JPH09190934A - Dc transmission transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the transformer, which decreases the electric-field value of the DC voltage applied in the direction of the layer along the insulating material comprising oil impregnated paper at the boundary part of an insulating spacer and an electric-field alleviating shield ring, or the boundary part of the edge part of a DC winding and the insulating spacer and or at the above described both boundary parts. SOLUTION: A DC voltage bearing cylindrical insulating plate 18 comprising oil impregnated paper is provided at the inner-diameter side and the outer- diameter side in contact with the region from the paper side of the overlapped part of the lower edge of an insulation-reinforcing cylindrical insulator 17 of a DC winding 5 and the upper surface of an insulating spacer 15 to the lower side of an oil gap formed between the lower surface of the insulating spacer 15 and the upper corner part of an electric-field alleviating shield ring 10. Here, the DC voltage, which is applied on the above described overlapped part and the oil gap is borne with the layer penetrating direction A of the insulating plate 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC transmission transformer, and more particularly to a DC transmission AC / DC conversion transformer to which a voltage waveform including a DC component is added during operation.

[0002]

2. Description of the Related Art As shown in FIG. 2, a transformer for AC / DC conversion used for DC power transmission has a tank 2 filled with insulating oil 1.
It is constituted by accommodating therein a transformer main body composed of an iron core 3 and a winding wire 4 wound around its leg portion in a cylindrical shape, and the winding wire 4 is sufficiently coaxial with each other. It is composed of a DC winding 5 and an AC winding 6 arranged with an insulation distance maintained, and an insulating tube 7 made of insulating paper arranged between these windings 5 and 6 for improving the insulation performance. There is.

FIGS. 3 and 4 show examples of the insulating structure of such a transformer for AC / DC conversion.

The DC winding 5 is composed of a plurality of disk-shaped unit windings 9 formed by winding a wire 8 formed by covering a conductor 8a with an insulator 8b made of oil-impregnated paper in a disk shape a plurality of times. It is constructed by vertically stacking via a spacer (not shown), and a lower end thereof is formed by covering a conductor 10a having a large radius of curvature with an insulator 10b made of oil-impregnated paper along a molded insulator 10c. Insulator made of oil-immersed paper 10
d. Shield ring for electric field relaxation integrally coated with d
Is arranged. The AC winding 6 is also configured in the same manner as the DC winding 5, and an electric field alleviating shield ring 11 in which the periphery of a conductor 11 a having a large radius of curvature is covered with an insulator 11 b made of oil-impregnated paper is similarly arranged at the lower end. Have been. Also,
Around the DC winding 5 and the shield ring 10 and the AC winding 6 and the shield ring 11, an I-shaped insulating cylinder 12, an L-shaped insulating cylinder 13 and an inverted L-shaped cross-section made of oil-impregnated paper, respectively. The insulating tube 14 is arranged to form an insulating structure.

As shown in FIG. 5, a plurality of radially extending spacers 15 are provided between the DC winding 5 and the shield ring 10 to form a cooling passage and maintain mechanical strength. And a cylindrical insulator for insulation reinforcement made of oil-impregnated paper (a plurality of arc-shaped pieces are inserted along the inner and outer sides of the DC winding 5 in the circumferential direction). 16 and 17).
Is provided.

3 and 4 have the same structure except that the arrangement of the DC winding 5 and the AC winding 6 is opposite to each other in the radial direction.

By the way, the DC winding 5 of the AC / DC conversion transformer
And the DC potential distribution under DC high voltage applied to the shield ring 10 is governed by the resistivity of the constituent insulators, but the resistivity of the oil-immersed paper depends on the resistivity of the transformer oil, which is the main insulating oil. At 80 ° C., it is as large as 10 to 50 times, so that the voltage sharing in these parts largely depends on the insulator made of oil immersion paper. As a result, a high electric field is generated inside the insulator made of oil immersion paper. Become.

Therefore, conventionally, for example, JP-A-60-200
As disclosed in Japanese Unexamined Patent Publication No. 509 and Japanese Unexamined Patent Publication (Kokai) No. 62-2509, in order to improve the dielectric strength at the end of the DC winding, the insulation covering the wires located at the innermost and outermost layers is removed. As a result, improvement measures have been taken to reduce the voltage distribution in this portion and suppress the generation of a high electric field.

[0009]

However, in recent years,
The resistivity of the insulator made of oil-impregnated paper that shares most of the DC voltage has directionality, and among them, the breakdown electric field value in the layered direction of oil-impregnated paper was found to be comparable to that of transformer oil. A need has arisen to reduce the electric field value in the layered direction of the paper immersion.

