JPH10172836A - Gas insulated transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent gas-insulated transformer that can improve the insulation properties of metal bolts, contribute to downsizing of a tank, and have a low manufacturing cost. A metal bolt (7) is provided on a holding plate (6) for holding an iron core (5), and a lead wire (4) is arranged near the bolt (7). A plastic insulating cap 8a having an insulating property is attached to the head of the bolt 7 so as to cover the head. In such a gas-insulated transformer, since the insulating cap 8a is in contact with the bolt 7 head, the electric charge released from the bolt 7 head is charged on the inner surface of the insulating cap 8a, and the electric field of the bolt 7 is reduced. Can be. Therefore, the insulation distance between the bolt and the lead wire 4 can be reduced. In addition, since the plastic insulating cap 8a can have appropriate plasticity, the work of attaching the insulating cap 8a to the head of the bolt 7 can be easily performed in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas-insulated transformer in which metal bolts are arranged near high-voltage charging sections such as windings and lead wires, and more particularly, to an improvement in an insulation structure for the bolts. It relates to an added gas insulated transformer.

[0002]

2. Description of the Related Art Generally, a transformer for converting AC and DC is installed in an AC / DC conversion station in DC transmission. As such a transformer, an oil-insulated transformer using insulating oil as an insulating medium has been conventionally known. However, in recent years, a gas insulated transformer using a nonflammable insulating gas as an insulating medium has been proposed instead of the oil insulated transformer for reasons of disaster prevention.

[0003] There are various types of this gas insulated transformer, for example, a dry type in which both cooling and insulation are performed by an insulating gas, a semi-pool type and a spray type in which a cooling liquid and an insulating gas are combined, and a further type. Is a separate type that performs cooling and insulation separately. Of these, dry type gas insulated transformers are simpler and less expensive than other types and do not use expensive coolant, and are applicable to high voltage, large capacity transformers. It has the advantage of being able to do it, and has attracted widespread attention.

Here, a conventional example of a dry-type gas-insulated transformer will be specifically described with reference to FIG. The dry-type gas-insulated transformer has almost the same winding configuration as a conventional oil-insulated transformer except that the insulating medium is changed from insulating oil to insulating gas, and a polymer film is laminated on a copper wire. It uses a twisted element wire.

As shown in the figure, a sealed tank 2 is filled with an insulating gas 10 and a connection tank 3 is connected. In the tank 2, a coil in which a plurality of layers of the windings 1 are arranged around a core 5 is housed as a high-voltage charging unit. The core 5 is similar to that of the oil-insulated transformer,
It is configured by bundling a plurality of thin silicon steel plates and amorphous magnetic materials, and is held down by a holding plate 6. The holding plate 6 is arranged at the upper end and the lower end of the iron core 5, and is mechanically fixed to the iron core 5 by metal bolts 7.

[0006] The above-mentioned gas-insulated transformer uses the non-combustible insulating gas 10, so it is very advantageous from an oil-insulated transformer in terms of disaster prevention, but is larger than an oil-insulated transformer. It is pointed out that the weight tends to be heavy.
This is because the heat capacity of the insulating gas 10 is smaller than the heat capacity of the insulating oil, so that a large passage for flowing the insulating gas 10 in the tank 2 must be ensured, and the tank 2 becomes larger accordingly. It is. That is, in order to obtain a gas-insulated transformer having the same voltage and current capacity as the oil-insulated transformer, a large amount of the insulating gas 10 is circulated per unit time as compared with the insulating oil, and the heat generated by the loss generated in the winding 1 is reduced. It needs to be cooled sufficiently. In order to satisfy this need, the tank 2 must be increased in size without increasing the flow path of the insulating gas 10.

Therefore, in the gas insulated transformer, miniaturization of the tank 2 is one of the important issues, and when a structure is housed in the tank 2, the structure is arranged in consideration of the space efficiency. ing. For example, it is desirable that the lead wire 4 for leading the winding wire 1 be passed through a physically vacant space, and is generally arranged near the upper end and the lower end of the iron core 5.

As described above, the holding plate 6 is disposed at the upper end and the lower end of the iron core 5, and a metal bolt 7 is mounted on the holding plate 6. Therefore, the lead wire 4 near the upper end and the lower end of the iron core 5 passes near the bolt 7. An enlarged view of this state is shown in FIG. Note that reference numeral 17 in FIG. 11 denotes a washer.

