JP2000260636A - Stationary induction apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable realization of an excellent insulating performance and reduced insulation dimensions by eliminating drawbacks in an insulating structure. SOLUTION: Insulating layers 6 surrounding coil groups 21 and 31 and electrodes 8 surrounding the layers for voltage control are provided. The electrodes 8 and insulating layers 6 are arranged so that an electric field is directed in a direction of the weak insulation strength of the insulating layers 6, i.e., the field is vertical to its creeping direction. As a result, the field in the creeping direction of the insulating layers to an impulse voltage or a normal test voltage can be suppressed and thus the good part of dielectric strength of the insulating layers can be effectively used. For this reason, an improved insulation performance and a reduced insulation distance can be effectively realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stationary induction device such as a transformer or a reactor, and more particularly to an insulation structure thereof.

[0002]

2. Description of the Related Art A transformer is a static induction machine having one or more windings. Transformers are widely used in power systems for transmitting power, and convert current and voltage values by electromagnetic induction between circuits of the same frequency. Reactors also have one or more windings and are used to add inductance to electrical circuits and power systems. Generally, there are oil cooling, gas cooling, liquid cooling, and air cooling as internal cooling systems, and air cooling, water cooling, and the like as external cooling systems for cooling internal refrigerant. Further, there are an iron core type in which silicon steel sheets are laminated as a magnetic circuit and an air core type having no iron core. The present invention is directed to such devices.

In each of the above cases, each part of the conductor constituting the winding has a different voltage. In order to electrically insulate the conductors from each other, a method using oil containing insulating oil and fibrous insulating material, sulfur hexafluoride (SF6) gas, resin molding, and the like are used. In these insulating transformers, the electric field is concentrated on the insulating oil or gas because the insulating oil or gas has a lower dielectric constant than the solid dielectric constant. Insulating oil and gas have a lower dielectric strength than solid insulators. Therefore, in these transformers, the oil, gas, and air portions are divided by a solid insulator to reduce the distance between the portions, thereby improving the overall insulation performance.

For example, as described in “Electrical Engineering Handbook”, The Institute of Electrical Engineers of Japan, pp. 674 of 1988, conventional oil-immersed transformers have a high voltage winding, a low voltage winding, an iron core, and a tank. Is divided by an insulating partition wall made of interlayer insulating paper. It is known that the insulation performance of the oil layer per unit distance is improved by reducing the distance. Therefore, the distance between the divided oil layers is reduced to improve the dielectric strength, and the insulation performance between the windings is improved in addition to the effect that the insulating partition walls prevent the progress of the discharge phenomenon that causes the dielectric breakdown. Similarly, in gas-insulated equipment, the insulation breakdown electric field can be increased by reducing the insulation distance of the gas portion, as is known as Paschen's law.

Japanese Patent Application Laid-Open No. 4-306810 discloses a small gap formed between a conductor and a supporting insulator or a triple contact portion in order to reduce the insulation distance of a core-type transformer and reduce the size of equipment. Attempts are made to suppress the electric field concentration by interposing an insulator having a lower relative permittivity than one of the insulators at a portion where the electric field is concentrated such as a junction. In Japanese Patent Application Laid-Open No. Sho 62-144307, a shield ring is provided with a conductive shield and two or more low dielectric constant insulators having different dielectric constants in order to improve the dielectric strength at the winding end of the core type transformer. The low dielectric constant insulating material is stacked from the conductive shield in ascending order of the dielectric constant, and is collectively covered to suppress the electric field concentration near the shield ring. In these methods, electric field concentration can be suppressed by placing an insulating material with a higher dielectric constant in a low dielectric constant portion such as oil or gas, but equipotential lines cross the creepage of the insulator, and Due to the problem of the generation of an electric field, there is a limit to further downsizing the device.

Electrical stresses applied to the insulation of transformers and reactors include normal voltages, surge voltages such as lightning surge voltages due to lightning strikes and switching surges generated by circuit breakers and disconnectors. The distribution of the potential applied to the insulator between the high-, medium-, and low-voltage coils differs greatly depending on these voltages. Therefore, the electric field in the creepage direction of the insulator between the coils greatly differs depending on the normal voltage, the lightning surge voltage, and the switch surge voltage, so that it has been difficult to design the equipment. Also, when the number of equipotential lines crossing the creepage of the insulator increases, the electric field in the creepage direction increases, which may cause insulation failure.
To solve this problem, increase the distance between the coil groups, optimize the curvature of the corner of the electrostatic plate at the end of the high-voltage coil, and devise the insulation configuration to minimize the creeping electric field generated in the surface direction of the insulating paper. I have tried not to happen.
However, even when these methods are used to reduce the size of the device, there is a problem that the electric field in the creeping direction of the insulating paper due to various voltages cannot be completely eliminated.

