JPH09281175A - Apparatus for searching cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately identify a specific cable in a short time with a small amount of energy by detecting pulse signals propagated in the cable with the use of a probe at a middle part of a laid route through electrostatic coupling. SOLUTION: A metallic shielding layer S as a conductor of the outermost layer of a cable 2A, 2B... 2N to be specified is exposed at an injection end. Code pulses are injected with a preliminarily set code proper to each cable between the layer S and the ground from a transmitter 30. A receiver main body 50 carries out searching from a predetermined distance while bringing a measuring electrode of a probe 40 into touch with a surface of the cable of an insulating layer or holding the measuring electrode in parallel to the surface of the cable. If a receiving sensitivity of one cable is larger by a significant difference than that of the other cables of the whole group of cables including the cable to be specified when the measuring electrode of the probe 40 is brought close to the surface of the cable, the one cable is judged as the cable to be specified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable detecting device for detecting a specific cable from a plurality of laying cables at an intermediate portion of a laying route.

[0002]

2. Description of the Related Art Hundreds to thousands of cables are laid in power plants, substations, and central control panels of plants.
These cables are connected to relevant electrical equipment throughout the site. These cables have lengths ranging from tens to hundreds of meters per cable, and are laid through the wall or floor of the building at the entrance to or exit from the building or room. Is done. Therefore, it is very difficult to visually detect a specific cable from a large number of cables in the middle of the cable laying route.

[0003] When repairing electrical equipment in the central control panel or in various places in the plant, a specific cable is detected at an arbitrary intermediate portion other than the control room, and the cable is cut or reconnected in accordance with the repair content of the electrical device. The need to connect often arises.

[0004] Broadly speaking, two types of this type of cable detection device are known: an electromagnetic induction type and an electrostatic coupling type.

In the electromagnetic induction type cable detecting device, as illustrated in FIG. 6, the conductor 4 of one cable 2 is used.
A sine wave voltage T is applied from one end to the ground 6 by the transmitter 8 and the other end of the conductor 4 is connected to the ground 6 to form a loop circuit in which a sine wave current circulates. At this time, the magnetic field generated around the cable 2 is detected by the search coil 12,
The detection output is measured by the receiver 14. A cable for which a measurement value having a significant difference from the detection outputs of other cables as the detection output at that time is obtained is identified as a cable for detection purposes.

Similarly, as an electromagnetic induction type cable detecting device, a device exemplified in FIG. 7 is known. In this case, 2
Using the two cables 2A and 2B, a sine wave voltage T is applied from the transmitter 8 between one ends of the conductors 4A and 4B of each cable, and the other ends of the conductors 4A and 4B are short-circuited by the conductor 10 to generate a sine wave. It forms a loop circuit in which the wave current circulates. In this case, when a sine wave voltage is applied, each cable 2
A magnetic field generated around A and 2B is applied to the search coil 12A,
12B and receivers 14A and 14B detect. A cable for which a measurement value having a significant difference from other cables as this detection output is obtained is identified as a cable for detection purposes. It is known that the detection output is displayed as a level using a bar graph, and a buzzer sounds when the level is equal to or higher than a predetermined value. A detection device of this type is known, for example, from JP-A-57-180304.

In the electrostatic coupling type cable detecting device, as shown in FIG. 8, a signal is transmitted between the outermost layer conductor at one end of one cable 2 (core wire 4 when it does not exist) and the ground 6. A sine wave voltage is applied from the machine 8 so that the other end of the conductor is insulated (floated) from the ground. As a result, an electric field generated around the cable 2 is applied to the receiver 2 from above the outermost insulating layer 16 of the cable 2 via the measuring electrode 18.
A cable for which a measurement value of 0 is obtained, and a measurement value of which is significantly different from that of other cables is identified as a cable for detection. A detection device of this type is known, for example, from Japanese Patent Application Laid-Open No. 7-270469.

[0008]

In the above-mentioned conventional apparatus, since a sine wave voltage is used as a measurement signal, there is a limitation on a usable frequency bandwidth, and there is a problem of frequency resolution. The number of cables that can be operated is limited. Furthermore, in the case of transmitting a sinusoidal voltage in the cable detection device of the electrostatic coupling type, in order to obtain the same electric field strength regardless of the cable length, energy or power that increases in accordance with the distribution capacity corresponding to the cable length is required. And

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a cable detecting device capable of performing a task of identifying a specific cable in a short time with a small amount of energy and a high accuracy even when a large number of cables are used.

