JPH1164266A - Apparatus for detecting position and level of damage of coated buried metallic conductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always monitor occurrence of a damage to a coating of a buried metallic conductor and quantitatively judge a position and a degree of the damage. SOLUTION: A position and a degree of a damage of a buried metallic conductor (steel pipe) 2 to be monitored are immediately detected by a conduction point 3 set at one point of the coated buried metallic conductor, a conduction electrode 5 buried in the vicinity of the buried metallic conductor 2, a conduction power source apparatus 12 sending a.c. signals between the conduction point 3 and the conduction electrode 5, a potential measuring apparatus 13 measuring an amplitude and a phase of a signal frequency component of a potential between the buried metallic conductor 2 and a reference electrode 8 buried in the vicinity of the conductor, a current measuring apparatus 14 measuring an amplitude and a phase of a signal frequency component of a current running in a conductor in a monitor direction of the buried metallic conductor 2, an analyzing apparatus 15 detecting the position and degree of the damage in the monitoring direction, and an informing apparatus 16 informing a predetermined manager of a detected result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for constantly monitoring the occurrence of coating and coating damage on coated metal conductors buried in soil or the like.

[0002]

2. Description of the Related Art As a conventional method for monitoring the occurrence of paint coating damage on a buried metal conductor, there is a method in which an administrator patrols a place where the metal conductor is buried from a road. Further, as a method of constantly monitoring the occurrence of coating and coating damage on a buried metal conductor having a long extension, there is a method described in Japanese Patent Application No. 5-274286. This allows a constant signal current to flow through the buried metal conductor to be monitored, damage can be detected from changes in the potential and current distribution measured at appropriately spaced points of the buried metal conductor, and furthermore, It is possible to determine which of the points has been damaged.

[0003] There is also a method described in JP-A-2-203263. This means that by applying an AC signal to the buried metal object to be monitored and monitoring the AC impedance at the current-carrying point, in the event of damage, the absolute value of the AC impedance decreases and damage can be detected. is there. Furthermore, the damage position can be specified by moving the monitoring device of the AC impedance. The method described in Japanese Patent Application Laid-Open No. 8-304321 measures the characteristic impedance and the propagation constant of the buried metal conductor to be monitored in advance, and determines the damage position and the degree of damage from the values and the potential or current at the energized point. Can be determined.

[0004]

The steel surface of the metal conductor buried in the soil is insulated from the soil by coating and coating, thereby preventing the progress of corrosion. But other buried objects,
If the coating is damaged due to contact with stones in the soil, heavy construction equipment, or natural deterioration, the steel surface of the buried metal conductor comes into contact with the soil and may be corroded. Further, when the degree of damage is so severe that the metal conductor is damaged, a serious accident such as leakage of internal fluid due to breakage of the metal conductor or the like is caused. Therefore, it is extremely important for security to constantly monitor the coating of the buried metal conductor for damage.

In the case where the length of the buried metal conductor is long, when the damage is detected, the position of the damage is specified in detail,
It is important to be able to take appropriate action immediately, such as restoration. The method of patroling a place where a metal conductor is buried from a road has a problem that contact with other buried objects and stones in soil cannot be detected. In addition, there is a problem that it is difficult to constantly monitor even during a time period such as nighttime, and costs for personnel maintenance and patrol facilities are required.

[0006] In a conventional method of maintaining and managing the distribution of potentials and currents measured at a plurality of points, it is possible to determine which of the points has suffered damage. There was a problem that can not be.
Further, the method of detecting damage from a decrease in the absolute value of the AC impedance at the energized point as disclosed in Japanese Patent Application Laid-Open No. 2-203263 has a problem that the position of the damage cannot be specified.

Further, in the method of specifying the damage position by moving the damage detection sensor along the pipeline, it takes time and cost for the buried metal conductor having a long extension, and the purpose of constant monitoring cannot be achieved. There was a problem that. In the method of measuring the characteristic impedance and propagation constant of a buried metal conductor in advance as disclosed in Japanese Patent Application Laid-Open No. 8-304321, a technique that requires skill is required to accurately measure these values for a buried metal conductor having a long extension. There was a problem that it was necessary.

