JPS58137909A - Gas-immersed power cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas-impregnated cable cable, and particularly to a plastic tape constituting the cable insulation layer thereof.

BACKGROUND AND OBJECTIVES OF THE INVENTION For 750 kV and 1100 kV class UHV cables, the value of ε is required to be 2.5 or less and the taJ to be 0.05% or less in order to reduce the dielectric loss of the cable insulation layer.

The structure of the cable insulation layer that satisfies such requirements requires that the wound layer of plasti or cutave be impregnated with gas and pressurized to improve the withstand voltage characteristics. In such a configuration, the gas flows through the thickness (radial)
It cannot pass through the plastic tape, and only longitudinal impregnation between the plastic tapes can be expected.

Therefore, it has been considered to emboss the plastic tapes to increase the gap between the plastic tapes. Embossing is done by mechanical, thermal, chemical treatment, etc. Therefore, 1) the price of plasti and tape increases, and 2) large embossments may reduce power transmission capacity due to increased thermal resistance. ,
3) If the emboss is small, the emboss will return to its original state under the heat cycle of the cable, and the emboss on the tape surface may disappear if it is due to mechanical or thermal treatment. There are disadvantages such as .

Note that semi-synthetic paper such as laminated paper is easily impregnated with gas, but cannot be used because it cannot satisfy the above dielectric properties. In addition, since heating and vacuum drying is required to remove moisture from Kraft B paper, there is also the drawback that manufacturing costs are high.

This invention solves the above problems, and has the following properties: 1) Even without special embossing, gas impregnation can be made as good as with embossing, 2) The above requirements for dielectric properties are met, and 3) The object of the present invention is to provide an impregnated capeple that has low thermal resistance, high AO and impulse breakdown values, and 4) low manufacturing costs.

Configuration of the invention (1) Cable insulation J140 is made of plastic tape 4
(2) As the plastic tape 41, 100 parts by weight of plasti resin is added with an average particle size having a higher melting point than that of the plastic. 1 to 3 organic or inorganic fine particles of 1 to 100 μm
0 parts by weight are mixed and extruded, and particles 44 protrude over the entire surface (Fig. 2).

As the plastic resin, polyethylene, polypropylene, polymethylpentene, etc. are used. As the fine particles, high melting point plastics and inorganic materials such as crosslinked polyethylene, crosslinked polypropylene, crosslinked polymethylpentene, Teflon, silica, TE, and Lumina are used.

As an example of the method for manufacturing the plastic tape 41 used in the present invention, raw materials for the tape body (polypropylene,
Particles of plastic (cross-linked polypropylene, cross-linked polyethylene, etc.) that do not melt at the temperature of the melt are mixed in a pellet of polyethylene, etc. at a ratio of about 10:1,
In the case of polypropylene, it is extruded through a T-die at about 200°C. In this case, since the plastics are from the same series, the interface between the tape body and the particles has good adhesion in a high-temperature molten state, and no voids are formed.

After extrusion molding and cooling as described above, co-axial stretching may be performed. In this case, since the tape 41 becomes thinner, the ratio of the thickness of the tape to the height of the outside portion of the plastic particles 44 increases. This increases the gap between the layers of the plastic tape 41 in the cable insulation layer 40, making it easier for gas to be impregnated. Furthermore, since the mechanical strength is increased by stretching, the tape winding properties are improved, and the heat resistance is also improved.

When the plasti and cutape 41 are made by extrusion molding in this way, there is no need for special embossing as in the past, so the manufacturing cost is reduced to about half.◇ The above plastic and cutape 41 are wound. , to form a cable insulation layer 40 (FIG. 1).

In "Figure 7", 10 is a gas passage, 20 is a cable conductor, 30 is an internal barrier layer, 50 is an external barrier layer, 60 is a metal sheath, and 70 is a corrosion protection layer, which are the same as in the conventional case. It is.

In the present invention, if the particle diameter is smaller than 1 μm, it will be buried in the plastic resin of the tape base material, making it impossible to form protrusions of the desired height. If it exceeds 100 μm, the protrusion height will be too large, resulting in thermal resistance The mechanical strength also decreases.

On the other hand, if the amount of particles mixed in is less than 1 part by weight, the unevenness of the tape surface will decrease and gas flow will deteriorate.

"Figure 4" shows the relationship between the number of particles mixed in and the gas specific flow resistance of the cable insulation layer around which the tape is wound, and the specific flow resistance suddenly increases when the number of particles mixed in is 1 part by weight or less. It appears that this will increase.

If the amount of particles mixed in is more than 30 parts by weight, the mechanical properties of the tape deteriorate, particularly when stretched, thin portions or holes may be formed at the electrodes, making it impossible to use the tape as an electrical cable insulator.

Effects of the invention (1) A cable insulation layer with excellent gas impregnation properties can be produced.

(2) By using materials with good dielectric properties, such as polypropylene and crosslinked polyethylene, it is possible to make cables with cable insulation layers that meet the dielectric properties requirements mentioned at the beginning.

(3) A cable with a plastic tape-wrapped cable insulation layer with low thermal resistance can be made.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is an explanatory diagram of a plastic tape 41, and FIG. 3 is an enlarged sectional view of the plastic tape 41. Figure 5 is a relationship diagram showing the gas flow characteristics of the cable insulation layer. 40: Cable insulation layer 41 Nibra Chichi tape 42: Tape body 44: Particle Patent applicant Keiji Kokuji, agent for Katokura Electric Wire Co., Ltd.

Claims (2)

[Claims] (1) In a gas-impregnated cable cable in which the cable insulation layer is made of a wound layer of plastic tape impregnated with an insulating gas, the plastic tape includes plastic resin 10.
0 parts by weight, the plasti, an average particle size 1 with a higher melting point than the
1 to 30 organic or inorganic fine particles of ~100 μm
A gas-impregnated capsule characterized by being extruded by mixing parts by weight. (2) After the plastic tape is molded by extruding the plastic resin, it is further coaxially stretched, resulting in a part of the particles entering the tape body and a part appearing outside the tape body. A gas-impregnated capeple according to claim 1, characterized in that: