JPH05198219A - Optical fiber composite overhead earth-wire - Google Patents

Abstract

PURPOSE:To realize a communication line involved in a power transmission line, which is economical and has high reliability. CONSTITUTION:A hollow tube 2 is twisted together with bare metal wires of an overhead earth-wire in which a plurality of bare metal wires 1 are twisted, and one or plural optical fibers are placed in a space defined by the hollow tube 2. The bare metal wires are aluminium-coated steel wires.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an optical fiber composite overhead ground wire.

[0002]

2. Description of the Related Art Conventionally, wired and microwave systems have been used for communication and control lines in the field of electric power.

However, in the wired system, it is extremely troublesome to separately lay out communication and control lines, and there is a drawback that the power line and noise due to lightning strikes affect the system.

In the microwave system, the transmission line is not interrupted because it is wireless, but in recent years the amount of information required has increased and it has become very difficult to allocate microwaves. In this case as well, the power line is used. The effect of noise from lightning and lightning was inevitable.

Therefore, recently, a composite power cable in which a power cable and an optical fiber are integrally incorporated has been proposed. (For example, Japanese Utility Model Laid-Open No. 50-62542) With this composite type power cable, it is not necessary to separately install communication and control lines. There is no allocation problem like the microwave method. Since the optical fiber is used, the electromagnetic induction disturbance does not become a problem and the signal reliability is high. It is effective as a communication line that accompanies a highly reliable power transmission line having a large amount of information and high reliability.

[0006] However, it is not realistic to stretch such a composite type power cable all over the country regardless of the case where it is installed underground between substations in an urban area.
That is, since the power cable and the optical fiber are covered with an insulating protective coating and integrated, the price per unit length is expensive and not economical, and when installed overhead, it is easily damaged by lightning strikes, etc. Insufficient reliability.

In consideration of laying in a mountainous area in a rural area, it is conceivable that the overhead power transmission line made of bare metal wire and the optical fiber are integrally twisted or attached. (Swiss patent 567 for showing similar construction
There is 730. ) However, the coefficient of thermal expansion and Young's modulus on the bare metal wire and the optical fiber are remarkably different, and the optical fiber is extremely weak. The optical fiber will be damaged.

[0008] In case of aerial installation, of course, the influence of wind and snow, lightning, and the like is expected, so that practical reliability cannot be obtained with such a structure.

[0009]

Prior art of the present invention: Therefore, as shown in FIG. 3, an optical fiber 3 is housed in one or a plurality of metal tubes 2, and the metal tubes 2 are made up of a bare metal wire. It is conceivable to attach and integrate them with the suspension frame 5.

Even with such a structure, the communication line can be secured at the same time as the power transmission line. There is no allocation problem like the microwave method. Since an optical fiber is used, electromagnetic induction interference is not a problem and reliability is high. In addition to the same effect as in the prior art, it is more economical than the composite power cable of the prior art because it is integrated with the overhead power transmission line made of bare metal wire. Since the optical fiber is housed in the metal tube, it is more reliable than the conventional technology in which it is simply integrated. That is the effect.

That is, even when the overhead power transmission line expands or contracts, this effect affects the metal tube, but does not directly affect the optical fiber accommodated in the metal tube, and the optical fiber slides in the metal tube. The stress can be avoided.

However, the technique at this stage has the following major problems.

(A) It is complicated to handle because it is integrated with an overhead power transmission line to which a high voltage is applied. That is, although the optical fiber itself is an insulator for some time, there is a risk that the drawn part may become dirty and creeping discharge may occur, and it is also necessary to stop power transmission for maintenance of the optical fiber part, so various measures are necessary. Becomes

(B) Since an overhead power transmission line requires a certain amount of current capacity, a metal having high conductivity such as aluminum is mainly used and it is not always possible to select the tensile strength first, so that the outer diameter tends to be large and the slack tends to be large. Is. Therefore, the optical fiber is greatly vibrated under the influence of the wind pressure, and the optical fiber is easily damaged.

(C) Since it has a suspender and its outer shape is special, the laying work is extremely troublesome.

(D) Since the metal tube containing the optical fiber projects from the surface, it is susceptible to external influences such as lightning strikes and bird strikes, and the tube containing the optical fiber is easily damaged.

[0017]

SUMMARY OF THE INVENTION In view of such a situation, the present inventors have aimed to solve the above problems and realize an economical and highly reliable communication line associated with a power transmission line. I made an invention like this.

That is, "a space defined by a hollow tube is formed at or near the center of an overhead ground wire in which a plurality of bare metal wires having conductivity are twisted together,
An optical fiber composite overhead ground wire, characterized in that a single or a plurality of optical fibers are housed in the space. "
But that is it.

