JPH0535388B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a cable accident inspection method that accurately detects the point of failure without error when an accident such as conductor breakage occurs in a power cable or the like. This is related to the method of output.

<Conventional technology> Conventionally, in order to locate an accident point in a power cable, one or more optical fibers are inserted into a part of the cable, that is, under the cable sheath, to detect accidents such as cable breakage. Cables have already been proposed for detecting fault points in the cable due to abnormalities in the optical fiber, such as breakage. An example of this is shown in Figure 3, where 1 is a conductor, 2 is an insulator, 3 is a barrier layer, 4 is a sheath (corrosion protection layer), and 5... is the above-mentioned accident inspection placed under the sheath. It is an optical fiber for use. Due to this abnormality in the optical fibers 5..., a cable fault point is detected.

<Problems to be Solved by the Invention> However, according to this cable, the insertion position of the optical fiber for detecting an accident point is closer to the outside under the sheath, so the following problem occurred.

(1) On the outside of the cable, the optical fiber alone may break along with the sheath etc. due to damage to the inside of the cable during transportation, bending during installation, or expansion and contraction after installation. Abnormalities could occur due to bending, and this could be mistaken for an accident with the cable itself, such as a broken conductor. That is, even a small accident such as an external injury may be mistakenly detected as a major accident involving the cable itself, such as a breakage of a conductor.

(2) In addition, in the event of a cable accident, even if there is no major abnormality in the sheath or other parts of the outer sheath, the conductor may break inside the cable (ground fault, etc.), and this may be detected on the outside of the cable. However, the monitoring position of the accident point was insufficient.

<Means for Solving the Problems> The present invention has been made in view of such conventional problems, and its characteristic configuration is that the central part of a cable conductor such as a power cable or the vicinity thereof,
A cable containing one or more optical fibers is installed in or near the sheath, an optical fiber failure point detector is connected to the optical fiber of the cable, and the optical fiber is connected to the optical fiber in the longitudinal direction of the optical fiber. By sending optical pulses from the fault point detector, and receiving the reflected light of the optical pulses from the abnormal part of the optical fiber at the time of an accident in the cable, by the optical fiber fault point detector,
This method not only detects whether the cable is a conductor part, a sheath part, or both parts, but also detects the point of the accident.

<Function> Since the optical fibers are placed in or near the center of the cable conductor and in or near the sheath, any abnormality in these optical fibers can cause an accident to occur, as well as to which part of the cable the accident occurred. The accident point (position) can also be detected with high accuracy.

<Example> Figure 1 shows a power cable used in the present invention, in which 11 is a conductor, 12 is an insulator, 13 is a shielding layer,
14 is a sheath, 15... is a plurality of optical fibers placed under the sheath 14 as in the conventional case, and 16a is a conductor 1.
The optical fibers 16b, . . . , inserted into the center of the conductor 11 are a plurality of optical fibers inserted around the outer periphery of the conductor 11.

In this cable, the optical fibers 16a, 16b... inserted in the center of the conductor and its vicinity mainly serve to detect accidents (major accidents) inside the cable such as conductor breakage, and the optical fibers 15... inserted under the sheath It works to detect accidents (small accidents) on the outside of the cable, such as damage to the sheath. Note that the number of each optical fiber is not particularly limited, but from the viewpoint of detection accuracy, it is desirable to have the number of optical fibers in this embodiment.

The cable configured as described above is installed in a desired installation route, and then, in the present invention, as shown in FIG. 2, optical fiber failure point detectors 17 are connected to optical fibers 16a, 16b, . do.

According to the method of the present invention, when detecting a fault point in a cable or periodically monitoring it, the optical fiber fault point detector 17... detects a fault point in the optical fiber 15..., 16a, 16b... A pulse is sent to receive the Rayleigh scattered light that occurs within the optical fiber and the Fresnel reflected light that occurs at the accident point.

In this state, if an abnormality (Fresnel reflection, optical attenuation) is observed only in (1) the optical fibers 15..., it is considered that there is damage to the sheath etc., that is, a small accident point is detected. (2) If an abnormality is found only in the optical fibers 16a, 16b..., it is likely that the conductor has broken, etc., although this is a stage before the accident has spread to the entire cable, which means that a major accident point inside the cable has been detected. be done. Furthermore, by identifying abnormalities between the optical fiber 16a at the center of the conductor and the optical fiber 16b at the periphery of the conductor, it is possible to more precisely determine the state of the accident. (3) Optical fiber 15... and optical fiber 16
If an abnormality is found in both cables 16a, 16b, etc., it is considered that the conductor breakage is progressing considerably, that is, a major fault point affecting the entire cable is detected.

<Effects of the Invention> As is clear from the above explanation, according to the method for detecting fault points of cables according to the present invention, major accidents such as conductor breakage are mainly detected in cable accidents.
In some cases, an excellent effect can be obtained in that the detailed accident condition can be detected quickly and accurately by distinguishing it from a small accident such as damage to the cable sheath.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the optical fiber-containing cable used in the present invention, FIG. 2 is a schematic explanatory view showing the connection between the optical fiber of the cable and the optical fiber failure point detector, and FIG. FIG. 2 is a vertical cross-sectional view of a conventional optical fiber cable. In the figure, 11... conductor, 12... insulator, 14...
... Sheath, 15, 16a, 16b... Optical fiber, 17... Optical fiber failure point detector.

Claims (1)

[Claims] 1. Laying a cable containing one or more optical fibers in or near the center of a cable conductor such as a power cable, and in or near the sheath,
An optical fiber failure point detector is connected to the optical fiber of the cable, and a light pulse is sent from the optical fiber failure point detector in the longitudinal direction of the optical fiber to detect an abnormal part of the optical fiber at the time of an accident of the cable. By receiving the reflected light of the above-mentioned light pulse etc. by the above-mentioned optical fiber failure point detector, it is possible to detect whether it is a cable conductor part, a sheath part, etc.
Alternatively, a cable fault point detection method that detects both parts and also detects the fault point.