[0010] Further, in the future, as the need for increasing the voltage of DC power transmission increases, it is necessary to improve the dielectric strength of the DC insulation structure, but the above-described improvement in consideration of the directionality of the oil immersion paper has not been made. .

Furthermore, as described above, the degree of voltage sharing in DC insulation is governed by the resistivity of the elements constituting the insulation structure. Therefore, if the generated voltage increases, it is necessary to maintain the same electric field value. In addition, the insulation distance increases according to the ratio, which leads to an increase in the size of the equipment. Therefore, in order to reduce the insulation distance, it is necessary to suppress the electric field value at a site where a high electric field is locally generated.

In the portions surrounded by alternate long and short dash lines D ₁ and D ₂ in FIG. 5, cylindrical insulators 16 and 17 for insulation reinforcement of the DC winding 5 and a coating insulator 1 of the shield ring 10 are provided.
0d and a spacer 15 interposed therebetween.
The insulating oil 1 enters, and wedge-shaped oil gaps are formed. In these wedge-shaped gaps, the resistivity of the insulating oil is low. Most will be shared.

[0013] an enlarged D ₂ parts of FIG. 5 is shown in FIG. A portion surrounded by the one-dot chain line B ₁ in FIG. 6, that is, like a wedge-shaped oil gap between the spacer 15 made of oil-impregnated paper and the coated insulator 10d made of oil-impregnated paper of the shield ring 10, its vicinity is formed. In the case where the lines of electric force cross a combination portion of the insulators in which the layer directions C are radial directions to each other, or the portion surrounded by the one-dot chain line B ₂ , that is, the cylindrical insulator 17 made of oil-impregnated paper.
When a line of electric force crosses a combined portion of insulators whose vertical directions C are different from each other, such as a wedge-shaped oil gap between the spacer 15 and the spacer 15 made of oil-immersed paper,
An electric field tends to concentrate on these combination parts, and a high voltage is generated particularly in a layer direction of an insulator made of oil immersion paper.

[0014] As described above, since the breakdown electric field value of the insulator made of oil-immersed paper has anisotropy, DC withstand field value at that edgewise is almost equivalent to the insulating oil, the B _1, edgewise of the insulator in the B ₂ moiety, i.e. the radial direction of the insulating tolerance becomes very low, the weaknesses insulation. Incidentally, such a problem occurs also in D ₁ part.

FIG. 7 shows an example of DC electric field analysis mapping at this time. In this figure, as shown by an arrow F, a DC electric field is generated in a direction perpendicular to the equipotential line E of the DC voltage, and the DC electric field F is a spacer 1 made of oil-impregnated paper.
5 and the covering insulating material 10d,
It can be seen that a high voltage is generated in this direction.

It is considered that such a concentration of the electric field in the wedge-shaped oil gap with a rise in the voltage of the DC power transmission causes a dielectric breakdown.

Therefore, an object of the present invention is to provide an oil immersion at the boundary between the spacer and the shield ring for reducing electric field, or at the boundary between the end of the DC winding and the spacer, or at both boundaries. An object of the present invention is to provide a DC power transmission transformer capable of reducing an electric field value of a DC voltage applied in a layer direction of an insulator made of paper and improving the insulation strength.

[0018]

The breakdown electric field value of an insulator made of oil-impregnated paper is almost the same as that of the insulating oil in the direction along the layer. One or more digits higher than the breakdown electric field value.

The present invention has been made in view of this point, and the boundary between the spacer and the shield ring for alleviating the electric field, or the boundary between the end of the DC winding and the spacer, or Along the inner diameter side and the outer diameter side of the region extending over the two boundaries, a DC voltage sharing insulator made of oil-impregnated paper whose permeation direction is the radial direction is provided, and the region extending over these boundaries and the two boundaries is provided. The DC voltage applied to the DC voltage is distributed in the direction of the penetrating layer of the DC voltage sharing insulator.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.
Will be described.

