JPS59211208A - Laminated insulator for oil-immersed electric apparatus - Google Patents

Abstract

PURPOSE:To improve the oil impregnation characteristics and reduce the manufacture period without deteriorating the mechanical strength by a method wherein press-board layers which have high oil permeability are used as intermediate layers and perforated films which have holes with a prescribed interval are used as adhesive layers. CONSTITUTION:A laminated insulator is composed of high density (about 1.25g/ cm<3>) press-boards 1 which have excellent mechanical strength and insulation strength but have a little inferior oil impregnation characteristics and press- boards 2 which have the density a little lower than the press-board 1 (about 0.9-1.1g/cm<3>) and a little inferior mechanical and electrical strength but have excellent oil impregnation characteristics. Those two kinds of boards are laminated alternately and the high density press-boards 1 come to both surfaces. Adhesive layers 5 composed of perforated films are provided between the adhesion surfaces and the laminated boards are solidified under the high temperature and the high pressure by a hot-press machine and the like to form a solid laminated insulator. Round holes 6 of the diameter (d) are provided in the adhesive layer 5 with a certain interval S along the surface direction.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention is applied to oil-filled electrical equipment such as a transformer,
The present invention relates to a laminated insulator for oil-filled electrical appliances that is laminated to have good oil impregnation properties.

In general, insulating structural members such as oil-immersed transformers that require particularly high mechanical strength use laminated insulators made by laminating dozens of layers of electrically insulating press pods several millimeters thick. . In the oil impregnation step for vacuum heating and drying of a transformer, it is desired from the viewpoint of electrical performance that the insulating presspod portions constituting the laminated insulator be completely impregnated with oil. Therefore, laminated insulators are required to have good oil impregnation properties.

[Prior art and its problems]

FIGS. 1 to 3 are structural diagrams of conventional laminated insulators for oil-filled electrical appliances. Conventional laminated insulators, as shown in Figure 1,
An electrically insulating presspod 1 is used as a substrate, an adhesive is applied to the entire surface of the substrate 1, and the whole is heated and pressed to form a laminated structure. That is, the laminated insulator is composed of presspods 1 of a plurality of substrates and an adhesive layer 3 between the substrates 1 and formed of an adhesive. Now, in FIG. 1, the oil impregnation rate that permeates through the adhesive layer 3 is extremely small compared to the oil immersion rate that permeates through the press pad 1 of the substrate, and in general, the oil permeability of the adhesive layer 3 is not as expected. It is something that cannot be done. Moreover, as shown in FIG. 2, the adhesive layer 3 is formed on the entire adhesive surface of the press pad 1 of the substrate and is interposed between the substrates 1, so that the oil immersion direction of the press pad 1 constituting the laminated insulator is It will be limited. In other words, oil immersion in the lamination direction is blocked by the adhesive layer and is limited to the direction parallel to the laminated surface, which has the disadvantage that the oil immersion speed of laminated insulators is slow. There has been a problem in that oil impregnation failures often occur in the central portion away from both the surfaces and the end surfaces, and the insulation properties of the laminated insulator are significantly degraded.

Conventionally, in order to improve oil permeability (oil impregnation), some mechanical properties of the laminated insulation were sacrificed, and as shown in Fig. It had 4 oil holes. In other words, if a large number of oil guide holes 4 are formed that penetrate through the press pads 1 and adhesive layer 3 of the substrate, or if the deterioration of mechanical properties due to the processing of the oil guide holes cannot be tolerated, the laminated insulator is completely oiled. In order to impregnate the transformer, a special method is required to completely impregnate it with oil, such as by significantly extending the oil impregnation time, and this has caused a problem in that the manufacturing process and man-hours for the transformer have increased.

[Purpose of the invention]

The present invention was made in view of the above-mentioned situation, and it can be used without sacrificing the performance as an insulating member or a structural member.
The object of the present invention is to provide a laminated insulator for oil-filled electrical appliances that has excellent oil impregnation properties.

[Key points of the invention]

According to the present invention, the above-mentioned object is achieved by using a breath board having a higher oil permeability than others for at least one intermediate layer of the press boards of the plurality of layers for electrical insulation and wire forming the laminated insulator. By improving the oil permeability of the intermediate layer in the longitudinal direction, and by making the adhesive layer into a membrane with holes in a predetermined pattern, we can improve the oil permeability in the lamination direction or along the laminated plate. This was achieved by arranging press pods with high density and excellent mechanical strength on at least both sides in the lamination direction to prevent a decrease in mechanical strength.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

4 and 5 are perspective views showing the insulation structure of the embodiment of the present invention. In the case of Figure 4, the laminated insulator has a high density and excellent mechanical strength and insulation strength, but is slightly inferior in oil impregnation. Press pods 2 are arranged alternately with press pods 2, which have a slightly lower density (density of about 0.9 to 1.1 gZd) and have slightly lower mechanical strength and insulation strength, but which have good oil impregnation properties, and both surfaces are high-density press pods. The adhesive layer 5 with a large number of holes is interposed on the adhesive surface, and is heated to a high temperature using a hot press machine or the like.