[0010]

In order to solve the above problems, the present invention provides a cable detecting device for detecting a specific cable from a plurality of laying cables at an intermediate portion of a laying route. A transmitting means for injecting a pulse signal from the end injection part, a probe for detecting the pulse signal propagating through the cable in the middle part of the installation route by electrostatic coupling, and a receiving means for identifying a specific cable based on the detection output of the probe. It is characterized by having and.

As the pulse signal, a code-patterned pulse in which a different code is assigned to each cable can be used.

The pulse width of the pulse signal is preferably shorter than the propagation time.

It is preferable that the repetition period of the pulse signal is set to a value that is not substantially affected by the reflected pulse wave.

The pulses of a plurality of code patterns can be generated in a time-division manner while maintaining a synchronous relationship with each other.

[0015]

1 and 3 show an embodiment of the present invention. The device of the present invention comprises a combination of a transmitter and a receiver.
FIG. 3 shows each of the receivers.

The transmitter 30 shown in FIG. 1 comprises a power supply circuit 34, a code generator 36, and a switching circuit 38 housed in a case 32. The power supply circuit 34 receives a commercial power supply or a battery power supply as an input, outputs a DC voltage of several volts to several tens of volts, and supplies the DC voltage to the code generator 36 and the switching circuit 38. The code generator 36 generates a unique code pattern preset for each cable to be inspected, and inputs it to the code input terminal of the switching circuit 38. The switching circuit 38 has a number of code input terminals corresponding to the number of cables to be inspected, and output terminals corresponding to the number of code input terminals. Corresponding pulse voltages P1, P2
…, PN is output to each output terminal sequentially and cyclically in time division. The time width (pulse width) of each pulse is shorter than the propagation time. For example, if the cable length is 10
If it is 0 m, it may be about 0.1 to 10 μs (microsecond), and the voltage value may be about several volts to several tens of volts. In principle, (2
ⁿ −1) types of code patterns can be generated,
For example, if n = 8, 255 types of code patterns can be generated and up to 255 cables can be specified. FIG. 2A shows an example of a code pattern in which each bit is all "1", and FIG. 2B shows a bit arrangement of "1,0,1,1,0,1,0,1". Is shown.

By doing so, even when a plurality of cables are to be inspected, a plurality of code pulses do not overlap at each instant, and the receiving side synchronizes with the transmitting side as described later. There is no need, and cable identification is easy.

Regarding the equipment configuration on the receiver side, one probe is provided for one cable and a one-input type receiver main body, and one operator in the receiver main body switches the measurement target cable. Of the first type that moves the probe while switching the setting code patterns of
Prepare multiple sets of receivers consisting of one probe and one-input type receiver body connected to it according to the number of target cables, and set different code patterns of different cables for each receiver body. By placing it, a second type that allows multiple people to measure multiple cables simultaneously, a plurality of probes intended for simultaneous measurement of multiple cables, and a single-input type that is individually connected to each probe Of the third type including a plurality of receiver main bodies. The receiver of the first type sequentially switches the probe according to the cable to be measured and measures the code pattern setting of the receiver body accordingly. In the receiver of the second type, it is necessary to cyclically switch the code pattern setting in the receiver itself in synchronization with the transmitter. The receiver of the third type has a drawback that the installation cost of the device is somewhat high, but since the code pattern can be internally set according to the cable to be measured in advance, many cables can be quickly used by many operators. It is convenient when you want to identify.

The receiver shown in FIG. 3 is of the first principle type. This receiver is a probe 40
And a receiver body 50. Probe 40
Is functionally composed of a measuring electrode 42 for electrostatically coupling with the cable to be inspected, and a preamplifier 44 for amplifying the electric signal detected by the measuring electrode 42. The amplifier 44 is a case 48 with a shield 46 inside.
It is stored inside. The receiver main body 50 includes a power supply unit 5
2, an attenuator 54, a main amplifier 56, a code pattern setting switch 58, a discriminator 60, and a level indicator 62. Generally, the power supply unit 52 is preferably a battery power supply because the receiver is used as a portable device at a cable laying site. Probe 40 and receiver body 50
A multi-core connecting wire 70 is provided between the preamplifier 44 of the probe 40 and the output signal of the preamplifier 44 and the attenuator 54. Is supplied with operating power. Here, the output lines of the power supply unit 52 are not shown in order to avoid complication of the drawing. In the main body 50, the power supply unit 52 is composed of each component, that is, the attenuator 54, the main amplifier 56, the discriminator 6
The operating power is also supplied to 0 and the level indicator 62. Here again, those operating power supply lines are not shown.

