JPH0755749A - Monitoring equipment of damage of buried pipe - Google Patents

Abstract

PURPOSE:To shorten a distance from a transmission point to a reception point without shortening an interval of installation of ground bases. CONSTITUTION:Wires 12a and 12b for power supply and signals are buried along a buried pipe 11 and ground bases 13 are installed at proper places, while a terminal box 14 is installed at a proper place between the adjacent ground bases 13. A transmission means 15 for impressing an AC signal for monitoring on the buried pipe 11 and a monitoring means 16 for receiving signals from the wire 12b for signals are constructed on the ground base 13, while a reception means 17 for receiving the AC signal for monitoring from the buried pipe 11, detecting damage from the received signal and impressing a detection signal on the wire 12b for signals is constructed in the terminal box 14, and power is supplied to this reception means 17 from the wire 12a for power supply in this construction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damage monitoring device for a buried pipe.

[0002]

2. Description of the Related Art In excavation work, a buried pipe may be damaged by an excavating machine, and various damage monitoring devices have been proposed for monitoring this. As one of the conventional devices for monitoring such damage to the buried pipe, a monitoring AC signal is applied to the buried pipe to be monitored from the transmission point,
There is a monitoring device that receives this at a reception point distant from the reception point and detects the occurrence of damage to the buried pipe from the decrease in the reception voltage.

This monitoring device is shown in a conceptual explanatory view, for example, as shown in FIG. Reference numeral 1 is a transmitter for applying a monitoring AC signal to the buried pipe 2, and the transmitter 1 is provided at a transmission base 3 on the ground. The monitoring AC signal is, for example, 500 to 250.
An appropriate frequency such as 525 Hz or 2025 Hz is selected from the range of 0 Hz, and the applied voltage is appropriately set within the range of 1.0 to 4.0 V according to the installation environment of the buried pipe 2.

Reference numeral 4 denotes a receiving base installed on the ground at a position appropriately separated from the transmitting base 3 along the buried pipe 2, for example, a distance of 2 to 3 km, and a receiver 5 provided at the receiving base 4 separates the buried pipe 2 from the buried pipe 2. Receives the monitoring signal and receives its voltage (effective value)
The change is monitored.

That is, in the excavation work currently being carried out between the transmitting base 3 and the receiving base 4, when the conductive excavating blade 7 of the excavating machine 6 damages the insulating coating of the buried pipe 2, the damaged portion is excavated. Since it is grounded via the blade 7, the impedance of this portion is lowered and the monitoring AC signal leaks into the ground. Therefore, the reception voltage of the monitoring AC signal transmitted from the transmitter 1 to the receiver 5 via the buried pipe 2 is lowered,
By monitoring the decrease in the received voltage, damage to the buried pipe 2 can be detected and an alarm can be issued.

For example, FIG. 5 shows that a receiver 5 receives a simulated signal of damage by grounding a point of the buried pipe 2 with a conductor between the transmitting base 3 and the receiving base 4 at appropriate intervals. It shows the measurement result of the voltage level of the monitoring AC signal. In addition, this measurement was performed with the frequency of the monitoring AC signal being 2025 Hz in the buried pipe 2 whose distance from the transmitting point to the receiving point was 2.7 km.

As shown in FIG. 5, when a simulated signal of damage is given to the buried pipe, the received voltage of the monitoring AC signal received by the receiver 5 drops from the normal value V ₁ to V ₂ , and this It can be seen that damage to the buried pipe 2 can be detected by detecting the voltage drop using an appropriate method. For example, Japanese Patent Laid-Open No. 4-
Japanese Patent Laid-Open No. 194742 discloses a method of detecting the occurrence of damage by sampling a reception voltage for each unit time and comparing a voltage difference between adjacent sampling times with a set value.

