JP2003241040A - Water-immersion and wire-breaking sensor cord and cable having the same installed therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-immersion and wire-breaking sensor cord which can detect both a water-immersion accident and a wire-breaking accident by itself with high precision without any misdetection, and to provide a cable for electric power, communications, etc., which is inexpensive and can bring about improved operation efficiency in laying operations when the water-immersion and wire-breaking sensor cord is incorporated and used. <P>SOLUTION: One water-immersion and wire-breaking sensor cord 20 is incorporated between insulating cores 13 accommodated in a jacket sheath 14 of the cable 10. An expansion pressure press sheath 23 covering a water-absorptive swelling material 22 on an optical fiber 21 is molded into a high-rigidity cylinder by using a hard material such as HDPE to withstand the expansion pressure when the water-absorptive swelling material 22 increases in volume by absorbing rainwater. The expansion pressure operates as lateral pressure on the optical fiber 21 and light loss caused by backward scattered light and reflected light is detected. If the cable 10 is broken, light pulses incident on the optical fiber 21 of the water-immersion and wire-breaking sensor cord 20 are shut off as propagation is lost. A monitor detects that and the occurrence and place of the wire-breaking accident are confirmed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water breakage disconnection sensor code for detecting intrusion of rainwater or the like and detecting a breakage, and a power / communication cable incorporating the same.

[0002]

2. Description of the Related Art Electric power / communication cables (generally referred to as "cables" below) for urban overhead lines and seabeds are designed to promptly recover from a flood or wire breakage accident due to rainwater or seawater. It is set up to constantly monitor and monitor which area and place the spillage occurred. Conventionally, it is known that a cable has a built-in sensor cord for detecting such a water break.

FIG. 4 is a cross-sectional view showing a conventional example of such a cable with a sensor cable for inundation breakage. This cable 1
Is based on a structure in which a conductor 2 such as a copper wire is coated with an insulator 3 to form an insulating core 4, and, for example, three of the insulating cores 4 are housed inside an outer sheath 5. . In the space between the three insulated wire cores 4, two pairs of the infiltration sensor cord 6 and the disconnection sensor cord 7 are housed, and a total of four pairs are accommodated.

As shown in FIG. 5, which is a single unit, the water immersion sensor cord 6 is formed by covering a conductor 6a such as a copper wire with an insulator 6b. The insulator 6b is penetrated at regular intervals in the cord length direction. A through hole 6c for taking in water is provided, and the conductor 6a is exposed to the outside from the through hole 6c. Therefore,
When rainwater or the like enters the outer sheath 5 of the cable 1, the rainwater intrudes from any one of at least one of the two water sensor cords 6 through the through hole 6c and comes into contact with the conductor 6a. The insulation resistance value of the conductor 6a in the portion in contact with the rainwater decreases and changes. Or two inundation sensor cords 6
The insulation resistance value between the respective conductors 6a changes and is detected by a monitoring system that constantly monitors it to confirm the inundation accident and the occurrence point.

The disconnection sensor cord 7 may be an optical fiber into which light, which should be referred to as sensor light, enters from its input end, or an electric wire through which current, which is also referred to as sensor current, flows. Therefore, when a disconnection accident occurs in the cable 1 and the disconnection sensor cord 7 is disconnected, the disconnection accident and the occurrence point are detected by detecting the continuity of light or current and detecting it by the monitoring system which is constantly monitoring. To confirm.

On the other hand, as another conventional example, JP-A-62-2
There is an optical fiber water immersion detection sensor disclosed in Japanese Patent No. 62803. In this case, it is disclosed that the outer circumference of the optical fiber is covered with a water absorbing and swelling material, and a braid made of metal or plastic is coated thereon. As its application, one end side of the sensor is connected to the water infiltration detection system, and the other end side is arranged on every floor where power communication equipment is installed in a structure such as a building. For example, when a flood accident occurs on the floor of the area A, the water absorbing and swelling material of the optical fiber water immersion detection sensor arranged there comes into contact with the invading water to expand the volume, and the expansion pressure is applied to the optical fiber as a lateral pressure. Optical fiber undergoes partial bending and microbending under lateral pressure, and the optical loss due to backscattered light and reflected light at that time is measured by optical time domain reflectometry (OTDR method).
It is designed to confirm the occurrence of the flood accident and the location of the occurrence by the detection by.

