JPS63298924A - Resin mould bushing - Google Patents

Abstract

PURPOSE:To improve the anti-cracking property and the airtightness-resisting property by furnishing the first layer consisting of a silicon rubber type adhesive on a central conductor and the second layer consisting of a heat-contracting material over the first layer, and heating. CONSTITUTION:The first layer 11 of a silicon rubber type adhesive tape furnished close to a central conductor 1 keeps the condition of a putty with no flowing-out even under a high temperature at 150 deg.C or more, and does hot lose the rubber elasticity even under a low temperature ambiance at -50 deg.C. As a result, a stress generated by the difference of the thermal expansion rate between the central conductor 1 and a pouring pattern layer 3 in a rapid heating and a rapid cooling can be relaxed sufficiently. Moreover, the first layer 11 contacts closely to the central conductor 1 and to the second layer 12 by the thermal contraction of the second layer 12 owing to its thermal contraction tape, maintaining the airtightness perfectly. Since the second layer 12 with the thermal contraction tape contacts rigidly to the whole body of the pouring pattern resin layer 3 by the chromic acid mixture solution treatment, the airtightness-resisting property is improved, and the anti-cracking property is secured generating no stress concentration on the pouring pattern resin layer 3.

Description

Detailed Description of the Invention (Objective of the Invention) (Industrial Field of Application) The present invention is a device that is installed in electrical equipment that uses insulating oil or gas, such as an oil-immersed transformer, and that requires airtight maintenance. The present invention relates to a resin molded bushing.

(Prior technology) Cast insulation has both electrical insulation and structural functions, and can produce products with more complex shapes without voids than other molding methods, making it an ideal choice for solid insulation for high-voltage equipment. Widely used in various fields.

In addition, recent electrical equipment is desired to have a larger capacity, to be smaller, and to thereby reduce the installation space and total cost, and the parts used are also required to be high-value-added and compact.

For this reason, various electrical devices are forced to use a combination of solid insulation with silicone oil, fluorocarbon liquid, or petroleum-based insulating oil, or a combination of insulating gas such as sulfur hexafluoride or fluorocarbon gas with solid insulation. ing.

For this reason, the various parts used are required to be airtight against insulating oil and gas, and the conditions of use are becoming increasingly severe.

For example, a transformer for a train uses a combination of petroleum-based insulating oil and an epoxy cast bushing as a resin molded bushing, and is installed outside, such as under the floor of a car body.

When a train is in operation, it is exposed to high temperatures of 100°C or more due to heat generated by coils, etc., and when it is stopped, especially in the harsh winter months, it is exposed to low temperatures of -20°C or less. Needless to say, if cracks occur in the cast resin of the epoxy cast bushing due to the repetition of such severe cooling and heating cycles, a serious accident may occur.

Therefore, the conventional epoxy cast bushing has a stress relaxation layer 2 between the center conductor 1 and the cast resin layer 3, as shown in FIG.
is provided, and the center conductor 1 is provided to provide airtightness.
A partition wall 4 made of a circular copper plate is soldered to the middle part of the wall, and only this part is firmly bonded to the casting resin layer 3 to maintain airtightness.

For the stress relaxation layer 2, flexible epoxy resins, polyurethane resins, and the like, whose cured products have rubber-like properties, have been used.

Note that in the same figure, the symbol @5 indicates a filler metal having a screw hole into which the mounting screw of the epoxy cast bushing is screwed, and the symbol 6 indicates a groove for a packing.

(Problems to be Solved by the Invention) However, the stress relaxation layer 2 made of flexible epoxy resin or polyurethane resin exhibits a rubber-like appearance in the range from room temperature to high temperature.
Although it fully plays its role as a stress relaxation layer, for example, -
In the low temperature range of 20°C and -30'C, the elastic modulus increases, the rubber-like properties disappear, and it becomes brittle and cannot be expected to have properties as a stress relaxation layer, so cracks may occur earlier than the casting resin layer 3. .

In addition, in order to maintain airtightness, a part of the center conductor 1 (the attachment part of the partition wall 4) is treated so that it firmly adheres to the casting resin layer 3. At the boundary with the stress relaxation layer 2, the liquid casting material hardens by reaction,
This is the part where residual strain is generated due to volumetric contraction when solidified, and is the part where stress concentration is most likely to occur due to the above-mentioned cooling/heating cycle, which can trigger cracks.

The partition wall 4 is determined by complex stress calculations and electric field calculations in order to have a shape that does not adversely affect the cast resin layer 3 and is less likely to cause electrical field concentration, so there are no processing or changes to the central conductor 1. Considerable ingenuity was required in the mounting position, mounting method, etc., leading to an increase in costs. Rather, when viewed from the epoxy cast bushing, the partition wall 4 is unnecessary, and its characteristics are better without it.