[0007]

As described above, in conventional transformers and reactors, the oil layer, which is a weak point on insulation, is filled with a material having a low dielectric constant or insulating paper in order to reduce the insulation distance. , Trying to adhere. However, the electric field distribution between the windings and the insulator of the main insulating part differs depending on the normal voltage applied to the transformer and the reactor, the impulse voltage, and so on. When an electric field is present and the insulation distance is reduced, the creeping electric field becomes stronger. Therefore, there is a limit in reducing the insulation distance, and there is also a problem in insulation reliability.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides a static induction device which has no insulation weakness portion in its structure, has excellent insulation performance against surge voltage, and can be reduced in size. With the goal.

[0009]

According to a first aspect of the present invention, there is provided a stationary induction machine having a coil group including one or more coils and an insulating layer surrounding the coil group. And an electrode whose voltage is controlled. The electrode and the insulating layer are arranged such that the electric field vector is perpendicular to the direction in which the insulating strength of the insulating layer is weak. According to a second aspect of the present invention, the coil group includes a plurality of coils, and the electrodes are arranged such that a distance from the coils is constant. The stationary induction device according to claim 3, wherein the coil group has a plurality of coils, and the electrodes are arranged such that a distance from each of the coils is a ratio corresponding to a voltage applied to each of the coils. is there.

According to a fourth aspect of the present invention, in the stationary induction device, the insulating layer is formed by stacking a plurality of partial insulating layers, and the partial insulating layer having a dielectric constant larger than the dielectric constant of the partial insulating layer disposed on the electrode side is formed by the coil. It is arranged on the side. The static induction device according to claim 5, wherein the partial insulating layer having a large dielectric constant is made of an insulating material in which press boards are laminated, and the partial insulating layer having a small dielectric constant is made of an insulating material in which a nonwoven fabric and a film are alternately laminated. is there. In the stationary induction device according to claim 6, the electrode is made of a non-magnetic material. In a stationary induction device according to a seventh aspect, the electrodes are made of a semiconductive material. According to a still further aspect of the present invention, the electrode is made of carbon-mixed paper. According to a ninth aspect of the present invention, in the stationary induction device, the electrodes are made of a comb-shaped conductive material. Claim 10
In the stationary induction device according to the above, the electrode is formed of a conductive net.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 An embodiment of the present invention will be described below. FIG. 1 is a cross-sectional view of a transformer, which is a stationary induction device, as viewed from above, and shows a cross section of a portion surrounded by an iron core. In the figure, only the upper half is shown, and the lower half, not shown, is the same, constituting a shell-type transformer.

In FIG. 1, 2 is a high-voltage winding and 3 is a low-voltage winding, which constitutes a current path. Reference numerals 21 and 31 denote coil groups of the high-voltage winding 2 and the low-voltage winding 3.
The high and low pressure sides are alternately arranged along the longitudinal direction of.
These coil groups 21 and 31 are arranged in an oval shape or a cylindrical shape around the iron core leg 41. In the case of the drawing, the high-voltage winding 2 includes one coil group 21 and the low-voltage winding 3 includes two coil groups 31. 2
Reference numerals 2 and 32 denote coils constituting the coil groups 21 and 31. Reference numeral 4 denotes an iron core, which is a magnetic circuit through which a magnetic flux generated by current flowing through the high and low voltage windings 2 and 3 has an iron core leg 41. Reference numeral 5 denotes an electrostatic plate, which is disposed on each line end side of the high and low voltage windings 2 and 3. 6 is coil group 2
An insulating layer surrounding the electrodes 1 and 23 insulates an electrode 8 described later. Reference numeral 8 denotes an electrode whose voltage is controlled (for example, to a ground potential), and is configured to surround the high and low voltage windings 2, 3, the electrostatic plate 5, and the insulating layer 6. These electrodes 8 are arranged so that the electric field vector is perpendicular to the direction in which the insulating strength of the insulating layer 6 is weak, that is, the creeping direction. Reference numeral 7 denotes a tank containing all of the above, and the inside is filled with insulating oil.