In addition, when the buried metal conductor to be monitored is very long and the impedance per unit length is high, or when the state of the coating is not very good, signal attenuation or deterioration becomes remarkable. For this reason, there has been a problem that the accuracy of determining the damage position and the degree of damage is reduced, and the range that can be monitored is limited. The buried metal conductor is
In addition to applying a coating, there is a case where corrosion is prevented by an electrolytic protection method called an external power supply method in which a direct current is supplied from a direct current power supply. If a signal for damage monitoring is superimposed on this direct current and energized from the same power supply, the management work for the already established cathodic protection and the damage monitoring management work must be performed simultaneously, which complicates the management work. There were challenges. Also, it is rare that the optimal energization point of the anticorrosion DC and the optimal energization point of the damage monitoring signal coincide, and it is not possible to energize the anticorrosion DC and the damage monitoring signal from the same energization point. There was a problem of efficiency.

Accordingly, an object of the present invention is to constantly monitor the occurrence of coating and coating damage on a buried metal conductor without requiring any skill while keeping costs down. It is another object of the present invention to quantitatively determine a damage position and a degree of damage when damage is detected. It is another object of the present invention to cover the entire monitoring target range even when the length of the buried metal conductor to be monitored is very long, and to accurately determine the damage position and the degree of damage. Furthermore, even when the buried metal conductor to be monitored is subjected to cathodic protection, an object of the present invention is to efficiently monitor damage without complicating management work.

[0010]

According to the present invention, there is provided a damage monitoring apparatus comprising: a current-carrying point provided at one point of a coated and covered buried metal conductor to be monitored; and a through-electrode buried near the buried metal conductor. A power supply device for supplying an AC signal between the conduction point and the conduction electrode; and a potential for measuring the amplitude and phase of a signal frequency component of a potential between the buried metal conductor and a reference electrode buried in the vicinity thereof. A measuring device, a current measuring device for measuring an amplitude and a phase of a signal frequency component of a current flowing through the conductor in a monitoring target direction of the buried metal conductor, and a signal in a monitoring target direction of the buried metal conductor from the measured potential and current. By calculating the impedance with respect to the frequency and referencing the coordinates of the calculated impedance on the Gaussian plane to a preset map of the coordinates of the impedance at the time of damage, An analysis device for determining the degree of damage location and damage in a subject view direction, and means that it is composed of a notifying device to notify the determination result to a predetermined administrator.

Further, according to the present invention, when the damage position changes from the position closest to the energized point to the position farthest from the energized point within the monitoring target range, the coordinates of the impedance at the time of damage on the Gaussian plane are around the coordinates of the healthy state. The rotation angle is 360
The means is to grasp in advance the range of frequencies that are less than ° and select the frequency of the AC signal to be energized from within this range. Also, the present invention selects a plurality of frequencies as signal frequencies from the applicable frequency range,
These are superimposed and energized to determine the damage position from the impedance coordinates for the high frequency signal, and determine the damage degree from the impedance coordinates for the low frequency signal.

Further, according to the present invention, the buried metal conductor to be monitored is divided into several monitoring target ranges, one point in each of the divided ranges is set as an energizing point, and signals from energizing points in other divided ranges are supplied. A signal of a frequency different from the above is simultaneously supplied from each conduction point, and at each conduction point, the impedance in the monitoring target direction for each frequency is calculated, and the damage is monitored. Further, the present invention is to provide one or a plurality of measurement points at a point different from the energization point, calculate impedance at the energization point and each measurement point, and monitor damage.

The present invention also provides a method for connecting a power supply for damage monitoring in parallel with the anticorrosion DC power supply when the buried metal conductor to be monitored is electrically protected by the anticorrosion DC power supply. By simultaneously energizing the AC signal and the anti-corrosion direct current from the same energizing point, damage monitoring and cathodic protection are simultaneously performed. Also, the present invention provides damage monitoring and cathodic protection by energizing DC and AC from the respective optimal energizing points when the optimal energizing point of the anticorrosion DC and the optimal energizing point of the damage monitoring AC signal are different. Are performed simultaneously.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors conducted an experiment to measure a change in impedance at an energized point when simulated damage was applied to a coated steel pipe buried in soil, and obtained the following new findings. Obtained. The impedance depends on the location of the damage and the degree of the damage.
Can be plotted at one point on the Gaussian plane as shown in FIG. The position of the damage can be determined on the Gaussian plane by an angle θ formed by a line connecting the coordinates at the time of soundness and the coordinates at the time of damage as shown in FIG. 1 with an arbitrarily determined reference line. On the Gaussian plane, the degree of damage can be determined from the displacement between the coordinates when sound and the coordinates when damaged, as shown in FIG. When the frequency of the monitoring signal is changed, the angle formed by the arbitrarily determined reference line between the coordinate at the time of damage and the coordinate at the time of sound has a positive correlation as shown in FIG.

