JP2001226786A - Constant-potential automatic-control electric corrosion inhibiting system and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the corrosion inhibiting state of plural interfered objects to be inhibited from corrosion at its best. SOLUTION: This constant-potential automatic-control electric corrosion inhibiting system 1 is arranged for plural objects 21 to be inhibited from corrosion and provided with a constant-potential automatic-control electric corrosion inhibitors 3 composed of a constant-potential automatic-control DC power source device 4, a check electrode 32 and a current applying electrode 31 and maintaining the potentials of the objects 21 and a monitor controller 2 for controlling the plural inhibitors 3. When the potentials of the objects are increased beyond the controllability of the inhibitor 3 and deviated from its appropriate corrosion inhibiting potential range, the set potential of the inhibitor 3 for the objects is controlled by the monitor controller 2 to maintain the potential of the object in the appropriate corrosion inhibiting potential range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to seawater machinery for thermal and nuclear power generation, buried piping used for oil transportation, gas and water supply, ground-based storage tanks used for oil and water, and ports The present invention relates to an anticorrosion of a structure, a ship, and the like by a constant potential automatic control system.

[0002]

2. Description of the Related Art For one or a plurality of anticorrosion objects,
When performing electrolytic protection using a plurality of circuits or a plurality of constant-potential automatic control power supplies, the anti-corrosion current supplied from one constant-potential automatic control power supply causes the constant current of another constant-potential automatic control power supply to decrease. When interference is applied to the potential control, the potential near the reference electrode for which the potential control is performed due to the interference may be a noble or noble potential with respect to the case where there is no interference, and may be in an uncontrollable state.

[0003] In this case, in the conventional technique, the potential is set manually so that the set potential of the constant-potential automatic control type power supply device that causes interference is in a range where the anti-corrosion state is not significantly deteriorated and the potential state is within an allowable range of interference. I was adjusting.

[0004]

Problems to be Solved by the Invention <A> The present invention is to maintain the anticorrosion state of an anticorrosion target having a different anticorrosion state depending on a location in an optimum state. <B> Further, the present invention is to maintain the anticorrosion state of a plurality of interference anticorrosion targets in the best state.

[0005]

In order to solve these problems, according to the present invention, there is provided a constant-potential automatic control type cathodic protection device which is likely to interfere with each other or to cause interference. A monitoring control device that collectively manages the potential information of the reference electrode is provided, and this monitoring control device deviates from the proper anticorrosion potential of the interfered anticorrosion target to noble or noble due to mutual interference of each constant potential automatic control type cathodic protection device. And, when the constant potential automatic control function is disabled, the monitoring and control device monitors the potential of the interfered anticorrosion target so as to be within an appropriate potential range, and performs the constant potential automatic control that gives interference. The set potential of the type cathodic protection device is continuously varied by feedback, and cooperative control is performed so that the potential of the interfered anticorrosion target falls within the appropriate corrosion protection range, and the potential is restored.

According to a first aspect of the present invention, there is provided a constant-potential automatic control type cathodic protection system for electrically protecting a plurality of anticorrosion objects, wherein the direct-current power supply, the reference electrode, and the power supply are provided for each anticorrosion object. A constant potential automatic control type cathodic protection device comprising electrodes and controlling to maintain an appropriate potential of the anticorrosion target; and a monitoring control device controlling a plurality of constant potential automatic control type cathodic protection devices. The device maintains the potential of the interfered anticorrosion target within the appropriate anticorrosion potential range when the potential of the interfered anticorrosion target deviates from the appropriate anticorrosion potential range beyond the control capability of the constant potential automatic control type anticorrosion device. In this way, a constant potential automatic control type cathodic protection system is characterized by controlling the set potential of an automatic constant potential control type cathodic protection device for an interference corrosion prevention target.

According to a second aspect of the present invention, there is provided a constant potential automatic control type cathodic protection system according to the first aspect of the present invention, wherein the constant potential automatic control type cathodic protection device for the interference prevention target is weighted, and the potential of the interference prevention target is controlled. Is controlled in a constant potential automatic control type cathodic protection system for interference anticorrosion prevention objects in the order of weighting, when is not maintained within the proper corrosion protection potential range.