[0007]

By the way, FIG. 4 and FIG.
The former cable 1 indicated by has the following problems. One is a problem with the water immersion sensor cord 6. Since this is a method of detecting a change in insulation resistance of the conductor 6a in contact with rainwater, the length of the water immersion sensor cord 6 becomes longer as the cable laying distance increases, and the farther the inundation occurrence point becomes, the further the conductor becomes. This means that the detection accuracy of the insulation resistance value of 6a is reduced. Further, particularly when the cable 1 is for electric power, it is strongly affected by noise due to the influence of the electric field, and the detection accuracy and detection capability of the water are reduced, making it difficult to specify the water immersion position. As described above, there are practical problems. One is that, in addition to the above-mentioned water immersion sensor cord 6, a wire breakage sensor cord 7 is separately provided, and at least two sensor cords are required to have both the water immersion and wire breakage detection functions. Is. In the example shown in the figure, a total of four are arranged in the vacant space for the purpose of detecting water breakage. Therefore, incorporating a large number of such sensor cords in the outer sheath 5 of the cable 1 requires a considerably high level of technology in terms of manufacturing, resulting in an overall increase in cost, as well as workability during laying work on site. There are some drawbacks.

On the other hand, the latter optical fiber water immersion detection sensor disclosed in Japanese Patent Laid-Open No. 62-262803, which is another conventional example, has the following problems. One is that a metal or plastic "braid" is used which is coated from above the water-swelling material. It is disclosed that the side pressure received from the water absorbing and swelling material is pressed inward in the radial direction within the range in which the infiltrated water can be taken in by using the finest stitch as possible. However, if some external pressure or external force is applied to the entire sensor while it is being installed and used on each floor of a building, the strength of the braid is not enough to withstand such external pressure and external force and not bend. It tends to be. As a result, there is no possibility of a water immersion accident, and the optical fiber receives lateral pressure due to external pressure or external force even though the water-absorption swelling material does not generate expansion pressure. high. One is that the optical fiber water immersion detection sensor is premised on the detection of water infiltration, and it may be used by laying it on a long object such as a power / communication cable that needs to be monitored for water leakage. First, it does not consider the function of detecting disconnection accidents, which should be taken into consideration.

In view of the above, an object of the present invention is to provide a water immersion disconnection sensor code capable of detecting both a water immersion accident and a wire disconnection accident with high accuracy and without erroneous detection. An object of the present invention is to provide a cable for electric power / communication, which is low in cost and can improve workability during installation work.

[0010]

In order to achieve the above-mentioned object, a flooded disconnection sensor cord 20 according to a first aspect of the present invention has an optical fiber 21 and an optical fiber 21, as shown in FIG. A water absorbing and swelling material 22 which covers the outer periphery and gives a swelling pressure to the optical fiber 21 as a lateral pressure when the water is in contact with infiltrated water and expands in volume; and the water absorbing and swelling material having rigidity higher than the swelling pressure. The expansion pressure pressing sheath 23 is formed into a cylindrical shape that covers the outer circumference of the cylindrical shape 22, and has a vertical slit 23a that is formed by cutting out a part of the cylindrical shape and extending in the cylinder length direction.

