JPH0755751A - Noise-suppressing method in damage-monitoring system for buried pipe - Google Patents

Abstract

PURPOSE:To enable reliable detection of the damage of a buried pipe caused by an excavating blade of an excavator. CONSTITUTION:In a noise-suppressing method, a passing filter 7 for the frequency of an AC signal for monitoring is connected in parallel to a drainage 6 connected to a buried pipe 2, in a system the AC signal for monitoring impressed on the buried pipe 2 in a transmission part 1 is received in a reception part 3 located apart from the transmission part 1 and the damage of the buried pipe 2 is monitored on the basis of a reception signal. Accordingly, the noise due to the operation of the drainage 6 out of electric noise nixing in the buried pipe 2 can be suppressed, and therefore disadvantages that the fluctuation of a received voltage caused by that noise may be detected falsely as the damage, and that the fluctuation of the received voltage caused by the damage may not be detected, can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise suppressing method in a damage monitoring system 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 systems have been proposed for monitoring this. As one of the conventional systems for monitoring the damage to the buried pipe, an AC signal for monitoring is applied from the transmitter to the buried pipe to be monitored, and this is received by a receiver that is distant from the receiver, and the received signal is received. There are monitoring systems that detect the occurrence of damage to buried pipes due to voltage drops.

This monitoring system is shown in a conceptual explanatory view as shown in FIG. 4, for example. Reference numeral 1 is a transmitter, and the transmitter 1 applies a monitoring AC signal to the buried pipe 2.
The monitoring AC signal is, for example, 525 from the range of 500 to 2500 Hz.
A suitable frequency such as Hz or 2025 Hz is selected, and the voltage is appropriately set and applied in the range of 1.0 to 4.0 V according to the installation environment of the buried pipe.

Reference numeral 3 denotes a receiver installed at a position appropriately separated from the transmitter 1, for example, a position of the buried pipe 2 separated by 2 to 3 km, and the monitoring AC signal transmitted from the transmitter 1 is received by the receiver 3. It is received at and is monitored by the fluctuation of the received voltage (effective value).

That is, when the conductive excavating blade 5 of the excavating machine 4 damages the insulating coating of the buried pipe 2 in the excavation work currently being carried out between the transmitting section 1 and the receiving section 3, the damaged portion thereof is damaged. Is grounded through the excavating blade 5, the impedance of this portion is lowered and the monitoring AC signal leaks into the ground. For this reason, the reception voltage of the monitoring AC signal in the receiving unit 3 decreases, so that the damage to the buried pipe 2 can be detected by monitoring the decrease in the reception voltage.

For example, FIG. 5 shows the monitoring in the receiving unit 3 when a simulated signal of damage is given by grounding one point of the buried pipe 2 between the transmitting unit 1 and the receiving unit 3 with a conductor at appropriate intervals. It shows the measurement result of the voltage level of the AC signal for use. In addition, this measurement is performed from the transmitter 1 to the receiver 3.
In the buried pipe 2 with the distance to 2.7 km, the frequency of the monitoring AC signal was set to 2025 Hz.

When a simulated signal of damage is given to the buried pipe as shown in FIG. 5, the received voltage at the receiving section is a normal value V ₁
From To decreases to V _2, it can be seen that can detect damage to the buried pipes by detected using the voltage drop appropriate method. For example, Japanese Laid-Open Patent Publication No. 4-194742 discloses a method of detecting the occurrence of damage by sampling a received voltage for each unit time and comparing a voltage difference between adjacent sampling points 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 distance between the transmitter and the receiver, that is, the monitorable distance is limited. 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 also suddenly drops, and the monitoring AC current leaks from the impedance, causing a large fluctuation in the received voltage. For example, FIG. 7 shows 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 drainage device is frequently operated. It can be seen that the received voltage fluctuates greatly due to the operation of the device. 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 it is an object of the present invention to suppress the generation of noise due to the operation of the drainage device with a simple configuration.

[0009]

Means for solving the above problems will be described with reference to the drawings conceptually showing an example of a damage monitoring system to which the present invention is applied.
First, the monitoring AC signal applied to the buried pipe 2 in the transmitter 1 is received by the receiver 3 distant from the transmitter 1,
In a system for monitoring the damage of the buried pipe 2 by the received signal, a noise suppression method is proposed in which a pass filter 7 for the frequency of the monitoring AC signal is connected in parallel with the drain 6 connected to the buried pipe 2.

Then, the present invention proposes that in the above method, the pass filter 7 is constituted by an LC series resonance circuit as shown in FIG.

Further, according to the present invention, the buried pipe 2 is provided in the transmitter 1.
In the system in which the receiving AC signal for monitoring applied to the receiving unit 3 is received from the transmitting unit 1 and the damage of the buried pipe 2 is monitored by the received signal, the drain 6 connected to the buried pipe 2 is used. A noise suppression method is proposed in which a blocking filter 8 for the frequency of the monitoring AC signal is connected in series.

