JPS6344249B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber built-in power line in which an optical fiber core wire is enclosed inside a power line such as an overhead power transmission/distribution line or a power cable.

In recent years, optical fiber cables have been developed and used for communications.

Fiber optic cables have a large information capacity,
Since it is not subject to electromagnetic induction interference, it can be encapsulated within power lines.

In general, power line conductors are made of stranded wire conductors made by twisting multiple strands of wire, and when the power line is installed, an initial elongation of about 0.1 to 1% occurs due to the tightening of the twist, tension, bending, etc. This will also apply to optical fibers. On the other hand, the permissible elongation of optical fiber is about 1 to 2% at most, so an unreasonable elongation is already applied to the optical fiber at the time of power line installation, and as a result, even if there is no initial abnormality, long-term creep and elongation due to thermal expansion and contraction occur. , and external forces such as vibrations applied in this stretched state significantly shorten the life of the optical fiber.

The present invention has been made to solve the above-mentioned problems, and includes providing a longitudinal hole with a radially elongated cross section inside a stranded conductor of a power line, and By storing the optical fiber core in a hole and providing a void inside the core, when the stranded conductor stretches during power line installation, the optical fiber core itself can be stretched from the position outside the void. It moves to the inner cavity where the core diameter is smaller and absorbs the elongation, so no elongation force is applied to the optical fiber.
The purpose is to provide a power line with built-in optical fiber that will not be damaged.

The present invention provides a stranded conductor for a power line formed by twisting a plurality of strands of strands, in which longitudinal grooves are provided on the surface of at least some of the strands other than the center on the radially center side. A power line with a built-in optical fiber, characterized in that an optical fiber core wire is housed in a groove, and a groove-like cavity facing the groove is provided on the surface of the wire on the radially center side in contact with the groove. . The stranded wire conductor used in the present invention is a compressed conductor in which at least the stranded wire portion in which grooves are provided is a compressed conductor with almost no gaps between the strands, as shown in the embodiments shown in FIGS. 1 to 5. , is usually formed by twisting together multiple strands of fan-shaped, trapezoidal, or other irregular cross-section, and although the center is made up of a single strand in the figure, it can also be formed by twisting multiple strands of strands together. good. The stranded wire layer other than the stranded wire portion in which the groove is provided may be composed of round wires as shown in the figure, or may be composed of irregularly shaped wires, or may be omitted. These strands are metal wires or composite metal wires that are normally used for stranded conductors.

In the present invention, the optical fiber core means a core made of optical fiber (glass fiber) or a wire coated with a coating layer of synthetic resin or the like.

1 to 5 are cross-sectional views showing a twisted wire conductor section in an embodiment of the present invention. In the figure, the inside of the stranded wire is a compressed conductor, and three to six strands 2 having irregular cross sections are twisted around one center line 1 having a circular or polygonal cross section. A plurality of round wires 3 are twisted together to form an outermost layer around the compressed conductor. On the surface of each strand 2 in the outer layer around the center line 1 of the compressed conductor on the radial center side, longitudinal grooves 5 for storing the optical fiber core 4 are provided. A groove-like cavity 6 is provided on the surface of the center line 1 which is in contact with the groove 5 and is aligned with the groove 5 .

In this way, when the optical fiber core 4 is inserted into the radially outer groove 5, for example, during twisting, the insertion is easy, and the optical fiber core 4 after insertion is
has a structure in which it can move to the groove-like cavity 6 on the radially inner side where the layer core diameter is smaller. In other words, when the stranded conductor is stretched due to an external force applied during the installation of a power line, the optical fiber core 4 moves from the position of the outer groove 5 to the inner groove-like cavity 6 where the core diameter is smaller. This creates a margin for elongation and absorbs the elongation, so that no large elongation force is applied to the optical fiber core, and damage is prevented.

Hereinafter, the mechanism for preventing the optical fiber from stretching according to the present invention will be explained in more detail. FIG. 6 is a cross-sectional view showing a model of the optical fiber built-in part in the present invention. In the figures, the same reference numerals as in FIGS. 1 to 5 indicate the same parts.

Display various specifications as follows.

r ₀ : Inner radius of the layer in which the optical fibers 2 are twisted together (radius outside the center line groove) (mm) p: Pitch length of the layer in which the strands 2 are twisted (mm) δ ₀ : Outer diameter of the optical fiber core wire 4 (mm) δ ₁ : Depth of the groove 5 that accommodates the optical fiber (mm) δ ₂ : Depth of the groove-shaped cavity 6 (mm) ε: Permissible elongation of the stranded conductor Rate △: Allowable elongation rate of optical fiber core L ₁ : Optical fiber core length (mm) when the stranded conductor has no elongation and the optical fiber core is housed in groove 5 L ₂ : Stranded wire The length of the optical fiber (mm) when the conductor is stretched by ε and the optical fiber falls to the innermost radial direction (minimum diameter) of the groove-shaped cavity 6. Now, L ₂ is the length of the optical fiber. The conditions within the allowable elongation are given by the following equation.

