JPH09172725A - Structure of oil-impregnated terminal for plastic cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide structure of an oil-impregnated terminal for a plastic cable, which can maintain insulating performance even at a high temperature. SOLUTION: In an oil-impregnated terminal for a plastic cable, a plastic laminate paper constituting an oil-impregnated insulating material 16A is formed of a plastic film and a kraft paper applied to the plastic film. The kraft paper is made into a multilayered paper comprising a paper of two or more layers, and the air resistance of the layer on the side of being in contact with the plastic film of those layers is made not more than 20 Gurley seconds, and the density of the layer on the side of being exposed in the surface is made not less than 0.7g/cm<3> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an oil-immersed terminal used for a terminal portion of a plastic cable such as a cross-linked polyethylene insulated power cable, and more particularly to a structure having improved insulation reliability.

[0002]

2. Description of the Related Art As an oil-immersed terminal used at the end of a plastic cable such as a cross-linked polyethylene insulated power cable, the one shown in FIG. In the figure, reference numeral 10 is an oil immersion terminal, and reference numeral 12 is a plastic cable. Around the end of the plastic cable 12, a plastic laminated paper 16 impregnated with an insulating oil such as silicone oil is wound many times to form the oil-immersed insulator 1.
6A are formed. A cylindrical condenser cone 1 made of aluminum or the like is provided around the oil-immersed insulator 16A.
8 is attached to the condenser cone 18, and a fitting-equipped insulator tube 22 is provided on the outer periphery of the condenser cone 18. Silicone oil 2 is provided between the condenser cone 18 and the fitting-equipped insulator tube 22.
0 is filled. Above these, the oil-immersed insulation 1
An oil amount compensator 24 for replenishing 6A with insulating oil and a conductor pull-out rod 26 are provided.

In the oil-immersed terminal 10 constructed as described above, the plastic-laminated paper 16 forming the oil-insulated insulator 16A has a kraft paper 31 attached to a polyolefin plastic film 32 as shown in FIG. It has a combined structure. Further, the kraft paper is provided with a plurality of linear slits (not shown) in consideration of ease of winding and stretchability.

The production of such a plastic laminated paper is carried out by extruding a molten plastic film from a T-type die of an extruder and at the same time kraft paper along the film in a molten state, press-bonding with a roll, and then cooling and winding. Is done by. Therefore, the plastic film of the plastic laminated paper and the kraft paper are bonded to each other by the anchor effect in which the molten plastic is embedded in the fine irregularities on the surface of the kraft paper.

If the adhesive strength between the plastic film and kraft paper is not sufficient, the kraft paper may peel off from the plastic film. In this case, when the oil-immersed terminal employing this kraft paper becomes high temperature, the plastic cable in the oil-immersed terminal is thermally expanded, so that tensile force is applied to the peeled kraft paper,
The kraft paper may be damaged by tearing from the slit. In such a case, the insulation performance of the oil-immersed terminal using this kraft paper will deteriorate.

[0006] In order to avoid this, it is conceivable to interpose an adhesive at the interface between the plastic film of the plastic laminated paper and the kraft paper to enhance the adhesive strength, but the adhesive is generally a substance having a polar group. For,
It cannot be used because it causes deterioration of dielectric properties, especially dielectric loss tangent. For this reason, it is necessary to take measures to increase the adhesive strength between the plastic film and the kraft paper without using an adhesive.

As a measure for this, it is conceivable to enhance the anchor effect to enhance the adhesive strength, and for this purpose, it is conceivable to use kraft paper having a low airtightness. Since kraft paper with low airtightness has large irregularities on the surface, the degree of embedding of the resin at the time of bonding increases, the anchor effect increases, and the bonding strength increases.

However, kraft paper having a low airtightness generally has a low density. Kraft papers with low density usually have low tensile strength. For this reason, the oil-immersed end of the plastic cable using the plastic laminated paper using such kraft paper has a high temperature, particularly a temperature of 80 ° C or higher, due to the heat of lead work at the time of connection and the heat generated by energization. When exposed to water, the plastic laminated paper may be subjected to tensile force due to thermal expansion of the plastic cable in the oil-immersed terminal, and may be damaged such as tearing. This may reduce the insulation performance of the oil-immersed terminal.