Therefore, the sensor cord 2 for this water breakage
0 works as follows. For example, the cable 10 shown in FIG. 1 is used by incorporating only one wire breakage sensor cord 20 over the entire length of a long object such as an electric power / communication cable that requires constant monitoring of water breakage accidents. During laying and use, light which should be called sensor light is incident on the optical fiber 21 from one end. When water such as rainwater penetrates into the expansion pressure holding sheath 23 through the vertical slits 23a and comes into contact with the water absorbing and swelling material 22, the water absorbing and swelling material 22 absorbs water and expands in volume, and the expansion pressure acts on the optical fiber 21 as a lateral pressure. . At the same time, the expansion pressure acts to push the expansion pressure pressing sheath 23 outward as well, but the expansion pressure pressing sheath 23 holds the expansion pressure with a rigidity sufficient to withstand it. Therefore, the swelling pressure generated in the water absorbing and swelling material 22 acts on the optical fiber 21 as a sufficient lateral pressure. Optical fiber 2
1 receives back pressure and locally generates backscattered light and reflected light. By detecting the light loss due to backscattered light with a monitor that constantly monitors, for example,
Confirm that the communication cable was inundated by rainwater and the location where it occurred.

On the other hand, when a long monitoring object such as an electric power / communication cable breaks / breaks in the middle of it, the built-in water break sensor cord 20 also breaks / breaks at the same time, and the light incident on the optical fiber 21 is broken. The pulse is cut off and reaches zero. By detecting it with a monitor that constantly monitors it, it is possible to confirm that a wire disconnection accident has occurred and the location of the accident.

Further, in the water breakage disconnection sensor cord according to a second aspect of the present invention, the material of the expansion pressure holding sheath 23 is high density polyethylene.

From the above, the expansion pressure holding sheath 23 is HD
By molding a rigid material such as PE (high-density polyethylene) into a highly rigid cylinder, the expansion pressure holding sheath 23 can be pushed outward by the expansion pressure when the water absorption swelling material 22 absorbs water such as rainwater and expands in volume. However, you can hold it down. As a result, the swelling pressure of the water absorbing and swelling material 22 is effectively applied to the optical fiber 21 as a lateral pressure, and the optical loss due to backscattered light or reflected light partially generated in the optical fiber 21 due to the lateral pressure is detected. The expansion pressing sheath 23 made of HDPE has a rigidity that does not give an unintentional lateral pressure to the optical fiber 21 due to bending deformation even when some external pressure or external force is applied from the outside, and plays a role of a protective cover. ing. Therefore, it is effective to prevent erroneous detection when no flood accident actually occurs.

A cable 10 according to a third aspect of the present invention, as shown in FIG. 1, accommodates a plurality of insulating cores 13 inside an outer sheath 14, and the insulating cores 13 are contained. It is characterized in that it is configured to accommodate the water immersion disconnection sensor cord 20 according to claim 1 between them.

From the above, the cable 10 operates as follows. By accommodating only one of the above-mentioned inundation breakage sensor cords 20 in the space between the insulated wire cores 13, it is possible to have both a detection function of inundation accident and a disconnection accident. While the cable 10 is being laid, the sensor cord 20 for water breakage
Light that should be called sensor light is incident on the optical fiber 21 from the input end. When rainwater or the like enters the inside of the sheath 14 of the cable 10, the rainwater enters the breakage sensor cord 20 through the vertical slit 23a of the expansion pressure holding sheath 23. The infiltrated rainwater comes into contact with the water-swelling and swelling material 22 and expands in volume, and the expansion pressure is increased by the optical fiber 21.
And acts on the inflation pressure holding sheath 23. Since the expansion pressure holding sheath 23 has high rigidity, the expansion pressure holding sheath 23 withstands the deformation caused by the expansion pressure and spreads it. Thereby, the optical fiber 2
On the other hand, the expansion pressure of the water-swelling and swelling material 22 effectively works as a lateral pressure for the case of 1. The optical fiber 21 locally generates backscattered light and reflected light by receiving lateral pressure. By detecting the light loss due to the backscattered light and the like with a monitor that constantly monitors, it is confirmed that an inundation accident such as rainwater has occurred in the cable 10 and the occurrence point.