Here, by rearranging equation (1) under the condition of (2πr ₀ /p) ² <<1...(2), the following equation is obtained.

(2π/p) ² (r ₀ +δ ₁ −δ ₂ /2) {(δ ₁ +δ ₂ ) −δ ₀ >ε−△ ...(3) An optical fiber core that satisfies this equation (3) By realizing a built-in stranded conductor structure, it is possible to create a power line with a built-in optical fiber that keeps the elongation of the optical fiber core below the allowable elongation and minimizes the cross-sectional area of the wire.

In particular, the conditions are such that the depth δ ₁ of the groove 5 and the depth δ ₂ of the groove-like cavity 6 are equal and the optical fiber core 4 is not stretched, that is, δ ₁ = δ ₂ = δ △=0...( If equation 4) is established, equation (3) will be given by the following equation.

δ＞δ ₀ /2+εp ² /8π ² r ₀ ...(5) Furthermore, if the depth δ ₁ of the groove 5 is equal to the outer diameter δ ₀ of the optical fiber core 4, that is, δ=δ ₀ ...(6) In this case, the conditional expression for the twist pitch length p is as follows.

Now, in equation (7), the optical fiber core wire outer diameter (δ) is 1 mm, and the inner radius of the layer in which the strands 2 are twisted
If r ₀ is 2.5 mm, the twist pitch length p of that layer is
140mm or less for stranded conductor elongation ε of 0.5%,
If the elongation ε of the stranded wire conductor is 1%, it is necessary to keep the elongation to 100 mm or less.

As described above, according to the present invention, when an external force is applied during the installation of a power line and the stranded conductor elongates within the allowable elongation, it is possible to create a structure that does not cause elongation to the optical fiber core wire. It is.

In addition, the wire structure according to the present invention can protect the optical fiber core wire compared to a wire structure in which the stranded conductor main body is completely void, and since the center wire body is made of a conductive metal, it can be used as a conductor. , the wire cross-sectional area can be minimized.

The structure of the stranded wire conductor according to the present invention is shown in Figs.
It is not limited to the structure shown in FIG.
The center of the stranded wire conductor may be formed by twisting multiple strands of wire other than one center line, and the stranded wire layer housing the optical fiber core other than the center may be two or more layers in addition to one layer. Also, the strands in which the grooves for storing the optical fiber core wires are provided in the stranded wire layer other than the center may be some or all of the strands in the layer. Further, the number of twisted wire layers may be one or more, and the number and shape of the strands constituting the twisted wire layers are not particularly limited.

As described above, the present invention provides a stranded conductor for a power line, in which a longitudinal groove is provided on the surface of at least some of the strands other than the center on the radially center side, and an optical fiber core is provided in the groove. In addition to storing the wire,
Since a groove-like cavity facing the groove is provided on the surface of the wire on the radial center side in contact with the groove, when the stranded conductor is stretched due to an external force applied during power line installation, the optical fiber core By moving the wire from the radially outer groove position to the radially inner groove-like cavity where the core diameter is smaller, there is a margin for elongation, the elongation is absorbed, and the optical fiber core has a large It has the advantage of providing a safe wire with built-in optical fiber that does not undergo any stretching force and will not be damaged over a long period of time.

Further, the present invention has a stranded conductor structure with a built-in optical fiber that satisfies equation (3), so that the elongation of the optical fiber is kept below the allowable elongation and the cross-sectional area of the wire is minimized. There is an advantage that a type power line can be realized.

[Brief explanation of the drawing]

1 to 5 are cross-sectional views showing a twisted wire conductor section in an embodiment of the present invention. FIG. 6 is a cross-sectional view showing a model of the optical fiber built-in part in the present invention. 1...Center line, 2...Element wire, 3...Round wire, 4...
...Optical fiber core wire, 5...Groove, 6...Groove-shaped cavity.

Claims (1)

[Scope of Claims] 1. In a stranded conductor of a power line made by twisting a plurality of strands, a longitudinal groove is formed on the surface of at least some of the strands other than the center on the radial center side. and storing the optical fiber core in the groove,
1. A power line with built-in optical fiber, characterized in that a groove-like cavity facing the groove is provided on the surface of the wire on the radially center side in contact with the groove. 2. The power line with a built-in optical fiber according to claim 1, wherein the strand on the center side in which the groove-like gap is provided is one center line. 3 Outer diameter of the optical fiber core δ0 (mm), depth of the groove for storing the optical fiber core δ ₁ (mm), depth of the groove of the groove-like cavity δ ₂ (mm), depth of the groove for storing the optical fiber core The light according to claim 1 or 2, which has the following relationship between the twist pitch length p (mm) of a layer made of twisted wires and the inner radius r ₀ (mm) of the layer. Power line with built-in fiber. (2π/p) ² (r ₀ + δ ₁ − δ ₂ /2) {(δ ₁ + δ ₂ ) − δ ₀ }>ε−△ where ε: Permissible elongation rate of the stranded conductor △: Optical fiber core wire Allowable elongation rate.