The overhead ground wire is not an overhead power transmission line itself, but is installed in parallel on a steel tower together with the overhead power transmission line.

The present invention is described in Japanese Patent Application No. 51-98348 (Japanese Patent No. 1395875), which is the original application of the present application.

As the bare metal wire used for the overhead ground wire, a metal wire having conductivity such as a galvanized steel wire, an aluminum covered wire or an aluminum wire is widely used. The inventors have confirmed that aluminum-steel coated wire should be selected, and will be described in detail below.

That is, galvanized steel wire or the like has a concern about corrosion resistance, and its long-term reliability is low as compared with an optical fiber, in particular, an optical fiber hermetically housed in a hollow tube, and an optical fiber composite using the same. In the overhead ground wire, there is a possibility that the optical fiber communication network will be broken due to the corrosion of the galvanized steel wire even though the optical fiber has no trouble.

Further, since the aluminum wire or the like is greatly expanded and contracted by thermal expansion and contraction and also greatly expanded by tension, there is a possibility that the optical fiber communication network may be broken due to the expansion of the aluminum wire.

Therefore, as long as these filaments are simply used as an overhead ground wire, they are governed by their own characteristics. When used in a composite overhead ground wire, it has been found that its properties pose a problem that limits the reliability of another important element, the optical fiber.

[0025]

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned problems and realize an economical and highly reliable communication line associated with a power transmission line. A hollow tube is twisted together with the bare metal wire of an overhead ground wire in which the bare metal wire is twisted, and a single or a plurality of optical fibers are provided in the space defined by the hollow tube. In the optical fiber composite overhead ground wire accommodated, an aluminum steel covered wire is selected as the bare metal wire.

Here, one or more optical fibers may be accommodated in parallel in the hollow tube, or may be accommodated in a twisted state.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail with reference to an explanatory view showing an embodiment.

In FIG. 1, 1 is a steel covered wire, 2 is a hollow tube such as an aluminum tube or a galvanized steel tube, and an optical fiber is inserted as shown in FIG.

FIG. 2 shows that the optical fiber 3 is accommodated in the hollow tube 2 together with the cushion material 4. By doing so, even if a sudden stress is applied to the hollow tube, it is possible to prevent the stress from being directly applied to the optical fiber due to the expansion and contraction of the cushion material.

Further, when the hollow tube is corrugated during manufacturing, the tube shrinks and the optical fiber is accommodated with an extra length. Therefore, even if tension is applied to the cable, the optical fiber does not break, The transmission characteristics are not impaired.

In this way, the hollow tube 2 containing a single or a plurality of optical fibers together with the cushion material is arranged inside the overhead ground wire, and a plurality of aluminum covered wires 1 are twisted together as shown in FIG. ing.

By disposing the hollow tube inside the aerial ground wire formed by twisting together the steel-covered wires of aluminum, there is no need for a suspending tool for integrating the aerial ground wire and the hollow tube, and Since it can be formed into a substantially circular shape, the work of laying it is easy, and it is less susceptible to external influences, and the reliability of the communication line formed by the optical fiber is increased.

[0033]

According to the optical fiber composite overhead ground wire of the present invention, the following remarkable effects can be obtained in addition to the effects achieved in the prior art.

(A) Since the optical fiber is installed in the overhead ground wire that does not receive voltage during steady operation, no special withstand voltage measures are required at the optical fiber draw-out portion, and power transmission is also stopped for maintenance of the optical fiber part. There is no need to do it and it is easy to handle.

(B) Since the overhead ground wire has a smaller current capacity requirement than a power transmission line, it can be made thin and slack. As a result, the influence of wind pressure is small and the amplitude is small,
Less likely to damage the optical fiber. In particular, since the optical fiber is housed in the hollow tube, it can be built into the aluminum steel wire with an arbitrary margin, and when the optical fiber is twisted or attached directly to the bare metal wire. The optical fiber is highly reliable without being damaged.

(C) Since the bare metal wire constituting the overhead ground wire is a steel covered wire, it has excellent corrosion resistance and tensile strength, and the bare metal wire limits the reliability of the communication line by the optical fiber. High reliability as a whole.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a partial example of FIG.

FIG. 3 is an explanatory diagram showing a technique at a previous stage of the present invention. 1 Bare metal wire 2 Tube 3 Optical fiber

Claims (1)

[Claims] 1. A hollow tube is twisted together with a bare metal wire of an overhead ground wire in which a plurality of bare metal wires are twisted together, and a hollow tube is twisted in the space defined by the hollow tube. An optical fiber composite overhead ground wire containing a single or a plurality of optical fibers, wherein the bare metal filament is an aluminum covered steel wire.