The spacer 15 has its inner and outer peripheral portions removed, and its inner and outer peripheral surfaces are the inner peripheral surface of the cylindrical insulator 16, the outer peripheral surface of the cylindrical insulator 17, and the shield ring 10 for reducing the electric field. Are formed substantially flush with the inner and outer peripheral surfaces of the spacer, and from above the overlapping portion between the lower end surface of the cylindrical insulator 17 and the upper surface of the spacer 15, from above the lower surface of the spacer 15 and the upper outer diameter side corner of the electric field mitigation shield ring 10. A DC voltage sharing insulating plate 18 is provided below and in contact with the oil gaps formed between them. The DC voltage sharing insulating plate 18 is made of oil-impregnated paper, and is formed by bending an insulating plate having a radial direction of the permeation layer direction A sequentially in the circumferential direction so as to have a cylindrical shape. Are formed at the positions corresponding to the radial direction, so that the flow of the insulating oil 1 to the cooling passage is not hindered. Other configurations are the same as those of the above-described conventional example.

In FIG. 1, only the lower end portion of the DC winding and the outer diameter side portion of the lower electric field reducing shield ring are shown. Similarly, a DC voltage sharing insulating plate is provided on the inner and outer diameter sides of the electric field relaxing shield ring.

According to this embodiment, the overlapping portion between the lower end surface of the cylindrical insulator 17 and the upper surface of the spacer 15 or the spacer 1
The DC voltage applied to the oil gap formed between the lower surface of the filter 5 and the shield ring 10 for reducing electric field is converted into a DC voltage sharing insulation made of oil-impregnated paper provided along the inner and outer diameter sides of these portions. Since the plate 18 is shared in the direction of the transmissive layer having high resistivity, most of the DC voltage applied to these portions is shared by the DC voltage sharing insulating plate 18, and as a result, the insulating structure of these portions is reduced. The electric field value generated in the layer direction along the spacer 15 made of the oil-impregnated paper and the insulating insulator 10d of the shield ring 10 for reducing the electric field can be suppressed low, and the dielectric strength can be improved.

FIG. 8 shows an example of DC electric field analysis mapping according to this embodiment. 8, G is an equipotential line, arrow H
Indicates the direction in which the DC electric field is generated.

FIG. 8 is compared with FIG. 7 which shows an example of a DC electric field analysis map of the conventional example in which the DC voltage sharing insulating plate 18 is not provided. It can be seen that the provision of 18 significantly reduces the size before the provision. That is, by providing the DC voltage sharing insulating plate 18, the DC voltage sharing in these portions can be controlled, and the electric field value in the layer direction generated in these portions can be suppressed.

In the above-described embodiment, the DC voltage sharing insulating plate 18 is used for both the overlapping portion of the cylindrical insulator 17 and the spacer 15 and the oil gap formed between the spacer 15 and the shield ring 10 for reducing the electric field. Although provided over the portion, the invention is not limited to this, and it is also possible to provide over only the overlapping portion or the oil gap of these portions, or to separately provide over the overlapping portion and the oil gap of these portions.

Further, the DC voltage sharing insulating plate 18 is formed in a cylindrical shape and is provided in common at each circumferential position where the spacer 15 is arranged. A plurality of arc-shaped plates and these are spacers 1
5 may be provided separately corresponding to each position in the circumferential direction where the 5 is arranged.

[0028]

According to the present invention described above, focusing on the anisotropy of the breakdown electric field value in the insulator made of oil-impregnated paper, the boundary portion between the spacer and the electric field relaxation shield ring,
Alternatively, a direct current made of oil-impregnated paper whose permeation direction is radial along an inner diameter side and an outer diameter side of an end portion of the DC winding and a boundary portion of the spacer or a region extending between the two boundary portions. A voltage sharing insulator is provided, and the DC voltage applied to these boundaries and the region extending between both boundaries is shared in the direction of the transmissive layer of the DC voltage sharing insulator having a high resistivity. Most of the applied DC voltage will be shared by this DC voltage sharing insulator,
As a result, the electric field value in the layer direction in the spacer or the covering insulator made of oil-impregnated paper constituting the insulating structure of these portions is reduced, and the dielectric strength can be improved.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part of an AC / DC conversion transformer according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view showing the entire structure of the AC / DC conversion transformer.

FIG. 3 is a sectional view showing an example of a conventional AC / DC conversion required transformer.

FIG. 4 is a cross-sectional view showing another example of the conventional AC / DC conversion transformer.

5 is an enlarged sectional view showing the vicinity of the lower end of the DC winding of the transformer for AC / DC conversion shown in FIG. 3 or FIG. 4;

6 is an enlarged sectional view showing the vicinity of D ₂ parts of FIG.

7 is an explanatory diagram showing a DC electric field analysis mapping example in the vicinity of D ₂ portion shown in FIG.