The present invention has been made based on the above new findings. The present invention is an apparatus that detects occurrence of damage from a change in impedance of a steel pipe on a Gaussian plane, and clarifies a position and a degree of damage.

The basic configuration of the device required for implementing the present invention will be described with reference to FIG. FIG. 3 shows a coated steel pipe 2 buried in soil with a point 1 as a pipe end, and devices installed at a point 0 for implementing the present invention. Point 0
In FIG. 1, one point of the coated steel pipe 2 is referred to as an energizing point 3, the right direction in the figure is a monitored direction A, and the left direction is a monitored direction B. The monitoring target range in the monitoring target direction A is from point 0 to point 1.

At a point 0, in order to apply an AC signal, the conducting lead 4 attached to the conducting point 3 and the conducting lead 6 attached to the conducting electrode 5 installed near the ground stand on the ground surface. Raising. A potential measuring lead wire 7 attached to one point near the conducting point 3 for measuring potential;
A reference electrode lead wire 9 attached to a reference electrode 8 installed in the vicinity is raised on the ground surface. Here, the potential measurement lead wire 7 may be attached to the conduction point 3.

In order to measure the current flowing through the pipe in each of the monitoring target directions A and B, a CT (current transformer) 10 is attached to one point in each monitoring target direction, and a current measuring lead wire 11 is connected to the ground surface. Has been launched. The current flowing in the buried metal conductor in the monitoring target direction can also be measured by a tube-to-tube potential difference method.

The energizing lead wire 4 and the conducting electrode lead wire 6 are connected to an energizing power supply device 12. The potential measuring lead 7 and the reference electrode lead 9 are connected to a potential measuring synchronous detector 13. The current measuring lead wire 11 is connected to a current measuring synchronous detector 14.

Here, from the relationship between the frequency and the rotation angle shown in FIG. 2, the frequency at which the angle between the coordinate of the damage at the farthest point of the monitoring range and the reference line is 360 degrees can be obtained.
This is the highest frequency that can be applied in the actual machine. And by applying a lower frequency as the signal frequency,
In the actual monitoring result, the coordinates indicating the damage at the farthest point and the damage at the closest point are not plotted so as to overlap the same point on the Gaussian plane, and it is possible to accurately determine the damage position.

A frequency within an applicable range is supplied as a monitoring signal from the power supply 12 for monitoring, and a synchronous detector for measuring a potential or a current is used to detect a potential E and currents iA and iA.
| E | and | iA |, | i of the signal frequency component of B
B | and the phase differences θ _E and θiA, θiB. The AC signal is energized by inputting a signal oscillated from the internal oscillator of the potential measuring synchronous detection device 13 to the energizing power supply device 12. The phase is measured using the oscillation signal as a reference signal. Here, the signal may be oscillated by preparing the current measuring synchronous detector 14 or another oscillator.

Further, as a potential of the buried metal conductor to be monitored, a voltage between the conduction point 3 and the conduction electrode 5, that is, a conduction voltage may be substituted. At this time, energization may be performed by constant voltage control to keep the potential constant. In addition, when the energizing point 3 is at the tube end, the energizing current flows all in one direction. In this case, the current flowing through the buried metal conductor in the monitoring target direction is defined as the current flowing between the energizing point 3 and the through electrode 5. , The current flowing therethrough may be used instead. At this time, energization may be performed by constant current control to keep the current constant.

| E |, θ _E , | iA |, θi
The values of A, | iB | and θiB are taken into the impedance analyzer 15, and the impedance is calculated.
The impedance ZA in the monitoring target direction A and the impedance ZB in the monitoring target direction B are expressed by Expressions 1 and 2, respectively. Here, j ² = −1.

[0024]

## EQU1 ## ZA = E / iA = (| E | / | iA |)
expj (θE-θiA)

[0025]

## EQU2 ## ZB = E / iB = (| E | / | iB |)
expj (θE-θiB)

When the coated steel pipe to be monitored is damaged, the coordinates of the impedance at that time are referred to the impedance map at the time of damage prepared in advance by the same measurement as that shown in FIG. It is possible to quantitatively determine the location and degree of damage. Further, if a similar map is created for the impedance ZB, the damage position and the damage degree in the monitoring target direction B can be quantitatively determined.

