JPH0646609B2 - Oil-filled induction device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an oil-filled induction electric device.

[Conventional technology]

As described in Japanese Patent Laid-Open No. 53-74231, the conventional oil-filled induction device has an insulating material with a low dielectric constant only in the insulating cylinder arranged in the middle among a plurality of insulating cylinders arranged between high and low voltage windings. In order to reduce the insulation distance between the high and low voltage windings, that is, the main insulation distance, the electric field applied to the oil gap is relaxed. However, in practice, no consideration was given to the local relaxation of the electric field of the oil gap on the surface of the high and low voltage windings, which is the main factor that determines the insulation performance.

[Problems to be solved by the invention]

In general, under an unequal electric field, when the permittivity of the equipment constituting one part is changed in one part, the influence that it has on the electric field in other parts tends to decrease with distance. The electric field on the surface of the high and low voltage windings is an unequal electric field. The above-mentioned conventional technique changes the permittivity of the portion distant from the winding surface, and has a small relaxation effect on the oil gap electric field on the winding surface which is essential for insulation. In addition to the insulating cylinder, a linear spacer is also arranged between the high and low voltage windings to secure the insulation distance, and the electric field concentration due to the linear spacer is rather large on the surface of the winding in contact with it, and only the insulating cylinder has a low dielectric constant. The effect of relaxing the electric field in the oil gap on the surface of the winding was small even if it was made. In general, a low dielectric constant insulator is twice or more expensive as compared with a normal insulating material, and it is necessary to reduce the amount of use and to reduce the cost by effectively using it.

The present invention has been made in view of the above points, and an object thereof is to provide an oil-filled induction electric device capable of relaxing an oil gap electric field on a winding surface and shortening a main insulation distance. is there.

[Means for solving problems]

The above object is achieved by forming at least the outer insulating cylinder and the outer linear spacer of the outer insulating cylinder, the outer linear spacer, and the inner linear spacer with a low dielectric constant insulator having a dielectric constant smaller than that of the inner insulating cylinder. It

[Action]

Since at least the outer insulating cylinder and the outer linear spacer are formed of a low dielectric constant insulator, the dielectric constant is small at least inside the outer insulating cylinder and the outer linear spacer. Therefore, the electric field concentrates inside the outer insulating cylinder and the outer linear spacer. As a result, the electric field of the oil gaps adjacent to each other, that is, the oil gaps on the high and low voltage winding surfaces is alleviated, and the main insulation distance can be shortened. Further, in this case, the pulp fiber layer on the surface of the low-dielectric-constant insulator suppresses fluff that is harmful to the insulation on the surface of the low-dielectric-constant insulator, and prevents deterioration of the insulating performance due to the fluff.

〔Example〕

Hereinafter, the present invention will be described based on the illustrated embodiments. 1 to 3 show an embodiment of the present invention.
As shown in the figure, the oil-filled induction electric device is composed of a high-voltage winding 1 and a low-voltage winding 2 arranged concentrically, and a plurality of high-voltage windings 1 and 2 arranged between the high-voltage winding 1 and the low-voltage winding 2. The insulating cylinder 3 and the linear spacer 4 are provided. These insulating cylinders 3 and linear spacers 4 are outer linear spacers 4a and 4c arranged between the high and low voltage windings 1 and 2 in contact with the high and low voltage windings 1 and 2, respectively, and these outer linear spacers 4a and 4c.
The outer insulating cylinders 3a and 3c arranged in contact with the outer linear spacers 4a and 4c, respectively, and the inner insulating cylinder 3b and the inner linear spacer 4b arranged between the outer insulating cylinders 3a and 3c, High and low voltage windings 1 and 2, insulating tube 3
An oil layer 5 is formed between the (outer insulating cylinders 3a, 3c, the inner insulating cylinder 3b) and the linear spacer 4 (the outer linear spacers 4a, 4c, the inner linear spacer 4b). Thus, a plurality of insulating cylinders 3 and linear spacers 4 are alternately arranged between the high-voltage winding 1 and the low-voltage winding 2, and these are immersed in mineral oil to form a composite insulating layer, that is, in a transformer. The main insulation 6 is formed. The high-voltage winding 1 has a high-voltage terminal 7 at the center, and a voltage V is generated there. The upper and lower ends are the neutral point terminals 8 and 8a, and no voltage is generated here. Since the dielectric breakdown strength of the mineral oil itself in this main insulation 6 is lower than that of the solid insulating material forming the winding coating, the insulating cylinder 3 and the linear spacer 4, the dielectric breakdown first occurs from the oil layer 5. Insulation tube 3
Shows a phenomenon that the oil gap is subdivided, and the shorter the oil gap length, the higher the dielectric breakdown strength of the oil gap.
It also has the function of increasing the insulation strength, preventing the streamer from developing even if an oil gap causes dielectric breakdown, and preventing the dielectric breakdown between the high voltage winding 1 and the low voltage winding 2. The linear spacer 4 serves to keep the oil layer 5 at a predetermined oil gap length.

