JPS644287B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a power cable impregnated with an insulating fluid, such as insulating oil or gas, which has improved discharge characteristics. A power cable impregnated with an insulating fluid, such as a gas, generally has a conductor shielding layer 2 on the conductor 1 for the purpose of shielding the surface irregularities of the stranded conductor, as shown in FIG.
On top of that, an insulating layer 3 is formed by wrapping multiple layers of plastic insulating tape, an external shielding layer 4 is provided as needed, and finally the whole is covered with, for example, a metal sheath 5, and the inside is filled with an insulating gas. It has the following basic configuration. Conventionally, the conductor shielding layer 2 is, for example, a second
As shown in the figure, a carbon-containing conductive paper tape 2a is wound around the conductor 1, or as shown in FIG. It was constructed by winding the conductor 1 side. However, such power cables impregnated with insulating fluid have the following drawbacks. That is, in the case of the conductive paper tape 2a shown in FIG.
At this point, the edge of the conductive paper tape 2a becomes a sharp protrusion, and as shown in the enlarged view in FIG.
As a result, electric field concentration tends to cause partial discharge, which becomes a serious cause of dielectric breakdown. Next, when a single-sided metallized paper tape 2b as shown in FIG. 3 is further wound on the outside, the edge of the conductive paper tape 2a described above is properly suppressed, and the possibility of such a problem is reduced. However, if the power cable is subjected to extreme bending, etc., the edges of the single-sided metallized paper tape 2b will wrinkle, as shown in the enlarged view in Figure 5, and if this is extreme, it will protrude as shown in Figure B. , a sharp depression occurs in the equipotential line a at this portion, which becomes a serious cause of dielectric breakdown as described above. This problem occurs even when insulating oil is used as the above-mentioned insulating fluid, but it is particularly serious when an insulating gas having a relatively low dielectric strength is impregnated. In recent years, gas-impregnated power cables impregnated with an electrically negative gas such as SF ₆ have attracted attention as cables that meet various objectives such as low capacitance and low dielectric loss. However, in devices using such electrically negative gases, even if the above-mentioned electric field concentration area is extremely small, partial discharge is very likely to occur in the area, which inevitably causes dielectric breakdown. The reality is that there is a strong demand for appropriate improvements. The inventors have made extensive studies to solve this problem, and found that a surprising effect was obtained by using the single-sided metallized tape in at least the outermost layer of the conductor shielding layer as described in detail below. This discovery led to the completion of this invention. That is, the present invention provides a power cable having a basic structure in which a conductor shielding layer, an insulating layer formed by wrapping multiple layers of plastic insulating tape, and a sheath are provided on a conductor in this order, and the inside is filled with an insulating fluid. Using a single-sided metallized tape, in which a metal layer is provided on one side of the base tape with at least the outermost layer portions exposed to a slight width of the base tape at both edges in the longitudinal direction, the metal layer surface is placed on the conductor side. This power cable is characterized in that it is formed by winding it while providing a gap. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 6, 11 is a conductor, 12 is a conductor shielding layer, 13 is an insulating layer, 14 is an outer shielding layer, and 15 is a sheath, which have the same basic structure as the conventional one described above. In this invention, the metallized tape 12b used as the outermost layer of the conductor shielding layer 12 is made of aluminum foil having a narrower width on one side of a base tape 12' made of plastic, paper, etc., as shown in FIG. A metal foil of about 2 mm is placed on each longitudinal edge of the base tape 12' in exposed tape parts 12.
A single-sided metallized tape is used in which a metal layer 12'' is provided by bonding the metal layer while leaving the metal foil, or by depositing a metal instead of the metal foil, and when winding, the metal layer of the single-sided metallized tape is used. The 12'' side faces the conductor side. The conductor shielding layer 12 thus formed has a cross-sectional configuration as shown in FIG. In the figure, 11
1 is a conductor, 13 is an insulating layer, and a conductor shielding layer 12 formed of the conductive paper tape 12a and the single-sided metallized tape 12b formed as described above is provided between them. In this case, the metal layer 12'' is on the conductor side and is flush with the surface of the conductive paper tape 12a, so that the above-mentioned equipotential lines are not disturbed.And as mentioned above, when the cable is bent, if one side is made of metal Even if wrinkles occur on the side edges of the adhesive tape 12b and the side edges rise as shown in FIG. 9, there is no metal layer on these side edges, and the equipotential lines as described above are disturbed. When winding the single-sided metallized tape 12b, keep a gap at the side edges to prevent damage caused by bumping, especially when bending. If a conductive surface that is continuous in the longitudinal direction of the cable is formed by the metal layer 12'' of the metallized tape 12b and the conductive paper tape 12a inside it, the equipotential lines can be aligned most stably. becomes the most preferred. Furthermore, the present invention significantly solves the above-mentioned drawbacks when an electrically negative gas such as SF ₆ is used as the insulating fluid. As is clear from the above description and the examples described later, the present invention has a structure in which at least the outermost layer of the conductor shielding layer on the conductor is exposed on one side of the base tape at both edges in the longitudinal direction by a slight width of the base tape. Since it is formed by winding a single-sided metallized tape with a metal layer on it with the metal layer side facing the conductor side, even if wrinkles occur at the edge of the single-sided metalized tape when the cable is bent, the metal part will not protrude. There is almost no disturbance to the equipotential lines, and as a result, it is possible to prevent the cable characteristics from deteriorating due to the electric field concentration described above, and its industrial value is extremely high. The present invention will be specifically explained below with reference to Examples. Example 1 and Comparative Examples 1 and 2 A gas insulated power cable having the configuration shown in FIG. 6 was obtained according to the specifications shown in Table 1 below.