The impedance analyzer 15 constantly monitors the impedances ZA and ZB to be monitored. Damage in the direction A to be monitored is caused by a change in the coordinates of ZA.
Damage in the monitoring target direction B is detected by a change in the coordinates of ZB. When damage is detected in any of the monitoring target directions, it is compared with a preset map of impedance coordinates at the time of damage to determine the damage position and damage degree in each monitoring target direction. Do. When the impedance analysis device 15 detects the damage, the notification device 16 issues an alarm to a predetermined manager via the telephone line 17 and simultaneously notifies the judgment result of the damage position and the damage degree. Here, besides the telephone line,
Wireless or the like may be used.

In order to improve the accuracy of damage detection, a plurality of frequencies may be superimposed and used as a monitoring signal. However, each of the signal frequencies is selected from within the applicable frequency range. In this case, if a combination of a high frequency with a high accuracy in determining the damage position and a low frequency with a high accuracy in the determination of the degree of damage is used, the accuracy of determination of both the damage position and the degree of damage is improved.

When the entire monitoring target cannot be covered by one monitoring device, the buried steel pipe to be monitored is divided into several monitoring target ranges according to claim 4 of the present invention.
A monitoring device may be installed for each of the divided areas to cover the entire area to be monitored. At this time, if different signal frequencies are used for the respective monitoring devices, interference of the monitoring signals is eliminated and a good monitoring state is achieved. Further, in order to improve the detection accuracy, a plurality of measurement points may be provided in the monitoring target area according to claim 5 of the present invention, and the impedance may be calculated at the energization points and at each measurement point to monitor the occurrence of damage.

In the case where an anticorrosion DC power supply is already installed on the buried metal conductor to be monitored, a power supply device for damage monitoring is connected in parallel with the anticorrosion DC power supply according to claim 6 to monitor the damage. The occurrence of damage can be monitored by energizing the AC signal for protection and the DC for corrosion protection simultaneously from the same conduction point. Furthermore, if the optimal energization point of the anticorrosion DC and the optimal energization point of the damage monitoring AC signal do not match, according to claim 7, the anticorrosion DC and the damage monitoring AC signal are output from different energization points. All you have to do is energize.

[0031]

Embodiment 1 According to the present invention, a caliber 3 buried in soil
A result of monitoring the occurrence of coating damage on a coated steel pipe having a length of 00 mm and a total length of 28.3 km will be described. The monitoring device is as shown in FIG. 3, and its detailed contents are as described above. FIG. 4 shows an outline of a coated steel pipe to be monitored, and a monitoring device is installed at a point 0 in the figure. The monitoring target directions are two directions on both sides in the A direction and the B direction from the energization point. The monitoring target range is from the energization point to the pipe end in each direction, and the distances of the respective ranges are A: 14.2 km and B: 14.1 km.

In order to grasp the applicable frequency range in the monitoring target range A, the rotation angle of the impedance coordinate when the damage position was changed from the energized point to the tube end was measured. The results of measurement at four frequencies of 15, 220, 420, and 820 Hz are indicated by circles in FIG. The rotation angle increased linearly with the frequency, and was expected to rotate 360 degrees at 440 Hz, as indicated by x in the figure. Therefore, for the monitoring target range A, a frequency lower than 440 Hz is an applicable frequency range. In this embodiment, the signal frequency is set to 220 Hz.

FIG. 6 shows the coordinates of the impedance when a damage of a degree of 30Ω is simulated at a position 4.2 km from the energization point in the monitoring target range A on a map set in advance. This is plotted with. From the impedance map, the damage position is about 4.2k from the energized point.
m, the degree of damage was determined to be about 30Ω, which was in good agreement with the actual value, and it was confirmed that the damage position and the degree of damage can be correctly and quantitatively determined by the apparatus of the present invention.

[0034]

Second Embodiment In the monitoring target range A shown in FIG. 4, the displacement amount of the impedance coordinate when the damage occurs from the normal state is as shown in FIG. Since the lower the frequency, the larger the displacement amount from the normal state, the lower frequency is more advantageous for determining the degree of damage. In addition, as shown in FIG. 5, the higher the frequency, the larger the rotation angle. Therefore, the higher frequency is more advantageous for determining the damage position. FIG. 8 shows an embodiment in which 15 Hz is selected as the low frequency and 420 Hz is selected as the high frequency, and these are superimposed and energized to determine the damage position and the degree of damage. At this time, a frequency signal is input to the power supply device 12 via the signal superposition circuit 20.