Then, the present invention proposes that the blocking filter 8 in the above method is constituted by an LC parallel resonance circuit as shown in FIG.

[0013]

In the configuration in which the pass filter 7 for the frequency of the monitoring AC signal is connected in parallel with the drainer 6, the impedance of the drainer portion with respect to the monitoring AC signal is ON / OFF of the drainer 6. It is always kept at a low value regardless of. Therefore, the voltage fluctuation of the monitoring AC signal due to ON / OFF of the drainage device 6 can be suppressed low. The pass filter 7 does not hinder the operation of the drainage device 6.

The pass filter 7 can be easily constituted by an LC series resonance circuit in which the resonance frequency is set to the frequency of the monitoring AC signal.

In the configuration in which the blocking filter 8 for the frequency of the monitoring AC signal is connected in series with the drainer 6, the impedance of the drainer portion for the monitoring AC signal is
It is held at a high value even when the drainage device 6 is ON. At this time, the blocking filter 8 does not hinder the operation of the drainage device 6. In this way, the drainer portion is always kept in a high impedance state with respect to the monitoring AC signal regardless of whether it is ON or OFF, so that the voltage fluctuation of the monitoring AC signal due to ON or OFF is suppressed to a low level. be able to.

The blocking filter 8 can be easily constructed by an LC parallel resonance circuit in which the resonance frequency is set to the frequency of the monitoring AC signal.

[0017]

FIG. 1 conceptually shows an embodiment of the present invention, in which a drain filter 6 is connected in parallel with a pass filter 7 and a blocking filter 8 is connected in series. As described above, in the present invention, either one of the pass filter 7 and the blocking filter 8 may be connected as described above, or both of them may be connected.

Further, the specific circuits of the filters 7 and 8 can be appropriately constructed. That is, the pass filter 7
Can be configured as a band-pass filter including the frequency of the monitoring AC signal in the band, or can be configured as a high-pass filter including the frequency of the monitoring AC signal in the pass band, and the blocking filter 8 is used for monitoring. In addition to being configured as a band elimination filter that includes the frequency of the AC signal within the band, it can be configured as a low-pass filter that does not include the frequency of the monitoring AC signal within the pass band.

[0019]

As described above, the present invention provides a system for receiving a monitoring AC signal applied to a buried pipe in a transmitter at a receiver remote from the transmitter and monitoring the received signal for damage to the buried pipe. Of the electrical noise that is mixed in the buried pipe, the noise caused by the operation of the drain can be suppressed, so the fluctuations in the received voltage caused by this noise can be mistakenly detected as damage or There is an effect that it is possible to prevent the occurrence of inconvenience such that the fluctuation of the received voltage due to the error cannot be detected.

[Brief description of drawings]

FIG. 1 is a conceptual explanatory diagram showing a configuration example of a buried pipe damage monitoring system to which the method of the present invention is applied.

FIG. 2 is a circuit diagram showing a configuration example of a pass filter applied to the method of the present invention.

FIG. 3 is a circuit diagram showing a configuration example of a blocking filter applied to the method of the present invention.

FIG. 4 is a conceptual explanatory diagram showing a configuration example of a buried pipe damage monitoring system.

FIG. 5 is a diagram showing a measurement result of fluctuations in a reception voltage level of a monitoring AC signal in a reception unit when a damage simulation signal is applied to a buried pipe in the system of FIG.

FIG. 6 is the end of train operation in the system of FIG.
6 shows the measurement result of the reception voltage level of the monitoring AC signal in the reception unit when the drainer is not operating at all.

FIG. 7 is a diagram showing the measurement result of the voltage level of the monitoring AC signal in the receiving unit in the system of FIG. 4 when the train is frequently operated in the daytime and the drain is frequently operated. is there.

[Explanation of symbols]

 1 transmitter 2 buried pipe 3 receiver 4 excavator 5 excavator blade 6 drainer 7 pass filter 8 blocking filter

Claims (4)

[Claims] 1. A system for receiving a monitoring AC signal applied to a buried pipe in a transmitter at a receiver remote from the transmitter and monitoring the received signal for damage to the buried pipe, the system being connected to the buried pipe. Noise suppression method in a damage monitoring system for buried pipes, characterized in that a pass filter for the frequency of the monitoring AC signal is connected in parallel with the existing drainer. 2. The noise suppressing method in a damage monitoring system for a buried pipe, wherein the pass filter according to claim 1 is composed of an LC series resonance circuit. 3. A system for receiving a monitoring AC signal applied to a buried pipe in a transmitter at a receiver remote from the transmitter and monitoring the received signal for damage to the buried pipe by connecting to the buried pipe. Noise suppression method in a damage monitoring system for a buried pipe, characterized in that a blocking filter for the frequency of a monitoring AC signal is connected in series with an existing drainage device 4. A noise suppressing method in a damage monitoring system for a buried pipe, wherein the blocking filter according to claim 3 is constituted by an LC parallel resonance circuit.