Further, when the cable 10 is broken in the middle thereof, the sensor cable 20 for water breakage is simultaneously broken and the optical pulse incident on the optical fiber 21 is cut off from conduction and becomes zero. By detecting it with the monitor, it is confirmed that the disconnection accident has occurred in the cable 10 and the occurrence point.

Therefore, in this cable 10, as shown in FIG.
As is clear from comparison with the conventional cable 1 of
Since only one inundation breakage sensor cord 20 is required, the structure is simplified, the cost can be significantly reduced, and the workability at the laying work site can be improved.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a water breakage disconnection sensor cord and a cable incorporating the same according to the present invention will be described below in detail with reference to the drawings. Figure 1
Is a cable 10 for power or communication of the present embodiment.
FIG. Insulator 1 on conductor 11 such as copper wire
2 is applied to form the insulated core 13, and the insulated core 13 is formed.
The cable 10 is configured by accommodating, for example, three of them inside the outer sheath 14 by twisting them. In addition, the insulated core 13 inside the sheath 14
In the space between and, a single wire breakage sensor cord 20 according to the present embodiment is housed.

As shown in FIGS. 2 (a) and 2 (b), the water breakage disconnection sensor cord 20 has an optical fiber 21 as a core wire and a water-swelling / swelling material 22 coated on the outer periphery thereof, and the water-swelling / swelling material 22 is entirely covered. The circumference is covered and an expansion pressure holding sheath 23 is provided. The expansion pressure holding sheath 23 is made of HDPE.
A high-rigidity material such as (high-density polyethylene) that has high rigidity in terms of hardness and mechanical strength is used, and is molded like a cylinder having a required wall thickness. Further, the expansion pressure holding sheath 23 is formed with a single vertical slit 23a which is formed by cutting out a part of the cylinder circumference and extending in the cord length direction. When the rainwater or the like enters the outer sheath 14 of the cable 10, the vertical slits 23a are provided to take in the water into the sensor cord. That is, the infiltrated water such as rainwater taken in from the vertical slit 23a is brought into contact with the water absorbing and swelling material 22 inside.

Here, as described above, the material for the expansion and pressure holding sheath 23 is selected from a material having high rigidity such as HDPE for the following reason. When water such as rainwater taken into the lateral pressure holding sheath 23 from the vertical slit 23a comes into contact with the water absorbing and swelling material 22, the volume of the water absorbing and swelling material 22 expands, and the expansion pressure acts on the optical fiber 21 as a lateral pressure. At the same time, the expansion pressure acts to expand the expansion pressure holding sheath 23 to the outside and elastically deform it. Expansion pressure holding sheath 23
Is expanded to the outside because the expansion pressure of the water absorbing and swelling material 22 escapes to the outside, so that the lateral pressure due to the expansion pressure does not work sufficiently on the optical fiber 21. Since the initial purpose cannot be achieved as a sensor code for detecting a water infiltration accident, the sensor cord is provided with rigidity and waist strength sufficient to withstand and hold down the expansion pressure of the water absorbing and swelling material 22.

The water absorbing and swelling material 22 for generating the swelling pressure
Here, the material and thickness are not particularly limited here, but any material can be used as long as it can absorb water and apply a lateral pressure required for volume expansion to the optical fiber 21.

The water-corruption sensor cord 20 composed of the above-mentioned members has the optical fiber 2 with the cord end side as the input end.
An optical pulse, which should be called a sensor light, is incident on the optical system 1 and the optical loss caused by the backscattered light and the reflected light of the optical pulse in the monitoring system is measured by the optical time domain reflectometry
n Reflectometry: OTDR).