According to a third aspect of the present invention, there is provided a constant-potential automatic control type cathodic protection system according to the first aspect, wherein the constant-potential automatic control type cathodic protection device continuously controls the set potential to control the distance between the energized electrode and the anticorrosion target. This is a constant potential automatic control type cathodic protection system characterized by controlling a current flowing through the anticorrosion system.

According to a fourth aspect of the present invention, there is provided a constant potential automatic control type cathodic protection system according to the first aspect, further comprising a remote potential measuring device having a remote reference electrode, disposed in an interference area of the object to be subjected to interference protection. The control device monitors the potential of the remote reference electrode via the communication means, and when the potential of the interfered anticorrosion target deviates from the proper anticorrosion potential range of the constant-potential automatic control type cathodic protection device, the interfering anticorrosion target A constant-potential automatic control type cathodic protection system characterized by controlling a constant-potential automatic control type cathodic protection device for an object to be subjected to interference anticorrosion so as to maintain the electric potential within an appropriate corrosion prevention potential range.

According to a fifth aspect of the present invention, there is provided a constant potential automatic control type cathodic protection device comprising a constant potential automatic control DC power supply device, a plurality of reference electrodes, and a conducting electrode. If the potential of the anticorrosion target deviates from the appropriate anticorrosion potential range even when controlled using electrodes, the potential of the anticorrosion target is controlled by switching the reference electrode from one side to the other and controlling the constant potential automatic control type cathodic protection device. Is controlled so as to be maintained within an appropriate anticorrosion potential range.

A sixth invention comprises a constant potential automatic control DC power supply, a plurality of reference electrodes, and an energizing electrode. The set potential is continuously controlled so as to maintain the potential of the anticorrosion target and the energizing electrode. Equipped with a constant-potential automatic control type cathodic protection system that controls the current flowing between the anticorrosion target objects. Even if the constant-potential automatic control type cathodic protection system continuously controls the set potential using one reference electrode, the anticorrosion target When the potential of the object deviates from the appropriate corrosion protection potential range, the reference electrode is switched from one side to the other, and the set potential of the constant potential automatic control type cathodic protection device is continuously controlled to set the potential of the object to be protected to the appropriate corrosion prevention potential range. A constant potential automatic control type cathodic protection device characterized by being controlled so as to be maintained in the inside.

According to a seventh aspect of the present invention, there is provided a constant potential automatic control type cathodic protection system for cathodic protection of an object to be protected. A plurality of constant-potential automatic control type cathodic protection devices, comprising: a plurality of constant-potential automatic control type anti-corrosion devices, comprising: a set potential to continuously control the set potential so as to maintain the potential of the anticorrosion target; A monitoring control device that controls a plurality of constant-potential automatic control type cathodic protection devices, wherein the monitoring control device is configured such that the potential of the anticorrosion target exceeds the control capability in the corrosion protection range of one of the constant-potential automatic control type cathodic protection devices. If it deviates from the appropriate corrosion prevention potential range, the set potential of the other adjacent constant potential automatic control type cathodic protection device is continuously controlled, and the anticorrosion target is set in one of the constant potential automatic control type cathodic protection devices. And maintains the potential within an appropriate corrosion potential range, a constant potential automatically controlled cathodic protection system.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

<A> Outline of Automatic Electrostatic Protection System with Constant Potential Automatic Control The automatic corrosion control system with automatic constant potential control includes a plurality of automatic corrosion control devices with automatic constant potential control which are likely to interfere or give each other. And a monitoring control device that collectively manages the potential information of the reference electrodes of these constant potential automatic control type anticorrosion devices.

In the monitoring and control device, the appropriate anticorrosion potential of the interfered anticorrosion target deviates to noble or noble due to mutual interference between the constant potential automatic control type cathodic protection devices, and the constant potential automatic control function is disabled. In such a case, the potential of the interfered anticorrosion target is monitored so as to be within an appropriate potential range, and the set potential of the constant-potential automatic control type cathodic protection device that is giving interference is changed by feedback control. Cooperation control is performed so that the potential of the target object falls within the appropriate corrosion protection range, and the object is returned.