[0009]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a structure of an oil-immersed terminal of a plastic cable capable of maintaining good insulation performance even at high temperatures.

[0010]

The structure of the oil-immersed terminal of the plastic cable of the present invention is a multi-layered paper made of two or more layers of kraft paper constituting the plastic laminated paper, and the plastic film among these layers. It is characterized in that the airtightness of the layer on the side in contact with is set to 20 Gurley seconds or less and the density of the layer on the surface exposed side is set to 0.7 g / cm ³ or more. Further, it is preferable to use a film made of polypropylene homopolymer as the plastic film from the viewpoint of insulation performance.

[0011]

FIG. 2 shows an example of a plastic laminated paper used as an oil-immersed insulator having an oil-immersed terminal structure according to the present invention. Reference numeral 1 in the drawing denotes two layers 1a and 1a.
It is a double kraft paper consisting of b, and reference numeral 2 is a plastic film. The double kraft paper 1 is integrally attached to one surface of the plastic film 2 to form the plastic laminated paper 3. Double kraft paper 1
The airtightness of the first layer 1a is set to 20 Gursec or less. If the airtightness exceeds 20 Gursec, the adhesiveness to the plastic film will be poor and the kraft paper will be easily peeled off. The density of the second layer 1b is 0.7 g / c.
It is the m ³ or more, the density of less than 0.7 g / cm ^3, and reduced tensile strength when formed into a oil immersion insulation, easily damaged.

The thickness of the double kraft paper 1 is not particularly limited, but is usually in the range of 20 to 100 μm,
The thickness of the first layer 1a is at least 5 μm or more, preferably 5 to 30 μm. On the other hand, the thickness of the second layer 1b is at least 15 μm or more, preferably 15 to 70 μm. When the thickness of the first layer 1a is less than 5 μm, sufficient adhesive strength with the plastic film cannot be obtained, and when the thickness of the second layer 1b is less than 15 μm, the tensile strength is insufficient.

Further, the ratio of the thickness of the first layer 1a and the second layer 1b to the total thickness of the double kraft paper 1 is the first
It is advantageous that the ratio of the layer 1a is small. This is because the region relating to the adhesiveness is a relatively thin part of the surface, and if the unevenness of the surface of this part is large, sufficient adhesive strength can be obtained, and the second layer 1b is thicker. Because the tensile strength is improved. The double kraft paper 1 is preferably deionized water-washed low-loss paper having good dielectric properties, and has a low conductivity of water immersion liquid conductivity (according to JIS-C-2111) of 15 μS / cm or less. Is preferred. Such a double kraft paper 1 is manufactured by a method of stacking pulp having different degrees of fibrillation of paper fibers in two stages when making paper with a Fourdrinier or round net paper machine.

Then, the first layer 1a of the double kraft paper 1
Is in contact with the plastic film 2, and the second layer 1b is assembled so as to be exposed on the surface and bonded to the plastic film 2.

The plastic film 2 is made of polypropylene, poly-4-methylpentene-1, polybutene-
1. Non-polar polyolefin such as polyethylene, fluorocarbon resin such as tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer and the like, having a thickness of 20 to 150 μm. Among these plastics, polypropylene homopolymer, preferably having a melt index of 5 to 5
A film made of polypropylene homopolymer having a relatively low melt viscosity of 0 g / 10 minutes has high adhesiveness with the double kraft paper 1, and the resulting laminated paper has good insulating properties, which is preferable.

For laminating the plastic film 2 and the double kraft paper 1, the molten film is extruded from the T-shaped die of the extruder, and the double kraft paper 1 is placed on the film 2 when the film is in a molten state. It is manufactured by a so-called extrusion laminating method in which pressure is applied by a pressure roll. The total thickness of such plastic laminated paper is 1
The range is from 00 to 300 μm, but may be outside this range depending on the application.

In the plastic laminated paper 3 having such a structure, since the first layer on the plastic film 2 side of the double kraft paper 1 laminated on the plastic film 2 has a low airtightness, it is porous. The unevenness of the surface becomes large, and when it is bonded to a plastic film, the melted plastic penetrates better into the paper and the adhesive strength is improved. Further, since the second layer on the front surface side of the double kraft paper 1 has a high density, the plastic laminated paper 3 has high tensile strength and elongation.