Next, when one of the inundation disconnection sensor cords 20 is built in and used in the cable 10 such as an overhead power line, it operates as follows. When rainwater or the like permeates through the cable connection portion or the relay portion and enters the inside of the sheath sheath 14 during laying use, the water is leaked from the vertical slit 23a into the expansion pressure holding sheath 23 of the water leakage disconnection sensor cord 20. It is captured. The infiltrated water taken into the sensor cord comes into contact with the water absorbing and swelling material 22 and is absorbed. The water absorption swelling material 22 expands in volume, and the expansion pressure acts as a force to act on the inner optical fiber 21 as a lateral pressure. On the other hand, at the same time, the expansion pressure pressing sheath 23 is also expanded outward and elastically deformed.

Since the expansion pressure holding sheath 23 has such rigidity that it is pressed down without being elastically deformed to the outside even when receiving the expansion pressure from the water absorbing and swelling material 22, the expansion pressure becomes a sufficient lateral pressure as a reaction. It acts on the optical fiber 21. The optical fiber 21 bends under lateral pressure, and the resulting optical loss is detected by the monitor in the monitoring system, and the occurrence of flooding in the cable 10,
It is possible to judge which area or position of the laid overhead wire the inundation point is.

On the other hand, at one of the overhead lines, the cable 10
When the cable breaks, the continuity of the optical pulse as the sensor light that is incident on the optical fiber 21 is cut off, so that it is detected by the monitor of the monitoring system, and the cable break accident occurs and the breakage accident. It is possible to judge which area and position of the laying overhead line.

Next, in order to confirm the detection accuracy of the water immersion disconnection sensor cord 20 of this example, a sample incorporated in the cable 10 was prepared, and an experiment for detection of water immersion and disconnection was conducted by the above OTDR measurement method. The experimental samples are (A) normal cable without water immersion and breakage, and (B) 30 from the cable end.
A water immersion test cable in which a through hole for taking in water is formed in the outer sheath 14 at a position of m (m);
(C) Three types of breaking test cables were prepared, which were broken at a position 30 m from the cable end.

3 (a) to 3 (c) show the above (A) to (c).
For the three types of experimental cables of (C), the horizontal axis is the cable length (m) and the vertical axis is the reflected light amount (dB), and the experimental cable (A) is normal, the experimental cable (B) 3 is a graph in which the characteristic change of the waveform of the optical pulse is measured when the lateral pressure is applied by and the disconnection is caused by the experimental cable (C).

As a result, the waveform at the normal time in the experimental cable (A) shown in FIG. 3 (a) was 30 m from the cable end.
Since there is no hole or disconnection at the position, the reflected light amount shows a proportional attenuation with a gradual inclination as the cable length increases and the distance increases.

In the experimental cable (B) shown in FIG. 3 (b), when the lateral pressure is applied, the amount of reflected light sharply decreases at a position 30 m from the end of the cable. In this case, water is injected from a through hole opened at a position 30 m from the end of the cable assuming water intrusion, and the water enters the water intrusion sensor cord 20 through the vertical slit 23 a of the expansion pressure holding sheath 23. It contacts the water-swelling material 22. The water-swelling material 22 expands in volume, and the expansion pressure acts as a lateral pressure of the optical fiber 21. The light loss in the portion that receives this lateral pressure appears as a sudden decrease in the amount of reflected light, which is the result of monitoring it by the OTDR measurement method. In this way, it has been proved that the inundation breakage sensor code 20 accurately detected the inundation that occurred at the position of 30 m of the cable 10 by the monitor.

In the experimental cable (C) shown in FIG. 3 (c), the waveform at the time of disconnection is 30 m from the cable end.
The amount of reflected light is zero at the position. In this case, the measurement was performed at a position 30 m away from the end of the cable. That is, if the wire is disconnected at a position 30 m from the end of the cable, the sensor cable 20 for water breakage is also broken at that position,
This shows that the conduction of the optical pulse as the sensor light incident on the optical fiber 21 has been cut off, and it has been verified that the water breakage disconnection sensor code 20 accurately detected it.

