JP2001356177A - Buried cable investigating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a buried cable investigating method capable of executing easily conveyance, installation and operation, and executing position detection of a buried transmission cable with high precision. SOLUTION: In this buried cable investigating method, a feeble alternating- current magnetic field generated from the transmission cable buried underground is measured on the ground surface by a magnetic field measuring device, and the buried position of the transmission cable is calculated from the measured value of the magnetic field. In the method, each magnetic field in the horizontal and vertical directions (biaxially) relative to the transmission cable is measured simultaneously respectively by two sensors installed separately at a fixed interval in the vertical direction, and the planar position of the transmission line is investigated based on the measured result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for exploring a buried cable. More specifically, the present invention relates to a buried cable exploration method for detecting the burial depth of a transmission line buried underground using an electromagnetic induction phenomenon.

[0002]

2. Description of the Related Art With respect to buried objects such as gas pipes, water pipes, sewer pipes, and power cables once buried underground, the buried articles are repaired or new ones are placed near the buried articles. When constructing a buried object, it is necessary to check the buried position of the existing buried object. A buried object marking system is known as a technique for easily detecting the buried position from the ground without excavating these buried objects on site.

In a buried object marking system, when a buried object is buried in the ground, information on the buried position of the buried object is stored in advance in a wireless tag and attached to the buried object, so that it can be used during construction. In this case, it is possible to obtain the depth information of the buried object by making the wireless tag respond to the electromagnetic wave and reading the buried position information stored in the wireless tag by the wireless device on the ground. However, the depth of buried objects is not always constant, and often changes over time due to natural and artificial environmental changes such as the occurrence of crustal deformation and road maintenance. Therefore, since only the depth at the time of burying can be obtained by the above-mentioned method, there is a problem that when the depth of the buried object changes, the accurate depth of the buried object at present cannot be measured.

[0004] In the operation of power equipment, technologies and know-how have been accumulated from the viewpoint of predictive maintenance and preventive maintenance, and are implemented when a failure or defect is found in power transmission equipment buried underground. Repair work,
There has been a strong demand for the development of an exploration method for accurately measuring the position of underground equipment such as power transmission cables buried underground without digging. Similar to the above-mentioned buried object marking system, for the purpose of detecting the position of an buried object underground, a physical exploration method has been proposed in which physical quantities relating to the crust and the buried object are measured and an underground structure is estimated from the measured values. As a geophysical exploration method, the electromagnetic induction method, the underground laser method, or
The application of these combined methods has been studied.

In the electromagnetic induction method, a secondary magnetic field generated from a pipe is measured by a receiving magnetic sensor by indirectly applying an induced magnetic field from a magnetic field transmission source to an underground object.
This is a physical exploration method that detects the horizontal and vertical positions of the buried pipeline from changes in measured values. The electromagnetic induction method is subdivided into various methods depending on the positional relationship between the magnetic field transmission source and the receiving magnetic sensor, the installation position of the receiving magnetic sensor, the direction of the measured magnetic field, the method of estimating the position of the buried object, etc. In order to perform high-precision measurement in the presence of extraneous noise, it is necessary to prepare a large-scale magnetic field transmission source, especially in urban areas where the external noise is large,
Depending on the measurement environment such as a building or a road, there is a problem that it is difficult to secure an installation place or to transport the device.

The underground radar method is a technique for imaging an underground structure by utilizing the reflection, refraction, and transmission phenomena of an electromagnetic wave of 10 MHz or more. In the underground radar method, like the electromagnetic induction method, the problem of external noise,
Securing the installation place of the measuring device and the difficulty of transporting the device remain as problems to be solved.Furthermore, when targeting a buried object at a deep position, the detection accuracy may be significantly reduced. There is also a need for technical improvements in depth.

[0007] As described above, the electromagnetic induction method and the underground radar method have some technical problems to be solved. Because it is a temporary measurement at the site and it is essential that transportation and installation are simple, no buried cable exploration method that has reached a practical level has been developed at present.

[0008] The invention of this application has been made in view of the circumstances described above, and the transportation, installation, and operation are simple, and the position of the buried power transmission cable can be detected with high accuracy. It is an object to provide a method for exploring a buried cable.

[0009]

Means for Solving the Problems The present invention solves the above-mentioned problems by measuring a weak AC magnetic field generated by a transmission cable buried underground on a surface of a ground using a magnetic field measuring device. In the buried cable exploration method for calculating the buried position of the power transmission cable from the measured value of the magnetic field, two sensors installed at a certain distance in the vertical direction are arranged horizontally and vertically (two axes) with respect to the power transmission cable. Are measured simultaneously, and based on the measurement results,
A method for exploring a buried cable, which comprises exploring a plane position of a transmission line.