When the lead wire 4 and the bolt 7 are close to each other, an electric field is applied to the bolt 7 when a voltage such as a test voltage is applied to the lead wire 4. At this time, bolt 7
Because the electric field is very unequal at the edge of the head of,
Partial discharge may occur. For this reason, conventionally, an insulating configuration for relaxing the electric field of the bolt 7 is employed. Specifically, the insulation distance between the lead wire 4 and the bolt 7 is increased, or a metal electrostatic shield 11 machined to the bolt 7 is attached to the bolt 7 as shown in FIG. Further, for the purpose of improving the insulation properties of the bolt 7 itself, the bolt 7 is covered with an insulating film, and the surface of the bolt 7 is coated with an insulating paint.

[0010]

However, the insulating structure of the bolt 7 in the above-described gas insulating transformer has the following problems. First, if the insulation distance between the lead wire 4 and the bolt 7 is increased, the size of the tank 2 will be increased, and the miniaturization of the tank 2, which is an important issue of the gas insulated transformer, cannot be achieved.

In the configuration using the electrostatic shield 11, the electrostatic shield 11 has a large shape in order to reduce the electric field of the bolt 7, and it is difficult to mount the electrostatic shield 11 on a narrow portion. Moreover, the price of the metal electrostatic shield 11 is high,
If it were to be installed for each bolt 7, the production cost of the gas insulated transformer would have increased.

Furthermore, when the head of the bolt 7 is covered with an insulating film, the head includes an edge portion.
It takes a long time to attach the insulating film. As a result, there was a high possibility that the production cost would be higher than attaching the metal electrostatic shield 11.

As for the application of the insulating paint to the surface of the bolt 7, the insulating paint is applied before the bolt 7 is attached to the holding plate 6, and the insulating paint is applied after the bolt 7 is tightened. However, each has the following problems. That is, in the former, the insulating paint may be peeled off by the bolt tightening operation. In the latter case, the working area is limited and the painting operation becomes difficult, so that the production cost is increased.

The present invention has been proposed to solve the above-mentioned problems of the prior art, and its object is to improve the insulating properties of metal bolts and contribute to miniaturization of tanks. An object of the present invention is to provide an excellent gas-insulated transformer which is inexpensive and has a low manufacturing cost.

[0015]

In order to achieve the above object, according to the first aspect of the present invention, a tank filled with an insulating gas is provided, and a structure including a high-voltage charging section is accommodated in the tank. In a gas-insulated transformer in which metal bolts for fixing the structure in proximity to the high-voltage charging section are provided, the head of the bolt has an insulating property so as to cover the head. A plastic insulating cap is attached.

According to the first aspect of the present invention, since the insulating cap made of a plastic insulator is in contact with the head of the bolt, the electric charge released from the head of the bolt is charged on the inner surface of the insulating cap. The electric field can be reduced. Therefore, generation of partial discharge can be suppressed, and the electric field generated by partial discharge can be increased. Also, even if a partial discharge occurs at the head of the bolt and progresses, the insulation cap covers the head of the bolt, so there is no insulation breakdown until the bolt penetrates the plastic, and the insulation properties of the bolt are Significantly improved. Thereby, the insulation distance between the volt and the high-voltage charging unit can be shortened. In addition, since the plastic insulating cap can have appropriate plasticity, the work of attaching to the bolt head can be easily performed in a short time.

According to a second aspect of the present invention, in the gas insulating transformer according to the first aspect, a curved surface portion is formed on an inner surface of the insulating cap.

In the second aspect of the present invention, the partial discharge generated at the head of the bolt propagates along the inner surface of the insulating cap, and the discharge is present on the curved surface of the insulating cap. This discharge behaves like an electrode having a curved surface. Therefore, the insulating properties of the bolt are greatly improved.

According to a third aspect of the present invention, in the gas insulating transformer according to the first or second aspect, a conductive layer is formed on an inner surface of the insulating cap.

According to the third aspect of the present invention, by forming the conductive layer on the inner surface of the insulating cap, the electric field of the bolt can be reduced as in the case where the metal electrostatic shield is attached to the bolt. it can. In addition, the plastic insulating cap is inexpensive as compared with the metal electrostatic shield, and the mounting work on the bolt can be performed very easily.