8 is an explanatory diagram showing a DC electric field analysis mapping example in the vicinity of the portion corresponding to D ₂ parts of AC-DC converter transformer shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating oil 2 Tank 3 Iron core 5 DC winding 6 AC winding 8 Element wire 8a Element conductor 8b Element insulator 9 Disc-shaped unit winding 10 Electric field relaxation shield ring 10a Shield ring conductor 10d Shield ring oil immersion Insulating insulator made of paper 12, 13, 14 Insulating cylinder 15 Insulating spacer made of oil-impregnated paper 16, 17 Insulating reinforcing cylindrical insulator 18 DC voltage sharing insulating plate

Front Page Continuation (72) Inventor Shin Kadowaki 1-1-1 Kokubuncho, Hitachi City, Ibaraki Hitachi Ltd. Kokubun Plant (72) Inventor Toshimitsu Obata 1-1-1 Kokubuncho, Hitachi City, Ibaraki (72) Inventor, Hiroaki Kojima, 7-2-1, Omika-cho, Hitachi-shi, Ibaraki, Hitachi, Ltd. Electricity and Electric Power Development Division, Hitachi, Ltd. (72) Kazuo Sekine, Kokubun-cho, Hitachi-shi, Ibaraki 1-1-1, Hitachi Kokubun Plant, Ltd. (72) Inventor Makoto Tanaka 3-3-22 Nakanoshima, Kita-ku, Osaka-shi, Osaka Kansai Electric Power Co., Inc. (72) Inventor Hiroshi Sugihara 2 Marunouchi, Takamatsu-shi, Kagawa Prefecture No. 5 Shikoku Electric Power Co., Inc. (72) Inventor Yoshinori Makino 6-15-1, Ginza, Chuo-ku, Tokyo Power source development Co., Ltd.

Claims (3)

[Claims] 1. A transformer filled with an iron core and a DC winding and an AC winding wound around the iron core is accommodated in a tank filled with insulating oil, and a spacer is provided at an end of the DC winding. Shield ring for electric field mitigation
The DC winding is insulated by an insulator made of insulating paper wound therearound, and the spacer is made of an insulator made of insulating paper having a radial direction along its layer direction,
In the DC transmission transformer, the shield ring for electric field relaxation is composed of a conductor and an insulator made of insulating paper wound around the conductor, the inner diameter and outer diameter between the spacer and the shield ring for electric field relaxation. Along the side, a DC voltage sharing insulator made of oil-impregnated paper whose permeation direction is a radial direction is provided, and the DC voltage applied to the boundary between the spacer and the electric field mitigation shield ring is used for the DC voltage sharing. A transformer for DC power transmission, wherein the transformer is shared in the direction of the penetrating layer of the insulator. 2. A transformer main body comprising an iron core and a DC winding and an AC winding wound around the iron core is housed in a tank filled with insulating oil, and a spacer is provided at an end of the DC winding. While arranging the shield ring for electric field relaxation via
The DC winding is insulated by an insulator made of insulating paper wound therearound, and the spacer is made of an insulator made of insulating paper having a radial direction along its layer direction,
In the DC power transmission transformer, the shield ring for electric field relaxation is formed of an insulator made of a conductor and insulating paper wound around the conductor, an inner diameter side between the end of the DC winding and the spacer and an outer side. Along the radial side, a DC voltage sharing insulator made of oil-impregnated paper whose permeation direction is the radial direction is provided,
A DC transmission transformer, wherein a DC voltage applied to an end portion of the DC winding and a boundary portion of the spacer is shared in a penetrating direction of the DC voltage sharing insulator. 3. A transformer filled with an iron core and a DC winding and an AC winding wound around the iron core is accommodated in a tank filled with insulating oil, and a spacer is provided at an end of the DC winding. Shield ring for electric field mitigation
The DC winding is insulated by an insulator made of insulating paper wound therearound, and the spacer is made of an insulator made of insulating paper having a radial direction along its layer direction,
The shield ring for electric field relaxation is a transformer for DC power transmission composed of an insulator made of a conductor and insulating paper wound around the conductor, wherein the shield ring for electric field relaxation is provided from the end of the DC winding via the spacer. Along the inner diameter side and the outer diameter side of the region extending over the shield ring, a DC voltage sharing insulator made of oil-impregnated paper whose permeation direction is the radial direction is provided,
A DC transmission transformer, wherein a DC voltage applied to the region is shared in a direction in which the DC voltage sharing insulator penetrates.