It is formed as an integrated laminated insulator that is laminated and bonded under high pressure.

It also shows a modification of the embodiment shown in Fig. 4, with the fifth opening enlarged.The difference from Fig. 4 is that high-density presspods 1 are arranged at both ends in the stacking direction, and all intermediate layers in the stacking direction are oil-permeable. By arranging large, low-density press pods, oil impregnation in the middle layer, where impregnation is likely to occur, is greatly improved.

The presspod used in the above example is as follows:
Thin wet sheets made from kraft pulp, which is generally made from softwood fibers, are layered together and heated using hot press material.

Paperboard A formed by pressing and drying! However, different densities (or tightness) can be obtained by adjusting the degree of beating and pressing pressure of the fibers. In addition, the press pod called precombrest type press pod has a density of 1.25 g/cr/
It has a high density and excellent mechanical strength. (For the above-mentioned laminated insulator, a material with high density and excellent mechanical strength such as the pre-combreasted press pod mentioned above is used for both fIIl in the lamination direction, and the middle layer is made of a material with high density and excellent mechanical strength. By arranging the boards, etc., with materials that have slightly low density but good oil permeability, it is possible to obtain laminated insulation with good oil permeability without sacrificing mechanical strength such as bending strength. can.

Next, the adhesive layer will be explained. Thermosetting adhesives with excellent heat resistance and oil resistance are suitable as adhesives for forming the adhesive layer, and casein- and starch-based adhesives and synthetic resin-based adhesives such as epoxy, polyester, or phenol resins are suitable. It is broadly divided into adhesives. In addition, the adhesive layer can be formed by applying a predetermined number of turns on the adhesive surface of the press board using a mask, or by forming a perforated film of semi-cured adhesive in advance. There is a method of stacking pressed pressboard and adhesive film alternately and applying heat at a predetermined temperature and pressure to heat-cure and integrate them, and a method of applying adhesive to both sides of a base material such as insulating thin paper and drying it by heating. Another method is to form a semi-cured perforated adhesive sheet (prepreg material), stack it alternately with presspods, apply a predetermined temperature and pressure, heat cure, and integrate. The type and form of the agent can be selected and used.In addition, the use of a prepreg material pre-formed in a predetermined pattern for the adhesive layer has the advantage that the pattern can be easily and reliably formed.

Fig. 6 is a conceptual diagram for explaining the oil impregnation path of the laminated insulator formed as described above. High-density press board, 2 \low density press board, 5
6 is a perforated adhesive layer, 6 is a hole in the perforated adhesive layer 5, and the arrow indicates the direction in which oil permeates. 0 First, the laminated insulator formed as shown in Fig. 6 is vacuumed. Degassed insulating oil is injected in a heated and dry state, and with the insulator submerged in the oil, the oil level is returned to normal pressure or the oil is pressurized to a predetermined pressure.At this time, the interior of the laminated insulator is still a vacuum. Or, since it is in a reduced pressure state, the oil begins to penetrate into the laminated insulation due to the pressure difference with the surrounding oil. Laminated insulation is the route through which oil penetrates.
A path A goes inward from the surface of the high-density press pods 1 arranged on both sides in the stacking direction, and a path A goes in the longitudinal direction from the end surface of the press pods 2, which have a slightly lower density and have good oil impregnation properties, forming an intermediate layer in the stacking direction. There is an impregnation path B.

In this case, although the oil impregnation rate is slow in path A, the oil gradually penetrates from the surface of the high-density press pod, which has a large contact area with oil. On the other hand, in the path B, the surface area in contact with oil is small, but the oil permeates at a high speed, so the oil penetrates in the longitudinal direction of the press pad 2 and the press pad 2 is completely impregnated with oil, and the adhesive layer 5 is completely impregnated with oil. Holes 6a arranged at intervals
*6 The oil also permeates into the high-density press pod 1 through path A, and joins with the oil that has permeated through path A, so that the entire laminated insulator is completely impregnated with oil. In addition, at the final stage of the impregnation process, the pressure difference between the inside and outside of the laminated insulation is almost completely lost, but the few remaining air bubbles are dissolved in the degassed oil and disappear, leaving the laminated insulation The space inside is completely filled with oil. In particular, by interposing a low-density presspod with a high oil absorption capacity in the intermediate layer and communicating with each part of the high-density presspod through a perforated adhesive layer, it is possible to prevent residual oil in the final stage of oil impregnation. Figure 7 is a diagram showing the arrangement of holes in the adhesive layer in the above embodiment.
(A) is a plan view, and (B) is a sectional view taken along line A-A.