[0010] The method for exploring a buried cable according to the invention of the present application determines the phase arrangement of the power transmission cable based on the measurement results of the two sensors, and uses the database prepared in advance for each power cable phase array to determine the power transmission cable. Calculate the AC magnetic field generated from the transmission cable by theoretical calculation using the current flowing through the transmission cable and the vertical distance from the transmission cable as variables, and calculate the current flowing through the transmission cable and the current from the transmission cable. It is characterized by using a database constructed by storing the values of the alternating magnetic field calculated using the vertical distance as an index in an array.

In the method of searching for a buried cable according to the invention of the present application, a current of a power transmission cable, which is an index of an array constituting the database, is set, and a vertical distance, which is an index of the array, is similarly varied to use the magnetic field measuring apparatus. The vertical distance for the case where the measured magnetic field and the value stored in the array are equal or close to each other is 2
The steps required for each of the two magnetic sensors;
Determine whether the difference between the obtained vertical distances of the two magnetic sensors corresponds to the distance between the magnetic sensors, and if not, return to the first step to set a new cable current. Then, repeat the above steps, and if they match, subtract the height of the magnetic sensor installed below from the vertical distance between the magnetic sensor installed below and the power transmission cable, and embed the value in the power transmission cable. It is determined as the depth. Further, the invention of this application also provides a computer-readable storage medium characterized in that the above-described steps are recorded as a program for causing a computer to function.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The invention of this application has the features as described above, and embodiments thereof will be described below.

In the method of exploring a buried cable according to the invention of the present application, an alternating magnetic field generated by an alternating current flowing through a transmission cable buried underground is measured on a surface of a ground by a magnetic field measuring device, and the measured value of the magnetic field is measured. To determine the burial depth of the transmission cable. The measurement at the ground surface is performed while moving the magnetic field measuring device in a direction crossing the buried transmission cable.

As shown in FIG.
Two magnetic sensors (1) and (2) and a computer (3) for storing the values measured by these magnetic sensors
And a moving mechanism (4) for moving the magnetic field measuring device on the ground surface. Two magnetic sensors (1)
In the positional relationship (2), the horizontal positions are equal, and a constant interval L 'is provided in the height direction. The height of each magnetic sensor from the ground surface is determined by the upper magnetic sensor (1). H0 and the lower magnetic sensor (2) are set to H1.

As the magnetic sensor, an induction voltage sensor such as a coil or a loop antenna is used. Further, the magnetic sensor can simultaneously measure the magnetic flux density in the traveling direction of the magnetic field measuring device and the vertical direction to the ground, or the traveling direction of the magnetic field measuring device, the vertical direction to the ground, and the direction perpendicular to the traveling direction of the magnetic field measuring device. An axis / 3 axis induction voltage sensor is used.

In the method of searching for a buried cable according to the invention of the present application, first, an AC magnetic field generated by a power transmission cable is calculated by a theoretical calculation using a current I flowing through the power transmission cable and a vertical distance L from the power transmission cable as variables. further,
Using the current I flowing through the power transmission cable and the vertical distance L from the power transmission cable as indices, the AC magnetic field calculated by the above-described theoretical calculation is stored in an array B (I, L), and a database is constructed. Since the generated magnetic field differs depending on the phase arrangement of the power transmission cable, this database is prepared for each phase arrangement of the power transmission cable.

In the method of searching for a buried cable according to the invention of this application, two sensors capable of simultaneously measuring the magnetic fields in the horizontal and vertical directions (two axes) with respect to the power transmission cable are fixed in the vertical direction. They will be installed in isolation, and based on the measurement results measured by these sensors, the plane position of the transmission line will be searched.

A procedure for detecting a buried cable in the buried cable exploration method of the present invention will be described with reference to FIGS. 2 and 3. FIG.

As shown in FIG. 2, the x-axis is taken in the traveling direction of the magnetic field measuring device, the y-axis is taken in the horizontal direction of the ground perpendicular to the x-axis, and the z-axis is taken in the vertical direction of the ground. By scanning the magnetic field measuring device along the measurement line, the x-axis direction component V0x and the z-axis direction component V0z of the electromotive force induced by the magnetic sensor installed above, and the magnetic sensor installed below. X-axis components V1x and z of the electromotive force induced at
An axial component V1z is measured at a measurement point on the survey line,
The measured values are input to a computer as digital data and stored in an auxiliary storage device (FIG. 3A).