As is clear from the above, by incorporating one of the sensor cables 20 for water breakage into the cable 10,
It is possible to highly accurately detect at which position of the cable 10 the water flood or the wire breakage has occurred. One of the reasons why this is possible is that the expansion and pressure holding sheath 23 that covers the water absorbing and swelling material 22 from the outside is formed into a cylindrical shape with a material having rigidity and rigidity such as HDPE. In addition, the high rigidity of the expansion pressure holding sheath 23 means that the cable 1
When 0 is laid for overhead lines, it is effective in suppressing unintentional bending or bending of the expansion pressure holding sheath 23 under the influence of some external pressure under the laying environment. That is, it is possible to avoid erroneous detection when acting on the optical fiber 21 as if the inflation pressure pressing sheath 23 was unintentionally bent and deformed, as if it was the inflation pressure from the water absorbing and swelling material 22. Such a great advantage of the expansion pressure holding sheath 23 of this example cannot be obtained by the braid disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 62-262803. In addition, 1 of the sensor cable 20
The advantage of using only books is that FIG.
It is also clear when compared with the one composed of a large number of lines shown in FIG.

The characteristic graphs of the amount of reflected light shown in FIGS. 3 (a) to 3 (c) are for the purpose of demonstrating whether the positions of occurrence of flooding and wire breakage can be accurately detected by the wire breakage sensor code 20 of this example. For this purpose, an optical fiber 21 called a GI optical fiber having a large attenuation was used with a short distance of 30 m from the cable end as a measurement point. Actually, the optical pulse is not attenuated at 30 m from the end of the cable. For example, assuming a railway cable, SM (Simple-Mode)
) If an optical fiber with a small attenuation called an optical fiber is used, it is possible to apply the water immersion disconnection sensor cord 20 of this example by incorporating it in a cable up to 1000 m long.

Further, in the water breakage disconnection sensor cord 20 of this example, if the material of the optical fiber 21 is taken into consideration as described above, the detection accuracy is lowered even when the laying length of the cable 10 is long. Don't worry. On the other hand, in the case of the water immersion sensor cord 6 shown in FIG. 5 of the conventional example, since it has a structure in which a current, which should be called a sensor current, is passed through the conductor 6a to detect the insulation resistance, The problem that the detection accuracy of the insulation resistance value becomes lower as it gets worse can be solved.

[0035]

As described above, the sensor cable for inundation breakage according to the first aspect of the present invention is one cord over the entire length of a long object such as an electric power / communication cable which needs to be constantly monitored for intrusion accidents. When water such as rainwater infiltrates into the expansion and pressure holding sheath through the vertical slits and comes into contact with the water absorbing and swelling material, the water absorbing and swelling material absorbs water and expands in volume, resulting in the expansion pressure of the optical fiber. At the same time, the expansion pressure acts to spread outwardly against the expansion pressure holding sheath, but the expansion pressure holding sheath holds down the expansion pressure with a rigidity enough to withstand it. Therefore, the swelling pressure generated by the water swelling material acts as a sufficient lateral pressure on the optical fiber, and the optical fiber locally receives the lateral pressure to locally generate backscattered light or reflected light. By detecting the light loss due to the backscattered light etc. with a monitor that constantly monitors, for example, it is confirmed that a flood accident due to rainwater etc. has occurred in the power / communication cable and the occurrence point. In addition, if a long monitoring object such as a power / communication cable breaks or breaks in the middle of it, the built-in water break sensor cable also breaks or breaks at the same time, and the optical pulse incident on the optical fiber breaks the conduction. It falls to zero. By detecting this with a monitor that constantly monitors, it is possible to confirm that a disconnection accident has occurred and the location of the accident.