FIG. 2 is a sectional view showing the structure of the coils 22 and 23. The conductor 9 serving as a current path is configured by bundling a plurality of strands 10. As the strand 10, a metal flat wire having high conductivity such as copper or a copper alloy is used. The wire 10 is wound with a plastic film, insulating paper, or the like, or provided with an insulating coating to form the wire insulation 11, thereby reducing eddy current loss. The conductor 9 extends around the iron core leg 41. The voltage generated between the conductors 9 is insulated by the turn insulation 12 formed of the same or similar material as the wire insulation 11.

FIG. 3 is a cross-sectional view partially showing the structure of the insulator of the transformer and the positional relationship with the electrode whose voltage is controlled. The insulating structure near the end of the high-voltage winding 2 shown in FIG. This is shown in detail. In the figure, the insulating layer 6 is formed by laminating a press board (insulating paper) and is impregnated with insulating oil. The press board is a solid insulator having continuous minute gaps, and the gaps are impregnated with a liquid or a gas, in this case, an insulating oil to improve the insulation strength.
The insulating layer generally has a high dielectric strength in the thickness direction, and has a low dielectric strength against an electric field generated in the surface direction (creeping direction) of the insulating layer. Therefore, when performing insulation design, it is important to configure the insulating layer so as not to generate an electric field in the surface direction (creeping direction) of the insulating layer. Voltage controlled electrode 8
The electrodes 8 are arranged so as to suppress the electric field generated in the creeping direction of the insulating layer 6 by using. Then, the insulating layers 6 are formed by superimposing the press boats arranged along the electrodes 8. The electrode 8 may have an integral structure,
The structure may be divided into a plurality and electrically connected to each other.

FIG. 4 is a sectional view showing a potential distribution when an impulse voltage is applied to a line end of the high-voltage winding 2. Here, it is assumed that the electrode 8 is at the ground potential. 14 is an equipotential line. FIG. 5 is a cross-sectional view showing a potential distribution when a normal test voltage (induction test voltage) is applied to the high-voltage winding 2 and the low-voltage winding 3 by induction. 4 and 5, the use of the electrode 8 whose voltage is controlled makes the equipotential surface near the electrostatic plate 5 a potential distribution along the surface direction of the insulating layer 6.
Therefore, it is possible to suppress the electric field component appearing in the surface direction of the insulating layer 6. In addition, when an impulse voltage is applied, the equipotential lines are mixed more than the normal test voltage.
This is because the impulse voltage is applied about 1.5 to 3 times the voltage of the normal voltage. For example, in the case of composite insulation of oil and paper, the partial discharge voltage due to the impulse is about twice or more, so the impulse voltage is stricter. Therefore, the insulation configuration of the insulator in the winding portion is arranged based on the impulse voltage. In this specification, “regular” means “alternating current” with respect to “impulse”.

The electrode 8 whose voltage is controlled is made of a nonmagnetic conductive material having a sheet resistance of 0.01 to 10 Ω, preferably about 0.1 Ω. For this, metals such as copper, aluminum, and stainless steel, and other conductive films, nets, and carbon-mixed paper can be used. The upper limit of the surface resistance of the electrode 8 is determined by the condition that the potential in the same electrode 8 is constant with respect to the surge voltage and the condition that the heat generated by the charging current is within a predetermined limit.
It is determined by the condition that the efficiency decreases due to the eddy current loss due to the interlinkage of the magnetic flux and the heat generation due to the eddy current loss is within a predetermined limit.
In order to suppress the eddy current loss, the electrode 8 may be made of a conductive material such as a comb-shaped foil having a shape for preventing a circulating current. Further, when a material having a thermal expansion coefficient close to that of the insulating layer 6 is used as the electrode 8, even if a temperature change occurs during manufacturing or operation, the stress generated at the interface between the electrode 8 and the insulating layer 6 is small, and the occurrence of defects is reduced. Can be suppressed.

As can be seen from FIGS. 1 and 3, the voltage-controlled electrode 8 surrounds the coil 22 and the like, but the voltage is controlled at the external connection lead (not shown) and at the inlet and outlet of the cooling medium (insulating oil). It is necessary to provide a through hole (not shown) in the formed electrode 8. In this case, since an electric field concentrates on the end of the electrode 8, an electric field relaxation structure (not shown) is provided. This electric field relaxation structure can use a structure in which the curvature of the end of the electrode 8 is increased and the end of the through hole is covered with an insulator. Further, one or a plurality of electric field relaxation electrodes (not shown) may be separately provided in the vicinity of the through hole. Further, a non-linear resistance material can be used as a relaxing structure at the end of the electrode 8.
In FIG. 3, the distance between each coil 22 on the high voltage side and the electrode 8 is shown as being constant. However, since the dielectric strength required for each coil 22 is different, as shown in FIG. The distance between the electrodes 8 may be inclined so that the distance is in a ratio corresponding to the voltage applied to each coil 22 (for example, proportional to the applied voltage).

