JPS6034706B2 - Accident point detection method for cables in pipelines - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for detecting a fault point in a cable in a conduit.

If a grounding accident occurs due to a hole in the corrosion protection layer or insulator of a direct underground cable, the point of the accident can be detected relatively easily as follows.

That is, as shown in FIG. 1, at one end of the cable 1, its metal sheath connects between the conductor and earth a DC power supply 2 and a switch 3 placed in series with the power supply, which is periodically to open and close.

As a result, one constant periodic pulsed DC power is applied between the metal sheath or conductor and the ground. On the other hand, the operator holds a center-zero microvoltmeter 5 with a pair of rod-shaped electrodes 4 arranged at appropriate intervals and connected to input terminals, and while piercing the electrodes 4 into the ground, connects them from the power supply connection end to the other end. move towards. The micro voltmeter 55 indicates 0 at the fault point, and when it passes this point, it reaches the fault point and becomes the opposite point from before. Therefore, if you closely examine the vicinity immediately after the instruction is reversed, you can accurately locate the accident point. However, although the above detection method is effective when the ground surface is solid and can be penetrated by an electrode, it cannot be applied when the ground is paved with asphalt, concrete, etc. Moreover, the cable is an in-duct cable,
If the ground surface is concrete or asphalt pavement, it is completely impossible to detect the accident point using the above detection method. The present invention has been made in view of the above circumstances, and provides a detection method capable of detecting fault points in cables in conduits.

The invention will be explained in detail below with reference to the drawings.

In FIG. 2B, 6 is a manhole, and 7 is a conduit that accommodates the cable 8 where the accident occurred. Also, 9 is the pipe line 7
The empty conduit adjacent to is shown. The pipes 7 and 9 are filled with water. At this time, the pipe mouth waterproofing device 1 at both ends of the pipe line 7 acts as a seal. A cover 12 is attached to one end of the empty conduit 9, into which a detection wire 11, which will be described later, is inserted watertightly and with limited movement. A simple lid is attached to the other end. Detection line 11
is a two-core cable, and each core wire is uniformly connected to the input terminal of the micro voltmeter 13 at the center zero.

Further, both core wires are terminated at the end with an interval of, for example, about 50 skins, and the conductor is exposed at each terminal 14. (Figure 2A). As described above, the detection line is gradually fed into the empty conduit 9 from the cover 12.

Since the pipe line 7 and the empty pipe line 9 are filled with water, the cable 8 in the pipe line 7 has the same electrical relationship with the earth as if it were buried directly underground, and the empty pipe line 9 Conductor exposed terminal 1 inside
4 has the same electrical relationship with the ground as the rod-shaped electrode 4 shown in FIG. Therefore, if a pulsed DC voltage is applied to the cable 8, the point of failure can be detected by the 0 indication of the microvoltmeter 13. As described above, according to the present invention, even if the ground surface is paved and the cable is in a conduit, the accident point can be easily detected.

In addition, in Fig. 2, when both the empty pipe line 9 and the pipe line 7 have appropriate moisture, the detection line shown in Fig. 3 can be used to locate the accident point without filling each pipe with water. Detection can be performed. That is, as shown in FIG. 3A, a spherical weight 15 made of a conductor such as brass is connected and fixed to the core conductor at each core wire terminal 14 of the detection wire. If such a detection wire is used, the core conductor of the detection wire will maintain electrical contact with the inner surface of the empty conduit 9 via the weight 15, and will have the same electrical contact with the electrode rod 4 and the ground in FIG. have a relationship.

On the other hand, if there is moisture inside the conduit 7, it is the same as if the cable 8 is buried directly in the ground, and the micro voltmeter 13
The accident point can be known from the instruction 0. FIG. 3B shows a modification in which a water supply hose 16 is provided in parallel with the detection line.

If the moisture inside the empty pipe line 9 is not sufficient, water can be supplied from the hose 16 to improve the contact between the weight 15 and the inner wall of the empty pipe line 9. Incidentally, if the moisture in the conduit 7 housing the cable 8 is not sufficient, the conduit 7 may be filled with water as in the embodiment shown in FIG.

Furthermore, when carrying out the above-mentioned invention, if a long strip of bamboo, a wire, etc. used for inserting the detection wire into the pipe is used for passing the pilot wire through the pipe, the detection wire can be prevented from breaking. Smooth insertion can be achieved.

The detection lines shown in FIG. 2A and FIGS. 3A and 3B can also be used to detect a fault point in a large number of cables installed in a bit.

In other words, if you insert a detection line into a bit where many wires are installed and drag its terminal inside the bit, the microvoltmeter will indicate 0.
The point of failure can be determined by In this case, it is assumed that the faulty cable is known in advance and a pulsed DC voltage is applied from the end of the cable.

[Brief explanation of drawings]

Fig. 1 is a vague diagram of a fault point detection method for direct underground cables, Fig. 2A is a front view of an example of a detection line used in the present invention, and Fig. 2B is a bush type diagram of an example of the detection line used in the present invention. 3A is a front view of another example of the detection line used in the present invention, and FIG. 3B is a front view of a modification thereof. 7... Conduit, 8... Cable, 9... Empty conduit, 11...
Detection line, 13... Microvoltmeter, 15... Weight, 16
...Water supply hose o Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. Detection of two core wires in an empty conduit parallel to the conduit containing the cable in which the accident occurred, the ends of which are spaced apart in the longitudinal direction, and the core conductor is exposed at each end. draw a line,
A method of detecting a fault point by applying voltage between the cable sheath or conductor and the ground where a fault has occurred, and using the fact that when the fault point enters between the two terminals, the voltage between both terminals becomes zero. Accident point detection method. 2. The method for detecting a fault point in a cable in a conduit according to claim 1, wherein both the conduits are filled with water. 3. The method for detecting a fault point in a cable in a conduit according to claim 1, characterized in that a detection line is used in which a conductive weight is connected and fixed to each core conductor at the detection line terminal. 4. The method for detecting a fault point in a cable in a conduit according to claim 3, characterized in that the conduit containing the faulty cable is filled with water. 5. The method for detecting a fault point in a cable in a conduit according to claim 3 or 4, characterized in that water is injected to a weight at the terminal of the detection line.