[0035]

Embodiment 3 FIG. 9 shows an embodiment in which a buried metal conductor to be monitored is divided into several ranges to be monitored and the occurrence of damage is monitored by a monitoring device installed at each energization point.
At this time, a signal of a different frequency is supplied from each power supply power supply device 12, and a filter that allows only the signal frequency to pass therethrough so as not to adversely affect damage monitoring of other monitoring target ranges. Connect to metal conductor.
The signal frequencies are all selected from the range specified above. Further, as described above, it is also possible to improve the accuracy of damage monitoring by supplying a plurality of frequency signals at each conduction point. Further, the monitoring target ranges do not necessarily have to be completely independent, and there may be overlapping portions.

[0036]

Embodiment 4 FIG. 10 shows an embodiment in which one or a plurality of points other than the energization point are set as measurement points. At the two measurement points in the figure, the same damage monitoring device as the energization point is installed. Here, each signal frequency is selected from the range specified above. As described above, a plurality of frequency signals may be applied at each energization point. Further, the monitoring target ranges do not necessarily have to be completely independent, and there may be overlapping portions. Also, a plurality of measurement points may be provided for a plurality of energization points.

[0037]

Fifth Embodiment FIG. 11 shows an embodiment in which the anticorrosion DC power supply 23 is already installed on the buried metal conductor to be monitored and the control work of the cathodic protection is established. Power supply device 12 for monitoring the damage in parallel with DC power supply 23 for corrosion protection
Are connected, and a DC for corrosion prevention and an AC signal for damage monitoring are simultaneously energized to perform damage monitoring. in this case,
(A) The AC signal is energized by constant current control. (B) The two power supplies are connected to the low-pass filter 21 by the anticorrosion DC power supply 23 so that they do not load each other.
The damage monitoring power supply devices 12 are connected via a high-pass filter or a band-pass filter 22, for example, so as not to adversely affect each other.

[0038]

Embodiment 6 FIG. 12 shows an embodiment in which the anticorrosion DC signal and the damage monitoring AC signal are supplied from the respective optimal conduction points.
Shown in As shown in FIG.
Therefore, the signals for damage monitoring are energized from the energizing point 3 respectively. In this case, (a) the AC signal is supplied with constant current control, (b) the anticorrosion DC power supply 23 is provided with a low-pass filter 21, and the damage monitoring power supply device 12 is provided with a high-pass filter or band-pass filter 22. Take measures to prevent adverse effects such as connecting to each other.

[0039]

The present invention can be implemented only by installing the device at the current-carrying point, and there is no need to move the device, so that cost and labor are not required. When the damage is detected by the change in impedance, the damage position and the degree of damage can be quantitatively determined by referring to a preset impedance map at the time of damage without requiring skill. Further, by providing a plurality of energization points or measurement points according to the present invention, the application of the damage monitoring technique according to the present invention is not limited by the extension distance or the like, and the determination accuracy does not decrease. In addition, since monitoring is performed at a plurality of points, the reliability of determination is improved.

Simultaneously, the cathodic protection and the damage monitoring can be performed very easily by taking measures such as inserting a filter so as not to adversely affect each other.
If the damage monitoring AC power supply is connected in parallel to the anticorrosion DC power supply and energized, damage monitoring and cathodic protection management can be performed separately, so change the already established cathodic protection management work. There is no need, and the management of damage monitoring is easier. If the power supply for anticorrosion is broken by a parallel connection, the power supply for energization for damage monitoring can be used as a backup. When energizing anticorrosion DC and damage monitoring AC from different points,
The point at which the mutual efficiency is highest can be selected as the energizing point.

Further, when damage is detected, the location of the damage is reported to a predetermined manager, so that appropriate measures such as repair can be quickly taken.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a change in impedance of a coated steel pipe on a Gaussian plane.

FIG. 2 is an explanatory diagram showing a relationship between a frequency and a rotation angle.

FIG. 3 is an explanatory diagram of a basic configuration of an apparatus for implementing the present invention.

FIG. 4 is an explanatory diagram of an outline of a coated steel pipe to be monitored.

FIG. 5 is an explanatory diagram of a rotation angle of impedance at each frequency.

FIG. 6 is an explanatory diagram of a monitoring result of impedance.

FIG. 7 is an explanatory diagram of a relationship between a frequency and an amount of displacement.

FIG. 8 is an explanatory diagram of an embodiment of damage monitoring using a plurality of frequencies.

FIG. 9 is an explanatory diagram of an embodiment in the case where damage is monitored at a plurality of energized points.

FIG. 10 is an explanatory diagram of an embodiment in the case where damage is monitored at a plurality of measurement points.

FIG. 11 is an explanatory diagram of an embodiment in which an AC power supply for damage monitoring is connected in parallel to a DC power supply for corrosion protection.

