pipe to the flange, and causes corona discharge. Therefore, in order to prevent this, it is necessary to arrange a ground shield inside the flange. Since a predetermined insulation distance determined by the gas type and gas pressure is required between the ground electrode and the central conductor, this also increases the size of the oil-filled pipe and its flange portion in the diameter direction.

  For reference, FIG. 5 shows a state where the middle part of the oil is simply replaced with a porcelain insulator tube. Reference numeral 1 is a transformer pocket, 2 is a support fitting for supporting a polymer insulator tube in the air, 3 is a porcelain insulator tube in the oil, 4 is a flange supporting its upper end, 5 is a cement layer, and 6 is a ground shield. As described above, the flange portion becomes larger in the diameter direction as it is, and specifically, at 275 kV, the diameter of this portion exceeds 500 mm. However, since the standardized transformer pocket has a diameter of 440 mm at 275 kV, compatibility with the existing bushing is lost.

Japanese Patent No. 5766372

  Accordingly, the object of the present invention is to solve the above-mentioned conventional problems, and is excellent in earthquake resistance and productivity, and there is no possibility of carbonization of the oil-filled pipe creeping surface even when a discharge occurs in the oil-filled surface of the oil-filled pipe. It is to provide a gas bushing for a transformer that is compatible with the bushing.

  The gas bushing for a transformer of the present invention, which has been made to solve the above problems, connects an air side insulator pipe and an oil side insulator pipe with a support fitting, penetrates the central conductor inside, and insulates the gas. A gas bushing for a transformer in which a gas insulator on the air side is a polymer insulator, a gas insulator on the oil side is a porcelain insulator, and the upper end of the porcelain insulator is placed above the transformer pocket. It is characterized by being fixed by a flange located at the position.

  In addition, it can be set as the structure which provided the grounding shield of the same electric potential as a flange over the predetermined length from the upper end of a flange inside the upper part of a porcelain insulator tube. Moreover, it can be set as the structure which formed the electrically conductive layer of the same electric potential as a flange over the predetermined length from the upper end of a flange on the inner surface of the upper part of a porcelain insulator pipe. The conductive layer may be a conductive film, a metal vapor deposition film, or a conductive paint.

  In the gas bushing for a transformer of the present invention, a gas insulator tube in the air side is a polymer insulator tube, and a gas insulator tube in the oil side is a porcelain insulator tube. Porcelain insulator tubes can be easily and inexpensively produced by existing manufacturing techniques, and there is no risk of carbonization when a discharge occurs along the surface of the oil. Moreover, by adopting a new structure in which the upper end of the porcelain insulator tube is fixed by a flange located above the transformer pocket, it can be attached to an existing transformer pocket even if the outer diameter of the flange portion increases. .

It is sectional drawing which shows the whole gas bushing for transformers of this invention. It is a principal part expanded sectional view of 1st Embodiment. It is a principal part expanded sectional view of 2nd Embodiment. It is a principal part expanded sectional view which shows the modification of 2nd Embodiment. It is an expanded sectional view of the principal part which shows the state which replaced the oil center part with the porcelain insulator tube.

Embodiments of the present invention will be described below.
FIG. 1 is a cross-sectional view showing an entire transformer gas bushing according to the first embodiment, and FIG. 2 is an enlarged cross-sectional view of the main part thereof.

  In these figures, reference numeral 10 denotes a transformer pocket for mounting a bushing, and the inside thereof is filled with insulating oil. Reference numeral 11 denotes a polymer insulator pipe which is an air side insulator pipe, and reference numeral 12 denotes a porcelain insulator pipe which is an oil inside insulator pipe. The porcelain insulator tube 12 has been used for many years as an insulator tube for a gas bushing for a transformer, and can be mass-produced at low cost since the manufacturing technology has been established.

  The lower end portion of the polymer insulation tube 11 is fixed to the upper flange 14 of the cylindrical support fitting 13. An air-side ground electrode 15 is provided on the inner periphery of the lower end portion of the polymer insulation tube 11 for relaxing the electric field along the air surface. The upper end portion of the polymer insulation tube 11 is sealed with a metal upper lid 16, and an air terminal 17 is firmly fixed to the upper side of the upper lid 16 by welding or the like. The upper end of the center conductor 18 is fixed to the lower surface of the upper lid 16. Reference numeral 19 denotes an air shield ring.