According to a fourth aspect of the present invention, in the gas insulated transformer according to the first or second aspect, the insulating cap is made of a conductive plastic.

According to the fourth aspect of the present invention, since the insulating cap itself has conductivity, the step of forming a conductive layer on the insulating cap is not required, and the operation similar to that of the third aspect of the present invention is very easily performed. Can be obtained.

According to a fifth aspect of the present invention, in the gas insulating transformer according to any one of the first to third aspects, a fixing claw for fixing the insulating cap to the bolt is formed on the insulating cap. And

According to the fifth aspect of the invention, the insulating cap can be securely fixed to the bolt side by the function of the fixing claw. Further, since the thickness of the insulating cap is increased by the amount corresponding to the formation of the fixing claw, the insulating cap is less likely to be broken, and the cap can be prevented from being damaged when the insulating cap is attached to the bolt.

The invention of claim 6 is the invention of claims 1, 2, 3, 4
6. The gas insulated transformer according to claim 5, wherein a through hole is formed in the insulating cap.

According to the sixth aspect of the present invention, after the insulating cap is attached to the bolt, a tester can be inserted into the through hole to check whether the bolt is at the ground potential. That is, the work of confirming the ground potential can be performed without removing the insulating cap from the bolt, and the inspection workability is improved.

[0027] The invention of claim 7 is based on claims 1, 2, 3,
7. The gas-insulated transformer according to 4, 5, or 6, wherein the insulating cap is made of heat-shrinkable plastic.

According to the seventh aspect of the present invention, since the insulating cap has heat shrinkability, after the insulating cap is attached to the bolt, the insulating cap is heated and contracted, so that the insulating cap can be easily bolted. The electric charge released from the bolt head can be charged on the inner surface of the insulating cap, and the electric field can be surely alleviated.

The invention according to claim 8 is based on claims 1, 2, 3,
The gas insulating transformer according to 4, 5, 6, or 7, wherein the insulating cap is made of a transparent plastic.

According to the eighth aspect of the present invention, since the insulating cap is transparent, it can be visually confirmed whether the insulating cap is properly attached to the bolt. Therefore, the mounting workability can be further improved.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a gas-insulated transformer according to the present invention will be specifically described below with reference to the drawings. Note that the same members as those in the conventional example shown in FIG. 11 are denoted by the same reference numerals, and description thereof will be omitted.

(1) First Embodiment [Configuration] A first embodiment corresponding to the first aspect of the present invention will be specifically described with reference to FIGS. FIG. 1 is a schematic diagram showing the arrangement of the insulating cap, bolts and lead wires in the first embodiment, and FIG. 2 is a sectional view of the insulating cap and a front view of the bolt in the first embodiment.

As shown in FIGS. 1 and 2, an insulating cap 8a having an insulating property is attached to the head of the bolt 7 so as to cover the head. This insulating cap 8
a is made of a plastic material having a thickness of 100 μm or more, such as polyethylene terephthalate (PET) or polyethylene (PE).

[Effects] In the first embodiment, since the insulating cap 8a is in contact with the edge of the head of the bolt 7, the electric charge released from the edge is deposited on the inner surface of the insulating cap 8a. Charges. Therefore, bolt 7
Can be alleviated, and the occurrence of partial discharge can be suppressed. Even if the generated partial discharge progresses, the insulating cap 8a covers the head of the bolt 7, so that no dielectric breakdown occurs until the insulating cap 8a penetrates the insulating cap 8a, and the insulating characteristics of the bolt 7 are improved. Significantly improved. As a result, the insulation distance between the lead wire 4 and the bolt 7 can be significantly shortened, which can lead to downsizing of the tank 2. Moreover, the plastic insulating cap 8
Since a can have appropriate plasticity, the work of attaching to the head of the bolt 7 can be easily performed in a short time. Therefore, the production cost of the gas insulated transformer can be reduced.

(2) Second Embodiment A second embodiment corresponding to the second aspect of the present invention will be specifically described with reference to FIG. FIG. 3 is a sectional view of the insulating cap according to the second embodiment.

[Structure] Insulating cap 8 of the second embodiment
FIG. 2B is characterized in that a hemispherical portion 81b is formed on the upper side of its inner surface.