[Table] The partial discharge characteristics of the obtained cable were investigated and are shown in FIGS. 10 and 11. According to the same figure, the initial value (Figure 10) of the characteristic is that of Comparative Example 1.
was considerably low, and Comparative Example 2 and Example 1 were substantially equivalent. Next, when looking at the change in the characteristic value (Fig. 11) after the cable was subjected to extreme bending (bending twice to a diameter 15 times the outer diameter of the sheath), it was found that the comparative example 2 was the same as the comparative example 1.
However, in the Example product, almost no change was observed. Then SF ₆ gas pressure for these cables
Impulse characteristic values (KV) at 0.9MPa are shown in Table 2 below.
It was hot on the street.

[Table] According to the results in this table, it was clear that the characteristics deteriorated in all cases due to the occurrence of wrinkles in the insulating layer due to extreme bending, but the Example product had the least amount of wrinkles. In all of the above results, the Example products were excellent in that the deterioration due to the bending was slight.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional power cable impregnated with insulating fluid, Figures 2 and 3 are partial cross-sectional views of two examples of the same conductor shielding layer, and Figures 4 and 5 are equipotential lines of the two examples. 6 is a cross-sectional view of the cable of the present invention, FIG. 7 is an oblique view of the single-sided metallized tape used in the present invention, and FIGS. 8 and 9 show the normal partial structure of the conductor shielding layer. FIGS. 10 and 11 are partial discharge characteristic diagrams showing before and after bending, respectively, comparing the product of the present invention with a comparative product. 1, 11... conductor, 2, 12... conductor shielding layer,
2b, 12b... Single-sided metallized tape, 12'...
Base tape, 12″... Metal layer, 3, 13... Insulating layer, 5, 15... Sheath.

Claims (1)

[Scope of Claims] 1. A power cable having a basic structure in which a conductor shielding layer, an insulating layer formed by winding multiple layers of plastic insulating tape, and a sheath are provided in this order on a conductor, and the inside is filled with an insulating fluid. Using a single-sided metallized tape in which the outermost layer of the conductor shielding layer is provided with a metal layer on one side of the base tape with a slight width of the base tape exposed at both edges in the longitudinal direction, A power cable characterized in that it is formed by winding the metal layer side with the conductor side and providing a gap. 2. A patent characterized in that the conductor shielding layer is provided in such a way that the metal surface of the outermost conductor shielding layer and the conductive surface of the inner conductor shielding layer form a conductive surface that is continuous in the longitudinal direction of the cable. The power cable according to claim 1. 3. The power cable according to claims 1 and 2, wherein the insulating fluid is an electrically negative gas.