In the sensor cable for water breakage and breakage according to a second aspect of the present invention, the expansion / pressing sheath is formed of a hard material such as HDPE (high density polyethylene) into a highly rigid cylindrical shape, so that the water absorbing / swelling material absorbs water such as rainwater. Then, the expansion pressure pressing sheath tries to push the expansion pressing sheath outward by the expansion pressure when the volume is expanded, but it can be pressed. As a result, the swelling pressure of the water-swelling material is effectively applied to the optical fiber as a lateral pressure, and the optical loss due to the backscattered light or the reflected light partially generated in the optical fiber due to the lateral pressure is detected. HDPE
The expansion pressurizing sheath has a rigidity that does not give an unintentional lateral pressure to the optical fiber due to bending deformation even when some external pressure or external force is applied from the outside, and plays a role of a protective cover. Therefore, it is effective to prevent erroneous detection when no flood accident actually occurs.

Further, in the cable according to the third aspect of the present invention, only one of the above-mentioned inundation disconnection sensor cords is housed in the space between the insulated wire cores to detect both inundation accident and disconnection accident. It can have a function. In other words, if rainwater enters the inside of the sheath of the cable,
The rainwater penetrates into the sensor cord of the water pressure breakage through the vertical slit of the expansion pressure holding sheath and contacts the water absorbing and swelling material to expand the volume.The expansion pressure acts on the optical fiber and the expansion pressure holding sheath, but the expansion pressure holding is suppressed. Since the sheath has high rigidity, the sheath resists the deformation caused by the expansion pressure and presses it down, and the expansion pressure of the water absorbing and swelling material effectively acts as a lateral pressure on the optical fiber. The optical loss due to the backscattered light generated by the optical fiber under lateral pressure is constantly monitored and detected by a monitor to confirm the occurrence of inundation accidents such as rainwater and the location where it occurred. In addition, when the cable is disconnected, the sensor cable will be disconnected at the same time and the optical pulse incident on the optical fiber will be cut off to zero, and by monitoring it, a cable disconnection accident will occur. You can see what you did and where it occurred. Therefore, even if this cable is compared with the same type of cable as the conventional example, only one of the sensor cables for water breakage is required, so the structure is simple and the cost can be significantly reduced, and the workability at the laying work site etc. Is also increased.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an inundation disconnection sensor cord and a cable incorporating the same according to an embodiment of the present invention.

2 (a) and 2 (b) are a cross-sectional view and a perspective view showing a single unit of the sensor cable for water breakage of the same embodiment.

3 (a) to 3 (c) are an experimental cable in a normal state in which a sensor cable for inundation breakage of the same embodiment is incorporated, and an inundation experiment cable in which water is inundated at a position of a cable end of 30 m; It is a characteristic graph which similarly shows the correlation of a cable length and the amount of reflected light about each of the disconnection test cables in which the cable end 30 m was disconnected.

FIG. 4 is a cross-sectional view showing, as a conventional example, a cable in which a plurality of water immersion sensor cords and a plurality of wire breakage sensor cords are incorporated.

FIG. 5 is a perspective view showing only a water immersion sensor cord of the conventional example.

[Explanation of symbols]

10 cables 11 conductors 12 insulator 13 insulated wire core 14 sheath 20 Inundation disconnection sensor code 21 optical fiber 22 Water swelling material 23 Inflation pressure sheath 23a Vertical slit

Claims (3)

[Claims] 1. An optical fiber, a water absorbing and swelling material which coats the outer periphery of the optical fiber, and gives a swelling pressure to the optical fiber as a lateral pressure when the swelling is brought into contact with infiltrated water to expand the volume. An expansion pressure-holding sheath having a large rigidity and formed into a cylindrical shape that covers the outer circumference of the water-swelling and swelling material, and has a longitudinal split slit that is formed by cutting out a part of the circumference of the cylindrical shape and extending in the cylinder length direction. Inundation disconnection sensor cord characterized in that 2. The sensor cord for inundation breakage according to claim 1, wherein the material for the expansion pressure holding sheath is high density polyethylene. 3. The outer sheath is configured to accommodate a plurality of insulated wire cores, and the inundation breakage sensor cord according to claim 1 is housed between the insulated wire cores. cable.