JPS5812962B2 - Aburaganshin cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oil-impregnated cable mainly composed of a three-component mixed paper consisting of kraft pulp, polypropylene pulp, and polypropylene fibers (hereinafter referred to as three-component polypropylene mixed paper) and an insulator. This is intended to provide an ultra-super high voltage oil-impregnated cable with low dielectric loss and high withstand voltage value by sequentially winding three-component polypropylene mixed papers with different mixing ratios and paper thicknesses onto a conductor. It is.

Traditionally, electricity transportation in urbanized areas has been carried out using underground cables for reasons of safety and aesthetics.
In recent years, the demand for electricity in cities has increased rapidly due to the concentration of entrances to cities, and for this reason, it is desired to increase the capacity of underground cables.

However, with conventional cables insulated with kraft paper and hydrocarbon oil, due to the large dielectric loss of the kraft paper, increasing the transmission voltage significantly increases power loss during power transmission, so it is difficult to increase the transmission voltage beyond a certain level. It is not possible to transmit large amounts of electricity.

For this reason, the development of electrically insulating paper to replace kraft paper is progressing, and for example, synthetic paper, which has a paper-like structure similar to kraft paper, is being intensively researched from the viewpoint that unlike film, it is easier to form oil channels. .

A typical example of such synthetic paper is Tenax paper (manufactured by AKZO in the Netherlands, paper made of poly-2,6-diphenyl-1,4-phenylene oxide).
, polypropylene paper, etc., but the former is very expensive and the latter swells in hydrocarbon oil.
There is no commercial use for underground cables.

On the other hand, in addition to the synthetic paper made of a single polymer as described above, attempts have also been made to economically produce electrically insulating paper with low dielectric loss by mixing kraft pulp and polymer.

For example, mixed paper with polyolefin fiber as seen in Japanese Patent Publication No. 38-8421 or Japanese Patent Publication No. 38-19230.
However, since the Lahoriolefin fiber or polyolefin powder has a weak bond with the kraft pulp, it is not possible to make a homogeneous mixed paper, resulting in good electrical properties, Electrical insulating paper that gives mechanical properties cannot be blown.

However, the present inventors have eliminated the drawbacks of the conventional electrically insulating paper as described above, and have created a paper that is of homogeneous quality and has high airtightness.
As a result of various research efforts to create an electrical insulating paper that has mechanical properties suitable for cable tape wrapping, shows good dielectric loss in hydrocarbon oil, and does not swell in expensive insulating oil,
It has been found that a three-component polypropylene mixed paper consisting of three components of kraft pulp, polypropylene bulk and polypropylene fibers and within a specific mixing ratio range achieves the above object.

A cable made by winding a single composition of ternary polypropylene mixed paper with different paper thicknesses and impregnating it with oil using the usual method for paper cables gives good performance results in itself; The inventors of the present invention further conducted various studies on the optimal insulation structure for cables, and as a result, they developed a cable with lower dielectric loss and higher withstand voltage value than cables made of polypropylene mixed paper of a single composition. We discovered that there is a method for configuring special cable insulation so that the withstand voltage value does not decrease even after heating and bending, and we were able to complete the present invention.

That is, the present invention consists of (1) kraft pulp, (11) polypropylene pulp, and (110 polypropylene fiber), and the mixing ratio of the above (1) to (iii) is at point a, point b, and point C of the triangular coordinates shown in FIG. Electrical insulating paper made of fibrous material with a thickness of 70 to 125 μm is wound on the conductor shielding layer to a thickness of 10 to 50% of the total insulation thickness within the area connected by straight lines. The remaining insulation thickness is the above (l)
~ (iii), and their mixing ratio is an area connecting points b, C, d, and e of the triangular coordinates shown in Figure 1 with a straight line (however, the component on the line between points b and C An oil-impregnated product characterized by being made by winding a tape of electrically insulating paper with a thickness of 125 to 250 μm consisting of a fibrous material (excluding polypropylene) or electrically insulating paper made only of polypropylene with a thickness of 125 to 250 μm. This is a proposal for cables.