The attenuator 54 is, for example, 0, 6, 14, 2
It is configured so that seven kinds of attenuation amounts of 0, 26, 34, and 40 dB can be switched and set, and switched and used according to the input signal level. 40, 34, 26, depending on the input signal level,
When it is displayed that the output of the discriminator 60 matches the preset code by sequentially switching to 20, 14, 6, 0 dB, the level is detected as the attenuation amount of the attenuator 54, and the level is indicated by the level indicator 62. indicate.

In the receiver, the electric field generated by the traveling wave pulse of the cable is detected by electrostatic coupling using the measuring electrode 42 of the probe 40. The detection signal is the preamplifier 4
It is amplified at 4 and guided to the receiver body 50. The detection signal guided to the receiver body 50 is attenuator 54 and main amplifier 5
It is inputted to the discriminator 60 via 6 as a measurement signal. Here, when the input pulse is equal to or more than a predetermined value, it is set by the code pattern setting switch 58 and input as the reference signal,
Determine if it matches the code pattern of the pulse injected into the cable to be identified. With the input level of the discriminator 60 set to a constant threshold value, the attenuation amount of the attenuator 54 is variously changed, and the maximum attenuation amount that the discriminator 60 determines to match is displayed as the reception sensitivity.

The transmitter 30, the probe 40, and the receiver main body 50 configured as described above are used by connecting to a cable as follows.

As shown in FIG. 4, the metal shield layer S, which is the outermost conductor of the cables 2A, 2B, ..., 2N to be identified, is exposed at the injection end, and each cable is transmitted from the transmitter 30 between this and the ground. A code pulse is injected with a unique code preset for each. In the case of a cable without a shield layer, the core wire of the cable may be used instead of the metal shield layer S. The low voltage side of both output terminals of the transmitter 30 and the case 32 are both grounded. If there are no shielded cables in parallel for some or all of the length,
Substitute the core of the cable to be specified and ground.

In the receiver body 50, the ground terminal is connected to the nearest ground terminal such as the building ground terminal. The measurement electrode 42 of the probe 40 is brought into contact with the surface of the cable made of an insulating layer, or the measurement electrode 42 is arranged in parallel with the surface of the cable and probed from a distance of several hundred mm. For all the cables in the cable group including the cables to be specified, the reception sensitivity when the measurement electrode 42 of the probe 40 is brought closer to the cable surface while keeping the same distance and angle is higher than that of other cables. When there is a significant difference, it is judged that this is the cable to be specified. According to the experiment, it was possible to determine the significant difference even if the measurement electrode 42 of the probe 40 was separated from the cable by about 200 mm.

The code pulse injected from the transmitter 30 propagates between the shield layer of the cable to be identified and the core wire, or between the shield layers of parallel cables. Although pulse propagation is used in the present invention, the pulse energy does not need to take into consideration the electrostatic capacitance when the propagation medium is viewed as a lumped constant circuit, and the characteristic impedance when the distribution medium is viewed as a distributed constant circuit (almost Tens of ohms) and some attenuation from the injection point to the specific operating point. Therefore, even in the case of a long cable, high-sensitivity measurement can be realized without lowering the sensitivity, so that it is not necessary to send out a high-energy signal which leads to a malfunction of the device.

As shown in FIG. 6, the first wave Pa1 of the code pulse injected from the transmitter 30 into the cable 2 at the injection end Ei propagates in the cable 2 and, if the opposite end Er is open, then there. When it returns to the measurement end after being reflected, it is slightly attenuated to become the second wave Pa2. Now, the time width of each pulse, that is, the pulse width Tb is shorter than the pulse propagation time Tp from the point (connection point of the transmitter 30) where the specific operation of the cable 2 to be specified is performed to the opposite end Er (that is, Tb < T
p)). In addition, when the injection period of the injection pulse, that is, the pulse repetition period Tr is set to be several times or more the pulse propagation time Tp (that is, several times Tr> Tp), the opposite end Er is obtained.
And, it is possible to make it hardly affected by a plurality of reflections at the injection end Ei. In the figure, Pa3 indicates the third wave, that is, the second reflected wave. Similarly the second
The injection pulse of the injection pulse Pb1 is indicated by Pb1, the first reflected wave of the injection pulse Pb1, that is, the second wave is indicated by Pb2, and the third wave is Pb2.
It is indicated by b3. The attenuation of the reflected waves Pm2 and Pn2 of the first injection pulses Pa1 and Pb1 when the opposite end Er is short-circuited is relatively small.