  As shown in FIG. 2, the upper end portion of the porcelain insulator tube 12 is fixed to the inner surface of the flange 21 by the cement layer 20. Conventionally, as shown in FIG. 5, the flange 4 that supports the porcelain insulator tube is provided inside the transformer pocket 1, but in the present invention, the flange 21 is located above the transformer pocket 10. .

  In the present embodiment, a ground shield 22 having the same potential as the flange 21 is provided on the inner side of the upper portion of the porcelain insulator tube 12 from the upper end of the flange 21 to a predetermined length. Thus, even if the ground shield 22 is provided inside the upper part of the porcelain insulator tube 12, since the flange 21 is positioned above the transformer pocket 10, it is necessary to increase the outer diameter of the attachment portion to the transformer pocket 10. It can be attached to the existing transformer pocket 10.

  The preferred length from the upper end of the flange of the ground shield 22 varies depending on the voltage class, for example, 320 mm for 34.5 to 115 kV, 420 mm for 161 kV to 287.5 kV, and 700 mm for 550 kV. It is desirable that the porcelain insulator tube 12 has the same insulator tube diameter from the upper end to the center, and the ground shield 22 extends to that portion.

  The lower flange 23 of the support fitting 13 is fixed to the upper surface of the flange 21 by a bolt 25 via an insulating flange 24. Thus, the polymer insulator tube 11 and the porcelain insulator tube 12 are integrated by the support fitting 13 and the flange 21, and the inside thereof is filled with the insulating gas. The lower surface of the flange 21 is bolted to the transformer pocket 10. As shown in FIG. 1, the lower end of the center conductor 18 is connected to the lowermost metal fitting 26 at the lower end of the porcelain insulator tube 12, and further connected to a lead wire (not shown) extending from the transformer.

  The gas bushing for a transformer configured in this way is excellent in earthquake resistance because the air-side insulator tube is a light polymer insulator tube 11. Further, since the insulating pipe in the oil side is the porcelain insulating pipe 12, it can be produced easily and inexpensively, and there is no possibility that the creeping surface of the oil-in-gassing pipe is carbonized even when a discharge occurs in the creeping area in the oil. Furthermore, since the upper end of the porcelain insulator tube 12 is extended above the transformer pocket 10 and supported by the flange 21 on the upper side of the transformer pocket 10, even if the outer diameter of the flange 21 increases, the existing transformer pocket 10 Can be attached to.

  Further, since the cement layer 20 that fixes the porcelain insulator tube 12 to the flange 21 is protected by the ground shield 22 disposed between the center conductor 18 to which a high voltage is applied, a high voltage is applied to the center conductor 8. Even if it is done, the electric field does not concentrate on the cement layer 20.

  Next, a second embodiment of the present invention will be described. In the first embodiment described above, the electric field concentration of the cement layer 20 is protected by the ground shield 22, but in the second embodiment, the same potential as the flange 21 is provided at the upper end portion of the porcelain insulator tube 12, as shown in FIG. That is, the conductive layer 30 having the ground potential was formed. The conductive layer 30 can be formed by a conductive rod. In FIG. 3, the conductive layer 30 is formed on the outer peripheral surface of the porcelain insulator tube 12, but may be formed on the inner peripheral surface across the upper end surface.

  This conductive layer 30 is also formed on the inner surface of the upper part of the porcelain insulator tube 12 from the upper end of the flange 21 over a predetermined length. The preferred length is 320 mm for 34.5 to 115 kV, 420 mm for 161 kV to 287.5 kV, and 700 mm for 550 kV, as described above.

  A spring grounding metal fitting 31 provided at the lower end of the flange 21 is in contact with the conductive layer 30 so that the conductive layer 30 has the same potential as the flange 21, that is, a ground potential. For this reason, even if the ground shield 22 as in the first embodiment is omitted, the cement layer 20 can be protected.