In the oil-filled induction electric device configured as described above, the outer insulating cylinders 3a and 3c and the outer linear spacers 4a and 4c in the present embodiment have a low dielectric constant smaller than that of the inner insulating cylinder 3b and the inner linear spacer 4b. It is formed of the insulator 9. By doing so, the outer insulating cylinders 3a and 3c and the outer linear spacers 4a and 4c become the inner insulating cylinder 3b and the inner linear spacer 4b.
Is formed of a low dielectric constant insulator 9 having a dielectric constant smaller than that of the electric field, and the electric field is concentrated on the outer insulating cylinders 3a and 3c and the outer linear spacers 4a and 4c. The electric field of the oil gap on the surfaces 1 and 2 is relaxed, the electric field of the oil gap on the surface of the winding is relaxed, and the oil-filled induction electric device capable of shortening the main insulation distance can be obtained.

That is, the outer insulating cylinders 3a and 3c, the outer linear spacer 4
Although a and 4c are formed of the low dielectric constant insulator 9, the low dielectric constant insulator 9 is formed of the low dielectric constant portion 9a and the pulp fiber 9b covering the low dielectric constant portion 9a. That is, pulp fibers and synthetic fibers having a low dielectric constant and high oil resistance, such as polyethylene terephthalate (PET) and polypropylene (P
The P) fiber was mixed with any of the fibers to form a low inductive conductivity section 9a, and pulsed fibers 9b of 100% pulp were mixed on the surface. Incidentally, the inner insulating cylinder 3b and the inner linear spacer 4b are made of ordinary insulating paper. By doing so, the electric field in the oil gaps on the surfaces of the high and low voltage windings 1 and 2 can be relaxed. The results of a comparative study with the conventional example will be described below.

FIG. 4 shows the results of an investigation of the electric field in the central portion of the main insulation 6 of this example by the numerical electric field calculation method. The equipotential lines 10 are shown by dotted lines in the figure. As shown in the figure, the equipotential lines 10 are almost parallel and close to a uniform electric field in the middle portion, but near the surfaces of the high voltage winding 1 and the low voltage winding 2, the equipotential lines 10 are uneven due to the unevenness of the winding surfaces. 10 is undulating and becomes an unequal electric field. The electric field distribution near the surface of the high voltage winding 1 is shown in FIG. Usually, the electric field is most concentrated in the oil gap 13 between the insulating coating 12 of the electric wire 11 that constitutes the high-voltage winding 1 and the outer linear spacer 4a, and the electric discharge occurs first here, and then it becomes the starting point and the whole In many cases, dielectric breakdown occurs. By the way, in the case of the present embodiment, as is clear from the figure, the interval between the equipotential lines 10 near the oil gap 13 is not narrowed, and the electric field concentration in the oil gap 13 is small. On the other hand, the electric field distribution of the conventional example is as shown in FIG.
The electric field is concentrated in the vicinity. As described above, the present example shows a better result than the conventional one because the outer linear spacer 4a and the outer insulating cylinder 3a of the conventional example have a large inductivity.
The inside of each of them is relaxed by an electric field, and the amount of the relaxed electric field is wrinkled into the oil gap 13 having a small dielectric constant, whereas in the present embodiment, the dielectric constants of the outer linear spacer 4a and the outer insulating cylinder 3a adjacent to each other are small. Therefore, the electric field is concentrated inside each of them.

On the other hand, the insulation strength of the oil gap is influenced by the surface condition of the adjacent insulating material, particularly the fuzz, and tends to decrease as the fuzz increases. In this respect, the usual low-dielectric-constant insulator is a mixture of pulp fibers and synthetic fibers with low-dielectric constant. Reduces the insulation strength of the gap.

By the way, in the case of the present embodiment, since the surface of the synthetic fiber which is the low dielectric constant portion 9a is covered with 100% pulp fiber 9b,
A surface condition similar to that of ordinary insulating paper is obtained, and the insulating strength of the oil gap is not reduced.