Based on the measurement results of the two sensors stored in the auxiliary storage device, a determination is made as to the phase arrangement of the power transmission cable. For example, two lines in-phase type and two lines L
As shown in FIGS. 4 and 5, the distribution of the electromotive force in each sensor with respect to the horizontal distance between the power transmission cable and the magnetic field measurement device differs from that of the type. It is possible to determine the phase arrangement (FIG. 3B).

Next, V0 stored in the auxiliary storage device
x, V0z, V1x, V1z are divided by characteristic coefficients depending on the characteristics (number of turns, area, etc.) of the magnetic sensor, and converted into B0x, B0z, B1x, B1z as components of the magnetic flux density at each sensor position in each direction. Is done.
Further, the composite magnetic flux densities B0 and B1 are calculated by the following equation (FIG. 3C).

[0022]

(Equation 1)

[0023]

(Equation 2)

When the magnetic field measuring device is moved in a direction transverse to the buried power transmission cable, the values of B0 and B1 become maximum just above the power transmission cable.

For B0 and B1, which are the maximum, a value close to each is searched for in the magnetic field stored in the database. At this time, first, the current I of the power transmission cable is set (FIG. 3 (D)), and the distance L between the power transmission cable and the magnetic sensor is changed (FIG. 3 (E)). B
From (I, L), a value close to B0 and B1 is searched.
The distance between the power transmission cable and the magnetic sensor corresponding to the values close to B0 and B1 found in the database,
When L0 and L1, respectively,

[0026]

(Equation 3)

If the above holds, the burial depth D of the transmission cable is given by the following equation:

[0028]

(Equation 4)

(FIG. 3F). If equation (III) does not hold, the current value is changed, and the above procedure is repeated.

When searching the database, the arrangement type of the power transmission cable is known in advance.
The search is performed only for the array B (I, L) corresponding to the phase array type of the power transmission cable to be searched.

The above method is recorded on a computer-readable storage medium as a program to be executed by a computer.

In the method of searching for a buried cable according to the invention of the present application, a three-axis induced voltage sensor may be used as described above. In this case, the magnetic flux density in the direction perpendicular to the traveling direction of the magnetic field measuring device is used. In addition, it becomes possible to check the curvature of the power transmission cable in the running direction.

Although the invention of this application has the above-mentioned features, the present invention will be described more specifically with reference to the following examples.

[0034]

[Embodiment 1] A theoretical formula used for constructing a database will be described.

As shown in FIG. 6, H (m) from the measurement point S
It is assumed that a three-phase AC power transmission cable composed of an A phase, a B phase, and a C phase is buried at a distance d (m) at a distance of d. At this time, the currents IA, IB, and IC flowing in the power transmission cables of the respective phases are represented by the following expressions in Phaser display, assuming that the respective phases are tidal currents of the effective value I (A).

[0036]

(Equation 5)

The directional components of the magnetic flux density at the measurement point S using a three-phase power transmission cable as a source are calculated according to Biot-Savart's law.

[0038]

(Equation 6)

[0039]

(Equation 7)

Is represented by The values of the current I and the distance H are changed at fixed intervals, and an iterative operation is performed using the equations (V) to (IX).
By storing the calculated values in (I, H), the database is constructed. However, since these values are complex numbers, the amplitude is stored in the array B (I, H). Example 2 An exploration of a power transmission cable buried from the ground surface was performed using a measuring device as shown in FIG. The measuring device is scanned in a direction perpendicular to the running direction of the power transmission cable, that is, in a direction traversing the power transmission cable, and the voltage induced in the magnetic sensor is measured, and a point where the value is maximum is determined. The value of the magnetic flux density was determined from the maximum value of the induced voltage of the magnetic sensor, the database was searched, and the horizontal position corresponding to the burial depth of the power transmission cable determined according to the above procedure was shown in FIG.

The buried power transmission cable is installed in a pipeline as shown in FIG.
m. Further, the horizontal position is such that the left end is the position of 0.65 m in FIG. 8 and the right end is 1.15 m in FIG.
Corresponding to the position. The result shown in FIG. 8 is obtained by repeating the measurement seven times, and it can be seen that the actual position of the power transmission cable is detected with sufficient accuracy.