Embodiment 2 FIG. Hereinafter, other embodiments of the present invention will be described. FIG. 6 is a cross-sectional view of a part of a portion surrounded by an iron core when the transformer as the stationary induction device is viewed from above, and shows in detail an insulation configuration near the high-voltage winding 2 in FIG. . The overall schematic configuration is similar to that of the first embodiment described above.

In FIG. 6, the high voltage winding 2 and the low voltage winding 3 are arranged in an oval shape or a cylindrical shape around the iron core leg 4. In order to insulate the high and low voltage windings 2 and 3 from the core 4 and the electrode 8 whose voltage is controlled, an insulating layer 6 is arranged between them. The insulating layer 6 is a coil 2 for generating a high electric field.
Two or more kinds of partial insulating layers are arranged so that the dielectric constants thereof are inclined from the side of 2, 32 and the electrostatic plate 5. In FIG. 6, the insulating layer 6 is constituted by three types of partial insulating layers, that is, first to third partial insulating layers 61 to 63. The dielectric constant of the first partial insulating layer 61 is the largest, and the dielectric constant of the second and third partial insulating layers 62 and 63 decreases in this order. The third partial insulating layer 63 is configured by alternately laminating a nonwoven fabric and a film (both not shown). Voltage-controlled electrode 8
Is configured to surround the entire windings 2, 3, the electrostatic plate 5, and the insulating layer 6. The electrodes 8 are arranged so that the electric field vector is perpendicular to the direction (surface direction) where the insulation strength of the insulating layer 6 is weak.

In FIG. 6, the arc-shaped shape of the corner of the electrostatic plate 5 has a large curvature with respect to the thickness of the electrostatic plate. When the radius of curvature is reduced, the electric field concentration in the insulating layer 6 in this portion increases. In addition, since the electric field tends to increase near the winding, the insulating layer is made of a material having two or more kinds of dielectric constants in FIG. And place
An insulator having a low dielectric constant is arranged on the side of the electrode 8 where the electric field is low. Between the coils 22, 32, the electrostatic plate 5 and the electrode 8 whose voltage is controlled, a plurality of insulators having different dielectric constants are
By arranging 2, 32, and the electrostatic plate 5 to the electrode 8 in descending order of the dielectric constant, the electric field concentration at the end of the electrostatic plate 5, the end of the high voltage coil 22, and the end of the low voltage coil 32 can be suppressed, and the electric field strength can be reduced. It can be flattened. Embodiment 1
In Nos. 2 and 3, the high and low voltage windings 2 and 3 are provided with the electrostatic plate 5. However, the present invention can be similarly applied to a case where one or both windings have no electrostatic plate.

[0021]

As described above, the stationary induction device according to the first aspect of the present invention includes the insulating layer and the electrode surrounding the insulating layer and having a controlled voltage. So that the electric field vector is vertical
Since the electrodes and the insulating layer are arranged, the electric field in the surface direction of the insulating layer is suppressed with respect to the impulse voltage and the normal test voltage,
It is possible to effectively use the surface of the insulating layer having good dielectric strength. Therefore, there is an effect that the insulation performance can be improved and the insulation distance can be reduced. Further, according to the stationary induction device according to the second aspect, by disposing the electrode whose voltage is controlled at a fixed distance from the winding, the workability of the electrode and the insulating layer is improved. Therefore, the number of defective portions is reduced, and the insulation performance is improved. According to the stationary induction device of the third aspect, by arranging the electrodes whose voltage is controlled at a distance corresponding to the voltage of the winding, effective use of space is achieved, and furthermore, the electric field in the creepage direction of the insulating layer is reduced. This has the effect of improving the insulation performance and reducing the insulation distance.