Therefore, if the electric field of the conventional oil gap is set as the allowable electric field of the oil gap of this embodiment, the insulation distance between the high-voltage winding 1 and the low-voltage winding 2, that is, the main insulation distance is shortened, and this embodiment is adopted. Even if the electric field of the oil gap in this case is increased to the allowable electric field, the insulation strength of the main insulation 6 does not change. Therefore, according to the present embodiment, the main insulation distance can be shortened and the winding can be miniaturized as compared with the conventional case without lowering the insulation strength of the main insulation 6. By the way, when the conventional main insulation distance is 70 mm, the number of insulating cylinders 3 is 5, and the thickness thereof is 5 mm, it is calculated as follows when the low dielectric constant insulator 9 having a relative dielectric constant of about 3.5 is used. In comparison, the main insulation distance can be shortened by 10 mm, and the ratio can be reduced by about 15%. All the insulating cylinders 3 and the linear spacers 4 are made of a low dielectric constant insulator 9
Even in the case of the above construction, the length is reduced by 15 mm, and the effect of this embodiment is great. In addition, since the winding diameter is naturally reduced by shortening the main insulation distance, the width and length of the transformer tank can be shortened, and the tank can be downsized and the amount of oil can be reduced.

FIG. 7 shows another embodiment of the present invention. In this embodiment, the outer insulating cylinders 3a and 3c, the outer linear spacer 4a,
4c and the inner linear spacer 4b are formed of a low dielectric constant insulator. By doing so, the outer insulating cylinders 3a, 3
Since the outer linear spacers 4a, 4c and the inner linear spacers 4b are formed of a low dielectric constant insulator, the electric field on the winding surface can be reduced by a slight increase of the low dielectric constant insulator as compared with the above case. The main insulation can be relaxed more than 6
The distance a can be shortened as compared with the above case.

That is, as shown in FIG. 8 in which the electric field distribution near the surface of the high-voltage winding 1 is shown, the equipotential line 14 of this embodiment shown in solid line is the equipotential line 10 shown in dotted line. Compared to the above, the inner side is separated from the high voltage winding 1. This is because the electric field is concentrated in the inner linear spacer 4b due to the decrease in the dielectric constant and the interval between the equipotential lines 14 is narrowed.
In the oil gap 13 on the surface, the equipotential lines 14 are wider than in the case described above. That is, the electric field is relaxed more than in the above case. In this case, even if all of the linear spacers 4 are combined, it is about 1/10 of the volume of the insulating cylinder 3. Therefore, even if the inner linear spacer 4b is made of a low dielectric constant insulator, a low dielectric constant insulator is used as compared with the above case. The quantity only increases slightly.

FIG. 9 shows still another embodiment of the present invention. In this embodiment the top 3a ₁ the outer insulating tube 3a, the central portion 3a _2, lower
3a _{3 has} a three-part structure, and each of them is taper-joined in order to be integrated. The central portion 3a ₂ has a length of about ½ of the entire length of the insulating cylinder 3a and is made of a low dielectric constant insulator. Similarly, the other outer insulating cylinder 3c and outer linear spacers 4a, 4c
For 3c _{1 also, 3c 2, 3c 3, 4a} 1, 4a 2, 4a 3 and 4c _1, 4c _2, 4c ₃
And a central part 3c ₂ , 4a ₂ and 4c ₂ is composed of a low dielectric constant insulator, and an upper part 3c ₁ , 4a ₁ , 4c ₁ and a lower part 3c ₃ , 4
The a ₃ and 4c ₃ were made of ordinary insulating paper to form the main insulating 6b. By doing so, the cost can be reduced without lowering the insulation strength as compared with the case described above.

FIG. 10 shows the distribution of the voltage difference between the high voltage winding 1 and the low voltage winding 2 when a lightning impulse voltage is applied to the high voltage terminal 7 of the high voltage winding 1 of this embodiment. In the figure, the horizontal axis is the vertical position of the high voltage winding with the position of the high voltage terminal being 0% and the position of the neutral point terminal being 100%, and the vertical axis is the high voltage winding and low voltage winding at each position in the vertical direction. It is the voltage difference between the lines. Generally, the distribution of the differential voltage tends to rise near the high voltage terminal due to the potential oscillation phenomenon of the winding. Therefore, as shown in the same figure, a differential voltage equal to or higher than the applied voltage is generated up to a position far away from the high voltage terminal. When this tendency is the largest, it extends from the high-voltage terminal to a position close to 50%. By the way, in the case of the present embodiment, since up to this 50% position is made of the low dielectric constant insulator, it has the same insulation strength as that of the embodiment shown in FIG. Since the remaining area has a small voltage difference, normal insulating paper will not cause any insulation problems. That is, the amount of expensive low-dielectric-constant insulator is reduced to obtain the same insulation strength as in the above case.