[Function and Effect] In the second embodiment, the partial discharge generated at the head of the bolt 7 propagates along the inner surface of the insulating cap 8b, and discharges over the entire hemispherical portion 81b of the insulating cap 8b. Will be present. Since this discharge behaves like a hemispherical electrode, the insulation properties of the bolt 7 are greatly improved.

[Modification of Second Embodiment] As a modification of the second embodiment, as shown in FIG. 4, an insulating cap 8c having a curved surface portion 81c having a smooth upper surface as shown in FIG.
As shown in FIG. 5, there is an insulating cap 8d having a curved surface portion 81d only on the peripheral portion of the upper surface. These insulating caps 8
With c and 8d, the same operation and effect as in the second embodiment can be exhibited.

(3) Third Embodiment A third embodiment corresponding to the invention of claim 3 will be specifically described with reference to FIG. FIG. 6 is a sectional view of the insulating cap according to the third embodiment.

[Configuration] Insulating cap 8 of the third embodiment
In e, similarly to the insulating cap 8c, a curved surface portion 81e having a smooth upper surface is formed. The conductive layer 12 is formed on the inner surface of the insulating cap 8e along the curved surface portion 81e.

[Effects] In the third embodiment described above, since the curved surface portion 81e is provided, the same effects as those in the second embodiment can be obtained. In addition, in the third embodiment, since the conductive layer 12 is formed on the inner surface of the insulating cap 8e, the electric field of the bolt 7 is reduced as in the case where the conventional electrostatic shield 11 is attached to the bolt 7. Can be realized. Moreover, the insulating cap 8e made of plastic is inexpensive as compared with the electrostatic shield 11 made of metal, and the mounting work on the bolt 7 can be performed very easily. Therefore, the manufacturing cost of the gas-insulated transformer can be significantly reduced as compared with the related art.

(4) Fourth Embodiment A fourth embodiment corresponding to the invention of claim 5 will be specifically described with reference to FIG. FIG. 7 is a sectional view of an insulating cap and a front view of a bolt according to a fourth embodiment.

[Configuration] As shown in FIG. 7, an inwardly protruding fixing claw 13 is formed at the lower peripheral edge of the insulating cap 8f. The lower edge of the head of the bolt 7 is provided with a notch 71 cut out downward, and the fixing claw 13 is fitted therein. The shape of the insulating cap 8f is substantially the same as that of the insulating cap 8c (see FIG. 4).

[Function and Effect] In the fourth embodiment, the fixing cap 13 is fitted into the cutout of the head of the bolt 7, so that the insulating cap 8f can be securely fixed to the head of the bolt 7. . In addition, the thickness of the lower peripheral portion of the insulating cap 8f increases by the amount of the fixing claw 13 formed. For this reason, the insulating cap 8f is less likely to be broken, and the insulating cap 8f can be prevented from being damaged when the insulating cap 8f is attached to the bolt 7. The insulating cap 8
Since the shape of f is substantially the same as that of the insulating cap 8c (see FIG. 4), the same effect as that of the second embodiment can be obtained.

(5) Fifth Embodiment A fifth embodiment corresponding to the invention of claim 6 will be specifically described with reference to FIG. FIG. 8 is a sectional view of the insulating cap according to the fifth embodiment.

[Structure] As shown in FIG. 8, a through hole 14 is formed in the side surface of the insulating cap 8g. In addition,
The shape of the insulating cap 8g is substantially the same as that of the insulating cap 8c (see FIG. 4).

[Effect] In the fifth embodiment, even after the insulating cap 8g is attached to the bolt 7, the insulating cap 8g is not removed from the bolt 7,
By inserting a tester through the through hole 14, the ground potential of the bolt 7 can be confirmed. Thereby, inspection workability can be improved. The shape of the insulating cap 8g is as follows.
Since it is almost the same as the insulating cap 8c (see FIG. 4), it can have the same operation and effect as the second embodiment.

(6) Other Embodiments The present invention is not limited to the above-described embodiments, and a combination of the embodiments can be appropriately selected, and the shapes and dimensions of the constituent members are not limited. It is free as appropriate. For example, regarding the shape of the insulating cap, the outer shape may be a hexagon as in an insulating cap 8h shown in FIG. Further, when a plurality of insulating caps having different insulating performances are used, color confirmation or change of a mark for each type of the insulating cap can be performed to facilitate the number confirmation and inventory management.

