JPS6137723B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of an OF cable.

Currently, in ultra-high voltage power cables, ε
×tanσ (where ε: dielectric constant, tanσ: dielectric loss)
Polypropylene, such as polymethylpentene, will be explained below as a representative example. ) and kraft paper on both sides, commonly known as PPLP.
There is a type of insulating layer that uses a film tape called ``Film Tape'', which is wound around the conductor many times to form an insulating layer. However, this PPLP swells with insulating oil and increases its thickness by 2 to 7 percent, which is common to polyolefin films.

Therefore, if a PPLP tape without any pretreatment is wound on a conductor to form an insulating layer, then dried and impregnated with insulating oil, it may be damaged by swelling of the PPLP. For this reason, as is known from Japanese Patent Publication No. 52-38237, kraft paper for PPLP tape that has been pre-humidified is used, which is wound around the conductor to form an insulating layer, and then metallized paper, The manufacturing method is to wrap an appropriate number of carbon paper, wrap hard aluminum tape on top of it, cover it with an aluminum sheath to form a cable, dry it, deaerate it, and impregnate it with insulating oil. . However, immediately after drying, the PPLP tape that had been subjected to humidity control shrinks and the hard aluminum tape wrapped around its outer layer does not follow this shrinkage, resulting in gaps and wrinkles in the longitudinal direction. becomes. Once such wrinkles occur, the hard aluminum tape will no longer straighten as it is a metal tape, and these wrinkles will compress the underlying insulation layer and cause defects in the finished OF cable.

As is well known, metal tapes such as the hard aluminum tape mentioned above are essential for dissipating the charging current of the cable when in contact with the metal sheath. Since the tape does not shrink when dried and wrinkles appear, there is a risk that the tape may not be able to perform its function of dissipating the charging current as described above.

Therefore, in the present invention, instead of the metal tape, metallized carbon paper such as PPLP tape or a composite tape of polyolefin film and kraft paper is used by winding metallized paper, carbon paper, etc. on an insulating layer. The present invention provides an OF cable that is wound around the outermost layer of a thin layer and is configured so that electrical contact between this and a metal sheath is maintained.

The embodiment shown in FIG. 1 will be described below.

The figure shows a partial cross section on one side from the center line of the OF cable according to the embodiment of the present invention.

The metallized carbon paper used in the present invention is, for example, one made by combining extremely thin aluminum foil and carbon paper, or one made by vapor-depositing aluminum grains. For example, thickness 5
It is a composite of approximately 20μ aluminum foil and 70 to 100μ carbon paper. Metallized paper is a composite of ultra-thin aluminum foil and kraft paper, or it is made by vapor-depositing aluminum grains. It is a composite of kraft paper. In addition, carbon paper is made of ordinary kraft paper made of natural fibers with carbon grains dispersed using a dispersant, or paper made of a mixture of natural fibers and carbon fibers, and is usually dry-impregnated paper. It exhibits a volume resistivity of about 10 ² to ^{10 10} Ωcm.

Although not shown, a carbon paper tape or a metallized paper tape is wound on top of the conductor 1 as necessary, and a humidity-controlled PPLP tape is wound thereon in multiple layers to form an insulating layer 2.

In this insulating layer 2, in order to improve the circulation of the insulating oil and smooth the movement of the insulating tape due to bending of the cable, the tapes in the first layer are spaced apart, and the second and third layers each cover the gap between the tapes in the previous layer. A gap winding method is used.

On this insulating layer 2, a metallized paper tape is gap-wound with the metal side facing outward to form a metallized paper layer 3.

This metallized paper layer 3 has a tan
It is used to ensure that σ does not increase stably, but it may not be used for cables of 275KV or less.

One or two sheets of carbon paper tape are wound on top of this to form a carbon paper layer 4. This carbon paper layer 4 is a semiconducting layer that improves the impulse performance and AC long-term breakdown performance of the cable.

Carbon paper tape 6 is placed on top of this carbon paper layer 4.
and metallized carbon paper tape 5 with the metal side on the outside.
A combined winding is performed in which the metallized carbon paper and the carbon paper are partially overlapped to form a combined winding layer 7 of the metallized carbon paper and the carbon paper. A spiral or corrugated aluminum sheath 8 is then formed thereon. This laminated layer 7
Although not shown, a copper wire woven cloth tape is applied thereon as the case requires.

Layer 7 of carbon paper and metallized carbon paper
exists in order to efficiently flow the charging current to the aluminum sheath 8.