[0008]

The above-mentioned monitoring method has the following problems. When viewed as a transmission line for a monitoring AC signal, the buried pipe has a large signal attenuation at a connection portion of magnesium as a galvanic anode, a buried portion in the ground, and the like. Therefore, the monitorable distance, that is, the distance between the transmitting base and the receiving base is limited.
However, it is often difficult to reduce the distance between the terrestrial transmitting base and the receiving base because the number of terrestrial bases is increased and installation costs are low. The AC signal for monitoring flowing through the buried pipe is mixed with a drain, external power, and other electrical noise, which causes a large fluctuation in the received voltage, causing voltage fluctuation due to noise to cause damage to the buried pipe. There is a risk of misidentification. In particular,
The drain is electrically a diode, and when it is turned on by passing a train or the like, the impedance for the monitoring AC signal suddenly drops, and the monitoring AC signal leaks therefrom, so that the received voltage fluctuates greatly. For example, FIG. 6 shows the measurement result of the voltage level of the monitoring AC signal in the receiving section when the train is frequently operated during the daytime and the drain is frequently operated. In excavating machines, especially boring machines, the ground resistance value at the time of damaging the insulating coating of the buried pipe may be large, and in this case, the voltage drop of the receiving part due to the damage is also small, so this voltage drop causes noise of There is a possibility that the damage may not be detected because it will be buried in the voltage fluctuation due to. The present invention has been made in view of the above points, and an object thereof is to reduce the distance between adjacent ground bases,
It is an object of the present invention to substantially reduce the distance between the transmitting point and the receiving point and reduce the attenuation amount of the monitoring AC signal.

[0009]

Means for solving the above-mentioned problems will be described with reference to FIG. 1 which conceptually shows an example of a damage monitoring apparatus to which the present invention is applied. Power supply and signal wires 12a, 12 along the pipe 11
b is buried, the ground station 13 is installed in a proper place, the terminal box 14 is installed in a proper place between the adjacent ground stations 13, and the ground base 13 has a transmitting means for applying a monitoring AC signal to the buried pipe 11. 15 and a monitoring means 16 for receiving a signal from the signal electric wire 12b, and a monitoring AC signal from the buried pipe 11 is received in the terminal box 14, and damage is detected and detected by the received signal. The receiving means 17 for applying a signal to the signal wire 12b is configured,
We propose a damage monitoring device for a buried pipe, which is configured to supply power to the receiving means 17 from the power supply wire 12a.

Further, the present invention proposes that the power supply wire 12a and the signal wire 12b in the above-mentioned structure are independently formed, or that common wires are used in a multiplexed manner.

Further, the present invention proposes that the receiving means 17 is configured to use a battery as a power source so that only the signal wire 12b is buried along the buried pipe 11.

[0012]

The AC signal for monitoring applied to the buried pipe 11 from the transmitting means 15 installed in the ground base 13 is received by the receiving means 17 installed in the terminal box 14, and the change of the voltage of the received signal is monitored.

Now ground station 13 and terminal box 1
When the buried pipe 2 is damaged by the excavating blade of the excavating machine between 4 and 4, the voltage of the monitoring AC signal received by the receiving means 17 decreases. When the voltage of the reception signal drops below a preset value, the reception means 17 detects the occurrence of damage and applies a predetermined detection signal to the signal wire 12b.

On the other hand, since the monitoring means 16 provided at the ground base 13 monitors the state of the signal on the signal wire 12b, when the receiving means 17 of the terminal box 14 generates a damage detection signal, it immediately This can be detected.

[0015]

Embodiments of the present invention will now be described with reference to the drawings.
As described above, FIG. 1 conceptually shows an example of the damage monitoring device to which the present invention is applied. An appropriate number of ground bases 13 are installed along the buried pipe 11 and the adjacent ground bases 13 are installed.
A terminal box 14 is installed in between, and a power wire 12a and a signal wire 12b are buried along the buried pipe 2.

In the figure, 1 is provided between adjacent ground stations 13.
Although an example in which one terminal box 14 is installed is shown, the number of installations may be plural. Also, the power supply wire 12a
The signal wire 12b and the signal wire 12b are installed on the upper side of the buried pipe 2 in the figure, but may be on the side or the lower side.