<B> Example of the configuration of a constant-potential automatic control type cathodic protection system The constant-potential automatic control type cathodic protection system 1 comprises, as shown in FIGS. It comprises a constant potential automatic control type anticorrosion device 3 including a reference electrode 31 and a reference electrode 32 and the like, and a monitoring control device 2. In addition, as shown in FIG. 3, for example, as shown in FIG. 3, the automatic constant potential automatic control type cathodic protection system 1 includes a monitoring reference electrode 51 for measuring the potential similarly to the reference electrode 32 of the constant potential automatic control type anticorrosion device 3. Is disposed.

The constant potential automatic control DC power supply 4 controls a current source 44 by a control circuit (GCC) 42,
An anticorrosion current I flows between the energized electrode 31 and the anticorrosion target 21. The control circuit (GCCC) 42 compares the potential of the reference electrode 32 with the set potential by the comparator 423 and outputs the result to the gate signal generator 424. The gate signal generator 424 generates a gate signal to be applied to the gate of the thyristor 442 of the current source 44. The set potential E2 is, for example,
1 and a set potential adjuster 422. Set potential adjuster 422
Means that the signal from the monitoring control device 2 is a D / A converter 4
Controlled by the signal converted in step 1, the potential is adjusted. When a plurality of reference electrodes 32 are arranged, the multiplexer (MPX) 43 is switched by a signal from the monitoring control device 2 to select the reference electrode 32. The monitoring and control device 2 includes, for example, a programmable controller that can be controlled by a program.

The monitoring and control device 2 is arranged above the constant-potential automatic control DC power supply 4, and grasps the potential state of the reference electrode 32 of each constant-potential automatic control DC power supply 4. Instructs the device 4 to change the set potential by controlling the set potential adjuster 422, and instructs the switching of the reference electrode 32 when each of the constant potential automatic control DC power supplies 4 uses a plurality of reference electrodes 32. In addition, a potential signal from the remote potential measuring device 5 having the monitoring reference electrode 51 can be received and monitored via the communication means. When the monitoring control device 2 is not provided, the constant-potential automatic control DC power supply device 4 can operate alone.

<C> Operation example of the constant potential automatic control type cathodic protection system In a state where mutual interference of the respective constant potential automatic control type cathodic protection devices 3 is allowed, each of the constant potential automatic control type cathodic protection devices 3 The constant potential control is performed independently by a preset potential set in the automatic potential control type anticorrosion device 3 and a measurement potential of the reference electrode 32 which is normally used.

Any one of the constant-potential automatic control type cathodic protection devices 3 is affected by the influence of the current flowing through the other constant-potential automatic control type cathodic protection device 3, and the potential of the anticorrosion target 21 deviates from the proper anticorrosion potential range. However, in the case where the control cannot be controlled by itself, the potential is monitored by the monitoring control device 2 at all times, and it is determined that the state is abnormal, and the next step is performed.

First step: The reference electrode 32 used for the potential control of the constant potential automatic control type anticorrosion device 3 which is determined to be affected first is changed to another reference electrode 32, Perform the automatic potential control operation and check whether the operation is restored. When the plurality of reference electrodes 32 are provided in this manner, the potential affected by environmental factors such as water flow can be confirmed depending on the location of the anticorrosion target 21, and the anticorrosion target 21 is long, such as a buried pipe. In the case of the object, the potential can be confirmed at a special place such as an intersection of another anticorrosion target, a road crossing, a railroad crossing, and the like, and the accuracy can be improved.

Second step: Next, when a plurality of constant-potential automatic control type cathodic protection devices 3 are installed in one anticorrosion target 21, the built-in program of the programmable controller in the monitoring control device 2. The other constant potential automatic control type cathodic protection devices 3 in the order weighted by
Is continuously changed to a noble or noble potential within a range not deviating from the set potential. The basis for this weighting is
Basically, the order of the ripple effect is large, for example, the order of the output current capacity of the constant potential automatic control DC power supply 4 is large, or, if the output current capacity is the same, the order of the current load is large, or The order of importance is high, such as those that are sensitive to potential, such as titanium and duplex stainless steel.