FIG. 11 shows still another embodiment of the present invention.
In this embodiment, the high-voltage winding 1 is composed of a so-called winding wire having a high-voltage terminal 7 at the upper end and a neutral point terminal 8 at the lower end.
Outer insulating cylinders 3a, 3c and outer linear pacers 4a, 4c
3a ₄ , 3a ₅ , 3c ₄ , 3c ₅ and 4a ₄ , 4a ₅ , 4c ₄ , 4c ₅ up and down 2 respectively
Partial structure, the upper part 3a ₄ , 3c ₄ , 4a ₄ , 4c ₄ is composed of low dielectric constant insulator, the lower part 3a ₅ , 3c ₅ , 4a ₅ , 4c ₅ is composed of normal insulating paper 6c was formed. In this way, the upper part where the differential voltage between the high voltage winding 1 and the low voltage winding 2 is large is made of a low dielectric constant insulator, and the lower part where the differential voltage is small is made of ordinary insulating paper. It is similar to the above case, and the same effect as the above case can be obtained.

〔The invention's effect〕

As described above, according to the present invention, the oil gap electric field on the winding surface can be relaxed and the main insulation distance can be shortened. Therefore, the oil gap electric field on the winding surface can be mitigated and the main insulation distance can be shortened. It is possible to obtain the oil-filled induction device.

[Brief description of drawings]

1 is a vertical sectional side view of an embodiment of the oil-filled induction device of the present invention, FIG. 2 is a vertical sectional side view of a low dielectric constant insulator of the same embodiment, and FIG. 3 is a top view of FIG. FIG. 4 is an electric field distribution diagram showing the electric field distribution in the central portion of the main insulation of the same embodiment, FIG. 5 is an enlarged electric field distribution diagram showing the electric field distribution in the vicinity of the surface of the high voltage winding of the embodiment, and FIG. FIG. 7 is an enlarged electric field distribution diagram showing an electric field distribution in the vicinity of the high voltage winding surface of a conventional oil-filled induction device, FIG. 7 is a vertical side view of another embodiment of the oil-filled induction device of the present invention, and FIG. An enlarged electric field distribution diagram showing an electric field distribution in the vicinity of the surface of the high-voltage winding of the embodiment, FIG. 9 is a vertical sectional side view of still another embodiment of the oil-filled induction machine of the present invention, and FIG. 10 is still another embodiment. FIG. 11 is a vertical cross-sectional side view of yet another embodiment of the oil-filled induction device according to the present invention. DESCRIPTION OF SYMBOLS 1 ... High voltage winding, 2 ... Low voltage winding, 3 ... Insulating cylinder, 3a ... Outer insulating cylinder, 3b ... Inner insulating cylinder, 3c ... Outer insulating cylinder, 4 ... Linear spacer, 4a ... Outer linear spacer, 4b ... Inner linear Spacer, 4c ... Outer linear spacer, 5 ... Oil layer, 6, 6
a, 6b, 6c ... Main insulation, 9 ... Low dielectric constant insulator, 9a ...
Low dielectric constant part, 9b ... Pulp fiber, 13 ... Oil gap.

Claims (3)

[Claims] 1. A low-voltage winding and a high-voltage winding arranged concentrically, and a plurality of insulating cylinders and linear spacers arranged between the low-voltage winding and the high-voltage winding. The linear spacers are outer linear spacers arranged between the high and low voltage windings so as to be in contact with the high and low voltage windings, outer insulating cylinders arranged between the outer linear spacers and are respectively in contact with the outer linear spacers, and outer insulating cylinders thereof. In an oil-filled induction machine having an inner insulating cylinder and an inner linear spacer arranged between them, and an oil layer being formed between the high and low voltage windings, the insulating cylinder, and the linear spacer, the outer insulating cylinder, the outer An oil characterized in that at least the outer insulating cylinder and the outer linear spacer of the linear spacer and the inner linear spacer are formed of a low dielectric constant insulator having a dielectric constant smaller than that of the inner insulating cylinder. Induction apparatus. 2. The oil according to claim 1, wherein the low dielectric constant insulator is formed of a low dielectric constant portion and pulp fibers provided on the surface of the low dielectric constant portion. Induction electric appliance. 3. The oil-filled induction device according to claim 2, wherein the low dielectric constant portion is a mixture of pulp fiber and any one of polyethylene terephthalate and polypropylene fiber.