The kraft paper may be a multi-layered kraft paper having three or more layers. In this case as well, the airtightness of the layer in contact with the plastic film is 20 Gursec or less, and the density of the layer on the surface side is 0.7 g / It may be cm ³ or more. In this case, the intermediate layer preferably has a high density of 0.7 g / cm ³ or more in terms of tensile strength and elongation.

In the oil-immersed terminal having the structure shown in FIG. 1 in which the oil-impregnated insulator is formed by using such plastic laminated paper, the adhesive strength between the kraft paper and the plastic film forming the plastic laminated paper is high.
These peelings are unlikely to occur. Further, since the kraft paper has high tensile strength and elongation, even if the plastic cable in the terminal is thermally expanded at high temperature, the plastic laminated paper withstands the tensile tension and is not damaged. Therefore, this oil-immersed terminal can maintain the insulating performance at a higher temperature.

Hereinafter, a concrete example will be shown to clarify the action and effect. (Test Example) A polypropylene having a melt index of 15.0 g / 10 minutes and a density of 0.90 g / cm ³ was heated at 280 ° C.
Was melt-extruded into a polypropylene film, and while it was in a molten state, a kraft paper having a thickness of 70 μm was placed along the roll and pressure-bonded to produce a polypropylene laminated paper having a total thickness of 130 μm. As the kraft paper, a normal single layer paper having a thickness of 70 μm and a first layer having a thickness of 20 are used.
A double-layered paper was used in which two sheets of paper having a thickness of 2 μm and a thickness of the second layer of 50 μm were laminated. The double kraft paper used was one having a water immersion liquid conductivity of 5 μS / cm according to JIS-C-2111, which was washed with deionized water. The first layer was on the polypropylene film side and the second layer was on the surface side. I turned to.

This polypropylene laminated paper is used for 10
After being immersed in 0 ° C. insulating oil (JIS-C-2320-1993, 6 kinds of silicone oil) for 24 hours, the adhesive strength (1) of the interface between the polypropylene film and the double kraft paper
The 80 degree peel test) was measured. Moreover, the tensile strength (JIS-C-2111) of this polypropylene laminated paper was measured. Table 1 shows the results.

[0022]

[Table 1]

From the results shown in Table 1, the kraft paper was a double paper consisting of two kinds of paper, the airtightness of the first layer was 20 Gare seconds or less, and the density of the second layer was 0.7 g / cm. ^It can be seen that the test Nos. 3, 4, and 5 of ³ or more have good tensile strength and adhesive strength.

Taking the above experimental results into consideration, an oil-immersed terminal of a plastic cable having the structure shown in FIG.
When placed at 100 ° C., the insulation performance of the conventional product was extremely deteriorated, while the insulation performance of this example was kept good.

[0025]

As described above, in the structure of the oil-immersed end of the plastic cable of the present invention, the plastic laminated paper forming the oil-insulated insulator has high tensile strength. Further, this plastic laminated paper has high adhesive strength between the plastic film and the kraft paper. Therefore, the insulation performance can be maintained at a higher temperature. Also, it can withstand use for a longer period of time.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the structure of an oil immersion terminal of a plastic cable of the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of a plastic laminated paper used for the oil-immersed terminal shown in FIG.

FIG. 3 is a schematic sectional view showing an example of a plastic laminated paper used for a conventional oil-immersed terminal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Double kraft paper, 1a ... 1st layer, 1b ... 2nd layer, 2 ... Plastic film, 3 ... Plastic laminated paper, 10 ... Oil immersion terminal, 12 ... Plastic cable, 16A ... Oil-insulated insulators

Claims (1)

[Claims] 1. An oil-immersed insulator formed by winding a plastic laminate paper impregnated with insulating oil is provided around the outer periphery of a terminal end of a plastic cable, wherein the plastic laminate paper comprises a plastic film and the plastic film. This kraft paper is a multi-layered paper composed of two or more layers of paper, and the airtightness of the layer on the side in contact with the plastic film is 20 Gurley. The structure of the oil-immersed end of the plastic cable, which is less than a second and the density of the layer exposed on the surface is 0.7 g / cm ³ or more.