That is, in the present invention, the insulation structure of the cable is optimized by limiting the mixing ratio and paper thickness of the electrically insulating paper tapes wound on the cable conductor, as well as defining the winding order and winding ratio of those tapes. By using this method, even if the paper used for the upper layer swells a little, there is no change in the overall performance of the cable, and because it allows some swelling, it is possible to increase the range of oils that can be impregnated. Moreover, a cable with low dielectric loss and high withstand voltage value can be obtained.

The graft pulp used for the electrically insulating paper of the present invention is J
Any kraft pulp of a quality capable of producing insulating paper for power cables as defined in IS C2307 may be suitably used, but one that has been thoroughly washed with deionized water is particularly preferred.

The polypropylene fibers used are those produced by methods such as melt spinning or splitting of stretched films that involve ordinary drawing treatment, and cut fibers that are usually cut into fibers with a thickness of 10 to 30 μm and a total length of 2 to 15 mm are used. Preferably used.

Such products include Baylene fiber (manufactured by Mitsubishi Rayon ■), but the resin before spinning or the fiber after spinning is washed with a solvent such as a lower alcohol, ketone, ether, or aromatic hydrocarbon, or with deionized water. It is preferable to remove impurities as much as possible.

The polypropylene bulk used in the present invention is a fine fibrillated fiber of polypropylene, which is usually thinner than the above-mentioned polypropylene fiber and has a thickness of about 1 μm or more, and has a length of 0.
．． A thickness of about 1 to 5 mm is preferably used.

However, levers are usually made by heating a solution of polypropylene in a low boiling point solvent such as methylene chloride in a tank with a nozzle and blowing it out using its own pressure, or by blowing out a melt of polypropylene from a nozzle using centrifugal force. manufactured by the method.

Particularly preferred is polypropylene with hydrophilic groups such as hydroxyl groups and carboxylic acid groups bonded to it, which is made into a bulge by the method described above, and its excellent dispersibility in water can be used to make paper more uniform. Therefore, a homogeneous mixed paper can be obtained.

An example of such a polypropylene bulb is SWP (manufactured by Mitsui Zella Pack ■).

The electrical insulating paper made of three-component polypropylene paper according to the present invention is produced by dispersing the above-mentioned three-component fibrous materials in deionized water or water containing a dispersant such as polyethylene oxide at the above-mentioned mixing ratio. can be obtained easily.

Furthermore, the electrical insulating paper made only of polypropylene according to the present invention is produced by wet paper making, dry paper making, or spunbonding of polypropylene fibers or pulp, but particularly preferred is one from which impurities have been sufficiently removed, For example, there is polypropylene paper made by the spunpond method manufactured by Exxon Corporation in the United States.

It is preferable to improve the airtightness of these electrically insulating papers by ordinary hot calendering or supercalendering, and it is preferable to remove impurities by washing in a solvent in an appropriate step after papermaking.

In the present invention, paper is used that has a mixed paper ratio within the area connecting the points a, d, and e of the triangular coordinates shown in Fig. 1 with straight lines.The reason why the mixed paper ratio was determined in this area is that ab
This is because in the area to the left of the line e, even if hot calendering is performed to improve the airtightness of the paper, control at that time will be difficult and the paper will lack uniformity, while in the area to the right of the straight line acd. This is because it becomes impossible to obtain sufficient mechanical strength for use in cables, and furthermore, in the region below the straight line ed, swelling in insulating oil becomes large, so that it cannot be used as a cable insulation layer.

The further away from the coordinate axis of the triangular coordinates, the better the properties of the obtained paper become.
0.5, 0.5), b'(5.5, 3.3
, 1. 2) and c' (5.5, 1.2,
3.3) is connected by a straight line, and instead of the area bcde, b'', c', d' (2, 2, 6)
, and e' (2, 6, 2) with a straight line.