At each of the above-ground stations 13, a transmitting means 15 for applying a monitoring AC signal to the buried pipe 11 and a signal wire 12 are provided.
A monitoring means 16 for receiving a signal from b is installed, and a DC power supply 18 is installed in the ground base 13 on the left side of the drawing, and the DC power supply 18 is provided. The monitoring AC signal and its transmitting means 15 may have the same structure as the conventional one.

On the other hand, the receiving means 17 is installed in the terminal box 14. The receiving means 17 is connected to the buried pipe 11 and receives a monitoring AC signal;
That is, a portion that detects the damage to the buried pipe by comparing the voltage drop of the received monitoring AC signal with a set value, and a portion that outputs a detection signal to the signal wire 12b when the damage is detected,
The power supply wire 12a is connected to the power supply portion, and these can be configured by an analog circuit or a digital circuit.

For example, FIG. 2 shows an example in which the receiving means 17 is composed of an analog circuit. This circuit includes an amplifier circuit 19 connected to the buried pipe 11 and a band pass whose pass band is the frequency of the monitoring AC signal. Filter circuit 20 and detection circuit 2
1, a voltage comparison circuit 22, an output circuit 23 that outputs a predetermined detection signal to the signal wire 12b by the output of the voltage comparison circuit 22, and a power supply circuit 2 for supplying power to these circuits.
It is composed of 4 and.

In this configuration, the monitoring AC signal containing noise from the buried pipe 11 is first amplified by the amplifier circuit 19 to a predetermined level, and then the bandpass filter circuit 20 removes noise outside the band, and the detection circuit is detected. 21 obtains the voltage of the monitoring AC signal. Next, this voltage value is compared with the voltage comparison circuit 2
In 2, the threshold value is compared with the threshold value, and if the threshold value is exceeded, a predetermined detection signal is output to the signal wire 12b via the output circuit 23. It should be noted that the above-mentioned configuration of the receiving means 17 only shows basic elements, and elements such as the waveform shaping circuit are omitted.

Next, FIG. 3 shows a structure in which the receiving means 17 is composed of a digital circuit. This circuit comprises an amplifier circuit 19 connected to the buried pipe 11, an analog-digital conversion circuit 25, and an F-circuit.
It is composed of an FT circuit 26, a microcomputer 27, an output circuit 23, and a power supply circuit 24.

In this configuration, the monitoring AC signal containing noise from the buried pipe 11 is first amplified by the amplifier circuit 19 to a predetermined level, and then analog-digital converted by the analog-digital conversion circuit 25, and then the FFT circuit 26. input. After obtaining a digital signal corresponding to the monitoring AC signal from which noise components have been removed by a series of operations such as Fourier transform, removal of frequency components outside the frequency band of the monitoring AC signal, and inverse Fourier transform in the FFT circuit 26. , The voltage of the monitoring AC signal is obtained by the microcomputer 27, this voltage value is compared with a threshold value, and if it exceeds this voltage, a predetermined detection signal is output to the signal wire 12b via the output circuit 23. To do. It should be noted that the above-mentioned configuration of the receiving means 17 only shows basic elements, and elements such as a sample-hold circuit are omitted.

In the above construction, the detection signal output from the output circuit 23 to the signal wire 12b is a signal obtained by adding the identification signal of the terminal box 14 to the detection signal itself, so that the monitoring means 16 of the ground station 13 can It is possible to identify the terminal box 14 that has issued the damage detection signal, and thus help identify the damaged portion of the buried pipe 11.

Further, in the above embodiment, the power source electric wire 12a and the signal electric wire 12b are independently constructed, but if the signal is superposed on the power source electric wire 12a and shared, a pair of electric wires is provided. OK. If the battery for the receiving means 17 is stored in the terminal box 14, the power supply wire 12a can be omitted.