[0042]

As described above in detail, according to the invention of this application, a method of exploring a buried cable which can be easily transported, installed, and operated, and which can detect the position of the buried power transmission cable with high accuracy. Provided. The buried cable exploration method of the invention of this application does not require a magnetic field transmission source that has been required in the conventional electromagnetic induction method and underground radar method, and thus realizes a small and lightweight form as a measurement system, The labor of transportation and installation is simplified. Further, since it can cope with a change in the burial depth of the cable, its practical application is expected.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a magnetic field measuring device according to the invention of this application.

FIG. 2 is a schematic diagram showing a positional relationship between a magnetic field measuring device and a power transmission cable.

FIG. 3 is a flowchart showing a method of calculating the burial depth of a power transmission cable in the buried cable exploration method of the present invention.

[Fig. 4] Fig. 4
6 is a graph showing a relationship between an electromotive force induced by a plurality of sensors and a horizontal distance.

FIG. 5 is a graph showing a relationship between an electromotive force induced in two sensors by a magnetic field generated by a two-line L-type transmission line and a horizontal distance.

FIG. 6 is a schematic diagram showing a positional relationship between a three-phase power transmission cable and measurement points in an embodiment of the present invention.

FIG. 7 is a photograph of a magnetic field measuring device used in an example of the present invention.

FIG. 8 shows a horizontal position x of a buried power transmission cable obtained as a detection result in an embodiment of the present invention;
It is the graph which showed the burial depth D corresponding to the horizontal position x.

FIG. 9 is a schematic diagram showing the actual positions of a power transmission cable and a pipeline targeted for exploration in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic sensor 2 Magnetic sensor 3 Computer 4 Moving mechanism 21 Magnetic field measuring device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Kimura Inventor Kansai Electric Power Co., Inc. 3-3-22 Nakanoshima, Kita-ku, Osaka-shi, Osaka (72) Inventor Kazuji Naito 1 Oyodokita, Kita-ku, Osaka-shi, Osaka No. 6-110 Kansai Keiki Kogyo Co., Ltd. (72) Inventor Noboru Toyama 1-6-1110 Oyodokita, Kita-ku, Osaka-shi, Osaka F-term in Kansai Keiki Kogyo Co., Ltd. 2G005 EA03 EA05 EA09 EA09 EA10

Claims (6)

[Claims] 1. A buried cable exploration method for measuring a weak alternating magnetic field generated from a power transmission cable buried underground on a surface of a ground by a magnetic field measuring device and calculating a buried position of the power transmission cable from a measured value of the magnetic field. In the above, two sensors installed in the vertical direction and separated by a fixed distance simultaneously measure each magnetic field in the horizontal and vertical directions (two axes) for the power transmission cable, and based on the measurement results, determine the plane position of the power transmission line. A method for exploring a buried cable, characterized by exploring. 2. A power transmission cable phase arrangement is determined based on measurement results of two sensors, and a power transmission cable depth is calculated using a database created in advance for each power transmission cable phase arrangement. The method for exploring a buried cable according to claim 1, wherein 3. An AC magnetic field generated from the power transmission cable is calculated by theoretical calculation using the current flowing through the power transmission cable and the vertical distance from the power transmission cable as variables, and the current flowing through the power transmission cable and the vertical distance from the power transmission cable are calculated. 3. The method according to claim 2, wherein a database constructed by storing an AC magnetic field value calculated as an index in an array is used. 4. A magnetic field measuring device having two magnetic sensors having the same horizontal position and being spaced apart from each other in the height direction is scanned on the ground in the direction perpendicular to the running direction of the power transmission cable, and is buried. 3. The method according to claim 1, wherein a magnetic field generated from the power transmission cable is measured. 5. An electric current of a power transmission cable, which is an index of an array constituting the database according to claim 3, is set, and similarly, a vertical distance which is an index of the array is varied, and measurement is performed using the magnetic field measuring apparatus of claim 4. Generated magnetic field,
Determining a vertical distance for each of the two magnetic sensors when the values stored in the array are equal to or close to each other; and determining a difference between the determined vertical distances for each of the two magnetic sensors. It is determined whether or not the distance matches the magnetic sensor interval. If the distance does not match, the procedure returns to the first step to newly set the current of the cable, and further repeats the above steps. 3. The buried cable exploration according to claim 2, wherein a value obtained by subtracting the height of the magnetic sensor installed below from the vertical distance between the magnetic sensor installed in the power transmission cable and the power transmission cable is determined as the burial depth of the power transmission cable. Method. 6. A computer-readable storage medium recorded as a program for causing a computer to execute the steps according to claim 5.