In the present invention, the thickness is 70 to 1, which corresponds to the paper mixing ratio of the area connecting the point a, point b, and point C of the triangular coordinates shown in FIG. 1 with a straight line.
Add 25μ paper to the inner layer of the cable with a total insulation thickness of 10 to 50
% thickness is because there is a risk that swelling in oil will increase in the area below the straight line bc and the withstand pressure value during heating and bending will decrease, especially when used in the inner layer, and the thickness is less than 70μ. However, when wrapping paper around the cable, paper breaks or registration disturbances occur, making control difficult.
If these papers are used on the conductor shielding layer, sufficient voltage resistance cannot be obtained, and if these papers are used for the inner layer part of the cable, which accounts for less than 10% of the total insulation thickness, the This is because it is difficult to effectively insulate areas with high electrical stress, and if it exceeds 40%, the number of turns of paper tape increases, which is disadvantageous in terms of tape winding efficiency, and the paper tape in this area occupies the entire cable. This is because the dielectric loss of the cable increases as the ratio increases.

Next, in the present invention, paper with a thickness of 125 to 250μ or a paper with a thickness of 125 to 250μ that corresponds to the paper mixing ratio of the area connecting points b, C, d, and e of the triangular coordinates shown in FIG.
The reason why paper made only of polypropylene is wrapped around the outer layer of the cable to a thickness of 50 to 90% of the total insulation thickness is that the area above the straight line bc is insufficient to obtain a sufficiently low dielectric loss. With tapes of 50 of
If less than 90% is used for the outer layer, it will be disadvantageous in terms of winding efficiency and the dielectric loss of the cable cannot be lowered. If it exceeds 90%, the swelling of the entire cable will increase and the withstand voltage after heating and bending will decrease. This is because there is a significant decrease in

Hereinafter, the present invention will be explained with reference to FIG. 2. In the drawing, M is a hollow conductor having an oil passage in the center, N is a conductor shielding layer, and L is an insulator shielding layer. These shielding layers include carbon paper and metallized paper. etc. are used, and S is a metal sheath.

Insulators A and B are located between the two shielding layers, A corresponds to the inner layer, and has a mixing ratio of 70 to 70, which is the composition ratio surrounded by the three points a, b, and c in Figure 1. Consisting of 125μ single or multiple types of paper tape, 10-50% of the total insulation thickness
B is the part that occupies the thickness, while B is the part b, cd, and
12 with a mixed paper ratio within the range surrounded by the straight line connecting e.
It consists of a single or multiple paper tape of 5 to 250 microns or a paper tape of 125 to 250 microns made of polypropylene only, and accounts for 50 to 90% of the total insulation thickness.

All systems inside the metal sheath are vacuum impregnated with electrical insulating oil,
An example of the oil used here is Futukol OF Cable Oil (11 cst) manufactured by Fuji Kosan.
) (same below kinematic viscosity at 100°F),
Mineral oil-based insulating oils such as OF cable oil (10 cst) manufactured by Nippon Oil Co., Ltd. and Sonic OF cable oil (8 cst) manufactured by Nippon Mining Co., Ltd., hard type alkylbenzene SI-102 (7 cst) manufactured by Mitsubishi Yuka Co., Ltd. Soft type alkylbenzene≠246 (4.5 cst) manufactured by the company. Alkylbenzenes such as EHV cable oil (8.6 cst) manufactured by Nippon Oil, polybutene LV-10E manufactured by Nippon Petrochemical (
23cst), i, V-5 0 E (1 20
cst) Polybutenes such as HV-15g (780cst) and mixtures thereof (hereinafter referred to as hydrocarbon insulating oil)
In addition, silicone oil such as Shin-Etsu Chemical KF96 (25cst), Dainippon Ink Megafac F220 (2cs)
Diphenyl ether derivatives (2 to 100 cst) in which at least one hydrogen bonded to the phenyl group of diphenyl ether is substituted with an alkyl group
) and other ether oils.

Among the above, hydrocarbon insulating oils and ether oils are particularly preferred for application to the present invention due to their characteristics.