In order to efficiently flow the charging current through the aluminum sheath 8 and reduce the loss due to the charging current in this part, it is effective to bond the aluminum sheath 8 and aluminum foil, and conventionally hard aluminum tape has been used. However, in the present invention, metalized carbon paper is used as described above.

Since the metallized carbon paper is mainly carbon paper (approximately 100μ), it sufficiently follows the drying loss of the insulating layer 2 caused by PPLP and the swelling of PPLP after impregnation, and does not wrinkle.

In such cases, it is natural to consider using metallized paper instead of metallized carbon paper, but as mentioned above, metallized paper can be made of, for example, aluminum foil of about 5 to 20μ and kraft paper of about 70 to 100μ. are composited together and wound so that the aluminum surface is in contact with the aluminum sheath 8, so that the current flows from the lower carbon paper layer 4 to the laminated carbon paper tape 6 to the laminated metallized paper tape 9, as shown in FIG. The route is from the aluminum surface to the aluminum sheath 8, and a small amount of material takes a route directly from the double-wound carbon paper tape 6 to the aluminum sheath 8, and does not flow directly from beneath the metallized paper tape. Considering this path, it goes without saying that the resistance in this part increases, and when this increase is R and the charging current is i, the Watt loss of i ² R increases, so the apparent dielectric This is equivalent to an increase in body loss, that is, tanσ, which is inconsistent with the purpose of using PPLP, which is characterized by particularly low dielectric loss.

In this regard, according to the present invention, as can be understood from FIG. Since the carbon paper layer 4 → laminated carbon paper tape 6 → aluminum sheath 8, and part of the laminated carbon paper tape 6 → aluminum surface of metallized carbon paper tape 5 → aluminum sheath 8, the loss in this part is reduced. In the end, tanσ will not increase.

The process of covering the aluminum sheath 8, drying it, and impregnating it with, for example, dodecylbenzene (DDB) insulating oil is the same as in the case of conventional OF cables made only of kraft paper.

According to the present invention, a 275 KV, 1 x 2000 mm ² OF cable and one using metallized paper instead of the metallized carbon paper in the present invention were manufactured as a prototype, and the cable tan
When σ was measured, it was found that metallized paper was used...0.08 ~
0.09%, using metallized carbon paper...0.07~0.08%
An improvement effect of approximately 0.01 to 0.02% was observed.

Although one embodiment of the present invention has been described above, it goes without saying that an insulating layer may be constructed of a composite film in which kraft paper is integrated on both sides of a polyolefin film such as polymethylpentene or polyethylene. It should be understood that the present invention is also applicable to the insulating layer formed by alternately winding polyolefin film tape and kraft paper tape as described above. Needless to say, in either case, the kraft paper that has been subjected to moisture conditioning during winding is used. (Refer to Japanese Patent Publication No. 52-38237.) As explained above, according to the present invention, in an ultra-high voltage OF cable using a polyolefin film and kraft paper as insulators, the The problem can be solved by applying metallized carbon paper and laminated layers of carbon paper.
The problem has been solved, and its practical effects can be said to be extremely significant.

[Brief explanation of the drawing]

FIG. 1 is a partial longitudinal cross-sectional view of an embodiment of the present invention. FIG. 2 is an explanatory diagram of the charging current flow path when the metal tape of the conventional OF cable, such as hard aluminum tape, is replaced with metallized paper. 1...Conductor, 2...Insulating layer by PPLP winding,
3...Metalized paper layer, 4...Carbon paper layer, 5...
Metallized carbon paper tape, 6... Carbon paper tape, 7... Layered layer, 8... Aluminum sheath, 9... Metallized paper tape.

Claims (1)

[Scope of Claims] 1. A composite of humidity-controlled kraft paper and polyolefin film is wound around a conductor, or an insulating layer is formed by winding humidity-controlled kraft paper and polyolefin film alternately. An OF cable characterized by forming a combined layer of metallized carbon paper and carbon paper on the outermost layer of the formed thin layer, and covering this with a metal sheath. 2. The OF cable according to claim 1, characterized in that a copper wire woven cloth tape is disposed between the metalized carbon paper, the laminated layer of carbon paper, and the metal sheath. 3. Claim 1, characterized in that the composite of humidity-controlled kraft paper and polyolefin film is one selected from polypropylene film and polymethylpentene film, and kraft paper is composited on both sides. OF mentioned in paragraph or paragraph 2
cable.