In the case where a plurality of constant potential automatic control type cathodic protection devices 3 are installed for a plurality of anticorrosion targets 21, there is a possibility of causing interference. In the order weighted in 3, the potential is continuously changed to a noble or low potential within a range that does not deviate from the set potential of the other constant potential automatic control type cathodic protection device 3. The basis of this weighting is basically in the order of large ripple effect, for example, in the order of being easily affected by a small interference current such as a buried pipe with high coating resistance, or when the material is different Or in order of lower corrosion protection potential.

Third step: If the mutual interference falls within the allowable range by this operation, the operation of the constant potential automatic control type cathodic protection device 3 is continued in this state. After a certain period of time, return to the normal position.

Fourth step: If the mutual interference does not fall within the allowable range even if the set potentials of the one constant potential automatic control type cathodic protection device 3 are changed, the monitoring control device 2 further performs In the order weighted by the program of the programmable controller, the potential is successively changed to a noble or noble potential within a range that does not deviate from the set potential of the next-level constant-potential automatic control power supply 4.

Hereinafter, embodiments of the present invention will be described.

<A> First Embodiment of Automatic Electrostatic Protection System with Constant Potential Automatic Control FIG. 3 shows an example in which there are two objects 21 to be protected. One anticorrosion target 21 is the first buried pipe 211, which has a high insulation resistance of the coating and covering, and has strict conditions for controlling the potential for excessive anticorrosion. The other anticorrosion target 21 is the second buried pipe 212, which has a low insulation resistance of the outer coating of the pipe, and has moderate conditions for potential control for excessive anticorrosion.

First buried pipe 211 and second buried pipe 212
Crosses in the middle of the pipeline, and both are equipped with a constant potential automatic control type cathodic protection device to perform cathodic protection. First buried piping 2
The installation position of the eleventh constant potential automatic control type anticorrosion device is separated from the intersection, and a remote potential measuring device 5 that constantly monitors the potential of the intersection is installed at the intersection. The installation position of the constant potential automatic control type cathodic protection device of the second buried pipe 212 is close to the intersection, and the interference of the constant potential automatic control DC cathodic protection equipment of the second physical pipe 212 causes the first buried pipe 211 to interfere. Notably, The first buried pipe 211 and the second buried pipe 212 are not provided with a bond facility for reducing interference. In the case where the influence of the direct potential automatic control of the second buried pipe 212 is remarkable, the monitoring control for controlling the set potential of each other is performed on the constant potential automatic control type cathodic protection apparatus of the first buried pipe 211. The device 2 is installed.

<B> Control Method of First Embodiment of Automatic Electric Control System with Constant Potential Automatic Control The control method of the first embodiment will be described with reference to FIG. FIG. 4 shows pipes at the discharge points (points at which the negative side of the constant potential automatic control DC power supply is connected to the anticorrosion target) with respect to the constant potential automatic control DC power supply 4 of the first embedded pipe 211 and the second embedded pipe 212. Ground potential (P / S: Pipe to Soil Potencia)
l), the passing current, the set potential at the time of the automatic control of the constant potential, and the tube-to-ground potential at a remote point of the first buried pipe 211 at the intersection of the two, showing changes with time.
The remote potential measuring device 5 having the configuration shown in FIG. 3 is installed at a remote point of the first buried pipe 211.

In FIG. 4, the measurement result of the pipe-to-ground potential at the discharge point of the second buried pipe 212 and the first buried pipe 211 are shown.
Since the tube-to-ground potential at the remote point at the intersection of is partially inversely correlated, the second constant potential automatic control DC power supply 402
It is confirmed that interference occurs at the intersection of the first buried pipe 211. As a result, the first buried pipe 211 is an object to be subjected to interference and corrosion prevention, and the second buried pipe 212 is an object to be subjected to interference corrosion prevention.