FIG. 12 is an explanatory diagram of an embodiment in a case where an AC power supply for damage monitoring is connected to a different conduction point from a DC power supply for anticorrosion.

[Explanation of symbols]

 2 coated steel pipe 3 energized point 4 energized lead wire 5 through electrode 6 through electrode lead wire 7 potential measurement lead 8 reference electrode 9 reference electrode lead 10 CT 11 current measurement lead 12 current supply power supply 13 Synchronous detector for potential measurement (frequency f1) 14 Synchronous detector for current measurement (frequency f1) 15 Impedance analyzer 16 Notification device 17 Telephone line 18 Synchronous detector for potential measurement (frequency f2) 19 Synchronous detector for current measurement (Frequency f2) 20 signal superposition circuit 21 low-pass filter 22 high-pass filter or band-pass filter 23 anti-corrosion DC power supply 24 anti-corrosion DC current point 25 anti-corrosion lead 26 anti-corrosion through electrode 27 anti-corrosion through electrode lead

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Ohira 2-6-1, Otemachi, Chiyoda-ku, Tokyo Inside Nippon Steel Corporation (72) Inventor Nobuhiro Sasaki 2-6-, Otemachi, Chiyoda-ku, Tokyo No. 3 Inside Nippon Steel Corporation

Claims (7)

[Claims] 1. An apparatus for constantly monitoring the occurrence of coating damage on a coated buried metal conductor, comprising: an energization point provided at one point of the coated buried metal conductor to be monitored; A through electrode buried in the vicinity of the buried metal conductor, an energizing power supply for supplying an alternating current signal between the conducting point and the through electrode, and a potential between the buried metal conductor and a reference electrode buried in the vicinity thereof. A potential measuring device for measuring the amplitude and phase of the signal frequency component, a current measuring device for measuring the amplitude and phase of the signal frequency component of the current flowing through the conductor in the monitoring target direction of the buried metal conductor, and the measured potential and The impedance of the buried metal conductor with respect to the signal frequency in the monitoring target direction is calculated from the current, and the coordinates of the calculated impedance on the Gaussian plane are mapped to the coordinates of the impedance coordinates at the time of damage set in advance. An analysis device for determining the damage position and the degree of damage in the monitoring target direction by referring to the monitoring information, and a notification device for notifying a predetermined manager of the determination result. A device for determining the location and degree of damage to a covered buried metal conductor. 2. The angle at which the coordinates of the impedance at the time of damage are rotated around the coordinates at the time of soundness on the Gaussian plane when the damage position changes from a position closest to the energized point in the monitoring target range to a position farthest from the point. The apparatus for determining a damage position and a degree of damage of a coated and buried buried metal conductor according to claim 1, wherein a frequency that is less than 360 ° is selected as a signal frequency. 3. A plurality of signal frequencies within a range specified in claim 2 are selected, superimposed and energized on a coated and covered buried metal conductor to be monitored, and a current in a direction to be monitored for each frequency is selected. The apparatus for judging a damage position and a damage degree of a coated and covered buried metal conductor according to claim 1, wherein the impedance is monitored. 4. A coated and covered buried metal conductor to be monitored is divided into several ranges to be monitored, and one point in each of the divided ranges is set as an energizing point, and the energizing points in the other divided ranges are set as the energizing points. One or a plurality of frequency signals having a frequency different from the signal frequency and within the range specified in claim 2 are superimposed and energized from each energizing point, and the monitoring target direction for each frequency is measured at each energizing point. The apparatus for judging a damage position and a damage degree of a coated and covered buried metal conductor according to claim 1, wherein the impedance is monitored. 5. The potential measuring device, the current measuring device, the analyzing device, and the notifying device are installed at one or a plurality of points other than an energized point, and impedance of the signal frequency at each point and the energized point is set. The apparatus for determining a damage position and a degree of damage of a coated and covered buried metal conductor according to claim 1, wherein the calculation is performed. 6. The power supply device for energization is connected in parallel to a direct current power supply for anticorrosion, and an alternating current signal for damage monitoring and a direct current for anticorrosion are supplied from the same current supply point. An apparatus for determining a damage position and a degree of damage of a buried metal conductor coated and covered according to claim 1. 7. The power supply device for energization and the DC power supply for anticorrosion are respectively connected to different energization points, and an AC signal for damage monitoring and a DC for anticorrosion are energized from different energization points. The apparatus for determining a damage position and a degree of damage of a coated and buried metal conductor according to claim 1.