Regarding the material of the insulating cap, an embodiment in which the insulating cap is made of a heat-shrinkable plastic (corresponding to the invention of claim 7) and an embodiment in which the insulating cap is made of a transparent plastic ( (Corresponding to the invention of claim 8). According to the former embodiment, since the insulating cap has heat shrinkability, the insulating cap can be heated and shrunk after the insulating cap is attached to the bolt. Therefore, the insulating cap can be easily brought into close contact with the bolt head, and the electric charge released from the bolt head can be charged on the inner surface of the insulating cap, thereby reliably reducing the electric field. On the other hand, according to the latter embodiment, since the insulating cap is transparent, it is possible to visually check whether the insulating cap is properly attached to the bolt, and mounting workability is further improved.

Further, as an embodiment including the invention of claim 4, it is possible to propose a structure in which the insulating cap itself is made of a conductive plastic instead of forming a conductive layer on the insulating cap. In such an embodiment, the same operation and effect as those of the third embodiment can be obtained extremely easily without going through a step of forming a conductive layer on the insulating cap.

[0051]

According to the gas insulated transformer of the present invention, a plastic insulating cap having insulating properties is provided on the head of a metal bolt for fixing a structure so as to cover the head. With a simple configuration such as mounting, the insulation properties of the metal bolts can be improved, the tank can be downsized, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an arrangement of an insulating cap, a bolt, and a lead wire according to a first embodiment of the present invention.

FIG. 2 is a sectional view of an insulating cap and a front view of a bolt according to the first embodiment.

FIG. 3 is a sectional view of an insulating cap according to a second embodiment of the present invention.

FIG. 4 is a sectional view of an insulating cap according to a modification of the second embodiment;

FIG. 5 is a sectional view of an insulating cap according to a modification of the second embodiment;

FIG. 6 is a sectional view of an insulating cap according to a third embodiment of the present invention.

FIG. 7 is a sectional view of an insulating cap and a front view of a bolt according to a fourth embodiment of the present invention.

FIG. 8 is a sectional view of an insulating cap according to a fifth embodiment of the present invention.

FIG. 9 is a perspective view of an insulating cap according to another embodiment of the present invention.

FIG. 10 is a schematic diagram of a general gas-insulated transformer.

FIG. 11 is a schematic view showing an arrangement of bolts and lead wires in the gas-insulated transformer shown in FIG.

FIG. 12 is a schematic view of a bolt to which an electrostatic shield is attached.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Winding 2 ... Tank 3 ... Connection tank 4 ... Lead wire 5 ... Iron core 6 ... Holding plate 7 ... Bolt 71 ... Notch 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h ... Insulating cap 9 ... Curved surface Part 10: Insulating gas 11: Electrostatic shield 12: Conductive layer 13: Fixed claw 14: Through hole 17: Washer

Claims (8)

[Claims] 1. A tank filled with an insulating gas is provided, a structure including a high-voltage charging unit is housed in the tank, and a metal for fixing the structure in proximity to the high-voltage charging unit. A gas-insulated transformer in which a bolt made of stainless steel is disposed, wherein an insulating cap made of plastic having an insulating property is attached to a head of the bolt so as to cover the head. . 2. The gas insulating transformer according to claim 1, wherein a curved surface portion is formed on an inner surface of the insulating cap. 3. The gas insulating transformer according to claim 1, wherein a conductive layer is formed on an inner surface of the insulating cap. 4. The gas insulating transformer according to claim 1, wherein the insulating cap is made of a conductive plastic. 5. The gas insulating transformer according to claim 1, wherein a fixing claw for fixing the insulating cap to the bolt is formed on the insulating cap. 6. The gas insulated transformer according to claim 1, wherein a through hole is formed in the insulating cap. 7. The method according to claim 1, wherein the insulating cap is made of a heat-shrinkable plastic.
7. The gas-insulated transformer according to 2, 3, 4, 5, or 6. 8. The method according to claim 1, wherein said insulating cap is made of transparent plastic.
8. The gas-insulated transformer according to 4, 5, 6, or 7.