In the time chart shown in FIG. 4, the pipe-to-ground potential at the discharge point of the first buried pipe 211 is controlled independently by a constant potential automatic control until t1 to maintain the pipe-to-ground potential within the anticorrosion potential. are doing. However, the tube-to-ground potential at a remote point at the intersection of the first buried pipe 211 is such that the current flowing through the constant-potential automatic control DC power supply 402 of the second buried pipe 212 flows in at a remote point of the first buried pipe 211 and crosses. Due to the effect of returning to the second buried pipe 212 at the portion, the potential fluctuates in the noble direction opposite to the pipe-to-ground potential at the discharge point. Therefore, when the control point of the reference electrode 32 is switched from the discharge point to the remote point (time t1), the constant potential automatic control of the first buried pipe 211 is performed because the constant potential automatic control is performed by the tube-to-ground potential at the remote point. The current flowing through the device 401 increases, and the tube-to-ground potential at the remote point becomes an appropriate anticorrosion potential by the effect of the constant potential automatic control. The tube-to-ground potential at the discharge point fluctuates in the negative direction due to the effect of the current flowing through the constant-potential automatic control DC power supply 401, but is maintained within an appropriate corrosion protection range.

At time t2, the pipe-to-ground potential at the discharge point of the first buried pipe 211 became the over-corrosion potential due to a sudden increase in the current flowing through the constant potential automatic control DC power supply 402 of the second buried pipe 212. Therefore, the operation of shifting the set potential of the constant potential automatic control DC power supply 402 of the second buried pipe 212 to a noble potential (time t2) and continuously returning to the set potential in the normal operation state was performed. As a result, the tube-to-ground potential at the discharge point of the first buried pipe 211 returned to the proper corrosion prevention potential range, and the tube-to-ground potential at the remote point also returned to the proper corrosion prevention potential range from the electrolytic corrosion potential.

At time t3, since the discharge potential of the first buried pipe 211 and the pipe-to-ground potential at the remote point have both returned to the proper corrosion protection potential range, the control point of the cathodic protection device of the first buried pipe 211 is changed from the remote point. It returned to the reference electrode installed at the discharge point in the normal operation configuration (time t3).

As described above, when the pipe-to-ground potential at the discharge point and the remote point of the first buried pipe deviates from the appropriate corrosion prevention potential range,
By continuously changing the set potential of the second constant potential automatic control DC power supply in the noble direction, the interference state can be eliminated within an allowable range.

<C> Embodiment 2 of Automatically Controlled Electrostatic Protection System with Constant Potential Automatic Control FIG. FIG. 5 shows a large ground-mounted tank 6 and an insulating joint 63.
The constant potential automatic control DC power supply 4 is applied to both the buried pipe 64 of the fire extinguishing pipe of the tank 6 which is insulated by the tank 6, and the stationary tank 6 has a high height in the annular plate 61 used on the outer periphery of the tank bottom plate. Because of the use of high-strength steel, the anti-corrosion potential is as low as -900 mV. In addition, since the inside of the tank bottom plate 62 is made of ordinary steel and has a large area, the corrosion environment is not constant, Corrosion protection potential -77
It was necessary to perform the control at a potential with a margin for 0 mV. For this reason, the electrolytic protection of the central part of the annular plate part 61 and the tank bottom plate 62 is performed by the constant-potential automatic control DC power supply device 4 of another circuit, and the fire extinguishing pipe of the tank is buried from the middle of the pipe. Therefore, three facilities of the constant potential automatic control DC power supply 4 of the buried pipe 64 are installed close to each other.

From this, although the constant-potential automatic control DC power supply 4 of the three facilities is operated without interference in the normal season, the corrosive environment changes in the rainy season when the amount of precipitation is large. In the anti-corrosion state of the annular plate 61, a potential lower than -900 mV, which is an excessive anti-corrosion potential, was sometimes confirmed, and a constant potential automatic control type cathodic protection device was introduced.

As a result, when the potential of the annular plate 61 has deviated to a lower potential, the current flowing through the constant-potential automatic control DC power supply 4 is 0 (A) even though the current is 0 (A). In order to improve the state of the low potential, the set potential of the constant potential automatic control power supply 4 of the central portion of the tank bottom plate 62 and the buried pipe 64, which is an interference source, is continuously and continuously variable from the monitoring control device 2. By doing so, the over-corrosion prevention state of the high-tensile steel of the annular plate 61 could be improved.