Assuming that the cable length is 100 m, the pulse propagation speed is usually about 100 to 200 m / μs, so the pulse propagation time Tp is 1 to 2 μs, and the pulse width Tb is 1 μs or less. However, if the pulse repetition period Tr is set to 6 μs or more, the influence up to the third wave can be hardly received. Therefore, it is possible to perform measurement by grounding / ungrounding the other end Er of the cable 2 or any other termination method, for example, any impedance termination of L, C, and R, and far end operation is also required.

In the conventional sinusoidal signal injection method, the frequency band that can be used is limited, and the number of cables that can perform a specific task at the same time is considerably limited due to the problem of frequency resolution. By using the converted pulse signal, the limitation of the frequency band can be virtually eliminated. In addition, it is easy to determine a plurality of code patterns, and high accuracy and a significant reduction in time can be expected in specifying cables for a large number of cables.

In the same manner, it is possible to specify not a single cable but a cable group in which a plurality of cables are bundled as a unit.

It is also possible to prepare a plurality of receivers for one cable and specify the cables at a plurality of points on the one cable.

According to the embodiment described above, the following actions and effects can be achieved. 1. The pulse width of the injection pulse can be made shorter than the propagation time of the reflected wave, so that a high-precision cable identification operation can be efficiently performed with low power. 2. The opposite end of the cable can be measured in any state of ground, open, L, C, and R terminations, and no far-end operation is required. 3. By coding the injection pulse, the S / N ratio can be improved and the measurement accuracy can be improved. 4. By coding the injection pulse, the number of cables that can perform a specific work at the same time can be virtually unlimited, and the time required to specify a large number of cables can be significantly shortened. 5. Since the energy of the pulse propagating in the cable is determined by the surge impedance almost without being influenced by the cable length, it is possible to perform the specific work without lowering the sensitivity even when the long cable is specified. 6. If the cable to be specified has a shielding layer, it is possible to work in a live state.

[0032]

As described above, the pulse width of the injection pulse is made shorter than the propagation time of the reflected wave, whereby the cable specifying work with high accuracy can be efficiently performed with a small power. Moreover, the opposite end of the cable can be measured in any state of grounding, open, and L, C, and R termination, and the far end operation can be eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram of a transmitter according to the present invention.

FIG. 2 is an explanatory diagram showing an example of a code pattern generated in the transmitter of FIG.

3 is a block diagram of a receiver used in combination with the transmitter of FIG.

FIG. 4 is an explanatory diagram for explaining an operation of a transmitter and a receiver according to the present invention.

FIG. 5 is an explanatory diagram for explaining the behavior of a reflected wave when a pulse signal is injected into the cable.

FIG. 6 is a device layout diagram showing a first example of a conventional electromagnetic induction type cable detection device.

FIG. 7 is a device layout diagram showing a second example of a conventional electromagnetic induction type cable detection device.

FIG. 8 is a device layout diagram showing an example of a conventional electrostatic coupling type cable detection device.

[Explanation of symbols]

 2, 2A, 2B Cable 4, 4A, 4B Conductor 6 Earth 8 Transmitter 10 Conductor 12, 12A, 12B Antenna 14, 14A, 14B Receiver 16 Measurer 18 Insulation layer 20 Measuring electrode 22 Receiver 30 Transmitter 32 Case 34 Power supply circuit 36 Code generator 38 Switching circuit 40 Probe 42 Measuring electrode 44 Preamplifier 46 Shield 48 Case 50 Receiver body 52 Power supply section 54 Attenuator 56 Main amplifier 58 Code pattern setting switch 60 Discriminator 62 Level indicator 70 Connection line

Claims (5)

[Claims] 1. A cable detecting device for detecting a specific cable from a plurality of laying cables at an intermediate portion of a laying route, and transmitting means for injecting a pulse signal into the specific cable from a near-end injecting section, Cable detection, comprising a probe for detecting a pulse signal propagating through a cable at an intermediate portion of a laying route by electrostatic coupling, and a receiving unit for identifying the specific cable based on a detection output of the probe. apparatus. 2. The cable detection device according to claim 1, wherein a code-patterned pulse in which a different code is assigned to each cable is used as the pulse signal. 3. The cable detection device according to claim 1, wherein the pulse width of the pulse signal is shorter than the propagation time. 4. The cable locating device according to claim 1, wherein the repetition period of the pulse signal is set to a value which is substantially unaffected by the pulse reflected wave. 5. The cable detection device according to claim 1, wherein a plurality of code pattern pulses are generated in a time division manner while maintaining a synchronous relationship with each other.