JPS643292B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flexible conduit aerial cable with improved electrical characteristics.

Recently, a stranded conductor 11 is housed in a corrugated metal tube 12 as shown in FIG.
2, split insulating spacers 13 are attached at predetermined intervals, a corrugated metal sheath 14 with an anti-corrosion layer 15 is placed on the outside, and an insulating gas 16 is placed inside the metal sheath 14.
A gas-insulated cable has been proposed. In a conduit aerial cable having such a structure, the mounting inner circumferential surface of the insulating spacers 13 that support the internal corrugated metal tubes 12 at predetermined intervals for storing the stranded wire conductors 11 is the outer circumferential surface of the corrugated metal tubes 12. It is attached in contact with the protrusion a' that protrudes from the top. However, the convex portion on the outer circumferential surface of the corrugated metal tube 12 in the gas insulated cable
As shown in FIG. 1B, a' is a part where the electric field is particularly concentrated, and since there are an insulating gas 16 and an insulating spacer 13 with different dielectric constants in the metal sheath 14 of the cable, the corrugated metal tube is A large electric field is concentrated at the contact portion between the insulating spacer 13 mounted on the corrugated metal tube 12 and the convex portion a' of the corrugated metal tube 12, resulting in dielectric breakdown at low voltage.

The present invention aims to eliminate such drawbacks and provide a conduit aerial cable having excellent electrical characteristics.Examples illustrating the present invention will be described below.

In Figure 2, 1 is a stranded conductor, 2 is a stranded conductor 1
3 is a divided insulating spacer in which a plurality of leg rods 5 are arranged in a row facing each other on the inner circumferential surface 4 of an axial hole, and the insulating spacer 3 is a third
As shown in FIG. 4A and FIG. They are installed closely together. Reference numeral 6 denotes a corrugated metal sheath that covers the outside of the metal tube 2 to which insulating spacers 3 are attached at predetermined intervals.A corrosion protection layer 7 is applied to the outer peripheral surface of the corrugated metal sheath 6, and an insulating gas 8 is provided inside the corrugated metal sheath 6. is included. The length a of each leg rod 5 formed on the insulating spacer 3 is as follows: a=h+g...(1) However, h: Corrugation height of the internally corrugated metal tube g: Gap length between the corrugated convex portion of the metal tube and the insulating spacer D: Cable outer diameter L: The relationship between the installation width of the insulating spacer to the metal tube. It is desirable to set it to a satisfactory length. The reason for this is that if the edge of the insulating spacer 3 hits the corrugated metal tube 2 when the cable is bent during installation, an excessive force will be applied to the spacer 3 and there is a risk that it will be deformed or damaged. In order to prevent such an accident, a gap g satisfying the above formula (2) is provided between the spacer 3 and the corrugated metal tube 2. Although the above embodiments have been illustrated and described as gas insulated cables in which the stranded wire conductor 1 is housed in the corrugated metal tube 2, the present invention is not limited to such embodiments, and may be used instead of the stranded wire conductor. Of course, the design can be changed as appropriate, such as by using a metal corrugated pipe conductor or a pipe conductor, and by forming concave and convex portions continuously in a spiral shape on the outer peripheral surface of the corrugated metal tube 2.

According to the present invention, as described above, each of the plurality of leg rods 5 protruding from the insulating spacer 3 that supports the flexible corrugated metal tube 2 at predetermined intervals is connected to the trough portion 2 of the metal tube 2.
Since the length of the leg rod 5 is set so as to be in close contact with the insulating spacer 3 and to create a predetermined gap g between the inner peripheral surface of the spacer 3 and the metal tube 2, the mounting portion of the insulating spacer 3 is There is no risk of dielectric breakdown at low voltages due to partial discharge occurring, and a conduit aerial cable with stable electrical properties over time can be obtained. A leg rod 5 is provided, and its length a is set to a length that satisfies the above-mentioned relational expression, so that a gap g of a predetermined length is created between the insulating spacer 3 and the corrugated convex portion of the corrugated metal tube 2. This configuration has the advantage that accidents such as deformation or damage of the internal insulating spacer 3 caused by bending of the cable during installation can be eliminated.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing a conventional flexible conduit aerial cable, Fig. 2 is an explanatory diagram of main parts showing an embodiment of the present invention, and Figs. 3 and 4 are explanatory diagrams of an insulating spacer in the present invention. It is. 1: Stranded wire conductor, 2: Corrugated metal tube, 3: Insulating spacer, 4: Inner peripheral surface of shaft center hole of insulating spacer, 5: Leg rod, 6: Corrugated metal sheath, 7: Corrosion protection layer, 8: Insulation gas.

Claims (1)

[Claims] 1. A plurality of leg rods are protruded into the inner peripheral surface of the axial hole of an insulating spacer that coaxially supports an internal corrugated metal tube housing a stranded conductor and an external corrugated metal sheath. and each leg of the insulating spacer is brought into close contact with the trough of the corrugated metal tube so that a predetermined gap is created between the inner peripheral surface of the insulating spacer and the corrugated convex portion of the internally corrugated metal tube. A flexible conduit aerial cable that can be removed by hand and is made by sealing an insulating gas inside a corrugated metal sheath. 2 In claim 1, the length a of the leg rod protruding from the insulating spacer is a=h+g However, h: Height of the corrugation of the internally corrugated metal tube g: Gap length between the corrugated convex portion of the metal tube and the insulating spacer D: Outer diameter of the cable L: Width of the installation of the insulating spacer to the metal tube A flexible conduit aerial cable characterized by being set to a length that satisfies the relationship.