JPS6068506A - 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 Field of Industrial Application The present invention relates to an electric power cable that is used for power supply in power stations, plants, etc. and has improved air characteristics, heat resistance, etc.

<Background of conventional technology and its melting point> Conventionally, the insulator layer of plastic power couples has
Crosslinked low-density polyethylene, which has improved heat resistance through crosslinking, is often used. High density polyethylene (H, D
Compared to low-density polyethylene (bDp), PE) has excellent physical properties such as being strong against electric shock and having high dielectric breakdown strength, but conventionally, it has not been possible to proceed with crosslinking process satisfactorily. This posed a problem for use in the insulation layer of electric power cables. In other words, when attempting to chemically crosslink high-density polyethylene by incorporating an organic peroxide, the crosslinking reaction progresses inside the extruder due to the extrusion heat (extrusion temperature is usually 140°C or higher), resulting in high-density polyethylene. As the cables gradually harden, extrusion coating becomes increasingly difficult, making it impossible to stably manufacture ICs on long cables. In addition, when increasing heat resistance by radiation crosslinking (usually electron beam crosslinking), the crosslinking itself can be carried out smoothly, but if the insulator is thick, the radiation cannot reach the inside of the insulator. It was not possible to manufacture cross-linked cables.

Therefore, the present inventor conducted extensive research to utilize high-density polyethylene as an insulator layer, and first, a silane-grafted high-density polyethylene composition in which vinyltrialkoxysilane or the like is grafted onto high-density polyethylene was applied onto a conductor. By extrusion coating and then carrying out water-mediated silane crosslinking treatment according to a conventional method, it was found that silane crosslinking of the high density polyethylene composition was possible. However, in the conventional silane cross-linking treatment method in which the cable is passed through water, in the case of high-density polyethylene, the penetration and diffusion of water into the inside of the insulating layer is slow, and cross-linking occurs inside the insulating layer. It is difficult in practice to produce HFC cables in which the entire insulation layer is crosslinked, as it takes a long time to develop. This is especially difficult for thick gooples. Therefore, the present inventor conducted extensive research and found that if a silane-grafted high-density polyethylene composition was extruded and coated on a cotton body, then passed through a continuous steam crosslinking device and subjected to a silane crosslinking treatment in high-temperature steam. It has been found that even in the case of thick-walled cables it is possible to obtain totally silane-crosslinked cables.

<Object of the Invention> The present invention has been made with attention to the above-mentioned problem, and its purpose is to provide a heat-resistant power cable with further improved IR properties such as dielectric breakdown strength. It is about providing.

<Summary of the Invention> The electric power cable according to the present invention coats a conductor with a silane-grafted high-density polyethylene composition, and then performs a silane cross-linking treatment in high-temperature steam to form an insulator of the cross-linked high-density polyethylene composition. It is characterized by forming layers. This electric power cable uses high-density polyethylene for its insulating layer, which has high insulation properties and is strong against electric shock, so compared to low-density polyethylene cables,
Dielectric breakdown strength is further strengthened. In the present invention,
In high-temperature steam (e.g., temperature 80-200°C, pressure 0.
Since the silane crosslinking treatment was carried out at 6~'5 Kg/cm2), the penetration and diffusion of water into the inside of the insulator layer is accelerated, and the crosslinking reaction proceeds quickly, allowing even thick cables to be processed at normal wire speeds. Crosslinking is possible over the entire insulator layer.

<Example> Embodiments of the present invention will be described below based on the drawings.

In the power group 1 shown in FIG. 1, 2 is a conductor made of 325 stranded annealed copper wire, 3 is an internal semiconductive layer filled with carbon black or the like and has semiconductivity, 4 is an insulating layer made of cross-linked high-density polyethylene, 5 is an outer semiconducting layer having semiconductivity like the inner semiconducting layer 3. Group 1 describes the process as follows: “First, a 7-run grafted high f&1 degree polyethylene composition for the insulating layer was prepared by grafting the remaining silane to high-density polyethylene, including vinyltrimethoxysilane and vinyltriethoxysilane. In addition, a resin composition for the outer semiconductive layer was prepared by adding carbon black, etc., and these compositions were coextruded and coated on the conductor 2 to form the inner semiconductive layer 3 (layer thickness 1).
between), insulator layer 4 (j6 thickness 11am), external half conductor/g
j5 (layer thickness: 1 mm), and then passed through a steam crosslinking device to high-temperature steam (temperature: 160°C, pressure: 6 Kg/cm).
2) was produced by performing silane crosslinking treatment.

As Comparative Example 1.2, an inner semiconductive layer, a P3 edge body, and an outer semiconductive layer were coextruded on a conductor in the same manner as in the above example, and a non-crosslinked high-density polyethylene film without silane crosslinking was prepared.
composition, and chemical crosslinking/%4'/Jo sitI
+Ca's rtp l +I Ding R-1/y I
A Yt*-force cable with n imaginary power polygon was manufactured with the same size and layer thickness as in the example.

Therefore, in order to know the dielectric breakdown strength and heat resistance of the cables of Example and Comparative Example 1.2, the impulse breakdown strength at 130°C and the heating deformation rate at a high temperature of 140°C were measured. However, the results are shown in Table 1 below.

Table 1 [From this table, it is clear that the electric power cable of the present invention has further enhanced dielectric breakdown strength and improved heat resistance.

In the present invention, the silane-crosslinked high-density polyethylene is prepared by using the silane-grafted high-density polyethylene that has been grafted in advance as described above, and by supplying necessary additives such as silane in the extruder. However, high-temperature polyethylene may be directly made into kraft.

<Effects of the Invention> As explained above, the power couple according to the present invention employs a cross-linked high-density polyethylene composition for the insulating layer, so that it has better insulation than the conventional general-purpose cross-linked low-density polyethylene composition. It has the effect of having excellent electrical properties and heat resistance with respect to breaking strength.

[Brief explanation of drawings]

? , -1 is a sectional view showing a power group according to an exemplary embodiment of the present invention. 1 *Fung* Electric cable, 2.0 conductor, 4.--insulator Rzu. Owner: Fujikura Electric Wire Co., Ltd.

Claims (1)

[Claims] An electric power cable characterized in that a conductor is coated with a silane-cruated high-density polyethylene composition as an insulator, and then the insulator is cross-linked with silane in high-temperature steam.