The monitoring AC signal may be an AC signal having a single frequency, or may be a plurality of AC signals having, for example, two kinds of frequencies. In the latter case, the transmitting means 15 of each ground station 13 applies the monitoring AC signals of a plurality of frequencies to the buried pipe 11, and the receiving means 17 of each terminal box 14 receives the plurality of monitoring AC signals. Alternatively, the transmitting means 15 and the receiving means 17 may handle the monitoring AC signals having different frequencies.

In the above embodiment, one terminal box 14 is installed between the adjacent ground stations 13, but a plurality of terminal boxes 14 can be installed.

[0027]

As described above, according to the present invention, the monitoring AC signal applied to the buried pipe from the transmitting means of the ground base is not received by the adjacent ground base to detect the damage, but the adjacent ground base is detected. Since the reception means installed in the terminal box installed between and detects the damage, it is possible to shorten the distance from the transmission point to the reception point without shortening the installation interval of the ground base, By thus reducing the attenuation amount due to the transmission distance of the monitoring AC signal, the damage detection performance of the buried pipe can be improved.

Further, since the signal for detecting the damage of the buried pipe by the receiving means of the terminal box is received and processed by the monitoring means of the ground base, the damage of the buried pipe can be monitored at the ground base.

[Brief description of drawings]

FIG. 1 is a conceptual explanatory diagram showing a configuration example of a buried pipe damage monitoring device according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration example of receiving means applied to the device of the present invention.

FIG. 3 is an explanatory diagram showing another configuration example of the receiving means applied to the device of the present invention.

FIG. 4 is an explanatory diagram showing a configuration example of a conventional buried pipe damage monitoring device.

FIG. 5 shows the measurement result of fluctuations in the reception voltage level of the monitoring AC signal in the reception section when a damage simulation signal is applied to the buried pipe in the configuration of FIG.

FIG. 6 is a diagram showing the measurement result of the voltage level of the monitoring AC signal in the receiving unit when the train is frequently operated during the daytime and the drain is frequently operated in the configuration of FIG. 4; is there.

[Explanation of symbols]

11 buried pipe 12a power supply wire 12b signal wire 13 ground base 14 terminal box 15 transmitting means 16 monitoring means 17 receiving means 18 DC power supply 19 amplification circuit 20 band pass filter circuit 21 detection circuit 22 voltage comparison circuit 23 output circuit 24 power supply circuit 25 analog-to-digital conversion circuit 26 FFT circuit 27 microcomputer

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[Procedure amendment]

[Submission date] August 23, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Added

[Correction content]

[Figure 4]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Added

[Correction content]

[Figure 5]

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Added

[Correction content]

[Figure 6]

Claims (4)

[Claims] 1. A power supply line and a signal line are buried along a buried pipe, a ground base is installed at a proper place, and a terminal box is installed at a proper place between adjacent ground bases, and a buried pipe is installed at the ground base. A transmitting means for applying a monitoring AC signal to
A monitoring means for receiving a signal from the signal wire is constructed, and a monitoring AC signal from the buried pipe is received in the terminal box, damage is detected by the received signal, and a detection signal is applied to the signal wire. And a receiving unit for supplying power from an electric wire for power supply to the receiving unit. 2. The apparatus for monitoring damage to a buried pipe according to claim 1, wherein the power wire and the signal wire are configured independently. 3. The apparatus for preventing damage to a buried pipe according to claim 1, wherein a common electric wire is used as the electric power wire and the signal electric wire. 4. A signal wire is buried along a buried pipe, a ground base is installed in a proper place, a terminal box is installed in a proper place between adjacent ground bases, and a ground pipe is used for monitoring in a ground base. The transmission means for applying an AC signal and the monitoring means for receiving a signal from the signal wire are configured, and in the terminal box, the monitoring AC signal from the buried pipe is received and the voltage of the received signal changes A receiving unit configured to detect damage and apply a detection signal to the signal wire,
Device for monitoring damage to buried pipe, characterized in that receiving means is configured to use a battery as a power source