According to the stationary induction device of the fourth aspect, an insulating layer is formed by laminating a plurality of partial insulating layers, a partial insulating layer having a large dielectric constant is arranged on the coil side, and a dielectric is formed on the electrode side. By arranging the partial insulating layer with a small ratio, it becomes possible to suppress the electric field concentration on the winding side,
This has the effect of improving the insulation performance and reducing the insulation distance.
Further, according to the stationary induction device according to claim 5, by using an insulating material in which a nonwoven fabric and a film are alternately laminated as a partial insulating layer having a small induction ratio, an elastic layer portion of the nonwoven fabric, that is, a solid Since there is no portion of only insulating oil having no insulator, weak points on insulation can be reduced, which has an effect of improving insulation performance.

According to the stationary induction device of the sixth aspect, since the non-magnetic material is used for the electrode whose voltage is controlled,
The electric field can be controlled without greatly disturbing the magnetic field generated by the current flowing through the coil, and this has the effect of improving the insulation performance. According to the stationary induction device according to claim 7, since a semiconductive material is used for the electrode whose voltage is controlled, the magnetic field generated by the current flowing through the conductor is
The electric field can be controlled without being greatly disturbed by the current flowing through the electrodes, which has the effect of improving the insulation performance. According to the stationary induction device of the eighth aspect, since the electrode whose voltage is controlled is made of carbon-mixed paper, the length, thickness, and density of the carbon fiber are selected so that the conductive layer has a desired surface resistance. Can be controlled. Further, when paper is used as the insulating layer, the compatibility with the carbon-mixed paper is good, and the coefficient of thermal expansion is close, so that a decrease in insulation reliability due to a temperature change or the like can be prevented. According to the static induction device of the ninth aspect, since the electrode whose voltage is controlled is a comb-shaped conductive material, a circulation path with a large eddy current cannot be formed even if a magnetic flux links the conductive layer. This has the effect of suppressing the occurrence of eddy current loss. According to the static induction device of the tenth aspect, since the electrode whose voltage is controlled is a conductive net, the conductive layer can be formed on a desired surface by selecting the material, wire diameter, density, and structure of the net. The resistance can be controlled.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a transformer according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view showing a configuration of a coil of the transformer according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of the transformer according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of the transformer according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view of the transformer according to the first embodiment of the present invention.

FIG. 6 is a sectional view of a transformer according to Embodiment 2 of the present invention.

[Explanation of symbols]

2 high voltage winding, 3 low voltage winding, 6 insulating layer, 8 electrodes,
21,31 coil group, 22,32 coil, 61
To 63 first to third partial insulating layers.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Taketoshi Hasegawa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Toyoichi Koan 2-3-2 Marunouchi, Chiyoda-ku, Tokyo No. Mitsubishi Electric Corporation (72) Inventor Noboru Hosokawa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Kiyoyuki Ishikawa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F term in Mitsubishi Electric Corporation (reference) 5E044 CA01 CA03 CA08 CB03 CB06 CC03 DA03

Claims (10)

[Claims] 1. A stationary induction machine having a coil group composed of one or more coils and an insulating layer surrounding the coil group, comprising: an electrode surrounding the coil group and the insulating layer and having a controlled voltage.
A stationary induction device, wherein the electrode and the insulating layer are arranged such that the electric field vector is perpendicular to the direction in which the insulating strength of the insulating layer is weak. 2. The coil group has a plurality of coils,
The stationary induction device according to claim 1, wherein the electrodes are arranged so that a distance from the coil is constant. 3. The coil group has a plurality of coils,
The stationary induction device according to claim 1, wherein the electrodes are arranged such that a distance from each of the coils is a ratio corresponding to a voltage applied to each of the coils. 4. An insulation layer comprising a plurality of partial insulation layers laminated, wherein said partial insulation layer having a dielectric constant higher than that of said partial insulation layer arranged on the electrode side is arranged on the coil side. The stationary guidance device according to any one of claims 1 to 3, characterized in that: 5. The partial insulating layer having a large dielectric constant is made of an insulating material in which a press board is laminated, and the partial insulating layer having a small dielectric constant is made of an insulating material in which a nonwoven fabric and a film are alternately laminated. 4. The stationary guidance device according to 4. 6. The stationary induction device according to claim 1, wherein the electrode is made of a non-magnetic material. 7. The static induction device according to claim 6, wherein the electrode is made of a semiconductive material. 8. The stationary induction device according to claim 6, wherein the electrode is made of a carbon mixed paper. 9. The static induction device according to claim 6, wherein the electrode is made of a comb-shaped conductive material. 10. The stationary guidance device according to claim 6, wherein the electrode is formed of a conductive net.