  As shown in FIG. 3, the conductive layer 30 on the outer peripheral surface of the porcelain insulator tube 12 has an R shape whose lower end reaches the first rib 27 of the porcelain insulator tube 2, and the tip is away from the center conductor 18 so that the discharge does not easily occur. It has become. Further, as shown in FIG. 4, if a shield ring 28 made of a coil spring is provided on the first rib 27 of the porcelain insulator tube 2, discharge can be prevented more reliably.

  As is well known, a conductive soot is obtained by dispersing a metal oxide imparting semiconductivity in a glaze. However, as the conductive layer 30, a metal vapor deposition layer such as aluminum or a conductive paint can be used in addition to the conductive rod.

  The transformer gas bushing of the second embodiment configured in this way is also excellent in earthquake resistance because the air side insulator tube is made of a lightweight polymer insulator tube 11. Further, since the insulating pipe in the oil side is the porcelain insulating pipe 12, it can be produced easily and inexpensively, and there is no possibility that the creeping surface of the oil-in-gassing pipe is carbonized even when a discharge occurs in the creeping area in the oil. Further, since a conductive layer 30 having the same potential as the flange 21 is formed between the cement layer 20 that connects the porcelain insulator tube 12 to the flange 21 and the center conductor 18, a high voltage is applied to the center conductor 18. Even if it is done, the electric field does not concentrate on the cement layer 20.

  Moreover, since the conductive layer 30 is formed on the surface of the porcelain insulator tube 12, the outer diameter of the attachment portion of the porcelain insulator tube 12 to the pressure pocket 10 is smaller than that of the first embodiment in which the ground shield 22 is provided. can do. Therefore, it can be set as the gas bushing for transformers which can be attached to the existing transformer pocket.

  In any of the embodiments, an insulating flange 24 is interposed between the support fitting 13 and the flange 21 at the lower end of the polymer insulation tube 11. The support fitting 13 and the flange 21 are connected by a conductive plate 29, and the support fitting 13 is always at ground potential. However, when the conductive plate 29 is removed, the support fitting 13 and the ground shield are separated from the ground, so that the soundness of the device can be confirmed by measuring the bushing and the partial discharge in the transformer.

  As described above, the transformer gas bushing of the present invention is excellent in earthquake resistance and productivity, and there is no fear of carbonization even when electric discharge occurs in the surface of the oil center, and the electric field concentrates on the cement layer. In addition, it can be attached to an existing transformer pocket and has an advantage of excellent compatibility.

DESCRIPTION OF SYMBOLS 1 Transformer pocket 2 Polymer insulator tube 3 Porcelain insulator tube 4 Flange 5 Cement layer 6 Ground shield 10 Transformer pocket 11 Polymer insulator tube 12 Porcelain insulator tube 13 Support metal fitting 14 Upper flange 15 Air side ground electrode 16 Upper lid 17 Air Terminal 18 Central conductor 19 Shield ring 20 Cement layer 21 Flange 22 Ground shield 23 Lower flange 24 Insulating packing 25 Bolt 26 Bottom bracket 27 First rib 28 Shield ring 29 Conductive plate 30 Conductive layer 31 Spring ground bracket

Claims (4)

A gas bushing for a transformer in which a gas pipe on the air side and a gas pipe on the oil side are connected by a support fitting, and the central conductor is penetrated inside and an insulating gas is sealed.
The air side irrigation tube is a polymer irrigation tube, the oil side irrigation tube is a porcelain irrigation tube,
A gas bushing for a transformer, characterized in that the upper end of the porcelain insulator tube is fixed by a flange located above the transformer pocket.   2. The gas bushing for a transformer according to claim 1, wherein a ground shield having the same potential as that of the flange is provided on the inner side of the upper part of the porcelain insulator tube over a predetermined length from the upper end of the flange.   2. The gas bushing for a transformer according to claim 1, wherein a conductive layer having the same potential as that of the flange is formed on the inner surface of the upper part of the porcelain insulator tube over a predetermined length from the upper end of the flange.   4. The transformer gas bushing according to claim 3, wherein the conductive layer is a conductive film, a metal vapor-deposited film, or a conductive paint.

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