JPS6043606B2 - electric cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electric cables for power or communications installed in the air, along a survey, buried directly underground, on the seabed, etc., and particularly relates to electric cables for power or communication purposes that are installed in the air, along a road survey, buried directly underground, or on the seabed. This invention relates to an electric cable that can detect external injuries, accident locations, etc. accurately in a short period of time.

In general, there are many accidents in which underwater power cables installed on the ocean floor, for example, end up with dielectric breakdown or are torn off by a ship's anchor or the like.

In the case of the former accident due to abrasion of the protective layer, it is impossible to maintain long underwater cables that extend several thousand meters underwater, and the current situation is that the damage is only known after dielectric breakdown occurs. be. Underwater cables that have suffered dielectric breakdown should be repaired and reused, but in order to detect the accidental part, it is necessary to inspect a route that is several thousand meters long, such as by diving a dipper to the bottom of the water. It was extremely difficult to detect the accident area. Furthermore, in the case of the latter accident in which the underwater cable was cut, the Murray loop method was not used for detection, making it difficult to detect the accident point. Similarly, there is no quick, easy, and satisfactory method for finding damaged locations not only for underwater cables but also for other electrical cables. This invention was made in view of the above-mentioned circumstances, and it is possible to accurately and quickly locate the accident location, both when the cable is damaged by damage that leads to insulation breakdown, and when the cable is completely severed. The purpose is to provide an electric cable that can be detected by time.

This invention is characterized by the fact that optical fibers are very strong against tension in the longitudinal direction but weak against impact forces such as extreme bending, can be coated with plastic and even with this, are extremely thin, and have good insulation. Focusing on the fact that the optical fiber has properties such as no risk of insulation deterioration or corrosion even when used underwater, we developed an optical fiber that runs along the length of the cable in the outermost coating layer of the electrical cable. By incorporating this feature, if the cable suffers an injury or accident, the optical fiber in this part will be cut, and by measuring the light reflection characteristics at the cut surface of this optical fiber, the location of the injury or accident can be accurately determined in a short time. It was completed after gaining knowledge that it could be detected.

That is, the present invention provides an electric cable in which optical fibers are integrally arranged in the outermost coating layer of the cable along the longitudinal direction of the cable, and when the optical fibers are damaged or cut due to external injury, accident, etc., the position of the optical fibers is fixed. This is an electrical cable that appears as a light reflection characteristic, making it possible to quickly detect damage to the cable and the location of an accident.

Hereinafter, basic embodiments of the present invention will be explained with reference to FIGS. 1 and 2.

FIG. 1 shows a single-core CV insulated power cable, in which an insulating layer 2 and an anti-corrosion sheath 3 are provided in this order around the outer periphery of a conductor 1.
The optical fiber 4 is integrally embedded in the anti-corrosion sheath 3 along the longitudinal direction of the cable.

Figure 2 mainly shows power cables laid on the ocean floor.
The protective layer 6 provided on the outer layer is formed by collectively forming fiber-reinforced plastic linear bodies, and the optical fiber 4 is connected to the protective layer 6.
The figure shows the fiber-reinforced plastic linear body forming the fiber-reinforced plastic linear body.

Note that the insertion portion of the optical fiber of the electric cable according to the present invention may be placed in the outermost sheath or near the sheath. Further, the number of optical fibers is not limited to one location, and as described above, the above-mentioned sections may be combined to form a plurality of sections, and the number of optical fibers is appropriately selected depending on the importance of the line. Furthermore, the present invention is not limited to the cross-linked polyethylene insulated cables shown in FIGS. 1 and 2, but can also be applied to other rubber or plastic insulated cables, and there is no need to incorporate optical fibers into 0F cables, etc. It can be applied because it can be done without any problems. FIG. 3 shows an explanatory diagram of a method for detecting damage and accident positions on underwater cables according to the present invention.

In FIG. 3, 11 is an underwater cable incorporating an optical fiber 4, 12 is an optical system having a half mirror 13, and 14
1 is an optical filter, 15 is a cathode ray tube oscilloscope, 16 is a semiconductor laser, and 17 is a pulse generator. When the optical fiber 4 is cut at a distance x from one end of the optical fiber 4 integrated with the underwater cable 11, the optical pulse signal modulated by the pulse generator 17 is transmitted to the half mirror of the optical system 12. 13 and enters the optical fiber 4 from one end. The light incident on the optical fiber 4 is reflected at its cutting point 4a, and is reflected again by the half mirror 13.
Sent to 4. The light is converted into an electrical signal by the optical detector 14, and this electrical signal is observed by the oscilloscope 15 to measure the time from the incident pulse until the reflected pulse is obtained.
By measuring this time, the distance x from one end of the optical fiber 4 to the cutting point 4a can be measured in a short time using the following equation. However, C: speed of light in vacuum, n: refractive index of the optical fiber, Tx: time from incident Parnos to obtaining reflected pulse on the oscilloscope. The results of a comparative test between the cable according to the embodiment of the present invention and a comparative cable without an optical fiber were as shown in the following table.

The test cable in the above table has the structure shown in Figure 1, with a conductor diameter of 12 Tr$t, an insulating layer outer diameter of 20 Twt, an anti-corrosion sheath outer diameter of 26 mm (thickness 3 bars), and an optical fiber with an outer diameter of A mill with a glass core diameter of 125 μm and a coating material of nylon was used.

As is clear from the above table, the embodiment of the present invention can detect the defect position with considerable accuracy, and compared to the conventional Murray loop method, the defect position can be accurately measured regardless of the insulation resistance of the cable defect. We were able to further shorten the detection time.

As described in detail above, the present invention has optical fibers disposed in the outermost coating layer of the cable along its longitudinal direction, so that damage to the cable due to damage to the cable, cutting of the optical fiber due to an accident, etc. We can provide an electrical cable that can accurately measure and analyze the cut position in a short time of less than 0.1 hour, and in particular can accurately detect the position even if the cable is completely cut, which was previously impossible. There is an effect.

In addition, since the optical fiber is placed in the outermost coating layer of the cable, if the outermost coating layer of the cable is worn out, the optical fiber will break, making it possible to quickly detect the state of cable wear and prevent major accidents from occurring. It can be prevented and prompt repairs can be made.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing different embodiments of the electric cable according to the present invention, and FIG. 3 is a cross-sectional view showing a method for detecting damage and accident locations on underwater cables according to the present invention. It is a diagram. 1...Conductor, 2...Insulating layer, 3...
・Anti-corrosion sheath, 4... Optical fiber, 5...
...Inclusions, 6...Protective layer consisting of fiber-reinforced plastic linear bodies.

Claims (1)

[Claims] 1. In an electric cable, optical fibers are integrally arranged in the outermost coating layer of the cable along the longitudinal direction of the cable, and damage to the outermost coating layer, accidents, etc. can cause damage to the optical fibers. An electrical cable characterized in that the location of damage or breakage appears as a light reflection characteristic, making it possible to detect damage to the cable or the location of an accident. 2. The electric cable according to claim 1, wherein the optical fiber is embedded in the cable sheath layer. 3. The electric cable according to claim 1, wherein an optical fiber is arranged in a fiber-reinforced plastic linear body that is a constituent material of a fiber-reinforced plastic linear body layer forming the outermost layer of the cable.