An object of the present invention is to provide a resin molded bushing with excellent crack resistance and airtightness.

[Structure of the invention]

(Means and effects for solving the problem) The present invention provides a resin molded bushing in which a stress relaxation layer is interposed between a center conductor and a cast resin layer, in which a first layer made of a silicone rubber adhesive is applied to the center conductor. A second layer made of a heat shrinkable material is provided on top of the first layer and heated to form a stress relaxation layer, which has sufficient airtightness even when used in harsh environments. It is made to have crack resistance.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. Note that the same parts as in FIG. 2 are denoted by the same reference numerals, and redundant explanation will be omitted. FIG. 1 is a sectional view of an embodiment of the present invention. The epoxy cast bushing is applied to the center conductor 1 with a thickness of approximately 0.0 mm.
5m silicone rubber adhesive tape (product of Raychem Co., Ltd., product number 31085-1-900)
The first layer 11 is wound in a lap and becomes the main part of the stress relaxation layer.
A cross-linked polyolefin heat-shrinkable tape (Pennnit Co., Ltd.'s product name Insuru Tape) is wound on top of this first layer 11 with a 1/2 wrap to form a second layer 12. Heat shrinkage is performed under the following conditions to form the stress relaxation layer 13. Stress relaxation layer 1 obtained in this way
3, the surface is treated with an organic solvent and a chromic acid mixture (a mixture of sodium dichromate, water, and @acid) to improve adhesion to the casting resin H3.

After this treatment, it is assembled into a mold and preheated under predetermined conditions. After this, a bisphenol A type epoxy resin, a trianhydride curing agent, and a large amount of silica powder as an auxiliary material are added.
Further, casting is performed using an epoxy resin casting material mixed with tertiary amino as a curing accelerator, and the material is cured under predetermined curing conditions.

In addition, the present inventors used such a method to obtain a material with a diameter of approximately 1.
00IrunX An epoxy cast bushing with a length of 500 m was manufactured.

Next, the characteristics of the epoxy cast bushing produced as described above will be explained.

The first layer 11 made of silicone rubber adhesive tape adjacent to the center conductor 1 maintains a putty-like shape even at high temperatures of 150°C or higher, does not flow out, and does not lose its rubber elasticity even in a low-temperature atmosphere of -50°C. The stress generated due to the difference in thermal expansion coefficient between the center conductor 1 and the cast resin layer 3 during heating and rapid cooling can be sufficiently alleviated. In addition, the first layer 11 made of silicone rubber adhesive tape is heated by heat shrinking of the second layer 12 made of heat shrinkable tape, and the center conductor 1 and the second layer 11 made of heat shrinkable tape are bonded together.
It is completely airtight. The second layer 12 made of heat-shrinkable tape is formed by the casting resin layer 3 by treatment with a chromic acid mixture.
Since it is firmly adhered to the whole body, airtightness is increased, and an epoxy cast bushing with excellent crack resistance without stress concentration on the cast resin layer 3 is obtained. The following table shows the epoxy cast bushings made by the conventional method and the epoxy cast bushings according to an embodiment of the present invention, before testing, immersed in hot water at 98°C to 100'C for 1 hour, and immersed in cold water at 0°C to 2°C for 1 hour. The results of a visual inspection of the presence of cracks and an airtightness inspection using a helium detector after conducting a thermal cycle test in which 1 cycle of immersion was repeated for 10 cycles are shown. The epoxy cast bushing used in the example had a pressure of 1O-7torr, 11/
sec, but as shown in the table, there was no abnormality in appearance even after repeated cooling and heating cycles, and the present invention provided a product that satisfactorily satisfies the above-mentioned airtightness.

〔Effect of the invention〕

Since the present invention is configured as described above, the first layer is made of a silicone rubber adhesive and the second layer is made of a heat shrinkable tape.
By forming a stress-relaxing layer, Utsugi 1 has excellent airtightness. Moreover, a resin molded bushing that does not crack even under severe heating and cooling cycles can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional epoxy cast bushing. 1... Center conductor, 3... Casting resin layer 11...
・First layer, 12...Second layer 13...Stress relaxation layer (8733) Agent Patent attorney Yoshiaki Inomata (1 idiot) Figure 2

Claims (1)

[Claims] In a resin molded bushing in which a stress relaxation layer is interposed between a center conductor and a cast resin layer, a first layer made of a silicone rubber adhesive is provided on the center conductor, and a heat-shrinkable material is applied on the first layer. A resin molded bushing, characterized in that the stress relaxation layer is formed by providing a second layer and heating it.