Next, the effectiveness of the present invention will be explained with reference to Examples.

In all Examples and Comparative Examples, the conductor size was 1200 mm' and the insulation thickness was 30 mm, and the impregnating oil was alkylbenzene (see Note 5).

The composition and main properties of the ternary polypropylene mixed paper used in these examples are shown in Table 1.

Example 1 In the above (see Figure 2), the inner layer A of the cable insulator was wound with paper types SX-1 and SX-2 shown in Table 1 by 15% and 15% of the total insulation thickness, respectively, and then The outer layer B is 3 of the total insulation thickness for the paper types SY-1 and SY-2 shown in Table 1, respectively.
It was formed by winding 5% and 35%.

Example 2 In the above (see Figure 2), the inner layer part A of the insulator is
The paper type SX-3 shown in the table is wound to 12% of the total insulation thickness, and the outer layer B is wound to 30% and 58% of the total insulation thickness with the paper types SY-3 and SY-4 shown in Table 1, respectively. It was formed by

Example 3 In the above (see Figure 2), the inner layer part A of the insulator was wound with the paper types SX-4 and SX-5, which are shown in Table 1, by 8% and 22% of the total insulation thickness, respectively, and the outer layer part B was Paper type SY shown in Table 1
-5 and was formed by winding 70% of the total insulation thickness.

Comparative Example 1 Insulators were formed by sequentially winding SY-6, SY-7, and SY-4 at 15%, 30%, and 55% of the total insulation thickness, respectively.

Comparative Example 2 Insulators were formed by sequentially winding SX-4, SX-6, S, and X-7 to 8%, 22%, and 70% of the total insulation thickness, respectively.

Comparative Example 3 Insulators were formed by sequentially winding SX-4, SX-5, and SY-5 to a thickness of 22%, 44%, and 34% of the total insulation thickness, respectively.

Comparative Example 4 Insulators were formed by sequentially winding SX-3, SY-3, and SY-4 to 6%, 30%, and 64% of the total insulation thickness, respectively.

Table 2 shows the results of the dielectric loss measurement (Note 8) conducted on the above cable at 80°C and the results of the impact breakdown voltage test (Note 10) before and after the heating bending test (Note 9) of the cable.

As is clear from the above test results, the cable of the present invention has lower dielectric loss than the cable of the comparative example, and almost no drop in shock resistance value was observed even after the cable was heated and bent, demonstrating excellent characteristics. I own it.

On the other hand, Comparative Examples 2 and 3 have high dielectric loss, and in Comparative Examples 1, 3, and 4, the withstand voltage value decreases significantly after heating and bending, but as a result of disassembling and investigating these cables, it was found that Paper wrinkles were observed, indicating that the insulation configuration was not appropriate.

[Brief explanation of drawings]

FIG. 1 shows the range of mixing ratios of the three-component polypropylene mixed paper used in the present invention. FIG. 2 is a cable sectional view for explaining an embodiment of the oil-impregnated cable according to the present invention, where M is a conductor, A is an internal insulating layer, and B is an external insulating layer.

Claims (1)

[Claims] 1(i) kraft pulp, (1i) polypropylene bulk and (1[D) polypropylene fibers,
) to (iI1) The mixing ratio of the components is at point a on the triangular coordinates ( 1
0, 0, O) point b (5.5, 4, 0.
5) and C point (5.5, 0.5, 4) with a straight line.
A tape of ~125 μ electrical insulating paper is wound on the conductor shielding layer to a thickness of 10 to 50% of the total insulation thickness, and the remaining portion of the total insulation thickness is wrapped on top of the tape consisting of the components (i) to (11D) above, and The mixing ratio of points B, C, and d (1, l,
8) and e point (1, 8, 1) with a straight line (excluding components on the line between point b and point C) with a thickness of 125 to 250 μ. Thickness 125-25 made of insulating paper tape or polypropylene only
An oil-impregnated cable characterized by being wound with 0μ electrical insulating paper tape.