<D> Third Embodiment of Automatically Controlled Electrostatic Protection System with Constant Potential Automatic Control The third embodiment of the electrically controlled anticorrosion system with automatic constant potential control is shown in FIG.
Shown in FIG. 6 shows the large seawater heat exchanger 7 and the ball collector 75 of the shell removal device 73 and the heat exchanger thin tube continuous cleaning device installed in the middle of the seawater pipe connected thereto.
The example which carried out the cathodic protection by the constant potential automatic control power supply device 4 is shown.

In the third embodiment, double-layer stainless steel is used for a part of the components of the shell removal device 73 and the ball collector 75, and the cooling pipe 7 made of a copper alloy is used as the large seawater heat exchanger.
Since it is composed of the inlet water chamber 71 and the outlet water chamber 72 made of 0 and steel, the set potential is operated at -800 mV.
However, in winter when the seawater temperature falls, the appropriate corrosion protection potential of the double-layer stainless steel greatly deviates, and the current supplied to the constant-potential automatic control type cathodic protection device of the inlet water chamber 71 and the outlet water chamber 72 is reduced by the shell removal device 73. Then, by flowing into the ball collector 74, the constant-potential automatic control type cathodic protection device of the shell removing device 73 and the ball collector 74 was stopped, and the over-corrosion protection state was reached.

Therefore, when the shell removal device 73 and the ball collector 75 reach the over-corrosion prevention state, the entrance water chamber 71
And by continuously changing the set potential of the constant potential automatic control type cathodic protection device for the outlet water chamber 72 in the noble direction,
It has become possible to control the potentials of the shell removing device 73 and the ball collector 75 within the appropriate corrosion protection range of the double-layer stainless steel.

[0041]

According to the present invention, the following effects can be obtained. <A> The present invention can maintain the anticorrosion state of an anticorrosion target having a different anticorrosion state depending on a place in the best state. <B> Further, the present invention can maintain the anticorrosion state of a plurality of interference anticorrosion targets in the best state.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a constant potential automatic control type cathodic protection system.

FIG. 2 is an explanatory diagram of a constant potential automatic control DC power supply device.

FIG. 3 is a first embodiment of a constant potential automatic control type cathodic protection system.
Illustration of

FIG. 4 is a diagram showing a potential profile of anticorrosion control of a first buried pipe and a second buried pipe.

FIG. 5 is a second embodiment of a constant potential automatic control type anticorrosion system.
Illustration of

FIG. 6 is a third embodiment of a constant potential automatic control type cathodic protection system.
Illustration of

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Automatic electric potential control system of constant potential automatic control 2 ... Monitoring control device 21 ... Corrosion prevention object 211 ... 1st buried piping 212 / 2nd buried piping 3 ... Automatic electric potential control system of constant electric potential control 31 .. Energizing electrode 32... Reference electrode 4... Constant potential automatic control DC power supply 401. First constant potential automatic control DC power supply 402. Second constant potential automatic control DC power supply 41... D / A converter 42. ..Control circuit 421 reference power supply 422 set potential regulator 423 comparator 424 gate signal generator 43 multiplexer 44 current source 441 transformer thyristor 5 remote potential measuring device 51 Monitoring reference electrode 6 ・ ・ ・ Tank 61 ・ ・ Annular plate 62 ・ ・ Tank bottom plate 63 ・ ・ Insulation joint 64 ・ ・ Buried piping 64 for fire extinguishing piping 7 ・ ・ ・ Large seawater Heat exchanger 70, cooling pipe 71, inlet water chamber 72, outlet water chamber 73, shell removal device 74, circulating water pipe 75, ball collector

Claims (7)