In the case of the figure, circular holes 6 having a diameter d are provided in the adhesive layer 5 at predetermined intervals in the surface direction.

From the perspective of oil permeability, the hole size d and the farthest distance between the holes are determined by the volume of the high-density press pod 1 into which oil permeates through the holes 6 and the time required for oil impregnation. In terms of the mechanical strength of the laminate, there is a limit to the bonding area necessary to maintain the mechanical strength.
If the total area of the pores is selected to be about 3 to 30% of the total area of the bonding surface, appropriate oil permeability can be obtained without compromising mechanical strength.In the present invention, presspods with good oil permeability are used. Since this is a permeation path for oil, the holes provided in the adhesive layer can be formed as individual holes, such as circular or rectangular shapes as shown in the figure, and the adhesive layer can be formed into a perforated film or sheet. It has advantageous conditions when it is formed in advance. Note that the pores in the adhesive layer may be formed in a striped shape that communicates with each other, and it is obvious that this will further improve the oil permeability. This is determined by taking into consideration that the adhesive will flow to some extent during curing and the diameter of the pores will become smaller.

〔Effect of the invention〕

According to the present invention, a presspod layer with high oil permeability (low density) is provided in the intermediate layer in the lamination direction of a laminated insulator consisting of multiple layers of electrically insulating presspods, and oil impregnation in the longitudinal direction of the laminated insulator is provided. In addition to improving the properties, the adhesive layer is formed into a perforated membrane with holes at predetermined intervals to improve oil impregnation in the lamination direction. To provide a laminated insulator for oil-filled electrical appliances that eliminates the need for a large number of oil guide holes that are provided so as to penetrate the insulator in the lamination direction, and has excellent oil impregnation characteristics without impairing insulation characteristics and mechanical strength. was completed. In addition, the time required for machining to drill holes for introducing oil is reduced by 20 to 50 cm, and the manufacturing period for oil-filled electrical appliances using this material can be shortened by 7'C.

[Brief explanation of the drawing]

Figures 1 and 2 are perspective views of conventional laminated insulators, Figure 3
The figure is a diagram showing a conventional method for improving oil impregnation, and FIGS. 4 and 5 are perspective views of a laminated insulator showing an embodiment of the present invention.
FIG. 6 is a sectional view for explaining the oil impregnation path, and FIG. 7 is a conceptual diagram showing the shape of the adhesive layer. In the figure, 1...a small oil-permeable press pod (
High-density presspod), 2... Presspod with high oil permeability (low-density presspod), 5... Adhesive layer, 6
...These are holes in the adhesive layer. Figure 1 3 Figure 2 Figure 8 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1) A plurality of electrically insulating press pods having different oil permeability based on the difference in fiber density are laminated and bonded together,
An insulator that is used impregnated with electrical insulating oil, in which at least two types of press pods having different oil permeability are laminated with the press pod having a high oil permeability arranged on the inside in the lamination direction, and each of the press pods A laminated insulator for an oil-filled electrical appliance, characterized in that the layers are bonded to each other by an adhesive layer having holes arranged at predetermined intervals on the laminated surface, and the press pod is integrated. 2. In the product described in claim 1, the density of the electrically insulating presspod with low oil permeability is 1.1 compared to the density of the electrically insulating presspod with high oil permeability.
A laminated insulator for oil-filled electrical equipment characterized by having a size more than twice as large. 3) In the product described in claim 1 or 2, the laminated insulator is composed of an odd number of electrically insulating presspods, and the presspods with different oil permeability are alternately adjacent to each other on the inside in the lamination direction. A laminated insulator for oil-filled electrical appliances, characterized by the fact that: 4) The oil-filled product according to any one of claims 1 to 3, characterized in that a plurality of press pods with high oil permeability are arranged adjacent to each other inside in the lamination direction. Laminated insulator for electrical appliances 0 5) In the product described in claims 1 to 4, the adhesive layer is made of a prepreg insulating material pre-formed to have a predetermined pattern of through holes, and A laminated insulator for oil-filled electrical appliances, characterized in that the presspod is integrated by interposing the prepreg insulating material between the layers and then heating and curing the adhesive layer while applying a predetermined surface pressure.