[Claims] In a constant potential automatic control type cathodic protection system for electrically protecting a plurality of anticorrosion targets, the system is disposed for each anticorrosion target, and comprises a constant potential automatic control DC power supply device, a reference electrode, and a conducting electrode. A constant-potential automatic control type cathodic protection device that controls so as to maintain an appropriate potential of the anticorrosion target; and a monitoring control device that controls a plurality of constant-potential automatic control type cathodic protection devices. If the potential of the interference protection target exceeds the controllability of the constant potential automatic control type cathodic protection device and deviates from the proper corrosion prevention potential range, interference protection is performed so that the potential of the interference prevention target is maintained within the proper corrosion prevention potential range. A constant potential automatic control type cathodic protection system characterized by controlling a set potential of a constant potential automatic control type cathodic protection device for an object. 2. The constant-potential automatic control type cathodic protection system according to claim 1, wherein the constant-potential automatic control type cathodic protection device of the interference anticorrosion target is weighted, and the potential of the interference prevention target is properly anticorrosion. A constant potential automatic control type cathodic protection system characterized by controlling a constant potential automatic control type cathodic protection device for interference prevention objects in the order of weighting when the potential cannot be maintained within the potential range. 3. The constant-potential automatic control type cathodic protection system according to claim 1, wherein the constant-potential automatic control type cathodic protection device continuously controls a set potential to flow between a current-carrying electrode and an object to be protected. A constant potential automatic control type cathodic protection system characterized by controlling 4. The constant-potential automatic control type cathodic protection system according to claim 1, further comprising a remote reference electrode, a remote-potential measuring device disposed in an interference area of the target object, and a monitoring control device. When the potential of the remote reference electrode is monitored via the communication means, and the potential of the interfered anticorrosion target deviates from the proper anticorrosion potential range of the constant potential automatic control type cathodic protection device,
A constant potential automatic control type cathodic protection system characterized by controlling a constant potential automatic control type cathodic protection device of the interference prevention target object so as to maintain the potential of the interfered anticorrosion target within an appropriate corrosion prevention potential range. 5. The constant potential automatic control type cathodic protection system according to claim 1, wherein the constant potential automatic control type cathodic protection device comprises a constant potential automatic control DC power supply device, a plurality of reference electrodes, and an energizing electrode. If the potential of the anticorrosion target deviates from the appropriate corrosion prevention potential range even if the constant potential automatic control type cathodic protection device controls using one reference electrode, the reference electrode is switched from one to the other and the constant potential automatic control type is used. A constant potential automatic control type cathodic protection system, characterized by controlling the cathodic protection device so as to maintain the potential of the anticorrosion target within an appropriate anticorrosion potential range. 6. A constant-potential automatic control DC power supply, a plurality of reference electrodes, and a current-carrying electrode, wherein the set potential is continuously controlled so as to maintain the potential of the object to be protected. A constant-potential automatic control type cathodic protection device controls the current flowing through the anti-corrosion target even if the constant-potential automatic control type cathodic protection device continuously controls the set potential using one reference electrode. When the potential deviates from the appropriate corrosion protection potential range, the reference electrode is switched from one to the other to continuously control the set potential of the constant potential automatic control type cathodic protection device to maintain the potential of the object to be protected within the appropriate corrosion protection potential range. Constant-potential automatic control type cathodic protection device, characterized in that it is controlled in the following manner. 7. A constant potential automatic control type anticorrosion system for electrically protecting an object to be corroded, comprising: a constant potential automatic control DC power supply; a plurality of reference electrodes; A plurality of constant potential automatic control type cathodic protection devices for continuously controlling a set potential so as to maintain a potential of the anticorrosion target and controlling a current flowing between the current-carrying electrode and the anticorrosion target; A monitoring control device that controls the automatic potential control type anticorrosion device, wherein the monitoring control device has a proper anticorrosion potential when the potential of the object to be protected exceeds the control capability in the anticorrosion range of one of the constant potential automatic control type anticorrosion devices. If it deviates from the range, the set potential of the other adjacent constant potential automatic control type cathodic protection device is continuously controlled, and the potential of the object to be protected in the corrosion prevention range of one constant potential automatic control type cathodic protection device is adjusted appropriately. A constant potential automatic control type cathodic protection system, characterized in that the potential is maintained within the range of the positive corrosion prevention potential.